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The Yakovlev Ya-21, (aka UT-21, No.21 or No.25), was a single-seat high-speed sport aircraft / fighter-trainer designed and built in the Soviet Union in the late 1930s.

Ya-21
Role	single-seat fighter-trainer / high-speed sport aircraft Type of aircraft
National origin	USSR
Manufacturer	OKB Yakovlev
First flight	September 1937
Number built	1
Developed from	Yakovlev UT-1

Design and development

The Ya-21 was derived from the Yakovlev UT-1, in similar fashion to the Yakovlev AIR-18, by replacing the Shvetsov M-11 radial with an imported 220 hp (160 kW) Renault 6Q-01 inverted 6-cylinder in-line engine. The rear cockpit was enclosed with an aft-sliding canopy, a fixed trousered and spatted undercarriage with spring steel tail-skid was fitted, as well as split flaps and a fixed, forward firing, synchronised 7.62mm ShKAS machine gun in the forward fuselage decking. Plans for re-engining the Ya-25 with a Kossov MG-31F 9-cylinder radial engine were cancelled, due to changing priorities of the customer.[1][2]

The sole Ya-21 was converted into the No.25 prototype by substituting the imported Renault with a 220 hp (160 kW) Voronezh MV-6 (Renault Bengali copy). The cockpit also differed in having opaque side panels and no sliding hood, with a deeper windshield to house the gunsight.[1]

Production of both the Ya-21 or No.25 was not implemented due to the Yakovlev OKB focusing on combat aircraft, such as the Yakovlev BB-22 and Yakovlev I-26.[1]

Variants

Ya-21

(aka UT-21, No. 21) The sole prototype ( of two intended) fighter-trainer / high-speed sport aircraft powered by a 220 hp (160 kW) Renault 6Q-01 engine.

No.25

The Ya-21 converted to have open cockpit and powered by a 220 hp (160 kW) Voronezh MV-6 engine.

Specifications (Ya-21)

Data from OKB Yakovlev,[1] Yakovlev aircraft since 1924[2]

General characteristics

• Crew: 1
• Length: 6.4 m (21 ft 0 in)
• Wingspan: 7.8 m (25 ft 7 in)
• Height: 2.05 m (6 ft 9 in)
• Wing area: 9.58 m² (103.1 sq ft)
• Airfoil: Göttingen 387
• Empty weight: 611 kg (1,347 lb)
• Max takeoff weight: 831 kg (1,832 lb)
• Fuel capacity: 120 kg (260 lb) / 170 l (45 US gal; 37 imp gal) fuel; 12 kg (26 lb) oil
• Powerplant: 1 × Renault 6Q-01 6-cylinder inverted air-cooled in-line piston engine, 160 kW (220 hp)
• Propellers: 2-bladed fixed pitch wooden propeller, 2.1 m (6 ft 11 in) diameter

Performance

• Maximum speed: 290 km/h (180 mph, 160 kn) at sea level 322 km/h (200 mph; 174 kn) at 2,000 m (6,600 ft)
• Landing speed: 85 km/h (53 mph; 46 kn) with flaps, 90 km/h (56 mph; 49 kn) no flaps
• Cruise speed: 290 km/h (180 mph, 160 kn)
• Range: 715 km (444 mi, 386 nmi)
• Service ceiling: 7,000 m (23,000 ft)
• Time to altitude: 1,000 m (3,300 ft) in 2.7 minutes, 3,000 m (9,800 ft) in 7.5 minutes
• Take-off run: 150 m (490 ft)
• Landing run: 190 m (620 ft)

Armament

• 1x fixed forward firing synchronised 7.62mm ShKAS machine gun

References

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