Gribovsky G-20

The Gribovsky G-20 (Russian: ГРИБОВСКИЙ Г-20) was an aerobatic trainer, designed in the USSR in the mid-1930s. Only one was built; re-engined in 1937, it was used to train many aerobatic pilots.

Design and development

The G-20 was a monoplane with a low wing of semi-elliptical plan, its greatest chord some way out from the roots. Unusually, the wing was braced from above with a pair of inverted V steel struts to a crash pylon within the enclosed forward cockpit. The wing had long, broad chord ailerons and manually operated flaps.^[1][2]

On its first flight, in 1935, and over its early career it was powered by a five cylinder Shvetsov M-11 radial engine, a Soviet design which originally produced 100 hp (75 kW),^[1][3] enclosed in a broad chord, helmeted cowling. In 1937 performance was improved with the installation of an uprated M-11 variant, the 150 hp (112 kW) M-11 Ye. Behind the engine the fuselage was deep and rounded below. Instructor and student were in tandem cockpits under continuous, multiframed glazing that merged into a raised rear upper fuselage.^[1] Its empennage was conventional, with elliptical, mid fuselage horizontal surfaces, the tailplane braced from the upper fuselage. The fin merged smoothly into the fuselage and carried a broad, unbalanced rudder which extended own to the keel. The tailplane was far enough forward that trailing edges of the elevators were ahead of the rudder hinge.^[2]

The G-20 had a tailwheel undercarriage. Its main wheels, mounted on slender cantilever legs, were enclosed in large, deep spats.^[1]

It flew for the first time in 1935. It came third in the first All-Union light competition but was initially underpowered for its aerobatic trainer rôle.^[2] Its performance was much enhanced by the more powerful M-11 Ye engine^[1] and subsequently some seventy pilots qualified on it.^[2]

Specifications (M-11 Ye engine)

Data from Gunston (1965), p.79 ^[1]

General characteristics

• Crew: Two
• Length: 6.3 m (20 ft 8 in)
• Wingspan: 9.7 m (31 ft 10 in)
• Wing area: 13.2 m² (142 sq ft)
• Airfoil: RII
• Empty weight: 620 kg (1,367 lb)
• Gross weight: 880 kg (1,940 lb)
• Fuel capacity: 100 kg (220 lb), including oil
• Powerplant: 1 × Shvetsov M-11 Ye 5-cylinder radial, 110 kW (150 hp)

Performance

• Maximum speed: 235 km/h (146 mph; 127 kn)
• Range: 400 km (249 mi; 216 nmi) :This and below refer to original M-11 engine
• Service ceiling: 3,870 m (12,697 ft)
• Time to altitude: 11.1 min to 2,000 m (6,562 ft)
• Take off distance: 190 m (623 ft)
• Landing speed: 70 km/h (43 mph)

References