Bell YFM-1 Airacuda

Materializing many innovative features and designed by Robert J. Woods, the Airacuda was a five-seat long-range bomber destroyer. It was powered by two engines in a pusher configuration and it accommodated two gunners in forward extensions of the engine nacelles. Those crew members were provided with wing crawlways in order to reach the main fuselage in the event that it was needed to evacuate the nacelle gun positions.
The first prototype XFM-1 was powered by two 1150hp Allison V-1710-13 12-Cylinder liquid-cooled engines which drove three-blade propellers via 64-in (1.62m) extension shafts and flew for the first time on 1st September 1937.
Twelve further evaluation models were ordered, nine as YFM-1 and other three YFM-1As which was different just in having tricycle undercarriage. The engines kept being two 1150hp Allison V-1710-23s, but three of them were fitted with the V-1710-41 of 1090hp as YFM-1Bs. The 12 YFMs were delivered to the United States Army Air Corps between February and October 1940 and they were armed with one 37mm T-9 cannon in each gun nacelle with 110 rounds each, plus one 0.3in (7.62mm) M2 machine gun with 500 rounds in each of the retractable dorsal turret and ventral tunnel positions and one 0.5in (12.7mm) M2 gun firing from each of the port and starboard beam positions. Twenty 30lb (13.6Kg) bombs could be fitted internally.
During flight testing performed by Bell, many problems and flaw were encountered with two of them being lost to accidents and most of them being damaged. The most accident occurred to an YFM-1A on a flight between Chanute Field, Illinois and Keesler Field, Mississippi when a broken oil line sparked a fire due to some serious fuselage vibration encountered during the flight. As there wasn't any way of extinguishing the fire, both pilot and crew chief agreed to bail out. The pilot was killed as his parachute didn't open. That was the only fatality occurred during the testing of the Airacudas.
In spite of all those problems, a full operation Airacuda squadron was assembled and operated from 1938 to 1940. Funds were appropriatted but never released for the purchase of two further groups of Airacudas. However, as the continued problems persisted, the aircraft received the reputation of "hangar queens". Near the end of the aicraft's operational life they were flown mainly for photo oportunities and always accompanied by a chase plane for security purposes. It was decided eventually to disperse the aircraft through various airfields to give pilots the chance to add the unusual aircraft to their log books, so they were sent to Langley Field, Virginia, Maxwell Field, Alabama, Hamilton Field, California and Wright Field, in Dayton, Ohio. One of them was displayed at the 1940 New York World Fair finished with the colours of the 27th Pursuit Squadron but during this time the aicraft saw limited flight time as pilots weren't interested in flying the unusual aircraft.
Many plans were made to modify them to make them operational, including the modification of the airframe and adding more powerful engines but all of them were rejected. In early 1942 despite the danger of enemy attacks against American bombers, the Airacuda was rejected.

Sources:
1. Salamander Books - The Complete Book of Fighters
2. https://en.wikipedia.org/wiki/Bell_YFM-1_Airacuda