Oddball, Experimental, or One-off

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The Cunningham-Hall GA-21 was an American two-seat monoplane design to compete for the Guggenheim Safe Aircraft Competition in 1934. Its distinguishing feature was full span flaps which could be manually or automatically adjusted. The GA-36 was a military version of it with tandem, rather than side-by-side seating.

 

The GA-21M was all metal aircraft apart from the fabric covering of parts of the wing, otherwise metal-covered, and the control surfaces. The low-set wings were rectangular in plan out to rounded tips and had a high lift section. Both flaps and ailerons filled the whole straight part of the trailing edge, so the latter only opened upwards.

 

Apart from its unusual flaps and lateral control the GA-21M was conventional. Powered by a 145 hp (108 kW), seven cylinder Warner Super Scarab radial engine, it had a round-sectioned, metal-skinned, monocoque fuselage. An open cockpit over the forward wing seated two side-by-side. The tailplane was mounted just above the fuselage on the fin and could be trimmed; essentially triangular in plan, it carried rounded elevators. A rounded rudder reached down to the keel.

 

The GA-21Ms had conventional, tailwheel landing gear with the landing wheels ahead of the leading edge within aircraft fairings that also enclosed the legs.

 

The GA-36 was a 1936 military trainer rebuild of the Ga-21M. This included a revised, tandem cockpit and more trouser-like landing gear fairings, making it 15% heavier.

 

The automated flaps worked well but were more complicated than, for example, Fowler flaps and more expensive to construct. Simpler systems were preferred and the sole GA-21M/36 was sold in 1941, stripped of major components and dumped until the 1980s when it was recovered, fully restored and put on display at the Niagara Aerospace Museum.

 

GA-21M

 

GA-36

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The Martin XB-51 was an American trijet ground-attack aircraft. It was designed in 1945 and made its maiden flight in 1949. It was originally designed as a bomber for the United States Army Air Forces under specification V-8237-1 and was designated XA-45. The "A" ground-attack classification was eliminated the next year, and the XB-51 designation was assigned instead. The requirement was for low-level bombing and close support. The XB-51 lost out in evaluation to the English Electric Canberra which — built by Martin — entered service as the Martin B-57 Canberra.

 

This unorthodox design, first flying on 28 October 1949, was fitted with three General Electric J47 engines - an unusual number for a combat aircraft - two underneath the forward fuselage in pods, and one at the extreme tail with the intake at the base of the tailfin. The innovative, variable incidence wings, swept at 35° and with 6° anhedral, were equipped with leading edge slats and full-width flaps. Spoilers gave most of the roll control and undersized ailerons provided feel for the pilot. The combination of variable incidence and slotted flaps gave a shorter takeoff run. Four 954 lb (4.24 kN) thrust Rocket-Assisted Take Off (RATO) bottles with a 14-second burn duration could be fitted to the rear fuselage to improve takeoff performance. Spectacular launches were a feature of later test flights.

 

The main landing gear consisted of dual wheel sets in tandem in the fuselage, similar to the Boeing B-47 Stratojet, with outrigger wheels at the wingtips (originally proved on a modified Martin B-26 Marauder named "Middle River Stump Jumper"). The XB-51 was a large but aerodynamically "clean" design which incorporated nearly all major systems internally. The aircraft was fitted with a rotating bomb bay, a Martin trademark; bombs could also be carried externally up to a maximum load of 10,400 lb (4,700 kg), although the specified basic mission required only a 4,000 lb (1,814 kg) bombload. Eight 20 mm cannon mounted in the nose would have been installed in production aircraft.

 

Crew was a pilot under a "fighter"-type bubble canopy and a Short-range navigation and bombing system (SHORAN) operator/navigator in a compartment located lower than and to the rear of the cockpit (only a small observation window was provided). Both crew members were provided with a pressurized, air conditioned environment, equipped with upward-firing ejection seats. The XB-51 was the first Martin aircraft equipped with ejection seats, these being of their own design.Number built - 2.