Fletcher Aviation's bomb gliders

It has been long-known that US guided missile technology in World War II was very primitive at best, with American aerospace and weapons companies equipping straight-wing aircraft designs with explosives and bombs with guidance systems so those machines could function like a missile in terms of wreaking destruction on enemy targets in Europe and the Pacific. However, lost in aviation historians' discussions of early US guided missiles is the fact that in World War II the US Army Air Force and US Navy devised schemes to create bomb-laden gliders, with the Navy concocting the GLOMB (GLide bOMB) concept under the LB (glide bomb)-series designations, and the USAAF introducing the BG (Bomb Glider) category for their bomb-laden gliders. In particular, even though Radioplane and Interstate Aircraft led the way among southern California aviation companies in building radio-controlled bomb-packed aircraft, one aircraft manufacturer in the region involved in making explosive-filled aircraft in World War II that is overlooked by most aviation historians is Fletcher Aviation. Thanks to a copy of Bill Norton's 2012 book American Military Gliders of World War II, I now have had the liberty of illuminating and clarifying in detail the oft-forgotten story of Fletcher Aviation's efforts to develop explosive-filled glider designs, the BG-1 and BG-2.

The Fletcher Aviation Corporation was founded in Pasadena, California, by the Fletcher brothers (Wendell, Maurice, and Frank) in 1941, initially aiming to build a wooden basic trainer aircraft for the US Army Air Force. The resulting trainer design conceived by Wendell Fletcher, the FBT-2, had a Wright R-760 Whirlwind radial piston engine and a fixed tailwheel undercarriage, with seating for a pilot and flight instructor. The FBT-2 prototype (civil registration NX28368) flew in 1941, but the design failed to attract serious interest from the US military. Fletcher eventually decided to convert the FBT-2 prototype into a drone control aircraft under the designation CQ-1 (CQ=drone control aircraft), with tangible design changes including the replacement of the conventional landing gear by a tricycle undercarriage, the elimination of the turtle deck, and the swapping of the R-760 for a Pratt & Whitney R-985 Wasp Junior. The prototype CQ-1 (serial number 41-38984), would later form the basis of the PQ-11 target drone, of which ten were ordered (serial numbers 42-46892/46901). However, the PQ-11 was cancelled by the USAAF in favor of the Culver PQ-8 Cadet, and the ten PQ-11s on order were completed as a new bomb glider design based on the CQ-1, the BG-1 (designated Model 17 by Fletcher) (Andrade 1979).

Left: Fletcher BG-1 during testing at Muroc Army Air Field (now Edwards Air Force Base), spring 1942 (courtesy of National Museum of the US Air Force); Right: 3-view drawing of the Fletcher BG-1 bomb glider (courtesy of Bill Norton, via George Cully)

 The BG-1 was basically a CQ-1/PQ-11 with the R-985 engine removed and replaced by remote control systems and a round encasing for a 2,000 pound AN-M34 warhead. For combat missions, the BG-1 would be released 11 miles from an enemy target by a bomber and the operator aboard the towplane would guide the BG-1 to its target via TV screen (Norton 2008, p. 129). While the BG-1 had a simple windscreen and overturn bar, the first BG-1 to be completed had the sliding canopy seen in the CQ-1 and PQ-11, and was devoid of remote control gear. On April 26-27, 1942, the BG-1 made its first tow-and-free flights at Muroc Army Air Field, with Fletcher test pilot LaVerne Browne (aka John Trent) at the controls and a Douglas B-23 Dragon bomber serving as the towing aircraft. By June, five BG-1s had been delivered to the USAAF, all equipped with a 3-axis compact hydraulic servo unit, radio equipment, electric motor throttle control, an SCR-549 television transmitter, a wind-driven generator under the rear fuselage, and bomb arming equipment. The sole CQ-1 was fitted with a mockup of a TV guidance system fairing under the left wing, with stall tests conducted on August 23, 1942 (Norton 2012, pp. 209-210). It was also planned to conduct a flight test of the BG-1 with a 1,000 lb warhead at El Paso, Texas, to avoid overload.

A 3-view drawing of the proposed Fletcher BG-2 twin-fuselage bomb glider. The similarity of the vertical stabilizer shape and tricycle undercarriage to that of the CQ-1 and BG-1 is evident (courtesy of Bill Norton, via George Cully).

Even before flight tests of the BG-1 began, in January 1942, Fletcher proposed a twin-fuselage bomb glider, the Model 16, which had the same length as the CQ-1/PQ-11 and BG-1, but had a 45 foot wingspan and a TV fairing under the inboard wing either on the centerline or in the starboard fuselage nose.* The BG-1 fuselages were joined by a center wing section and a horizontal tail, and each fuselage carried a 2,000 lb warhead. Empty weight was to be 2,432 pounds, with the gross weight estimated at 6,531 pounds and the planned stalling speed was 84 mph. The Model 16 was designated XBG-2 by the Army Air Force and on April 1, 1942, a contract was awarded to build three BG-2 prototypes (serial numbers 42-46902/46904). However, according to an Engineering Division memorandum dated June 9, 1943, flight characteristics of the BG-1 during testing were judged unsatisfactory, and so a recommendation was made for the USAAF to cancel the BG-1 and BG-2 programs. Therefore, the BG-2 program was axed on September 8, 1942 before any of the XBG-2s on order could be completed (Norton 2012, p. 210). (One more USAAF glider design was given a BG-series designation, the similarly unbuilt forward-swept wing Cornelius XBG-3, but that's another story.) For one thing, the US Army Air Force must have realized that the bomb glider concept was going to be unfeasible in practice due to the fact that the weight and drag of the bomb glider would have caused the engines of a bomber towing the glider to overheat while on a combat mission over hostile territory, but also because free-fall guided bombs were faring poorly in combat.  

*Andrade (1979, pp. 59, 96) states that the three BG-2s on contract were originally ordered as a production batch of the 8-seat Frankfort CG-1 transport glider, while the June 1946 edition of Model Designations of Army Aircraft confusingly describes the BG-2 as a transport glider (although that description actually applies to the Frankfort CG-2 transport glider project, which was to carry 15 troops). However, this assertion is refuted by the available drawing of the BG-2 from Fletcher Aviation project documents and the description of the BG-2 given in the January 1945 edition of Model Designations of Army Aircraft, and Norton (2008, p. 130) states that the BG-2 itself was derived from the CQ-1, like the BG-1. Therefore, Andrade's claim that the BG-2 was based on the CG-1 is clearly due to the mention of "CG-1" under the BG-2 entry on page 96 being a typographical error for CQ-1, because the BG-2 had the same vertical stabilizer design as that of the CQ-1 and BG-1 (see drawings and photos in Norton 2012), and was of a completely different design than the CG-1 and CG-2 (see drawings of the CG-1 and CG-2 in Norton 2012, pp. 52-53). Additionally, the XBG-2 contract was signed shortly after the CG-1 and CG-2 were cancelled without a prototype reaching the flight stage. The misidentification of the BG-2 as a CG-1 derivative isn't the only error made in Andrade's book; other mistakes in the volume include description of the Kaiser-Fleetwings XA-39 as a twin-engine aircraft (the XA-39 was definitely a single-engine aircraft like the Navy's BTK), identifying the C-127 designation with the Boeing 493-3-2 turboprop derivative of the Boeing C-97 Stratofreighter (C-127 was actually the original designation for the turboprop-powered C-124B version of the Douglas C-124 Globemaster II), identification of the Martin XNBL-2 long-range bomber project as a monoplane (the XNBL-2 was actually a biplane), and the inclusion of the Wasp Major-powered Douglas Model 423 among design studies for the Douglas XB-31 (only the 140-foot span Model 332 was designated the XB-31, and the Model 423 was envisaged in late 1941, long after the B-29 Superfortress and B-32 Dominator were selected over the XB-30 and XB-31). 

References:

Andrade, J. M., 1979. US Military and Aircraft Designations and Serials since 1909. Leicester, UK: Midland Counties Publications.

Norton, W. J., 2008. Sideshow Curiosities: American Military Glider Experiments of World War II. American Aviation Historical Society 53 (2): 113-134.

Norton, W. J., 2012. American Military Gliders of World War II: Development, Training, Experimentation, and Tactics of All Aircraft Types. Atglen, PA: Schiffer Publishing.   

The PB3Y: Consolidated's unbuilt successor to the PB2Y Coronado

 The Consolidated PBY Catalina and PB2Y Coronado are well-documented in the literature on US naval aircraft of World War II as the poster boys of US anti-submarine warfare campaigns during the war, namely the Battle of the Atlantic and the sinking of Japanese submarines in the Pacific theater. Also of note is the fact that Consolidated (later Consolidated Vultee, then Convair) built several B-24 Liberator bombers for the US Navy as the PB4Y-1, from which a dedicated maritime patrol landplane, the PB4Y-2 Privateer, was developed. However, virtually lost in talk of US patrol aircraft development in World War II is one Consolidated project for a giant maritime patrol flying boat, the PB3Y. For a long time, the story of the PB3Y has been an enigma because of the length of time it was designed and developed but without ever leaving the drawing board. Now, thanks to my analysis of Consolidated's evolving priorities in military aircraft development from the late 1930s until the Japanese attack on Pearl Harbor as well as company documents, it is now possible to reconstruct the history of the design and development of the PB3Y.

A wind tunnel model of the initial Model 30 flying boat (XPB3Y-1) with a single vertical stabilizer

In January 1937, Consolidated began design studies for a new flying boat as a long-term replacement for its upcoming and yet-to-be flown PB2Y Coronado under the company designation Model 30. The first design of the Model 30, labeled 'XPB3Y-1' in company documents, retained the single vertical stabilizer initially fitted to the XPB2Y-1 but was 75 percent larger and heavier than the PB2Y-1, with a wingspan of 180 feet (54.86 meters), and power was supplied by four R-2800 radial piston engines. Accommodations were provided for four crewmen (pilot, co-pilot, navigator, and communications operator), and defensive armament included remote-controlled nose, dorsal, and tail turrets as well as a manually-controlled turret behind the step. Consolidated's informal use of the XPB3Y-1 label for the initial Model 30 proposal probably reflected anticipation of a future requirement for a new-generation long-range patrol flying boat because a Convair tailless land-based patrol bomber study of the 1940s was informally dubbed 'XP5Y-1' by Convair (the P5Y designation was formally used for the turboprop-powered Convair Model 117 flown in 1950, but that's another story). In fact, in May 1937, the US Navy issued requirement SD116-16 for a long-range patrol flying boat to replace the PB2Y Coronado, and because the Boeing 319 derivative of the 314 passenger flying boat but also the company's 320 twin-hull flying boat and the Martin Model 160A  were also conceived in the early 1937, it seems plausible that the initial Model 30 design was conceived along with the Martin Model 160A and Boeing 319 and 320 for the SD116-16 requirement.  

An artist's concept of a revised Model 30 design (XPB3Y-1) with twin vertical stabilizers from the project documents.

In January 1938, the US Navy tweaked the parameters of requirement SD116-16 to produce an updated operational requirement, SD116-19. In response, Consolidated revisited the Model 30 by having the design revised to incorporate the twin-rudder tail empennage eventually used for the PB2Y and a cockpit partially blending with the nose, and several Model 30 iterations were proposed with radial and V-cylinder engines. The Model 30/XPB3Y-1 design conceived in February 1938 was powered by four Wright R-3350 Duplex Cyclone radial piston engines and had a wingspan of 190 feet (57.91 meters), a wing area of 3,200 square feet (297.60 square meters), an empty weight of 57,258 lb (25,972 kg), a gross weight of 124,700 lb (56,563 kg), a top speed of 246 miles per hour (396 km/h), and a range of 8,200 miles (13,194 km). Fifteen crewmen were carried, and defensive armament was to consist of ten .50 caliber machine guns and one 20 mm cannon, housed in remote-controlled turrets on the nose, top waist, and tail, and manually-controlled turrets on the sides of the fuselage and behind the step, while 36,000 lb (16,330 kg) of bombs were carried. The gunners were also placed in the leading edges of the wing fillet, and passageways led outboard of the engines to two cupolas with guns that could fire up or down. Like the PB2Y, the Model 30 proposal of early 1938 had floats that could be retracted in flight after takeoff. The 190-foot span Model 30/XPB3Y-1 competed with rival Martin Model 170 Mars (originally Model 160B) (which was also powered by Duplex Cyclones but featured a slightly larger wingspan of 200 feet (60.96 meters) and six .50 caliber machine guns) and the Boeing 324 (also derived from the Boeing 314) designs for the SD116-19 requirement. On August 23, 1938, the Navy selected the Martin Model 170 over the Consolidated and Boeing designs, giving it the designation XPB2M-1. 

An artist's rendering of the Model 34/XPB3Y-1, late 1941

Although the Model 30 design of February 1938 had lost out to the Mars, protracted construction of the prototypes of the PB2M led Consolidated to propose a slightly scaled-down Model 30 in 1941 with the company designation Model 34. The overall design of the Model 34 was similar to the Model 30 design of 1938 as well as the PB2Y, and it had a wingspan of 169 feet (51.5 meters), a length of 104 feet 8 in (31.90 meters), a wing area of 2,600 square feet (241.80 square meters), a gross weight of 121,500 lb (55,111 kg), four Pratt & Whitney R-2800 Double Wasp radial piston engines, a top speed of 241 mph (388 km/h), and a range of 5,000 miles (8,045 km). A total of nine crewmen were to be carried, and armament comprised 20,000 lb (9,072 kg) of bombs and eight .50 caliber machine guns arranged in pairs in Erco nose and top ball turrets, along with twin waist blisters and a Convair-designed tail turret, while seal-sealing fuel tanks and armor protection were provided. The US Navy formally accepted the Model 34 design for full-scale development in late 1941, probably viewing it as assurance in case the Martin PB2M Mars ran into developmental problems, and on April 2, 1942, the aircraft was formally designated XPB3Y-1 and and one prototype (BuNo 32386) ordered the same day. A full-scale mockup of the XPB3Y-1 was inspected at the Consolidated Vultee factory in San Diego in early October, but a month earlier, on September 9, Isaac Laddon asked the US Navy to cancel the XPB3Y program because of his company's preoccupation with development of the B-32 Dominator, the B-36 Peacemaker, and PB4Y-2 Privateer. The Navy agreed, and the XPB3Y-1 program was axed on November 4. The cancellation of the XPB3Y-1 was perfectly timed, because the Martin PB2M Mars had taken flight a few months earlier, eventually being developed into the JRM cargo transport flying boat after the US Navy pronounced the patrol bomber flying boat concept obsolete.  

As a side note, in November 1941 Consolidated conducted design studies for a commercial version of the Model 34/XPB3Y-1 design conceived in September. The passenger flying boat variant of the Model 34 would have carried 77 passengers in day accommodations or 41 passengers in a night flight sleeper configuration, with a crew of 15 (including two stewards and one stewardess) and a maximum range of 3,700 miles (5,955 km), and comparisons of the commercial Model 34 were made with the Boeing 314 and Martin 130. However, like the XPB3Y-1, the Model 34 commercial flying boat design would never progress beyond the drawing board.

References:

Bradley, R., 2010. Convair Advanced Designs: Secret Projects from San Diego 1923-1962. North Branch, MN: Specialty Press.

Buttler, T., and Griffith, A., 2015. American Secret Projects 1: Fighters, Bombers, and Attack Aircraft, 1937 to 1945. Manchester, UK: Crecy Publishing.

Norton, B., 2012. American Bomber Aircraft Development in World War 2. Hersham, UK: Midland Publishing. ISBN 978-1-85780-330-3.

Wagner, R., 2004. American Combat Planes of the 20th Century: A Comprehensive Reference. Reno, Nevada: Jack Bacon & Co. ISBN 0-930083-17-2.