Role: Interceptor "Bomber destroyer"
Manufacturer: Bell Aircraft
Designed by: Bob Woods
First flight: 1 September 1937
Introduced: 23 February 1940
Retired: 1942
Primary user: United States Army Air Corps
Number built: 13
Program cost: $3.6 million USD
Unit cost: $219,000 USD

The United States Bell YFM-1 Airacuda was the first military aircraft produced by the Bell Aircraft Corporation. Originally designated the "Bell Model 1," the Airacuda first flew on 1 September 1937. The Airacuda was marked by bold design advances and considerable flaws that eventually grounded the plane.

The Airacuda was Bell Aircraft's answer for a "bomber destroyer" aircraft. Although it did see limited production, and one fully operational squadron was eventually formed, only one prototype and 12 production models were ultimately built, in three slightly different versions.

Design and development

In an effort to break into the aviation business, Bell Aircraft created a unique fighter concept touted to be "a mobile anti-aircraft platform" as well as a "convoy fighter." Created to intercept enemy bombers at distances beyond the range of single-seat fighter interceptors, the YFM-1 (Y, service test; F, fighter; M, multiplace) was an innovative design incorporating many features never before seen in a military aircraft, as well as several never seen again. Utilizing a streamlined, "futuristic" design, the Bell Airacuda appeared to be "unlike any other fighters up to that time."

According to Major Alexander De Seversky's 1942 book, Victory Through Air Power, the Bell Airacuda "represents a great engineering achievement. But its designation as 'convoy fighter' is erroneous, since that requires different disposition of armament. With its maximum firepower directed forward, it really offers a preview of an effective long-range interceptor fighter."

A forward-firing M4 37mm cannon with an accompanying gunner was mounted in a forward compartment of each of the two engine nacelles. Although capable of aiming the cannons, the gunner's primary purpose was simply to load them with the 110 rounds of ammunition stored in each nacelle.

The crew of five included the pilot and gunners; a copilot/navigator who doubled as a fire-control officer, using a Sperry Instruments "Thermionic" fire control system originally developed for anti-aircraft cannon combined with a gyro-stabilised and an optical sight to aim the weapons; and a radio operator/gunner stations ine the rear fuselage, armed with a pair of machine guns in waist blisters for defense against attack from the rear.

Production list

• Class 26 is USAAC parlance for "not economical to repair."

Picture - Bell YFM-1 during testing

Design flaws

The Airacuda was plagued with problems from the start. The lofty performance estimates were unobtainable as, despite its sleek looks, the Airacuda was heavy and was slower than most bombers. In the event of interception by enemy fighters, the Airacuda was not maneuverable enough to dogfight, while the meager 600 lb (272 kg) bomb load was of little use in the intended fighter-bomber role. Even the centerpiece, main 37 mm cannon armament, were perilous to use. The cannons had a tendency to fill the gun nacelles with smoke whenever fired and, additionally, fears persisted as to how the gunners would escape in an emergency, with the propellers directly behind them. An emergency bailout would have required both propellers to be feathered, though additional provision was made with the use of explosive bolts on the propellers to jettison them in the event of a bailout.

The Allison V-1710-41 engines, though relatively trouble-free in other types, had no additional cooling systems. Like many pusher designs, they were prone to overheating. On the ground, the aircraft had to be towed to and from the runway and could only be started when the Airacuda was able to take off immediately. Even in the air it was not uncommon to experience overheating problems. Although designed for turbo-supercharging, the first flights were made with V-1710-9 carbureted engines that only delivered 1,000 hp (745.70 kW) each. Despite the long five ft shaft extensions, there were no problems with this feature. When the turbos were fitted to the later YFM-1, they were plagued by cranky turbo regulators that backfired continuously. An explosion during a September 1939 test flight made it apparent that the teething engine troubles would not be solved easily.

Additionally, Marshall Wainwright notes that other sources indicate the first eight aircraft were to originally have been powered by Allison V-1710-13 engines fitted with GE Type B-6 turbosuperchargers. These aircraft were eventually delivered with improved V-1710-23(D2) engines. Wainwright further states that two of the YFM-1 airframes were changed on the production line to accept the V-1710-41 without turbosupercharging, becoming YFM-1Bs. This is noted in a contract change dated 19 October 1939 which shows that aircraft 34-489 and 38-490 had their turbos, all associated ducting, and controls removed and V-1710-41(D2A) "Altitude Rated" engines installed instead. The (D2A) was essentially a -23 with higher supercharger gear ratios (8.77:1 versus 6.23:1), which allowed the motor to develop around 1,090 hp up to 13,200 ft ASL. They used the same ratings and components as the Altitude Rated V-1710-33(C15) Allison fitted to the original Curtiss XP-40. Allison was paid $1,690 to modify each engine.

Initial flight testing by Lt. Ben Kelsey proved the plane virtually impossible to control on a single engine, as the aircraft would go into an immediate spin. Problems with stability in pitch were also encountered, and had to be corrected by reducing power. Test pilot Erik Shilling described his experiences in a later book, Destiny: A Flying Tiger's Rendezvous With Fate as:

Flying the Bell Airacuda was a new experience for me, since it was the first pusher aircraft I'd ever flown. Its handling characteristics were foreign to anything I had ever had my hands on. Under power it was unstable in pitch, but stable with power off. While flying straight and level, if a correction in pitch was required, a forward push on the control resulted in the airplane wanting to pitch over even more. Pitch control became a matter of continually jockeying the controls, however slightly, even when the aircraft was in proper trim. The same applied if pulling back on the control. It would tend to continue pitching up, requiring an immediate corrective response. The same happened in a turn with power off, the Bell became stable in pitch. This was fortunate because during approach and landing, it was very stable, and a nice flying airplane."

Flying the Bell Airacuda was a new experience for me, since it was the first pusher aircraft I'd ever flown. Its handling characteristics were foreign to anything I had ever had my hands on. Under power it was unstable in pitch, but stable with power off. While flying straight and level, if a correction in pitch was required, a forward push on the control resulted in the airplane wanting to pitch over even more. Pitch control became a matter of continually jockeying the controls, however slightly, even when the aircraft was in proper trim. The same applied if pulling back on the control. It would tend to continue pitching up, requiring an immediate corrective response. The same happened in a turn with power off, the Bell became stable in pitch. This was fortunate because during approach and landing, it was very stable, and a nice flying airplane."

The Airacuda was also saddled with a complex and temperamental electrical system and was the only aircraft ever built to rely on an independent auxiliary power unit (APU) to power both engine fuel pumps, as well as all aircraft electrical systems. Systems usually powered by an aircraft's engines were instead powered by the single generator. The generator, with its own supercharger, was located in the belly of the aircraft. In the event of a failure (and they occurred frequently), the crew was instructed to begin immediate emergency restart procedures as the aircraft basically shut down. When the APU failed, the pilot had "NO fuel pressure, NO vacuum, NO hydraulic pressure, NO gear, NO flaps and NO ENGINES".

Accidents

Despite the aircraft's many faults only two were lost in accidents. The seventh aircraft (38-492) was on its final test flight from the Buffalo factory prior to delivery to the Air Corps when pilot John Strickler, a Bell pilot and engineer, and co-pilot Brian Sparks, who was Bell's chief test pilot at the time, encountered problems recovering from a deliberate spin attempt which was part of the test flight profile. Despite every effort to emerge from the spin the aircraft wouldn't respond, and it appeared that the rudder had locked. Co-pilot Sparks shut down the engines and waited for the propellers to come to a stop before bailing out. Because of the tandem seating it was necessary for Sparks to exit the aircraft first, and in doing so he struck the empennage, breaking his legs - and freeing the rudder. Strickler decided to stay with the aircraft and attempt an emergency landing. By this time the plane had lost sufficient altitude that there was not time to restart the engines. Strickler put the Airacuda down hard in a farmer's field, and walked away unhurt. The Airacuda was so badly damaged it had to be scrapped.

All three Airacuda with tricycle landing gear encountered problems and were damaged at one time or another. The most serious accident occurred to 38-497 on a flight from Chanute Field, Illinois, and Keesler Field, Mississippi, when a broken oil line started an in-flight fire. The cause of the broken line appeared to be serious airframe vibration encountered during the flight. With no way of extinguishing the fire both the pilot and crew chief agreed to bail out. Unfortunately the pilot was killed when his parachute failed to deploy (he may have struck the tail while bailing out). This was the only fatality to occur during the flying of Airacudas. The accident investigation report stated "inherent defects in design caused constant maintenance difficulties and the flying of this type has been very limited."

Operational history

Despite these problems, one fully operational Airacuda squadron was eventually assembled, and operated from 1938 until 1940. Funds were appropriated, but never released, for the purchase of two groups of Airacudas. Continuing problems gave the machines a reputation as "hangar queens". Towards the end of the type's operational life, the aircraft were flown primarily for photo opportunities and always accompanied by a chase plane for safety. Eventually the decision was made to disperse the aircraft to various airfields to give pilots an opportunity to add the unusual plane to their log books. Airacudas were sent at various times to Langley Field, Virginia; Maxwell Field, Alabama; Hamilton Field, California; and Wright Field, in Dayton, Ohio. YFM-1 38-488 was displayed at the 1940 World's Fair in New York, finished in the markings of the 27th Pursuit Squadron. During this time the aircraft saw limited flight time, as few pilots were interested in adding the unusual plane to their logs.

Several proposals were made to modify the Aircudas to give them operational status, including modifying the airframe and adding more powerful powerplants, but all were eventually rejected. In early 1942, despite fears of enemy bomber attacks against which the Airacuda was intended, the aircraft were stricken from inventory, and all nine surviving airframes were flown by ferry crews to a training facility at Chanute Field, Illinois where the planes were assigned to the 10th Air Base Squadron to be used for ground crew instruction. Before the end of 1942 all Airacudas were scrapped.

Variants

The prototype, known as the XFM-1, incorporated a tailwheel, side "blister" ports, and a smooth, rounded canopy. This is the best known, and most produced version. An updated version called the YFM-1A eliminated the side blisters and added externally mounted radiators and turbo-superchargers. Produced in 1940, the final version designated YFM-1B, was slightly larger, had slightly less powerful Allison engines and incorporated a tricycle landing gear. The canopy was redesigned, with a flat forward windshield. A rearward-facing belly gunner's position was also added. The resulting aircraft was roughly the size of a Douglas B-18 bomber. Three YFM-1Bs were produced in 1939 before production was finally terminated.

XFM-1 (Model 1)Prototype powered by two 1150hp V-1710-13 engines, one built. YFM-1 (Model 7)Development aircraft powered by two 1150 V-1710-23 engines and fitted with 37mm cannon in wing nacelles, nine built two later converted to YFM-1B. YFM-1A (Model 8)Development aircraft with tricycle landing gear, three built. YFM-1B YFM-1 re-engined with 1090hp V-1710-41 engines, two converted from YFM-1. YFM-1C (Model 17) - proposed variant not proceeded with.

Reproductions

Since there are no surviving examples of the actual aircraft, the Oakland Air Museum at Oakland International Airport in Oakland, California houses perhaps the most detailed attempt to recreate the Airacuda. Following extensive research done in conjunction with Air Force archives in the 1990s, Bay Area resident Robert Winchell created and drew plans from scratch to build a detailed radio control model of the Airacuda. All of the fabrication, down to skin rivets and instrumentation systems, were hand crafted by Winchell, resulting in a singularly detailed and faithful recreation of the Airacuda. The Museum now houses the model, donated by Winchell in the early part of this century.

A die-cast toy reproduction of the first variant XFM-1 was produced by Hubley Toys in the late 1930s. Today this is one of the most sought-after of Hubley's die-cast toy aircraft. Wyandotte Tin Toys of Wyandotte, Michigan produced a pressed tin toy loosely based on the Airacuda in the late 1930s. This toy was also included in a set containing a string and magnetic bomb release attached to the airplane. RarePlanes models in England produced a 1/72 scale vacuform kit of the XFM-1 in the late 1970s. A model manufacturer located in Czechoslovakia has produced good-quality cast resin and metal models of each of the three Airacuda variants. These models are indicated as 1/72 scale, though appear closer to 1/100 scale, and are the most accurate models of the Airacuda to date.

In 2007 the Czech model manufacturer Valom released a series of 1/72 scale injection molded kits of all variants of the Airacuda. These kits are very accurate and well detailed with resin and photo-etched metal parts. Kit number 72015 includes markings for the YFM-1 that appeared at the New York World's Fair in June 1940.

Specifications (XFM-1)

Data from

General characteristics

Crew: 5 (pilot, copilot/navigator, radio operator/gunner, two gunners)
Length: 44 ft 10 in (13.67 m)
Wingspan: 69 ft 10 in (21.29 m)
Height: 13 ft 7 in (4.14 m)
Wing area: 684 sq ft (63.5 m)
Airfoil: NACA 23018/NACA 23009
Empty weight: 13,376 lb (6,067 kg)
Gross weight: 17,333 lb (7,862 kg)
Fuel capacity: 400 US gallons (1,500 l; 330 imp gal)
Powerplant: 2 x— Allison V-1710-9 liquid-cooled turbosupercharged V-12, 1,090 hp (810 kW) each
Propellers: 3-bladed

Performance

Maximum speed: 277 mph (446 km/h; 241 kn)
Cruise speed: 244 mph (212 kn; 393 km/h)
Range: 2,600 mi (2,259 nmi; 4,184 km)
Service ceiling: 30,500 ft (9,296 m)
Rate of climb: 1,480 ft/min (7.5 m/s)

Armament

Guns: 2 x 37 mm cannon (110 rpg) and 2 x .30-calibre machine guns in front of nacelles; 2 x .50-calibre machine guns (600 rpg) in side blisters
Bombs: 20 x 30-pound (14 kg) fragmentation bombs in wing bays

Comparable aircraft

Curtiss XP-71
Messerschmitt Bf 110
Vickers 414

Bibliography

Andrade, John (1979). U.S. Military Aircraft Designations and Serials since 1909. Hinckley, England: Midland Counties Publications. ISBN 0-904597-22-9.
Angelucci, Enzo (1987). The American Fighter from 1917 to the present. New York: Orion Books. ISBN 0-517-56588-9.
de Seversky, Alexander Procofieff (1942). Victory through Air Power. New York: Simon and Schuster. ASIN B0007DP2B2.
Lednicer, David "The Incomplete Guide to Airfoil Useage" Champaign, Illinois: UIUC Applied Aerodynamics Group http://www.ae.illinois.edu/m-selig/ads/aircraft.html. Retrieved 2010-04-23
Norton, Bill (2008). U.S. Experimental & Prototype Aircraft Projects: Fighters 1939-1945. North Branch, Minnesota: Specialty Press. pp. 122-125. ISBN 978-1-58007-109-3.
Plummer, Pat. "The Victorious Vees." Wings Vol. 27, no. 4, August 1997.
Taylor, Michael J.H., ed (1989). Jane's Encyclopedia of Aviation. London: Studio Editions. ISBN 0-517-69186-8.
Wainwright, Marshall. "Airacuda! Pts. 1 & 2." Air Classics, Volume 44, numbers 6 & 7, May & June 2008 (respectively).
Winchester, Jim (2005). "Bell YFM-1 Airacuda". The World's Worst Aircraft. London: Amber Books. ISBN 1-904687-34-2.

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Source: WikiPedia