United States of America (1945)
Observation Scout Floatplane – 10 Built
XOSE-1 taking off. Notice it is painted in the wartime colors. [axis-and-allies-paintworks.com]The XOSE-1 was an observation float plane built by the Edo float company during World War II and was intended to be a possible replacement for the OS2U Kingfisher. Before being built, the type seemed promising and ten prototypes were ordered. Although development was slow, the aircraft would finally fly after the war had ended. Testing showed the design was riddled with flaws and, with the end of the war making the observation floatplane obsolete and unnecessary, the XOSE-1 program was cancelled.
History
Photo of the mockup XOSE-1.
Before America had entered the Second World War, it was realized that many assets in the United States arsenal were outdated to some degree. Many aircraft were unable to compete with their contemporaries around the world. One such piece of equipment would be the ship launched floatplane. A concept that originated in the 1920s and 1930s, it involved the use of small floatplanes that were carried aboard large warships and could be deployed via catapults for a number of tasks to assist their mothership. These missions included long range scouting, spotting for the warships’ main guns and also providing anti-submarine protection using depth charges or torpedoes. Most of America’s larger warships were equipped with catapults at the time for this purpose. The dedicated ship-based floatplanes the United States Navy (USN) operated at their entrance to the war was the aging Curtiss SOC biplane and the Vought OS2U Kingfisher. The latter would soon replace the former and would enter widespread service after the Attack on Pearl Harbor. Although the Kingfisher was just entering service, the search for a modern seaplane that would eventually replace the aircraft began. The new type was expected to carry out the same duties as its predecessor but also be able to effectively protect itself if needed. The OS2U only had one .50 caliber machine gun for offense, which wasn’t very helpful when against newer fighters. The first and most prominent aircraft that would rise to meet this role would be the Curtiss SC Seahawk, but it would not be the only type that would be built. In fact, a competitor would come from a little known company called Edo.
The Edo Aircraft Company is not a company often mentioned in history regarding the Second World War. The company was founded in 1925 by Earl Dodge Osborne, with the name being an acronym of his own name. Despite being rarely discussed among historians, Edo was immensely crucial to the war effort for the USN. Edo was a primary producer for aluminum floats before the war and would be the main producer for the floats on Navy floatplanes, like the OS2U. It was estimated that up to 95% of floats used on USN aircraft were built by Edo. Not only was Edo responsible for the production of the floats, they were also known for adapting said floats for use on the aircraft that would use them. Edo had become known for their work on floats, but they worked on a handful of their own floatplane designs in the years before WWII had started. However, this was around the time the company was created in 1925, and aircraft design had changed drastically since then. Given their background and knowledge with designing and fitting floats, the USN requested that the Edo company should attempt to design their own modern floatplane for the ship-based observation role. Eager to attempt building a modern aircraft, Edo eagerly accepted the request. On January 11th, 1944, they would begin work on their floatplane, which would be called the XS2E-1.
Frontal view of an XOSE-2 or XTE-1. The two were visually identical from the outside. [axis-and-allies-paintworks.com]The preliminary design of the XS2E-1 was deemed acceptable by the Navy and an order for ten prototypes was made. The XS2E-1 would be a two seat design with a Ranger V-770-8 engine. The engine mount and cowling would also both be designed by Ranger (this company would become Fairchild after the war.) Additionally, a Westinghouse 19 turbojet was to be installed in the rear of the aircraft to offer increased thrust for evasion or to give chase to an enemy aircraft. This would make the aircraft a mixed powerplant type. Another order for eight more units was made some time after the first order, but an exact date is unknown. On March 16th, 1944, the USN opted to change the floatplane’s design. The Westinghouse 19 turbojet that was planned for the project was experiencing its own difficulties in development.
When the XS2E-1 was drafted, the turbojet, due to its development, had become much heavier than what Edo was expecting. Due to this weight increase and a high demand for the jet engine on other aircraft projects, it was removed from the XS2E-1. This caused a weight problem in the aircraft’s design, as it no longer had the additional thrust needed to operate with its then-current weight. Edo changed the aircraft’s design drastically to make the XS2E-1 lighter. A significant revision done was the removal of the second seat, making the aircraft a smaller, single-seater aircraft. This, however, meant all the work the 2nd crewmen was intended to do was now transferred to the pilot, which would include operating the radar system in addition to flying and observing.
A frontal shot of an XOSE-1 demonstrating its folding wings. [axis-and-allies-paintworks.com]After the loss of the turbojet and the switch to a single seater design, it was decided to change the aircraft’s role to an Observation Scout floatplane. Another reason for the change was that, developing parallel to the XS2E-1, was the Curtiss SC-1 Seahawk mentioned earlier, an aircraft that was meant to fill the Scout role for the USN. Finding that developing two aircraft with the same role was redundant, the USN authorized the role change on the XS2E-1. With the new role, the XS2E-1 was redesignated as the XOSE-1. Not long after the role and design change, a full-scale wooden mockup of the new XOSE-1 was built and an inspection was held on November 24th, 1944. An early criticism of the design was linked to the removal of the second seat, as would-be operators complained the intense workload was too much to put onto the pilot. A variant was soon conceived, the XOSE-2, which would address this workload issue by reintroducing the second seat for another crewman. This second crewmen would be tasked with operating the onboard radar system and performing observation duties. An order for two XOSE-2s to be built, as well as for a derivative of the XOSE-2 that would be a dual-control training version, soon followed after conception of the two-seat variant. The trainer would be named the XTE-1. Progress on the program overall was slow up to this point, but Edo had added many innovative features to the design to improve its performance.
Side view of an XOSE-1 taking off. [axis-and-allies-paintworks.com]The war came to an end before the XOSE-1 could take flight. The end of the war saw most of the projects the USN was working on be terminated immediately, as there was no purpose in developing them anymore. The XOSE-1, however, was saved from this fate, as the USN allowed the floatplane to continue development after the end of the war. The XOSE-1’s first flight took place on December 28th of 1945, only a few months after the war had ended. Since there was no urgency to press this new type of aircraft to the frontlines anymore, funding to the program was cut and work slowed down in accordance. The XOSE-2 version finally flew on September 24th, 1947, two years after the war was over. Two XOSE-2s were built. It is unknown exactly when the first XTE-1 was completed and flew, but two of this type were built as well. Originally, during its debut, the XOSE-1 was painted in the standard blue-on-the-top-white-on-the-bottom that mid war USN aircraft used, but would later be colored in the dark blue that late/post-war Navy aircraft were painted in.
Rear view of an XOSE-1 with the floats detached and the wheels attached instead. [axis-and-allies-paintworks.com]Despite being a company that had only built a handful of planes two decades prior, the XOSE-1 was very promising from the outset, but problems soon began to arise during testing. The XOSE-1 experienced trouble with the Ranger built engines. The two seater XOSE-2 experienced many more problems and major changes had to be implemented in the design. Some remedies to the problems included increasing the height of the tailfin and the addition of a ventral strake below the tail to help with stability. Stability issues were found to be caused by the two seater’s larger canopy installed on the largely unmodified fuselage. By the time the stability issues were resolved, it was almost for naught, as the aircraft program was going nowhere.The shipborne floatplane type itself was beginning to show its obsolescence compared to newer technology. Exactly when the program ended or the whereabouts of the ten XOSE built are unknown, as details about the program during this time are sparse. It is unknown if the XOSE-1 was ever even tested from a ship, as many warships postwar would have their catapults removed. Most of the testing was done via land or sea takeoff, with wheels attached to the floats or a landplane conversion where the floats were replaced with a conventional landing gear. The type would be slowly replaced by ship-based helicopters, an idea that had begun during the Second World War and expanded upon thereafter. The era of the scout floatplane, especially shipboard ones, was over. It is most likely all of the XOSE-1s and its derivatives were scrapped before 1950, as all shipboard seaplane squadrons had been disbanded in 1949.
Design
An Edo XOSE-1 in flight [axis-and-allies-paintworks.com]The Edo XOSE-1 was a single-seat floatplane design of all metal construction. It’s floatation was provided by one large aluminum float under the hull, and two smaller aluminum floats on the wingtips. This layout was used on almost every USN floatplane. In addition to floats, the aircraft was also able to be launched via catapult aboard a ship. An optional wheeled undercarriage was also available for ground based takeoffs.
The body of the aircraft would be constructed of metal and would contain 135 lbs (61 kg) of armor. The overall weight of the aircraft would be 5,316 Ib (2411.3 kg) standard and 3,973 Ib (1802 kg) empty. The fuselage would have a length of 31 ft 1 in (9.5 m) and a height of 14 ft 11 in (4.5 m). The XOSE and its variants had a unique construction that allowed many parts of the aircraft to be easily accessible for maintenance.
A rear view of an XOSE-1 with its wings folded back. [shu-aero.com]The Edo XOSE-1 and all of its variants were equipped with the Ranger V-770-8 inline engine that gave it a top speed of 188 mph (302 km/h), a cruising speed of 111 mph (178.6 km/h) and a stall speed of 61 mph (98.2 km/h). The aircraft would have a climb rate of 1,350 ft/min (411.5 m/min) and a maximum service ceiling of 22,300 ft (6797 m). The XOSE-1 would also have a range of 600 mi (965.6 km).
The cockpit would allow protection for the pilot, as the canopy was bulletproof. The canopy was one piece and would slide down and behind the cockpit for easy movement in. On the XOSE-2/XTE-1, the cockpit would be lengthened to accommodate the additional crewman, who would do observation and radar tasks. The canopy on the two seater versions would be two parts and the forward segment would slide back over the rear section.
Fuel would be stored in the fuselage in self-sealing fuel tanks. The tail section of the aircraft would be of metal construction as well. The only differences between the two versions were on the two seaters, in which the tail of the aircraft had to be extended height-wise and a vertical strake beneath the tail was added. Both of these changes helped in the stabilization of the two seaters. The wings of the aircraft were also constructed of metal and would have a wingspan of 37 ft 11 in (11.6 m). The wings would utilize a unique feature for some of its control surfaces. The flaps, that extended outwards from the folding line, would retract automatically if enough water impacted them. This was put in place to prevent damage to these flaps. Additionally, there were retractable slats on the leading edge of the wings to increase drag. The wings themselves could be folded inward for easy storage aboard ships or hangars. Interesting to note, the wings had a manual folding system instead of a hydraulic system most aircraft at the time had.
For armament, the XOSE-1 was equipped with two M2 .50 caliber machine guns as standard. Two hardpoints were equipped on the wings that could allow the XOSE-1 to carry two 350 Ib depth charges or two 50 gallon drop tanks. Additionally, two emergency rescue racks could also be carried on the underside for air to sea rescue missions. A single hardpoint could also be used to carry a radar pod. There is also mention of the XOSE-1 having smoke projectors as well. The two-seat XOSE-2 would lose one of the M2 machine guns and only carry a single gun. The XTE-1 variant would be completely unarmed, given it was only a trainer.
Conclusion
With the Edo XOSE-1 program being terminated, this would be the last time Edo would build an aircraft all on their own. However, Edo would propose a very interesting concept to the US Navy in the 1950s for an amphibious fighter similar to the Convair F2Y Sea Dart. However, this type would never be built.
Variants
XS2E-1 – Initial design of the XOSE-1. The XS2E-1 was a two seater and mounted a larger engine as well as a Westinghouse J19 jet engine. This design was changed and became the XOSE-1.
XOSE-1 – Single seat reconnaissance floatplane. The XOSE-1 had two .50 Cal M2 machine guns mounted in the wings and two hardpoints for depth charges. 6 were built.
XOSE-2 – Two seat version of the XOSE-1. The E-2 version would have a radar operator, a lengthened canopy, and only a single .50 cal for defense. Two were built.
XTE-1– Tandem control version of the XOSE-1. This version would be unarmed and would be used for training purposes. Two were built.
Operators
United States of America – The XOSE-1 and its variants were only tested by the United States Navy.
Edo XOSE-1 Floatplane Specifications
Wingspan
37 ft 11 in / 11.6 m
Length
31 ft 1 in / 9.5 m
Height
14 ft 11 in / 4.5 m
Wing Area
237 ft² / 22 m²
Engine
520 hp (387.7 kW) Ranger V-770-8 Inline Engine
Propeller
2-blade Hamilton Standard constant-speed propeller (9ft / 2.7m diameter)
Powerplant Ratings
Horsepower output
Altitude
Take Off
550 hp
Sea Level
Normal
(Approx. 84% Throttle)
500 hp
800 ft / 244 m
Fuel Capacity
120+58 US Gal / 454+219 L
Weights
Empty
3973 lb / 1802 kg
Gross
5316 lb / 2411.3 kg
Maximum
6064 lb / 2750.6 kg
Climb Rate (at sea level)
1,350 ft / 411.5 m per minute
Maximum Speed
188 mph / 302.6 kmh
Cruising Speed
111 mph / 178.6 kmh
Stalling Speed
61 mph / 98.2 kmh
Range
600 mi / 965.6 km
Maximum Service Ceiling
22,300 ft / 6797 m
Crew
1 pilot
Armament
2x 12.7x99mm / .50 cal Browning AN/M2 machine guns
Edo XOSE-1 in Standard Wartime ColorsEdo XOSE-1 with the additional ventral stabilizers addedA view showcasing the retractable flaps on the engine.
Two Edo XOSE-1s in flight together [shu-aero.com]A side view of the XOSE-1 in flight A side view of the XOSE-1 in flight. [axis-and-allies-paintworks.com]Rear view of an XOSE-2 or XTE-1. [axis-and-allies-paintworks.com]
Credits
Article written by Medicman11
Edited by Stan L. and Ed J.
Illustrated by Ed Jackson
Jane’s All the World’s Aircraft 1947
Norton, Bill. American aircraft development of WWII : special types, 1939-1945. Manchester: Crécy Publishing Ltd, 2016. Print.
Wagner, Ray. American combat planes of the 20th Century : a comprehensive reference. Reno, NV: Jack Bacon & Co, 2004. Print.
With the development of new designs for the Italian Air Force, the need for a more advanced reconnaissance aircraft became apparent. Italians mostly used older biplanes for this role, which was far from a perfect solution, and thus a new design was needed. For this reason, one Re.2000 would be rebuilt and tested as a reconnaissance aircraft. Despite an initial order for serial production, only a few prototypes were ever built.
History
Officine Meccaniche Reggiane SA (Reggio Emilia in Northern Italy) was a WWI-era aircraft manufacturer. After the war it was not involved in any significant aircraft production or design work. Large scale production only began during the thirties, when Reggiane became a subsidiary of the much larger aircraft manufacturer Caproni, which was led by the well known engineer Gianni Caproni. Thanks to him, Reggiane was aided by Caproni’s larger and well qualified aircraft design department. Reggiane and Caproni were involved with several experimental pre-war designs, like the Ca.405 Procellaria and P.32bis, in addition to the licensed production of the S.M.79. In 1938, the development of the Re.2000 began with a request from the Italian Aviation Ministry (Ministero dell Aeronautica) under the codename “Programme R.” This was intended to upgrade the Italian Air Force (Regia Aeronautica) with new and modern designs.
Despite the time and resources involved in development, the resulting Re.2000 would not be adopted for the Italian Air Force. It would see service in countries like Sweden and Hungary in some numbers. Due to the demand for long range fighters and shipboard versions, a small number was adopted for service by the Italian Air Force. From the small number of Re.2000s seized by the Italian Air force, most were from the Series II and III. At least one was used as a base for the experimental two-seat Re.2003 version.
The Re.2003
In early 1941, Italian Air Force officials placed an order for a two-seater reconnaissance aircraft. Reggiane responded by simply reusing the already produced Re.2000 in order to speed up development and to streamline a potential production run. One Re.2000 (MM.478) was modified by adding an additional seat behind the pilot.
The prototype was completed very quickly, and by July it was ready for its first test flight. The test flight was carried out by Captain Francesco Aggelo. The flight was considered successful, but certain modifications were required. These include redesigning the rear observer’s cockpit and the installation of camera equipment. Once these modifications were made, the test flights were resumed in November 1941 with two new pilots.
The Re.2003 seems to have fulfilled all requirements that were demanded. On the 16th of December 1941, an official order for the production of 200 Re.2003 was placed at Reggiane. Production was to commence before September 1942.
Reggiane engineers and designers began working on an improved second prototype in 1942, based on the Re.2002 (MM.12415). The decision to use the Re.2002 was probably based on the fact that it was put into production and was in (very limited) use during the war. In addition, while the Re.2000 was being produced for the export market, it was not adopted for Italian aviation use. Simply put, production in larger quantities was not possible.
Technical Characteristics
The Re.2003 was originally based on the Re.2000, and for this reason, the cosmetic and structural differences were minimal. The Re.2003 was a low wing, mixed construction, but mostly metal, two-seater reconnaissance plane. The fuselage consisted of a round frame covered with aluminum sheets held in place by flush-riveting. The Re.2003’s wings had a semi-elliptical design, with five spars covered with stressed skin. The wings were equipped with fabric-covered Frise type ailerons. The tail had a metal construction, with the controls surfaces covered with fabric. The fuel was stored in the wings, but the precise quantity is not known.
The landing gear system was unusual. When it retracted backward, it rotated 90° (a copy of the Curtiss type) before it moved into the wheel bays. For better handling when landing, the landing gear mechanism was provided with hydraulic shock absorbers and pneumatic brakes. The smaller rear wheel was also retractable and could be steered if needed.
The Re.2003’s engine was the stronger Piaggio P.XI bis RC.40, which had around 1025 hp. Due to being used in limited test flights, precise engine performance is not clear. Author Jonathan Thomson noted that the maximum speed was around 471 km/h (293 mph). The first prototype had the Re.2000’s original engine cowling. The second prototype had a more aerodynamically-shaped cowling, as it was based on the Re.2002.
The most obvious difference was the larger canopy. The front pilot canopy section was more or less the same as the Re.2000. The rear section was somewhat larger in order to provide the observer with a better view. In addition, two small glass windows were added on both sides of the fuselage sides for the observer.
Side view of the Re.2003. Below the rear cockpit, the two small windows placed to provide the observer with a better view of the surroundings can be seen. Source: www.vvsregiaavions.com
The main armament was not changed and consisted of two Breda-Safat 12.7 mm ( 0.5 in) heavy machine guns. The machine guns were placed in the top of the front cowling and fired through the propeller arc. For each machine gun, a provision of 300 rounds was provided. The machine guns could, depending on the combat situation (lack of ammunition, for example), be fired together or individually. The Re.2003 was also tested with a bomb load of 500 kg (1100 lb) placed on the ventral rack.
Operational Use
The Re.2003 first prototype was used by the 1st Gruppo Reserve Aerea (Reserve 1st Air Group), possibly from late 1942 up to the Italian capitulation in 1943. It was then captured by the Germans, who used it as a trainer aircraft. This aircraft, while in German hands, was stationed at the Caproni-Taliedo airfield. Its final fate is unknown.
To make the development of the new Re.2003 fast and easy, Reggiane simply reused the Re.2000 and later Re.2002 for this purpose. While it had a short operational life, it appears that no major problems were encountered during its development and that it could fulfill the designated role as a reconnaissance plane. Source: www.vvsregiaavions.com
Cancellation of the Project
The following year, due to the rapid military deterioration of the Italian Air Force, the need for more advanced fighters had greater priority over other projects. Work on the Re.2003 was slow and, by late 1942, little progress had been made. The second prototype’s development was also proceeding at a slow pace. It made its first test flight in October 1942. Some historians note that the second prototype was never fully completed. In order to increase the production of fighter designs, Reggiane was asked to stop the development of the Re.2003, and instead focus on the production of fighter planes. Only the two prototypes were ever built.
Re.2003 first prototype (MM.478) – One prototype built and used in a limited role. Re.2003 second prototype (MM.12415) – Based on the Re.2002, one built.
Operators
Italy – Operated the first prototype during the war.
Germany – Captured one prototype in 1943. It was used as a trainer plane.
Conclusion
Due to the Re.2003’s short development life, it is not known if it could have fulfilled the purpose the Italian Air Force officials had intended for it. It appears that no major problems were encountered during its development, so there is no indication it had any problems fulfilling its role as a reconnaissance plane. However, without ever being properly tested in real combat conditions, this will never be known.
Re.2003 Specifications
Wingspan
36 ft 1 in / 11 m
Length
26 ft 5 in / 8 m
Height
10 ft 4 in / 3.15 m
Wing Area
220 ft² / 20.4 m²
Engine
One Piaggio P.XI RC.40bis, 1025 hp
Maximum Takeoff Weight
7,210 lbs / 3,270 kg
Maximum Speed
293 mph / 471 km/h
Range
447 miles / 720 km
Crew
Pilot and observer
Armament
Two 0.5 in (12.7 mm) heavy machine guns
Bomb load of 1,100 lb ( 500 kg) bombs.
Gallery
The Re.2003 Prototype – Illustration by Carpaticus
Sources:
D. Nešić (2008) Naoružanje Drugog Svetsko Rata-Italija. Beograd.
M. Di Terlizzi (2002) Reggiane RE 2000 Falco, Heja, J.20, Instituto Bibliografico Napoleone.
J. W. Thompson (1963) Italian Civil And Military Aircraft 1930-1945, Aero Publisher
G. Cattaneo (1966) The Reggiane Re.2000, Profile Publication Ltd.
J. F. Bridlay (1972) Caproni Reggiane Re 2001 Falco II, Re 2002 Ariete and Re 2005 Sagittario, Profile Publications
The modified Yakovlev EG prototype in flight. (Yakovlev OKB) Colorization by Amazing Ace
The EG (also known as the Yak-M-11-FR-1, Sh or Yak-EG) was a prototype helicopter designed in 1946 by the Yakovlev OKB. The EG was designed with a coaxial rotor configuration and had an ambitious performance estimation. Through manufacturer testing, it was revealed that the EG had very undesirable handling characteristics and excessive vibrations when the helicopter reached around 20 mph (30 km/h). These flaws caused the cancellation of the EG project and the completed prototype was converted to an aerosani in 1955 and donated to a farm in the Kazakh SSR. The Kamov OKB would later go on to develop the coaxial rotor configuration further.
History
Lessons of the Second World War showed the world the importance of adopting and developing modern technologies. Throughout the war, autogyros and helicopters became increasingly relevant with several countries’ militaries and saw a dramatic increase in development. The Soviet Union had a very limited selection of these machines during the war, and looked to develop this technology and expand their arsenal. In 1946, the esteemed Yakovlev OKB initiated a project for an experimental coaxial rotor helicopter design. The project was given the nickname of “EG”, for “Experimental Helicopter” (Экспериментальный Геликоптер / Eksperimentahl’nyy ghelikopter). When the task of designing the EG was first announced to the design team, a flabbergasted staff member exclaimed “Shootka?” (шутыш), which roughly translates to “Are you kidding?”. This then led the EG to unofficially be referred to as the “Sh”, a running joke in the design team. Another designation which referred to the EG was “Yak-M-11FR-1”, which referred to the engine that the helicopter would use. The origin of this designation is unknown, but it does not appear to be official.
A detailed cutaway drawing of the modified Yakovlev EG prototype. (Yakovlev OKB)
Responsibility over the project was given to chief designer S.A. Bemov, with I.A. Erlikh as his aide. The EG was envisioned as a coaxial rotor configuration while powered by a 5-cylinder air-cooled Shvetsov M-11FR-1 radial engine producing 140 hp. When the initial design was completed in early 1947, the design team built a flying scale model of the EG to prove the viability of the coaxial rotor design. The scale model was given the designation of ED 115, with the digits referencing OKB-115, the plant designation for Yakovlev OKB.
The modified prototype Yakovlev EG sits on the Yakovlev OKB’s premise with it’s rotor fins folded. (Yakovlev OKB)
After verifying the EG’s design, construction of the actual prototype commenced. The prototype was completed sometime in the summer of 1947 and was promptly subjected to manufacturer’s trials. The EG prototype performed 40 tethered flights (total of 5 hours flight time) before being authorized to perform the first free flight test on December 20, 1947. Through extensive testing, it was revealed that the center of gravity was too far to the rear, which led the team to remove the tail and tailskid and relocate the oil tank behind the cockpit. In early 1948, the M-11FR-1 engine was removed, replace by an experimental M-12 radial engine, a development of the M-11. The first test flight with this engine was conducted on April 9th, but the engine proved troublesome and forced the team to refit the M-11FR-1 engine. Flight tests continued until July 8, 1948, with a total of 75 free flights conducted (total of 15 hours flight time).
Despite the EG showing relatively decent results, it suffered from excessive vibration, loss of stick force and phugoid instability once the machine approached 20 mph (30 km/h). This severely restricted the EG’s practicality and thus warranted the project’s cancellation. The coaxial rotor design configuration was given to Kamov OKB to further develop, while the Yakovlev OKB moved onto more conventional helicopter configurations. A second prototype was in construction but was never completed and was scrapped when the program was canceled. The sole completed prototype was preserved at the Moscow Aviation Institute for a couple of years before being converted to an aero-sleigh by students between 1954 and 1955. The converted sleigh was then donated to a farm in the Kazakh SSR and the fate beyond that is unknown. Photos of this new conversion do not exist. Though ultimately ending up as a failure, the EG was an important stepping stone in Soviet helicopter development and was quite special in the sense that it was the Yakovlev OKB’s first helicopter design.
Design
The original configuration of the Yakovlev EG with a horizontal tail, tail bumper and endplate fins. (Yakovlev OKB)
The Yakovlev EG was a coaxial rotor helicopter powered by a 5-cylinder air-cooled Shvetsov M-11FR-1 radial engine producing 140 hp. The engine drove co-axial two-bladed rotors using a transmission system which featured a centrifugal clutch, a 90-degree gearbox and a cooling fan. Fuel tanks were placed under the gearbox while the oil tank was next to the engine. The rotors (made of laminated pine and hardwood) spun in opposite directions at 233 rpm. Both collective and cyclic pitch control was provided through the rotor’s fully articulated hub mount. The EG’s fuselage consisted of simple welded steel tubes which had D1 duraluminium skin all around except for the engine compartment. The rear fuselage, which was covered with fabric, gradually tapered off to form a fin which was accompanied by a horizontal stabilizer supplemented by two endplate tips. The tail and the horizontal stabilizer would be removed later on in the test phase due to the offset center of gravity. The EG had a non-retractable tricycle landing gear with vertical shock absorber struts. The glazed cockpit compartment could house two pilots, which would enter through doors on either side of the fuselage.
Operators
Soviet Union – The Yakovlev EG was designed with the intent of serving the Soviet Union. The EG was evaluated by Yakovlev OKB but was deemed to be unfit for service due to the excessive vibration and loss of stick control and phugoid instability when the helicopter reached speeds around 20 mph (30 km/h).
146 mi / 235 km – Estimation based on 58 mph / 93 kmh Top Speed
Hover Ceiling
820 ft / 250 m
Flight Ceiling
8,860 ft / 2,700 m – Estimated*
* – Testing never exceeded 590 ft / 180 m
Crew
1x Pilot
1x Co-Pilot
Gallery
Side View Profile of the Yakovlev EG by Ed JacksonA desktop model of the Yakovlev EG. This model does not have the tail components presented. (Yakovlev OKB)The modified Yakovlev EG prototype in flight. (Yakovlev OKB)A side view of the original configuration of the Yakovlev EG with a horizontal tail, tail bumper and endplate fins. (Yakovlev OKB)A side view of the modified prototype Yakovlev EG sitting on the Yakovlev OKB’s premise with it’s rotor fins extended. (Yakovlev OKB)
Nazi Germany (1939)
Experimental jet-engine powered aircraft – 2 prototypes and 1 mockup
The He 178 has the honor to be the first aircraft that made it to the sky solely powered by a jet engine. It was mainly designed and built to test the new jet engine technology. Two would be built, of which the first prototype made its maiden flight in late October 1939, just weeks after the start of the Second World War.
A photograph of the He 178 taken during its first test flight. Source: airwar.ru
Early German jet engine development
The leading German scientist in jet engine development was Hans Joachim Pabst von Ohain. He began working on jet engine designs during the thirties, and by 1935 managed to patent his first jet engine while working at the University of Göttingen. The following year, the director of this University, seeing the potential of the Hans Joachim jet engine, wrote a letter to Ernst Heinkel (the owner of the Heinkel aircraft manufacturer). Ernst Heikel was very interested in the development of jet-powered aircraft, seeing they had the potential of achieving great speed and range. After a meeting with Hans Joachim (17th March 1936), Ernst immediately employed him and his team (led by a colleague named Max Hahn) to work for his company.
In 1936, Hans Joachim and his team began building the first working prototype jet engine, using hydrogen gas as the main fuel, the HeS 1 (Heinkel-Strahltriebwerk 1). The HeS 1 was not intended as an operational engine, but for testing and demonstration purposes only. It was built and tested in early 1937, and was considered successful, so the research continued. The HeS 2 was the second test jet engine that initially used hydrogen gas fuel, but this would be changed to gasoline fuel. While this engine had some issues, it helped Hans Joachim and his team in gaining important experience in this new technology.
In September 1937, a series of modifications were made in order to improve its performance. By March 1938, the third HeS 3 jet engine was able to achieve 450 kg (1,000 lbs) of thrust during testing, much lower than the estimated 800 kg (1,760 lbs). Further modifications of the HeS 3 jet engine would lead to an increase of only 45 kg (100 lbs) of thrust.
Experimenting with the HeS 3 engine mounted on the He 118
In May (or July depending on the source) of 1939, testing of the improved HeS 3A engine began. At the same time, field testing done by attaching this engine to a piston-powered aircraft was being planned. For this reason, an He 118 was equipped with this auxiliary test jet engine. The He 118 was Heinkel’s attempt to build a dive bomber, but the Junkers Ju 87 was chosen instead. Having a longer undercarriage, the He 118 was able to mount the jet engine without any major problem. In order to keep the whole flight testing a secret, the tests were scheduled to start early in the morning.
Drawing of the He 118 equipped with the experimental HeS 3A jet engine. An improved version of this engine would later be mounted in the He 178. Source: www.fiddlersgreen
The pilot chosen for this test flight was Erich Warsitz. When the He 118 reached the designated height using the piston engine, the pilot would then activate the auxiliary jet engine. During this flight, the He 118 powered by the HeS 3A jet engine managed to achieve 380 kg (840 lb) of thrust. More test flights were carried out with the modified He 118 until it was destroyed in a fire accident during landing. Despite this accident, the final version of the HeS 3B jet engine was intended to be mounted in the Heinkel designed He 178 aircraft. While this engine was far from perfect and did not manage to achieve the designer’s expected thrust, Ernst Heinkel urged its installation in the He 178 as soon as possible.
The He 178 history
Interestingly, the whole He 178 development began as a private venture. It was also under the veil of secrecy and the RLM (Reichsluftfahrtministerium), the German Aviation Ministry, was never informed of its beginning. Ernst Heinkel gathered the designers and technical directors to reveal to them ’…We want to build a special aircraft with a jet drive! The RLM is not to know anything about the 178. I take full responsibility!..’
Heinkel was possibly motivated by a desire to get an early advantage over the other German aircraft manufacturers. The main competitor was the Junkers Flugzeugwerke, which would also show interest and invest resources in developing this new technology.
While Hans Joachim was in charge of developing the proper jet engine, work on the He 178 airframe was led by the team of Hans Regner as main designer and Heinrich Hertel, Heinrich Helmbold, and Siegfried Günter as aircraft engineers. The first He 178 mockup was ready by the end of August 1938. Ernst Heinkel was, in general, satisfied with the design, but asked for some modifications of the cockpit and requested adding an emergency escape hatch door for the pilot on the starboard side. The following year, both the He 178 airframe and the HeS 3B jet engine were ready, so the completion of the first working prototype was possible.
Technical characteristics
The He 178 was designed as a shoulder wing, mixed construction, jet engine-powered aircraft. As it was to be built in a short period of time and to serve as an experimental aircraft, Ernst Heinkel insisted that its overall construction should be as simple as possible. It had a monocoque fuselage which was covered with duralumin alloy. The wings were built using wood and were sloping slightly upwards. The wing design was conventional and consisted of inboard trailing edge flaps and ailerons. The rear tail was also made of wood. The pilot cockpit was placed well forward of the wing’s leading edge.
The jet engine used initially was the HeS 3B, but this was later replaced with a stronger HeS 6 jet engine. The He 178 jet engine was supplied with air through a front nose Pitot-type intake, then through a curved shaped duct which occupied the lower part of the fuselage, leading directly to the engine. The exhaust gasses would then go through a long pipe all the way to the end of the fuselage. At the developing stage, there were proposals to use side intakes but, probably for simplicity’s sake, the nose-mounted intake was chosen instead. The He 178 fuel tank was placed behind the cockpit.
The He 178 was to be equipped with a retractable landing gear with two larger wheels in the front and a small one at the rear. All three landing gear legs retracted into the aircraft fuselage. For unknown reasons, this was not adopted early on and many test flights were carried out with landing gear in the down position. One possible explanation was that the Heinkel engineers may have left it on purpose. They probably wanted to have the landing gear down in order to be able to land quickly if the engine failed.
First test flights
The first He 178 V1 prototype was completed by June 1939, when it was transported to the Erprobungsstelle Rechlin (test center). Once there, it was presented to Adolf Hitler and Hermann Göring. Interestingly, prior to the flight testing He 178 V1, another Heinkel innovative rocket-powered aircraft, the He 176 was demonstrated. On 23rd June 1939, the He 178 pilot Erich Warsitz performed a few ground test runs. During this presentation, the He 178 was not taken to the sky, mostly due to the poor performance of the HeS 3A jet engine.
Following this presentation, He 178 V1 was transported back to the Heinkel factory in order to prepare it for its first operational test flight. The first He 178 test flight was achieved on 27th August 1939 at the Heinkel Marienehe Airfield near Rostock. At this stage, the pilot, Erich Warsitz, was instructed by the Heinkel engineers not to fly this aircraft at high speeds, mostly due to the fixed undercarriage. In addition, the HeS 3B could only provide enough thrust for only six minutes of effective flight. During this flight, there was a problem with the fuel pump but, despite this, the pilot managed to land with some difficulty but nevertheless successfully.
While there are only a few photographs of the He 178 V1 prototype, this was taken during its maiden flight on the morning of 27 August 1939. Source: airwar.ru
The flight is best described by the pilot’s own words. ‘…As the aircraft began to roll I was initially rather disappointed at the thrust, for she did not shoot forward as the 176 had done, but moved off slowly. By the 300-meter mark, she was moving very fast. The 176 was much more spectacular, more agile, faster, and more dangerous. The 178, on the other hand, was more like a utility aircraft and resembled a conventional aircraft …In this machine, I felt completely safe and had no worries that my fuel tanks would be dry within a minute. She was wonderfully easy to hold straight, and then she lifted off. Despite several attempts, I could not retract the undercarriage. It was not important, all that mattered was that she flew. The rudder and all flaps worked almost normally, the turbine howled. It was glorious to fly, the morning was windless, the sun low on the horizon. My airspeed indicator registered 600 km/h, and that was the maximum Schwärzler had warned me. Therefore, I throttled back, since I habitually accepted the advice of experienced aeronautical engineers. The tanks were not full and, contrary to custom, I did not want to gain altitude for a parachute jump should things go awry. It was supposed to be a short flight. At 300 to 400 meters altitude I banked cautiously left – rudder effect not quite normal, the machine hung to the left a little, but I held her easily with the control stick, she turned a little more and everything looked good.
After flying a wide circuit my orders were to land at once, this had been hammered into me, but now I felt the urge to go round again. I increased speed and thought, ‘Ach! I will!’ Below I could see the team waving at me. On the second circuit – I had been in the air six minutes – I told myself ‘Finish off!’ and began the landing. The turbine obeyed my movement of the throttle even though a fuel pump had failed, as I knew from my instruments and later during the visual checks. Because the airfield was so small for such flights I was a little worried about the landing because we did not know for certain the safe landing speed: we knew the right approach, gliding and landing speeds in theory, but not in practice, and they did not always coincide. I swept down on the heading for the runway. I was too far forward and did not have the fuel for another circuit. Now I would have to take my chances with the landing, losing altitude by side-slipping. I was flying an unfamiliar, new type of aircraft at high speed near the ground and I was not keen on side-slipping. It was certainly a little risky, but the alternative was overshooting into the River Warnow. Such an ending, soaking wet at four on a Sunday morning, appealed less. The onlookers were horror-struck at the maneuver. They were sure I was going to spread the aircraft over the airfield. But the well-built kite was very forgiving. I restored her to the correct attitude just before touching down, made a wonderful landing, and pulled up just short of the Warnow. The first jet flight in history had succeeded! …’’ Source: L. Warsitz (2008) The First Jet Pilot The Story of German Test Pilot Erich Warsitz.
An interesting fact is that pilot Erich Warsitz managed to be the first man that flew on both a rocket-powered (He 176) and a jet-powered (He 178) aircraft in history.
Heinkel’s attempt to gain the support of the Luftwaffe
During the following months, Hans Joachim tried to improve the HeS 3B jet engine, which would lead to the development of the HeS 6. This jet engine managed to achieve a thrust of 1,300 lb (590 kg), but due to the increase in weight, it did not increase the He 178’s overall flight performance.
As the He 178 was built as a private venture, Heinkel’s next step was to try obtaining state funding for further research from the RLM. For this reason, a flight presentation was held at Marienehe with many RLM high officials, like Generaloberst Ernst and General Erhard Milch. During the He 178 V1’s first attempt to take off, the pilot aborted the flight due to a problem with the fuel pumps. During his return to the starting point, a tire burst out. The pilot, Erich Warsitz, lied to the gathered RLM officials that this was the reason why he aborted the takeoff.
After a brief repair, Erich Warsitz managed to perform several high-speed circuits flights. During the presentation flight, Erich Warsitz estimated that he had reached a speed of 700 km/h (435 mph), which was incorrect, as later turned out… Interestingly, even at this stage, the He 178 was still not provided with the retractable landing gear. The RLM officials were not really impressed with the He 178’s performance, and for now, no official response came from them.
This was for a few reasons. The Luftwaffe had achieved great success during the war with Poland, which proved that the piston-powered engines were sufficient for the job. In addition, Hans Mauch, who was in charge of the RLM’s Technical Department, as opposed to the development of jet engines. He was against the development of jet engines by any ordinary aircraft manufacturer. Another problem was the He 178’s overall performance. During the test flights, the maximum speed achieved was only 595 km/h (370 mph). Hans Joachim calculated that the maximum possible speed with the HeS 6 was 700 km/h (435 mph). The speed was probably affected by the landing gear, which was still deployed and not retracted.
While the RLM did not show any interest in the He 178, Heinkel would continue experimenting with it. While the He 178 did perform many more flight tests, these were unfortunately not well documented. What is known is that, in 1941, the He 178 (with fully operational landing gear) managed to achieve a maximum speed of 700 km/h (435 mph) with the HeS 6 jet engine.
The He 178’s final fate
By this time, Heinkel was more interested in the development of the more advanced He 280. In addition, the use of the HeS 3B jet engine was completely rejected, being seen as underpowered. The interest in the development of the He 178 was lost and it was abandoned. The second prototype, which was similar in appearance, but somewhat larger in dimensions, was never fitted with an operational jet engine. It was possibly tested as a glider. There was also a third mockup prototype built that had a longer canopy.
This is a wooden mockup of the third prototype. While it is somewhat difficult to spot, the front landing gear wheels are actually made of wood and not rubber. Source: airwar.ruFront view of He 178 V2. Strangely, more photographs of the second prototype survived the war than of the first prototype. Source: airwar.ruRearview from the second He 178 V2 prototype. Source: airwar.ruThis is the second V2 prototype which was to be powered by the HeS 6 jet engine but was never equipped with it. Source: Source: airwar.ru
The He 178 V1 was eventually given to the Berlin Aviation Museum to be put on display. There, it was lost in 1943 during an Allied bombing raid. The fate of the second prototype is unknown but it was probably scrapped during the war. While no He 178 prototypes survived the war, today we can see a full-size replica at the Rostock-Laage Airport in Germany.
An He 178 replica can be seen at Rostock-Laage Airport in Germany. Source: Wiki
Conclusion
Today, it is often mentioned that the He 178 was Germany’s lost chance to get an edge in jet-powered aircraft development. What many probably do not know is that the He 178 was not designed to be put into production, but to serve as a test aircraft for the new technology. We also must take into consideration that the jet engine technology was new and needed many years of research to be properly used. While Germany would, later on, operate a number of jet aircraft, they were plagued with many mechanical problems that could never be solved in time. Regardless, the He 178 was an important step in the future of aviation development, being the first aircraft solely powered by a jet engine
Heinkel He 178 (HeS 6 jet engine) Specifications
Wingspan
23 ft 7 in / 7.2 m
Length
24 ft 6 in / 7.5 m
Wing Area
98 ft² / 9.1 m²
Launch Weight
4.405 lbs / 2.000 kg
Engine
One HeS 6 jet engine with 590 kg (1,300 lb) of thrust
Maximum speed
435 mph / 700 km/h
Cruising speed (when towed)
360 mph / 580 km/h
Crew
Pilot
Armament
None
Gallery
Illustration’s by Ed Jackson
He-178 V1
He 178 V2
Sources
C.Chant (2007), Pocket Guide Aircraft Of The WWII, Grange Books
D. Nešić (2008), Naoružanje Drugog Svetskog Rata Nemačka Beograds
Jean-Denis G.G. Lepage (2009), Aircraft Of The Luftwaffe 1935-1945, McFarland & Company Inc
M. Griehl (2012) X-Planes German Luftwaffe Prototypes 1930-1945, Frontline Book
T. Buttler (2019) X-Planes 11 Jet Prototypes of World War II, Osprey Publishing
L. Warsitz (2008) The First Jet Pilot The Story of German Test Pilot Erich Warsitz Pen and Sword Aviation
By the middle of the Second World War, the Germans were losing control of the skies over the occupied territories. Even the Allied air attacks on Germany itself were increasing. In an attempt to stop these raids, the Blohm und Voss company presented the Luftwaffe with a new project which involved using cheap gliders in the role of fighters. While a small series would be tested nothing came from this project.
The Bv 40 was designed as a cheap, armed, and armored fighter glider. This is the first prototype (PN + IA) which was lost on its second test flight. Source: https://www.flugrevue.de/klassiker/kampfgleiter-blohm-voss-bv-40/
History
By 1943, the German Luftwaffe (air force) was stretched to limits in an attempt to stop the ever-increasing number of Allied air attacks. The Allied Bombing campaign particularly targeted German war industry. During this time, there were a number of proposals on how to effectively respond to this ever-increasing threat. Proposals like the use of a large number of relatively inexpensive fighter aircraft, that were to be launched from larger aircraft, were considered with great interest. One proposal went even further by suggesting the use of an inexpensively modified glider for this role. This idea came from Dr. Ing Richard Vogt who was the chief designer at Blohm und Voss.
In mid-August 1943, Dr. Ing Richard Vogt handed over the plans of a cheap and easy to build (without the use of strategic materials which were in short supply) glider that could be built by a non-qualified workforce to the German Ministry of Aviation (Reichsluftfahrtministerium – RLM). The pilots intended to fly this glider were to be trained in basic flying skills only. The initial name of this Gleitjäger (glider fighter) was P186 which would later be changed to Bv 40. After receiving the initial plans the RLM responded at the end of October 1943 with a request for six prototypes to be built. The number of prototypes would be increased to 12 December 1943 and again to 20 in February 1944. If the project was successful, a production order of some 200 per month was planned.
One of the few built prototype is preparing for a test flight. Source: https://www.flugrevue.de/klassiker/kampfgleiter-blohm-voss-bv-40/
Design
The Bv 40 was designed as a partly armored and armed, mixed construction, fighter glider. Its 0.7 m (2ft 3 in) wide fuselage was mostly constructed using wooden materials, while the cockpit was provided with armored protection. The front armor of the cockpit was 20 mm (0.78 in) thick, the sides were 8 mm (0.31 in), and the bottom 5 mm (0.19 in) thick. Additionally, the cockpit received a 120 mm thick armored windshield.
The wings and the tail unit were also built mostly using wooden materials. The rear tail had a span of 1.75 m (5ft 9in). For towing operation, the Bv 40 was provided with a jettisonable trolley that was discarded once the Bv 40 was in the air. Once it was back to the airbase it was to land using a skid.
What is interesting is that in order to have as small a size as possible, the cockpit was designed so that the pilot had to be in a prone position. While a pilot prone positioned design offered advantages like being a smaller target and having an excellent view at the front, it also caused some issues like a bad rearview. While this design was tested in Germany (like the Akaflieg Berlin B9 for example), it was never implemented. Inside the cockpit, there were only basic instruments that were essential for the flight. In addition, due to the high altitude that it was supposed to operate, the pilot was to be provided with an oxygen supply system and a parachute. The side windows had sliding armored screens with integral visor slots that could offer extra protection.
Close up view of the small pilot cockpit. Source: https://www.flugrevue.de/klassiker/kampfgleiter-blohm-voss-bv-40/
The armament of this glider consisted of two 3 cm (1.18 in) MK 108 cannons. These were placed in the wing roots with one on each side. This was serious firepower which could cause a huge amount of damage to the target it hit. Due to its small size, the ammunition loadout was restricted to 35 rounds per cannon. The ammunition feed system was quite simple; it consisted of a rectangular ammunition feed hatch placed in the middle of each wing. Inside the wings, an ammunition conveyor chute was placed to guide the rounds directly to the cannons. There was also a secondary option which included the use of one cannon together with the ‘Gerät-Schlinge’ 30 kg (66 lb) towed guided bomb. This bomb was to be guided by the Bv 40 toward the enemy bombers and was then detonated at a safe distance. In practice, during testing, this proved to be almost impossible to achieve success.
The front view of the Bv 40. Note the towing cable and the release mechanism just behind it. The pilot was beside he armored cockpit also protected by a 120 mm thick armored windshield. The large box with the round capcel (marked as number 5) is the compass housing. Source: https://www.flugrevue.de/klassiker/kampfgleiter-blohm-voss-bv-40/
Other weapon systems were also proposed. For example the use of R4M rockets placed under the wings. There was also a proposal to use the Bv 40 in the anti-shipping role by arming it with four BT 700 type torpedoes or even using 250 kg (550 lbs) time-fused bombs. Due to the extreme weight increase, this was never possible to achieve.
How should it be used?
In essence, the glider was to be towed by a Me-109G to a height of around 6 km before being released. Once released, it was to engage incoming enemy bombers with its two 3 cm (1.18 in) cannons. If circumstances allowed, a second attack run was to be launched. After the attack, the pilot simply guided the glider to the nearby airbase. It was hoped that the small size and armored cockpit would be the pilot’s best defense.
Testing of the Prototypes
Once the first prototype (marked PN+UA) was completed in early 1944, the first test flight made at Hamburg-Finkenwerder was unsuccessful as it was not able to take-off from the ground. A second more successful attempt was made on the 6th (or 20th depending on the source) May 1944 at Wenzendorf. Despite being intended to have an armored cockpit, the first prototype was tested without it. It appears also that during the maiden flight it was towed by another unusual Blohm und Voss design: the asymmetrical Bv 141. But according to most sources, the Me-110 was to be used, which seems more plausible. After the first flight, some modifications to the jettisonable undercarriage were made. On the 2nd June 1944, the first prototype was lost during a crash landing.
The Bv 40 small size is evident here. Source: Pinterest
A few days later the second prototype (PN+UB) made its first test flight. During a dive, it managed to reach a speed of 600 km/h (370 mph). Its final fate is unknown but it was probably scrapped. The third prototype never took off from the ground as it was used for static structural tests. The fourth prototype (PN+DU) was lost during its first test flight but the precise date is unknown. The fifth prototype (PN+UE) made its first test flight on 6th July 1944, but its fate is also unknown. The last prototype (PN+UF) was tested with a new fin section and made its maiden flight on the 27th of July 1944.
During these test flights, the Bv 40 was able to achieve a flight speed of up to 650 km/h (404 mph). During dive testing, the following speeds at different altitudes were achieved: 850 km/h (528 mph) at 4,000 m (13,120 ft), 700 km/h (435 mph) and an astonishing 900 km/h (560 mph) at 5,000 (16,400 ft). Nevertheless, the results of the test flight appear to have been disappointing due to Bv 40’s poor overall flight performance.
The Bv 40 interior of the pilot cockpit. The Pilot was placed in a prone position. While this arrangement was tested on some German aircraft design in practice it was never implemented. Source: https://www.flugrevue.de/klassiker/kampfgleiter-blohm-voss-bv-40/
Rejection of the Project
Once the project was properly revised by the RLM officials, the obvious shortcomings of the Bv 40 became apparent. The Bv 40 was simply deemed too helpless against the Allied fighter cover. In addition, when the report of the first few prototypes was studied, it became clear even to the RLM that the Bv 40 was simply a flawed concept and so it decided to cancel it in mid-August 1944. The next month the Allies bombers destroyed the remaining 14 Bv 40 which were in various states of production.
Not wanting to let their project fail, the Dr. Ing Richard Vogt and the Blohm und Voss designers proposed to mount either two Argus As 014 pulsejets or two HWK 109-509B rocket engines under its wings. Nothing came from this as the Me-328 and Me-163 proved to be more promising (these ironically also ended in failure). There was even a proposal to modify the BV 40 to be used as a Rammjäger (ram fighter) which was never implemented.
Production
Despite initial requests for the production of 200 such gliders only a small prototype series would be built by Blohm und Voss during 1944.
Bv V1 – Lost during its second test flight.
Bv V2 – Fate unknown.
Bv V3 – Used for static testing.
Bv V4 – Lost during it’s first flight.
Bv V5 – Flight tested but final fate unknown.
Bv V6 – Tested with modified fin section.
Bv V7-V20 – Lost during one of many Allied bombing raids on Germany.
Operators
Germany – While testing was conducted on a small prototype series no production order was given.
The Bv 40 side view. Source: http://www.histaviation.com/Blohm_und_Voss_Bv_40.html
Conclusion
The Bv 40 on paper had a number of positive characteristics; it was easy to make, could be available in large numbers, was cheap, well-armed and it did not need skilled pilots. But in reality, the poor performance, lack of a power plant, low ammunition count, and its vulnerability to Allied escort fighters showed that this was a flawed concept. This was obvious even to RLM officials who put a stop to this project during 1944.
The Bv 40 drawings. The small rectangles in the middle of the wings are ammunition feed openings. Source: http://www.warbirdsresourcegroup.org/LRG/luftwaffe_blohm_und_voss_bv40.html
Gallery
Illustration by Ed Jackson
Blohm und Voss Bv 40
Blohm und Voss Bv 40 Specifications
Wingspan
25 ft 11 in / 7.9 m
Length
18 ft 8 in / 5.7 m
Height
5 ft 4 in / 1.63 m
Wing Area
93.64 ft² / 8.7 m²
Empty Weight
1.844 lbs / 830 kg
Launch Weight
2.097 lbs / 950 kg
Climb rate to 7 km
In 12 minutes
Maximum diving speed
560 mph / 900 km/h
Cruising speed (when towed)
344 mph / 550 km/h
Maximum Service Ceiling
23,000 ft / 7,000 m
Crew
Pilot
Armament
Two 3 cm (1.18 in) MK 108 cannons
Or one 3 cm (1.18 in) MK 108 cannon and a glider bomb
Sources
J. Miranda and P. Mercado (2004) Secret Wonder Weapons of the Third Reich: German Missiles 1934-1945, Schiffer Publishing.
R. Ford (2000) Germany Secret Weapons in World War II, MBI Publishing Company.
Jean-Denis G.G. Lepage Aircraft Of The Luftwaffe 1935-1945, McFarland and Company.
M. Griehl (2012) X-Planes German Luftwaffe Prototypes 1930-1945, Frontline Book.
D. Herwig and H. Rode (2002) Luftwaffe Secret Projects, Ground Attack and Special Purpose Aircraft, Midland.
Nazi Germany (1942)
Amphibious Multipurpose Transport – 1 Incomplete Mockup Built
The 1:10 model of the Ar 233. [Dan Sharp]The Arado Ar 233 was an amphibious passenger transport seaplane designed in 1942, a time when it seemed Germany would soon complete its conquest of Europe and conclude the Second World War. Intended for civilian use after the war, the development of the Ar 233 was cancelled due to the deteriorating war situation for Germany in 1944. As the project was deemed low priority, much of the Ar 233’s advanced design work was done in the German Military Administration in France by the Société Industrielle Pour l’Aéronautique (SIPA) aircraft firm located within the Northern German administrative zone. The Ar 233 never materialized, but an incomplete mockup was constructed along with a 1:10 scale model. The incomplete mockup, along with blueprints and notes, were captured by the Free French Forces shortly after the Liberation of France. However, the Ar 233 was not further developed by the French, unlike quite a few of the German aircraft projects undertaken and captured in France. Relatively unknown and often overlooked, the Ar 233 is an interesting obscure project to provide an alternate-history post-war Germany with a suitable transport plane.
History
A cutaway drawing of the Ar 233 in its passenger configuration. [Dan Sharp]The first couple years of the Second World War appeared to have been going firmly in favor of Germany. Most of Western Europe had been conquered by then, and the Wehrmacht was making steady progress in its advance eastwards to conquer the Soviet Union. Despite recently declaring war on the United States, a distant economic powerhouse, Germany still seemed confident in its path to triumph. This feeling was prominent amongst the Germans throughout the initial years of the war. As such, some aircraft firms began to make preparations for post-war German civil aviation early in 1940, in accordance with a request made by the Reichsluftfahrtministerium (RLM / Ministry of Aviation). A few examples of aircraft designed for future German civil use are the Focke-Wulf Fw 206 and Blohm & Voss BV 144. The Arado firm was not exempt from partaking in civil aircraft design and responded with a two engine float plane design.
Designed as a passenger transport, the project began around August within the Arado firm bearing the designation “E 430”. Two variants were originally envisioned, a Bramo 323 R2 powered seaplane model capable of transporting ten passengers and a smaller Argus Ar 204 powered amphibian floatplane (capable of operating from land and water) able to transport eight passengers. According to the RLM, the project officially began in October 1942, but this was likely when it was submitted or approved to the RLM. Work on the project most certainly began in August due to the amount of preliminary steps required. This is further backed up by interviews with former French aircraft designers. As the German mainland’s industry was mostly reserved for military production, the industry of occupied France (German Military Administration in France) seemed like an acceptable place to offload this low priority project. As such, the Arado firm made arrangements for the German-controlled French Société Industrielle Pour l’Aéronautique (SIPA) aircraft firm to assist in the design and production of the E 430. The SIPA firm was founded by Émile Dewoitine in 1938 after his previous firm Constructions Aéronautiques Émile Dewoitine was nationalized. It would appear that, between October and December of 1942, the E 430 project gained the designation Ar 233.
In addition to the update in nomenclature, the smaller As 204 powered E 430 “Amphibium” was cancelled in favor of the ten passenger seaplane. However, the amphibious characteristic of the former was integrated into the Ar 233. Soon after, the French SIPA firm began work on producing a full-scale mockup. The SIPA factory in Île de la Jatte, Neuilly-Sur-Seine, West of Paris, was responsible for the the mockup while the other office at 27/29 Rue Dupont (also in Neuilly-Sur-Seine) and the Dewoitine Design office in 11 Rue de Pillet-Will in Paris were responsible for other work. By Christmas Eve of 1942, it would appear that a large portion of the mockup was completed as the Arado firm released a brochure advertising the Ar 233 which featured images of the mockup. The brochure made mention of four projected Ar 233 variants which included the original passenger airliner, a flying ambulance, a private luxury touring aircraft, and a cargo transport. The French effort in the design work and mockup construction went unrecognized, as all French involvement in the project were omitted from the brochure. However, close examination of a few photos in the brochure shows some of the equipment labelled in German and French.
A wind tunnel model of the Ar 233. The bulge beneath the wing is a extendable float. [Dan Sharp]Further on, it would appear that a 1:10 scale model of the Ar 233 was constructed along with a set of propellers. They were tested separately until May 1943 apparently, when they were paired together and sent to the Nationaal Luchtvaart Laboratorium (NLL / National Aviation Laboratory) facility in Amsterdam, Occupied Netherlands. Other than this model, not much more work appeared to have been done on the Ar 233. This was likely due to the disaster at Stalingrad, when the German 6th Army suffered a catastrophic defeat, and Germany’s ensuing effort to focus on their military industry. Nonetheless, the project remained stagnant for the remainder of 1943 and was finally cancelled in 1944 in favor of military aircraft. When the Allied forces and Free French Forces liberated France, it seems that the mockup and quite a lot of notes and design prints were captured. It does not appear that the French furthered the Ar 233 project after the war unlike quite a lot of the other German projects conducted in France, such as the Heinkel He 274 bomber or Blohm & Voss BV 144 airliner.
A rear view of the Ar 233 mockup which shows the port side entrance hatch. [Dan Sharp]In the end, the ill-fated Ar 233 did not progress beyond the mockup and wind tunnel testing stage, although the project was meant to be a capable amphibious seaplane which could operate in all weathers including the extremes in the North Pole and the Tropical regions. The aircraft also had the luxury of being operable from both land and sea. This also would allow the aircraft to operate in underdeveloped regions which did not have adequate airfields. It also would have made emergency landings safer as calm water surfaces would allow for less dangerous landings compared to rough land terrain.
Design
The incomplete Ar 233 mockup in the workshop of the French firm SIPA, near the outskirts of Paris. [Dan Sharp]The Ar 233 was an amphibious seaplane intended to be powered by two 9-cylinder air-cooled Bramo 323 MA radial engines producing 968 hp each. Each engine would be driven by a three blade propeller which would be started electrically via an onboard generator. The generator would also power the onboard radio systems (FuG X P, FuG 101 and FuBl II F) and a fan to provide ventilation. The Ar 233’s crew consisted of a pilot and a radio operator, though a co-pilot could join the crew. The Ar 233 had four variants which would have the passenger capacity vary. For ease of transport, the Ar 233 was designed so that it could be taken apart and transported via the railroad system.
A rear view of the Ar 233 mockup’s cockpit which shows the pilot and copilot’s seat. Note the hatch in the middle which gives access to the forward passenger luggage compartment. [Dan Sharp]The pilot’s compartment consisted of three seats for a pilot, a co-pilot or passenger and a radio operator. An extra set of controls could be installed for a co-pilot in longer range flights or to train pilots. The cockpit could be accessed via a ladder that folded to the underside of the wing. The side windows in the cockpit could be opened by sliding them forward, while the forward windows could be dropped forward to the bow section. An emergency manual pump was located next to the co-pilot’s seat that could be used to remove water. Visibility from the cockpit appears to be inadequate due to the lack of downwards visibility. Rear visibility also seems to be lacking.
The fuselage of the Ar 233 was a ship-hull shaped in order to allow floating on water surfaces. The fuselage was divided into several sections which, in order from front to end, were the nose wheel compartment, forward baggage compartment, pilot’s cockpit, landing gear hatch, passenger compartment, rear baggage compartment and a washroom fitted with a toilet. Lighting in the passenger compartment was provided by ceiling lights which were powered by a generator. Two air ventilation fans were also provided, with one above the entrance and the other in the land gear shaft. The left side of the fuselage had a door which allowed passengers to enter. The entrance door opened both upwards and downwards, with the latter being able to act as a platform. An emergency exit was provided on both sides, as the middle window in the fuselage could open. The tail of the Ar 233 was designed so that it curved upwards in order to protect the control surfaces by preventing unnecessary contact with the water.
A three-view drawing of the Ar 233 along with it’s basic dimensions. [Dan Sharp]In the passenger airliner configuration, the aircraft could carry eight passengers and two crew members. The seats provided in the passenger compartment were fitted with armrests, side tables, seatbelts, lamps and small luggage nets. The luxury touring configuration only allowed four seats (including the pilot). It would also have had two extra 400 L fuel tanks near the wing edge to extend the range. The cargo transport configuration would carry no passengers and had all seats in the passenger compartment removed for cargo. Any cargo would be loaded through hatches on the fuselage side and would have equipment to secure cargo in flight. In the ambulance configuration, beds could be fitted in the passenger compartment for the wounded.
There would be two wheeled landing gears which would be extendable from the side of the hull for land-based operations. Each one of these wheel measured at 39.96 x 14.96 in / 1,015 x 380 mm. These landing gears, when retracted, remained above the waterline and were hydraulically operated. The nose wheel (width measured at 33.74 x 12.79 in / 875 x 325 mm) sat at the front of the aircraft and could retract into a watertight compartment that could expel excess water with compressed air. If needed, a crewmember could climb above the nose compartment and lift the lid on top to perform maintenance. It was also provided with a locking mechanism. Additionally, the nose wheel’s suspension strength allowed it to perform takeoff and landings at altitudes up to 4,900 ft / 1,500 m.
The Ar 233 was designed so that it could be transported via rail. This blueprint drawing shows the transport configuration. [Dan Sharp]The “V” shaped gull wings that sat on top of the fuselage provided a suitable platform for the engines and propellers, as it allowed them to be mounted at a safe distance from the water. Just behind the engine cowls were a set of hydraulically extended floats for assistance with landing on water. The fuel tanks for the engines were located in the wing leading edge in three “densely riveted” containers. These fuel tanks would be refilled by climbing on top of the cockpit via an access ladder. In addition, hydraulically operated flaps were provided to aid the Ar 233 in landing. These flaps were designed to yield in rough water conditions to reduce damage.
In terms of excess equipment, the Ar 233 could carry a fog horn, rubber dinghy, boat hook, towing gear, ropes, detachable sun canopy, emergency food and water, emergency tools, both ground and sea anchors and various other materials.
Variants
E 430 (Bramo 323 R2) – Original design concept which saw a dedicated seaplane powered by two Bramo 323 R2 radial engines and capable of transporting ten people. This design was further developed by incorporating the amphibious characteristic of the E 430 “Amphibium”. This design was later improved upon and bore the designation Ar 233.
E 430 Amphibium (Argus Ar 402) – Original design concept developed beside the E 430 which saw a scaled down variant powered by Argus Ar 402 engines and capable of carrying eight passengers. This variant could be operated from land and water due to it’s amphibious characteristics. This variant was cancelled but its amphibious design was carried onto the E 430.
Ar 233 (Commercial Airliner) – Commercial airliner design based on the original E 430 design which would be capable of carrying ten people. A pilot and radio operator were part of the crew which allowed for eight passengers. In addition, a co-pilot could be in the crew at the expense of a passenger. Two baggage compartments (located in the hull in front of the cockpit but behind the nose wheel and behind the passenger compartment) and a toilet compartment (located behind the rear baggage compartment) were provided for the passengers. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.
Ar 233 (Luxury Touring Aircraft) – Luxury touring variant intended for sightseeing in remote areas. This variant featured four seats (including the pilot). This variant had the choice of carrying two extra fuel tanks at 400 L each in the outer wings. The envisioned range was 1,120 mi / 1,800 km. This variant also had the choice of implementing an additional set of controls for a co-pilot. It is not known if this variant would retain the two baggage compartments and toilet. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.
Ar 233 (Cargo Transport) – Cargo transport variant which saw the removal of the passenger compartment equipment for cargo. The aircraft in this configuration appeared to been capable of carrying up to 2,200 lb / 1,000 kg of cargo. The cargo would be loaded from doors on the side of the fuselage with equipment provided to secure the cargo. The two baggage compartments and toilet were definitely removed for space. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.
Ar 233 (Flying Ambulance) – Flying ambulance variant which envisioned the possibility of placing four beds in the passenger compartment either for the wounded or for the passengers. This variant was mentioned as the E 430 Flying Ambulance in the Ar 233 brochure, which shows the variant still maintained the original designation. It is not known if this variant would retain the two baggage compartments and toilet. Powered by two 9-cylinder air-cooled Bramo 323 MA radial engines.
Operators
Nazi Germany – The German Arado design firm was the original designer and intended to develop the Ar 233 for use with Lufthansa, the Luftwaffe and other organizations. The project was cancelled in 1944 after Allied forces liberated France.
German Military Administration in France – The SIPA firm under German control was responsible for partially designing and building the Ar 233. All three of SIPA’s facilities appeared to have been working on the project.
Free France – The Free French Forces captured the intact Ar 233 mockup as well as notes and drawings after the Liberation of France, but they did not continue development of the project and presumably scrapped the mockup.
Arado Ar 233 (Commercial Airliner)
Wingspan
77 ft 9.07 in / 23.70 m
Length
68 ft 5.65 in / 20.87 m
Height
21 ft 5.87 in / 6.55 m
Wing Area
807.29 ft² / 75.00 m²
Engine
2x 9-cylinder air-cooled Bramo 323 MA radial engine (986 hp / 735 kW)
Propeller
2x electrically started three-blade propeller
Propeller Diameter
11 ft 5.79 in / 3.50 m
Wheel Width
34.45 x 12.79 in / 875 x 325 mm – Nose Wheel
39.96 x 14.96 in / 1,015 x 380 mm – Fuselage Wheels
Arado Ar 233 – Artist Conception of the Military VersionArado Ar 233 – Artist Conception of the Passenger Version
A blueprint sketch showing how the main landing gear operated. [Dan Sharp]The radio operator’s position which is located behind the cockpit. All the equipment mockups are labeled in French and German. [Dan Sharp]A blueprint sketch showing extension of the forward nose. [Dan Sharp]A blueprint sketch showing the fuel tank arrangement of the Ar 233. [Dan Sharp]Inside view of the incomplete tail section of the mockup. [Dan Sharp]The nose section of the Ar 233 mockup. A tow ring is visible at the tip of the aircraft while two labels above it shows where the landing lights would be positioned. [Dan Sharp]A closeup of the cockpit is shown. The seats are removed and the forward baggage compartment can be seen. [Dan Sharp]A partial view of the Ar 233 mockup’s passenger compartment which shows two very comfortable looking seats. [Dan Sharp]A blueprint sketch shows the wing floats extended. [Dan Sharp]Credits
File No. IV-7 & V-16 Aircraft – Paris Zone (CIOS, Rep. Item No. 25). (1945).
Wasser-Land-Flugzeug Ar 233. (1942). Arado Flugzeugwerke.
United States of America (1945)
Prototype Fighter – 3 Built
The first XP-86 Prototype 45-59598, flown by George Welch
The North American F-86 Sabre is one of the most well-known fighter aircraft of all time, marking the transition from the propeller to the jet turbine. It first entered service with the newly formed U.S. Air Force in 1949, and was instrumental in denying air superiority to Communist forces during the Korean War. After the war ended, many Sabres entered service with dozens of foreign air arms, becoming the primary fighter equipment of many Allied nations. It was built under license in Canada, Japan, Italy, and Australia. Its service was so long-lived that the last operational F-86 was not withdrawn from service until 1993.
History
The F-86 Sabre began its life as North American Aviation’s company project NA-134, which was originally intended for the US Navy. As the war in the Pacific edged toward its climax, the Navy was making plans to acquire jet-powered carrier-based aircraft, which it was could be pressed into service in time for Operation Olympic-Coronet, the invasion of Japan planned for May 1946. The Navy had planned to acquire four jet fighters, the Vought XF6U-1 Pirate, the McDonnell XFD-1 Phantom, the McDonnell XF2D-1 Banshee, and the North American XFJ-1 Fury.
Work on the NA-134 project began in the late autumn of 1944. The NA-134 had a straight, thin-section wing set low on a round fuselage. It featured a straight through flow of air from the nose intake to the jet exhaust that exited the aircraft under a straight tailplane. The wing was borrowed directly from the P-51D, and had a laminar-flow airfoil. It was to be powered by a single General Electric TG-180 gas turbine which was a license-built version of the de Havilland Goblin. The TG-180 was designated J35 by the military and was an 11-stage axial-flow turbojet which offered 4000 lb.s.t. at sea level. The Navy ordered three prototypes of the NA-134 under the designation XFJ-1 on January 1, 1945. On May 28, 1945, the Navy approved a contract for 100 production FJ-1s (NA-141).
At the same time that North American was beginning to design the Navy’s XFJ-1, the U.S. Army Air Force (USAAF) issued a requirement for a medium-range day fighter which could also be used as an escort fighter and a dive bomber. Specifications called for a speed of at least 600 mph, since the Republic XP-84 Thunderjet already under construction promised 587 mph. On Nov 22, 1944, the company’s RD-1265 design study proposed a version of the XFJ-1 for the Air Force to meet this requirement. This design was known in company records as NA-140. The USAAF was sufficiently impressed that they issued a letter contract on May 18, 1945 which authorized the acquisition of three NA-140 aircraft under the designation XP-86.
The Navy’s XFJ-1 design had to incorporate some performance compromises in order to support low-speed carrier operations, but the land-based USAAF XP-86 was not so constrained and had a somewhat thinner wing and a slimmer fuselage with a high fineness ratio. However, the XP-86 retained the tail surfaces of the XFJ-1.
The XP-86 incorporated several features not previously used on fighter aircraft, including a fully-pressurized cockpit and hydraulically-boosted ailerons and elevators. Armament was the standard USAAF equipment of the era–six 0.50-inch Browning M3 machine guns that fired at 1100 rounds per minute, with 267 rounds per gun. The aircraft was to use the Sperry type A-1B gun/bomb/rocket sight, working in conjunction with an AN/APG-5 ranging radar. Rocket launchers could be added underneath the wings to carry up to 8 5-inch HVARs. Self-sealing fuel tanks were to be fitted, and the pilot was to be provided with some armor plating around the cockpit area.
In the XP-86, a ten percent ratio of wing thickness to chord was used to extend the critical Mach number to 0.9. Wingspan was to be 38 feet 2.5 inches, length was 35 feet 6 inches, and height was 13 feet 2.5 inches. Four speed brakes were to be attached above and below the wings. At a gross weight of 11,500 pounds, the XP-86 was estimated to be capable of achieving a top speed of 574 mph at sea level and 582 mph at 10,000 feet, still below the USAAF requirement. Initial climb rate was to be 5,850 feet per minute and service ceiling was to be 46,000 feet. Combat radius was 297 miles with 410 gallons of internal fuel, but could be increased to 750 miles by adding a 170 gallon drop tank to each wingtip. As it would turn out, these performance figures were greatly exaggerated.
A mock-up of the XP-86 was built and approved on June 20, 1945. However, early wind tunnel tests indicated that the airframe of the XP-86 would not be able to reach the desired speed of 600 mph. It is highly likely that the XP-86 project would have been cancelled at this time were it not for some unusual developments.
Saved by the Germans
After the surrender of Germany in May of 1945, the USAAF, along with a lot of other air forces, was keenly interested in obtaining information about the latest German jet fighters and in learning as much as they could about secret German wartime research on jet propulsion, rocket power, and ballistic missiles. American teams were selected from industry and research institutions and sent into occupied Germany to investigate captured weapons research data, microfilm it, and ship it back to the US.
The First XP-86 Prototype in Flight Testing [San Diego Air & Space Museum]By the summer of 1945, a great deal of German data was pouring in, much of it as yet untranslated into English. As it turned out, German aeronautical engineers had wind-tunnel tested just about every aerodynamic shape that the human mind could conceive of, even some ideas even only remotely promising. A particular German paper dated 1940 reported that wind tunnel tests showed that there were some significant advantages offered by swept wings at speeds of about Mach 0.9. A straight-winged aircraft was severely affected by compressibility effects as sonic speed was approached, but the use of a swept wing delayed the effects of shock waves and permitted better control at these higher speeds. Unfortunately, German research also indicated that the use of wing sweep introduced some undesirable wing tip stall and low-speed stability effects. American researchers had also encountered a similar problem with the swept-wing Curtiss XP-55 Ascender, which was so unstable that it flipped over on its back and stalled on one of its test flights.
In 1940, these German studies were of only theoretical interest, since no powerplants were available even remotely capable of reaching such speeds. However, such studies caught the attention of North American engineers trying to develop ways to improve the performance of their XP-86.
Going Supersonic
The first XP-86 prototype in what would be a temporary white paint scheme
The optimal design for an aircraft capable of high speeds produces a design that stalls easily at low speeds. The cure for the low-speed stability problem that was worked out by North American engineers was to attach automatic slats to the wing leading edges. The wing slats were entirely automatic, and opened and closed in response to aerodynamic forces. When the slats opened, the changed airflow over the upper wing surface increased the lift and produced lower stalling speeds. At high speeds, the slats automatically closed to minimize drag.
In August of 1945, project aerodynamicist L. P. Greene proposed to Raymond Rice that a swept-wing configuration for the P-86 be adopted. Wind tunnel tests carried out in September of 1945 confirmed the reduction in drag at high subsonic speeds as well as the beneficial effect of the slats on low speed stability. The limiting Mach number was raised to 0.875.
Based on these wind-tunnel studies, a new design for a swept-wing P-86 was submitted in the fall of 1945. The USAAF was impressed, and on November 1, 1945 it readily approved the proposal. This was one of the most important decisions ever made by the USAAF. Had they not agreed to this change, the history of the next forty years would undoubtedly have been quite different.
North American’s next step was to choose the aspect ratio of the swept wing. A larger aspect ratio would give better range, a narrower one better stability, and the correct choice would have to be a tradeoff between the two. Further tests carried out between late October and mid November indicated that a wing aspect ratio of 6 would be satisfactory, and such an aspect ratio had been planned for in the proposal accepted on November 1. However, early in 1946 additional wind tunnel tests indicated that stability with such a narrow wing would be too great a problem, and in March the design reverted to a shorter wingform. An aspect ratio of 4.79, a sweep-back of 35 degrees, and a thickness/chord ratio of 11% at the root and 10% at the tip was finally chosen.
All of these changes lengthened the time scale of the P-86 development in comparison to that of the Navy’s XFJ-1. The XFJ-1 took to the air for the first time on November 27, 1946, but the XP-86 still had almost another year of work ahead before it was ready for its first flight.
The first XP-86 prototype in flight during testing [North American Aviation]On February 28, 1946, the mockup of the swept-winged XP-86 was inspected and approved. In August of 1946, the basic engineering drawings were made available to the manufacturing shop of North American, and the first metal was cut. The USAAF was so confident of the future performance of the XP-86, that on December 20, 1946 another letter contract for 33 production P-86As was approved. No service test aircraft were ordered. Although the 4000 lb.s.t. J35 would power the three XP-86 prototypes, production P-86As would be powered by the General Electric TG-190 (J47) turbojet offering 5000 lb.s.t.
The first of three prototypes, 45-59597, was rolled out of the Inglewood factory on August 8, 1947. It was powered by a Chevrolet-built J35-C-3 turbojet rated at 4000 pounds of static thrust. The aircraft was unarmed. After a few ground taxiing and braking tests, it was disassembled and trucked out to Muroc Dry Lake Army Air Base, where it was reassembled.
Test pilot George “Wheaties” Welch took the XP-86 up into the air for the first time on October 1, 1947. The flight went well until it came time to lower the landing gear and come in for a landing. Welch found that the nosewheel wouldn’t come down all the way. After spending forty minutes in fruitless attempts to shake the nosewheel down into place, Welch finally brought the plane in for a nose-high landing. Fortunately, the impact of the main wheels jolted the nosewheel into place, and the aircraft rolled safely to a stop. The swept-wing XP-86 had made its first flight.
On October 16, 1947, the USAF gave final approval to the fixed price contract for 33 P-86As, with the additional authorization for 190 P-86Bs. The P-86B was to be a strengthened P-86A for rough-field operations.
XP-86 number 45-59597 was officially delivered to the USAF on November 30, 1948. By that time, its designation had been changed to XF-86. Phase II flight tests, those flown by USAF pilots, began in early December of 1947. An Allison-built J35-A-5 rated at 4000 lbs of static thrust was installed for USAF tests. The second and third XP-86 prototypes, 45-59598 and 45-59599 respectively, joined the test program in early 1948. These were different from the first prototype as well as being different from each other in several respects. Numbers 1 and 2 had different fuel gauges, a stall warning system built into the control stick, a bypass for emergency operation of the hydraulic boost system, and hydraulically-actuated leading-edge slat locks. The number 3 prototype was the only one of the three to have fully-automatic leading-edge slats that opened at 135 mph. Numbers 2 and 3 had SCR-695-B IFF beacons and carried the AN/ARN-6 radio compass set.
The original XP-86 prototype was used for evaluating the effects of nuclear blasts on military hardware at Frenchman Flats. It was later scrapped. [This Day in Aviation]In June of 1948, the new US Air Force redesignated all Pursuit aircraft as Fighter aircraft, changing the prefix from P to F. Thus the XP-86 became the XF-86. XP-86 number one was officially delivered to the USAF on November 30, 1948. The three prototypes remained in various test and evaluation roles well into the 1950s, and were unofficially referred to as YP-86s. All three prototypes were sold for scrap after being used in nuclear tests at Frenchman Flats in Nevada
Design
The three XP-86 prototypes flying in formation together in 1948 [National Archives]Evolving from the NA-134 project with wings borrowed from a P-51, the XP-86 would eventually end up with a low swept wing mounted to a tubular fuselage, with a large jet intake opening at the nose. The plexiglass bubble canopy gave the pilot great visibility, and afforded the pilot a pressurized cockpit. The tail featured a swept back rudder with tailplanes angled upwards, marking a departure from the largely perpendicular angles seen on most of the Sabre’s propeller driven predecessors. The landing gear was a tricycle configuration, which helped balance the weight of the jet engine at the rear.
The wing of the XP-86 was to be constructed of a double-skin structure with hat sections between layers extending from the center section to the outboard edges of the outer panel fuel tanks. This structure replaced the conventional rib and stringer construction in that area. This new construction method provided additional strength and allowed enough space in the wing for fuel tanks.
The wing-mounted speed brakes originally contemplated for the XP-86 were considered unsuitable for the wing design, so they were replaced by a hydraulic door-type brake mounted on each side of the rear fuselage and one brake mounted on the bottom of the fuselage in a dorsal position. The speed brakes opened frontwards, and had the advantage that they could be opened at any attitude and speed, including speeds above Mach One.
The maximum speed of the XP-86 was over 650 mph, 75 mph faster than anything else in service at the time. The noise and vibration levels were considerably lower than other jet-powered aircraft. However, the J35 engine did not produce enough thrust, and the XP-86 could only climb at 4,000 feet per minute. However, this was not considered an issue, since the production P-86As were to be powered by the 5000 lb.s.t. General Electric J47.
The XP-86 could go supersonic in a dive with only a moderate and manageable tendency to nose-up, although below 25,000 feet there was a tendency to roll which made it unwise to stay supersonic for very long. Production Sabres were limited to Mach 0.95 below 25,000 feet for safety reasons because of this roll tendency.
For the second and third prototypes, the ventral brake was eliminated, and the two rear-opening side fuselage brakes were replaced by brakes which had hinges at the front and opened out and down. These air brakes were adopted for production aircraft.
Prototype number 3 was the only one to be fitted with armament. The armament of six 0.50-inch M3 machine guns were mounted in blocks of three on either side of the cockpit. Ammunition bays were installed in the bottom of the fuselage underneath the gun bay, with as many as 300 rounds per gun. The guns were aimed by a Mk 18 gyroscopic gunsight with manual ranging.
Possibly the First Supersonic Aircraft
George Welch Circa 1947 – [San Diego Air & Space Museum]There is actually a possibility that the XP-86 rather than the Bell XS-1 might have been the first aircraft to achieve supersonic flight. During some of his early flight tests, George Welch reported that he had encountered some rather unusual fluctuations in his airspeed and altitude indicators during high speed dives, which might have meant that he had exceeded the speed of sound. However, at that time, North American had no way of calibrating airspeed indicators into the transonic range above Mach 1, so it is uncertain just how fast Welch had gone. On October 14, 1947, Chuck Yeager exceeded Mach 1 in the XS-1. Although the event was kept secret from the general public, North American test crews heard about this feat through rumors and persuaded NACA to use its equipment to track the XP-86 in a high-speed dive to see if there was a possibility that the XP-86 could also go supersonic. This test was done on October 19, five days after Yeager’s flight, in which George Welch was tracked at Mach 1.02. The tests were flown again on October 21 with the same results. Since Welch had been performing the very same flight patterns in tests before October 14, there is the possibility that he, not Chuck Yeager, might have been first to exceed the speed of sound.
In any case, the fact that the XP-86 had exceeded the speed of sound was immediately classified, and remained so for several months afterward. In May of 1948, the world was informed that George Welch had exceeded Mach 1.0 in the XP-86, becoming the first “aircraft” to do so, with an aircraft being defined as a vehicle that takes off and lands under its own power. The date was set as April 26, 1948. This flight did actually take place, but George Welch was not the pilot. In fact, it was a British pilot who was evaluating the XP-86 who inadvertently broadcasted that he had exceeded Mach 1 over an open radio channel. However, the facts soon became common knowledge throughout the aviation community. The June 14, 1948 issue of Aviation Week published an article revealing that the XP-86 had gone supersonic.
Variants
XP-86 45-59597 – The first prototype Sabre produced, was reconfigured many times with various test configurations. May have been the first aircraft to have gone supersonic in October 1947 with George Welch at the controls.
XP-86 45-59598 – The second prototype, had different production model speedbrake and flap configuration, various sensors and equipment installed for testing purposes.
XP-86 45-59599 – The third prototype, and the only Sabre prototype to have been armed, fitted with the standard six M3 Browning guns
Operators
United States – The prototypes were extensively tested by North American Aviation before being handed over to the U.S. Air Force in 1948.
XP-86 – 1st Prototype 45-59597 circa 1947 note it bears the P for “Pursuit”XP-86 – 1st Prototype 45-59597 circa June 1948 in white paint scheme, note the wingtip pitot probesXP-86 – 1st Prototype 45-59597 circa 1948, note the additional test equipment behind the pilot’s seatXP-86 – 2nd Prototype 45-59598 circa 1948XP-86 – 3rd Prototype 45-59599 circa 1948
People’s Republic of China (1958)
Helicopter / Bus / Boat Hybrid – None Built
Perhaps the only known photo of the original Shangdeng No.1 model. (中国飞机全书: 第3卷)
Shangdeng No.1 was an overambitious design undertaken by the Chinese Shanghai Bulb Factory in 1958 to produce a multipurpose vehicle which could serve as a helicopter, a bus and a boat for the National Day celebrations. Vastly unknown both inside and outside of China, the Shangdeng No.1 can be considered one of the People’s Republic of China’s more obscure designs of the 1950s. Quietly canceled after the conclusion of National Day, the Shanghai Bulb Factory would never fulfill their promise of completing the design and preparing it for mass production. This could be attributed to a plethora of reasons, but information is scarce.
History
On October 1st 1958, the People’s Republic of China celebrated the ninth anniversary of the founding of the nation. As their personal way of celebrating this national holiday, representatives of the Shanghai Bulb Factory unveiled a model of a hybrid design as a gift to the government. Unorthodox and, some may rightfully argue, ridiculous in concept, this design (dubbed the “Shangdeng No.1” / “上灯” 1号) was meant to have served as a versatile multipurpose vehicle capable of acting as a helicopter, a boat and a small bus. Upon presenting this model to the government, they proclaimed that design and manufacturing work would be completed in 1959 thus allowing for mass production. However, this would never happen, as work on the project ceased shortly after the model was presented and the conclusion of National Day.
The reason for the cancellation is unknown, but one could speculate a number of reasons. First and foremost, the Shanghai Bulb Factory specialized in the production of lightbulbs, therefore they completely lacked any expertise, experience, qualified personnel and machinery required to design and in turn produce such a conceptually complicated vehicle. A second possible reason why the project was canceled was due to Mao Zedong’s “Great Leap Forward” campaign, which would have the entire country struggle to industrialize and collectivize. The Shangdeng No.1 could have been deemed as useless and thus canceled by the government so that the factory could focus its resources to fulfill government mandated quotas of lightbulb production. Lastly, the Shanghai Bulb Factory could have had no intention of developing the Shangdeng No.1 in the first place, and the model presented could have been just a demonstration to show off Chinese ingenuity and to boost the morale of the Chinese people in a small show of fanciful propaganda. These, however, are just theories to speculate on why the Shangdeng No.1 was canceled. Only one photo is known to exist of the Shangdeng No.1’s scale model presented during National Day.
In conclusion, the Shangdeng No.1 was an overambitious design concept explored by the Shanghai Bulb Factory which resulted in the presentation of a scale model on the ninth National Day of the People’s Republic of China. Absurd in concept, the Shanghai Bulb Factory would have had no possible way of delivering on their promise to produce such a vehicle as they certainly had little to no experience on vehicle design and machinery intended for light bulb production could only produce so little. The fact that a light bulb factory conceptualized this vehicle is quite interesting though, and, to their credit, an intended helicopter/bus/boat hybrid design would most certainly have raised a few eyebrows in the country and in the Western world, assuming that the design was feasible and successful.
As details on this project are so scarce, it has led to some debate on the legacy of the design. A popular claim by numerous online sources is that, after the project was canceled, documents on the Shangdeng No.1 was transferred to the American Boeing firm, and that the Shangdeng’s tandem rotor design served as the inspiration of the Boeing CH-47 Chinook helicopter. This claim is unrealistic and vacuous, as the People’s Republic of China and the United States of America had no formal relations until the late 1960s / early 1970s, nearly a decade after the Chinook was serviced. Therefore, the concept of a Chinese light bulb factory transferring documents to and influencing a world-renowned aviation corporation would be extremely illogical and, frankly, impossible. The United States of America was also no stranger to tandem bladed helicopters designs, as numerous helicopters (eg. Piasecki HRP Rescuer, Piasecki H-21, etc) formerly and currently in service had these designs prior to the conceptualization of the Shangdeng.
Design
The design of the Shangdeng No.1 resembles a rectangular box with rounded edges. A tandem rotor blade configuration was used, and the conceptual power plant of the Shangdeng would have been an unspecified radial engine model capable of producing up to 450 hp, connected to both the front and the rear rotors. The cockpit located at the front of the helicopter would have allowed space for two pilots. Four passengers (or the weight equivalent in cargo) could have been held in the compartment located behind the cockpit. Windows were planned to be installed in the fuselage as can seen in the scale model. Relatively speaking, the Shangdeng’s dimensions are quiet small for a tandem rotor helicopter design. The Shangdeng was only 6 ft 7 in (2.00 m) tall, which would have likely made the interior compartment quite cramped.
Four static wheels were mounted in pairs in the front and rear part of the fuselage which would have moved the Shangdeng in its bus configuration. It is unknown whether or not the design would have allowed the tandem helicopter rotors to be folded in this configuration. If not, the blades could potentially be damaged in urban areas or crowded spaces. It is unknown if a separate transmission would have been connected to the wheels, but this would have certainly greatly complicated the design. If the vehicle in its bus configuration was meant to be propelled by the rotors, that would have been not only unacceptably inefficient, but would have also limited the paths it could travel and would have been highly dangerous to be next to. Steering in the wheeled mode is also unclear.
In its naval configuration, the Shangdeng would have been propelled by an unspecified amount of 15 in / 40 cm propellers in the rear, possibly with assistance from the wheels which would have provided limited propulsion in the water. Again, this would have probably been highly fuel-inefficient. Also, why would a helicopter, which can easily get between any two points by flying, be used as a boat is hard to fathom. How steering was achieved in the boat mode is unclear.
In the helicopter configuration, the Shangdeng would have just been propulsed by the rotor blades and radial engine. The problem of having someone trained both as a pilot, driver and skipper at the same time seems to have gone unnoticed by the designers. As the project did not progress beyond the conceptual model stage, intricate details regarding the Shangdeng No.1 are unknown. However, basic dimensions and estimated performances are provided by 中国飞机全书: Volume III, a book written by People’s Liberation Army Air Force (PLAAF) general Wei Gang (魏钢), former PLAAF model maker and artist Chen Yingming (陈应明) and aviation magazine author Zhang Wei (张维).
Operator(s)
People’s Republic of China – The Shangdeng No.1 would most likely have been operated by the various military branches and likely some civilian institutes if it were to see mass production.
Shanghai Bulb Factory Shangdeng No.1*
* – Statistics taken from中国飞机全书 (Vol. 3)
Length
32 ft 10 in / 10.00 m
Height
6 ft 7 in / 2.00 m
Engine
1x Unspecified Multi-Cylinder Radial Engine Model (450 hp)
The Yer-2ON was a VIP passenger transport aircraft designed in 1944 by Vladimir Grigoryevich Yermolayev and his Yermolayev OKB (design bureau). Based off of the firm’s preexisting Yer-2 bomber, the Yer-2ON was meant to fulfill the role of a government VIP transport aircraft which would carry government members to and from meetings in or out of the Soviet Union. Shortly after Vladimir Yermolayev died on December 31st of 1944 from a typhoid infection, the Yermolayev OKB firm was integrated into Pavel Sukhoi’s Sukhoi OKB firm where the project continued. Despite showing relatively promising performance, the Yer-2ON would eventually be cancelled due to the conclusion of the Second World War and the Sukhoi OKB’s need to concentrate resources on other projects. Thus, the three produced Yer-2ON would never be used for their intended purpose and were presumably scrapped some time post-war.
History
Diplomacy between the Allied countries during the Second World War was an essential step in defeating the Axis powers. With the increasing successes of the Allies during the war, meetings between representatives from the United States, Soviet Union and United Kingdom were held to discuss the future of Europe along with battle plans. In order to attend these meetings, the Soviet government became aware of the need for a long-range VIP passenger transport aircraft capable of carrying 10 to 12 people while maintaining comfort, reliability, cruising abilities at 13,000 ft to 16,400 ft (4,000 m to 5,000 m) and range of 2,500 mi to 3,100 mi (4,000 km to 5,000 km). After Joseph Stalin himself made a request for an aircraft meeting these requirements in January of 1944, a meeting was held between government and Soviet Air Force officials discussing the feasibility of converting existing bomber aircraft to meet this need. Not only would this save time, but also had the benefit of sharing the same airframe as aircraft already in production. In the end, the Yermolayev OKB’s liquid-cooled Charomskiy ACh-30B V-12 diesel engine powered Yer-2 bomber was chosen for conversion. Curiously enough, Yer-2 being used as a transport aircraft is quite ironic, as it reflects on Roberto L. Bartini’s 1937 Stal-7 transport aircraft, from which the Yer-2 bomber was originally developed from.
A frontal view of the passenger compartment. (AviaDejaVu)
Shortly after the NKAP (People’s Commissariat for Aviation Industry) approved Order 351 on May 23, 1944, the head designer of the Yermolayev OKB firm, Vladimir Grigoryevich Yermolayev, began work on converting the Yer-2 into a VIP passenger transport aircraft. In his address to the NKAP on that day, he promised that a completed example would be converted by Factory No.39 and be ready for tests by November 15th. This new variant would be designated Yer-2ON (Osoboye Naznachenie – Special Purpose). With most of the groundwork already completed, Yermolayev was able to complete the conversion blueprints by August. An inspection was conducted on the Yer-2ON’s plans on August 28th and was approved for production. The difference between the Yer-2ON and the standard bomber variant was the removal of all armament and replacement of the bomb bay with a passenger compartment. The passenger compartment would have been able to hold 9 passengers, as well as a flight attendant. All relevant technical drawings were sent to Factory No.39 in the Irkutsk Oblast. A total of four Yer-2 bombers were ordered for conversion, but standard Yer-2 production would run into difficulties as the diesel powered Charomskiy ACh-30B engines manufactured at Factory No.500 were found to have defects and needed to be addressed. As such, the project was put on hold for a considerable amount of time.
A rear view of the Yer-2ON. (Одноклассники)
On December 31st, Vladimir Grigoryevich Yermolayev passed away due to a typhoid infection. As a result, the Yermolayev OKB and its assets were integrated into Pavlov Sukhoi’s Sukhoi OKB firm. It would appear that N.V. Sinelnikov took over as head designer once the project was integrated into Sukhoi OKB. Once the issue with the engines was resolved, three Yer-2 bombers were set aside and were prepared to be converted into the Yer-2ON. Due to the relatively poor documentation of the Yer-2ON’s development, it is unknown when precisely the first Yer-2ON was completed, but most sources allege it was completed at the end of December. The manufacturer’s flight tests and maiden flight appeared to have taken place sometime in February of 1945. Through these tests it was revealed that the Yer-2ON was capable of covering a distance of 3,230 mi / 5,200 km while maintaining a flight ceiling of 19,700 ft / 6,000 m and a top speed of 270 mph / 435 kmh.
On April 16th, the first Yer-2ON made a record non-stop flight from the Irkutsk Aviation Plant’s airfield in Eastern Siberia to Moscow. This flight was accomplished by Heroes of the Soviet Union M. Alekseev and Korostylev over a flight time of 15 hours and 30 minutes and covered a distance of approximately 2,611 mi / 4,202 km. It would appear that a second flight would be conducted sometime near the end of April with the second converted aircraft once it was ready. The second flight had identical circumstances as the first flight (same pilots, destination, fuel load, etc). Interestingly enough, both flights concluded with enough fuel for four more hours of flight, attesting to the Yer-2’s long-range capabilities. A third Yer-2ON was converted at an unspecified time, but details of its tests (if it performed any at all) are unknown. Some internet sources claim that a fourth example was completed on May 10th of 1945, but this cannot be confirmed and disagrees with most publications.
One of the passenger seats of the Yer-2ON. (AviaDejaVu)
Despite the Yer-2ON performing relatively well and passing the manufacturer’s flight tests, the aircraft was never used for its intended role of government VIP passenger transportation. This was likely the result of the project being deemed as low priority within the Sukhoi OKB firm. At the time, Sukhoi was invested in other more pressing projects which led to the Yer-2ON being eventually canceled. Joseph Stalin himself was reputed to have aviophobia (a fear of flying) and the Yer-2ON not entering service did not appear to have consequences for the Sukhoi OKB. Nonetheless, the Yer-2ON project was dropped some time post-war and the three manufactured prototypes were likely scrapped as a result.
Design
A cutout drawing of the Yer-2ON’s interior. (AviaDejaVu)
The Yermolayev Yer-2ON was a two engine VIP passenger transport aircraft based on the Yermolayev Yer-2 bomber aircraft, powered by two liquid-cooled Charomskiy ACh-30B V-12 diesel engines capable of producing 1,500 hp each. The Yer-2ON was identical to the standard Yer-2 bomber in most respects, though armaments and turrets were removed and the bomb bay was converted to a passenger compartment with seats for 9 passengers and 1 flight attendant. The crew would have consisted of a commander pilot, a co-pilot, a navigator, a radio operator, and a flight attendant. In the passenger compartment, the left side (aircraft facing forward) had 5 seats while the right side had 4. The flight attendant’s seat was located behind the last seat on the right side, and was retractable. A luggage compartment was also provided. Another notable feature was the addition of a toilet compartment, as the aircraft’s long-distance travel routes required such a feature. Several windows were installed on the side of the fuselage for the passengers.
Operators
Soviet Union – The Yer-2ON was intended to be used as a passenger transport aircraft for government VIPs traveling in and out of the country to attend meetings.
Yermolayev Yer-2ON*
* – Statistics taken from “OKB Sukhoi: A History of the Design Bureau and its Aircraft” by Dmitriy Komissarov, Sergey Komissarov, and Yefim Gordon
Yermolayev Yer-2ON Side View IllustrationA side view of the Yer-2ON. (AviaDejaVu)The entrance to the passenger section. (AviaDejaVu)This photo shows what appears to be a retractable seat in the rear of the passenger compartment. This seat most certainly would be for the flight attendant. (AviaDejaVu)Toilet compartment of the Yer-2ON. (AviaDejaVu)
USSR (1936)
Experimental Light Bomber – One Prototype Built
Bolkhovitinov’s light bomber was a truly unusual design, with two engines mounted in the same fuselage.
Prior to the German invasion, the Soviet air industry was in the process of developing a series of new experimental ideas and concepts. While generally unknown around the world, some of these were interesting designs, such as the Bolkhovitinov “S” experimental twin-engine fast attack bomber. Due to the German advance and the need for immediately operational planes, the development of this model was terminated.
An Unusual Idea
The leader of the whole S-2M-103 project, aircraft engineer Viktor Federovich Bolkhovitinov.
The S-2M-103 was designed and developed by a Soviet aircraft engineer team led by Viktor Federovich Bolkhovitinov (Ви́ктор Фёдорович Болхови́тинов). Bolkhovitinov (February 1899 – 29 January 1970) was a Soviet professor at the Zhukovsky Air Force Academy in Moscow, and also an aircraft engineer. One of his best known designs was the four-engined Bolkhovitinov DB-A bomber that was intended to replace to aging TB-3 bomber.
During 1936, Bolkhovitinov and his team were looking for a solution for the lack of a high-speed light bomber in the Soviet Air Force. Their answer would be an unusual twin-engine aircraft with a peculiar wing configuration. Instead of a conventional wing placement, the wings were mounted very low on the fuselage, and the tail was a twin fin design.
When they began working on the first calculations and drawings, their greatest concern was how to reduce drag. Usual bomber designs with wing-mounted engines slowed down the plane due to excessive drag. Fighters, on the other hand, had much better aerodynamic properties as they were designed to achieve the highest possible speeds. Bolkhovitinov and his team decided that, for their purposes, they would reuse elements from other bombers (two engines, bomb-carrying capacities, defensive armament) and a one-part fuselage.
The problem was how to position the two engines in order to reduce the drag as much as possible. They quickly came up with the idea of putting them both on the same line (one behind the other) and in the same fighter-like fuselage. While this configuration would make the new plane longer, it could be designed with much better aerodynamic properties.
The development and design of the unusual twin-engine system began in 1936, while work on the aircraft design itself began the next year. By 1938, the design was completed and preparations for the construction of a fully operational prototype began in July that year. The prototype was completed in 1939 and flight tests were scheduled to begin in July 1939 (or in early 1940 according to some sources).
Designation
This was the single-engined version tested during the winter of 1940/41.
The aircraft’s original designation was simply “Bolkhovitinov S” or “Sparka/Cпаренный”, which means twin. Today it is generally known under the “S-2M-103” designation, where the “2” stands for twin-engine configuration and “M-103” is the name of the engine. There were other designations used for this plane, such as “BBS-1” (Ближний бомбардировщик скоростной, fast short-range bomber), “LB-S“ (легкий бомбардировщик спаренный, light twin-engined bomber) оr “BB“ (Болхови́тинов Бомбардировщик, Bolkhovitinov Bomber). As the plane is best known as the the S-2M-103, this article will use this designation.
Technical Characteristics
The S-2M-103 was designed as a low wing, all-metal construction, two-seater, two-engined fast attack bomber. The S-2M-103’s main fuselage had an elliptical cross-section. The fuselage consisted of four (bottom, top and left and right side) panels that were held in place by using four strong angled-section longerons. The S-2M-103’s structure was covered with a modern light alloy stressed-skin.
The wings were constructed using a structural box with flanged lightening holes (to save weight). The wings’ interior sheet ribs were covered on both sides (upper and lower) by metal skin and held in place by flush riveting.
The two three-bladed propellers turned in the opposite directions in order to provide better stability during flight.
The rear twin-finned tail was covered with duralumin skin. For better stability, the rudders were equipped with inset balanced hinges. For the tailplanes’ movement, an irreversible trimming motor was used. The elevator had trim tabs with a variable geared drive.
The S-2M-103 had a completely retractable landing gear that was operated electrically. The front wheels and the smaller rear tail wheel was able to retract backward 90 degrees. During the winter of 1940/41, the wheeled landing gear was replaced with fixed skis.
Drawing of the twin-engined configuration.
This aircraft had an unusual two tandem engine arrangement, placed in the same mounting in the fuselage. The rear-mounted engine’s shaft passed through the front engine’s cylinder blocks. Both engines were connected to the two propellers (with six blades in total) which, when powered, turned in opposite directions, which provided better stability during flight (at least in theory). The S-2M-103 was powered by two 960 hp (716 kW) Klimov M-103’s V-12 liquid cooled engines. This engine was based on the French Hispano-Suiza 12Y which was produced under license by the Soviet Union as the M-100.
The water radiators were placed under the fuselage and had controllable exit flaps. Two oil coolers were located on the ducts on both sides of the two engines. The fuel was stored in four fuel tanks that were placed in the wings (between the wing spars). Unfortunately, there is no information available about the capacity of these tanks.
The two crew members were positioned in an unusually large cockpit fully enclosed with a plexiglass canopy. The crew consisted of the pilot and the navigator. The navigator was also provided with a bombsight. The navigator’s position was covered with plexiglas on all sides, which provided him with an excellent all-around view, including under the plane. His additional role was to operate the rear-mounted machine gun.
The S-2M-103 lacked any forward-firing offensive armament. While it was planned to equip it with weapons mounted in the wings, this was never accomplished. For self-defense, one 0.3 in (7.62 mm) ShKAS machine gun was provided for the navigator/gunner. Due to its tail design, the rear machine gun had a wide firing arc. Later, it was planned to replace the single 7.62 mm rear gun with heavier twin 0.5 in (12.7 mm) UBT machine guns. There were also alleged plans to equip the S-2M-103 with a rear-mounted remotely controlled ShKAS machine gun. Whether this was ever implemented is unknown, as there no photographs or precise information are available. The bomb bay, which could carry 880 lb (400 kg) of bombs, was located under the pilot cockpit. The bomb bay opening doors were opened electrically.
Operational Tests
Side view of the S-2M-103.
The S-2M-103, piloted by D.N. Kudrin, made its first test flight in late 1939. More tests were carried out by the Army from March to July 1940, the plane being piloted by D.N. Kudrin and A.I. Kabanov. During these flight tests, the S-2M-103 proved to be able to achieve a maximum speed of 354 mph (570 km/h) at 15,400 ft (4,700 m). The tests also proved that the concept of installing two engines in the same fuselage had some advantages over the wing-mounted configuration. The most obvious was the reduced drag, which lead to increased speed and improved flight performance.
There were also some problems with the design. Immediately noticeable were the poor take-off and landing performance during these tests trials. Due to its high weight of 12,460 lb (5,650 kg), the S-2M-103 needed a 3,430 ft (1,045 m) long airfield. More tests were carried out by removing any extra weight. With the weight being reduced by some 1,100 lb (500 kg), the S-2M-103 now only needed a 2,800 ft (860 m) long airfield. During landing at speeds of 103 mph (165 km/h) the aircraft needed a 2,130 ft (650 m) long airfield. Some problems with the twin propellers were also noted. The rear-mounted propeller drive shaft was damaged due to strong vibrations. Unfortunately, there are no records of cruising speed, climbing speed, or maximum service ceiling.
The Single-Engine Version
For testing during the winter of 1940/41, instead of the standard landing gear, fixed skies were provided.
In the following months of 1940 and 1941, the S-2M-103 received a number of modifications in the hope of solving the issues observed during preliminary testing. The twin-engine configuration was replaced with a single M-105P engine with a power of 960 hp (or 1,050 hp depending on the source). The area where the second engine was previously located was filled in order to maintain the stability of the aircraft. Due to the removal the second engine, the second contra-rotating propeller was no longer needed. The new engine’s oil coolers were placed in the main radiator duct. The designers had a dilemma about what to do with the extra interior space left by the removal of the second engine, but this was never solved completely. With these modifications, the weight was reduced from 12,460 lb (5,650 kg) to 8,820 lb (4,000 kg).
The wing design was also changed to one done by Z.I. Iskovich by increasing its size and using a new aerofoil shape. The previous wing design had an area of 246.5 ft² (22.9 m²), while the new one had 252 ft² (23.4 m²). The last change was made to ease testing during winter, replacing the landing gear with fixed skis.
It appears that no official designation for this version existed but, using the same logic as for the two-engine version, it could be called S-M-105, but this is only speculation at best. According to some sources, the single-engined variant was marked as the S-1.
There were plans to improve the performance of the projected fighter version by mounting two M-107 engines. The new fighter was to be designated simply as the “I” or “I-1”. Due to the later cancellation of the S-2M-103 project, the I-1 was also abandoned.
The Fate of the S-2M-103 Project
More flight tests were carried out during the first half of 1941. While there is no precise information, the newly modified single-engined version of the S-2M-103 allegedly had poor performance. Despite the modifications, the new single-engined version managed to achieve a much lower top speed of 248 mph (400 km/h) at 14,440 ft (4,400 m). The poor performance, preparation for Pe-2 production at the factory where it was built, and the German Invasion of the Soviet Union led to the cancellation of the S-2M-103 project.
Operators
TheSoviet Union – A single prototype was tested in 1940/41, but was not adopted for production.
Variants
S-2M-103 – Twin engine fast bomber
S-2M-103 (possibly S-M-105) – Single-engine version
I-1 – Improved fighter version equipped with two M-107 engines, due to cancelation of the S-2M-103 none were built.
Conclusion
The concept of installing two engines in the same fuselage had some advantages over the wing mounted configuration. It reduced drag, which lead to increased speed and flight performance. The S-2M-103 proved this by achieving speeds of up to 350 mph (570 km/h). However, its design had issues that were never resolved. Given enough time, those might have been solved. Alas, in 1941, the German Invasion and the need to increase production of already existing aircraft stopped all unimportant projects.
Drawing of the S-2M-103.View of the engine compartment interior.Rear view of the S-2M-103.
Credits
Gordon, E. & Khazanov, D. (1998). Soviet combat aircraft of the Second World War. Leicester Osceola, WI: Midland Pub. North American trade distribution by Motorbooks International.
Yefim G. and Bill G (2000), Soviet X-Planes, Midland Publishing
United States of America (1945)
Kingdom of Italy (1941
USSR (1946)
Nazi Germany (1939)
People’s Republic of China (1958)
