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The Junkers Jumo 004

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Junkers Jumo 004B Orkan Turbojet Engine Specifications:

Weight: 1,640lbs
152 inches
30 inches
Output: 1,984lbs thrust
Turbine: 8 stage compressor, single stage exhaust turbine, adjustable exhaust cone
Starter Motor: Reidel 2 cycle 10hp@6,000rpm Started electrically from cockpit or manually via pull ring cord in jet engine nose
Starting RPM: 800
Operating RPM: 8,700
Operating Temp: 1,427°F
TBO - Time Between Overhauls: 50hrs (rarely achieved)
Airframes used on: German WWII Messerschmitt ME 262 Swallow, Arado Ar 234 Blitz Jet Bomber
Built in: 1944
Cost: $

This Junkers Jumo 004B Turbojet exhibit is unique in that the Reidel 2 cycle starter motor is clearly visible. The Reidel starter motor was started either electrically from the cockpit or by manually using a lawn mower type pull cord with a ring that protrudes from the jet engine nose cone. The Reidel starter motor was fueled by A3 80 octane gasoline and 5% two stroke oil in a .8 gallon annular tank in the nose of the engine nacelle.

Once the Reidel starter motor has started the turbine is allowed to spin up to 800rpm. At this point the pilot presses 2 buttons, one to inject B4 (smelly synthetic brown coal fuel oil) and 3% oil into the combustion chambers and another to light up the spark plugs to ignite the fuel oil mixture. At 1,800rpm the starter button could be released shutting off the starter motor allowing the turbine to spool up on its own. At 3,000rpm the ignition button for the glow plugs could be released and fuel flow would be switched to straight B4 from the main fuel tanks. After this the throttles could be advanced gradually to full power.

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Junkers Jumo 004B with exposed Reidel 2 cycle starter motor at the Air Victory Museum in Lumberton, NJ

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The Jumo 004 (109-004) Turbojet

The Jumo 004 project was initiated in late 1939 in a project led by Dr Anselm Franz, then in charge of Junkers' turbo- and supercharger development. 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 004 was assigned the RLM designation "109-004"

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The Jumo 004 axial-flow Turbojet engine

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.

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The Heinkel He-178 was the first pure jet-powered aircraft

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.

The design Dr Franz at Junkers Motoren (Jumo) initiated differed from von Ohain's design by using a new type of compressor, recently developed by the Aerodynamische Versuchsanstalt (AVA - Aerodynamic Research Institute) at G�ttingen. This was an axial-flow compressor, which offered greater efficiency and a smaller cross section then the earler designs.

In order to speed development and production of the new design, Dr Franz used a simple combustion area using six "flame cans". This was less efficient then the single annular can, but was simpler to implement. He also collaborated on the development of the engine's turbine with Allgemeine Elektricit�ts-Gesellschaft (AEG - General Electric Company) in Berlin. This approach was proved correct when the Jumo 004 entered production and service much earlier then the competing BMW 003 design

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.

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Me 262B-1a U1 night fighter (converted trainer), postwar image on US testing ground

Jumo 004B
Country Germany
Introduction 1944
Production end 1945
Type Non-afterburning turbojet
Compressor Eight-stage axial compressor
Turbine Single-stage
Maximum RPM 8,700 rpm
Weight 719 kilograms 1,590 pounds
Length 3.86 meters 12.66 feet
Diameter 81 cm 31.89 inches
Thrust 898 kilograms 1,980 pounds
Thrust to weight ratio 1.25

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.

Apart from the Me 262 and Arado Ar 234, the engine was used to power the experimental Junkers Ju 287 , and prototypes of the Gotha Go 229 and Heinkel He 280. There were plans to install it in the Heinkel He 162 as well as the Focke-Wulf Ta 183 and Henschel Hs 132 then under development.

Following World War II, Jumo 004s were built in small numbers by Malesice in Czechoslovakia, designated M-04 to power the Avia S-92, itself a copy of the Me 262. Jumo 004 copies were also built in the Soviet Union as the RD-10 engine, where they powered the Yakovlev Yak-15 as well as many prototype jet fighters.

In France, captured 004s powered the Sud-Ouest SO 6000 Triton and the Arsenal VG-70.

Derived from an article by Greg Goebel







Junkers Jumo 004

Jumo 004
Cutaway example of a Junkers Jumo 004 jet engine at the National Museum of the U.S. Air Force, Wright-Patterson AFB, Ohio.
Type Turbojet
Manufacturer Junkers
First run 1940
Major applications Messerschmitt Me 262

The Jumo 004 was the world's first turbojet engine in production and operational use, and the first successful axial compressor jet engine ever built. Some 8,000 units were manufactured by Junkers in Germany during late World War II and powered the operational Messerschmitt Me 262 jet fighter, Arado Ar 234 jet recon-bomber, and prototypes of the Horten Ho 229 aircraft. Variants of the engine were produced in Eastern Europe in the years following the war.


Design and development

The practicality of jet propulsion had been demonstrated in Germany in early 1937 by Hans von Ohain working with the Heinkel company. Most of the RLM remained uninterested, but Helmut Schelp and Hans Mauch saw the potential of the concept and encouraged Germany's aero engine manufacturers to begin their own programmes of jet engine development. The companies remained skeptical and little new development was carried out. Eventually in 1939 Otto Mader, head of Junkers Motoren (Jumo), stated that even if the concept was useful, he had no one to work on it. Schelp responded by stating that Dr Anselm Franz, then in charge of Junkers' turbo- and supercharger development, would be perfect for the job. Franz started his development team later that year, and the project was given the RLM designation 109-004 (the 109- prefix was common to all jet projects).

Franz opted for a design that was at once conservative and revolutionary. His design differed from von Ohain's in that he utilised a new type of compressor which allowed a continuous, straight flow of air through the engine (an axial compressor), recently developed by the Aerodynamische Versuchsanstalt (AVA - Aerodynamic Research Institute) at Göttingen. The axial-flow compressor not only had excellent performance, about 78% efficient in "real world" conditions, but it also had a smaller cross-section, important for a high-speed aircraft design.

On the other hand, he aimed to produce an engine that was far below its theoretical potential, in the interests of expediting development and simplifying production. One major decision was to opt for a simple combustion area using six "flamecans", instead of the more efficient single annular can. For the same reasons, he collaborated heavily on the development of the engine's turbine with Allgemeine Elektrizitäts-Gesellschaft (AEG - General Electric Company) in berlin, and instead of building development engines, opted to begin work immediately on the prototype of an engine that could be put straight into production. Franz's conservative approach came under question from the RLM, but was vindicated when even given the developmental problems that it was to face, the 004 entered production and service well ahead of its more technologically advanced competitor, the BMW 003.


Technical description and testing

Frontal view of a Jumo 004 engine mounted in a nacelle on an Me 262 fighter. The pull-starter handle is clearly visible in the center of the engine.

The first prototype 004A, which was constructed to run on Diesel fuel, was first tested in October 1940, though without an exhaust nozzle. It was bench tested at the end of January 1941 to a top thrust of 430 kgf (4,200 N; 950 lbf), and work continued to increase the output, the RLM contract having set a minimum of 600 kgf (5,900 N; 1,300 lbf) thrust.[1]

Vibration problems with the compressor blades delayed the program at this point, until a new stator design by Max Bentele solved the problem. The original alloy compressor blades were replaced with steel ones and with the new stators in place the engine developed 5.9 kN in August, and passed a 10-hour endurance run at 9.8 kN in December. The first flight test took place on March 15 1942, when a 004A was carried aloft by a Messerschmitt Bf 110 to run up the engine in flight.

On July 18, one of the prototype Messerschmitt Me 262s flew for the first time under jet power from its 004 engines, and the 004 was ordered into production by the RLM to the extent of 80 engines.

The initial 004A engines built to power the Me 262 prototypes had been built without restrictions on materials, and they used scarce raw materials such as nickel, cobalt, and molybdenum in quantities which were unacceptable in production. Franz realized that the Jumo 004 would have to be redesigned to incorporate a minimum of these strategic materials, and this was accomplished. All the hot metal parts - including the combustion chamber - were changed to mild steel protected by an aluminum coating, and the hollow turbine blades were produced from folded and welded Cromadur alloy (12% chromium, 18% manganese, and 70% iron) developed by krupp, and cooled by compressed air "bled" from the compressor. The engine's operational lifespan was shortened, but on the plus side it became easier to construct.[1]

The first production model of the 004B weighed 220 lb (100 kg) less than the 004A, and in 1943 had passed several 100 hour tests, with a time between overhauls of 50 hours being achieved.[2]

Later in 1943 a series of engines suffered vibration problems, and solutions dragged on. Eventually, in December, blade-vibration specialist Max Bentele was once again brought in during a meeting at the RLM headquarters, and the problem was solved by raising the blades' natural frequency by increasing their taper, shortening them by 1 millimeter, and reducing the operating speed of the engine from 9,000 to 8,700 rpm.

It was not until early 1944 that full production could finally begin. These setbacks were the principal factor delaying the Luftwaffe's introduction of the Me 262 into squadron service.

Given the lower-quality steels used in the 004B, these engines typically only had a service life of some 10-25 hours, perhaps twice this in the hands of a skilled pilot. Another shortcoming of the engine, common to all early turbojets, was its sluggish throttle response. Worse, it was fairly easy to inject too much fuel into the engine by throttling up too quickly, allowing heat to build up before the cooling air could remove it. This led to softening of the turbine blades, and was a major cause for engine failures. Nevertheless, it made jet power for combat aircraft a reality for the first time.

Riedel starter

The exhaust area of the 004 featured a variable geometry nozzle, which had a special restrictive body nicknamed the Zwiebel (German for onion, due to its shape when seen from the side) which had roughly 40 cm (16 inch) fore-and-aft travel to vary the jet exhaust's cross-sectional area for thrust control, as the active part of a pioneering "divergent-convergent" nozzle format.

One interesting feature of the 004 was the starter system, which consisted of a Riedel 10 hp (7 kW) 2-stroke motorcycle engine hidden in the intake. A hole in the extreme nose of the centrebody contained a pull-handle which started the piston engine, which in turn spun up the turbine. Two small gasoline tanks were fitted in the annular intake.

The Jumo 004 could run on three types of fuel:[3]


Postwar production

Following World War II, Jumo 004s were built in small numbers by Malešice in Czechoslovakia, designated M-04, to power the Avia S-92 which was itself a copy of the Me 262. Jumo 004 copies were also built in the Soviet Union as the RD-10 engine, where they powered the Yakovlev Yak-15 as well as many prototype jet fighters.

In France, captured 004s powered the Sud-Ouest SO 6000 Triton and the Arsenal VG-70.



A number of more advanced versions were in development at the end of the war. The 004C included an afterburner for increased thrust, but was not built. The 004D improved fuel efficiency with a two-stage fuel injector, and introduced a new throttle control that avoided dumping too much fuel into the engine during throttle-ups. The 004D had passed testing and was ready to enter production in place of the 004B, when the war ended. The 004E was a 004D model with an improved exhaust area for better altitude performance.

A much more advanced model based on the same basic systems was also under development as the Jumo 012. The 012 was based on a "two-spool" system, in which two turbines, spinning at different speeds, drove two separate sections of the compressor for more efficiency. In a jet engine the compressor typically uses up about 60% of all the power generated, so any improvements can have a dramatic effect on fuel use. Plans were also underway to use the 012's basic concept in an engine outwardly identical to the 004, known as the 004H, which improved specific fuel consumption from the 004B's 1.39 kg/(daN*h) to a respectable 1.20 kg/(daN*h), a decrease of about 15%.


Variants table

RLM Designation Type Layout Thrust or power Weight Speed
109-004B Turbojet 8ax 6in 1tu 8.8 kN (1984 lbf) 745 kg (1642 lb) 8700 rpm
109-004C Turbojet 8ax 6in 1tu 10.0 kN (2238 lbf) 720 kg (1588 lb) 8700 rpm
109-004D Turbojet 8ax 6in 1tu 10.3 kN (2315 lbf) 745 kg (1642 lb) 10000 rpm
109-004H Turbojet 11ax 8in 2tu 17.7 kN (3970 lbf) 1200 kg (2646 lb) 6600 rpm
109-012 Turbojet 11ax 6in 2tu 27.3 kN (6130 lbf) 2000 kg (4410 lb) 5300 rpm
109-022 Turboprop 11ax 8in 2tu 4600 ehp (3.4 MW) 2600 kg (5733 lb) 5000 rpm

Layout: ax=axial flow compressor stages, in=individual combustion chambers, tu=turbine stages.



Apart from the Me 262 and Arado Ar 234, the engine was used to power the experimental Junkers Ju 287, and prototypes of the Horten Ho 229 and Heinkel He 280. There were plans to install it in the Heinkel He 162 as well as the Focke-Wulf Ta 183 and Henschel Hs 132 then under development.


Specifications (Jumo 004B)

General characteristics






  1. Pavelec, p. 32
  2.  Meher-Homji
  3.  "Summary of Debriefing of German pilot Hans Fey" (PDF). Zenos' Warbird Video Drive-In.



  • Meher-Homji, Cyrus B. (September 1997). "Anselm Franz and the Jumo 004". Mechanical Engineering. ASME.
  • Pavelec, Sterling Michael (2007). The Jet Race and the Second World War. Greenwood Publishing Group. ISBN 0275993558.




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