Bell XFM Airacuda

History of Bell XFM Airacuda

The XFM "Airacuda" was Bell Aircraft's first foray into military aircraft design. With this unique foray into bomber-destroyer, the product marks Bell as a different kind of aircraft manufacturer - the company will finally be supplying the Allies for some time with the WWII-era P-39 "Airacobra" with rear-mounted Engines and tricycle landing gear when front engine and "rear tug" designs became the norm.

While Airacuda ended up being Bell's abandoned, largely forgotten enterprise, it provided the company with a lot of expertise in the design and development process of military aircraft as it sought to secure potentially lucrative government contracts.

The Bell Airacuda was originally a pre-war design to meet the requirements of the United States Army Air Corps (USAAC) for a new twin-engine multi-role platform. As such, the type is expected to fulfill a variety of battlefield roles, including bomber destroyer, bomber escort, and ground attack.

Such designs already exist in some aviation services around the world - the Germans developed their Messerschmitt Bf 110 for the same purpose.

The new design will require inherent long-range capabilities to fight the enemy and structural tolerances to withstand fast, fighter-like movements and dives. Two engines provide the required power from a single unit, increasing the survivability of the crew and aircraft in harsh terrain. The workload will be shared between two or more crew members.

Bell engineers understood that the design should meet performance specifications, including a top speed of 300 mph, a service ceiling of 30,000 feet, and an inherent operating range of 3,000. It takes 10 minutes or less to ascend to 15,000 feet.

Work on Airacuda products began in 1936, and the bomber-destroyer/bomber-escort essentially evolved into a "heavy fighter" in WWII aircraft terminology. USAAC soon adopted Boeing B-17 "Flying Fortress" (1938) heavy bombers in an attempt to acquire an aircraft capable of escorting a large fleet of these new heavy aircraft over enemy airspace. While the bomber carries its own defensive weapon, that weapon actually allows only a limited defensive network to harass interceptors from the enemy. Accompanying escort fighters could break through bomber formations and engage these attackers directly, while the bombers continued to advance toward their targets. For bomber and destroyer roles, heavy artillery weapons would be used to take down large targets on these structures and make some good hits on their vital engine components or critical frame areas.

In addition, the new aircraft also considered the practice of dropping bombs on enemy bomber formations.

Engineers opted for a traditional twin-engine arrangement, with a pair of engines mounted in a single nacelle outside the fuselage, which are built into the plane's main wing elements. However, the design decision was to use the engines in a "propeller" arrangement, where the engines drive the respective propellers behind the trailing edges of the wings - thereby "pushing" the aircraft through the air. This is in contrast to the more traditional approach, in which the front engine drives the forward propeller assembly in a "pull rod" arrangement - which "pulls" the aircraft across the sky. The fuselage forms the central part of the aircraft and contains the main crew area, bomb bay, and various systems and subsystems. A single vertical tail is attached to the tail.

The front of the fuselage houses a glass nose for the cockpit crew. The total crew is 5, including pilot, co-pilot (also navigator), radio operator (also fuselage/hip/beam gunner) and two full-time gunners.

The mention of two dedicated gunners is particularly important, as their location is not in the actual hull. Instead, their workplaces are located in front of each engine nacelle - with the engines behind. Each manages a 37mm M4 gun mounted to the front of each nacelle, in addition to a coaxial 0.30 M1919 Browning machine gun that fires tracer rounds for aiming. The M4 gun was mounted on a hydraulic auxiliary mount for some trainable fire and fed from a five-round magazine.

For visibility, the leading section of each engine nacelle is glazed. Each gun carries 119 x M4 shells. Access to the fuselage is via a tunnel from the fuselage to the engine nacelles.

To power the aircraft, the engine initially chosen was an Allison V-1710-9 rated at 1,090 hp. Each is turbocharged and drives a three-bladed propeller unit via a 5-foot, 3-inch extended shaft. As mentioned earlier, the engine unit occupies the rear of each nacelle assembly.

The radio operator was also responsible for protecting the sides of the plane, so he had .50 caliber Browning M2 heavy machine guns on his platformone set on each side of the fuselage, each holding 600 rounds of ammunition. Originally, machine guns were installed through structural "bubbles" found on the sides of the hull.

The optional weapon for the Bomber Destroyer character is the 20 x 30 lb fragmentation bomb carried in the bomb bay. The destroyer was supposed to pass through a slower enemy formation and attempt a rather tricky direct strike against the group of moving targets, thereby delivering a lethal charge.

The first flight of the XFM-1 was on September 1, 1937. Due to the increased weight of the new aircraft, engineers replaced the original Allison V-1710-9 horsepower performance with 1,150 Allison V-1710-13s.

This optimistic and complex aircraft presented Bell personnel with various challenges during most of its active test life cycle - it was neither the test pilots who flew the machines nor the ground crew who were responsible for maintenance and repairs. popular.

In firing tests, it was found that the nacelle-mounted tracer gun was severely inadequate for the aiming requirements required by the M4 gun's larger, heavier 37mm projectile. Therefore, a special setup from Sperry Instruments was installed, adding a telescopic rangefinder and gyro-stabilized autopilot capabilities, allowing the pilot to fire the gun instead.

The cabin crew was retained, as they still needed to reload the five-round magazines into the cannon if needed.

Despite these early failures, USAAC allowed the XFM-1 product to continue in May 1938 when it awarded another contract for the XFM-1 product under the designation "YFM-1" for 13 tests airplane. The series of tests then continued until 1939, by which time the aircraft had been modified with an enlarged vertical stabilizer. Smaller spinners were fitted to each propeller unit, and the waist machine gun airbags were eliminated and modified for a more streamlined approach. The more advanced YFM-1 now features an Allison V-1710-23 engine rated at 1,150 horsepower with relocated turbochargers. Structurally, the skin of the aircraft is streamlined thanks to the use of flush rivets, which help limit the overall drag along each panel surface.

A retractable dorsal turret was armed with a .30 caliber machine gun, while another .30 caliber machine gun was operated through a ventral "tunnel" to help protect the critical lower rear quadrant of the aircraft. Updated bomb load to carry up to 600 pounds of traditional USAAC drop bombs.

The YFM-1 did not make its first flight until September 28, 1939about two years after the XFM-1's first flight. The second flight was damaged when one of the turbos disintegrated in flight, but the program continued to be developed by USAAC and was finally delivered to pilots for formal testing in February 1940. The YFM-1 standard was implemented by nine aircraft introduced in 1940. Three more three-wheeled undercarriages were delivered in October - Bell revisited this modern approach in their upcoming P-39 fighter jet. These aircraft carry the slightly modified designation "YFM-1A".

Two other Airacuda aircraft from the batch appeared, powered by Allison V-1710-41 engines rated at 1,090 hp, although they lacked turbochargers. These forms, designated "YFM-1B", evolved from the existing YFM-1 inventory.

Service trials began in 1941. One example has been lost during an emergency landing caused by a locked rudder - no deaths were recorded, but the fuselage was destroyed. Another fuselage was lost in an accident in January 1942.

American war planners lost interest in larger aircraft despite the work and funding of the Airacuda program. After Japan attacked Pearl Harbor in December 1941, the United States officially entered the war, and more pressing issues in the war required attention. Airacuda went through as much testing as possible, but its design was never completely reliableengine cooling remained an issue throughout its life cycle, requiring prototypes to be towed to launch sites rather than positioned on their own.

The propulsive propellers posed considerable danger to the departing crew if they were asked to disembark - they had to dodge the challenges of the rotating blades and vertical stabilizers to survive. Finally, despite the engine installed, the heavy aircraft simply couldn't perform as expected to keep up with the new B-17 bomber fleet -- it had a top speed of no more than 277 mph and a cruising speed of 244 mph (B -17G eventually reached a top speed of 287 mph).

Combined, this high-tech aircraft became an expensive acquisition and maintenance product that ultimately proved a failure for Bell and a forgotten product for USAAC.

The focus is back on single-engine combat mounts with inherent mobility. These were also eventually modified to carry bomb loads in the fighter-bomber role. USAAC eventually got a better twin-engine option, especially when the Lockheed P-38 Lightning came along. The P-38 enjoyed a distinguished wartime career, serving countless roles on the battlefield.

Compared to the Airacuda, it was certainly a more compact product, and in addition to the standard gun/machine gun weapon combination, it was piloted by only one crew member, carrying both bombs and missiles.

None of the Airacuda airframes survived the war and were scrapped in early 1942.

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