The BMW 003 (109-003) Turbojet
The BMW 003 Turbojet began life as a project of the Brandenburg Motor Works in Germany. The Heinkel company had proved the potential of jet propulsion as early as 1937, and the German Air Ministry encouraged other engine manufacturers to initiate their own jet engine developments. The 003 was assigned the RLM designation "109-003"
German turbojet-engine development work had begun in the mid-1930s, with the initial concepts conceived by an engineer named Hans-Joachim Pabst von Ohain, whose efforts paralleled those of Frank Whittle of Britain.
In 1933, while von Ohain was working on his doctorate at the University of Goettingen, he began investigate the gas turbine as a basis for an advanced aircraft engine. Although most of the feedback he received suggested that gas turbines would be too heavy for such a role, he pressed on anyway, developing a demonstrator model of a "turbojet" engine in his garage, with the help of a mechanic named Max Hahn.
Von Ohain managed to impress his professor, R.W. Pohl, with a test run of the model. Pohl was both open-minded and well-connected, and in 1936 he sent von Ohain on to aircraft manufacturer Ernst Heinkel with a letter of recommendation. Von Ohain defended his ideas under grilling by Heinkel engineers, and was put in charge of a design team to develop a practical turbojet engine.
Von Ohain's team had a working bench-test prototype in September 1937, six months after Whittle had reached the same benchmark. Von Ohain's prototype burned hydrogen, which was not a practical fuel, but further work with Max Hahn led to an engine that burned kerosene.
Ernst Heinkel gave the go-ahead to develop a flight-test engine, designated the "HeS-3", which was strapped to an He-118 dive bomber for evaluation. Tests began in May 1939 and continued until the engine burned itself out a few months later. Enough had been learned to build a pure jet-powered experimental aircraft, the "Heinkel He-178", powered by an improved "HeS-3B" engine with 2.94 kN (300 kgp / 835 lbf) thrust. Later in the flight test program, the He-178 would be fitted with a further improved "HeS-6" turbojet with 5.78 kN (590 kgp / 1,300 lbf) thrust.
The He-178 was a simple "flying stovepipe", with straight-through airflow from nose to tail. The aircraft had high-mounted tapered wings and a conventional tail assembly. Although it had fully-retractable "tailsitter" landing gear, the landing gear was bolted into the down position.
The He-178 performed its first test flight on 27 August 1939, a few days before the outbreak of World War II. The flight lasted about five minutes, with the pilot reporting that the aircraft "had no vibration and no torque like a propeller engine. Everything was smooth, and ... felt wonderful." Von Ohain was now well ahead of Whittle, whose efforts were bogged down, first by official indifference and then by national crisis. Whittle would not fly his own experimental jet aircraft, the "Gloster-Whittle G.40", until May 1941.
The Luftwaffe and the German Air Ministry ("ReichsLuftfahrtMinisterium / RLM") were preoccupied with war, and the authorities didn't witness a flight demonstration of the He-178 until November 1939. They were generally unimpressed, since the He-178 was not as fast as the best piston fighters. Heinkel was told: "Your turbojet is not needed. We will win the war on piston engines."
After a total of about a dozen test flights, the He-178 was sent to the national air museum in Berlin, where it was destroyed in a bombing raid in 1943. A second He-178 was planned, but not completed.
Although the RLM seemed indifferent to the He-178, the ministry was nonetheless actively pushing German industry to develop turbojets. In hindsight, it seems that the left and right hands of the RLM were not in agreement, which summarizes most of the Third Reich's attempts to develop advanced weapons.
Hans A. Mauch had become head of rocket development at the RLM in April 1938, and quickly expanded his office's charter to emphasize turbojet development, working with an experimental department under Helmut Schelp in the RLM research branch. By mid-1938, the two men had set up a comprehensive program of jet engine development that was soon sponsoring a range of turbojet and turboprop projects.
In response to RLM urging, the Bramo company began work under the direction of Hermann Ostrich, on a pair of "axial flow" engines. Both Whittle's and von Ohain's engines were "centrifugal flow" engines, with a compressor like a pump impeller shoving air into combustion chambers ringing the engine. The compressor in an "axial-flow" engine, in contrast, uses rings of blades to drive air directly back into the combustion chambers.
The two Bramo engines included one with a contra-rotating compressor assembly to reduce torque, which eventually was designated the "109-002", and a simpler engine without the contra-rotating fan scheme that was eventually designated the "109-003". Incidentally, the "109-" suffix was used by the RLM to specify turbine engine projects.
Bramo's works at Spandau were bought out by the BMW concern in mid-1939. BMW had been working on their own centrifugal-flow turbojet, but the company quickly decided to abandon their own effort and focus on the two Bramo engines obtained in the buyout. The 109-002 proved too complicated and never flew, and the project was abandoned in 1942. The company focused on the simpler 109-003, with fabrication beginning in 1939 and first test runs in 1940. By that time, the engine was known as the "BMW-003".
Construction of the first BMW 003 prototype began late in 1939, and the BMW 003 engine ran for the first time in 1940. The thrust produced by the engine on this initial run was less then half the design target of 1420lbf (6.3kN). Flight testing of the BMW 003 did not take place until mid 1941, when a BMW 003 was mounted under a Messerschmitt Bf 110. Problems continued to delay the engine, and when it was tested in an Messerschmitt Me-262 (which had been designed to be fitted with two BMW 003 engines) in November 1941 both engines failed.
Even before this, in the fall of 1938, a Messerschmitt design team under Dr. Waldermar Voight had drawn up concepts for a interceptor fighter with twin turbojet engines. The preliminary designs for "Project 1065", as it was designated, went through a iteration or two and finally resulted in a proposal submitted to the RLM in May 1940
Messerschmitt's dream fighter had the turbojets mounted in nacelles under the middle of the wings. The wings were slightly swept to ensure proper center of gravity, and had an unusually thin chord, or ratio of thickness to width, for good high-speed performance. Since the wing's features for high-speed performance compromised low-speed handling, a "slat" was added to the front of the outer wings. The slat was automatically extended to improve handling at low speeds.
The fuselage had a triangular cross section and substantial fuel capacity to feed the thirsty engines. The aircraft was a "taildragger", with fully retractable landing gear. In July 1940, the RLM ordered three prototypes, under the designation "Messerschmitt 262 (Me-262)", to be powered by BMW-003 engines.
Airframe development far outpaced engine development, and so the first prototype, the "Me-262-V1" ("V" standing for "Versuchs / Experimental"), was fitted with a single Jumo-210G piston engine with 530 kW (710 HP) and a two-bladed propeller for preliminary test flights. First flight was on 18 April 1941. The RLM was becoming more interested in the aircraft, ordering five more prototypes in July 1941, to follow the initial order for three.
The Me-262-V1 was finally fitted with a pair of BMW-003 turbojets, each with 5.40 kN (550 kgp / 1,200 lbf) thrust, in November 1941. The Jumo 210G piston engine was retained, which was fortunate, since the turbojet engines were hopelessly unreliable. On 25 March 1942, Messerschmitt test pilot Fritz Wendel took off and suffered immediate failures of both engines. He managed to make a go-round on the piston engine and land, damaging the aircraft but suffering no injury himself.
The BMW 003 engine was abandoned for the Me 262, being replaced by the Junkers Jumo-004 which seemed more promising. The third prototype, the "Me-262-V3", was fitted with two Jumo-004A pre-production engines with 8.24 kN (840 kgp / 1,850 lbf) thrust each. Wendel took the V3 into the air on 18 July 1942 and found the aircraft extremely impressive. Work on the BMW 003 continued at BMW, and by late 1942 it had been made far more powerful and reliable. The improved engine was flight tested under a Junkers Ju 88 in October 1943 and was finally ready for mass production in August 1944.
|Number built||approx. 500 units|
|Compressor||Seven-stage axial compressor|
|Weight||562 kilograms||1,240 pounds|
|Length||3.53 meters||11.58 feet|
|Diameter||69 cm||27.17 inches|
|Thrust||798 kilograms||1,760 pounds|
|Thrust to weight ratio||1.42|
The BMW-003 had been intended for export to Japan, but working engines were never supplied. Japanese engineers used drawings and photos of the engine to design an indigenous turbojet, the Ishikawajima Ne-20.
Following the war, two captured BMW-003s powered the prototype of the first Soviet jet, the Mikoyan-Gurevich MiG-9, and copies of this engine, designated RD-20 powered this aircraft in series production.
At the end of the war, Hermann Ostrich soon accepted an offer from the French government to work on further refining the -003 for Voisin, a division of SNECMA. The result was the Atar, which in various forms powered French military aircraft for decades to come.