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Yak-55
Yak-55
	Yak-55 performing low-level airshow aerobatics (pilot Mark Hensman)
General information
Type	Aerobatic aircraft
National origin	Soviet Union
Manufacturer	Yakovlev
History
First flight	28 May 1981

The Yakovlev Yak-55 is a single-seat aerobatic aircraft. Pilots flying the Yak-55 have won several world aerobatic championships.^[1]

Development

The 1976 World Aerobatic Championship was dominated by Soviet pilots, who finished first and second in the individual competition and also won the team and women's competitions in their Yakovlev Yak-50s.^[2] However, the Soviet pilots were also impressed by the performance of competing Western-built aircraft, which required less space than the Yak-50 to perform the same manoeuvers. A team in the Yakovlev design bureau, led by Sergei Yakovlev, and with V. P. Kondratiev and D. K. Drach as chief engineers, therefore set out to design an all-new dedicated aerobatic aircraft, unrelated to the Yak-50, which would be able to match the tight, low-speed style of Western aircraft.^[3]^[4]

The resulting design, the Yakovlev Yak-55, was a single-engined all-metal cantilever monoplane. The aircraft's wing is mounted midway up the fuselage and is of thick, symmetrical section to aid inverted flight. The pilot sits in an enclosed cockpit under a sliding teardrop canopy level with the trailing edge of the wing and with the seat below wing level. The powerplant is the same tractor configuration 360 horsepower (270 kW) Vedeneyev M14P engine driving a two-bladed V-530TA-D35 propeller, as used by the Yak-50, while the aircraft has a fixed undercarriage with titanium sprung main gear and tailwheel.^[3]^[4]

The prototype Yak-55 first flew in May 1981, was unveiled at the Moscow Tushino air show in August 1982 and displayed (but did not compete) at the 1982 World Aerobatic Championships. By this time, fashions in aerobatic flying had changed, with the high-energy aerobatics demonstrated by the Yak-50 back in fashion, leading to the Yak-55 being rejected by the Soviet team.^[3] The Yak-55 was therefore redesigned with new wings with shorter span, reduced area and a thinner but still symmetrical aerofoil section, giving an increased rate of roll and speed.^[4]^[5]^{[nb 1]} Series production finally began in 1985 at Arsenyev,^[6] with 108 aircraft being delivered by 1991.^[4]

In the late 1980s, work began on a revised version of the Yak-55, the Yak-55M, to meet demands from DOSAAF for an aircraft with further increased rates of roll, and to compete with new designs from the Sukhoi design bureau. The Yak-55M had a still smaller wing, which resulted in the required improvement in roll rate. It first flew in May 1989, entering production in 1990.^[7] 106 Yak-55Ms had been built by the end of 1993, with low-rate production continuing.^[8]

Operational use

The Soviet aerobatic team first used the aircraft in 1984 when they won the World Aerobatic Championship. That same year the Soviet woman's aerobatic team took first place flying the Yak-55, Kh. Makagonova winning individual gold.^[1]

The aircraft has been relatively free of Service Bulletins and Airworthiness Directives and has proved exceedingly effective in competition at all levels.^{[citation needed]} The obvious capabilities of the aircraft and its success in use, together with the relatively large numbers built (about 250) have meant that owners make relatively few modifications and that few are needed.^{[citation needed]}

Variants

Yak-55: Prototype/initial production aerobatic aircraft. Long-span wings.
Yak-55: Revised production version with reduced wingspan and area.
Yak-55M: Further revised version, with revised wings.
Technoavia SP-55M: The SP-55M is a development of the Yak-55M by V. P. Kondratiev, one of the designers of the Yak-55 with a redesigned vertical tail, composite-covered control surfaces, a deeper aft fuselage.^[9]^[10]
Yak-56: The Yak-56 was to be a two-seat trainer based on the Yak-55M, but with a low wing and retractable undercarriage. Power was to have come from a 300 hp VOKBM M-16 8-cylinder x-8 engine driving an AV-16 three-bladed propeller. The prototype was expected to fly in 1992, but delays in producing the engine meant that Yakovlev decided to produce the Yak-54 instead.^[11]^[12]

Boerboon & Coller Yak-110: The Yak-110 is an American-engineered twin-fuselage aircraft made from two Yak-55 airframes, fitted with a new wing center section supporting a single General Electric J85 turbojet engine in addition to the Vedeneyev M14P propeller engines. The idea was conceived in 2016 by pilot Jeff Boerboon and mechanic Dell Coller; Boerboon owns one of the original airframes, with the other one belonging to Chad Bartee. The plane is flown with the pilot in the left-side cockpit, and is the only three-engined aircraft to be certified for unlimited aerobatics as of 2023. Its first airshow was the Gunfighter Skies in 2018 at the Mountain Home Air Force Base in Idaho.^[13]^[14]

Operators

Lithuania

Lithuanian National Defence Volunteer Forces

Specifications (Yak-55M)

Data from Brassey's World Aircraft & Systems Directory 1999/2000 ^[15]

General characteristics

Crew: one
Length: 7.29 m (23 ft 11 in)
Wingspan: 8.10 m (26 ft 7 in)
Height: 2.80 m (9 ft 2 in)
Wing area: 12.8 m² (138 sq ft)
Aspect ratio: 5.13
Gross weight: 855 kg (1,885 lb) for aerobatics
Max takeoff weight: 975 kg (2,150 lb) for ferry flight
Powerplant: 1 × Vedeneyev M14P 9-cylinder radial engine, 268.5 kW (360.1 hp)

Performance

Maximum speed: 305 km/h (190 mph, 165 kn)
Stall speed: 100 km/h (62 mph, 54 kn) ^[16]
Never exceed speed: 450 km/h (280 mph, 240 kn)
Ferry range: 705 km (438 mi, 381 nmi)
g limits: +9, -6
Roll rate: 345 degrees per second
Rate of climb: 15.5 m/s (3,050 ft/min)

References

^ Gunston blames the redesign on the need to deal with structural failures of the original wing.^[4]

^ ^a ^b Gunston, 1997
^ Smith, Flight International, 21 August 1976, pp. 437–439.
^ ^a ^b ^c Gordon, Komissarov and Komissarov 2005, p. 290.
^ ^a ^b ^c ^d ^e Gunston and Gordon 1997, p. 209.
^ Gordon, Komissarov and Komissarov 2005, pp. 290–291.
^ Gordon, Komissarov and Komissarov 2005, p. 291.
^ Gordon, Komissarov and Komissarov 2005, pp. 291–292.
^ Gunston and Gordon 1998, pp. 209–210.
^ Gordon, Komissarov and Komissarov 2005, p. 292.
^ Jackson 2003, p. 424.
^ Gunston and Gordon 2005, p. 210.
^ Gordon, Komissarov and Komissarov 2005, pp. 294–295.
^ "Home". yak110.com.
^ Hal Bryan; "One Plus One Equals 110", EAA Sport Aviation, February 2019.
^ Taylor 1999, pp. 486–487.
^ 105 km/h (57 knots, 66 mph) inverted

Gordon, Yefim, Dmitry Komissarov and Sergey Komissarov. OKB Yakovlev: A History of the Design Bureau and its Aircraft. Hinkley, UK: Midland Publishing, 2005. ISBN 1-85780-203-9.
Gunston, Bill and Yefim Gordon. Yakovlev Aircraft since 1924. London, UK: Putnam Aeronautical Books, 1997. ISBN 1-55750-978-6.
Jackson, Paul. Jane's All The World's Aircraft 2003–2004. Coulsdon, UK: Jane's Information Group, 2003. ISBN 0-7106-2537-5.
Smith, Tony. "Lots of torque at Kiev". Flight International, 21 August 1976, pp. 437–439.
Taylor, Michael J. H. (editor). Brassey's World Aircraft & Systems Directory 1999/2000. London:Brassey's, 1999. ISBN 1-85753-245-7.
YAK-55M Operators Handbook