All posts by Marko P.

Nakajima Ki-115 Tsurugi

Empire of Japan, WW2, , , , , , ,

 Empire of Japan (1945)
Kamikaze Aircraft – 105 Built

The Ki-115 suicide aircraft [Combat Workshop via Pinterest]

Throughout 1945, it was becoming clear to Japanese Army Officials that an Allied invasion of the Japanese mainland was growing ever more likely. Seeing as their navy and airforce had been mostly destroyed, they needed new weapons to fight off a probable Allied attack on Japan. Among these new weapons were Kamikaze aircraft, with many older designs having already been used in this role. However, some Kamikaze aircraft were to be specially designed for such a role, being cheap and able to be built quickly and in great numbers. One such aircraft was the Ki-115 Tsurugi (Sabre) which was built in small numbers, and never used operationally.

History

Rear view of Ki-115 suicide aircraft [ijaafphotos.com]
Following the extensive loss of men, materiel, and territory during the fighting in the Pacific, the Japanese Army and Navy were in a precarious situation, especially as there was a great possibility of an Allied invasion of their homeland. Unfortunately for them, the Japanese fighting forces on the ground, in the air, and on the sea were mostly mere shadows of their former selves, unable to prevent the rapid Allied advance across the Pacific. This was especially noticeable after the costly Japanese naval defeat during the Battle of Leyte Gulf in October 1944 and later Battle of Okinawa which ended in July 1945.. The desperation, or better said fanatical refusal to accept that the war was lost, led to the development and use of Kamikaze (divine wind) tactics. This name was taken from Japanese history, the term arose from the two typhoons that completely destroyed the Mongol invasion fleets.

Essentially, the Kamikaze were Japanese pilots that used their own explosive-laden aircraft as weapons, and sought to crash into important targets, such as Allied warships. This term also entered widespread use to designate all Japanese suicide craft used in this way. During the war, these tactics managed to sink over 30 Allied ships and damage many more.

Allied anti-aircraft fire was often concentrated in order to prevent Kamikaze attacks. But, despite this, Japanese aircraft would often get through. [Wiki]
The suicide attacks were mostly carried out using any existing aircraft that was operational, including older trainers and obsolete aircraft. Kamikaze are a subject with a great deal of nuance and can be difficult to understand through a conventional lens. However, supplies of these aircraft would inevitably become limited and their previous usage meant fewer would be serviceable compared to newer, more expensive models. Thus, the Japanese Army wanted a specially designed Kamikaze aircraft that could be produced in great numbers. These aircraft needed to have a simple construction and use as little of dwindling material stockpiles as possible.

On 20th January 1945, the Japanese Army contacted the Nakajima aircraft manufacturer with instructions to design and build such an aircraft. The basic requirements included a bomb load up to 800 kg (1,760 lbs). It had to be able to be powered by any available radial engine in the range of 800 hp to 1,300 hp. The maximum speed desired was 515 km/h (320 mph). Construction and design had to be as simple as possible. They also wished to speed up the whole development and production process and also to reduce the need for skilled labor. It was especially emphasized that the undercarriage had to be jettisonable, not retractable. It was not expected for the aircraft to fly back, so a retractable landing gear was not needed and this would make the production and design process somewhat quicker.

First Prototype

The job of designing this aircraft was given to Engineer Aori Kunihiro. He was supported by engineers from Ota Manufacturing and the Mitaka Research Institute. While Nakajima received the contract in January 1945, it only took two months to complete the first prototype. In March 1945, this prototype was presented to the Japanese Army and then put through a series of tests. Almost immediately, a series of faults with the design were noted. This was not surprising given that the whole design process lasted only two months. During running on the ground, the fixed and crude undercarriage was difficult to control. The pilot’s poor frontal visibility further complicated matters. This was unacceptable even for skilled pilots, while less experienced pilots would have had great difficulty in successfully operating it on the ground. The Army rejected the prototype and requested a number of modifications to be done.

The Ki-115 first prototype. [ijaafphotos.com]
The Ki-115 cockpit was positioned in the middle of the fuselage and offered the pilot limited forward vision when on the ground. [Wiki]

Technical Specifications

The Ki-115 was designed as a low-wing mixed construction suicide attack aicraft. The front fuselage, containing the engine compartment, and the central part were built using steel panels. The engine compartment was held in place by four bolts and was specially designed to house several different potential engines. Eventually, the Japanese chose the 1,130 hp Nakijama Ha-35 14 cylinder radial piston engine. It had a fixed-pitch three blade propeller. In order to help reach its target quicker, two small auxiliary rocket engines were placed under each wing.

The wings were built using all-metal construction with stressed skin. The rear tail unit was built using wood and was covered by fabric. The cockpit was placed in the upper centre of the fuselage. It was semi-open, with a front windshield.

As requested, the Ki-115 prototype had a fixed and jettisonable undercarriage. It had a very simple design, using simple metal tubes with no shock absorbers. While two wheels were used in the front, a tailskid was used at the rear. The fixed undercarriage tested on the prototype proved to be highly ineffective. All later produced aircraft were instead equipped with a simple and easy to build shock absorber.

Ki-115 side view [ijaafphotos.com]
The armament consisted of a bomb load of up to 800 kg (1,760 lbs). This included using either a single 250 kg (550 lb), 500 kg (1.100 lb) or 800 kg (1.760) bomb. The bomb was not to be dropped on the enemy, but instead be detonated once the aircraft hit its target. Beside the bomb, no other armament was to be provided on the Ki-115.

The Ki-115 was initially meant to be supplied with a fixed undercarriage, which proved to be problematic. Production aircraft were instead provided with simple shock absorbers. [ijaafphotos.com]

The Fate of the Project

Once the prototype was back in Mitaka Kenkyujo (where the prototype was built), the engineers began working on improving its performance. The redesigned undercarriage, which incorporated a simple shock absorber, was completed by June 1945, by which time a series of test flights were done. By August 1945, some 104 Ki-115 aircraft were ready. Two Ki-115s were given to Hikoki K.K., where the Japanese Navy Air Force was developing its own suicide attack aircraft. By the war’s end, none of the Ki-115s built would be used in combat.

Surviving Aircraft

The Ki-115 planes were later captured by the Allies, and nearly all were scrapped. Surprisingly, two Ki-115s have survived to this day. One can be seen at the Pima Air & Space Museum. This aircraft is actually on loan from the National Air and Space Museum. The second aircraft is currently located in Japan. Not wanting to potentially damaged tis aircrafts on the side of caution no restoration attempts are planned for the near future.

The surviving Ki-115 at the Pima Air & Space Museum. [Wiki]
A picture of the second surviving aircraft taken during the 1980’s in Japan. [hikokikumo.net]

The Ki-115b Proposal

In order to further improve the aircraft’s performance and reduce cost, the Ki-115b version was proposed. This included replacing the all-metal wings with ones built of wood. These new wings were larger and had to be equipped with flaps. To provide the pilot with a better view, his cockpit was moved to the front. Due to the end of the war, nothing came from this proposal.

Production and Modifications

The Ki-125 was built in small numbers only, with some 104 production planes plus the prototype. These were built by the two Nakajima production centres at Iwate (22 aircraft) and Ota (82 aircrafts). The production lasted from March to August 1945.

  • Ki-115 prototype – Tested during early 1945.
  • Ki-115 – In total, 104 aircraft were built, but none were used operationally.
  • Ki-115b – Proposed version with larger wooden wings, none built.
Only 105 Ki-115 aircraft, including the prototype, were ever built. [ijaafphotos.com]

Conclusion

Luckily for the Japanese pilots, the Ki-115 was never used operationally. It was a simple and crude design which was born out of desperation. If the Ki-115 was ever used in combat, it would have likely presented an easy target for enemy fighters and suffered from poor reliability due to its cheap construction.

Ki-115 Specifications
Wingspan 28 ft 2 in / 8.6 m
Length 28 ft 1 in / 8.5 m
Height 10 ft 10 in / 3.3 m
Wing Area 133.5 ft² / 12.4 m²
Engine One 1,130 hp Nakijama Ha-35 14 cylinder radial piston engine
Empty Weight 3,616 lbs / 1,640 kg
Maximum Takeoff Weight 6,440 lbs / 2,880 kg
Maximum Speed 340 mph / 550 km/h
Cruising speed 186 mph / 300 km/h
Range 745 miles / 1,200 km
Crew Pilot
Armament
  • Bomb load up to 1,760 lbs (800 kg)

Gallery

Illustrations by Ed Jackson

Another Ki-115 Tsurugi in Natural Metal with 500kg Type 92 Bomb
Ki-115 Tsurugi in Green with 500kg Type 92 Bomb
Ki-115 Tsurugi in Natural Metal with 500kg Type 92 Bomb

Credits

  • Written by: Marko P.
  • Edited by: Stan L. & Henry H.
  • Illustrations by Ed Jackson

Sources

  • R. J. Francillon (1970) Japanese aircraft of the Pacific war, Putham and Company
  • D. Nešić (2007) Naoružanje Drugog Svetskog Rata Japan, Tampoprint
  • D.Mondey (2006) Guide To Axis Aircraft Of World War II, Aerospace Publishing

 

 

 

Yakovlev Yak-4

Soviet, WW2, ,

USSR flag USSR (1939)
Light Bomber – 90 to 100 Built

The Yak-4. [Wiki]
Following the failure of the Yak-2, Yakovlev attempted to salvage the project. One of the attempts that saw limited production was the Yak-4. While it would be powered by a somewhat stronger engine, it too would prove to be a failure and only some 100 aircraft would be built by 1941.

The Yak-2 Failure

While the Yak-2 prototype initially had excellent flying characteristics, once it was actually fully equipped with its military equipment, its performance dropped dangerously. A large number of issues, like overheating, poor flight stability, and problems with its hydraulics, were also noted during the development phase. Despite this, some 100 aircraft would be built and some were even issued for operational use.

Yak-2 side view. [Gordon & Khazanov, Soviet Combat Aircraft]
One of the many weak points of the Yak-2 was its problematic Klimov M-103 engine. The Soviet designers decided to replace this with the more powerfulr M-105 engine. Two basic designs emerged, one for a dive bomber and one for a short-range bomber. During its first test flight, the dive bomber variant proved to be so disappointing that the project was canceled. The bomber version, however, showed to be somewhat promising and the green light for its development was given.

Development History

The development of the BB-22bis (also known as Izdeliye 70bis) prototype was given to Factory No.1, and the Yak-4 designation was officially adopted only in December 1940. Engineers at Factory No. 1 started to build the prototype in early 1940 and it was completed by March the same year. This was not a new aircraft, but a modified Yak-2,serial number 1002) . That same month, Factory No.1 was instructed to produce additional prototypes for testing the aircraft’s performance by the Army, which had to be completed by the start of July 1940. The Army requested a maximum speed of 590 km/h (366 mph) at 5,000 m (16.400 ft)be , an operational range of 1,200 km (745 miles), and a service ceiling of 11,000 m (36,090 ft).

The modified Yak-2 (serial number 1002) aircraft that served as the base for the BB-22bis prototype. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev ]
Following the completion of the first prototype, a series of test flights were carried out. During one of the test flights, carried out on the 12th May, a maximum speed of 574 km/h (356 mph) was achieved. On 23rd May, however, there was an accident and the pilot was forced to crash land at a nearby airfield, damaging two other bombers and the prototype’s wing in the process. Given the extensive damage to the aircraft’s wing, the prototype had to be written off. Due to this and delays in production, the first two trial aircraft could not be completed before the end of 1940. Interestingly enough, these were actually produced by the Moscow Aircraft Factory No.81, which started the production of the Yak-4 during October and November 1940. At that time, the type had not yet received official approval from the Soviet Army.

The damage suffered by the first prototype during its hard landing was so severe that it had to be scrapped. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev]

The two trial aircraft were given to the Army for testing on 10th December 1940. These tests were held at the end of January 1941. The results were once again disappointing, as these aircraft had worse performance than the prototype. With the added weight of equipment and fuel, the maximum speed was reduced from 574 km/h (357 mph) to 535 km/h (332 mph). The cockpit was described as being too cramped, and with the full bomb load, the plane proved to be difficult to control even by experienced pilots. The commission that examined the two aircraft insisted that the Yak-4 should not be accepted for service. In late February 1941, the Director of Factory No.81 gave a report to the Soviet People’s Commissar of the Aircraft Industry, A. Shakhoorin, that the production of the Yak-4 was to be stopped and replaced with the Yak-3. Interestingly enough, while the Yak-2 was developed by Alexander Sergeyevich Yakovlev, he did not direct the design process of the Yak-4.

Technical Characteristics

The Yak-4 was an overall copy of its predecessor, the Yak-2, but there were still some differences. The most obvious change was the introduction of new engines. The older M-103 ,960 hp, was replaced with a stronger M-105 1050 hp engine. The installation of the two new engines also introduced a number of internal improvements to the ventilation and fuel systems. New 3.1 m (122 in) long VISh-22Ye type propellers were also used on this model. The landing gear retracted to the rear into the engine nacelles, but was not fully enclosed. These consisted of two pairs of 700×150 mm wheels.

The rear parts of the fuselage were lengthened and redesigned, and it was less bulkier than the Yak-2. The cockpit was improved in order to provide the crew with a slightly better overall view. The rear gunner received a completely new pivoting canopy. He operated the TSS-1 mount armed with two 7.62 mm (.30 caliber) ShKAS types machine guns.

Rear view of the Yak-4. [Wiki]
The maximum bomb load was increased to 900 kg (1,980 lbs). In addition, there was an option of mounting two 90 (20 gallons) or one 250 liter (54 gallons) auxiliary fuel tanks under each wing. There were six fuel tanks placed in the wings. These had a total capacity of 1,120 litres (244 gallons) of fuel.

A front view of the Yak-4 with its new and stronger M-105 engines. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev]

In Combat

The Yak-4, together with the Yak-2, was allocated to the 314th and 316th Reconnaissance Regiments in the western district. Some were given to the 10th, 44th, 48th, 53rd, 136th and 225th short to medium range Bomber Regiments. The main problem for the units that operated the Yak-2 and Yak-4 was the slow delivery of these aircraft. For example, only a few pilots from the reconnaissance units had a chance to fly on these new aircraft. By 10th June 1941, only limited numbers of Yak-4s were available for service. A shipment of some 10 new aircraft was meant to arrive but did not due to the war’s outbreak.

Pilots from the 314th Reconnaissance Regiment performed several flights over the border with Germany just prior to the Invasion of the Soviet Union while flying Yak-4s. The Germans responded by sending the Bf 109E to intercept them, but they failed to do so. However, once the war started, the German Luftwaffe destroyed many Soviet aircraft on the ground. This was also the case with the Yak-4, with the majority lost this way. Some did survive though and offered limited resistance to the Germans. By September 1941, on the Northern front, there were still fewer than 10 operational Yak-4s. To the South, there were still some 30 or so Yak-4s which were still operational by October 1941. There is no information of the use or losses of the Yak-4 after 1942. According to Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev , at least one Yak-4 was still operational and used by the 118th Reconnaissance Regiment in 1945.

Most of the Yak-4s were destroyed on the ground by the advancing Germans. [Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev]
The advancing Hungarians, who were supporting the Germans during the Invasion of the Soviet Union, managed to capture at least one Yak-4 aircraft during 1941. The use of this aircraft by them would be limited at best, due to the scarcity of spare parts and general poor performance.

Production

The production of the Yak-4 was only carried out at Factory No.81. The production lasted from November 1940 to April 1941. Around 90 to 100 aircraft would be built, with the last 22 Yak-4s being delivered for use by late April 1941.

Operators

  • Soviet Union – Operated some 90 aircraft
  • Hungary – Managed to capture at least one Yak-4 aircraft

Conclusion

Despite attempts to resolve a number of issues noted on the previous version, the Yak-4 in general failed to do so. The problem was the overall poor design of the original Yak-2 which offered little room for improvement. The inability to improve the aircraft to the satisfaction of the Soviet Air Force led to the cancelation of the Yak-4 project after only a small number of aircraft was built.

Yak-4 Specifications
Wingspans 45 ft 11 in / 14 m
Length 33 ft 4 in / 10.18 m
Wing Area 316.4 ft² / 29.4 m²
Engine Two M-105  hp engines
Empty Weight 10,050  lbs / 4,560 kg
Maximum Takeoff Weight 13,481 lbs / 6,115 kg
Climb Rate to 5 km In  6.5 minutes 
Fuel load 1,120 litres (244 gallons)
Maximum Speed  332 mph / 535 km/h
Cruising speed 284 mph  / 458 km/h
Range 460  miles / 740 km
Maximum Service Ceiling 31,824 ft / 9,700 m
Crew Pilot and the rear gunner. 
Armament
  • Two 7.92 mm (.30 caliber) machine guns 
  • 400 to 900 kg (880 to 1.980 lbs) bombs

Gallery

Illustrations by Ed Jackson

Yak-4, 118th Independent Reconnaissance Aviation Regiment, Northern Fleet, 1943
Yak-4, Riga, Latvia, June 1941
Yak-4, 314th Reconnaissance Aviation Regiment, 1941
Yak-4, Grodno, Belarus, June 1941
Yak-4 from the 314th Reconnaissance Aviation Regiment, Babruysk, Belarus, June 1941

Credits

  • Written by: Marko P.
  • Edited by: Stan L. & Henry H.
  • Illustrations by Ed Jackson

Sources

  • D. Nešić (2008), Naoružanje Drugog Svetskog Rata SSSR, Beograd
  • B. Gunston and Y. Gordon (1977)Yakovlev Aircraft Since 1924, Putnam Aeronautical Books.
  • Y. Gordon, D, Khazanov (1999) Soviet Combat Aircraft, Midland Publishing
  • Y. Gordon, D, Khazanov and S. Komissarov (2005) OKB Yakovlev, Midland
  • G. Sarhidai, H. Punka and V. Kozlik. (1996) Hungarian Air Forces 1920-1945, Hikoki Publisher

 

Arado Ar 234A Blitz

Weimar and Nazi Germany, WW2, ,

Nazi flag Nazi Germany (1940)
Jet Powered Bomber & Reconnaissance Aircraft – 8 Prototypes Built 

The Ar 234 A V6 (GK+IW) prototype. [Warbirdphotographs]

Following a request from the German Ministry of Aviation (Reichsluftfahrtministerium – RLM), in 1940, German aircraft manufacturer Arado began working on a new multi-purpose jet powered plane. Arado’s work would lead to the development of the advanced and sophisticated Ar 234 aircraft. During 1943, a small series of eight prototypes would be built and used mainly for testing, but some saw operational service.

History

During the spring of 1940, Arado was contacted by RLM officials with a request to design a completely new multi-purpose jet aircraft to be used for bombers and for reconnaissance duties. This aircraft was to be powered by new jet engines which were under development by Junkers and BMW. Interestingly, besides the request that it should be able to reach the British naval base at Scapa Flow in Northern Scotland, no other performance requirements were specified. The sources do not specify the precise base of operation for these reconnaissance missions. Geographically, the closest territories under German control were south Norway and Denmark, although it is possible that these aircraft would have had to operate from air bases in the occupied territories in Western Europe, either from France, the Netherlands or Belgium. This would require an estimated range of over 900 km. In essence, the RLM gave Arado free reign in terms of the overall design and its performance. If the prototypes built were satisfactory, an initial order for 50 aircraft was to be given.

Work on this new design was given to engineer Rüdiger Kosin, as Arado’s Technical Director, Walter Blume, was uninterested in this project. When work started, it received the Arado Erprobungs (experimental) 370 designation. During the initial phases, there were several different proposals about the number of crewmen, wing size, weapon configuration and the number of engines. After nearly a year, in October 1941, the first proper project, designated the E 370/IVa, was completed. This proposal was mainly intended to be used as a reconnaissance aircraft and was to be equipped with camera equipment. It was to be powered by two BMW P 3302 turbo jet engines. The armament was quite modest and consisted of only one 13 mm MG 131 machine gun. As this aircraft was to operate from short-length airfields, the designers came up with the idea to use a wooden retractable skid for landing, which was to be mounted beneath the fuselage.

E 370/IVa drawings. [Smith & Creek, Arado 234 A]

The project was presented to RLM officials in late October of 1941. They were satisfied and gave permission for the production of 50 aircraft. During the evaluation, it received the 8-234 designation. Unfortunately for Arado, the head of the RLM Technical Department, Ernst Udet, committed suicide just a few weeks later. He was replaced by Erhard Milch, who was more interested in aircraft that were already being produced rather than the proposed Arado project. This without a doubt affected the earlier mentioned initial production order, as the initial order for 50 seems to disappear from record. Despite this setback, work on the E 370 continued. During early 1942, some modifications to the fuselage were made with the aim of increasing its size and strength. The unusual skid undercarriage was replaced by a retractable wheeled bogie system.

In February 1942, Erhard Milch visited the Arado company. He was presented with the drawings and calculations for the improved E 370 model. He was generally impressed with what he saw, and gave his permission for the construction of a wooden mockup. The order would be increased to six prototypes in the following month. The aircraft was to take off using a small three wheel dolly. After the aircraft was in the sky, the dolly was jettisoned and landed with the help of a parachute, meaning it could be used again. In addition, the idea of using a retractable skid undercarriage was reintroduced. If needed, jettisonable Walter HWK auxiliary rocket take-off engines could be attached under the wings. Throughout 1942, many additional modifications and changes were made to the design. Great attention was given to the testing of different engine types and configurations.

By the end of 1942, the number of prototypes to be built was once again increased to 20. The first seven aircraft were to be powered by Jumo 004 engines, with prototype V8 powered by four BMW 003 engines, and V9 through V14 with two BMW 003 engines. The remaining aircraft were to be powered by four BMW 003 engines. The first prototype was meant to be built by November 1943, with the last in October 1944. Surprisingly, these 1942 plans actually started to be completed early, with the first 3 prototypes ready by August 1943. Thanks to this, it was possible to run the first test trials even earlier than anticipated.

Work on the First Prototypes

Work on the construction of the first prototype began in late 1942. During this time, the name was changed to Ar 234. Progress was slow due to problems with the delivery of the Jumo 004 engines, which only arrived in February 1943. These engines were tested and immediately proved to be problematic, as they failed to achieve the promised 850 kg (1879 lbs) thrust. Once fitted with these engines, the first prototype, Ar 234 V1, was used for static ground testing and taxiing trials. No flight was initially accepted due to the short runway at Brandenburg, where the prototype was built. For this reason, the prototype was moved to a Luftwaffe airfield at Munster. During July 1943, this aircraft was mainly used for ground tests. In late July, there was an accident when one of the Jumo engines caught fire. The damage was minor and was quickly repaired. On 30th July, Ar 234 V1 made its first test flight piloted by Horst Selle. The flight was successful, with no problems with the aircraft. The dolly, on the other hand, was lost when the parachute failed to properly open. In early August, there were again problems with the same engine. To avoid any potential threat to the aircraft, it was simply replaced by an engine taken from Ar 234 V3, which was under construction. On 9th August, another test flight was undertaken. During this flight, Selle reached a speed of 650 km/h (400 mph) without any problems. The dolly was once again lost, similarly to the first one. Additional changes were made to the position of the parachute on the dolly, which proved to be the solution to this problem. The V1 prototype would be lost in an accident where the pilot overshot the landing field and crash landed on 29th August. While the aircraft was not repaired, parts of it were reused for testing other equipment.

The Arado 234 V1 first prototype. This particular aircraft would be lost in an accident where the pilot overshot the landing field and crash landed on 29th August 1943. [Warbirdphotographs]
V1 during the third test flight, during which the dolly parachute release system was successfully tested. [Luftwaffephotos]

The V2 prototype was completed in late August 1943. There were some issues with the engine, which had to be replaced. The aircraft was otherwise trouble-free. It was moved to Alt Lonnewitz, where it was mainly used for engine testing. In late September 1943, V3 made its first flight. While, initially, it was to be equipped with a pressurized cabin and an ejector seat, this was never implemented.

In early October 1943, the V2 prototype, with its pilot, Selle, were lost in a fire. This accident prompted the Germans to introduce automatic fire extinguishing systems on all of the Ar 234 prototypes, including later ones. Another change was introducing ejection seats to avoid any further pilot casualties. Due to this accident, there were some delays in the Ar 234 project. Testing continued in November, when V3 was piloted by Walter Kroger. On the 21st of November, the V3 aircraft was transferred to Insterburg to be presented to Adolf Hitler, together with other experimental jet aircraft, like the Me 262 and Me 163. Hitler was highly impressed and even gave orders that some 200 aircraft be built during 1944. During this time, V4 was also flight tested. Both V3 and V4 were used until June 1944 for various roles, including crew training, after which they were removed and replaced with later Ar 234 B versions. By the end of 1943, V5, fitted with Jumo 004 B-0 engines. was introduced.

During early 1944, two Arado 234 aircraft would be tested with a four engine configuration. The idea was that the use of four smaller engines would provide similar performance to the larger ones. V8 was powered by two pairs of BMW P.3302 engines. V6 (which was built later than V8) was tested with four BMW 003 engines placed in four separate wing-mounted nacelles. During a routine flight of V6 at the start of June 1944, all four engines stopped working only 17 minutes after take-off. The pilot was forced to conduct an emergency landing of the plane, after which it caught fire and was heavily damaged, rendering it a complete loss. After this accident, and due to many other engine problems with both versions, all further work on the multi-engined Ar 234 A was discontinued. These would later serve as the basis for the Ar 234 C version instead.

V6 powered by four BMW 003 engines placed in four separated wing cowlings. [Luftwaffephotos]
V6 after a forced landing in June 1944, shortly before the engines began to burn. This accident and problems with the engines put an end to the development of the multi-engined Ar 234 A version. [Warbirdphotographs]
V8 was powered by four BMW P.3302 engines placed in pairs. [Warbirdphotographs]

Technical Characteristics

The Arado Ar 234A (as they were designated later on) prototypes were designed as all metal, high-wing turbojet-powered experimental reconnaissance planes. Their fuselages had a semi-monocoque design with a flat top. The wings consisted of two main spars, each with 29 ribs. They were covered with metal stressed skin. Each wing was connected to the fuselage by four bolts. If needed, these could easily be taken off and removed. At the rear, there was a more or less conventional tail unit.

The Ar 234 was used to test a number of different engines. The first 4 prototypes were powered by two Jumo 004 A-0 engines, which had 840 kg (1,850 lbs) of thrust. V5 and V7 used Jumo 004 B-0 engines which provided 900 kg (1,980 lbs) of thrust. The 3.8 m (12 ft) long engines (both types had the same size) were attached to the wings using three bolts. V6 and V8 were powered by four engines which were able to achieve 800 kg (1,760 lbs) of thrust. As the Ar 234 was intended to be used for reconnaissance operations, a large fuel capacity was important. One 1,800 liter fuel tank was placed behind the cockpit, with a second 2,000 liter tank in the rear of the fuselage. With this fuel load the Ar 234 had an operational range of 1,500 km (930 miles). To assist with take-off, the Ar 234 could be equipped with small Walter 109-500 type rocket engines. These had a run time of 30 seconds and could generate 500 kg (1,100 lbs) of thrust. After the Ar 234 was in the air, the rocket motors would be jettisoned and would land on the ground using small parachutes.

The Ar 234 did not have conventional landing gear, but instead used a three wheel 640 kg (1,410 lbs) jettisonable take-off assist dolly. The Ar 234 pilot could control this dolly by using the rudder, which was connected to hydraulic brakes on the dolly. Once in flight, the dolly would detach and then fall back to Earth using a parachute, and could thereafter be reused. Initially, it was discarded during flight, but this proved to be problematic. After some redesign work, the moment of release was changed to just after take-off. There was no risk of the dolly impacting the fuselage in midair, as the parachute pulled it away from the aircraft. When the Ar 234 had to land, it would use the retractable hydraulically operated skid under the fuselage. The engine nacelles were also provided with smaller skids to avoid any damage to them and to provide better stability during landing. The V3 prototype tested in early 1944 used a drag parachute during landing. This proved to be successful and was later implemented as standard from the B series on.

The smaller front wheel on the jettisonable dolly was fully steerable to help during airfield taxiing and take-offs [Warbirdphotographs]
Close up view of the large sliding skid. [worldwarphotos.info]
Ar 234 during landing. A fuselage skid along with smaller skids placed under the engine nacelles were used instead of wheels. Later versions of the Ar 234 incorporated a conventional wheeled landing gear. [Warbirdphotographs]

The pilot’s cockpit was fully glazed, which provided excellent all around visibility. To enter the cockpit, the pilot used a small hatch placed atop the cockpit. This was not a great design feature as, in an emergency, the pilot could not easily escape the plane. In order to protect the pilot from enemy fire from the rear, a 15 mm thick armor plate was installed behind his seat. Behind this protective armor plate, three oxygen tanks were placed. The instruments were placed on two smaller panels to the left and right of the pilot.

A few Ar 234s were equipped with two Rb 50/30 cameras. These were placed behind the rear fuel tank. These could cover a wide area of 10 km (6 mile) at an altitude of 10 km (33,000 ft).

There were initial plans to arm the Ar 234 with a 13 mm machine gun for self defence. Due to the experimental nature of the Ar 234 A version, no actual armament would actually be installed.

Operational Service

In May 1944, Conny Noell of the Luftwaffe experimental Versuchsverband unit requested that at least two Ar 234 airframes be used for experimental reconnaissance operations after examining the prototypes. The request was accepted and the V5 and V7 aircraft were allocated for this task. Besides the camera equipment, virtually nothing else was changed on these two aircraft.

For the testing of these aircraft, two pilots were chosen, Horst Götz and Erich Sommer. At the start of June 1944, the V5 prototype was tested by Götz during a short 30 minute long flight. He later wrote, after the war “The take-off procedure was not very complicated. First, I engaged the starter, then fed petrol into the combustion chamber until, at approximately 6,000 rpm, I made the gradual change to J2 kerosene. The engines were then reved up to their maximum 9,000 revolutions. After take-off, I throttled the engine back to cruising speed. It was a completely new flying experience. Only a slight whistling noise in the cockpit could be heard. The take-off dolly had functioned quite normally. It was really wonderful”.

Four days later, Sommer also tested this aircraft and gave a similar positive assessment of its overall performance. More flights were undertaken in the following days without major problems. While piloting the V5 prototype during a routine take-off, Götz’ wheeled takeoff dolly release mechanism failed, with the assembly remaining stuck to the aircraft’s landing skids. He immediately tried to land back at the airfield. Despite the dangerous maneuver, he managed to land in a nearby potato field, with minimal damage to the plane.

Around this time, the two test pilots were informed that no prolonged or high-altitude flights had ever been attempted by the Ar 234 prototypes, mostly due to a lack of pressurized cockpit. For this reason, Sommer decided to personally test the Ar 234’s performance at altitude. In late June 1944, he made the first high altitude flight, which lasted over an hour and fifteen minutes at an altitude of 11 kilometers (36,000 ft). During a dive, he managed to reach a speed of 590 km/h (367 mph). A few days later, he made another similar flight that lasted over two hours, during which he managed to cover a distance of 1,435 km (890 miles). When the test flights were completed, both pilots gave positive feedback and evaluations about the performance of the planes and recommended their immediate production.

Following the Allied invasion of German occupied France in 1944, the experimental unit was ordered to move its two aircraft and equipment by train to Juvincourt, in France, by the end of July. Due to delays with the delivery of necessary parts, mostly due to Allied air raids, V7 was finally ready to take to the sky on the 2nd of August. V7’s first operational mission was to take photographs of the Allied landing beaches and the 10 km (6 mile) wide inland strip . The flight was a success, without any problems. The Ar 234’s cameras managed to take nearly 400 photographs of the Allied invasion force, which provided the Germans with vital information about the strength and numbers of the enemy. With this single flight, Sommer managed to achieve what the remaining Luftwaffe reconnaissance units failed to do in two months. During August, some 7 reconnaissance flights were undertaken by the two Ar 234 aircraft. Following the rapid Allied advance, they had to be relocated to Belgium. While V7, piloted by Sommer, arrived without any problems, Götz was less fortunate. During the flight, he was hit by friendly anti-aircraft fire. While damaged, Götz managed to fly up to Oranienburg. But his bad luck for that day was not yet over. His landed Ar 234 aircraft was struck from behind in a ground collision by a Focke Wulf Fw 190 which was attempting a take-off, completely destroying V5. Ironically, the first German operational jet powered aircraft, and the first in the world, was shot down by the Germans and then destroyed by a German fighter plane!

Sommer was stationed with his aircraft at Volkel in Holland until the 5th of September, when it was relocated to Rheine base. On the 10th, Sommer performed a reconnaissance flight over the Thames Estuary but, without direct orders, continued up to London. The next morning, he was informed that, due to this action, he was to be arrested and court martialed. Sommer immediately contacted Götz and explained the situation to him. Götz immediately took action and, after persuasions and threats, managed to get the charges against Sommer dropped. After the war, they both found out who demanded Sommer’s arrest. It was the chief of the V-2 program, Hans Kammler, who had feared that the pictures of London would prove the failure of his rocket program.

Part of the damage suffered by V5 during the forced landing and after being hit by ground anti-aircraft fire, shortly before being hit by an Fw 190 taking off. [Smith & Creek, Arado 234 A]

Sommer made at least four more reconnaissance flights with Ar 234 V7 before it was finally replaced with a B version, which was essentially just a copy of the previous version but with a wider fuselage and a more conventional completely retractable wheeled landing gear. After this, V7 was mainly used for crew training before being damaged during a take-off accident on 19th October 1944. After it was repaired, Götz made a flight to Oranienburg, where the plane was removed from service.

Production

Of the Arado 234 A series, only 8 aircraft were ever produced, as they were used for experimentation of various equipment and engine units.

  • V1 (TG+KB) – Badly damaged during a harsh landing.
  • V2 (DP+AW) – Was lost in a flight accident.
  • V3 (DP+AX) – Was presented to Hitler, who authorized the Ar 234 production. Used for various testing until July 1944.
  • V4 (DP+AY) – Similar to the V3 prototype, used up to June 1944 mainly for crew training, when it was removed from service.
  • V5 (GK+IV) – The first aircraft to be used operationally, but was lost when damaged by friendly ground-based anti-aircraft fire.
  • V6 (GK+IW) – Heavily damaged during a landing accident and caught fire soon after.
  • V7 (GK+IX/ T9+MH) – Used operationally until October 1944, when it was damaged in a take-off accident. Written off as a complete loss.
  • V8 (GK+IY) – Tested with a four engine configuration, but proved to be highly problematic.

Conclusion

While only a small number of Ar 234A planes were built, they proved to be successful designs. During the initial development phase and in their experimental use in service, no major issues were noted. The major drawback was the insufficient quality of the engines and the use of a jettisonable takeoff dolly. Following the success of the Ar 234 A, the development and production of the B and C versions was approved.

Ar 234 V4 Specifications
Wingspans 46 ft 7 in / 14.2 m
Length 38 ft 2 in / 11.65 m
Height 12 ft 6 in / 3.8 m
Wing Area 284 ft² / 26.4 m²
Engine Two Junkers 004 A-0 turbojet
Empty Weight 10,740 lbs / 4,250 kg
Maximum Takeoff Weight 19,180 lbs / 8,700 kg
Fuel Capacity 3,800 l
Maximum Speed 472 mph / 760 km/h
Range 930 miles / 1,500 km
Maximum Service Ceiling 36,090 ft / 11 km
Crew One Pilot
Armament
  • None

Gallery

Illustrations by Ed Jackson

V1, the first prototype, made its first test flight piloted by Horst Selle at the end of July 1943. It would eventually be lost in an accident when the pilot overshot the landing field and crash landed on 29th August 1943.
Ar 234 V5 was the first aircraft of the small production series to be used operationally during the Allied Liberation of France in 1944. It would be lost after a series of unfortunate circumstances culminated with a ground collision with a Focke Wulf 190 which was attempting a take-off. Ironically, the first German operational jet powered aircraft, and the first in the world, was shot down by the Germans and then destroyed by a German fighter plane! V5 was fitted with Jumo 004 B-0 engines.
V6 was tested with four BMW 003 engines placed in four separate wing-mounted nacelles. During a routine flight at the start of June 1944, all four engines stopped working, forcing the pilot to conduct an emergency landing of the plane. After this, the plane caught fire and was heavily damaged, rendering it a complete loss.

Credits

  • Written by Marko P.
  • Edited by Stan L. & Ed J.
  • Illustrations by Ed Jackson
  • D. Nešić (2008), Naoružanje Drugog Svetskog Rata Nemačka Beograd
  • D. Mondey (2006). The Hamlyn Concise Guide To Axis Aircraft OF World War II, Bounty Books.
  • J. R. Smith and E. J. Creek (2006) Arado 234 A, Chevron Publishing
  • R. P. Bateson, Profile 215 ARADO Ar 234 Blitz
  • M. Griehl (2012) X-Planes German Luftwaffe Prototypes 1930-1945, Frontline Book
  • Jean-Denis G.G. Lepage Aircraft Of The Luftwaffe 1935-1945, McFarland and Company.
  • D. Donald (1998) German Aircraft Of World War II, Blitz Publisher

Messerschmitt P.1101

Weimar and Nazi Germany, WW2, ,

Nazi flag Nazi Germany (1944)
Jet Fighter – 1 Incomplete Prototype Built 

The P.1101 prototype after the war [Wiki]


During the war, German scientists and engineers managed to develop and build a number of jet powered aircraft, several of which went on to see combat. What is generally less known are the large number of experimental jets that were proposed and prototyped. These designs utilized a great variety of engines, airframes, and weapons. One of these unfinished projects was the Messerschmitt P.1101 jet fighter.

Need for a New Jet Fighter

Line drawing of the P.1101 [Luftarchiv]
During the war, the Germans introduced the Me 262, which had the honor of being the first operational jet fighter in the world. While it provided better performance than ordinary piston powered aircraft, it was far from perfect. The greatest issues were that it was expensive to build, required two jet engines, and could not be built in sufficient numbers. The German Air Ministry (Reichsluftfahrtministerium; RLM) wanted a much simpler and cheaper design powered by a single engine. They issued a competition for a new jet fighter ,code named 1-TL-Jäger, during July 1944 for all available aircraft manufacturers. Some of the requirements listed were that it would be a single seater, have a maximum speed of 1000 km/h (620 mph), an endurance of at least one hour, armor protection for the pilot, make use of the Heinkel HeS 011 engine, and had an armament that had at least two 30 mm (1.18 in) MK 108 cannons. During a meeting with the leading German aircraft manufacturers held in September 1944, Messerschmitt presented the P.1101designed by Waldemar Voight.

The Messerschmitt P.1101 Development History

Drawing of the P.1101 before a number of design changes were introduced. [Luft46.com]
Messerschmitt’s engineers and designers began working on designing a single engined jet aircraft at the start of 1943. Two projects, P.1092 and P.1095, were both powered by a single Jumo 004 jet engine, but, as the Me 262 was entering full production, their development was largely suspended. These projects were shelved until the RLM competition in 1944. Seeing a new opportunity, Messerschmitt presented drawings of a new project named P.1011, which was influenced by the previous projects. It had an all-metal fuselage construction and was powered by one HeS 011 engine with the air intakes placed on the wing’s roots. It also had a V-tail.

Following the meeting with the RLM officials in September, some changes were made to the P.1101’s overall design. Instead of two air intakes, a single one in the nose was to be used. This also necessitated the redesigning of the cockpit, which was moved back. In addition, the rear V-tail was replaced with a standard fin design. At this early stage, the possibilities of using this aircraft for other purposes were still being explored. Beside the standard fighter, other roles which were considered were night fighter and interceptor. On 10th November, the owner of the company, Willy Messerschmitt, issued orders to begin working on the first experimental prototype. To speed up the developing time, it was proposed to reuse the already produced components of the Me 262. The Me 262 fuselage, wings design and construction were to be copied.

End of the Project

The P.1101 prototype was only partially completed in early 1945. It appears that, despite Messerschmitt’s attempts to complete this project, the RLM simply lost interest. Messerschmitt’s other projects, like the P.1110 and P.1111, showed greater potential than the P.1101. This, together with the fact that the promised engine never arrived, meant that the single incomplete prototype was put into storage at the Messerschmitt Oberammergau research center. It remained there until the war’s end, when it was captured by American forces.

Technical Characteristics

Side view of the P.1101. This picture was taken at the Messerschmitt Oberammergau base. [Luftarchiv]
The P.1101 was a single seater, jet engine-powered mixed construction fighter. The lower parts of the all-metal fuselage were designed to house the jet engine. In the front of the fuselage, a round shaped intake was placed. To the rear, the fuselage was additionally reinforced to avoid any damage due to the heat of the jet exhaust. The underside of the fuselage was to have a skid to help better land during an emergency.

While it was originally intended to be powered by the HeS 011 engine, the power plant was never supplied and the Jumo 004B was to be used as a replacement. The main fuel tank, with a capacity of 1,100 liters (290 gallons), was placed just behind the cockpit. Only a mock-up engine was ever installed in this aircraft, so it was never tested properly, even on the ground. Due to this, it is unknown what the P.1101’s overall flight performance would have been. Some sources give rough estimates, such as that it could have reached 890 km/h (550 mph) at sea level and up to 980 km/h (610 mph) at higher altitudes. Of course, these are only estimations contingent on the fact that the plane had no other problems during operational flight. In addition the general ability to test flight characteristics in the transonic-supersonic range were extremely crude at this point.

Close up view of the P.1101’s large front air intake for the jet engine. The markings painted on it were probably added by the Americans after the war. [Luftarchiv]
The wing’s were made of wood materials. The prototype would have a completely innovative feature, namely the sweep angle of the wings could be adjusted at different angles ranging between 35° and 45°. The rear vertical and horizontal tail assembly was also made of wood.

The P.1101 had a retracting tricycle-type landing gear. It consisted of one forward mounted and two mid-fuselage wheels. All three retracted rearwards into the fuselage. The cockpit had a round shaped canopy with good all around vision.

The basic armament configuration consisted of two MK 108 cannons with 100 rounds each. These were placed in the front lower part of the fuselage. There were proposals to increase the firepower by adding two more MK 108 cannons, and the use of experimental air-to-air missiles was also considered. As the prototype aircraft was built to test overall flight performance, no armament was ever installed.

Rear view of the tail assembly. [Luftarchiv]

In American Hands

The restored P.1101 in America. [Pinterest]
Advancing American soldiers reached the Messerschmitt Oberammergau base during April (or May) 1945. The single P.1101 was found there and, for some time, left open to the elements. The Bell Aircraft Chief Designer Robert Woods came to know of the existence of this aircraft. Once he had a chance to examine it, he organized for it to be shipped back to America for further study. It would be restored and used as testing mock up aircraft. The Bell aircraft design bureau paid great interest to the variable wing design. Working from the P.1101, they would eventually develop the Bell X-5, one of the first operational aircraft that could change the position of its wings during flight.

The Bell X-5 aircraft, which was heavily influenced by the German P.1101 design [WIki]

Conclusion

While incorporating the innovative feature of variable swept wings, the P.1101 was another victim of the chaotic state Germany was in at the end of war. Whether this aircraft could have performed its role is unknown, and while it never flew for the Germans, it helped the Americans develop the Bell X-5 after the war which incorporated the same variable wing design.

P. 1101 Specifications
Wingspans 27 ft / 8.24 m
Length 30 ft 1 in / 9.13 m
Height 9 ft 18 in / 2.8 m
Wing Area 170 ft² / 15.8 m²
Engine One Jumo 004B or one HeS 011
Empty Weight 5,725 lbs/ 2,600 kg
Maximum Takeoff Weight 8,950 lbs / 4,060 kg
Fuel Capacity 1,100 l / 290 Gallons
Estimated Maximum Speed 610 mph / 980 km/h
Estimated Cruising speed 550 mph / 890 km/h
Crew 1 pilot
Armament
  • Two 108 MK cannons
Messerschmitt P.1101 Prototype
Initial P.1101 Design prior to changes

Credits

  • Article by Marko P.
  • Edited by Stan L. and Henry H.
  • Illustrated by Carpaticus
  • D. Nešić, (2008). Naoružanje Drugog Svetsko Rata-Nemačka. Beograd.
  • D. Monday. (2006). The Hamlyn Concise Guide To Axis Aircraft Of World War II, Bounty Books.
  • D. Sharp (2015) Luftwaffe Secret Jets of the Third Reich, Mortons Media Group
  • M. Griehl (2012) X-Planes, Frontline Books
  • R. Ford (2000) German Secret Weapons of World War Two, MBI Publishing
  • Jean-Denis G.G. Lepage (2009) Aircraft of the Luftwaffe 1935-1945, McFarland and Company
  • J. R. Smith and A. L. Kay (1972) German Aircraft of the Second World War, Putnam
  • http://www.luft46.com/mess/mep1101.html

Modli J.M. 8

Cold War, Yugoslavia, , ,

Yugoslavia flag Yugoslavia (1939-1950)
Trainer – 2 Prototypes

The Modli-8 in use with the Yugoslav Aviation after the war. www.paluba.info

The Modli J.M. 8 was designed in the Kingdom of Yugoslavia, built by the Independent State of Croatia (NDH), and after World War II, operated by the Federal People’s Republic of Yugoslavia (FPRY). It was an inexpensive training aircraft that would be used in this role up to 1950.

The Beginning

The story of the Modli J.M. 8 began in 1938, when an aircraft engineer from the 1st Air Force Regiment (stationed at Novi Sad), Josip Modli, finished work on a new light training aircraft design. He originally intended to design and build a single seat trainer that was cheap and simple to manufacture by using mostly wood. He also intended to gain the interest of amateur aviators and aeroclubs with a low price. The J.M. 8 designation comes from the initials of the designer’s name. Due to its small size and low price, it earned the nickname Komarac/komaрац (Mosquito).

The following year, Modli actually began building this aircraft. He reused the small 18 hp engine taken from a damaged French HM.14 Pou du Ciel (Nebeska Vaš/Небеска Ваш in Serbian). Four had been bought from France in 1935 but, due to construction problems, their use was limited and all were damaged during test flights. One was tested at Novi Sad, where the 1st Air Force Regiment was stationed.

Modli reused the engine from a damaged HM.14 Pou du Ciel for his first prototype. Four of these small aircraft were bought from France. www.vazduhoplovnetradicijesrbije.rs

At that time, word of his design and work reached the Yugoslavian Air Force Headquarters. Headquarters then instructed (or ordered, depending on the sources) aircraft engineer Tišma, who was co-owner of the Albatros aircraft manufacturer from the cit of Sremska Mitrovica, to contact Modli. After short negotiations, Tišma and Modli reached an agreement that Albatros should finish the construction of the J.M. 8.  If the design received any mass production orders, Modli agreed to provide Albatros with a license for its production.

The J.M. 8 was completed in early 1941, with testing scheduled to begin in March. Due to bad weather, Albatros’ main airport at Ruma was flooded during March and early April, so no tests flights were conducted. During the outbreak of the April War (Axis invasion of Yugoslavia), all finished and partially constructed planes from Albatros were loaded on a train on the 10th of April. Because of the great confusion due to the outbreak of war and the lack of documentation, the fate of this train and its cargo is unknown to this day.

After the end of  the April War, the Serbian Air Force Commission made estimates of all unpaid pre-war designs, including the Modli J.M. 8, in order to arrange for future payments for military contracts. The commission, after analysis of the Modli J.M. 8 documentation, concluded that the aircraft did not meet any military requirements and was suitable for civilian use only.

Technical Characteristics 

The Modli J.M. 8 was designed as a single engined, high wing, mixed construction (but mostly wood) training aircraft. Its fuselage had a simple design made of plywood. The high wings and the rear tail were made of a wooden structure covered with fabric. For better flight controls, Modli used two modified Gottingen 426 longerons. The wings were connected to the fuselage with three “N” shaped metal bars on both sides and with two additional ones in the centre. The tail had a large rudder and elevators made of wood.

It was powered by the two cylinder Aubier & Dunne 18 hp engine. The engine compartment was covered with duralumin. The two-bladed propeller was made of walnut. A fuel tank with a capacity of 16 liters was placed in the center of the wing.

The Aubier & Dunne 18 hp engine was reused for the first prototype. Source: www.vazduhoplovnetradicijesrbije.rs

The landing gear was fixed, but was equipped with rubber shock absorbers for greater comfort and control during  landing. There was no rear wheel, being instead equipped with a small skid and shock absorber.

The pilot’s cockpit was fully open with a small windshield at the front. The cockpit had a simple design and was equipped with basic controls and instrumentation. These flight instruments included an airspeed indicator, fuel level, tachometer, and altimeter. As the first prototype was never adequately tested, details about its flying performance are not known.

During World War II

After the Yugoslavian capitulation, its territories were divided between the Axis forces. The Germans created the Independent State of Croatia (Nezavisna Država Hrvatska) puppet state. Despite promises of sending military equipment, weapons and aircraft, the NDH was mostly supplied with older or captured equipment. The NDH aviation industry was heavily dependent on supplies from Germany and Italy, as it lacked any major production capacity or industrial development, meaning domestic production was not possible. The only attempt at domestic production was with the Modli aircraft.

In 1941, Modli joined the new NDH Air Force with the rank of Flight Captain as a flight school instructor. He immediately began working on his second prototype, now simply called Modli-8. Unlike his first prototype, the second one was powered by a stronger four-cylinder Praga-B giving 40 hp. As this engine was too strong for the prototype, its power was reduced to just 20 hp. For the landing gear, two smaller rear wheels from a German Me-109 were reused. The Modli-8 was also shorter in comparison to the first prototype by 0.94 ft (15 cm).

In 1943 Modli was transferred to the technical workshop of the 1st Air Base in Zagreb, where he continued to develop his plane. In 1944, the Modli-8 was completed and introduced to NDH operational service according to authors T. Lisko  and D. Čanak. Unfortunately, they do not give more information on its service history. According to authors B. Nadoveza and N. Đokić on the other hand, noted that Modli deliberately delayed the production of the Modli-8 and it was never fully completed for use by the NDH.

On 26th October 1944, Josip Modli fled to Slovenia at the helm of a Bücker Bü 131 “Jungmann” in hopes of joining the Yugoslav Communist Partisans. Meanwhile, his assistants and friends in Zagreb hid the Modli-8 prototype in the attic of an old shed. Due to the chaos and confusion caused by the war, it was easy to hide the small and lightweight prototype. The Modli-8 would survive the war intact.

The Modli-8 was the only NDH domestically-built aircraft during the War. These two pictures may be the only ones of the Modli-8. Source: www.paluba.infok

In NDH service, the Modli-8’s lower fuselage, wings, and tail were painted in silver. The upper part of the fuselage and vertical stabilizer was blue. The wings struts were painted in red, while the middle of the fuselage wore a red stripe on both sides with a white outline. There were NDH markings with a large “JM8” painted on the tail. The color scheme would remain the same after the war but the NDH marking would be replaced with the Communist Star.

After the War

After the collapse of the NDH and the German forces in Yugoslavia, Modli, now Captain in the Yugoslav People’s Army, moved his prototype from Zagreb to Skopje, where it was completed in an army workshop. Modli himself flew the prototype during the summer of 1945. Surprisingly , he did not report this flight to his superiors and an alarm was raised, with several fighters launched to intercept him. Modli was lucky, as this incident did not affect his military career. The Modli-8 was, by order of Air Force Command, moved to Belgrade for further tests. The aircraft proved to be a good design, as it was easy and pleasant to fly according to test pilot Vasilije Vračević. There were some issues with the sensitivity of the large rudders and elevators during flight. For take off, it only needed a very short 170 m (558 ft) runway, and could land on a 125 m (410 ft) airfield. The maximum speed was around 100 km/h 223 mph at an altitude of 1 km.

The Modli-8 was then given to Aircraft Center Vršac, where it was used for training and propaganda flights. It was used operationally up to 1950, when it was removed from Army service. During its operational service, the Modli-8 was also used as a glider trainer. Under the right conditions it could be used as a glider with the engine shut off, which was useful for glider training.

Josip Modli later (date unknown) designed a two-seater version named Modli-9, but it was never fully completed. Both the Modli-8 and the unfinished 9 were given to the Croatian Technical Museum (Zagreb)  after the death of Josip Modli in 1974.

Production and Modifications

Despite being cheap, easy to build, and pleasant to fly, the Modli-8 was never adopted for military or civilian service. The first prototype was never fully tested due to the outbreak of the war and was lost (precise fate unknown). The second prototype was built during the war and was in use up to 1950. Despite the good feedback for its flight performance from the military, the Modli-8 was rejected for production, mostly due to the recent adoption of the BC-3 Trojka.

Modli J.M.8 – First prototype powered with Aubier & Dunne engine, lost in WW2.

Modli-8 – Second prototype powered by Praga-B engine and with other minor improvements, in service until 1950.

Modli-9 – Two-seater version, never fully completed.

Conclusion

Despite the few number of built aircraft, the Modli J.M. 8 had a small but interesting development history, changing owners several times. It had the honor of being the only aircraft built in Croatia during World War II. Despite its simplistic nature, it saw extensive use as a trainer after the war.

Operators

  • Kingdom of Yugoslavia – One built prototype
  • Independent State of Croatia (NDH) – Constructed one prototype but never tested
  • Federal People’s Republic of Yugoslavia (FPRY) – Operated the Modli-8 up to 1950.

Modli-8 (second prototype) Specifications
Wingspans 31 ft 2 in / 9.5 m
Length 19  ft 7 in / 6 m
Height 6 ft  / 1.85 m
Wing Area 36.25 ft² / 11.05 m²
Engine One four cylinder Praga-B 40 hp engine
Empty Weight 474 lbs / 215 kg
Maximum Takeoff Weight 705  lbs / 320 kg
Fuel Capacity 16 l
Climb Rate to 1 km In 10 minutes
Maximum Speed at 1 km 223 mph / 100 km/h
Take of run 558 ft / 170 m
Landing run 410 ft / 125 m
Range 124 mi / 200 km
Maximum Service Ceiling 5578 ft / 1,700 m
Crew 1 pilot
Armament
  • None

Gallery

Illustrations by Carpaticus

Modli Croatia
Modli Yugoslavia

Sources:

  • T. Lisko  and D. Čanak (1998), The Croatian Air Force In The WWII, Nacionalna i sveučilišna knjižnica, Zagreb
  • Vojislav V. Mikić, (2000) Zrakoplovstvo Nezavisne države Hrvatske 1941-1945, Vojno  istorijski institut Vojske Jugoslavije
  • B. Nadoveza and N. Đokić (2014), Odbrambena Privreda Kraljevine Jugoslavije, Metafizika Beograd.
  • Nebojša Đ.and Nenad M. (2002), IPMS Yugoslavia and Yugoslavian Aviation Special Interest Group Bulletin No 1-4, 

 

 

Focke-Wulf Fw Triebflügel 

Weimar and Nazi Germany, WW2, , ,

Nazi flag Germany (1944)
Experimental VTOL Fighter – Paper Project

The bizarre looking Focke-Wulf Triebflügel fighter design. [luft46.com]
During the war, German aviation engineers proposed a large number of different aircraft designs. These ranged from more or less orthodox designs to hopelessly overcomplicated, radical, or even impractical designs. One such project was a private venture of Focke-Wulf, generally known as the Triebflügel. The aircraft was to use a Rotary Wing design in order to give it the necessary lift. Given the late start of the project, in 1944, and the worsening war situation for Germany, the aircraft would never leave the drawing board and would remain only a proposal.

History

During the war, the Luftwaffe possessed some of the best aircraft designs and technology of the time. While huge investments and major advancements were made in piston engine aircraft development, there was also interest in newer and more exotic technologies that were also being developed at the time, such as rocket and jet propulsion. As an alternative to standard piston engine aircraft, the Germans began developing jet and rocket engines, which enabled them to build and put to use more advanced aircraft powered by these. These were used in small numbers and far too late to have any real impact on the war. It is generally less known that they also showed interest in the development of ramjet engines.

Ramjets were basically modified jet engines which had a specially designed front nozzle. Their role was to help compress air which would be mixed with fuel to create thrust but without an axial or centrifugal compressor. While this is, at least in theory, much simpler to build than a standard jet engine, it can not function during take-off. Thus, an auxiliary power plant was needed. It should, however, be noted that this was not new technology and, in fact, had existed since 1913, when a French engineer by the name of Rene Lorin patented such an engine. Due to a lack of necessary materials, it was not possible to build a fully operational prototype at that time, and it would take decades before a properly built ramjet could be completed. In Germany, work on such engines was mostly carried out by Hellmuth Walter during the 1930s. While his initial work was promising, he eventually gave up on its development and switched to a rocket engine insead. The first working prototype was built and tested by the German Research Center for Gliding (Deutsche Forschungsinstitut für Segelflug– DFS) during 1942. The first working prototype was tested by mounting the engine on a Dornier Do 17 and, later, a Dornier Do 217.

The Dornier Do 217 was equipped with experimental ramjets during trials. [tanks45.tripod.com]
The Focke-Wulf company, ever keen on new technology, showed interest in ramjet development during 1941. Two years later, Focke-Wulf set up a new research station at Bad Eilsen with the aim of improving already existing ramjet engines. The project was undertaken under the supervision of Otto Ernst Pabst. The initial work looked promising, as the ramjets could be made much cheaper than jet engines, and could offer excellent overall flying performance. For this reason, Focke-Wulf initiated the development of fighter aircraft designs to be equipped with this engine. Two of these designs were the Strahlrohr Jäger and the Triebflügel. The Strahlrohr had a more conventional design (although using the word conventional in this project has a loose meaning at best). However, in the case of the Triebflügel, all known and traditional aircraft design theory was in essence thrown out the window. It was intended to take off vertically and initially be powered by an auxiliary engine. Upon reaching sufficient height, the three ramjets on the tips of the three wings would power up and rotate the entire wing assembly. It was hoped that, by using cheaper materials and low grade fuel, the Triebflügel could be easily mass-produced.

A model of the Triebflügel. This is how it may have looked if completed. [Wiki]

The Name

Given that these ramjet powered fighter projects were more a private venture than a specially requested military design, they were not given any standard Luftwaffe designation. The Triebflügel Flugzeug name, depending on the sources, can be translated as power-wing, gliding, or even as thrust wing aircraft. This article will refer to it as the Triebflügel for the sake of simplicity. 

Technical Characteristics  

Given that the Triebflügel never left the drawing board, not much is known about its overall characteristics. It was designed as an all-metal, vertical take-off, rotary wing fighter aircraft. In regard to the fuselage, there is little to almost no information about its overall construction. Based on the available drawings of it, it would have been divided into several different sections. The front nose section consisted of the pilot, cockpit, and an armament section for cannons and ammunition, which were placed behind him. Approximately at the centre of the aircraft, a rotary collar was placed around that section of the fuselage. Behind it, the main storage for fuel would be located. And at the end of the fuselage, four tail fins were placed. 

A drawing of the Triebflügel’s interior. [luft46.com]
This aircraft was to have an unusual and radical three wing design. The wings were connected to the fuselage while small ramjets was placed on their tips. Thanks to the rotary collar, the wings were able to rotate a full 360o around the fuselage. Their pitch could be adjusted depending on the flight situation. For additional stability during flight, the tail fins had trailing edges installed. The pilot would control the flying speed of the aircraft by changing the pitch.  Once sufficient speed was achieved (some 240 to 320 km/h (150 to 200 mph)), the three ramjets were to be activated. The total diameter of the rotating wings was 11.5 m (37  ft 8  in) and had an area of 16.5 m² (176.5 ft²). 

This unusual aircraft was to be powered by three ramjets which were able to deliver some 840 kg (1,1850 lb) of thrust each. Thanks to ramjet development achieved by Otto Pabst, these had a diameter of 68 cm (2.7 ft), with a length of less than 30 cm (0.98 ft). The fuel for this aircraft was to be hydrogen gas or some other low grade fuel. The estimated maximum speed that could be achieved with these engines was 1,000 km/h (621 mph). The main disadvantage of the ramjets, however, was that they could not be used during take-off, so an auxiliary engine had to be used instead. While not specifying the precise type, at least three different engines (including jet, rocket, or ordinary piston driven engines) were proposed.

In the fuselage nose, the pilot cockpit was placed. From there the pilot was provided with an overall good view of the surroundings. The main issue with this cockpit design wass the insufficient rear view during vertical landing. 

Close up view of the Triebflügel landing gear assembly. [Secret Jets of the Third Reich]
The landing gear consisted of four smaller and one larger wheels. Smaller wheels were placed on the four fin stabilizers, while the large one was placed in the middle of the rear part of the fuselage. The larger center positioned wheel was meant to hold the whole weight of the aircraft, while the smaller ones were meant to provide additional stability. Each wheel was enclosed in a protective ball shaped cover that would be closed during flight, possibly to provide better aerodynamic properties. It may also have served to protect the wheels from any potential damage, as landing with one of these would have been highly problematic. Interestingly enough, all five landing wheels were retractable, despite their odd positioning.  

The armament would have consisted of two 3 cm (1.18 in) MK 103s with 100 rounds of ammunition and two 2 cm (0.78 in) MG 151s with 250 rounds. The cannons were placed on the side of the aircraft’s nose. The spare ammunition containers were positioned behind the pilot’s seat.

Final Fate

Despite its futuristic appearance and the alleged cheap building materials that would have been used in its construction, no Triebflügel was ever built. A small wooden wind tunnel model was built and tested by the end of the war. During this testing, it was noted that the aircraft could potentially reach speeds up to 0.9 Mach, slightly less than 1,000 km/h. The documents for this aircraft were captured by the Americans at the end of the war. The Americans initially showed interest in the concept and continued experimenting and developing it for sometime after. 

In Modern Culture 

The Triebflügel taking off in the movie. [marvelcinematicuniverse.fandom.com]
Interestingly, the Triebflügel was used as an escape aircraft for the villain Red Skull in the 2011 Captain America: The First Avenger movie.

Conclusion

The Triebflügel’s overall design was unusual to say the least. It was a completely new concept of how to bring an aircraft to the sky. On paper and according to Focke-Wulf’s engineers that were interrogated by Allied Intelligence after the war, the Triebflügel offered a number of advantages over the more orthodox designs. The whole aircraft was to be built using cheap materials, could achieve great speeds, and did not need a large airfield to take-off, etc. In reality, this aircraft would have been simply too complicated to build and use at that time. For example, the pilot could only effectively control the aircraft if the whole rotary wing system worked perfectly. If one (or more) of the ramjets failed to work properly, the pilot would most likely have to bail out, as he would not have had any sort of control over the aircraft. The landing process was also most likely very dangerous for the pilot, especially given the lack of rear view and the uncomfortable and difficult position that the pilot needed to be in order to be able to see the rear part of the aircraft. 

The main question regarding the overall Triebflügel design is if it would have been capable of successfully performing any kind of flight. Especially given its radical, untested and overcomplicated design, this was a big question mark. While there exist some rough estimation of its alleged flight performances, it is also quite dubious if these could be achieved in reality. The whole Triebflügel project never really gained any real interest from the Luftwaffe, and it is highly likely that it was even presented to them. It was, most probably, only a Focke-Wulf private venture.

Triebflügel Estimated  Specifications
Rotating Wing diameter 37  ft 8  in / 11.5 m
Length 30 ft / 9.15 m
Wing Area 176.5 ft² / 16.5 m²
Engine Three Ramjets with 840 kg (1,1850 lb) of thrust each
Empty Weight 7,056  lbs / 3,200 kg
Maximum Takeoff Weight 11,410 lbs / 5,175 kg
Climb Rate to 8 km In 1 minute 8 seconds
Maximum Speed  621 mph / 1,000 km/h
Cruising speed 522 mph  / 840 km/h
Range 1,490  miles / 2,400 km
Maximum Service Ceiling 45,920 ft / 14,000 m
Crew 1 pilot
Armament
  • Two 3 cm MK 103 (1.18 in) and two 2 cm (0.78 in) MG 151 cannons

Gallery

A rendition of how the Triebflugel may have looked had it been built. Illustration by Pavel ‘Carpaticus’ Alexe.

Credits

  • Article by Marko P.
  • Duško N. (2008)  Naoružanje Drugog Svetsko Rata-Nemačka. Beograd.
  • D. Sharp (2015) Luftwaffe Secret Jets of the Third Reich, Dan Savage
  • Jean-Denis G.G. Lepage (2009) Aircraft of the Luftwaffe 1935-1945, McFarland and Company  
  • J.R. Smith and A. L. Kay (1972) German Aircraft of the Second World War, Putham  
  • http://www.luft46.com/fw/fwtrieb.html 

 

Yakovlev Yak-2

Soviet, WW2

USSR flag USSR (1939)
Ground attack bomber – 100 Built

The Yak-2. Source: Y. Gordon, D, Khazanov Soviet Combat Aircraft

During his career, Alexander Sergeyevich Yakovlev designed a number of successful aircraft, his most famous being his single engine fighters. But his first proper military aircraft project, the Yak-2, would be so poorly designed that it was practically useless. Nevertheless, thanks to Yakovlev’s good standing with Stalin, this aircraft would be put into production, albeit in small numbers, and would see limited action during World War Two.

The No-22 and BB-22 projects

While being involved in civil aviation, Yakovlev wished to pursue military contracts., Yakovlev actually wanted to gain a proper military contract. He estimated that the best way to do this was to impress Stalin himself. To do so, he set on designing the fastest plane in the Soviet Union. Having no previous experience in designing military aircraft, this was no easy task. Nevertheless, he soon began working on a two-engined mixed construction aircraft named simply the No.22 (but also known as the Ya-22). When the prototype was complete and flight tested it reached a maximum speed of 567 km/h (352 mph). This design would first be presented to the Soviet Spanish Civil War hero Yakov Smushkeviche, who was also the Chief of the Soviet Air Force. Yakov was highly impressed with this aircraft and informed Stalin about its performance. Stalin agreed and gave a green light for its future development.

In May of 1939, for further testing and evaluation, this prototype would be given to the Nauchno Issledovatelysii Institut (NII VVS). There, the aircraft was evaluated by a commission consisting of Chief engineer Holopov, test pilot Shevarev, and navigator Tretyakov. They managed to reach a maximum speed of 567 km/h (352 mph) without any problems. The commission also suggested that, with an improved cooling system and with new propellers, the maximum speed could be increased up to 600 km/h (372 mph).

When Yakovlev began working on the No.22, he did not seriously consider in which role it should be used. Military officials would decide the aircraft would be used as a light bomber, a use that both Yakovlev and Stalin would agree with. The plane would be renamed BB-22  (Blizhnii Bombardirovshchik, short range bomber) to fit its new role.

 

The BB-22 prototype, Source: Source: Y. Gordon, D, Khazanov Soviet Combat Aircraft

While at first glance the BB-22 showed to be capable of racing at high speeds, its use in military aviation would prove to be highly problematic. The core of this problem lay in the fact that this aircraft was designed with the main purpose of reaching the highest possible speed, with little thought for military adaptation. Very shortly, the BB-22 began showing the first signs of being an inadequate design. While being tested, it was noted that the engine was prone to overheating. During one test flight, the pilot attempted to reach 7,000 m (23,000 ft) which the designers claimed that it could reach in 8 minutes. In reality, the pilot needed more than half an hour due to constant engine overheating problems. Other issues were also noted, like the inadequate fuel system and wheel brakes.

In the meantime, Air Force officials were discussing the BB-22’s performance and if it should have been put into production. Nearly two months earlier, Yakovlev had already made first steps for the BB-22’s production without their knowledge, despite no official order being given. While military officials were still discussing the BB-22, he had already given copies of the design to GAZ’s Plant No.1. In June 1939, the Council of Soviet People’s Commissars officially gave orders to put the BB-22 into production. The first production aircraft was completed by the end of 1939, and thanks to the political machinations of its designer, made its first flight in February 1940. Production of the aircraft was subsequently delayed. By the end of 1939, of the planned 50, only one was built. Despite these problems, the Soviet Defence Committee issued orders for 580 new aircraft to be built.

 

Work on the Yak-2

Despite the best attempts of Soviet Air Force officials to cancel the BB-22 project, they were hindered by two facts. First was the fact that Stalin personally showed significant interest in its development. Secondly, Yakovlev was appointed as the Deputy People’s Commissar for aircraft production. As a result, the aircraft’s production could not be interrupted. In November 1940, the name of the aircraft was changed to Yak-2, as it was common practice in the Soviet Union to name the aircraft after their designers

By March 1940, after numerous tests and attempts to improve this aircraft, it simply proved to be unusable due to many mechanical flaws. These included the engine overheating, poor flight stability, problems with hydraulics, insufficient quality of bolts that held the wings etc. In total, over 180 faults were reported. The situation was so bad that the Directorate of the Soviet Army Land-based Aviation actually demanded the cancellation of any further work on the Yak-2. On the other side, GAZ No.1 plant officials (who were responsible for the production of this aircraft), along with their test pilots who had flown on this plane, urged its production in order to stay in Yakovlev’s graces. There were plans to produce the first series of 21 aircraft that would be ready by May 1940. After numerous complaints about the Yak-2’s performance, Stalin ordered that the whole situation be investigated. To avoid any kind of guilt, Yakovlev simply blamed the GAZ No.1 production plant for the Yak-2’s poor quality. Ultimately, only 100 Yak-2s would be built and given to the Air Force for operational use.

 

Yak-2 side view. Source: Pinterest

Technical characteristics

The Yak-2 was designed as a twin-engined, mixed-construction low-wing light bomber. The frontal part of the fuselage was made of duralumin. The central part of the fuselage, which was integrated into the wings, was made of wood. The rear part of the fuselage consisted of a welded steel tube frame that was covered with fabric. This rear part could be, if needed (for repairs for example), be separated from the remainder of the aircraft.

The Yak-2 was powered by two Klimov M-103 960 hp liquid cooled engines. The two engines were placed in wing nacelles, on each side of the central fuselage.

op view of the Yak-2. The two engines could be clearly seen. Source: Wiki

The Yak-2 had standard retractable landing gear units, which consisted of two larger frontal wheels and one smaller to the rear. All three retracted to the rear, with the frontal two retracting into the engine nacelles. While, initially, the aircraft had only one large frontal landing wheel on each side, the majority would be built with twin-wheels on each side.

Unusually, the wings were built using only a single large piece. This greatly limited the possibility of transporting this plane by rail. The wings were built using two metal spar structures which were covered with plywood skin. At the rear of the fuselage, the twin-finned tail was positioned.

While it was based on the BB-22, unlike it, the Yak-2 received a modified canopy with both crew members being placed in it. The pilot was placed in front, while the navigator/rear gunner was placed behind him. This arrangement provided easier crew communication.

The Yak-2 had a crew of two, with the pilot placed to the front and the navigator/machine gunner to the rear. Source: Pinterest

The armament of this aircraft consisted of two rear positioned 7.62 mm (0.3 in) machine guns. These were placed in a small cupola that could be raised higher up to provide better covering fire. There was a provision for an internal bombing bay that could hold 400 kg (880 lbs) of bombs. In addition, the aircraft could carry up to 100 kg (210 lbs) bombs in external bomb racks

In combat

Despite its obvious mechanical unreliability, the Yak-2 would be allocated for operational service. The first group of 25 aircraft were initially allocated to the Kharkov Military District. Due to many mechanical problems, they could not be used for flying. Even at this time, there were still attempts to somehow improve the Yak-2’s overall performance, with minimal results. When the aircraft was fully equipped with military equipment, such as radio, weapons, and full fuel load, the flight performance dropped dramatically. For example, the maximum speed was reduced to 399 km/h (247 mph). In addition, the Yak-2 struggled to reach heights of 8,100 m (26,500 ft), which were some 2,800 m (8.800 ft) lower than those reached during prototype testing.

When the war with the Germans broke out, some 75 Yak-2s were allocated to the 136th Bomber Regiment located in Kiev and the 316th Reconnaissance Regiment in the western district. Their use was quite limited, as most were destroyed on the ground by the German Air Force. At least one was shot down by friendly aircraft fighters.

 

The majority of Yak-2s were destroyed on the ground by the German Air bomb raids. Source Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev, Midland
Some did survive the initial German Air raids but would be lost in the following weeks. Here, a group of three Yak-2s on their way to bomb German positions can be seen. Source: Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev, Midland

Proposed versions

Despite its generally poor performance of the Yak-2, there were some attempts to reuse this aircraft for other purposes. These included the BPB-22 short-range bomber, R-12 reconnaissance, I-29 escort fighter, Yak-2KABB ground attack aircraft, and a trainer version.

The BPB-22

The GAZ. No.81 production plant, on its own initiative, tried to develop a short-range dive bomber based on the BB-22. For this proposal, they equipped one aircraft with the newly developed M-105 engines and added dive brakes. The first flight test made in October 1940 was disappointing and the project was canceled.

R-12 reconnaissance

Based on elements from No-22 and the Yak-2, a reconnaissance aircraft named R-12 was to be developed. This aircraft was to be powered by 960 hp M-103 engines. In the end, nothing came of this project.

Yak-2KABB

This was a ground attack prototype equipped with bombs, two 20 mm (0.78 in) cannons, and two machine guns placed under the fuselage. It also received a new modified cockpit design. The aircraft was tested in a series of evaluation flights and was generally considered to be a good design. The outbreak of the war stopped any further work on this aircraft.

The experimental Yak-2KABB. Source: Y. Gordon, D, Khazanov and S. Komissarov OKB Yakovlev, Midland

I-29

The I-29 was a heavy escort fighter that was to be armed with two 20 mm (0.78 in) cannons. While work on this aircraft continued up to 1942, it would ultimately be canceled.

A trainer version

One Yak-2 was built as a dual-control trainer aircraft. While it was tested in March 1941, nothing came from this project. It is not known if this version ever received any official designation.

Production

Being an unsuccessful design, the actual production run was limited. The Yak-2 was produced by the GAZ No.1 production plant, which built around 25 aircraft. The Moscow Aircraft factory No.81 produced some 75 Yak-2s which were slightly improved in quality but, otherwise, were the same. By the time production ended, only around 100 aircraft were built.

  • No-22/BB-22 Prototype – The first prototype built during the summer of 1939, which served as a base for the Yak-2
  • Yak-2 – Main production version
  • Yak-2KABB – A ground attack prototype
  • BPB-22 – Short-range bomber, one prototype built
  • R-12 – Reconnaissance version proposal
  • I-12 – Escort fighter proposal
  • Trainer Aircraft – One prototype of a dual-control trainer version was built but was not accepted for service

Conclusion

While it managed to achieve extraordinary speed during the prototype phase, in the military role, the Yak-2 proved to be a disappointing design. Once it was fitted with armament and other equipment, its performance dropped dramatically. This, together with other design problems, ultimately led to the cancelation of this project after only 100 built aircraft.

Specifications –  Yak-2 Specifications
Wingspan 45 ft 11 in / 14 m
Length 30 ft 7 in / 14 m
Wing Area 316.4 ft² / 29.4 m²
Engine Two M-103 960 hp engines
Empty Weight 9,390 lb / 4,260 kg
Maximum Takeoff Weight 12,410 lb / 5,630 kg
Fuel Capacity 600 liters
Maximum Speed 310 mph / 500 km/h
Cruising Speed 255 mph / 410 km/h
Range 560 mi / 900 km
Maximum Service Ceiling 28,545 ft / 8,700 m
Crew One pilot and one navigator/gunner
Armament
  • Two 7.92 mm (0.3 in) machine guns
  • 400 to 500 kg (880 to 1100 lbs) bombs

Gallery

Yak-2 (BB-22) – 316th RAP Lt.I.M.Agarkov. South-West Front – July-August 1941
Illustration by Ed Jackson

 

  • D. Nešić (2008), Naoružanje Drugog Svetskog Rata SSSR, Beograd.
  • B. Gunston and Y. Gordon (1977)Yakovlev Aircraft Since 1924, Putnam Aeronautical Books.
  • Y. Gordon, D, Khazanov (1999) Soviet Combat Aircraft, Midland Publishing.
  • Y. Gordon, D, Khazanov, and S. Komissarov (2005) OKB Yakovlev, Midland.

Junkers Ju 87A Stuka

Weimar and Nazi Germany, WW2, , , ,

Nazi flag Nazi Germany (1934)
Dive-bomber – 262-400 Built

The Ju 87A [warbirdphotographs.com]
Prior to the Second World War, the Germans were experimenting with how to increase the accuracy of air bombing attacks. One solution was to use dive attacks, which greatly increased the chance of hitting the desired targets. By the mid-30s, a number of German aircraft manufacturing companies were experimenting with planes that could fulfill these dive bomb attacks. The Junkers Ju 87 proved to be the most promising design and would be adopted for service.  The Ju 87 would become one of most iconic aircraft of the Second World War, being feared for its precise strikes, but also for its unique use of sirens for psychological warfare.

History

After the First World War, the Germans began experimenting with ideas on how to make aircraft more precise during ground attack operations. The use of conventional bombers that dispatched their payload from straight and level flight could effectively engage larger targets, such as urban centers, industrial facilities, infrastructure, etc. This method was less effective for destroying smaller targets, like bunkers or bridges. A dive-attack, on the other hand, provided a greater chance of hitting smaller targets and, to some extent, reduced the chance of being shot down by ground based enemy anti-aircraft fire. This concept of dive-attack aircraft would be studied and tested in detail by the Germans during the 1930s. These aircraft would be known as Sturzkampfbomber (dive-bomber), but generally known as Stukas. 

The development of such aircraft was greatly hindered by the prohibitions imposed by the Treaty of Versailles. To overcome this, some German companies simply opened smaller subsidiaries in other countries. In the case of the Junkers, a subsidiary company known as Flygindustri was opened in Sweden. There, they developed a K 47 two-seater fighter in 1929. It was tested for the role of dive-bomber and proved successful. But its price was too high for the German Luftwaffe to accept, so it was rejected.

The Junkers K 47 was a two-seater fighter from 1929. While showing to possess good dive-attack characteristics, due to its price, it was not adopted for service. [Wiki]
As a temporary solution, the Germans adopted the He 50 in 1932. The following year, a more comprehensive test of the dive-bombing concept was undertaken at airbase Juterbog-Damm. During these trials, Ju-52 bombers were used. The overall results were disappointing, thus development of a completely new dedicated design was prioritized by the Germans. For this, Luftwaffe officials placed an order with all aircraft manufacturers to present their models for the dive-bomber competition.

In late 1933, the Junkers dive-bomber development project was carried out by engineer Herman Pohlmann. He stressed the importance of an  overall robust aircraft design in order to be able to withstand steep diving maneuvers. Additionally, it should have had fixed landing gear and be built using all-metal construction. 

The next year, a fully completed wooden mock-up with inverted gull wings and twin tail fins was built by Junkers. Officials from the German Aviation Ministry (Reichsluftfahrtministerium RLM) inspected the mock-up during late 1934, but they were not impressed and didn’t place a production order. Despite this, Junkers continued working on the project. Junkers soon began construction of a full scale prototype. Due to many delays with the design, construction of the project dragged into October 1935. The first prototype received the Ju 87 V1 designation, bearing serial number 4921. Somewhat surprisingly, it was powered by a 640 hp Rolls-Royce Kestrel 12 cylinder engine. The first test flight was completed in September 1935 by test pilot Willi Neuenhofen. While the first flight was generally successful, the use of a foreign engine was deemed unsatisfactory and it was requested that a domestic built engine be used instead.  The V1 prototype would be lost in an accident when one of the twin tail fins broke off during a dive test near Dresden. Both the pilot Willi Neuenhofen and the second passenger, engineer Heinrich Kreft, lost their lives. The examination of the wreckage showed that the fin design was too weak and thus had to be replaced with a simple conventional tail fin. 

The V1 prototype could be easily identified by its twin tail fin design. [warbirdphotographs.com]
Ju 87 V2 (serial number 4922 and with tail code  D-UHUH (later changed to D-IDQR) was built with the 610 hp Jumo 210 A engine and had a redesigned tail fin. Another addition was the installation of special slats that could be rotated at 90° forward, perpendicular to the underside of the wing, acting as dive brakes. The V2 also received a specially designed bomb release mechanism, meant to avoid accidentally hitting the lowered radiator and the propeller. When the pilot activated the bomb release during a dive, the specially designed cradle would simply swing forward. In essence, this catapulted the bomb safely away from the plane while still maintaining its trajectory toward the target. There were a number of delays with the redesign of the airframe, which led to V2’s first flight being made during late February 1936. While the test flight was successful, the Luftwaffe officials showed some reluctance with regards to the project, given the fate of the first prototype. Nevertheless, the Ju 87, together with the He 118, Ha 137 and Ar 81, were used in a dive-bomber competition. The initial results favored the Heinkel, but when the He 118 was lost during one of its  test flights together with the engine problems, the RLM proclaimed the Ju 87 as the winner.

The unsuccessful He 118 aircraft. [Wiki]
The Ju 87 V2 prototype. [warbirdphotographs.com]
Winning the competition for the new dive-bomber design, Junkers was instructed to build more prototypes to improve the overall performance of the Ju 87. The V3 (serial number 4923 and designation D-UKYQ) received a number of modifications. It had an enlarged tailfin, added counterweights on the elevators, a modified landing gear, and a redesigned engine cowl to improve forward visibility. The first test flight was made in March of 1936. 

The V4 (serial number 4924 and with D-UBIP) was further modified by once again increasing the size of the tailfin, adding forward firing machine guns, a rear defensive machine gun, and again redesigning the front engine compartment. It was powered by the Jumo 210 Aa engine. It was flight tested for the first time in June 1936. During its test flight, the maximum cruising speed achieved was 250 km/h (155 mph). The RLM would become increasingly concerned about the Ju 87 design, as this cruising speed was the same as that of the older He 50. Despite this, the handling and resilience of the whole airframe were deemed satisfactory. The V4 prototype would later serve as the base for the A-0 pre-production series. The last prototype, V5 (serial number 4925), was built in May 1936. It was built to test the installation of the DB 600 and Jumo 210 engines. 

The V4 prototype, which served as base of the A-0 pre-production series. In addition, it was the first Ju 87 aircraft to see real combat action during the Spanish Civil War. [warbirdphotographs.com]

The Ju 87 ‘Anton’ Introduction

Following the success of the prototype series, the RLM officials issued orders for more Ju 87 aircraft. This would lead to a small production run of between 7 to 10 aircraft of the Ju 87A-0 pre-series aircraft (A for Anton, according to the German phonetic alphabet). While the first A-0 aircraft were to be built starting in November 1935, due to a number of delays, the actual production began in the spring of 1936. Following a series of tests conducted on the A-0 aircraft at the end of 1936, it was determined that these planes, equipped with the Jumo 210 Aa engine, were underpowered. A number of the A-0 aircraft would receive a new 680 hp Jumo 210 D engine as an upgrade. The A-0’s rear fuselage was also lowered to provide the rear gunner with a better firing arc. For the radio equipment, two ‘V’ shaped antennas were placed around the cockpit. 

Further development led to the Ju 87A-1, which was powered by the Jumo 210 D as standard. The A-1 series was able to carry one 250 kg (550 lbs) bomb in its standard two man crew configuration. Alternatively, it could carry one 500 kg (1100 lbs) bomb but, in this case, the rear machine gunner had to be left behind. 

The last version of the series was the Ju 87A-2. It was slightly improved by adding better radio equipment. In addition, the engine performance was improved, along with a new two-stage compressor, and a new propeller.

Technical Characteristics 

The Ju 87A was designed as a single-engined, twin-seat all metal dive bomber. Its fuselage was built by connecting two oval-shaped sections with a simple structure design. The longerons consisted of long shaped strips which spanned across the longitudinal direction of the aircraft. These had a ‘U’ shape which was connected to the duralumin skin by rivets. 

For construction of the Ju 87’s wings, Junkers engineers employed the doppelüger (a double wing construction). This meant that the full-span ailerons were hinged near the trailing edge of the wings. Another feature of the wings was that they had an inverted gull design. This was done intentionally by the Junkers engineers in an attempt to provide the crew members with the best possible all around visibility. The Ju 87 fuselage and wings were covered with a combination of duralumin and magnesium alloy sheeting. While the V1 prototype was equipped with twin tail fins, the A-series was equipped with a more orthodox tail design. The tailplanes had a rectangular shape, while the rudder had a square shape.

Rear view of the Ju 87A [asisbiz.com]
The landing gear was fixed. It consisted of two larger front wheels, with one smaller tailwheel to the rear. The front landing gear and wheels were covered in large protective fairings, sometimes known as “spats.” This arrangement would prove to be problematic, and would later be replaced with a much simpler design.

The Ju 87 had a distinguishable fixed landing gear, protected by a larger housing. This design would be simplified in later version. [asisbiz.com]
The Ju 87 engine was mounted specifically to provide easy access for replacement or maintenance. It was powered by an inline Jumo 210 D water cooled engine, with a variable pitch propeller with a 3.3 m diameter. The fuel capacity was 480 liters, placed in two tanks. The fuel tanks were located in the center part of the curved wings. 

The Ju 87 had a large cockpit where the pilot and the rear gunner were positioned in a back-to-back configuration. The center of the canopy assembly was reinforced by a durable section of cast magnesium, meant to provide better structural integrity. The cockpit was also protected with a fire-resistant asbestos firewall. On the A-series, the pilot was responsible for operating the radio equipment. This task would be allocated to the rear gunner in later versions. The radio equipment consisted of a FuG VII radio receiver and transmitter. 

The Ju 87A-1 was armed with one forward mounted 7.92 mm MG 17 and a rear positioned MG 15, also firing 7.92 mm, fitted on a flexible mount. The offensive armament consisted of either a 250 kg or 500 kg bomb (550 to 1100 lbs). When the larger bomb was used, the rear crew member had to be left behind. A small number of aircraft were equipped with bomb racks for four 50 kg (110 lbs)  mounted under the wings. These were actually used for training purposes, as the bombs were actually made of concrete. 

Diving Operation

The Ju 87 pilot would commence the dive-bombing run once the target was identified. The target would be located through a bombsight which was placed in the cockpit floor. The attack would usually be carried out from an altitude of less than 4,600 meters. The aircraft would then be rolled around by the pilot until it was upside down. The Ju 87 would then engage its target at an angle of attack of 60 to 90°, with a speed of 500 to 600 km/h (310-370 mph). During these dive-bombing runs, there was a chance the pilot could  temporarily lose consciousness due to extensive G-forces. If the pilot was unable to pull up, a ground collision was a strong possibility. To avoid this, the Ju 87 was equipped with automatic dive brakes that would simply level out the plane at a safe altitude. Once the plane reached a level flight, the brakes would then disengage. The Ju 87 was also equipped with warning lights that informed the pilot when it was time to release the bomb. 

Germans conducted extensive research to determine how much G-force a pilot could endure without any medical problems. The testing revealed that the pilot could overcome a 4G force without problems. At 5G , the pilot would experience blurred vision. The maximum G-forces were noted to be 8.5 G but only for three seconds. Any more could lead to extensive injuries or even death. 

Illustration of a Ju 87 dive-attack run. Source Pinterest

Organization

The Ju 87 were used to equip the so-called Sturzkampfgeschwader or simply StG (dive-bomber flight unit). The StG was divided into three Gruppen (groups). Each of these groups was further divided into three Staffel (squadrons).  

In Combat

The Ju 87 saw its first combat action during the Spanish Civil War that lasted from 1936 to 1939. The Germans saw this war as the perfect place to test their new aircraft designs. For this reason, one V4 prototype was secretly disassembled and transported on a passenger ship to Spain in August 1936. It was part of the experimental unit (Versuchskommando) VK/88 (or VJ/88, depending on the source) of the Condor Legion. The overall performance or even the use of this aircraft is generally unknown. During this conflict, it received the designation 29-1. It may have taken part in the Battle of Bilbao  in June of 1937, after which it was shipped back to Germany. 

In early 1938, three more aircraft of the A-1 series were shipped to Spain. These received the 29-2, 29-3, and 29-4 designations. They were given to the 1st Staffel of Sturzkampfgeschwader  162 (dive bomber wing).  While only three aircraft were used by this unit  their original designations were often replaced with higher numbers in an atempt to decive the enemy.  The initial pilots of these aircraft were Ernst Bartels, Hermann Hass, and Gerhard Weyert. The Germans would replace them with new crew members after some time, in the hope of increasing the number of pilots with experience operating the aircraft under combat situations. 

Their initial base of operations was an airfield near Zaragoza, Spain. There were some problems with the forward landing gear covers, which would dig into the ground on the sandy soil of the airfield. To resolve this issue, the crews simply removed them. The use of a larger 500 kg bomb required the removal of the rear gunner, so the smaller 250 kg bomb load was more frequently used.

In March 1938,, the three Ju 87s attempted to attack retreating Spanish Republican units at the Aragon with somewhat limited success. The attacks were less successful, mainly due to the inexperience of the pilots. From July 1938 on, the Ju 87 showed more promising performance during the Spanish Republican failed counterattack at the Ebro River and Mequinenza. By October, all three Ju 87 As were shipped back to Germany. 

A Ju 87A during the Spanish Civil War [Wiki]
The overall performance of the A-series was deemed insufficient for combat operations early on. This, together with the fact that the improved Ju 87B version was becoming available in increasing numbers, leading to a withdrawal of the A version from service. These would be reallocated to training units, and would be used in this role up to 1944. 

The Ju 87A would see only limited combat service, being mostly allocated to training units [warbirdphotographs.com]

In Hungarian Service 

During the war the Germans provided their Hungarian ally with four Ju 87A aircraft. These were used mostly for crew training in later stages of the war. 

Hungarian Ju 87A [Hungarian Air Forces 1920-1945]

Production and Modifications

Production of the Ju 87 ended by the summer of 1938. By that time, some 262 were built by the Junkers factories located in Dessau (192) and Bremen (70). These numbers are according to M. Griehl (Junkers Ju 87 Stuka). Author D. Nešić (Naoružanje Drugog Svetsko Rata-Nemačka), on the other hand, notes a number of 400 aircraft being built. 

The main versions were:

  • Ju 87 Prototype series – Five prototypes were built and used mostly for testing. 
  • Ju 87A-0 – A small pre-production series.
  • Ju 87A-1 – Main production version.
  • Ju 87A-2 – Slightly improved A-1 aircraft.

Conclusion

While the Ju 87A fulfilled the role of dive-bomber well, it was shown to be inadequately developed to meet military requirements. For this reason, it was mainly issued for crew training. Its main success was that it provided the German with an excellent base for improvement and development of further aircraft. It also provided the German pilots with valuable experience in such dive-bombing flights.

Ju 87A-1  Specifications
Wingspans 45 ft 3 in / 13.8 m
Length 35 ft 4 in / 10.78 m
Height 12 ft 9  in  /  3.9 m
Wing Area 104 ft² /  31.9 m²
Engine Junkers Jumo 210D 680 hp engine
Empty Weight 5,070 lbs / 2,300 kg
Maximum Takeoff Weight 7,500 lbs / 3,400 kg
Fuel Capacity 480 liters / 127 US gallons            
Maximum Speed  200 mph / 320 km/h
Cruising speed 170 mph  / 275 km/h
Range 620 miles / 1,000 km
Maximum Service Ceiling 22,970 ft / 7,000 m
Crew One pilot and the Rear Gunner
Armament
  • One forward mounted 7.92 mm MG17 and one 7.92 mm MG15 positioned to the rear
  • One 550 lb (250 kg) bomb for two-seaster
  • Or one  1100 lb (500 kg) bomb in the single-seater configuration. 

Gallery

Illustrations by Carpaticus

Ju 87A with an unusual winter camouflage
Ju 87A-1 from the Dive bomber school 1, operated during winter 1940-1941
Ju 87A used for pilot training in late 1939
Ju 87 A-1 1st Staffel of Sturzkampfgeschwader 162 during the Spanish Civil War

Credits

  • Article by Marko P.
  • Edited by Stan L. & Ed J.
  • Illustrations by David Bocquelet & Carpaticus
  • M. Griehl (2006) Junkers Ju 87 ‘Stuka’, AirDOC.
  • M. Guardia (2014) Junkers ju 87 Stuka, Osprey Publishing 
  • D. Nešić (2008). Naoružanje Drugog Svetsko Rata-Nemačka. Tampoprint S.C.G. Beograd.
  • D. Monday. (2006). The Hamlyn Concise Guide To Axis Aircraft OF World War II, Bounty Books.
  • Z. Bašić (2018) Građanski Rat U španiji 1936-1939, Čigoja Štampa. 
  • G. Sarhidai, H. Punka and V. Kozlik. (1996) Hungarian Air Forces 1920-1945, Hikoki Publisher  

 

 

Blohm und Voss Bv 141

Weimar and Nazi Germany, WW2, , ,

Nazi flag Nazi Germany (1938)
Tactical Reconnaissance Aircraft – 13-18 Built

The Second Bv 141 Prototype (V1) – Colorized by Michael Jucan

During the Second World War, the Germans would design and build a number of unusual aircraft (the Me 163 or the He 111 Zwilling, for example), but none was so unorthodox and strange as the Bv 141. In order to provide good visibility for its reconnaissance role, the crew gondola was completely separated from the aircraft’s fuselage. While small numbers were built, during testing it was shown to have decent flying characteristics for its completely unconventional design.

History 

In 1937, the German Ministry of Aviation (Reichsluftfahrtministerium RLM) issued a request to all German aircraft manufacturers for a new single-engine reconnaissance aircraft with provision for three crew members. Great attention was to be dedicated to having a good all-around visibility. In addition, the aircraft would also have to be able to act as a light attack, and smokescreen laying aircraft. Three aircraft manufacturers responded to this request, Arado, Focke Wulf, and Blohm und Voss. Of these, Blohm & Voss would submit the most distinctive design to say at least. 

While at first glance, the Ha 141 (as it was known at the start of the project, with the ‘Ha’ designation stands for Hamburger Flugzeugbau) appears to be created by someone with no experience whatsoever in aircraft design. This was not actually the case. In reality, the Ha 141 was designed by Dr. Ing. Richard Vogt, who was Chief Designer at Blohm und Voss for the new reconnaissance aircraft. The Ha 141 was to have an unusual design, as the crew was put into a well-glazed gondola, with the fuselage with and engine to the left. During his initial calculations, Dr. Vogt predicted, successfully, that the large crew gondola would act as a counterbalance to the long left-side engine fuselage.  

When Dr. Ing. Richard Vogt presented his plans to the Ministry of Aviation, the officials were quite uninterested in such an unorthodox design, and the story of the Ha 141 would have ended there. Not willing to give up on his idea so easily, the Blohm und Voss company financed the construction of the first prototype with its own funding. The prototype was completed early in 1938  and the name was changed to Bv 141. It made its maiden flight on the 25th of February that year. The flight went well, without any major problems. The only issue was a slight oscillation of the landing gear. When it was presented to the Luftwaffe officials, they were surprised by its performance and ordered a production run of three more prototypes. Interestingly, after some negotiations with Blohm & Voss, their prototype was included in this order and two more aircraft were actually built. The first prototype was marked as V0 and would be later rebuilt into the Bv 141 V2 prototype and tested with the BMW 139F engine.  The Luftwaffe officials only requested that the crew gondola be completely redesigned, internally and externally, to incorporate a larger working space, and to be almost completely glazed, quite similar in design to the Fw 189. Bv 141 V1, actually the second produced aircraft, was used to test the aircraft’s general flight performance. The V3 made its first test flight on 5th October 1938 and was used mainly to test the BMW 132N engine. 

After the first prototype was shown to the Luftwaffe officials order few more to be built for future testing [luftwaffephotos.com]
By 1939, an additional two more aircraft were built. The V4, that was to be sent to the Erprobungstelle Testing Center at Rechlin, had an accident during landing. After the repairs were made, it was finally flight tested at Rechlin. It performed well and it was liked by the pilots that had the chance to fly it. It also underwent a number of different weapon tests. Once all these tests were completed, the V4 prototype was chosen for modification into the first A-series. After that, a small series of the A version, five aircraft in total, were built and used mostly for testing and development of new improvements at Rechlin. Some were stationed at Aufklärungsschule 1 (Training School 1) at Großenhain. While the A-2 would be rebuilt into a training airframe in May 1942, the fate of the remaining aircraft of this series is unknown. Likely, all were scrapped. Depending on the sources the A-series aircraft were powered by a 1,000 hp BMW Bramo 323 radial engine.

A rear view of the Bv 141 V4 prototype. [luftwaffephotos.com]
Following these tests, the Bv 141 received positive reports about its overall performance. There were also discussions about its mass production. Despite this, the whole project was officially canceled on 4th April 1940. The main reason was the Luftwaffe high officials’ distrust of the design. The official reason for rejection of the Bv 141 was noted as ‘underpowered,’ despite its good performance.

Technical Characteristics

The Bv 141 was a uniquely designed single-engine all-metal aircraft. It did not have a standard fuselage, with the engine in the front and the crew behind it.  The crew gondola and the fuselage with the engine were completely separate from each other. Both were located slightly off the center of the wings. The crew gondola was placed on the right, with the engine to the left.

The glazed crew gondola is quite visible here [luftwaffephotos.com]
The first A-series aircraft had a wingspan of 15 m (49 ft 3 in). The Bv 141 was initially powered by a 865 hp BMW 132N 9-cylinder radial engine. It used a constant speed propeller. Behind the engine, the 490 l fuel tank was placed. 

Close up view of the initially used 865 km/h BMW 132N engine. While weaker than the later engine used, its performance was much better and offered a much more pleasant flight. [luftwaffephotos.com]
The tail design was changed during the Bv 141’s development. Initially, a standard tail design was used. This would later be replaced with a forward leaning, asymmetric tailplane, offset to port side. The unusual shape of the new tailplane had the intent of providing the rear gunner with the best available firing arc. It only had one elevator, which had a larger surface area than the previous model. Surprisingly, the aircraft’s good performance was left unchanged after the introduction of the asymmetric tailplane. 

The landing gear was more or less standard for its time. The front landing gear consisted of two large wheels that retracted outwards into the leading edges of the wings. To the rear, there was a small landing wheel that retracted to the back and slightly protruded out of the fuselage.

The landing gear on the Bv 141 were standard type at the time, consisting of two forward landing wheels and one smaller to the rear [luftwaffephotos.com]
The first crew gondola had fewer glazed surfaces than the later used models. In general, it provided the crew with excellent front, rear, and right-side views of the surroundings. The left view was partly obscured because of the engine.

The Bv 141 pilot front gondola interior [luftwaffephotos.com]
The armament consisted of four 7.92 mm machine guns. Two MG 17 forward firing fixed machine guns were placed in the forward nacelle. These were operated by the pilot, who used a Revi aim sight. To the rear, one defensive MG 15 was placed in a small circular cupola atop of the Bv 141. The last MG 15 was positioned to the rear of the aircraft. The Bv 141 could also carry four 50 kg (110 lb) bombs. 

The pilot was positioned on the left side of the englazed nose of the gondola.  Next to him  was the position of the observer, who also acted as bombardier in case the Bv 141 was used for ground attack. The observer also had the job of operating the radio and the machine gun placed in the small circular cupola. Interestingly, because he performed different tasks, his seat was connected to two tracks which enabled him to move freely inside the gondola without getting up. The third crew member operated the rear defensive machine gun. 

The Bv 141 pilot had a large glazed gondola where the crew was positioned. It offered a good all round view (except to the right side where the engine was). [luftwaffephotos.com]
The front view of the first Bv 141 prototype built by Blohm und Voss. [luftwaffephotos.com]

Last Hope for Production

With the cancelation of the Bv 141A series due to allegedly poor engine performance, Dr. Ing. Richard Vogt immediately began working on an improved version. In order to address the concerns made  by the Luftwaffe regarding its engine, the Blohm & Voss designers decided to use the stronger 1,560 hp BMW 801A 14-cylinder two-row engine. Unbeknownst to them, this decision would actually doom the whole project. 

With the new engine, other changes to the overall design had to be made. The wings had to be reinforced and their span increased to 17.46 m (57 ft 3 in). In addition, the leading and trailing edges had to be redesigned. The rear part of the fuselage’s design was also changed. The landing gear was also improved by adding much stronger landing gear wheels. The armament appears to have been reduced to three machine guns (the sources are not clear here), while the bomb load remained the same.

The top view of one of few built Bv 141B series. While intended to improve the Bv 141A series performance, it was never achieved successfully. [luftwaffephotos]
All these changes would lead to the development of the Bv 141B series. The first mock-up was completed in February 1940. The first test flight was made on the 9th January 1941. This time, the Luftwaffe officials showed interest in it, especially after installing the much stronger engine. While Blohm & Voss received permission to build five aircraft of the B-series, the order was increased by five more. Initial calculations showed that it could reach speeds up to 480 km/h (300 mph), at least in theory. Almost immediately, the Bv 141B aircraft proved to be plagued with many problems. The controls were difficult to use and the plane was prone to mechanical faults, especially regarding the landing gear and the hydraulic systems. A huge issue was also created by the strong vibrations that occurred during the test flights. In addition, during firing trials, it was noted that cordite fumes would accumulate in the cockpit from the guns.

The Luftwaffe’s initial enthusiasm for this unusual aircraft quickly faded away. While the tests on the Bv 141 would go on for a few more years, the Fw 189 would be chosen instead. Despite this setback, Dr. Vogt would continue on working on similar and improved designs during the war. Due to urgent requests for more ‘normal’ planes, he was ultimately forced to abandon his work and, besides some proposals, he never got a chance to build another such aircraft during the war. The last mention of the Bv 141 B-10 was in May of 1944, when it was used to tow another unusual design from Blohm and Voss, the experimental Bv 40 armed glider. 

A group of three Bv 141 aircraft during one of many test flights [luftwaffephotos]

Operational Use

The Blohm und Voss Bv 141 [luftwaffephotos.com]
The second BV 141B prototype was allocated to Aufklärungsschule 1 (Reconnaissance Training Unit) in 1941, stationed at Grossenhain. It appears that its performance was deemed satisfactory, as more aircraft were requested in order to form at least one operational test unit for use on the Eastern Front. This was never implemented, mostly due to two reasons. The Blohm und Voss factories were redirected to higher priority projects, and since the  Fw 189 was accepted for service, there was no real need for another reconnaissance aircraft.

Some sources, like the book Aircraft of World War II by C. Chant, mention that it was used in test flights over the UK and the Soviet Union during its short operational service.

Use After the War

The fate of the small number of Bv 141s produced is not known. While the majority were scrapped, some managed to survive until war’s end. One Bv 141 was actually captured by the Soviet Forces near the end of the war. This aircraft would be flight tested by the British pilot Captain Eric Brown. He was the chief test pilot of the Royal Aircraft Establishment at Farnborough. He was involved in a British project tasked with taking over German war research installations and interrogating technical personnel after the war. 

The single Bv 141 was relocated to an auxiliary airfield near the town of Meissen. When Captain Brown arrived, Soviet soldiers were already taking anything that was of use from the airfield and destroying everything else. After making a request to the Soviets to see if the aircraft could be flown, the Soviets approved. He was instructed to conduct a short flight around the airfield, and to beware of possible engine malfunctions due to the general poor state of the aircraft.  

Captain Eric Brown described the flight with the Bv 141 as follows. “With the flaps set to start, there was surprisingly little take-off swing, although I had expected rather a lot. The run was short, but I found the undercarriage took a long time to retract, although I suspected the hydraulics were sluggish after a long period of disuse.

The climb was mediocre at a speed of 189 km/h (112 mph) and, remembering my Russian instructions, I did not go above about 915 m (3,000 ft). Cruising speed at that height was 325 km/h (202 mph). It was at this speed that I decided to try out the theory behind the asymmetric layout of the 141, namely that in the event of attack, the aircraft could be stood on its wing tip and held there in straight flight, thus giving the gunner in the cone of the nacelles a tremendous field of fire. 

Frankly, I was sceptical of this claim of edge-on straight flight, but it proved to be, as near as damn it, true. I then stepped up the power, increasing the speed to 360 km/h (224 mph), but just as I rolled the aircraft on to its port side, the engine suddenly backfired heavily and oil pressure began to drop. This terminated any short handling session, as I considered discretion better than providing the Russians with their eagerly awaited spectacle. 

I therefore turned straight into the landing pattern with the engine throttled well back, and lowered the undercarriage immediately at about 610 m (2,000 ft) to give it time to lower in case it got temperamental. I had both flaps and the undercarriage lowered by about 305 m (1,000 ft), across wind of the final approach, turning on to finals at 150 m (490 ft) at 145 km/h (90 mph) and easing the speed off to 130 km/h (80 mph) over the airfield boundary. 

I stopped the engine at the end of the landing run, as it was obviously very sick. …. In retrospect, I am really glad to have had the unique opportunity of even a short flight in the Bv 141B, because it left me with the realisation that it was not as bad an aircraft as its development history seemed to suggest. It had good, effective controls, although it had poor lateral stability, which would have made it unpleasant to fly in turbulence at low level. Maybe this and the fact that its competitor, the Fw 189, had excellent flying characteristics, were the real reasons for its demise before reaching operational production.  “

Allegedly, according to some internet sources, at least one Bv 141 was captured by the British forces. It was then shipped to England for evaluation, but its fate is unknown. 

Production

How many Bv 141s were produced is not clear in the sources. The number ranges from 13 to 18 aircraft being built. This includes at least three prototypes, five of the slightly improved A series and some 10 B series aircraft. The last Bv 141B was delivered in mid-May 1943.

  • Ha 141 Prototype – The first prototype was built as a Blohm & Voss private venture.
  • BV 141A –  Slightly improved version.
  • BV 141B – Powered by a much stronger engine and with many other modifications, especially to the wing design.  

Operators

  • Germany – A few aircraft were used experimentally by the Luftwaffe.
  • Soviet Union – After the War, the Soviets managed to capture one Bv 141B, but its fate is unknown.
  • United Kingdom – Possibly captured one, which was allegedly shipped to England for evaluation.

Conclusion

The BV 141 initially demonstrated generally good flight characteristics, despite its unusual and radical design. The desire to further improve the flight performance, and distrust by the Luftwaffe eventually killed the project. The extensive redesign of the Bv 141B series simply had too many problems that were never completely resolved. The Luftwaffe was also reluctant to invest more time in it, especially as the more orthodox Fw 189 was being introduced into service. In the end, while it was not put into production, the BV 141 was nevertheless an interesting design and certainly deserves a spot in aviation history.

Bv 141B Specifications
Wingspans 57  ft 3  in / 17.56  m
Length 45  ft 9 in / 13.9 m
Height 11 ft 9 in  / 3.6  m
Wing Area 570 ft² / 52.9 m²
Engine One BMW 801 A-0 1.560 HP 14 cylinder radial engine
Empty Weight 10,360  lbs / 4,700 kg
Maximum Takeoff Weight 13,450 lbs / 6,100 kg
Fuel Capacity 470 l
Climb Rate to 6 km In 8 minute 48 second
Maximum Speed at 5.000 m 272 mph / 438 km/h
Cruising speed 250 mph  / 400km/h
Range 745  miles / 1,200 km
Maximum Service Ceiling 32,810 ft / 10,000 m
Crew Pilot, observer and the rear gunner. 
Armament
  • Two forward fixed 0.3 in (7.92 mm) machine guns and one same caliber machine gun placed to the rear.
  • Up to four 110 lb (50 kg) bombs

Gallery

Illustrations by Ed Jackson

Bv 141 V2 – The 1st Prototype
Bv 141B – The first B Series Prototype
Bv 141B V-11
Bv 141B V-18 with 50kg Bomb Mounted
Bv 141B Overhead View

Credits

  • D. Nešić (2008), Naoružanje Drugog Svetskog Rata Nemačka Beograd
  • B.Eric (1977/2010) Wings Of The Luftwaffe Flying The Captured German Aircraft of World War II, Hikoki Publications.
  • C. Chant (2007) Pocket Guide Aircraft Of World War II, Grange Books. 
  • M. Griehl (2012) X-Planes German Luftwaffe Prototypes 1930-1945, Frontline Book.
  • Jean-Denis G.G. Lepage Aircraft Of The Luftwaffe 1935-1945, McFarland and Company.
  • D. Donald (1994) Warplanes Of The Luftwaffe, Barnes and Noble. 

Fizir Prelazni FP-2

WW2, Yugoslavia, , , , ,

Yugoslavia flag Yugoslavia (1933-1947)
Training aircraft – 81 Built

Front view of the FP-2. [vazduhoplovnetradicijesrbije.rs]
The FP-2 was designed as an advanced two seater biplane trainer for the Yugoslav Royal Air Force in late 30s. It would be used to equip pilot training schools for some years before WW2. During World War II, it would be used by the Axis powers, which managed to capture a number of them, for limited ground attack operations. The FP-2 would survive the war in smaller numbers and remain in use up to 1947.

History

As the Yugoslav Royal Air Force began to develop and acquire more modern types of aircraft, the need for advanced training aircraft became apparent. Due to the obsolescence of older trainers, the Yugoslav Royal Air Force Command issued orders to begin developing a new series of advanced trainers in 1933. One of the designs submitted was the Fizir FP-1 biplane made by Zmaj. Despite its disappointing overall performance, a new design was desperately needed. At the same time, a design team composed of Rudolf Fizir and Dušan Stankov began working on a new model named FP-2. In a later address to Zmaj management in May of 1940, Dušan Stankov wrote that he was responsible for the design of the FP-2, with little to no input from Rudolf Fizir. While the Royal Air Force command was more in favor of a monoplane design, the FP-2 nevertheless received a green light.

Name

The capital letters in the name FP-2 are an abbreviation for “Fizir Prelazni 2” (Физир Прелазни ФП-2). Depending on the source, it is also sometimes identified as F.P.2. During its operational service in the Yugoslav Royal Air Force, it was also known as F.P.2-K7 after its engine name, or Fizir-Stankov F.P.2 after its designers. This article will use the FP-2 designation, as it is best known today.

What is interesting is that the FP-2 name may suggest that it was an improved version of the earlier FP-1. In reality, these two projects had nothing in common. This name was done mainly for administrative reasons, in order to obtain the funds allocated for FP-1.

Work on the Prototype

Work on the first prototype began in early 1933. At this time, the Yugoslav Royal Air Force officials were negotiating with the French for licenced production of several Gnome-Rhone engine designs, including the K-7, K-9 and K-14. For this reason, it was decided to test the performance of these engines by installing them into several prototype aircraft. This decision included the FP-2 ,which was to be powered by a French Gnome-Rhone K-7, making 420 hp.

The first prototype was officially completed by the end of 1933. It was flight tested by Zmaj test pilot Pavle Bauer. The pilot performed a series of test flights without any problems. As the first flights were successful, the FP-2 was given to the Yugoslav Royal Air Force for further testing in early 1934. For the testing of the FP-2, a commission of seven members was tasked with determining its exact flight performance. The test flight series began on the 19th of February, and after only four days a preliminary report was submitted to the Yugoslav Royal Air Force Command. The report gave mostly positive remarks on the FP-2 performance, with a few changes requested, such as increasing of the fuel load, a better position for the instruments inside the cockpit, modifications of the seats etc. The K-7 engine performance was deemed sufficient, and it was also noted that the testing of the FP-2 with any other engines at the moment was not required. This commission also urged for the FP-2 to be put into production as soon as possible. 

The FP-2 design team expected that a production order was to be given shortly by the Yugoslav Royal Air Force Command. But this was not the case for several reasons. The main problem was the inability of the Rakovica factory to locally produce the K-7 engine by 1936.  Due to high prices, the Yugoslav Royal Air Force could not buy these engines directly from France. Another issue was the adoption of the new Rogožarski ‘PVT’ high-wing training aircraft which used the same engine and offered better performance than the FP-2.

In order to solve this problem, the Zmaj engineers decided to replace the K-7 with the nine-cylinder Valter Pollux II (320 hp) engine. The ensuing flight tests carried out showed that the new engine only worsened the flight performance of the FP-2, due to lower power output. Thus, Zmaj was forced to replace it with the original K-7.

From the end of October to the first half of November 1934, more tests were carried out on the FP-2 with the K-7 by a second commission. This new commission had six members and was tasked with FP-2’s overall performance more thoroughly. These tests also included the testing of a few different types of propellers. The results showed that the metal type propellers gave better performance. In addition, the operational radius was evaluated and the results showed that, at the speed of 100 mph (161 km/h), the FP-2 could stay operational for three hours. Several pilots flight tested the FP-2 and, in general, positive remarks were given about its performance. The changes in the cockpit instrument arrangement was also rated as an improvement. After the tests were completed, this commission gave positive reviews for the FP-2 and suggested that it should be adopted for production as a basic trainer, but not as a fighter trainer due to the lack of performance for this role.

Technical Characteristics

The FP-2 was designed as a single-engine, two-seater basic trainer biplane. The FP-2 was made using wood as its main construction material and then covered with canvas. Its wooden elements were connected using metal pleats and rivets. The fuselage consisted of 16 oval shaped frames that were all connected with four long wooden spars. The wing’s construction was made of wood and then covered with fabric. Rear tail unit was made using a combination of metal and wood, which was then covered in  fabric. The landing gear was a fixed design with two wheels equipped with shock absorbers. There was no rear tail wheel and instead used a small skid which also was provided with a shock absorber. In winter, the front wheels could be replaced with skis.

It was powered by the French K-7 Gnome-Rhone 313 kW (420 hp) engine. The engine itself was placed on a ring shaped housing made of metal and duralumin construction. The maximum speed achieved with this engine was 148 mph (238 km/h). Being designed as a trainer aircraft, its crew consisted of a pilot/instructor and the student.

In Service Before War

For its service in the Yugoslav Royal Air Force, the first prototype was purchased for 577,000 Dinars in 1934. Next year, the contract for the construction of the first batch of 20 aircraft was signed. These were to be produced and given to basic training schools by 1936. All 20 aircraft were completed on time and were given to the First and Second basic training Schools. A few were temporarily given to the Fighter plane school until the more advanced PVT could be built. Once the PVT was adopted for service, the fighter school FP-2s were given to the basic training schools.

The FP-2 was mainly used to replace older training aircraft models that were in service. In its intended role, the FP-2 proved to have satisfactory performance and generally fulfilled the role of a basic trainer successfully. Only one accident was reported in 1938, when, due to a pilot error, control of the plane was lost and it crashed to the ground. The pilot managed to jump out of the plane and safely landed.

The FP-2 was considered a successful basic trainer by the Royal Air Force before the war. [airwar.ru]
During the production run, there were only minor modifications between the different planes. The FP-2 which were built in 1939 were modified with improved control panels with more updated instrumentation. Zmaj also proposed a modified FP-2H powered by the K-9 engine for use by the navy, but it was not adopted. 

By March 1941, around 9 FP-2 aircraft were reportedly awaiting repairs at the Zmaj factory. The fifth batch of 15 FP-2 were to be built by mid-1941. The materials and engine were assembled but, due to the outbreak of the war, none were delivered to the Yugoslav Air Force. Production of the FP-2 was carried out until the Axis invasion of Yugoslavia in April 1941. 

During the April War

At the time of the Axis attack on Yugoslavia in April 1941, all FP-2 were still assigned to the two basic training schools. The First pilot school was transferred near Sarajevo shortly before the outbreak of the war, along with 10 FP-2. The school was operational until the German capture of Sarajevo. The commander of this school, Colonel Adalbert Rogulja, ordered the entire unit to surrender to the Germans without attempting to sabotage its aircraft. 

The Second pilot school, located at the Kapino polje near Nikšić, had 15 FP-2. As the area was not  attacked by Axis forces, this school was operational until the end of war. The remaining FP-2s were stationed in smaller numbers across Yugoslavia. One was destroyed by the Germans in Novi Sad, and a few more in Niš and Pančevo. By the war’s end, both the Germans and Italians managed to capture an unknown number of FP-2s.

In German Service

The Germans managed to capture the Zmaj factory and an unknown number (possibly more than 15) of FP-2 across Yugoslavia. But they were more interested in the factory itself than the FP-2, and for this reason did not use the aircraft that were captured.

In Italian Service

The Italians managed to capture around 13 fully operational FP-2. One was transported to Italy to be flight tested with other captured Yugoslav aircraft (Do-17K and Hurricane) in early June 1941. The remaining 12 FP-2s were stationed at Tirana, but then repositioned in May 1941 to Shkodër to join the 5° Gruppo, which was part of the 39ª Squadriglia. This unit was equipped with older IMAM Ro-37 aircraft. As these were prone to malfunction, the Italians simply reused the FP-2 and pressed them into service. They were mainly used for liaison missions between Tirana and Shkodër. But Partisan activity began to increase in the area and faced with a lack of any other aircraft, the Italians began to arm the FP-2s. The FP-2s were armed with machine guns taken from the Ro-37 aircraft.

The 39ª Squadriglia would be operational until June 1943 in the Shkodër region. It was then returned to Italy and, while it is not clear, there is a chance that at least three FP-2 were still operational with this unit. The final fate of the FP-2s in Italian service is unfortunately not known.

In NDH Service 

After the April War ended, the Germans captured all surviving aircraft production factories, including Zmaj, in Yugoslavia. They restarted production for their own needs. The newly formed NDH (Independent State of Croatia) puppet state asked the Germans for a number of aircraft for their newly formed air force. This included any available Yugoslavian aircraft that survived the war. The Germans supplied the NDH with FP-2s captured in Sarajevo during the war.

In the case of the FP-2s at the Zmaj factory, there were engines and parts for the incomplete fifth production series that could potentially be built. The Germans delayed any decision whether to allow the NDH to take these aircraft. In 1943, an arrangement was reached between the NDH Aviation Force officials and the representatives of Zmaj for the delivery of the 15 FP-2 aircraft. The production process was slow due to the lack of a qualified workforce and constant sabotage by resistance movements. By 1944, only eight FP-2s were completed for the NDH. The remaining seven would remain in Zmaj factory hangars until they were captured by the victorious Communist Partisan forces in October 1944. 

During the war, the NDH Air Force used the FP-2 in its original role of a training aircraft. As the Partisan activity began to rise, some FP-2s were modified by adding bomb racks for six 12 kg (27 lb) bombs. These were then used to fight the Partisans, but as neither the pilot nor the observer were supplied with parachutes, these operations were dangerous.

FP-2 in Croatian service during the Second World War. [histaviation.com]
By 1944, it was obvious that the Axis were on the losing side and, for this reason, many NDH pilots tried to escape to the Partisan side whenever it was possible. One of them was Mitar Оbućanin. While flying an FP-2 (6822) in late August 1944, he escaped to the Partisan held island of Vis. This plane would be used by the Partisans for reconnaissance and liaison. Another attempt was made in October by pilot Drago Markotić and assistant Milan Aćimović. The escape failed and the plane was shot down by German AA ground fire. The pilot was captured and executed but his assistant managed to escape.

This FP-2 (6822) is the plane in which Croatian pilot Mitar Оbućanin defected to the Partisan side. It was then put into service by the Partisans from the isle of Vis. The FP-2 received a large Red Star painted on its side.[vazduhoplovnetradicijesrbije.rs]
The NDH had around 23 FP-2s in their Air Force. The aircraft supplied by the Germans received serial numbers 6801 to 6815 and the ones acquired from Zmaj were 6816 to 6823.

After War Service

With the liberation of Zemun, where the Zmaj factory was located, seven incomplete FP-2s were found abandoned. By late April 1945, two FP-2s were completed and put to use by the new Communist Yugoslav Air Force. The last five were completed by mid 1945. In total, around 13 were operated by the Yugoslav Air Force after the war. They would not remain long in service due to a lack of spare parts. They were mostly used as a target tug to haul flying targets for ground AA crew training.

The parts of one FP-2 can now be seen at the Belgrade Aviation Museum near the Nikola Tesla Airport.

Side view of the FP-2. [airwar.ru]
One of the 13 FP-2s operated by the new Communist Yugoslav Air Force after the war. [vazduhoplovnetradicijesrbije.rs]
 

Production

The FP-2 was produced in several batches from 1934 to 1940. The first batch consisted of 20 aircraft, followed by a second one with 15 planes in 1937, another 15 planes in 1939, and the final batch of 15 in 1940. An additional 15 planes were to be built in 1941, but due to the outbreak of the war, this was never completed. 

Before the war, the total production number of FP-2s made by Zmaj was 65 aircraft, plus the prototype. During the war and, in small numbers, after the war, an additional 15 were built. In total, 81 FP-2 were built.

Modifications

  • FP-2 – Main production version
  • FP-2H – A proposed naval version powered by the K-9 engine, but not adopted for service.

Operators

  • Kingdom of Yugoslavia – Used some 66 planes for pilot training.
  • SFR Yugoslavia – After the war used seven aircraft of this type. They were all captured at the Zmaj factory. These planes were designed for the NDH but never delivered on time.
  • NDH – A dozen aircraft of this type were delivered to the Air Force of the NDH in 1941 by the Germans. In 1944, another eight aircraft were delivered from the Zmaj factory in Zemun.
  • Italy – Used 13 captured planes from May 1941 to June 1943 against the rebels in Montenegro and Albania.
  • Germany – Captured smaller numbers of FP-2s but did not use them.
FP-2 Specifications
Wingspan 35 ft 5 in / 10.8 m
Length 25 ft  11 in /  7.9 m
Height 9 ft 6 in / 2.9 m
Wing Area 310 sq ft / 28.8 m²
Engine One Gnome-Rhone 7K, 7-cylinder radial, 313kW (420 hp) engine
Empty Weight 1.630  lbs / 740 kg
Maximum Takeoff Weight 3.170 lbs / 1,450 kg
Maximum Speed 148 mph / 238 km/h 
Cruise speed:  124 mph / 200 km/h
Effective range 360 mi / 580 km
Maximum Service Ceiling 22,300 ft / 6,800 m 
Crew Two (Instructor and student)
Armament None

Gallery

Illustrations by Carpaticus

FP-2 in Croatian service during the Second World War
FP-2 in Italian Service – 39ª Squadriglia

Credits

  • Article by Marko P.
  • Edited by Stan L. and Ed J.
  • Illustrations by Carpaticus
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  • Vojislav V. Mikić (1998) Italijanska Avijacija u Jugoslaviji 1941-1943, Vojno  istorijski institut Vojske Jugoslavije
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  • F. Vrtulek (2004) Ludbrežanin Inženjer Rudolf Fizir, Podravski Zbornik.  
  • http://www.vazduhoplovnetradicijesrbije.rs/index.php/istorija/229-fizir-fp-2