Heinkel He 274
Encyclopedia

The Heinkel He 274 was a German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....

heavy bomber
Heavy bomber
A heavy bomber is a bomber aircraft of the largest size and load carrying capacity, and usually the longest range.In New START, the term "heavy bomber" is used for two types of bombers:*one with a range greater than 8,000 kilometers...

 developed during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, purpose-designed for high-altitude bombing with pressurized crew accommodation.

He 177 ancestry

On 17 November 1938, the owner of the Heinkel
Heinkel
Heinkel Flugzeugwerke was a German aircraft manufacturing company founded by and named after Ernst Heinkel. It is noted for producing bomber aircraft for the Luftwaffe in World War II and for important contributions to high-speed flight.-History:...

 aviation firm, Ernst Heinkel
Ernst Heinkel
Dr. Ernst Heinkel was a German aircraft designer, manufacturer, Wehrwirtschaftführer in the Third Reich, and member of the Nazi party. His company Heinkel Flugzeugwerke produced the Heinkel He 178, the world's first turbojet aircraft and jet plane, and the Heinkel He 176, the first rocket aircraft...

, requested permission from the RLM
Reich Air Ministry
thumb|300px|The Ministry of Aviation, December 1938The Ministry of Aviation was a government department during the period of Nazi Germany...

 that two of the requested eight prototype airframes for the nascent He 177 heavy bomber project, specifically the V3 and V4 airframes, be set aside for a trial installation of four separate powerplants. Herr Heinkel had foreseen that an individually engined version of his bomber would someday be preferred, quite unlike the requested fitment of the coupled pairs of Daimler-Benz DB 601
Daimler-Benz DB 601
|-See also:-Bibliography:* Mankau, Heinz and Peter Petrick. Messerschmitt Bf 110, Me 210, Me 410. Raumfahrt, Germany: Aviatic Verlag, 2001. ISBN 3-92550-562-8.* Neil Gregor Daimler-Benz in the Third Reich. Yale University Press, 1998-External links:...

 inverted V12 engines, each known as a DB 606, which ended up being fitted to all of the eight He 177 V-series prototypes at the request of the RLM, and the Luftwaffe High Command
Oberkommando der Luftwaffe
The Oberkommando der Luftwaffe was the air force High Command of the Third Reich.Air Force Commanders-in-Chief* Reich Marshal Hermann Göring * Field Marshal Robert Ritter von Greim -History:...

, with the concerned government agencies citing the desire for a dive-bombing capability to be present even with a heavy-bomber-sized offensive warplane, something Ernst Heinkel vehemently disagreed with.

By April 1939, interest in developing a high-altitude version of the He 177 had arisen, and on April 27, 1939, the first proposal for such an aircraft was presented to Heinkel by his firm's engineering staff. The aircraft was intended to have a reduced crew manifest of three people, with a fully pressurized nose compartment for the pilot and bombardier/forward gunner, and separate pressurized tail gun emplacement. The result, in December 1940, was the specification for the He 177A-2 high altitude bomber design, with a four-person crew manifest (pilot, bombardier, forward gunner and tail gunner) in the two specified pressurized compartments, and powered by the regular A-series pair of DB 606 coupled engines. The defensive armament had been reduced to a trio of Ferngesteuert-Lafette FL 81Z remote gun turrets, each with a twin-barrel MG 81
MG 81 machine gun
The MG 81 was a German belt fed 7.9 mm machine gun, used in flexible installations in World War II Luftwaffe aircraft, replacing the older drum magazine-fed MG 15....

 armament installation each in an upper nose mount, forward dorsal and (as part of the Bola casemate-style gondola under the nose) forward ventral location each, and a single MG 131 machine gun
MG 131 machine gun
The MG 131 was a German 13 mm caliber machine gun developed in 1938 by Rheinmetall-Borsig and produced from 1940 to 1945...

 in an He 177A-1-style, pressurized manned flexible tailgun emplacement.

The Heinkel firm had been working on practical cockpit pressurization methods and hardware for both the A-2, and slightly later A-4 versions (identical to the A-2, except for the fitting of a pair of the later DB 610 coupled engine "power systems") from 1940 through the late summer of 1941, when the DB 610-powered A-4's pressurized cockpit in provisional form, almost identical in external appearance to the standard "Cabin 3" He 177A-series production cockpit, was ready for tests and development.

By October 1941, a more developed "He 177H" specification for a high-altitude Heinkel-designed heavy bomber had emerged from the proposed A-2 and A-4 coupled-engine designs, with the intent of carrying a 2,000 kg (4,410 lb) bombload over a maximum range of some 3,000 km (1,895 mi), and accepted by the RLM for the first time, an individual four-engine installation was being considered for any He 177-based bomber airframe, with a quartet of either BMW 801
BMW 801
The BMW 801 was a powerful German air-cooled radial aircraft engine built by BMW and used in a number of German military aircraft of World War II. The engine's cylinders were in two rows of seven cylinders each, the bore and stroke were both 156 mm , giving a total capacity of 41.8 litres...

 or DB 603 engines among the choices of powerplants being specified, with the same sort of reduced-armament defensive weapon format as the A-2 and A-4 were intended to have.

A pair of the early He 177A-0 pre-production prototypes were redesignated the He 177 V10 and V11 for the purposes of high-altitude trials, and were to be the first to test the A-4 pattern pressurized cockpit design at altitude, but only the V11 was actively used for the needed research, and managed to achieve an altitude of 9,200 m (30,200 ft) with complete success on August 9, 1943, with further tests continuing through October of that year, before both the V10 and V11 were grounded in April 1944.

In February 1943, any further work on the coupled-engined A-2 and A-4 designs was halted by order of the RLM, as the four-engined He 177H high-altitude design had gained in importance from that time, evidenced by Reichsmarschall Hermann Goering's derisive "welded-together engines" complaints in August 1942, regarding the He 177 A-series unending engine problems from the choice of the DB 606 and 610 "power systems" for the A-series operational aircraft.

Development

The first proposal for what would become the He 274 started with six examples of what had been known as the He 177H, which were requested from Heinkel as early as mid-October 1941, all to have four individual engines, and intended to use what were essentially production He 177A-3 fuselages mated to longer-wingspan, four-engined wings. These proposed aircraft were shortly thereafter officially given the project number 8-274 by the RLM, and due to the heavily preoccupied Heinkel factory design offices and aircraft manufacturing facilities, this new "He 274" high-altitude bomber was to have its prototypes built in France by the Societe des Usines Farman (SAUF) firm in Suresnes
Suresnes
Suresnes is a commune in the western suburbs of Paris, France. It is located from the center of Paris. The nearest communes are Neuilly-sur-Seine, Puteaux, Rueil-Malmaison, Saint-Cloud and Boulogne-Billancourt...

.

Two He 274 prototypes were ordered built in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 by the Farman
Farman
Farman Aviation Works was an aeronautic enterprise founded and run by the brothers; Richard, Henri, and Maurice Farman. They designed and constructed aircraft and engines from 1908 until 1936; during the French nationalization and rationalization of its aerospace industry, Farman's assets were...

 Brothers and four pre-production prototypes by Heinkel
Heinkel
Heinkel Flugzeugwerke was a German aircraft manufacturing company founded by and named after Ernst Heinkel. It is noted for producing bomber aircraft for the Luftwaffe in World War II and for important contributions to high-speed flight.-History:...

 at its Rostock-Marienehe facility. SAUF at Suresnes, began their prototype development.

Work on the requested half-dozen He 274 prototype airframes was leveraged off Heinkel aircraft production at AIA Breuget, Toulouse
Toulouse
Toulouse is a city in the Haute-Garonne department in southwestern FranceIt lies on the banks of the River Garonne, 590 km away from Paris and half-way between the Atlantic Ocean and the Mediterranean Sea...

 where French factories produced Heinkel components and Junkers
Junkers
Junkers Flugzeug- und Motorenwerke AG , more commonly Junkers, was a major German aircraft manufacturer. It produced some of the world's most innovative and best-known airplanes over the course of its fifty-plus year history in Dessau, Germany. It was founded there in 1895 by Hugo Junkers,...

 aero engines. French production facilities at Toulouse for Heinkel aircraft were severely damaged by Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...

(RAF) air raids on the night of 5/6 March 1944 and again by the US Eighth Air Force
Eighth Air Force
The Eighth Air Force is a numbered air force of the United States Air Force Global Strike Command . It is headquartered at Barksdale Air Force Base, Louisiana....

 on 25 June 1944. This frustrated completion of the French prototypes as the design work on what would emerge as the Heinkel-designed entry in the trans-Atlantic range Amerika Bomber
Amerika Bomber
The Amerika-Bomber project was an initiative of the Reichsluftfahrtministerium, the Nazi Germany Air Ministry, to obtain a long-range strategic bomber for the Luftwaffe that would be capable of striking the continental United States from Germany, a range of about 5,800 km...

strategic heavy bomber design competition, the He 277, was slowly progressing at the Heinkel-Sud facility in Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...

. The "Typenblatt" drawings for the never-completed He 277, with a heavy design influence for the fuselage's geometry from the smaller Heinkel He 219
Heinkel He 219
The Heinkel He 219 Uhu was a night fighter that served with the German Luftwaffe in the later stages of World War II. A relatively sophisticated design, the He 219 possessed a variety of innovations, including an advanced VHF-band intercept radar...

 night fighter, however show that it had also adopted many features from the He 274, especially its twin tail
Twin tail
A twin tail is a specific type of vertical stabilizer arrangement found on the empennage of some aircraft. Two vertical stabilizers — often smaller on their own than a single conventional tail would be — are mounted at the outside of the aircraft's horizontal stabilizer...

 empennage design.

Characteristics

Major differences between the He 274 and the He 177 A were abandonment of the twin coupled engine arrangement in favor of four independent DB 603 A-2 engine units, an extended rear fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...

 with a pressurized double glazed cockpit
Cockpit
A cockpit or flight deck is the area, usually near the front of an aircraft, from which a pilot controls the aircraft. Most modern cockpits are enclosed, except on some small aircraft, and cockpits on large airliners are also physically separated from the cabin...

 of nearly identical external appearance to the 177A's "Cabin 3" nose, longer wingspan
Wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...

, a twin tail fin empennage
Empennage
The empennage , also known as the tail or tail assembly, of most aircraft gives stability to the aircraft, in a similar way to the feathers on an arrow...

 and a more conventional set of twin-wheel main undercarriage, abandoning the cumbersome four-strut main gear system of the He 177A.

The He 274 dispensed with coupled engines, providing room for the installation of DVL exhaust driven TK 11B turbo-supercharger
Twincharger
Twincharger refers to a compound forced induction system used on some piston-type internal combustion engines. It is a combination of an exhaust-driven turbocharger and an engine-driven supercharger, each mitigating the weaknesses of the other...

s.

The He 274 also featured a pressurized compartment
Cabin pressurization
Cabin pressurization is the pumping of compressed air into an aircraft cabin to maintain a safe and comfortable environment for crew and passengers when flying at altitude.-Need for cabin pressurization:...

 for a crew of four, this employing double walls of heavy-gauge alloy, hollow sandwich-type glazing and inflatable rubber seals, a pressure equivalent to that at 2,500 m (8,200 ft) being maintained at high altitude. Largely unnecessary defensive armament was restricted to a single forward-firing 13 mm (.51 in) caliber MG 131 machine gun
MG 131 machine gun
The MG 131 was a German 13 mm caliber machine gun developed in 1938 by Rheinmetall-Borsig and produced from 1940 to 1945...

 and remotely controlled dorsal and ventral Fernbedienbare Drehlafette FDL 131Z gun turret
Gun turret
A gun turret is a weapon mount that protects the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in many directions.The turret is also a rotating weapon platform...

s each containing a pair of MG 131s and with the dorsal turret operated from a slightly offset plexiglass domed sighting station in the roof of the flight deck, with the ventral unit aimed from the rear of the ventral Bola gondola. The powerplants selected were the same Daimler-Benz DB 603
Daimler-Benz DB 603
|-See also:-Bibliography:* Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9* Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1989. ISBN 0-517-67964-7...

A Kraftei "power-egg" unitized engine installations, complete with their He 219-style annular radiators, that were placed on the wings of the He 177B prototypes, but with the added TK 11 turbochargers, one per engine, for better power output at high altitude.

The significance of this design is that had this aircraft entered production and been used in operations over England it would have been impossible for Allied fighters to intercept over the target, owing to its extreme high altitude performance.

Abandoned prototypes

Construction of the two prototype
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...

s, the He 274 V1 and V2 did not commence until 1943. They were to have been built in France by SAUF at Suresnes, France, but the prototypes were not completed in time. The He 274 V1 was being readied for flight testing at Suresnes in July 1944 when the approach of Allied
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 forces necessitated the evacuation of Heinkel personnel working on the project. Minor difficulties had delayed the flight testing and transfer of the aircraft to Germany, and orders were therefore given to destroy the virtually completed prototype. Only minor damage was actually done to the airframe of the He 274 V1, and repairs were begun after the Allied occupation.

The He 274 V1 was repaired by Ateliers Aéronautiques de Suresnes
Ateliers Aéronautiques de Suresnes
Ateliers Aéronautiques de Suresnes was a French aircraft manufacturer that existed for a short while after World War II. Operating from the Farman Aviation Works factory near Paris, its most notable achievement was completing the two examples of the Heinkel He 274 left unfinished by the...

(AAS) and used by the Armée de l'Air
French Air Force
The French Air Force , literally Army of the Air) is the air force of the French Armed Forces. It was formed in 1909 as the Service Aéronautique, a service arm of the French Army, then was made an independent military arm in 1933...

(French Air Force) for several years as a high-altitude research plane. It was renamed the AAS 01A. The He 274 V2 was eventually completed as the AAS 01B, complete with the Hirth 2291 turbochargers.

Eventually the V2 flew exactly two years (on December 27, 1947) after the AAS 01A. By this time, the AAS organization had been absorbed into the French SNCASO (Société nationale des constructions aéronautiques du sud-ouest, or commonly, Sud-Ouest) aviation conglomerate. Both of the AAS 01 completed and airworthy versions of the He 274 were eventually broken up in late 1953, after serving as "mother ships" for aerial launching, in the manner of a composite
Composite aircraft
A composite aircraft is made up of multiple component craft. It takes off and flies initially as a single aircraft, with the components able to separate in flight and continue as independent aircraft.-Design principles:...

 or parasite aircraft
Parasite aircraft
A parasite aircraft is a component of a composite aircraft which is carried, and air launched by, a mother ship aircraft.The first use for parasite aircraft was in 1916, when the British used a Bristol Scout, flying from a Felixstowe Porte Baby, a giant flying boat of its time. This eventually...

, of a number of early French advanced jet and rocket test aircraft, almost always launched from a strut-braced, above-fuselage position.

Specifications (He 274 V1)

See also

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