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Yak-25
Role	Interceptor aircraft
Manufacturer	Yakovlev OKB
First flight	2 November 1947
Introduced	n/a
Status	Project cancelled in 1948
Number built	1
Variants	Yakovlev Yak-30

The Yakovlev Yak-25 was a Soviet military aircraft, an early turbojet-powered interceptor aircraft designed by the Yakovlev OKB. The designation was later reused for a different interceptor design.

Tasked by the Council of Ministers in a directive issued on 11 March 1947, with producing a straight winged fighter powered by a Rolls-Royce Derwent V, OKB-115 swiftly produced the Yak-25.

Development

The Yak-25 closely followed the Yak-19 in layout if not in detail. The straight wings, though similar in planform, were of much thinner section (9% t/c), using laminar flow sections. The tail unit differed in being swept 45 degrees at the leading edge. The Derwent V engine was attached to the rear of the centre fuselage, with the rear fuselage being removed to gain access to the engine for removal or maintenance.

Flight tests followed quickly, and showed that the Yak-25 was easy to fly, had good performance, and manoueverability. Unfortunately it soon became clear that the laminar flow section used for the tail unit was totally unsuitable, with extremely severe buffetting setting in at 500 km/h (310 mph). Test pilot L.L. Selyakov reporting that the buffetting was so bad that he was thrown about the cockpit, banging his head on the canopy, and the needles fell off all the flight instruments.

To cure the buffetting the tail unit was replaced with one using a NACA 004 aerofoil section¹.

The Yak-25 blazed several trails as the first Soviet fighter with fully pressurised cockpit, air conditioning, jettisonable canopy, hydraulic airbrakes on the fuselage amongst others.

As Yakovlev were busy testing and improving the Yak-25, other OKB's were already in production with designs that eclipsed the straight-winged Yak-25, notably the Mikoyan-Gurevich MiG-15 and Lavochkin La-15. Development was halted, but two of the prototypes were used for test and development purposes. The second proototype being modified with a nose mounted telescopic probe to test the 'Burlaki' captive escort fighter programme. The third prototype was modified with a non-retractable 'Bicycle' type undercarriage for development of the Yak-50. Production aircraft would have used Klimov RD-500 engines

Further development, replacing the straight wing with one of 35° sweepback was undertaken as the Yak-30. The Yak-25 designation was later reused for a twin-jet heavy fighter in 1952.

Specifications

General characteristics

• Crew: 1
• Length: 8.66 m (28 ft 5 in)
• Wingspan: 8.88 m (29 ft 1 in)
• Height: m (ft)
• Wing area: 14.0 m² (151 ft²)
• Empty weight: 2,285 kg (5,027 lb)
• Max takeoff weight: 3,535 kg (7,777 lb)
• Powerplant: 1× Rolls-Royce Derwent V centrifugal compressor turbojet, 15.6 kN (3,500 lbf)

Performance

• Maximum speed: 982 km/h (530 knots, 610 mph)
• Range: 1,100 km (590 nm, 690 mi)
• Service ceiling 14,000 m (46,000 ft)
• Rate of climb: 37 m/s (7,260 ft/min)
• Wing loading: 163 kg/m² (34 lb/ft²)
• Thrust/weight: 0.45

Armament

• Guns: 3× 23 mm (0.906 in) Nudelman-Rikhter NR-23 cannon, 75 rounds/gun

See also

Comparable aircraft

• Dassault Ouragan
• Lavochkin La-15
  

Related lists

• List of military aircraft of the Soviet Union and the CIS
  

References

• Gordon, Yefim (2005). OKB Yakovlev: A History of the Design Bureau and its Aircraft. Hinkley: Midland. 

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