Editing Heinkel He 100 (section)

== Operational history ==
[[File:Heinkel He 100D 1940 propaganda photo.jpg|thumb|Heinkel He 100 posing as the fictitious "[[Heinkel He 113|He 113]]"]]

=== Pre-production series ===
Throughout the prototype period, the various prototypes were presented to the RLM as the basis for series production. The Luftwaffe never took Heinkel up on their offer, although the company decided to build a total of 25 of the aircraft one way or the other, so with 10 down, there were another 15 of the latest model to go. In keeping with general practice, any series production is started with a limited run of "zero series", resulting in the He 100 A-0 (postwar designation: He 100 D-0).

The A-0 was similar to the earlier prototype models, with a few notable changes. Primary among these was a larger vertical tail in order to finally solve the stability issues. In addition, the [[cockpit]] and canopy were slightly redesigned, with the pilot sitting high in a large canopy with excellent vision in all directions. The armament was reduced from the V8 model to one {{convert|20|mm|abbr=on}} MG FF/M in the engine V firing through the propeller spinner, and two 7.92&nbsp;mm (.30-caliber) MG 17s in the wings close to the fuselage.

The three pre-production aircraft were completed by the summer of 1939 and stayed at the Heinkel Marienehe plant for testing. They were later sold to the [[Japanese Imperial Navy]] to serve as pattern aircraft for a production line, and were shipped there in 1940. They received the designation '''AXHe1'''.

=== Production series ===
The final evolution of the short He 100 history is the production model. As the name suggests, the design was supposed to be very similar to the pre-production models, the main planned change being to enlarge the [[Tailplane|horizontal stabilizer]]. The big change was the abandonment of the surface cooling system, which proved to be too complex and failure-prone. A larger version of the retractable radiator was installed, and this appeared to cure the problems. The radiator was inserted in a "plug" below the cockpit, widening the wings slightly.

Though the aircraft failed to match its design speed of {{convert|700|km/h|abbr=on}} once it was equipped with weapons, the larger canopy and the radiator, it was still capable of speeds in the {{convert|644|km/h|abbr=on}} range. The He 100 had a combat range of {{convert|900|to|1000|km|abbr=on}} compared to {{convert|600|km|abbr=on}} for the Bf 109 by virtue of its low drag airframe. While not in the same league as the later escort fighters, this was at the time a superb range, which could mean that a production Heinkel 100 might have offset the need for the Bf 110.

Since by this point, however, the war was under way, and as the Luftwaffe would not purchase the aircraft in its current form, the production line was shut down. There were allegations that politics played a role in stopping production of the He 100 {{Citation needed|date=March 2025}}. The remaining 12 He 100 production fighters were used to form Heinkel's Marienehe factory defense unit, flown by factory test pilots. They replaced the earlier He 112s that were used for the same purpose and the 112s were sold. Early in the war, there were no bombers venturing that far into Germany and it appears that the unit never saw action. The fate of these aircraft remains unknown. The aircraft were also used for a [[propaganda]] spoof, as the supposed [[Heinkel He 113]].

=== Foreign use ===
When the war opened in 1939 Heinkel was allowed to look for foreign licensees for the design. Japanese and Soviet delegations visited the Marienehe factory on 30 October 1939 and were both impressed by the design.<ref name="AE 38 p78"/> The Soviets were particularly interested in the surface cooling system, having built the experimental [[Ilyushin I-21]] with evaporative cooling and to gain experience with it they purchased the six surviving prototypes (V1, V2, V4, V5, V6 and V7).<ref name="AE 38 p78">Green and Swanborough 1989, p. 78.</ref> After arriving in the USSR they were passed onto the [[TsAGI]] institute for study.

The Japanese were also looking for new designs, notably those using inline engines, where they had little experience and purchased the three pre-production models for 1.2 million RM, as well as a license for production and a set of jigs for another 1.6 million RM. The three pre-production models arrived in Japan in May 1940 and were re-assembled at Kasumigaura. They were then delivered to the Japanese Naval Air Force where they were renamed '''AXHe1''', for "Experimental Heinkel Fighter".<ref name="AE 38 p78"/> When referring to the German design, the aircraft is called both the He 100 and He 113, with at least one set of plans bearing the latter name.

The prototypes were accompanied by Heinkel test pilot Gerhard Nitschke, who worked with [[Lieutenant (navy)|Lieutenant]] [[Terufumi Kofukuda|Mitsugi Kofukuda]] during the testing and evaluation.{{sfn|小福田|2004|pp=198-201}} The Navy was so impressed by tests that they planned to put the aircraft into production as soon as possible, as their land-based [[Interceptor aircraft|interceptor]]. (Unlike every other armed forces organization in the world, the Japanese Army and Navy both fielded complete land-based air forces.) Hitachi won the contract for the aircraft and started construction of a factory in Chiba for its production. With the European war on, the jigs and plans never arrived.<ref name="AE 38 p78"/>