United States of America

Heavy Bomber Design Study

Introduction

There are very few planes in military and aviation history that have garnered as much attention or popularity as the Boeing B-17 “Flying Fortress”. The aircraft has been called by some “the best bomber of the Second World War”, although there are other contenders for that title. Opinions aside, one cannot dismiss the impact of the B-17 on military history and the evolution of strategic bombing. The development of the B-17 initially started with Boeing Model 299, often incorrectly called the Boeing XB-17 in various sources. Surprisingly, the B-17 was initially not selected for production, as the Model 299 prototype was destroyed in an accident and the US Army Air Corps’ limited budget did not allow for the purchase of the more expensive bomber. As this is such a popular aircraft, one would assume that quite a good portion of what there is to know about the plane and its development has already been researched, and documented. However, as is often the case, there are always discoveries waiting to be found, such as one particular obscure variant of the B-17, the Boeing Model 299G

To say that there is little to no information on this Model 299G would be quite an understatement as, aside from a few drawings, there is nothing that indicates why this aircraft was designed and what its exact purpose was. However, after studying the documents as well as consulting with several well-known aviation experts, it has become somewhat clear that what the Model 299G represents is not just an attempt to create a new and more effective variant of the B-17 based on the already in-production B-17B but, in fact, was a design concept that proved extremely influential in the design of the B-29 “Superfortress”.

Boeing: The American giant and a leader in aircraft design

The Boeing Company exemplifies the idea of rising from small beginnings. It was founded in 1916 on the shores of Lake Washington by a young timber baron by the name of William Boeing, who had an interest in aircraft. The first Boeing aircraft, a seaplane, took off from the shores of Lake Washington in January 1916. However, the company did not really take off until the 1920s and 30s, when Boeing achieved many great and public feats, including designing and building the first all-steel tube fuselage with its then-innovative arc welding process and even becoming one of the first companies to build dedicated mail aircraft. It was also during this time that Boeing would design and build some of its most legendary aircraft, such as the P-26 Peashooter, which, when introduced, was considered to be one of the fastest fighter aircraft in existence.

The company would gain even more fame and recognition with its construction of the Boeing Model 247 in the early 1930s, which allowed Boeing to dominate the early modern airliner market until the introduction of the Douglas DC-2 and the later Douglas DC-3. The Model 247 was considered to be extremely technologically advanced for the time and represented Boeing’s shift to all-metal aircraft construction. Boeing received even greater fame with its development and construction of the Boeing Model 299, which later became the B-17 Flying Fortress, an aircraft that was very well-liked by the top staff of the US Army Air Corps. The B-17 design would also later allow Boeing to create several other highly influential and popular designs based on the Model 299. These designs included civilian aircraft, such as the Boeing Model 307 Starliner and the famed Boeing Model 314 Clipper, which saw great fame while flying for Pan-American Airways in the late 1930s and even saw service as a Presidential transport aircraft for Franklin Delano Roosevelt. The Model 314, while externally quite different, used the same wing structure and design as the Model 299. The Model 299 design also brought forth various military variants which would see various uses, including transport aircraft in the case of the C-108 and VB-17. The Model 299’s development would ultimately culminate with the so-called “ultimate B-17”, the B-17G, which went on to become one of the most popular and well-known variants.

The Birth of Boeing’s big bombers

The development of the Boeing B-17 began in February of 1934, with a US Army Air Corps request for proposals for a new bomber with a range of 5000 miles (8046 kilometers) and a bomb load of at least 2000 pounds (907 kilograms). This request, designated “Project A”, was only a feasibility study for a production aircraft to these requirements. Even with it being a proposal, there was a chance the aircraft would be built, and Boeing put its best designers and engineers on the project and was clearly interested in developing the design. These designers and engineers soon found success, as they were able to successfully design and later build a very good aircraft. Initially, Boeing submitted the XBLR-1 (Experimental Bomber Long Range) for this program, which was later re-designated XB-15 upon its construction. Their competitor, Martin, also submitted a project, the XB-16, but that was later canceled before it actually left the drawing board, nor was a final design for it completed. Because of this, the XB-15 would remain the only bomber built in the XBLR program and was the largest until the Douglas XB-19 was built. The XB-15, while never serving as a bomber as intended, would eventually see service as a transport under the designation XC-105 and would serve until its retirement in 1944. Following its retirement, the aircraft would be partially dismantled and dumped in the so-called “Diabalo Dump”, where it remains to this day.

The Boeing Model 299 and the B-17

 

In May of 1934, the US Army Air Corps announced a second competition, this time for a multi-engine bomber capable of carrying a ton of bombs, having a range of 2000 miles (3219 kilometers), and capable of flying at over 200 miles per hour (173 knots or 321 km/h). Unlike the previous competition, however, this aircraft would be built and brought into limited service, with a potential for full production. For this competition, Boeing decided to design and build what, in essence, was a scaled-down Model 294 (XB-15) under the designation Model B-299. The Model B-299 took many of the base features of the Model 294 and improved on them while scaling down the aircraft. In this regard, it was much like the 294, a twin-wing monoplane with four engines, but it also combined elements of Boeing’s successful Model 247 passenger aircraft. The prototype Model 299 first flew on 28 July 1935 and was very quick to impress the US Army Air Corps as well as the assembled press, with one reporter describing it as a “Flying Fortress”, and the US War Department describing it as an “Aerial Battle Cruiser”. On August 20, the Model 299 was flown to Wright Field, where it would spend the next two months being tested against the Martin 146 and the Douglas DB-1 (B-18 Bolo), where it eventually performed above and beyond the base requirements. The 299 would eventually get the US Army’s stamp of approval as well as an order for 65 YB-17s. However, on 30 October 1935, disaster struck and the Model 299 crashed and burned on takeoff. While the official cause was deemed to be a pilot error, as the pilot had forgotten, due to the lack of a checklist, to unlock the control surfaces (it was this accident that introduced checklists as standard equipment on aircraft), the US Army would cut the order to only 13 planes, designated Y1B-17, and instead ordered the production of 133 Douglas B-18 Bolos. The reason for this decision was twofold. While the destruction of the Model 299 did impact this decision, it was ultimately the US Army’s limited budget and their lack of funding that led them to ultimately choose the B-18 Bolo, as it was the only aircraft they could really afford a large number of. Despite this setback, the US Army was still enthusiastic about the design and allowed Boeing to submit another prototype for evaluation, which they did in the form of a modified Y1B-17 with more powerful engines and a crew of 6 instead of 7.

The Boeing Y1B-17 did not differ too much from the original Model 299, however, some improvements were made, including switching the engines to the more powerful Pratt and Whitney R-1820s and changing the design of the landing gear arms. It was this prototype that ultimately won Boeing the contract and would go on into production as the Boeing B-17B.

The Model 299G: A modified B-17 or Something More?

When looking at the B-17’s lineage, one will notice that the very first mass-produced variant of the bomber was the Boeing B-17B or, as the Boeing Company knew it, the Model 299E (later changed to 299M). The B-17B followed a long line of prior limited or prototype variants, including the base Model 299, later Y1B-17, and Y1B-17A. The production run of the B-17B only ran for a total of 39 aircraft before it was switched to the B-17C (Model 299H). According to the documentation and the drawings found, the Model 299G was considered to be a very heavily modified B-17B which was re-engined with the Pratt and Whitney R-2180 Twin Hornets instead of the Pratt and Whitney R-1820-51 Cyclone. Beyond this, unfortunately, the drawings give very little information on this aircraft or really what exactly it was supposed to be. However, according to historians such as Mike Lavelle, this variant may be a link in the greater chain of designs that led to the Model 345, better known as the B-29 Superfortress.

The Design of the Model 299G

The Model 299G is unique compared to other B-17 variants and designs based on the B-17. It shares very little similarity with the Model 299 and Model 299M (B-17B) designs it is based on. Outside of the tail section and some other components, such as the general design of the wings, the rest of the aircraft is almost a completely different design from the B-17B on which it is based. Among the interesting features is the tricycle landing gear arrangement (one wheelset in the front, two on the wings). The aircraft also features a cockpit section very similar to that of the Boeing Model 307, completely eliminating the turtle deck. It shares a similar fuselage to the Stratoliner as well, as it was designed to test the feasibility of pressurization for use in bombers. Another major aspect that stands out about the aircraft is that it appears to have been both wider and longer than the B-17, with a slightly larger wingspan. Also featured were 4 defensive weapon blisters that almost seem like a cross of those on the early B-17s and those featured on the later PB4Y-2 “Privateer”. These were situated on the dorsal and ventral sections of the waist, with the ventral one just behind the wings and the dorsal one farther aft and closer to the tail.

The Model 299G also did not feature an astrodome. Rather, it featured what appears to have been a dedicated observation area above the cockpit. Perhaps the only major similarity it shared with the B-17 was that the 299G was a monoplane and, the wheels still receded into the engine nacelles. The design, as such, does not really seem to have been that of a B-17, bearing the most similarity to Boeing’s Model 307 Stratoliner, which was later adopted into US Army Air Force service as the C-75 Stratoliner. It also more clearly resembles Boeing’s later bomber designs, such as the Model 322, which eventually led to the development of the Model 345, better known as the B-29 Superfortress.

Conclusion

While, ultimately, the Model 299G never left the drawing board, it certainly represents an interesting insight into the developmental history of Boeing’s large bomber projects. Based on conversations with several Aviation historians, it has been presented as a possibility that this Model 299G could also have been a very early attempt to design a sort of “Superbomber” that members of the so-called “Bomber Mafia”, including Jimmy Doolittle and General Hap Arnold, had been searching for. This conclusion would indeed make sense, as many of the features of the Model 299G do seem to correspond with later Boeing bomber designs. It has also been suggested that the Model 299G might have been a link in the greater developmental chain of the Boeing Model 345, which eventually saw service as the B-29 Superfortess. Some, however, have also suggested that this aircraft instead represented a link between Boeing Airliner development and their Military Aviation development. However, as of this writing, there is no concrete information or documentation that directly links the Model 299G to the Model 345, though it and other projects were part of the B-29 program’s design studies. Aside from general appearance, there is also really nothing concrete to link the 299G to airliner development either. What is undeniable though is that Model 299G does offer deeper insight into the continued development of the B-17 Flying Fortress and the influence, if indirect, it had on future projects.

Variants

Model 299G – The Boeing Model 299G was designed by Boeing and based on the Boeing B-17B. It never went past the design stage and was not selected for production.

Operators (Projected)

 

• United States of America
  • US Army Air Corps (Presumed) – The Model 299G was designed by Boeing but never made it past the design stage.

Illustration

 

Credits

• Article written by J. Manuel
• Edited by  Henry H. & Stan L.
• Ported by Henry H.
• Illustrated by Ed Jackson

Sources

Baugher, J. (1999, July 25). Retrieved from http://www.joebaugher.com/usaf_bombers/b17_1.html

The Boeing Company (2020, December 20). Retrieved from

http://www.boeing.com/history/#/legacy

Harris, S. M., & Angelucci, E. (1983). The Rand McNally Encyclopedia of military aircraft: 1914-1980. New York: Military Press.

Model 299 Crash. (2009, June 25). Retrieved from https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/610002/model-299-crash/

Model 299 Press Release. (2009, June 25). Retrieved from https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/610003/AFmuseum/

Lavelle, Mike. War on the Home Front: Building the B-29 Superfortress. Chester River Press, 2011.

Lavelle, Mike, and Matzelle, Liz. “Fwd Boeing 299G.” Received by Jonathan Manuel, 21 Nov. 2021

Simons, Graham M. The Boeing B-29 Superfortress: The Giant Bomber of World War Two and Korea. Pen Et Sword Aviation, 2012.