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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.

GA-21M
Cunningham-Hall GA-36 tandem seat, military version of GA-21M.
Role	Sports monoplane Type of aircraft
National origin	United States
Manufacturer	Cunningham-Hall Aircraft Corporation
Designer	Randolph Hall
First flight	1934
Number built	1

Design and development

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.[1][2]

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.[1]

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.[1]

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.[3][2]

The automated flaps worked well but were more complicated than, for example, Fowler flaps[2] 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.[4]

Specifications (GA-36)

Data from Aero Digest, March 1937[3]

General characteristics

• Crew: 2
• Length: 20 ft 0 in (6.10 m)
• Wingspan: 30 ft 0 in (9.14 m)
• Height: 6 ft 5 in (1.96 m)
• Wing area: 131 sq ft (12.2 m²)
• Empty weight: 1,490 lb (676 kg)
• Gross weight: 2,100 lb (953 kg)
• Fuel capacity: 29 US gal (24 imp gal; 110 l)
• Powerplant: 1 × Warner Super Scarab seven cylinder air-cooled radial piston engine, 145 hp (108 kW) at 2,050 rpm
• Propellers: 2-bladed Hamilton Standard, 8 ft (2.4 m) diameter

Performance

• Maximum speed: 158 mph (254 km/h, 137 kn)
• Cruise speed: 140 mph (230 km/h, 120 kn)
  
• Landing speed with-without flaps: 45–63 mph (72–101 km/h; 39–55 kn)
• Range: 450 mi (720 km, 390 nmi)
• Service ceiling: 14,000 ft (4,300 m)
• Rate of climb: 850 ft/min (4.3 m/s)

References

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