Heinkel P.1076
In the 1935 contest for future fighter airplanes of the
Jagdwaffe, the Heinkel He 112 lost against the Messerschmitt Bf 109 because of its elliptic wing, more difficult to manufacture.
In an effort to remain in the contest, Dr. Heinkel promised to General
Luftzeugmeister Udet that he would be able to manufacture a fighter that, propelled by a Daimler Benz DB 601, would be capable of reaching 700 km/h.
Although Udet considered it impossible, the project (named Heinkel P.1035) started on May 25, 1937. The design team, led by Siegfried Günter, had the streamlining and drag reduction as the main guidelines. They adopted a well faired cockpit, a fully retractable tail wheel and a stressed skin wing covering, reducing the number of Butter rivets.
The DB 601 engine had exhaust ejectors for a small amount of thrust and the supercharger inlet was moved from the side of the cowling to a location under the propeller hub. The frontal radiator was replaced by a surface cooling system, inspired by some Macchi seaplane racers, which was already being tested on the He 119 V1.
Steam at high temperature was separated from the cooling fluid coming from the engine, using a centrifugal compressor and an expansion chamber. The heat exchangers, located in the wings, had a total capacity of 345 lt. and transferred the heat outside through the light alloy stressed covering. The steam was then condensed into liquid by cooling and returned to the engine circuit by means of 22 electric-driven centrifugal pumps.
A similar system was designed to refrigerate the oil, by passing it through a heat exchanger where methyl alcohol was added. The resulting vapour was then being ducted to the tail surfaces, where it was to be condensed back to liquid form before returning to the heat exchanger.
By the end of October the project was presented to the
Technisches Amt, receiving the He 100 number.
During the flight tests of the first prototype, it turned out that the wing suffered a structural distortion, caused by the high temperatures. It was also confirmed that the oil cooling system did not work at all.
The second prototype had a reinforced wing cladding and a retractable auxiliary cooler for the ground running and another, mounted on the port wing root, for the oil.
More prototypes and a short preproduction series were built and the He 100 achieved several speed records. But the little reliable cooling system that made it very vulnerable in combat, together with its maintenance problems and the lack of DB 601 engines advised against its mass production foreseen for 1939.
However, Ernst Heinkel tried it again following the RLM specifications for a piston-engine fighter which was to combine speed and high altitude performance.
By the end of 1944, the team led by Siegfried Günter started to work on the P.1076, possibly the fastest airplane of its class ever designed. The new project based on the He 100, adopted a more sophisticated version of the surface-cooling technology, where the steam circulated within the double layer of stressed skin covering that integrated wings, engine cowling, rear fuselage and tailfin. The centrifugal compressor and the expansion chamber were mounted into the rear fuselage.
The design of the wings was very advanced for its time, with a perfectly smooth surface and slightly swept forward at 8-degrees, constructed as a two piece, two spar all metal structure. The section between spars housed the condensation deposits of heat exchangers, electric driven centrifugal pumps, main undercarriage and two Mk 108/30 cannon with ammo tanks. Flaps and ailerons spanned the entire trailing edge.
The armoured cockpit was pressurized for high-altitude and covered with a clear vision bubble canopy hinged to the port side. The 700 lt. fuel tank was mounted behind the pilot seat. The tailwheel was fully retractable.
To facilitate its cooling on both sides, the tailfin was designed with a zero-degrees angle to the fuselage axis. As a consequence, the engine should be fitted with counter-rotating propellers.
The P.1076 was projected in four different versions, to adjust to the new 2,000 hp. Class engines that were expected to be available in 1945.
The P.1076/I was designed as a competitor of the Bf 109 K-14. Equipped with a DB 603 M, it would have been faster and climbed to higher altitude, carrying heavier armament.
The P.1076/II, fitted with a Jumo 213, should reach similar performances. Its production was to compete against the Fw 190 D-9, to which could have equally exceeded in armament, maximum speed and ceiling.
The P.1076/III was designed as a competitor of the Fw Ta 152 H. Equipped with a DB 603N and a wingspan expanded to 12.40 m, it would have been a formidable high-altitude interceptor, so fast and well-armed as the Me 262, but with a superior ceiling.
The design of a V16 variant of the DB 603, known as DB 609, was started in September 1942. It was a 16 cylinder 2,500 hp. engine, which prototype showed serious problems of vibration, due to the excessive length of the crankshaft, when tested in the Focke-Wulf 190 V19.
It was expected that the DB 609 engine, with two-stage supercharger, heat exchanger cooler and contra-rotating propellers, would reach 3,400 hp. at a ceiling of 12,000 m, but the vibration problem could not be solved and the program was cancelled in 1943.
From some drawings of the time can be inferred that the purpose was to install it on the P.1076.
The Version III, with increased span, would possibly serve to compensate the lengthier engine. This new airplane would have had a length of 9.86 m. and one 55-mm engine-mounted cannon Mk 112B, Mk 214 or Mk 412.
Technical Data He P.1076/I
| Engine | One Daimler-Benz DB 603M, twin supercharged, with take-off power of 1,825 hp. and 2,100 hp. with MW50 injection boost.
|
| Wingspan | 11 m. |
| Length | 9.60 m. |
| Sweep | (-8)-degrees at 0.25 chord. |
| Wing area | 18.00 sq. m. |
| Height | 2.90 m. |
| Max. weight | 3,260 kg. |
| Max. speed | 860 km/h at 11,000 m. |
| Rate of climb | 17.2 m/sec at 9,000 m. |
| Service ceiling | 14,500 m. |
| Max. range | 1,340 km. |
| Landing speed | 167 km/h |
| Armament | One Mk 103/30 engine-mounted cannon plus two Mk 108/30 wing mounted cannons. |
Technical Data He P.1076/II
| Engine | One Junkers Jumo 213 E, two stage, three speed supercharger with take-off power of 1,750 hp. and 2,100 hp. with MW50 boost.
|
| Wingspan | 11 m. |
| Length | 9.64 m. |
| Sweep | (-8)-degrees at 0.25 chord. |
| Wing area | 18.00 sq. m. |
| Height | 2.90 m. |
| Max. weight | 4,480 kg. |
| Max. speed | 860 km/h at 11,000 m. |
| Rate of climb | 17.2 m/sec at 9,000 m. |
| Service ceiling | 14,500 m. |
| Max. range | 1,340 km. |
| Landing speed | 167 km/h. |
| Armament | One Mk 103/30 engine-mounted cannon plus two Mk 108/30 wing mounted cannons.
|
Technical Data He P.1076/III
| Engine | One Daimler-Benz DB 603N, with two-stage twin supercharger, integrated heat exchanger cooler and contra-rotating three-bladed VDM propellers. Take-off power of 2,750 hp. and 1,500 hp. at 9,200 m.
|
| Wingspan | 12.40 m. |
| Length | 9.60 m. |
| Sweep | (-8)-degrees at 0.25 chord. |
| Height | 2.90 m. |
| Max. weight | 5,230 kg. |
| Max. speed | 880 km/h at 11,000 m. |
| Armament | One Mk 103/30 engine-mounted cannon plus two Mk 108/30 wing mounted cannon. |
