He 100 in service, but with caveats (1 Viewer)

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Heinkel He 100 Fighter Aircraft – Hunter of Records
by Dr. Volker Koos (ADL)
Revised as of September, 2016. Original publicaction in Classics of Aviation, April, 2006.

After the failure of the He 112, Heinkel sought success with the He 100. Technically, the He 100 made great strides forward in 1937-38. But like its predecessor, the He 112, this high-speed single-seater fighter was not a commercial success. With its world speed records, the He 100 nevertheless secured a firm place in aviation history.

History of its Creation

The elimination of the He 112 in the competition to become the Luftwaffe's standard fighter (see report on the He 112 on the ADL homepage) hit Ernst Heinkel hard. It not only dented the company's honor, but also the self-image of the company boss, who was particularly proud of the term "Heinkel-Tempo". Therefore, as early as January 1936, Heinkel began working on the P.1035 project for a Super V.J. (pursuit fighter) with a DB 601 and surface cooling. The company management knew that the Technical Office of the Reich Air Ministry (RLM) was thinking about such an aircraft, although it was already being worked on at Focke-Wulf as a twin-engine design (the later Fw 187).

Without the knowledge of the RLM, Heinkel built a mock-up of the new fighter, which was initially designed to have a top speed of 650 km/h (403.9 mph) and was to carry a 20 mm Oerlikon cannon in addition to two machine guns. The reduction of harmful drag was a top priority in the aerodynamic design. One of the key points was to dispense with conventional radiators and replace them with modern surface cooling.

Preliminary tests were carried out with a He 70 to test the new cooling system. In order to save on the resistance-generating coolers for engine oil and cooling water, Heinkel used large parts of the airframe paneling for cooling. At the same time, to reduce the risk of water loss due to gunfire damage, the engineers used evaporative cooling. The cooling water under pressure in the engine could be heated to over 100˚C. When the superheated water from the engine escaped into the cooling circuit, steam formed, which was fed into the cooling cells in the wing. After condensation, the water was fed back into the engine's cooling channels using small electric pumps. The hot engine oil evaporated into methyl alcohol in a heat exchanger. The alcohol vapor then condensed in cooling cells in the tail unit.

Construction of the new fighter began in August 1937. Heinkel had learned lessons from the defeat of the He 112 and paid particular attention to technical simplifications and weight-reducing structures. For example, the front fuselage shell was designed as an integrated engine mount. This saved Heinkel the weight of a separate engine mount, and also enabled the engine cowling to be cut around the engine in an aerodynamically optimal way. A design that is also found in the North American P-51 Mustang. In the first completed wing in the plate construction developed by Heinkel, the engineers achieved a weight saving of 62.1 percent for the individual parts and 57 percent for the rivets, despite the surface cooling and the tightly riveted tanks.

The New Fighter Should Reach a Good 700 km/h (435 mph)

On October 1, 1937, Heinkel presented the new project to Major General Ernst Udet and his senior advisor. Under the type number He100, which was approved by the RLM on October 23, the company submitted an offer to the ministry at the end of the month for the delivery of three V-planes (serial numbers 1901 to 1903). The design specification, completed on October 27, assumed a top speed of around 700 km/h (435 mph). From the outset, Heinkel planned to attack the existing world speed records of 3, 100 and 1000 kilometers with the new He 100 and to beat the absolute record of 709.2 km/h (440.7 mph) held by the Italian Macchi MC 72.

In mid-November 1937, it was planned to use the He 100 V-1 for the record flights and to build a fourth V-model with a reduced wing area of eleven square meters in order to possibly improve the aircraft's own best values later on. The offer was to be presented to General Udet during his visit in December. During Udet's visit on December 16, 1937, the negotiating partners agreed to design the first two aircraft primarily for preparatory flight tests, with later military equipment to be taken into account but not installed for the time being. The He 100 V-3, on the other hand, was to be designed purely as a record-breaking aircraft with a smaller wing, a more aerodynamic canopy and a lowered horizontal tail unit. The plan also called for the V-4 to be used as a prototype aircraft for series production with full armament, i.e. with a motor cannon and two wing machine guns.

Cooling Problems During the First Test Flight

The construction of the first prototype was strongly pushed by the technical director Heinrich Hertel in order to be ready for the company boss's 50th birthday on January 24, 1938. On January 22, 1938, chief pilot Gerhard Nitschke flew the He 100 V-1 (Wnr.1901, D-ISVR). But after just nine minutes he had to abort the first test flight when water vapor escaped from the ventilation lines of the surface cooling system.

For Heinkel, the first priority was to test the new evaporative cooling system and to achieve the highest possible record speeds. After initial problems, additional cooling cells were integrated into the fuselage of the V-1. But problems with the evaporative cooling system continued in March 1938. Based on the test experience with the V-1, the fin of the V-2 was enlarged. Heinkel continued to hope that outstanding performance would lead to a series production order. The second test aircraft (He 100 V-2, Wnr. 1902, D-IUOS) flew for the first time on May 17, 1938, followed by the V-3 (Wnr. 1904, D-IDGH) the following month. After the test flight, the V-2 was given exhaust jets, a smaller and more streamlined canopy and a special high-speed propeller with narrower blades. Disturbing joints and depressions in the cell paneling were filled, the antenna mast was removed and the entire surface was polished to reduce resistance as much as possible.

The story of Udet's spontaneous decision to fly the record himself during a chance visit to Rostock, described by Ernst Heinkel in his book "Sturmisches Leben" and often circulated, is a complete invention! Letting Udet fly the world record was more of an attempt by Heinkel to get the He 100 into service with the Luftwaffe alongside the Bf 109. This also included the designation He 112U, under which the record was registered, and the flight demonstration during Hitler's visit to Barth on June 13, 1938.

While the series prototype, the He 100 V-4 (Wnr. 1903), was still under construction, work began in June 1938 on the construction of the pre-series of 25 He 100 A-0s ordered by the RLM. In the meantime, there had been several problems with the V-planes, especially with the undercarriages and due to excessive cooling water loss. In August, the He 100 V-3 was lost when Gerhard Nitschke had to parachute out because the undercarriage leg had jammed. In October, half of the undercarriage of the V-4, which had been flown in a month earlier, broke off. By the beginning of September 1938 at the latest, the RLM had decided that there were no plans to purchase the He 100, with the exception of the test aircraft and the pilot series, "since continuous development of the Bf 109 would be more cost-effective in terms of troops."

In July 1938, Heinkel equipped the He 100 V-2 for the first time with a motor cannon and two machine guns to prepare the fighter for the pre-series. Construction of a break cell also began in this month. By October 1938, the He 100 had also been fitted with the improved, so-called large-capacity cooling system. Hans Dieterle aborted the first flight with the modified cooling system on October 25, 1938, due to missing landing gear indicators. The aircraft was damaged during the hard landing.

Japan Showed Interest in the Modern Fighter

At the beginning of November 1938, the RLM finally informed Heinkel that large-scale production of the He 100 for the Luftwaffe was out of the question. Just a few days later, on November 16, 1938, Gerhard Nitschke flew the first example of the pilot series, the He 100 A-01 (Wnr. 3001, also known as the He 100 V-5). Heinkel still hoped to get the He 100 into the Luftwaffe, even though the experience with the advanced surface cooling was apparently not convincing. He therefore proposed converting five to six aircraft from the pilot series to conventional coolers. The plan was now changed so that 19 aircraft would be built with surface cooling like the V-4 and the last six aircraft with the wing cooler arrangement and a new tail unit.

At the end of the month, the He 100 V-8 (Wnr. 1905), intended as a replacement for the He 100 V-3 in the attack on the absolute speed record, flew for the first time. There were again problems with the undercarriage. During a visit by a Japanese naval delegation on December 1, 1938, the two He 100 and He 119 models, which had been rejected by the Luftwaffe but had now been approved for export, were inspected. Heinkel immediately negotiated an offer to supply five He 100s and to build the model under license in Japan. At the end of December 1938, the Heinkel works were asked by the RLM to stop all work on getting the He 100 ready for series production. Two months later, the next two aircraft of the pilot series were flown in, the He 100 V-6 and V-7 (Wnr. 3002 and 3003).

The hour that made the He 100 famous around the world struck on March 30, 1939. On that day, factory pilot Hans Dieterle attempted to break the absolute world speed record in Oranienburg near Berlin. The record team had already arrived at the Heinkel factory in Oranienburg at the beginning of the month and, after completing preparations, had to wait for favorable weather. During the flight, the aircraft was not allowed to exceed a height of 75 meters above the ground. Dieterle drove the He 100 V-8 over the three-kilometer test track at exactly 746.66 km/h (463.95 mph). This made him the fastest man in the world. For this, Hermann Göring appointed him the youngest German flight captain at the time.

The record-breaking aircraft, again referred to in the press as the He 112U, was equipped with a specially modified racing engine derived from the DB 601. At higher speeds, it briefly produced over 2000 hp. The planned record flight over the 100-kilometer distance, for which the He 100 V-4 had been prepared, never took place.

In May 1939, factory pilot Fritjof Ursinus flew the serial numbers 3004 to 3006 of the A-0 series. At the start of the war, the aircraft up to serial number 3019 were so complete that delivery could be expected by the end of October. On September 12, 1939, General Aviation Master Udet approved the completion of the He 100, which was already under construction. In total, 24 aircraft are believed to have left Heinkel's factory halls. In addition to the prototypes V-1 to V-4 and V-8, there were 19 He 100 A-0s, of which the first three also received V numbers (V-5 to V-7).

False Designations in Post-War Literature

Several He 100s were used for various tests at the Luftwaffe test site in Rechlin, including the V-6 (Wnr. 3002, D-IACI). The pre-production aircraft that remained in Rostock-Marienehe formed a so-called factory protection squadron from October 1939. Factory pilots were to use them to fight attacking bombers. These He 100 A-0s were given fantasy paint jobs and issued during the war as the Luftwaffe's "latest German single-seater fighter" or "He 113 night fighter". The type designation He 113 was just as wrong as the previously used designation He 112U for the record-breaking aircraft. The 113 was actually an RLM number assigned to Heinkel. It was used briefly during the development of a dive bomber, which was then given the designation He 118. Heinkel simply did not want to use the "13". The version designation He 100D for the A-0 aircraft can be found in various literature. It is just as much a post-war invention as the versions He 100B and C, to which some authors even assigned some of the prototypes.

Japan received two He 100s in 1940 and acquired the license rights. The Soviet Union also ordered a total of ten He 100s in 1940 after the conclusion of the non-aggression pact, five of which were to be equipped with evaporative cooling and the others with normal water coolers. According to literature, however, only six of these were delivered. The He 100 V-8, painted in camouflage, was exhibited in the German Museum in Munich, where it later fell victim to a bombing raid.

Today, there are no He 100s left in the world. Anyone who wants to get a true-to-life picture of the elegance of this fighter and record-breaking aircraft will have to travel far. A non-flyable, full-size replica can be found in the Planes of Fame Air Museum in Chino, California. A sign of the appreciation that Heinkel's He 100, which was so technically advanced for its time, enjoyed even across the Atlantic.

Technical data of the Heinkel He 100 V-3

Aircraft model, lost due to crash in August 1938

Motor:..............-----.....--Daimler-Benz DB 601 Aa
Takeoff Power: ---------=1.100 PS (1084 hp) at 2500 RPM
Span: ---------------------7,60 m / 24'11.2"
Length: -------------------8,00 m
.......................................-26'3"
Height:............-----.......=3,60 m / 11'9.7"
Wing Area:.........-----....=11,0 m2 / 114 sqft. 4060.9 lb.
Empty Weight:.....-----.-=1.842 kg / 4060.9 lb.
Max Takeoff Weight:----=2.439 kg / 5377.1 lb.
Max Speed:.........-----...=730 km/h at 5000 m
-----------------------------453.6 mph @ 16404'
Landing Speed:...-----.....140 km/h
.............................------......87 mph
Time to Climb (2000 m)]: --2.2 min (15.15 m/sec)
------------------------------.(2982.58 fpm)
Time to Climb (6000 m): --6.9 min (14.49 m/sec)
------------------------------.(2852.90 fpm)
Service Ceiling: ----------=10.000 m
.....-....................................32808.4'
Range: ------------=.-------1.100 km
.....-....................................683.5 mi

The information is based on EHF data sheet 1220 from 1938

Update (3/1/25): Translated, with a few alterations for punctuations, ease of read, and unit conversions.
 
Last edited:
While they did put more thought into the surface-evaporation system than I would have thought, they appeared to still had problems with the system springing leaks.
 
Zipper730 said:
GrauGeist GrauGeist , S Shortround6 , tomo pauk tomo pauk , W wuzak , I'm curious if you guys have any data as to what pressures were used for the surface-evaporative cooling system in the He 100
Click to expand...
I've sifted through some of the test reports for the He 100 V2, V4 and V5, they don't mention the pressures, just the coolant temperatures (that went up to 120 °C with engine running at 2500-2560 rpm and 1.42 ata).
 
Zipper730 said:
GrauGeist GrauGeist , S Shortround6 , tomo pauk tomo pauk , W wuzak , I'm curious if you guys have any data as to what pressures were used for the surface-evaporative cooling system in the He 100
Click to expand...
The Rolls Royce Merlin pressurized its coolant to 18psig (33psia) so that it could run at 130DegC. The DB601 was not similarly pressurized. If you place the cooling system between the coolant pump and the engine, you can run the radiators at higher pressures that what the engine can handle.

None of this changes the fact that surface radiators are a bad idea on a warplane.
 
From an old thread.
jap-100-jpg.jpg

The items marked 1 are the engine coolant panels. #2 are the fuel tanks. I have forgotten was #3 is.
The oil cooler was behind the pilot in the rear of fuselage. The shaded panels in the top of the rear fuselage, the vertical fin and horizontal stabilizers are alcohol filled panels that provided the cooling for the buried oil cooler.
This is why the whole surface radiator/evaporative cooling idea was a really, really bad one for a warplane.
Your aircrew are essential manning a flying radiator. Normal radiators were venerable enough to enemy fire. The surface radiator/evaporative cooling system increased the target area/vulnerability by an order of magnitude.
 
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