Heinkel He 51
|He 51W seaplane|
|First flight||May 1933|
|Retired||1939 (Luftwaffe) 1952 (Spanish Air Force)|
The Heinkel He 51 was a German single-seat biplane which was produced in a number of different versions. It was initially developed as a fighter, a seaplane variant and a ground-attack version were also developed. It was a development of the earlier He 49.
Design and development
In 1931, Heinkel recruited the talented aircraft designers Walter and Siegfried Günter. Their first major design for Heinkel was the Heinkel He 49. While this was officially an advanced trainer, in fact it was a fighter. The first prototype, the He 49a, flew in November 1932, and was followed by two further prototypes, the He 49b, with a longer fuselage, and the He 49c, with a revised engine.
The He 51 was a conventional single-bay biplane, with all-metal construction and fabric covering. It was powered by a glycol-cooled BMW VI engine, with an armament of two 7,92 mm (.323 in) machine guns mounted above the engine.
The He 51 was intended to replace the earlier Arado Ar 65, but served side-by-side with the slightly later Ar 68. The He 51 was outdated the day it entered service, and after an initial run of 150 production fighters, the design was switched into the modified He 51B, with approximately 450 built, including about 46 He 51B-2 floatplanes, and then finally a further 100 He 51C light ground-attack plane.
On 6 August 1936, six of the He 51s were delivered to Spain to fight in the Spanish Civil War along with the Nationalists. Initial operations were successful, with the Heinkels meeting and defeating a number of older biplanes of the Spanish Republican Air Force, with two Nieuport Ni-52 fighters, a Breguet 19 and a Potez 54 destroyed on 18 August 1936, the first day of operations by Spanish-flown He 51s. Deliveries continued as the hostilities increased, with two Nationalist squadrons equipped by November, and the Legion Condor forming three squadrons of 12 aircraft each manned by German "volunteers".
This time of superiority was short lived, with the arrival of large numbers of modern aircraft from the Soviet Union, including the Polikarpov I-15 biplane and new Polikarpov I-16 monoplane, together with the Tupolev SB bomber, which was 110 km/h (70 mph) faster. The He 51 proved unable to protect the Legion Condor's bombers, forcing it to switch to night operations, while also unable to intercept the much faster SB. The He 51 was therefore withdrawn from fighter duty and relegated to the ground-attack role by both the Legion Condor and the Nationalists. It was replaced in the fighter role by the Fiat CR.32 in the rebel Nationalist Air Force, with the Legion Condor receiving Messerschmitt Bf 109s from April 1937 to allow it to operate successfully in fighter operations.
While a failure as a fighter, the Heinkel proved successful as a ground-attack aircraft, being used by Wolfram von Richthofen to develop the close support tactics which were used by the Luftwaffe in World War II. It continued in use as a ground attack aircraft for the remainder of the Civil War, although losses were heavy. After the war the 46 surviving aircraft would be joined by another 15 new builds, and serve in the utility role in Spain until 1952.
The He 51 continued in front-line service with the Luftwaffe until 1938, with it remaining in service as an advanced trainer for the first few years of World War II.
- He 49a
- First prototype, with short fuselage.
- He 49b
- Second prototype, with stretched fuselage. Tested as both landplane and floatplane.
- He 49c
- Third prototype, with revised, glycol-cooled engine installation.
- He 51a
- Fourth prototype, with new vertical tail, revised wings and undercarriage, new radiator.
- He 51A-0
- Pre-production aircraft; 9 built.
- He 51A-1
- Initial production version; 150 built.
- He 51B-0
- Pre-production aircraft, structurally strengthened; 12 built.
- He 51B-1
- Production version of B-0; 450 built.
- He 51B-2
- Single-seat floatplane fighter, reconnaissance version; 46 built.
- He 51B-3
- High-altitude version.
- He 51C-1
- Light ground-attack version; 100 built, 79 sent to Spain to equip the Legion Condor and Nationalist air force.
- He 51C-2
- Improved version of C-1, with revised radio equipment; 21 built.
Specifications (He 51B-1)
Data from Warplanes of the Luftwaffe 
- Crew: 1
- Length: 8.40 m (25 ft 6¾ in)
- Wingspan: 11.00 m (36 ft 1 in)
- Height: 3.20 m (10 ft 6 in)
- Wing area: 27.20 m² (292.6 ft²)
- Empty weight: 1,460 kg (3,212 lb)
- Loaded weight: 1,900 kg (4,180 lb)
- Powerplant: 1 × BMW VI 7,3Z liquid-cooled V12 engine, 559 kW (750 hp)
- Maximum speed: 330 km/h (178 kn, 205 mph)
- Cruise speed: 280 km/h (151 kn, 174 mph)
- Range: 570 km (308 nmi, 354 mi)
- Service ceiling: 7,700 m (25,256 ft)
- Wing loading: 69.9 kg/m² (14.3 lb/ft²)
- Power/mass: 0.29 kW/kg (0.18 hp/lb)
- Climb to 1,000 m (3,300 ft): 1.4 min 
- Climb to 6,000 m (19,700 ft): 16.5 min 
- Guns: 2 × 7.92 mm MG 17 machine guns in nose; 500 rpg
- Bombs: 6 × 10 kg (22 lb) bombs (C-1)
Aircraft of comparable role, configuration and era
- Mondey 1996, p. 81.
- Green and Swanborough 1994, p. 295.
- Mondey 1996, p. 80.
- Donald 1994, p. 96.
- Green and Swanborough 1988, p. 15.
- Hooton 1994, pp. 121–122.
- Green and Swanborough 1988, p. 20.
- Hooton 1994, p. 125.
- Hooton 1994, p. 127.
- Hooton 1994, p. 126.
- Green and Swanborough 1988, p. 21.
- Green and Swanborough 1988, pp. 21–22.
- Green and Swanborough 1988, p. 23.
- Green and Swanborough 1988, p.14.
- Green and Swanborough 1988, p. 17.
- Green and Swanborough 1988, p. 19.
- Donald, David, ed. Warplanes of the Luftwaffe. London: Aerospace, 1994. ISBN 1-874023-56-5.
- Green, William and Gordon Swanborough. "The Cadre Creator ... Heinkel's Last Fighting Biplane". Air Enthusiast No. 36, May–August 1988, pp. 11–24. ISSN 0143-5450.
- Green, William and Gordon Swanborough. The Complete Book of Fighters. New York: Smithmark, 1994. ISBN 0-8317-3939-8.
- Hooton, E.R. Phoenix Triumphant: The Rise and Rise of the Luftwaffe. London: Arms & Armour Press, 1994. ISBN 1854091816.
- Mondey, David. The Concise Guide to Axis Aircraft of World War II. London: Chancellor, 1996. ISBN 1-85152-966-7.
- Taylor, John W.R. "Heinkel He 51". Combat Aircraft of the World from 1909 to the Present. New York: G.P. Putnam's Sons, 1969. ISBN 0-425-03633-2.
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