Editing Heinkel He 100 (section)

== Projekt 1035 (initial development) ==
Following the selection by the [[Reich Air Ministry|RLM]] of the Bf 109 as its next single-seat fighter over the [[Heinkel He 112|He 112]], Ernst Heinkel became interested in a new fighter that would surpass the performance of the Bf 109 as much as the Bf 109 had surpassed that of the [[biplane]]s it replaced.<ref>{{Cite web |title=Heinkel He 100D-1 {{!}} Planes of Fame Air Museum |url=https://planesoffame.org/aircraft/plane-He-100D-1 |access-date=2025-01-05 |website=planesoffame.org}}</ref> Other German designers had similar ambitions, including [[Kurt Tank]] at [[Focke-Wulf Flugzeugbau GmbH|Focke-Wulf]]. There was never an official project on the part of the RLM, but Rudolf Lucht felt that new designs were important enough to fund the projects from both companies to provide "super-pursuit" designs for evaluation. This would result in the single-engined He 100 fighter, and the promising twin-engine [[Focke-Wulf Fw 187|Fw 187 ''Falke'']] ''Zerstörer''-style [[heavy fighter]], both reaching the flight stage of development.

[[File:De Heinkel He 100 V8 (2157 001-039).jpg|thumb|left|He 100 V8 prototype, 1938.]]
Walter Günter, one half of the famous [[Siegfried and Walter Günter|Günter brothers]], looked at the existing He 112, which had already been heavily revised into the He 112B version, and decided it had reached the end of its development and started  a completely new design, ''Projekt 1035''. Learning from past mistakes on the 112 project, the design was to be as easy to build as possible yet {{convert|700|km/h|kn mph|abbr=on}} was a design goal. To ease production, the new design had considerably fewer parts than the 112 and those that remained contained fewer compound curves.<ref name="Smith&Kay p238-9">Smith and Kay 1972, pp. 238–239.</ref> In comparison, the 112 had 2,885 parts and 26,864 rivets, while the P.1035 was made of 969 unique parts with 11,543 rivets. The new straight-edged wing was a source of much of the savings; after building the first wings, Otto Butter reported that the reduction in complexity and rivet count (along with the Butter brothers' own explosive rivet system) saved an astonishing 1,150 man hours per wing.

The super-pursuit type was not a secret, but Ernst Heinkel preferred to work in private and publicly display his products only after they were developed sufficiently to make a stunning first impression.{{fact|date=December 2024}} As an example of this, the mock-up for the extremely modern-looking He 100 was the subject of company Memo No.3657 on 31 January that stated: "The mock-up is to be completed by us ... as of the beginning of May ... and be ready to present to the RLM ... and prior to that no one at the RLM is to know of the existence of the mock-up."

Walter Günter was killed in a car accident on 25 May 1937, and design work was taken over by his twin brother Siegfried, who finished the final draft of the design later that year. Heinrich Hertel, a specialist in aircraft structures, also played a prominent role in the design. At the end of October the design was submitted to the RLM, complete with details on [[prototype]]s, delivery dates and prices for three aircraft delivered to the [[Rechlin-Lärz Airfield|Rechlin]] test center.

The He 100 should have been designated '''He 113''', but since the number [[Triskaidekaphobia|"13"]] was unlucky, it was not used.<ref>Lepage 2009, p. 215.</ref> It is reported that Ernst Heinkel lobbied for this "round" number in the hope that it would improve the design's chances for production.{{citation needed|date=November 2013}}

=== Design phase ===
[[File:800px-Истребитель He 100 в НИИ ВВС 1940.jpg|thumb|Heinkel He 100]]
In order to get the promised performance the design included a number of drag-reducing features. The [[landing gear]] (including the tailwheel) was retractable and completely enclosed in flight.

There was also a serious shortage of advanced aero engines in Germany during the late 1930s. The He 100 used the same [[Daimler-Benz DB 601]] engine as the Messerschmitt Bf 109 and Bf 110, and there was insufficient capacity to support another aircraft using the same engine. The only available alternative engine was the [[Junkers Jumo 211]], and Heinkel was encouraged to consider its use in the He 100. However, the early Jumo 211 then available did not use a pressurized cooling system, and it was therefore not suitable for the He 100's [[Radiator (engine cooling)#Evaporative cooling|evaporative cooling]] system. Furthermore, a Jumo 211-powered He 100 would not have been able to outperform the contemporary DB 601-powered Bf 109 because the [[supercharger]] on the early Jumo 211 was not fully shrouded. In order to reduce weight and frontal area, the engine was mounted directly to the forward [[fuselage]], which was strengthened and literally tailored to the DB 601, as opposed to conventional mounting on engine bearers. The [[cowling]] was very tight-fitting, and as a result the aircraft has something of a slab-sided appearance.

In order to provide as much power as possible from the DB 601, [[exhaust ejector]]s were used to provide a small amount of additional thrust. The supercharger inlet was moved from the normal position on the side of the cowling to a location in the [[leading edge]] of the left wing. Although cleaner-looking, the long, curved induction pipe most probably negated any benefit.

=== Cooling systems ===
For the rest of the designed performance increase with the DB 601 powerplant, Walter turned to the experimental method of evaporative cooling. Heinkel and the Günter brothers were avid proponents of the technology, and had previously used it on the He 119, with promising results. Evaporative or "steam" cooling promised a completely drag-free cooling system and reduced weight. No detailed plans of the installation survive. The earlier prototypes varied, but they were all eventually modified to something close to the final standard before they were exported to the [[Soviet Union]].

=== Design issues ===
Overheating problems and general failures with the cooling system motors was a continued problem during development. Throughout the testing period, failures of the pumps ended flights early, although some of the test pilots simply started ignoring them. In March, Kleinemeyer wrote a memo to Ernst Heinkel about the continuing problems, stating that Schwärzler had asked to be put on the problem.

Another problem that was never cured during the prototype stage was a rash of landing gear problems. Although the wide-set gear should have eliminated the collapse of landing gears that plagued the Bf 109, especially in the difficult take-offs and landings, the He 100's landing gear was not built to withstand heavy use, and as a result they were no improvement over the Bf 109. V2, 3, 4 and 6 were all damaged to various degrees due to various gear failures, a full half of the prototypes.