Yakovlev Yak-25 (1947)

Yakovlev OKB

Industry	Aerospace
Founded	1934
Headquarters	Moscow , Soviet Union
Products	Aircraft, including the Yakovlev Yak-25 prototype jet fighter

Template:Infobox aircraft

The Yakovlev Yak-25 represented an early Soviet jet fighter prototype developed by the Yakovlev OKB bureau. Initially, this designation referred to this particular aircraft before being assigned to a distinct interceptor model later on. Following an order from the Council of Ministers dated 11 March 1947, the design bureau was tasked with creating a straight-wing fighter analogous to the earlier Yak-19, but powered by a Rolls-Royce Derwent V turbojet. The resulting Yak-25 introduced several pioneering features for Soviet fighters, including a fully pressurized cockpit, climate control, a jettisonable canopy, and hydraulically operated airbrakes mounted on the fuselage.

Development

While retaining a similar overall configuration to the Yak-19, the Yak-25 incorporated several modifications. Its straight wings were marginally larger and significantly thinner, maintaining a consistent 9% thickness-to-chord ratio and utilizing laminar flow airfoils. The CAHI-designed flaps were hydraulically actuated. The vertical stabilizer differed by featuring a leading edge swept back at 40°, whereas the horizontal stabilizers were swept at 35°.

The Derwent V engine was mounted at the rear of the central fuselage in a manner akin to that on the Yak-19. Although the fuselage cross-section was non-circular and distinct from its predecessor, it incorporated a double bulkhead behind the wing that enabled removal of the rear fuselage section for engine access during maintenance or replacement. The landing gear arrangement closely mirrored that of the Yak-19.

The cockpit shared many design elements with earlier Yakovlev jets but featured pressurization achieved through an air-cycle system utilizing engine bleed air. The canopy slid rearwards and was powered for operation. Protection included a bullet-resistant front windshield measuring 57 mm in thickness and armor plating of 8 mm safeguarding the pilot's rear. The ejection seat improved upon that of the Yak-19 by incorporating a longer-stroke gun and leg restraints. Armament was upgraded to three NR-23 cannons, each supplied with 75 rounds.

Testing

Assigned the callsign "yellow 15" and marked with the number "2" on its airbrake rudder, the Yak-25-I underwent factory trials piloted by Anokhin from 31 October 1947 until 3 July 1948.

Subsequent flight evaluations demonstrated that the Yak-25 was straightforward to handle and delivered remarkable agility and performance for an aircraft with straight wings. However, it quickly became evident that the laminar flow airfoil used for the tail assembly was highly unsuitable, causing intense buffeting starting at speeds of 500 km/h (310 mph). According to test pilot L.L. Selyakov, the buffeting was so severe that he was violently shaken inside the cockpit, striking his head against the canopy, and all flight instrument needles detached. After replacing the tailplane section, handling significantly improved. Despite this, both competitors—the Lavochkin La-15 and the swept-wing MiG-15—offered superior capabilities. Ultimately, the MiG-15 was chosen for mass production while the La-15 saw limited manufacture totaling 235 units. Yakovlev never again produced a single-engine fighter surpassing those from OKB Mikoyan-Gurevich or OKB Lavochkin. Development of the Yak-25 was discontinued, though two prototypes continued to serve in testing and experimental roles.

Although known to Western observers during that era, the Yak-25 never received an ASCC reporting name or a USAF type designation.

Experimental work

Development efforts progressed with a redesign featuring a 35° swept wing, resulting in the Yak-30.

Yak-25E

The Yak-25E (Eksperimentalnyi) represented a modified Yak-25-II adapted for towing by a Tupolev Tu-4 strategic bomber. This modification responded to a Long Range Aviation headquarters initiative seeking a means to tow short-range jet fighters, codenamed Burlaki (barge hauler).

Production models were intended to be powered by Klimov RD-500 engines.

Concurrently, the U.S. Air Force was exploring a comparable concept under Project Tom-Tom. The American approach planned to utilize either a specially altered F-84 or an XF-85 Goblin parasite fighter. Early designs involved attaching two fighters to the bomber’s wingtips, while later proposals envisioned housing a parasite aircraft internally within the fuselage of a B-36.

Bibliography

• Gordon, Yefim. Early Soviet Jet Fighters. Hinkley: Midland Publishing, 2002. ISBN 1-85780-139-3
• Gordon, Yefim. OKB Yakovlev: A History of the Design Bureau and its Aircraft. Hinkley: Midland, 2005.
• Green, William & Swanborough, Gordon. The Complete Book of Fighters. London: Salamander Books, 1994. ISBN 1-85833-777-1
• Gunston, Bill. The Osprey Encyclopedia of Russian Aircraft 1875-1995. London: Osprey Publishing, 1995. ISBN 1-85532-405-9
• Gunston, Bill. Yakovlev Aircraft since 1924. London: Putnam Aeronautical Books, 1997. ISBN 1-55750-978-6