Among the scores of experimental fighter aircraft developed before the Second World War, hands down one of the most unusual designs was the Bell Model 1, later known as the Aracuda.
.jpg)
An Airacuda in flight
The Airacuda was a large, twin-engine, pusher configured, fighter aircraft, the only one the US would even build. It had its origin in a September 1935 request from the USAAC for a heavy interceptor, able to engage long-range strategic bombers effectively. The result was a large, heavily armed aircraft, though not one that would be able to adapt to the march of technology.
Interestingly, the fairly new company, Bell Aviation, won the prototype contract to design and built this new
interceptor over Lockheed on June 4th, 1936.
The immediately apparent feature of the Airacuda is the large engine nacelles located on each wing. They each held a single gunner with his gyro-stabilized 37mm cannon and a .30 caliber machine gun mounted in the front, and a turbosupercharged Allison V-1710-13 engine in the back.
Turbochargers (exhaust-driven compressors) and superchargers (mechanically-driven compressors) were a major desire of military aircraft designers as early as the 1920s, since they were able to compress the ambient air at higher altitudes and provide equivalent performance at higher altitudes to what aircraft would get closer to sea level. This was a difficult task for a fighter, as turbosuperchargers were heavy and required a lot of ducting which added weight and required a lot of space. But bombers would have the space to carry them easily, which required fighters to have the same if they were to have a hope of effective interception.
The pilot and navigator were positioned in tandem in the fuselage, with a rear gunner/radioman behind them to operate the blister mounted .50 caliber machine guns. The total crew was five, three gunners, the navigator, and the pilot.
There were several interesting features that Bell added to the Airacuda, some of which were even good ones. The door for the pilot and navigator could slide down and be used as a ladder for the two crewmen, doing away with the need for a separate ladder. On the other hand, there was only one electrical system in the aircraft that the engines powered, that being a 50 amp generator attached to the left engine. Everything else that was electrically powered by the engines on other aircraft, such as fuel pumps, hydraulics, vacuum systems, and the gyros for the guns were all powered by a dedicated Auxilary Power Unit that was itself powered by a separate turbosupercharged gas engine, fed from both of the turbos on the Allison engines. This APU had the unfortunate tendency to stall in flight, which would effectively shut down the entire aircraft. It could be restarted in flight, but it was still a dangerous feature for such an innovative aircraft.
Another issue was the basic configuration of the aircraft, with the engines and propellers located in the pusher configuration. If the crew needed to evacuate the aircraft for whatever reason, it would take a full six seconds for the engines to stop and feather. The engines also tended to overheat while at low speeds, so they sometimes had to be towed to the runway before startup to keep from overheating the engines.
The flaps and landing gear were tied together and could be set to three positions, takeoff, fly, and land. The landing gear would extend first, then the flaps. So the pilot would have to flip the circuit breaker to start the landing gear down, then flip it off before the flaps. Then when on their final landing approach, they would flip it back on to extend the flaps all the way. Once they were on the ground they would set it to fly, which would retract the flaps.
The intended use of the Airacuda was to fly behind a formation of hostile bombers and engage them with the 37mm cannons, which would keep the Airacuda out of range of the defending gunners who would generally be armed with .30 caliber machine guns. While the men in the nacelles could fire their guns if required, their primary job was to keep the guns loaded. The navigator had a set of controls, but he also had the belly-mounted periscope and sighting system to fire all of the guns with. Each gun could traverse through a 25-degree cone, allowing them to be aimed accurately once the pilot had the plane pointed in the general direction of an enemy aircraft.
An Airacuda being assembled.
The XFM-1 (Experimental, Fighter, Multiplace) flew for the first time on September 1st, 1937 with wooden mockup guns as the real ones were not yet produced. The craft was a taildragger, and the landing gear only retracted halfway into the nacelles.
Turbochargers (exhaust-driven compressors) and superchargers (mechanically-driven compressors) were a major desire of military aircraft designers as early as the 1920s, since they were able to compress the ambient air at higher altitudes and provide equivalent performance at higher altitudes to what aircraft would get closer to sea level. This was a difficult task for a fighter, as turbosuperchargers were heavy and required a lot of ducting which added weight and required a lot of space. But bombers would have the space to carry them easily, which required fighters to have the same if they were to have a hope of effective interception.
The pilot and navigator were positioned in tandem in the fuselage, with a rear gunner/radioman behind them to operate the blister mounted .50 caliber machine guns. The total crew was five, three gunners, the navigator, and the pilot.
There were several interesting features that Bell added to the Airacuda, some of which were even good ones. The door for the pilot and navigator could slide down and be used as a ladder for the two crewmen, doing away with the need for a separate ladder. On the other hand, there was only one electrical system in the aircraft that the engines powered, that being a 50 amp generator attached to the left engine. Everything else that was electrically powered by the engines on other aircraft, such as fuel pumps, hydraulics, vacuum systems, and the gyros for the guns were all powered by a dedicated Auxilary Power Unit that was itself powered by a separate turbosupercharged gas engine, fed from both of the turbos on the Allison engines. This APU had the unfortunate tendency to stall in flight, which would effectively shut down the entire aircraft. It could be restarted in flight, but it was still a dangerous feature for such an innovative aircraft.
Another issue was the basic configuration of the aircraft, with the engines and propellers located in the pusher configuration. If the crew needed to evacuate the aircraft for whatever reason, it would take a full six seconds for the engines to stop and feather. The engines also tended to overheat while at low speeds, so they sometimes had to be towed to the runway before startup to keep from overheating the engines.
The flaps and landing gear were tied together and could be set to three positions, takeoff, fly, and land. The landing gear would extend first, then the flaps. So the pilot would have to flip the circuit breaker to start the landing gear down, then flip it off before the flaps. Then when on their final landing approach, they would flip it back on to extend the flaps all the way. Once they were on the ground they would set it to fly, which would retract the flaps.
The intended use of the Airacuda was to fly behind a formation of hostile bombers and engage them with the 37mm cannons, which would keep the Airacuda out of range of the defending gunners who would generally be armed with .30 caliber machine guns. While the men in the nacelles could fire their guns if required, their primary job was to keep the guns loaded. The navigator had a set of controls, but he also had the belly-mounted periscope and sighting system to fire all of the guns with. Each gun could traverse through a 25-degree cone, allowing them to be aimed accurately once the pilot had the plane pointed in the general direction of an enemy aircraft.
The XFM-1 (Experimental, Fighter, Multiplace) flew for the first time on September 1st, 1937 with wooden mockup guns as the real ones were not yet produced. The craft was a taildragger, and the landing gear only retracted halfway into the nacelles.
Specifications: XFM-1
Allison V-1710-13, 1150 hp at takeoff, 1000 hp at 20,000 feet
Dimensions:
Wingspan: 69' 10''
Length: 44' 10''
Height: 13' 7''
Wing Area: 684^2 feet
Weight:
Empty: 13,376 lb
Gross: 17,333 lb
400-800 gallons of fuel
Performance:
Top Speed: 271 mph @ 20,000 Feet
At Sea Level: 335 mph
Cruising Speed: 244 mph
Landing Speed: 77 mph
Service Ceiling: 30,500 Feet
Normal Range: 800 Miles
Maximum Range: 1,590 Miles
Test versions, known as the YFM-1 (Service test, fighter, multiplace), were ordered in May 1938. At first, they were supposed to mount the same turbosupercharged Allisons as the XFM-1, but altitude rated ones were substituted after the turbo exploded on the VFM-1's first flight on September 28th, 1939. Other differences from the XFM included the engine's radiators being moved onto the wings instead of the nacelles, two M2 .50 caliber guns in different side mounts, a single M1919 .30 caliber gun in a top-mounted retractable turret (360-degree traverse), and another in a 180-degree traverse belly turret. Twenty bombs ranging from 30 pounds to 17 pounds could be carried on the fuselage. The carried ammunition consisted of 110 37 mm shells, 1,200 .50 caliber rounds, and 1,000 .30 caliber rounds.
Colt started delivering the 37 mm M4 cannons in April 1939. Each cannon weighed 213 pounds, had a rate of fire of between 140 and 150 rounds per minute, and fed from the left side via the 30 round endless belt magazine called the M6. This is the same cannon that the P-39 Airacobra had mounted to fire through the propeller hub. Each gun would have had 55 rounds of 37mm available, most likely high explosive shells, though armor-piercing was also available.
Nine YFM-1s were accepted from March to July 1940, one of which crashed before it could be delivered. The YFM-1As produced in August were identical except for the addition of a nosewheel, and the main landing gear folded in flush with the wings. Only three of these were produced. The YFM-1B was a YFM-1 fitted with V-1710-41 engines, of which only two were made.
.jpg)
A YFM-1B
Specifications: YFM-1
Allison V-1710-13, 1150 hp at takeoff, 1000 hp at 20,000 feet
Dimensions:
Wingspan: 70'
Length: 46'
Height: 12' 9''
Wing Area: 600^2 feet
Weight:
Empty: 13,630 lb
Gross: 18,000 lb
Maximum: 19,000 lb
400-800 gallons of fuel
Performance:
Top Speed: 270 mph @ 12,600 Feet
Landing Speed: 77 mph
Service Ceiling: 30,500 Feet
Normal Range: 940 Miles
Maximum Range: 1800 Miles
.jpg)
A YFM-1A
Despite these shortcomings, there were only two major accidents that resulted in the loss of the aircraft. The seventh YFM-1 went out of control during a spin test, and the rudder locked. The crew (Pilot: John Strickler, Copilot: Brian Sparks) shut down the engines and the copilot bailed out first due to the tandem arrangement. He struck the tail once out of the aircraft, managing to unlock the rudder, but he broke his legs in the process. With the rudder functioning, the pilot was able to make an unpowered landing in a farmer's field, but the aircraft was so badly damaged that it had to be scrapped.
More tragic was when an oil fire in a YFM-1A forced the crew to bail out. The pilot was killed when his parachute failed to deploy, possibly after striking the tail.
Despite its novel design, when compared to the contemporary Curtiss XP-37 (another turbosupercharged fighter), the Airacuda was the inferior aircraft in terms of airspeed, rate of climb, and service ceiling.
Worse, the Airacuda was too slow to justify itself as an interceptor against most medium and heavy bombers of the period, and it was not nimble enough to compete with lighter, single-engine fighters. It wouldn't even work as an escort for long range bombers, as its armament was poorly laid out to defend against interceptors, being concentrated mostly in the forward aspect.
Despite its novel design, when compared to the contemporary Curtiss XP-37 (another turbosupercharged fighter), the Airacuda was the inferior aircraft in terms of airspeed, rate of climb, and service ceiling.
Worse, the Airacuda was too slow to justify itself as an interceptor against most medium and heavy bombers of the period, and it was not nimble enough to compete with lighter, single-engine fighters. It wouldn't even work as an escort for long range bombers, as its armament was poorly laid out to defend against interceptors, being concentrated mostly in the forward aspect.
In service, the Airacuda was something of a hanger queen due to the aforementioned maintenance issues. They were distributed to several airfields around the US to give pilots something different to fly, though most did not. By 1942, all of the Airacudas were allocated for ground crew instruction and by March of 1942, they had all been scrapped.
Sources:
https://web.archive.org/web/20090227082948/http://home.att.net/~Berliner-Ultrasonics/aviatn-1.html#FM1
http://www.planesandpilotsofww2.webs.com/Prototypes.html - Description of Technical Issues and Flying the Airacuda.
American Combat Planes: Third Enlarged Edition. 1982. Wagner, Ray - Development History and Technical Data.
Photos are from Wikipedia Commons
Comments
Post a Comment