Information page for the Top Secret Focke-Wulf VTO Triebflugel Attack X-plane (original) (raw)
THE FOCKE-WULF TRIEBFLUGEL VERTICAL ATTACK X-PLANE
Without doubt, one of the most unusual fighter projects to be devised during the life of the Third Reich was the Focke-Wu
lf Triebflugeljager (rotating wing fighter) created by Professor von Holst and Dr. Kuchemann, of the Gottingen Technical University. Erich von Holst had participated at the Saalflugwettbewerb (Indoor Flying Scale-Model Competition) held at Breslau in 1940, where he demonstrated his model, identified as the Libelle (Dragonfly). he also referred to his creation as the Schwingenflugzeug Ornithoper, flapping wing aircraft). After investigating several
different design approaches, he published his findings in the "Jahrbuch der Luftahrtforschung" (Aeronautical Research Annual) of 1942.
Beginning in 1943, Focke-Wulf actively tried to find a reliable method of increasing the thrust of a conventional Lorin ramjet, following Dr. Sanger's research that proved this type of propulsion to be the most efficient way to accelerate advanced fighters. Dr. O. Pabst, head of Focke-Wulf's development department, and Dr.-Ing. Theodor Zobel, his most experienced colleague, had designed an engine that had a reduced drag coefficient due to it's clean shape. By March 1944, at had been ascertained that the Lorin ramjet would work efficiently up to altitudes of 59,000 ft. (18,000 m). Another advantage of the system was that cheap fuels and oils worked well. The first test model was finished in August 1944, but testing was delayed several months due to Allied air raids. It was impossible to complete certain essential sections, and the promised fuel was not available in time. During July 1944, the OKL had decided that four airworthy Lorin ramjets 
would be built by August 1945. Also in 1944, Focke-Wulf engineers had designed a Lorin ramjet powered Strahlrohr-Bomber (Lorin ramjet bomber), followed by a fighter bomber and some designs of fast fighters.
According to Focke-Wulf's overview, the Triebflugeljager had the following advantages: high efficiency, low fuel consumption, light weight, and a high ceiling; furthermore, it's engine would run on any combustible medium, gaseous or liquid, which could be vaporized. In the case of engine failure, three HWK rockets would ensure a safe landing.
The most important theoretical work on the Triebflugeljager was contributed by Dipl-Ing. Flugbaumeister Heinz van Halem, a highly qualified and gifted engineer. He had joined the Focke-Wulf development department in the summer of 1944, becoming part of a team of experienced designers and engineers. The Triebflugel was an aircraft whose wings were replaced by three airfoil-shaped rotor blades, each with a ramjet propulsion unit at it's tip. The pitch of the rotors could be adjusted by the pilot. At the top speed of 453 mph (730 km/h), normally used only during the climb, the rotating velocity of the ramjets would be much higher than the aircraft's forward speed. In this manner, efficient functioning of the ramjets would be ensured even at low air speeds. The greater the forward speed of the aircraft, the slower the rotation of the wings, and the smaller the difference between ramjet speed and airspeed.
For takeoff, the aircraft stood vertically on it's main wheel located in a pod at the tip of the rear fuselage, while each of the cruciform tail planes also had smaller auxiliary wheels. For initial wing rotation, Three Walter rockets were ignited, one in each ramjet. When the correct rotation speed was reached, then the ramjets would start, whereupon the smaller rockets were shut down. During this stage, the wing pitch was neutral, when they were moved to fine pitch, lift was generated to the aircraft, due partly to the rotation of the wings, and the ramjets' thrust being parallel to the longitudinal axis of the fuselage. After climbing and leveling off, course pitch was applied and rotation speed reduced accordingly, in order to maintain a constant speed at the wing tips of 683 mph (1,100 km/h). At the maximum design speed of the fighter, the wings rotated at 220 rpm. To land, the pilot had to rotate the aircraft while switching the rotor pitch, enabling the aircraft to vertically descend to it's takeoff position. During all flight regimes, the pilot seat remained fixed in one position. This meant that he was in a reclining position during takeoff and landing. It is interesting to contrast this approach with that of the American VERTOL (Vertical Takeoff and Landing) Convair XFY-1, Pogo, of 1954, in which the gimbal-mounted pilot's seat rotated forward 45 degrees, thus enabling the pilot to fly the aircraft from a more conventional position while it was taking off or landing.
The outstanding fighter performance data, compiled on September 9, 1944, greatly surprised RLM officials: length was 30 ft (9.15 m), with a maximum takeoff weight of only 11,355 lb (5,150 kg); the rate of climb at sea level had been calculated at 410 ft/sec (125 m/s), and at 22,965 ft (7,000 m) a rate of 164 ft/sec (50 m/s). The anticipated maximum speed was 575 mph (925 km/h) at sea level and 419 mph (675 km/h) at 45,930 ft (14,000 m). The proposed armament consisted of either two MK 103s (100 rpg) and two MG 151/20s (250 rpg), or four modern high power MK 213s installed on either side of the pressurized cabin.
Dan Shippey, the rocket man, created these two variations that are included on the FG WWII CDCheck out his site at:http://www.spacecraftmodels.com/
 |
 |
|---|
---
 Wayne's usually quick like a rabbit to send us photos of new releases. So quick is he, that these were ready BEFORE the models were even released! Click here to see a bevy of photos from his web page. Thanks Wayne. |
 |
|---|
Unfortunately for the Focke-Wulf VERTOL fighter project, development was interrupted when the Chef TLR ordered termination of all project under development that required more than a few months for completion. Only the Bachem Natter escaped this cutback. It is interesting to note that, Triebflugel fighter development seemed so promising to the western Allies that Pabst's and Zobel's reports remained classified by the Americans until January 1955.
---------------------------------------------
Military Directives regarding Luftwaffe camouflage 1944-45...
There was no specific body of orders that governed aircraft camouflage
in the Luftwaffe. Orders and instructions pertaining to aircraft
camouflage were usually part of larger directives from the German Air
Ministry's Technical Department (RLM). This department occasionally
issued catalogs of paint chips to provide specific references for
paint manufacturers and final assembly plants which applied camouflage
to aircraft. Since 1941, the Germans camouflaged their day fighters in
these RLM colors:
Specification Color Application
RLM 74 Dark Gray Upper surfaces
RLM 75 Medium Gray Upper surfaces
RLM 76 Light Blue-Gray Under surfaces
---------------------------------------------
The Attack X-plane Focke-Wulf Triebflugel, conceived by Heinz von Halem in September 1944, was a very interesting study of rotary wing flight and had some very unusual characteristics indeed. The Triebflugel sat vertically on the empennage and obtained its upward push by three wings in rotation around the fuselage. These rotary wings was positioned roughly a third length of the fuselage starting from the nose.
No torque was transmitted to the fuselage by the wings since they were propelled by three ramjets affixed to the ends. Below the speed of operation of ramjets(300 km/h), the wings were put into rotation by three booster rockets Walter (660 Ib of thrust) assembled in the nacelles of the ramjets. The great advantage of this design was the plane was to be able to take off vertically at a high vertical speed from just about anywhere. Each ramjet would have been 2 ft. to 3 in diameter, give approximately 1,850 lb of thrust and was developed from the tests led since 1941 by Otto Pabst in the department of Gas Dynamics at Focke Wulf, in Bad Eilsen.
Ram Jets are basically simple cylinders that operate as jet engines only when they pass through the atmosphere at high speeds. The compressed air acts as the compressor. Pabst had developed successfully a ramjet with a total length two and a half times the the diameter, which gave suitable propulsion for a rotational movement of the 'wings'. The starting rockets located in the ram jets were to rotate the blades up to mach .9 to allow the jets to kick in.
Another significant advantage of the ramjets was their capacity to operate on low quality fuel- a solution to the problem Nazi Germany faced more and more towards the war's end.
Das Triebflugel rested vertically on the ground, supported by its leg landing gear PLUS one main wheel..Each comprised of a spreadable housing with a wheel at its end. During the flight the wheels retracted into the nacelles. The pilot was positioned prone in the cockpit with a bubble canopy. This provided a more streamlined smaller fuselage cross section as well as making the would be pilot more comfortable not having to sit in messy pants that he surely would have had flying this little puppy. Armament was placed in the unobstructed the nose and consisted of two 20mm machine guns of 20 mm and two or 30mm.
The rotary wings had an DE-creasing angle of attack toward the tips like any propeller (but without control surfaces) and were to be set at +3 degrees. The Triebflugel was controlled by the usual tail control surfaces. The transition from the vertical flight to level flight and vice versa promised great difficulties for the pilot. Landing backwards can only result in problems as the American Engineers and Aircraft Companies were to discover in the following decade. (see Convair XFY-1 and Lockheed XFV-1).
Comments and Views: (we know nothing....just report it)
Sorry, the Great Hairy Paw and I disagree with that article 100%. The
power source was to be three JUMO turbojets, a sawed off version of the
same engine powering the ME-262. Now, how the fuel was to be fed out to
the tips from the fuselage...that's another matter entirely, unless the
fuel tanks were located within the rotors themselves, or had
self-contained fusion units....a la "Back to the Future"..is another
matter entirely. Remember, this was an "X-Plane" that never really got
off the drawing board. Ramjets...nice idea, but NO WORKEE!!!!
The French Article is totally wrong, IMHO!
Pax, Doc and GHP (Jan 26, 01)
Since no successful coleopter has ever flown (A French Job managed to get
off the ground, but became totally unstable while attempting to
transition to horizontal flight...fortunately, they had the foresight to
install an ejection seat...plane totalled, pilot took up knitting and
gardening afterwards....)
GHP and Ich both think that a counter-rotating prop design would have
been more stable, but doubt that a human pilot would have been able to
fly it. Why? A little thing called PRECESSION! What happens when you pick
up a spinning gyroscope and try to turn it? It promptly tries to turn at
a 90-degree angle from the direction you're trying to make it go, and
we're talkin' about a pretty heavy flywheel here, considering the size
and mass of the rotors. That thing would twist and turn in unpredictable
directions as soon as you tried to transition to horizontal
flight...possibly a computer-aided fly-by-wire system could do it, but
doubt pure mechanical controls would have been effective.
A second school of thought on the subject seems to hint that the rotor
effect was used solely for takeoff and landing, with the rotors pivoting
forward to act as lifting surfaces, flying on jet power alone and
handling like a conventional aircraft. No one really knows, as no example
was apparently ever built, and engineering documentation is scanty at
best. "Star Wars" before it's time! (Jan 27, 01)
GO TO: AEROSPACE/ BETWEEN WARS /BOMBERS / EARLY FLYERS
GLIDERS / HELICOPTERS/ JETS / LIGHT AIRCRAFT / RACERS
TRAINERS / WEIRD AIRCRAFT / WWI / WWII