Focke Wulf Triebflügel

[hesham]

By the way,


the Focke Wulf Triebflugel was called FW.354.

 

[hesham]

My dear Jemiba,


the source of Focke Wulf FW.354 is the book; Rotorcraft of the Third Reich

 

[Jemiba]

Interesting review:
http://luftwaffereviews.blogspot.de/2007/09/rotorcraft-of-third-reich.html

We're not the only ones, taking those designations with a pinch of salt. Until we get a
confirmation, we should be a little bit careful with its use, I think !

 

[Jemiba]

Just an interesting side note (at least to me) is the mention of a report by Erich von Holst (zoologist),
Dr. Küchemann (aerodynamicist, working for Focke-Wulf during the war) and K.Solf in Steve Coates
"Helicopters Of The Third Reich". E.von Holst had built two successful indoor flying models based on the
flying technique of a Dragonfly. This principle, using flaping wings was scaled up and led in the end to
the fuselage mounted rotor of the "Triebflügel".

 

[hesham]

Great find my dear Jens.

 

[Michel Van]

Thats really a surprise: Ornithopter

i wonder if Focke-Wulf presented that concept to Reichsmarschall Herman Göring...

 

[Jemiba]

It is said in the mentioned book, that this report was published in the "Jahrbuch der deutschen
Luftfahrtforschung 1942", where already ways to develop a VTO tailsitter were described. The
then still missing component, the ramjet, was added byDr.Otto Pabst and a report submitted
to the RLM in 1944.
Don't think, that today anybody would start such a project with considering flapping wings !
Another detail mentioned are different layouts for positioning the rotating wings and the cockpit,
see below.

 

[Jemiba]

Couldn't resist to try to sketch the Triebflügel pre-study with the cockpit behind the rotor wing.
The layout with the wing at the extreme nose was regarded as probably giving problems with
the weapons installation.
(For this one I spoiled the drawing from http://www.aviastar.org/helicopters_eng/focke_thrustwing.php)

 

[hesham]

Although,the drawing is very nice my dear Jens.

 

[hesham]

By the way,


the Focke Wulf Triebflugel was called P.0310240-0061,from Flugzeug Profile 23.

 

[lark]

This is incorrect I'm afraid...

No Focke Wulf P number is given in the No.23 Flugzeug Profile text.
Text for the drawing on p.41 says

'Triebflügeljäger mit Lorin antrieb 310240-0061'

Literal: Powered wing with Lorin driving
No 'P' letter.
drawing is dated 15.8.44.

There is also no source for the Triebflügel designation
in Rotorcraft of the 3e Reich (FW-354) Mushroom.

 

[hesham]

My dear Lark,


we know for Focke Wulf,the number 0310 or 310 is a reference to "P" series,and when the
author wrote under the drawing 310240,what is that meaning?,I think he meant the "P"
aircraft or projects series.

 

[Jemiba]

Internal project numbers, as we know them weren't longer, than three digits, I think. And the number "0310..." was used for
vrious other Focke-Wlf projects, too, so I'll agree with lark that the give number is no direct indication for the Fw P-number,
which is still unknown then.
I know, that those numbers, which are quite probably just drawing numbers, were given as project numbers in several
publications, for example in Novarras volumes "Die deutsche Luftrüstung", but it should be confirmed before taken as a
hard fact nevertheless.

 

[hesham]

OK my dear Jens,


I agree with you,those are a drawing numbers,not designations,I think that's
a good analysis.

 

[Stargazer]

My theory is that the prefixes such as 0310- may indicate the design bureau or maybe simply the office or facility from which the designs emanated. The second number would then indicate that this was, for instance, the 310240th drawing to be done by that office or team. Just my two cents.

 

[blackkite]

Hi! Focke-Wulf Triebflügel(pinion)
Luft46 says that....
"This Focke-Wulf VTOL (Vertical Take Off and Landing) fighter/interceptor was designed in September 1944. The three untapered wings rotated around the fuselage and had a gradually decreasing pitch towards the wingtips, thus acting like a giant propeller. At the end of each wing was a Pabst ramjet, Since ramjets do not operate at slow speeds, either the rotor had to be driven by a fuselage mounted takeoff-booster or small Walter rocket engines could have been fitted to each ramjet pod. The pilot sat in a cockpit near the nose and the armament consisted of two MK 103 30mm cannon with 100 rounds plus two MG 151/20 20mm cannon with 250 rounds. Although the Triebflugel was not constructed, a wind tunnel model was tested up to a speed of Mach 0.9. "

You can see small Walter rocket engine in engine drawing.

Wikipedia...
https://en.wikipedia.org/wiki/Focke-Wulf_Triebfl%C3%BCgel

https://www.youtube.com/watch?v=WxVWH9mOYGA

 

[Johnbr]

CIOS report XXVI-6 “Focke-Wulf Designing Offices and General Management Bad Eilsen”, contained several blueprints of the Focke-Wulf Triebflugel and its engines. The Triebflugel was a vertical-takeoff, ramjet-powered, helicopter-plane hybrid, bomber interceptor developed by Focke-Wulf.

 

[nuuumannn]

Whilst wiling the time away during lockdown I began watching the Marvel Cinematic Universe films, some of them for the first time and I noticed that the baddie in Captain America; The First Avenger flees a scene in one of these. Take a look at Marvel's reimagining of the Triebflugel. If you don't want to watch the whole scene, skip to 2:42.

 

[raidenace45]

After reading the David Myhra book I still do not understand how fuel would get to the rotor/wings when they have to rotate , did they intend to have the fuel tank spin with the rotating assembly ? If not how would the fuel lines work ? Thank you in advance for any response.

 

[Mike Pryce]

"CIOS report XXVI-6 “Focke-Wulf Designing Offices and General Management Bad Eilsen”"

Is there a PDF of that anywhere?

 

[Grey Havoc]

On another note, a couple of old youtube videos (from 2007 and 2011, respectively), the second one was made by David Myhra incidentally, I think with the help of the animator on the older video:

View: https://www.youtube.com/watch?v=bqqQ48KFXJE

View: https://www.youtube.com/watch?v=WxVWH9mOYGA

 

[Justo Miranda]

After reading the David Myhra book I still do not understand how fuel would get to the rotor/wings when they have to rotate , did they intend to have the fuel tank spin with the rotating assembly ? If not how would the fuel lines work ? Thank you in advance for any response.

The fuel system used the same principle as the pressurized fluid used in variable pitch propellers.

 

[raidenace45]

So when I look at a variable pitch propeller diagram it does not show how fluid from a stationary line connects to a line that is spinning , which is what you would have with a fuel line before it connected to some type of manifold leading to each rotor tip. Also the line I would assume would have to be in the center to get as close to zero rotation which would mean it will have to go through the center of the variable pitch mechanism. This is what I am having trouble understanding. Thank you for your response. Also does David Myhra frequent this site , maybe he could shed some light on this ?

 

[Arjen]

David Myhra passed away in December.

 

[Zoo Tycoon]

So when I look at a variable pitch propeller diagram it does not show how fluid from a stationary line connects to a line that is spinning , which is what you would have with a fuel line before it connected to some type of manifold leading to each rotor tip. Also the line I would assume would have to be in the center to get as close to zero rotation which would mean it will have to go through the center of the variable pitch mechanism. This is what I am having trouble understanding. Thank you for your response.

I don’t know how FW where going to do it but I would use a rotating fluid coupling on the fuselage centerline, three orthogonal outlets to pipes running up the blades. A bit demanding for the seals but hey there’s a war on and things are not looking rosey.

 

[Justo Miranda]

So when I look at a variable pitch propeller diagram it does not show how fluid from a stationary line connects to a line that is spinning , which is what you would have with a fuel line before it connected to some type of manifold leading to each rotor tip. Also the line I would assume would have to be in the center to get as close to zero rotation which would mean it will have to go through the center of the variable pitch mechanism. This is what I am having trouble understanding. Thank you for your response.

I don’t know how FW where going to do it but I would use a rotating fluid coupling on the fuselage centerline, three orthogonal outlets to pipes running up the blades. A bit demanding for the seals but hey there’s a war on and things are not looking rosey.

Hi

 

[raidenace45]

First off I am sorry hear of David Myhra's passing , he will be missed. Thank you to all for the information. I looked up rotary unions as I was unaware of them and was amazed that they are even used for casting operations with molten steal. But the device explains everything I had questions about. At least now I can look at this project as being at least possible. Good day !

 

[T. A. Gardner]

So when I look at a variable pitch propeller diagram it does not show how fluid from a stationary line connects to a line that is spinning , which is what you would have with a fuel line before it connected to some type of manifold leading to each rotor tip. Also the line I would assume would have to be in the center to get as close to zero rotation which would mean it will have to go through the center of the variable pitch mechanism. This is what I am having trouble understanding. Thank you for your response.

I don’t know how FW where going to do it but I would use a rotating fluid coupling on the fuselage centerline, three orthogonal outlets to pipes running up the blades. A bit demanding for the seals but hey there’s a war on and things are not looking rosey.

The problems with this design don't end there. We know from US experiments with wingtip ramjets on helicopters like the Hiller Hornet that these are very thirsty and give the aircraft a very short range. Both would have been issues for the Germans, particularly the high fuel use given their shortages to begin with.
Then there is trying to land this aircraft. Convair built the XFY Pogo using a similar take-off and landing position.



While take-offs were easily accomplished, landings were a terrifying and dangerous maneuver for the pilot. Trying to land in windy conditions was nearly impossible. The rate of descent was not easily judged and if too high would result in a crash. It was adjudged even in service only the most highly skilled pilots could fly the plane.

None of that argues in favor of the Focke Wulf design.

 

[raidenace45]

I said "possible"not likely. From what I have read fuel could have been the coal slurry type which would have helped the fuel constraints but even if workable it probably would have required years of development . Also the vehicles and specialized trailers to move them for deployment and on occasion retrieval would have taxed an already over loaded infrastructure. Another problem is late war development was toward missile armament which likely could only be mounted in the nose area limiting it's punch. But let's be honest most of these Luft 46 were born in desperation and events had already passed them by. If the war was going well for the Germans they would have continued making more conservative designs. So I am not one to say "If they could have got this or that built it would have changed the war" the very reason these projects were pursued made that unlikely.

 

[Temistocle]

A very detailed article on the Triebflügel in Flieger Revue X N.104 (pp. 50-61)

 

[Wurger]

A very detailed article on the Triebflügel in Flieger Revue X N.104 (pp. 50-61)

I've seen that TF drawing in one of Dan's bookazines.

 

[hesham]

My dear Jemiba,


the source of Focke Wulf FW.354 is the book; Rotorcraft of the Third Reich

In the Flieger Revue Extra 104,they aren't sure about this designation.

 

[fightingirish]

A very detailed article on the Triebflügel in Flieger Revue X N.104 (pp. 50-61)

Here an appetizer from their website.
Link: https://www.fliegerrevuex.aero/geheimprojekt-focke-wulf-triebfluegel/
Today I bought myself the newest issue of the German magazine "FliegerRevue eXtra 104" at my newsagent near my local train station.
IMHO I find the article about Robert Bartini and his aircraft projects more interesting so far.

 

[Tonton-42]

To fantasize about this trapanelle :

https://static.planetebd.com/dynamicImages/album/cover/large/19/65/album-cover-large-19659.jpg

 

[F.L.]

trapanelle

A nice "french word" !

 

[Justo Miranda]

Senkrechstarter Jagdflugzeug concept​

After the Bodenplatte Operation, only 1,300 German airplanes continued fighting. They were turbojet propelled machines Arado Ar 234, Messerschmitt Me 262 and Heinkel He 162 and a hundred Messerschmitt Me 163 rocket fighters that used sonderkraftstoff (experimental propellants).

As German fuel reserves declined, the OKL cancelled a large number of aircraft projects; first the heavy bombers, then the piston fighters and finally the turbojet-powered aircraft that required long runways. They also eliminated the rocket fighters with landing skids when the experience gained with the Messerschmitt Me 163 proved that their low mobility on the ground made them extremely vulnerable to strafing attacks by enemy fighters.

Finally, the VTOL was the only option left and the German designers were forced to imagine new aerodynamic solutions.

The Forschungsfürung (Fo Fü) was an OKL department for leading all research carried out by the aeronautical research institutes DVL, FGZ, LFA, LFM, AVA, TAL, DFS, FKFS and FFO that formed the most powerful scientific organization in the world. It consisted of four senior scientific leaders: Prandtl, Georgii, Seewald and Bäumker.

By early 1944 Professor Walter Georgii and Oberst Siegfried Knemeyer, director of the Research and Development Institute of the Luftwaffe, initiated contacts with several aeronautical companies looking for ideas for the construction of a Senkrechtstarter Jagdflugzeug (tail sitter VTOL fighter) that could operate independently of the runways.

In the late 1930s, Dipl. Ing. Otto Muck, of Siemens, patented a project of tailsitter aircraft with contra-prop airscrews, but in 1940 a team of engineers from AVA-Göttingen calculated that a VTOL aircraft of 5 tons would require 4,000 hp power to lift-off, an engine that did not exist at the time.

In January 1944 Daimler Benz built a twenty-four cylinders engine with 3,800 hp, called DB 613, formed by two DB 603 G engines coupled together to drive a single-shaft power with contra-rotating airscrews. But the set weighed two tons and was not useful to propel a VTOL aircraft.

In the last days of the World War II, high power and reasonable weight was just a dream; piston engines weighed too much and jet engines had very little thrust.

Lacking engines with sufficient power, Heinkel’s designers attempted to increase the efficiency by using ducted propellers, based on those of the Italian experimental aircraft Caproni Stipa, and annular wings based on the aerodynamic theories of Dipl.-Ing. Helmut Graf von Zborowski.

Inside an annular wing the tapered duct compressed the propeller’s airflow applying Bernoulli’s principle. As the air forced into the Venturi duct it accelerated.

Annular wings with ducted propellers were advantageous in augmenting engine thrust and in providing additional lifting area in forward flight. This meant that a larger propeller with a greater pitch did not require more engine power.

By incorporating adjustable control surfaces and varying the cross-section, the duct increased thrust efficiency by up 90 per cent in comparison to a similar-sized propeller in free-air.

It must be made rigid enough though, not to be distorted under flight, combat, and landing loads.

A VTOL fighter needed that engine power to be delivered with rapid response even at the highest power levels.

The thrust needed to get off the ground had to exceed aircraft weight, but it was necessary for the power plant to provide additional thrust for vertical maneuvering.

A typical value for total thrust needed for vertical acceleration and maneuvering in the other axes would be about 1.7 times the aircraft maximum weight. On the contrary the thrust required in cruising flight would be only a fifth of aircraft weight.

In December 1944, Dr.-Ing. Gerhard Schulze and Dipl.-Ing. Kurt Reiniger fron Heinkel-Wiener Neustädter Flugzeugwerke, designed two tailsitter fighters with annular wing called Heinkel He 355A Lerche and Heinkel He 355 B Wespe.

In February 1945, the VTOL project Lerche was proposed to the RLM in three different versions: Leuchter Jäger Lerche I (24.2.45), Schlachtflugzeug Lerche II (25.2.45) and Schwerer Jäger Lerche III (24.2.45).

Focke-Wulf Triebflügeljäger
​

In 1940, Professor Erich von Holst discovered the aerodynamic principle of the radial lift force, by which wings rotating around the longitudinal axis of the aircraft provided lift and thrust. In May 1944, he designed a Senkrechtstarter Jagdflugzeug for the firm Focke-Wulf. It was a helicopter with contra-prop rotors in the nose, probably equipped with one Argus As 413 engine. Unlike the tailsitter designed in 1938 by Otto Muck and by the American Arthur M. Young in 1941, the von Holst helicopter lacked fixed wings, flying in horizontal position with the tail depressed to transform part of the thrust into lift.

In 1942 the Austrian engineer Friedrich von Dobhloff, of Wiener Neustädter Flugzeugwerke, started the development of the jet-propelled gyrocopter WNF 342 with a two-bladed tip-driven rotor. The propulsion elements were two combustion chambers made of a chromium-nickel-steel alloy, where they burned B4 fuel mixed with compressed-air at 2,000º C, at a stoichiometric fuel/air ratio of 1:20. For horizontal flight propulsion, the WNF 342 used a conventional piston engine that also powered an Argus As 411 supercharger, sending 0.7 kg of compressed-air to the combustion chambers every second. Vertical control was achieved by varying the rotor speed, but the system had problems of ground-resonance vibration caused by the even number of rotor blades.

During the flight tests carried out in 1943, it was found that the compressed-air system limited the thrust and by early 1945 it was decided to replace the combustion chambers with rotor mounted ramjets.

After being examined by engineers of General Electric Corp in September of 1946, the basic design of the WNF 342 was used in several models of North American gyrocopters during the 1950s. The new propulsion system exhibited powerful lifting capacity. In 1953 the Bensen Midget could lift four times its weight and the Hughes XH-17 flew with a gross weight of 23 tons. This feature would have been very useful for the air defense of the Reich during the last year of the war in Europe.

American bombers flew together in self-defensive formations over the Reich, taking the risk that one huge explosion would destroy all the planes in the 'box', which rarely happened when a bomb bay was hit by one of the million shells fired by the Flak. The Germans called this situation Pulkzerstörer but lacked a weapon strong enough to achieve this effect regularly. None of the 55,000 anti-aircraft guns used by the Flakartillerie could launch the 2,000 kg of high explosive needed for the destruction of a ‘box’. The 88-mm Flak 41 fired shells of only 9.4 kg, the Flak 39 of 105-mm 15.1 kg and the Flak 40 128-mm 26 kg, out of which only 10 per cent were HE. The warhead of a Wasserfall ground-to-air missile weighted 235 kg only and that of an Enzian weighted 300 kg.

At the end of 1944 the suicide bombers Focke-Wulf Ta 154 A-0/U2, Gotha P.55 and Messerschmitt Me 328 SO were designed. They could carry out Pulkzerstörer missions loaded with 2,000 kg Amatol. In the May/April 1975 issue, the German magazine Luftfahrt International published the drawing of an unknown gyrocopter, named Flakmine V7, with a circular body and an eight-blade rotor propelled by four ramjets, which looked like a machine designed to lift-off a great charge of explosives.

It is possible that this propulsion system would have inspired Focke-Wulf designers during the planning of their second senkrechtstarter jagdflugzeug project. In the summer of 1944, Dipl.-Ing. Flugbaumeister Heinz von Halem and designer Ludwig Mittelhüber designed the Fw Nr. 310240-0061 gyrocopter with a freely spinning two-bladed rotor that was propelled by tip-ramjets, a system called the Triebflügel (thrust-wing).

On ground, the aircraft was kept upright over four tailfins and the rotor was rotated in neutral pitch by means of a small ground engine, until the wingtips reached the necessary speed for the ignition of the ramjets. For the lift-off, the pilot varied 3-degrees the incidence angle of the blades. It was expected that after the lift-off the blades rotated 87- degrees, acting as un-tapered wings with conventional air foil. It was also considered to use small turbojets, but the idea was dismissed because the acceleration of Coriolis negatively affected its operation. On the contrary, the ramjet, with no moving parts, compresses the air and adds fuel by means of its shape and movement through the air, without being affected by the changes in the angular velocity.

The narrow landing gear track and rotor above the center of gravity affected the stability of the aircraft floor, the use of a pair of blades rotor produced ground resonance effect and the fuselage could only contain enough fuel for a few minutes flight.

In September 1944, the original design was modified by increasing the diameter of the fuselage and the capacity of the fuel tanks and by using a new three-bladed rotor. The project was renamed Fw Nr. 310240-004 Triebflügeljäger. Its considerable weight gain was offset by redesigning the landing gear, adding a central wheel with a powerful shock absorber. The outer wheels were installed at the end of the extensible supports that increased the runway, improving stability during landing.

Hans Multhopp joined the design team and with his usual disdain for the safety of the pilots, proposed to install the rotor behind the cockpit, at a 37 per cent fuselage length. The mechanical device that actuated the rotary collar was replaced by three Aniass-Raketen (Walter 109-509 B-0 bi-propellants rockets) of 350 kg thrust each, installed in the air-intake of each ramjet in 1. Einbauvorschiag configuration. When the correct rotation speed of 220 rpm was reached, the ramjet would start, and the rockets were shut down. The blades were designed with variable incidence so that they continued to generate lift during horizontal flight even with 90 degrees pitch at the root.

In October 1944, the project was re-named Fw Nr. 310240-005 and several safety mechanisms were added.

In case of emergency the blades could be disengaged by explosive bolts before the pilot operated the ejection seat.

The ramjets were very vulnerable to the defensive fire of the Allied bombers: a single impact of 12.7-mm could alter the aerodynamic properties of the outer coating creating flameout and destructive vibrations in the rotor. It was estimated that the rockets would ensure emergency power, but the drag generated by the ramjets would prevent safe landings by autorotation with unacceptably high sink rate. The solution consisted in using explosive devices to detach the ramjets, changing the Aniass-Raketen location to the trailing edge of the blades, inboard the ramjet, in 2. Einbauvorschiag configuration.

The forward section of the fuselage, 320-cm length, would be made of light alloy and would house the pressurized cockpit, with ejector seat, EZ 42 gyroscopic gunsight and ZFR 4a telescopic gunsight. The electronic equipment was housed under the cockpit floor: FuG 24 SE, FuG 25a, FuG 101a, FuG 120K, FuG 125a, Patin PKS and RF2C rear-periscope. The armament (angled down 6 degrees) was to both sides of the cockpit and consisted of two Mauser MG 151/20 cannons, 250 rounds per gun, and two Rheinmetall-Borsig MK 103/30 cannons with 100 rounds per gun. The ammunition tanks were located behind the cockpit. The protection for the pilot consisted of a 15-mm thick armored nosecone, containing one MG BSK 16 gun camera, one 50-mm thick armored glass windshield and two 12-mm steel plates behind the back and head.

The rotary collar, made of steel, would have had a 160-cm of diameter and 82-cm of length. It housed the rotor roller-bearings, the hydraulic actuators of the collective pitch system, the electric generator, the fuel, and propellants pumps, one rocket-propellant tank with 380 liters of T-Stoff, another with 70 liters of C-Stoff and the evaporation plant. The rear fuselage section, with 533-cm of length, would have been made of steel and light alloy and housed two tanks with 1,800 and 1,400 liters of ramjet-fuel, the central steel tube, the main wheel shock-absorber and some electronic equipment.

The cruciform tailfins, with 32-degrees sweepback angle and four rudders, housed the hydraulic retraction systems of the auxiliary wheels with 5.4 meters (extended) track. The landing gear was made of a central wheel 780 x 260-mm, one main shock-absorber with 50-cm play and four auxiliary wheels of 300 x 150-mm. All wheels were steerable, with swivel mounts to facilitate ground towing. They were enclosed by streamlined tulip-shaped pods during flight. In flight configuration, the overall length was of 9.35 meters.

The rotor blades, 436-cm long and with 114-cm parallel-chord, would be constructed entirely in steel with a tubular main spar containing the rocket propellant ducts, ramjet propellant and electric cables for explosive bolts located at both ends of each blade. Those located in the root were used to detach the rotor and those installed in the tips served to detach the ramjets in auto-rotation emergency landing.

The rotor had a maximum diameter of 11.76 meters and a disc surface of 108.56 sq. m. It was designed to rotate freely, and no torque was transmitted to the fuselage. In level flight, the pitch at the root varied automatically to maintain a constant rotation speed of 120 rpm. During lift-off and landing the (subsonic) rotation speed would be 220 rpm.

The Triebflügeljäger used three Pabst ramjets, 70-cm in diameter and 140-cm long, entirely built of steel. Each had 35 injectors and a thrust of 840 kg, with operating speed between 300 km/h and 0.9 Mach and 18,000 meters estimated ceiling. The specific fuel consumption rate varied with the speed of rotation and the type of fuel used. With hydrogen, it was 1.47 at 0.8 Mach and 900º C, with crude oil (superheated and vaporized to achieve rapid mixing with the incoming air) was increased by about 3 per cent.

Ramjets would run on any combustible medium which could be vaporized, passing through the heat exchanger designed by Otto Pabst. It consisted of a tiny ramjet that worked with petrol 133/5000, consuming only a 2 per cent of that of the main engine, and could process substances that were as little volatile as lignite tar and pitch oil. The high fuel consumption, compared to piston or turbojets engines, was caused by the subsonic speed at the rotor tips. The low compression ratio of the air intakes generated inefficient combustion, high noise, poor range, high night-time visibility and induced current effects.

The circular movement of the ramjet left a low-pressure zone behind. To prevent the formation of vortex and destructive vibrations on the external face of the nozzle, an aerodynamic fence of 56-cm length was installed in the area. The three rockets could be run for 200 seconds using a mixture of T-Stoff (highly concentrated solution of hydrogen peroxide) and C-Stoff (57 per cent methyl alcohol, 30 per cent hydrazine hydrate and 13 per cent watery solution of potassium cuprocyanide). T-Stoff and C-Stoff were unstable and dangerous hypergolic substances which reacted explosively on contact, so an ignition device was not needed.

During the rocket’s ignition, the rotor tips had neutral pitch and their roots a 30-degrees negative pitch. The generated negative lift avoided a premature take-off before all the ramjets operated at full power. When the rotor reached the 220 rpm the pilot disconnected the electric-driven pumps from the rockets and gradually increased the collective pitch angle to perform the take-off. The transition to forward flight was made at 300 meters of altitude and 120 rpm, increasing the rotor pitch up to 90-degrees at the roots and 120- degrees at the tips. The higher thrust lift ratio was obtained by flying with the tail depressed 6-degrees, therefore the armament and gunsight were also installed with 6-degrees down with respect to the longitudinal fuselage axis. With a range of only 500 km, the Triebflügeljäger was considered a point defense interceptor that would only start the flight when detecting a bomber stream near its base.

Once the service ceiling had been reached, it should be directed towards the target following the instructions of the Reichsjägerwelle communications network via the FuG 120K device. The MK 103/30 heavy cannons were powerful enough to destroy a four-engine bomber with only five hits of 30 x 184B Minengeschoss ammunition and could be fired from a safe distance of 1,500 m, using the ZFR 4a telescopic gunsight. The MG 151/20 rapid-fire cannons and the Adler gyroscopic gunsight were more useful in dogfight against the escort fighters.

An experienced pilot could perform some conventional fighter maneuvers with the Triebflügeljäger: using the collective pitch he could stop its advance by easily changing direction and even flying backwards, and he could also avoid combat because of its superior rate of climb. Hovering under the bomber stream could shoot at the belly of the planes from a safe distance, out of the reach of their ventral turrets. Guided by the FuG 125a radio-beacon receiver, the pilot could return to his base to hide the aircraft. A base that might be a section of an autobahn surrounded by forests and signaled with ground radar-reflectors as a reference for the FuG 101a radio-altimeter.

The small diameter of the auxiliary wheels suggests that the gyrocopter would be towed from the landing site to the maintenance area, through a network of tarmac path. There the ground crews would attach stairs to both sides of the fuselage to replenish oxygen, ammunition, fuel pumps, B4 petrol from the evaporation plant, heavy kerosene from ramjets and rocket propellants. Afterwards, the fighter would be towed to one of the take-off sites covered by nets stretched between the trees.

Data on the semi-automatic landing procedure planned for the Triebflügeljäger have not been kept. It might be expected that it could have used part of the ‘blind bomb’ and ‘level bomb’ electronic equipment developed for the Arado Ar 234 and adopted by the firm Focke-Wulf for its project 1000 x 1000 x 1000 bomber. After making the transition to the vertical flight on the landing area, the pilot would connect the three-axis Patin PKS autopilot and the Lofte tachometric bomb-sight rear periscope. Both devices acted together driving the airplane according to the pilot movements over the bombsight.

The rate of descent to 120 rpm would be regulated by varying the rotor pitch until reaching the landing point predicted by the computer. To get a view of the ground from the cockpit, it would have been necessary to modify the RF2C rear-periscope by installing the PV1B sighting head at the end of a retractable tube that would be long enough to save the visual obstacle of the rotating collar. The FuG 101a radio-altimeter, designed for horizontal flight, used two ‘inverted T' dipoles that normally were installed under the wings of the big airplanes, but the Triebflügeljäger would require that they were installed in the tailfins for its use during vertical landing.

The indications of the FuG 101a were only reliable for altitudes above 200 meters due to the phenomenon of interference between the transmitter dipole 'S' and the receiver 'E', suggesting that the final descent step would be carried out manually by the pilot following indications from the ground crews. The conclusion is that the Triebflügeljäger had to operate from well-provided bases of fuel, towing vehicles, reflectors, communications equipment, and ground crews. This dependence made it less effective than the Bachem Natter, which only needed a truck, six men and a launching ramp hidden among the trees.

Small numbers of FuG 103 pulse-modulated radio-altimeters, without altitude limitation, were produced in 1945. Therefore, FuG 101a could be dispensed with.

The probable electronic equipment for a Luftwaffe fighter in 1945 would have been:

EZ 42 Adler gyroscopic gunsight Zielgerat developed by Askania/Zeiss. Automatically computed the deflection angle required to hit a target when both aircraft were maneuvering.

FuG 24 SE VHF Funksprechgerät R/T device developed by Lorenz for single seat fighters and operation frequencies between 37.8 and 47.75 MHz. It was used in combination with the ZVG Zielflugrorsatzgerät direction finder device. It had a power of 5 Kw, VHF wave, whip antenna and a weight of 18 kg.

FuG 25a Erstling IFF device Kenngerät manufactured by GEMA and Brinkler

Emission frequency of 160 MHz, reception frequency of 125 MHz. Its rage was of 100 km, had a power of 600 W, a rod antenna under the fuselage (300 mm long) had a 10 degrees rear swept and responded to Freya, Würzburg and Gemse ground control radars. It could be used to calculate the distance of an airplane from the ground radar. The need to operate in several frequencies between 0.53 and 2.40 meters considerably delayed its entering into service with the Luftwaffe. It was used in combination with the EGON (Erstling-Gemse-Offensive-Navigation), for radio navigation of bombers, and with the FuMG 401A Freya LZ radar, as an alternative to the Y-Gerät. Its weight was of 12 kg.

FuG 101a Feinhöhermesser of 1.5 Kw, radio-altimeter developed by Siemens/LG

Operation frequencies between 337 and 400 MHz in continuous wave and frequency modulation (CW-FM with a 2 m error). It had a power of 1.5 W, a weight of 16 kg, and a range between 150 and 1,500 meters. It used two Sender S101 and Empfänger E 101 dipoles to transmit and receive.

FuG 120a Bernhardine radio beacon teleprinter developed by Siemens to receive the emissions from the rotating beacon FuS An 724/725 Bernhard (30-33.3 MHz). The data were presented over a band of printed paper to diminish the efficiency of the enemy interference systems. The FuG 120k was a simplified version for single seat fighters.

The FuG 120 could be used in combination with the FuG 10 K2 and FuG 16 radio transmission system and with the EBl3 receiver of the Funklandegerät Fu Bl2 blind landing system. It had a range 5 at 400 km.

FuG 125a Hermine radio-beacon receiver was developed by Lorenz. It operated in frequencies between 30 and 33.3 MHz with a precision of 5-degrees. Its weight was of 10 kg and its range of 200 to 250 km. It operated in combination with the FuG 16 ZY Zypresse direction finder and the FuG 16 R/T device using the antenna and the D/F loop and Morane mast from these devices. It received the emissions from the FuS An 726 Hermes and could be used in combination with the FuG 120 K Bernhardine to receive emissions from the FuS An 724/725 Bernhard. Combined with the EBl 3F system acted as radio landing device. The data was presented in audio via earphones.

The movement of the ramjets and the high temperature of the exhaust gases in this type of gyrocopters used to ionize the air causing corona dischargers and induced current effects. The electromagnetic phenomenon called evanescent field could affect the operation of electronic equipment, so it is assumed that most antennae would be installed in the front section of the fuselage. The radio-altimeters in the tailfins should be retractable or located inside the tulip-shaped landing gear pods to avoid interference. The Triebflügeljäger should use static-electricity dischargers wicks in the wing trailing-edges and rudders, and ground contact whips.

Focke-Wulf Fw 354 Triebflügeljäger technical data​

Estimated maximum speed of 1,000 km/h at sea level, 900 km/h at 7,000 m, 840 km/h at 11,000 m. Initial climb rate: 125 m/sec. Service ceiling: 14,000 m. Empty weight: 2,800 kg. Maximum lift-off weight: 5,175 kg. Range: 500 km at 675 km/h and 14,000 m. Endurance: 42 minutes at sea level.

 

[Justo Miranda]

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