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Heinkel He 51

Germany · Interwar (1919–1938)

Heinkel He 51 — Fixed Wing
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The Heinkel project bureau developed the He 51 in 1932-1933; the prototype first flew in summer 1933. About 725 He 51s were built between 1934 and 1937 at Heinkel Warnemünde + Arado Brandenburg + Erla Maschinenwerk + Fieseler Kassel. The aircraft entered Luftwaffe service in April 1935 and saw combat use in the Spanish Civil War (1936-1939) before being eclipsed by the monoplane Messerschmitt Bf 109.

The He 51 used a BMW VI 7.3Z V-12 liquid-cooled engine (750 hp). Maximum speed 330 km/h, range 570 km, service ceiling 7,700 m. Armament: 2 × MG 17 7.92 mm machine guns. The aircraft was a conventional biplane fighter — already obsolescent at its 1933 first flight as the Soviet Polikarpov I-16 (1933) and British Hawker Hurricane (1935) and German Bf 109 (1935) were ushering in the monoplane fighter era.

He 51 service in the Spanish Civil War (Condor Legion 2.J/88) was unsuccessful — the He 51 was outclassed by Soviet Polikarpov I-15 + I-16 fighters supplied to Republican forces. After Spanish Civil War losses, surviving He 51s were transferred to ground-attack roles and the type was retired from front-line Luftwaffe service by 1938. Spanish Air Force used surviving He 51s in trainer roles through the late 1940s. About 1 He 51 airframe survives in 2026 at the Deutsches Technikmuseum Berlin.

For Kids — a shorter, friendlier version

The Heinkel He 51 was Germany's first front-line fighter after the 1935 rearmament. It first flew in 1933 and entered Luftwaffe service in April 1935. About 725 He 51s were built between 1934 and 1937. The He 51 fought in the Spanish Civil War from 1936 to 1939 with the German Condor Legion.

The He 51 is 25 feet long with a 36-foot wingspan, smaller than a school bus. One BMW VI 12-cylinder engine made 750 horsepower. Top speed is 205 mph, faster than most cars on a highway. Two MG 17 machine guns were the only weapons.

The He 51 was a biplane fighter, already outdated when it first flew in 1933. The same year, the Soviet Polikarpov I-16 became the first monoplane fighter to enter service. By 1935, the Hawker Hurricane and Messerschmitt Bf 109 were starting to fly. The biplane era was ending fast.

In Spain, the He 51 was outclassed by Soviet I-15 and I-16 fighters supplied to the Republican side. After heavy losses, surviving He 51s were turned into ground-attack aircraft. The Luftwaffe retired the He 51 from front-line service by 1938. The Bf 109 took over as Germany's main fighter.

Fun Facts

  • The He 51 was Germany's first front-line fighter after 1935 rearmament.
  • About 725 He 51s were built between 1934 and 1937.
  • The He 51 is 25 feet long, smaller than a school bus.
  • Top speed is 205 mph, faster than most cars on a highway.
  • The He 51 fought in the Spanish Civil War from 1936 to 1939.
  • Soviet I-16 fighters outclassed the He 51 in Spain.
  • The Bf 109 replaced the He 51 as Germany's main fighter.

Kids’ Questions

Why was a biplane outdated?

Biplanes have two wings stacked, which gives lots of lift but lots of drag. By 1933, engineers learned that single-wing (monoplane) designs were faster and more agile if built right. The Soviet I-16 (1933), Hawker Hurricane (1935), and Bf 109 (1935) were all monoplanes that easily beat biplanes in air combat. The He 51 was on the wrong side of this change.

What was the Condor Legion?

The Condor Legion was a German volunteer unit that fought for the Nationalist side in the Spanish Civil War. From 1936 to 1939, German pilots flew He 51s, Bf 109s, He 111 bombers, and other aircraft in Spain. The German leader Hitler used the war to test new aircraft and tactics. Many lessons learned in Spain helped Germany prepare for World War II.

What happened after Spain?

After heavy losses to Soviet fighters in Spain, the Luftwaffe retired He 51s from fighter duty by 1938. Surviving He 51s were used as ground-attack aircraft, dropping bombs on tanks and troops. By 1940, all He 51s were retired completely. Spanish forces kept some He 51s in service into the early 1940s.

Variants

He 51A (basic fighter)
Initial 1935 production. ~150 built.
He 51B (improved fighter)
Improved-engine variant. ~450 built. Most-numerous variant.
He 51C (ground-attack)
Ground-attack variant with bomb racks. ~80 built. Late-war role after fighter obsolescence.

Notable Operators

Luftwaffe (1935-1938)
Principal operator. ~600 He 51s in front-line service before replacement by Bf 109.
Condor Legion (Spain 1936-1939)
About 50 He 51s served Condor Legion 2.J/88 in Spanish Civil War. Outclassed by Soviet-supplied Republican fighters.
Spanish Nationalist / Spanish Air Force
Spanish-built He 51s by CASA (about 100). Used in Spanish Civil War + postwar trainer role through 1947.

Frequently Asked Questions

Why was the He 51 quickly obsolete?

It was a biplane in an era when monoplane fighters were displacing biplanes. The He 51 (1933 first flight, 330 km/h) was outpaced by the Messerschmitt Bf 109 (1935 first flight, 470 km/h) within 2 years. Spanish Civil War combat against Soviet Polikarpov I-16 monoplane fighters demonstrated that biplanes had become uncompetitive in fighter-vs-fighter combat. The Luftwaffe retired the He 51 from front-line service by 1938.

How did the He 51 perform in Spain?

Poorly. Condor Legion 2.J/88 He 51s were outclassed by Soviet-supplied Polikarpov I-15 + I-16 fighters serving Republican forces. He 51 losses prompted the Condor Legion to switch to ground-attack roles + accept early-production Messerschmitt Bf 109s for fighter roles. The He 51's combat record in Spain validated Luftwaffe transition to monoplane fighters.

How many He 51s were built?

About 725 airframes 1934-1937 at Heinkel + Arado + Erla + Fieseler plants in Germany, plus ~100 Spanish CASA-built airframes. Combined production ~825.

Sources

See Also