# Vought XF5U "Flying Pancake



## johnbr (Oct 5, 2017)



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## johnbr (Oct 5, 2017)



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## johnbr (Oct 5, 2017)

Vought XF5U-1 mockup, July 1943

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## johnbr (Oct 5, 2017)




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## johnbr (Oct 5, 2017)




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## johnbr (Oct 5, 2017)

_View: https://www.youtube.com/watch?v=LfpTDOAfj7Y_

 

_View: https://www.youtube.com/watch?v=RcRciqSLzPY_

_View: https://www.youtube.com/watch?v=N2yzoMt6etc_

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## johnbr (Oct 5, 2017)

sxf5u

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## johnbr (Oct 5, 2017)

*Design and development *Vought Website
The XF5U-1 was designed as a land-based or carrier-based fighter to be used with or without a catapult, with an arresting gear. The airplane incorporated certain unusual design and structural features.

The wing, the basic outline of which was defined by two ellipses, so arranged that the major axis of one coincided with the minor of the other, comprised the main structure of the airplane, with the exception of the pilot’s cockpit and the horizontal and vertical tail surfaces. The greater part of the wing surfaces and internal structure was composed of Metalite, a “sandwich” material providing a particularly strong and light type of construction. The four-bladed counter-rotating propellers were driven by cross-shafting and gear boxes connected to both engines. If one engine failed, it could be de-clutched from the system and the airplane flown with the remaining engine and both propellers operating. Circular air intakes in the wing leading edge provided carburetor, engine and oil cooling air. Two vertical tails with rudder and fins provided directional control. Two Metalite ailavators, with trim tabs across 70% of their trailing edge and with balance weights on the tips, provided lateral and longitudinal control. The pilot’s cockpit was a complete monocoque shell with a formed plexiglass canopy. The stick and rudder flight controls were manual except for proportional hydraulic boost to the ailavators.

Neither the first nor second airplane had armament, although there were provisions for six 50-caliber machine guns and ammo boxes. Two Pratt and Whitney R-2000-7 radial engines with cooling fans and superchargers were mounted upright in the wing.

The 16-foot diameter propellers were unique for the time and bear some mention. Because of the activity factor, twist and shape, the props were manufactured by Chance Vought Aircraft of Stratford, Connecticut. The two hydraulically operated, fast-acting, electro-mechanically governed propellers each had four Pregwood blades and load-relieving hubs which differed from the conventional four-way hub in that the blades were free to “flap” in pairs about the shaft axis. Low pitch stop was 15 degrees, high pitch stop was 70 degrees. The propeller pitch control set the left-hand propeller governor mechanism which controlled the right-hand propeller governor mechanism electronically and adjusted the propeller blade angle. Movement of the pitch control lever upward decreased pitch, and downward increased the pitch. Full forward position governed takeoff rpm (2,700): full aft position gave approximately 1,300 rpm in take-off slot and 800 rpm for flight. These were propeller rpm’s. There was also the more conventional throttle control which operated in three slots: “WARM-UP”, “TAKE-OFF” and “FLIGHT”.

Another unique feature of the XF5U-1 was the stability flap, located symmetrically about the centerline of the airplane at the wing trailing edge. The 15 sq. ft. hinged surface required no pilot control but automatically provided for change in airplane trim with change in attitude. The air loads upon the flap adjusted deflection against a spring loaded strut. The stability flap was linked to the tail wheel to insure locking in the up position when the tail wheel was extended.


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## johnbr (Oct 5, 2017)

*Front view. The propeller blades were
black from the root with white stenciling, 
then varnished mahogany with yellow tips. 
The right propeller had Hamilton Standard
oval decals and both propellers had small white “tracking” diamonds on them.*



The letter of intent for the Vought VS-315 (XF5U-1) was issued September 17, 1942. The XF5U-1 was a twin-engine, single-seat, low aspect ratio flying wing type of airplane, manufactured by the Chance Vought Division, United Aircraft Corporation, Stratford, Connecticut.

The first XF5U-1 airplane (Bureau Number 33958) was used for static tests; proof loads, extended to ultimate, largely confirmed structural design predictions. The second XF5U-1 airplane (Bureau Number 33959) was used for experimental flight test and concept validation. It was never flown because many hours of engine run-up showed excessive mechanical vibration between the engine-propeller shafting, gear boxes, and airframe structure. The airplane was taxi tested on February 3, 1947 at Stratford, Connecticut, but, again, vibration levels were considered excessive. 

The airplane was being readied for shipment by sea through the Panama Canal to Edwards AFB, California, when the contract was canceled (March 17, 1947) because of still unsolved technical problems and the lack of Navy R&D money


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## johnbr (Oct 5, 2017)

Vought V-173


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## johnbr (Oct 5, 2017)




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## Wayne Little (Oct 6, 2017)

a real odd one that's for sure.


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## Wurger (Oct 6, 2017)




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## Gnomey (Oct 6, 2017)

Good shots!


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## chuter (Oct 10, 2017)

To prevent wear during the many hours of ground running the rotors were replaced with standard Hamilton Standard four blade props. Because there wasn't a left hand version of this propeller the blades on the left prop were reversed so that it gave reverse thrust, the close-up view of this prop in the second photo of post #1 (wider view post #3 pic 5) shows this as well as any photo I've seen. The reference in post #9 about Hamilton Standard decals only being on the right (forward) propeller may simply not account for the likelihood of decals being on the aft facing side of the left propeller blades. 

This aircraft had the same flight safety requirement of requiring both rotors to keep turning in an engine out situation as the V-22 Osprey and we all know how troubled that development process was. In a practical sense the aircraft was doomed before development started.


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## johnbr (Oct 11, 2017)

The Vought XF5U "Flying Pancake" was an experimental fighter aircraft designed by NACA researcher Charles H. Zimmerman. This unorthodox design consisted of a flat, somewhat disc shaped body serving as the lifting surface, with propellers located on the leading edge at the wingtips. The XF5U-1 was a larger version of the original #V-173 (see alsoV-173 testing).















The project was cancelled in 1947 and the lone V-173 prototype transferred to the Smithsonian Institute.


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## polo1112 (Oct 11, 2017)

Fantastic and never seen (for me) photographs.

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## Old Wizard (Oct 12, 2017)




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## johnbr (Feb 2, 2018)

Assembly breakdown.


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## chuter (Feb 16, 2018)

Just noticed in post @16 the desk model (?) has the rotors wrong-handed.


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## Zipper730 (Feb 17, 2018)

I've seen it at the Paul E. Garber institute...


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## Wildr1 (Feb 27, 2018)

earlier version was known as the Chance-Vought V-173 flying pancake

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## johnbr (Aug 31, 2018)



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## wuzak (Sep 4, 2018)

Just had a though about the engine/gearbox/propeller arrangement.

The XF5U prototype used R-2000 engines. That schematic looks like it has turbines.

The interesting thing about turbines is that the power turbine could be separate from the gas generator section. You could have the power turbine in line with the propellers, while the main part of the engine remains where it is. Weight would be saved by not having the gearboxes and drive shafts.


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## johnbr (Sep 21, 2018)

http://virtpilot.org/files/lib/book126.pdf

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## johnbr (Jan 22, 2019)

*XF5U-1 (Stability)*
643 Test 160 - XF5U-1 (Stability) - NasaCRgis 
643 Test 132 - V-173 - NasaCRgis

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## johnbr (Jan 22, 2019)

Charles H. Zimmerman - NasaCRgis

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## johnbr (Jan 22, 2019)



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## johnbr (Jan 22, 2019)

Spin tests of a 1/16-scale model of the Chance Vought XF5U-1 airplane have been performed in the Langley 20-foot free-spinning tunnel. The effect of control position and movement upon the erect and inverted spin and recovery characteristics ae well as the effects of propellers, of stability flaps, and of various revisions to the design configuration have been determined for the normal fighter loading. The investigation also included spin recovery parachute, tumbling, and pilot-escape tests. For the original design configuration, with or without windmilling propellers, the recovery characteristics of the model were considered unsatisfactory. Increasing the maximum upward deflection of the ailavators from 45 deg to 65 deg resulted in greatly improved recovery characteristics. Dimensional revisions to the original airplane configuration, which satisfactorily improved the general spin and recovery characteristics of the model, consisted of: (1) a supplementary vertical tail 34 inches by 59 inches (full-scale) attached to a boom 80 inches aft of the trailing edge of the airplane in the plane of symmetry, (2) a large semispan undersurface spoiler placed along the airplane quarter-chord line and opened on the outboard side in a spin, or (3) two additional vertical tails 64 inches by 52 inches (full-scale) located at the tips of the ailavators. A satisfactory parachute arrangement for emergency spin recovery from demonstration spins was found to be an arrangement consisting of a 13.3-foot parachute attached by a 30-foot towline to the arresting gear mast on the airplane and opened simultaneously with an 8-foot parachute on the outboard end of the wing attached by a 3-foot towline. Tests indicated that pilot escape from a spin would be extremely hazardous unless the pilot is mechanically ejected from the cockpit. Model tumbling tests indicated that the airplane would not tumble.

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## swampyankee (Jan 22, 2019)

wuzak said:


> Just had a though about the engine/gearbox/propeller arrangement.
> 
> The XF5U prototype used R-2000 engines. That schematic looks like it has turbines.
> 
> The interesting thing about turbines is that the power turbine could be separate from the gas generator section. You could have the power turbine in line with the propellers, while the main part of the engine remains where it is. Weight would be saved by not having the gearboxes and drive shafts.




Part of the reason for gearboxes and driveshafts was to provide cross-shafting, so the failure of one engine wouldn't be quite so unpleasant.

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## CORSNING (Jan 22, 2019)

Great stuff John. Thank you for posting all those great pictures and
information.
Calculated performance and specification of the Vought fighter and 
and prototype:
Standard Aircraft Characteristics Arcive
and scroll down to F5U Flapjack.

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## johnbr (Jan 23, 2019)




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## Gnomey (Jan 23, 2019)

Good stuff!


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## johnbr (Jan 28, 2019)

643 Test 132 - V-173 - NasaCRgis


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## johnbr (Jan 28, 2019)




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## johnbr (Jan 28, 2019)




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## johnbr (Jan 29, 2019)

The XF5U-1 during testing 
Role Fighter 
Manufacturer Vought 
Designer Charles H. Zimmerman 
Status Cancelled 17 March 1947 
Primary user United States Navy 
Number built 2 
Developed from Vought V-173 

The Vought XF5U "Flying Flapjack" was an experimental U.S. Navy fighter aircraft designed by Charles H. Zimmerman during World War II. This unorthodox design consisted of a flat, somewhat disc-shaped body (hence its name) serving as the lifting surface.[1] Two piston engines buried in the body drove propellers located on the leading edge at the wingtips.
Design and development:
A developed version of the original V-173 prototype, the XF5U-1 was a larger aircraft. Of all-metal construction, it was almost five times heavier, with two 1,600 hp (1,193 kW) Pratt & Whitney R-2000 radial engines. The configuration was designed to create a low aspect ratio aircraft with low takeoff and landing speeds but high top speed.

Normally, a wing with such a low aspect ratio will suffer from very poor performance due to the degree of induced drag created at the wingtips, as the higher pressure air below spills around the wingtip to the lower-pressure region above. In a conventional aircraft, these wingtip vortices carry a lot of energy with them and hence create drag. The usual approach to reducing these vortices is to build a wing with a high aspect ratio, i.e. one that is long and narrow. However, such wings compromise the maneuverability and roll rate of the aircraft, or present a structural challenge in building them stiff enough. The XF5U attempted to overcome the tip vortex problem using the propellers to actively cancel the drag-causing tip vortices. The propellers are arranged to rotate in the opposite direction to the tip vortices, with the aim of retaining the higher-pressure air below the wing. With this source of drag eliminated, the aircraft would fly with a much smaller wing area, and the small wing would yield high maneuverability with greater structural strength.
The propellers envisioned for the completed fighter were to have a built-in cyclic movement like a helicopter's main rotor, with a very limited ability to tilt up and down to aid the aircraft in maneuvering. An ejection seat was fitted to allow the pilot to clear the massive propellers in the event of an in-flight emergency. Although the prototype was unarmed, a combination of machine gun
eneral characteristics:
Crew: One, pilot
Length: 28 ft 7 in (8.73 m)
Wingspan: 32 ft 6 in (9.91 m)
Height: 14 ft 9 in (4.50 m)
Wing area: 475 ft² (44.2 m²)
Empty weight: 13,107 lb (5,958 kg)
Loaded weight: 16,722 lb (7,600 kg)
Max. takeoff weight: 18,772 lb (8,533 kg)
Powerplant: 2 × Pratt & Whitney R-2000-7 radial engine, 1,350 hp (1,007 kW) each

Performance:
Maximum speed: 413 knots / 475 mph at 28,000 ft (estimated)[8] (765 km/h at 8,534 meters)
Range: 1,064 miles (1,703 km)
Service ceiling: 34,492 ft (10,516 m)
Rate of climb: 3,000 ft/min (914 m/min)
Wing loading: 35 lb/ft² (172 kg/m²)
Power/mass: 0.16 hp/lb (0.27 kW/kg)
Armament:
6 × .50 machine guns or 4 × 20 mm cannon
2 × 1000 lb. bombs 
s and cannons would have been installed under the nose.


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## johnbr (Jan 29, 2019)




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## johnbr (Jan 29, 2019)




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## johnbr (Jan 29, 2019)




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## chuter (Jan 31, 2019)

Yep, in Post 38 third photo we see the left hand ground run propeller's Hamilton Standard decals facing aft showing the counterclockwise turning blade is thrusting forward (there was no left hand turning version of this propeller). Right hand prop is normal in direction and function. The Pancake's complex rotor drive system (both rotors were tied together - couldn't turn separately - and either engine could be clutched out) was never close to being airworthy and doomed the project.

Also, it looks like World of Warplanes has wrongly modeled the aircraft with Hamilton Standard props which were strictly ground run clubs.


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## Gnomey (Feb 3, 2019)

Nice shots guys!


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## johnbr (Jun 30, 2019)

643 Test 160 - XF5U-1 (Stability) - NasaCRgis


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## Zipper730 (Jul 1, 2019)

chuter said:


> Yep, in Post 38 third photo we see the left hand ground run propeller's Hamilton Standard decals facing aft showing the counterclockwise turning blade is thrusting forward (there was no left hand turning version of this propeller).


So they would have had to make such a propeller?


> The Pancake's complex rotor drive system (both rotors were tied together - couldn't turn separately - and either engine could be clutched out) was never close to being airworthy and doomed the project.


I'm curious if it would be possible to find a picture of the power-train?


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## chuter (Jul 5, 2019)

Zipper730 said:


> So they would have had to make such a propeller?
> I'm curious if it would be possible to find a picture of the power-train?



If they were going to fly the aircraft with standard props, yes, but no, the plane was designed to fly with the complex rotor system seen in other photos, the Hamilton Standard props (of which there was no left hand turning model) were used strictly for ground running to avoid putting needless hours of wear and tear on the expensive bespoke rotors.

I don't recall seeing photos clearly showing the entirety of the drive system but there are diagrams and drawings floating about.

As an aside the V-22 Osprey had the same dual engine/single drive requirement that the Pancake had and I think we all can recall the drawn out development issues (and crashes) that were experienced by that (mandated) program.

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## Gnomey (Jul 8, 2019)

Good shots!


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## swampyankee (Jul 8, 2019)

chuter said:


> If they were going to fly the aircraft with standard props, yes, but no, the plane was designed to fly with the complex rotor system seen in other photos, the Hamilton Standard props (of which there was no left hand turning model) were used strictly for ground running to avoid putting needless hours of wear and tear on the expensive bespoke rotors.
> 
> I don't recall seeing photos clearly showing the entirety of the drive system but there are diagrams and drawings floating about.
> 
> As an aside the V-22 Osprey had the same dual engine/single drive requirement that the Pancake had and I think we all can recall the drawn out development issues (and crashes) that were experienced by that (mandated) program.




Boeing-Vertol had decades of experience with that sort of transmission on its helicopters when it was building the V-22. Vought didn’t, nor was the process of designing and producing high power bevel gears as well known. 

There were a lot of technical issues with the XF5U, the cross-shafting and need for flapping and lead-lag hinges on the propellers being two.


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## nuuumannn (Jul 8, 2019)

wuzak said:


> You could have the power turbine in line with the propellers, while the main part of the engine remains where it is.



Dunno how that's gonna work. The power turbine is driven by the exhaust gases, so it has to be in line with the combustor section.


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## nuuumannn (Jul 8, 2019)

chuter said:


> As an aside the V-22 Osprey had the same dual engine/single drive requirement that the Pancake had and I think we all can recall the drawn out development issues (and crashes) that were experienced by that (mandated) program.



Although the V-22 programme was complex and the rotor system might have caused delays in construction and testing, I don't believe any of the frame losses the Osprey has suffered have been as a result of the complexities of the 'dual engine/single drive system'. Take a look here:

Accidents and incidents involving the V-22 Osprey - Wikipedia


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## wuzak (Jul 8, 2019)

nuuumannn said:


> Dunno how that's gonna work. The power turbine is driven by the exhaust gases, so it has to be in line with the combustor section.



No, it doesn't have to be in line with combustor.

SZR: Z32 Turbocharger based Gas Turbine, MK2.5 

GR-1 Turbojet Project 2/21/04 

A power turbine does not have to be connected to the gas generator mechanically. This makes it a free power turbine, and is used to drive something - a generator, a prop, etc.

The gas generator is a gas turbine, with compressor driven by its own turbine.


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## nuuumannn (Jul 8, 2019)

wuzak said:


> A power turbine does not have to be connected to the gas generator mechanically. This makes it a free power turbine, and is used to drive something - a generator, a prop, etc.



Yeah, I know this, I work on gas turbines. The free turbine is still in line with the combustor though, through concentric shafts. It, as you say is not mechanically linked to the _compressor section_, but it still needs that power from the exhaust, so in a gas turbine that's fitted to an aircraft, not a car turbocharger, has to be in line with the combustor. In, say the PW100 series engines, which I work on, the LP and HP compressors have their own turbine, but the power turbine is separate to them in that it is connected via the reduction gearbox to the propeller, but the turbines are driven by exhaust gases, which means _it needs to be in line with the combustor_.


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## nuuumannn (Jul 8, 2019)

Here's a short clip on the PT-6; you'll notice for one thing that the engine is reverse flow, the intake is at the rear of the engine and the air flow moves forward through centrifugal compressors to the combustion section, after which the turbines are driven by the combusted gases. The power turbine is the foremost connected to the drive shaft that turns the prop, via an RGB:

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## wuzak (Jul 8, 2019)

That's the way it is generally done, but it doesn't have to be.

And it is logical for most applications.


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## nuuumannn (Jul 8, 2019)

wuzak said:


> That's the way it is generally done, but it doesn't have to be.



Not in an aircraft engine. The turbine relies of the energy from the combusted gases. The further you move the turbine away from that heat source, the greater amount of effort to produce a given amount of power, which is just inefficient. In an application like an aircraft engine, it would be foolhardy to do it any other way. Heat is the key, that is why in pure jet engines you have guide vanes and turbine blades that regularly operate in temps greater than their base metal melting points (this is done through efficient cooling).

You need to read the theory behind the operation of the turbine section and the extraction of energy from combusted gases to understand why it doesn't make sense to put the turbine away from the combustor. In aircraft engines and industrial sized gas turbine engines, that's the way it is.


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## Zipper730 (Jul 8, 2019)

Why would you have the exhaust flow backwards? I figure you would want to have the airflow going as straight aft as possible with the minimum number of directional changes.


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## nuuumannn (Jul 8, 2019)

Zipper730 said:


> Why would you have the exhaust flow backwards?



It's just another means of doing the same thing, it creates a compact and light engine arrangement. Note also that the compressor section is also centrifugal flow, again, in the PT-6's case for compactness. An axial flow compressor takes up space. In most (not all) small helicopter and aeroplane turbines the compressor is centrifugal. In the PT-6 the coupling between the turbine and RGB/prop is short, because in every gas turbine there are mechanical inefficiencies in the extraction of energy from the combustor section by the turbine (this is why the turbine needs very hot gases, to maximise efficiency - high temps = high efficiency), so with a reverse flow engine the length of shafts etc can be kept short, which produces a compact yet efficient engine. Note also that the combustion chamber is designed so the gases double back on themselves before they exit the combustor section.

PT-6s are extraordinarily efficient for their size and have enormous application. Take a look at this page, which gives you a list of the applications of this engine.

Pratt & Whitney Canada PT6 - Wikipedia


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## nuuumannn (Jul 8, 2019)

Zipper730 said:


> I figure you would want to have the airflow going as straight aft as possible with the minimum number of directional changes.



In a gas turbine the air doesn't flow straight. It is constantly changing direction to get the most efficiency out of it. In the compressor section and in the turbine section the air is swirled and its direction changed with the use of stators and guide vanes to move that air perpendicular to the linear mechanics of the engine, then back again over the rotor sections of the compressor and turbines. 

There's plenty of links to this stuff on the net.


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## Zipper730 (Jul 8, 2019)

nuuumannn said:


> In a gas turbine the air doesn't flow straight. It is constantly changing direction to get the most efficiency out of it. In the compressor section and in the turbine section the air is swirled and its direction changed with the use of stators and guide vanes to move that air perpendicular to the linear mechanics of the engine, then back again over the rotor sections of the compressor and turbines.


That's why I said "with the minimum number of directional changes".


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## nuuumannn (Jul 8, 2019)

Zipper730 said:


> That's why I said "with the minimum number of directional changes".



Even then, that's not accurate.

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## wuzak (Jul 9, 2019)

nuuumannn said:


> Not in an aircraft engine. The turbine relies of the energy from the combusted gases. The further you move the turbine away from that heat source, the greater amount of effort to produce a given amount of power, which is just inefficient. In an application like an aircraft engine, it would be foolhardy to do it any other way. Heat is the key, that is why in pure jet engines you have guide vanes and turbine blades that regularly operate in temps greater than their base metal melting points (this is done through efficient cooling).
> 
> You need to read the theory behind the operation of the turbine section and the extraction of energy from combusted gases to understand why it doesn't make sense to put the turbine away from the combustor. In aircraft engines and industrial sized gas turbine engines, that's the way it is.



For an installation like I suggested for the XF5U the question is whether the losses are greater in using an offset power turbine or using an in-line power turbine with bevel drive to the props. 

However, I believe it was pointed out earlier in the thread that the geared solution includes connecting one side to the other for redundancy, which would not work with the offset turbine.


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## wuzak (Jul 9, 2019)

nuuumannn said:


> It's just another means of doing the same thing, it creates a compact and light engine arrangement. Note also that the compressor section is also centrifugal flow, again, in the PT-6's case for compactness. An axial flow compressor takes up space. In most (not all) small helicopter and aeroplane turbines the compressor is centrifugal. In the PT-6 the coupling between the turbine and RGB/prop is short, because in every gas turbine there are mechanical inefficiencies in the extraction of energy from the combustor section by the turbine (this is why the turbine needs very hot gases, to maximise efficiency - high temps = high efficiency), so with a reverse flow engine the length of shafts etc can be kept short, which produces a compact yet efficient engine. Note also that the combustion chamber is designed so the gases double back on themselves before they exit the combustor section.
> 
> PT-6s are extraordinarily efficient for their size and have enormous application. Take a look at this page, which gives you a list of the applications of this engine.
> 
> Pratt & Whitney Canada PT6 - Wikipedia



Note that the PT6 has both axial and centrifugal compressor stages.


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## nuuumannn (Jul 9, 2019)

wuzak said:


> For an installation like I suggested for the XF5U the question is whether the losses are greater in using an offset power turbine or using an in-line power turbine with bevel drive to the props.



The losses in efficiency with an offset turbine would be enormous because again, what is it that's driving the power turbine. You need tht heat for greater efficiency. Adding a bevelled drive would just add complexity to the gearbox. You're taking about two different things here.


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## nuuumannn (Jul 9, 2019)

wuzak said:


> Note that the PT6 has both axial and centrifugal compressor stages.



Now, you are just nitpicking, wuzak, and you're just clutching at straws in an attempt to justify your original suggestion. As Elsa said, "Let it go, let it go..."


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## chuter (Jul 11, 2019)

nuuumannn said:


> Although the V-22 programme was complex and the rotor system might have caused delays in construction and testing, I don't believe any of the frame losses the Osprey has suffered have been as a result of the complexities of the 'dual engine/single drive system'. Take a look here:
> 
> Accidents and incidents involving the V-22 Osprey - Wikipedia



You're right. I lived through that without paying much attention to the details ... apparently - lol. However, it looks like the July 1992 crash into the Potomac was driveline related as the results of the investigation led to a titanium firewall protecting the carbon drive shaft due to finding that an engine failure led to a fire which apparently failed the shaft. 

What I do know about the XF5U's transmission is they were never able to get one flight qualified for all the testing and modifying the did to it. It seemed to be either breaking or vibrating. But that was very definitely a different era.


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## nuuumannn (Jul 11, 2019)

chuter said:


> that was very definitely a different era



Sure was, it was a highly ambitious and esoteric programme that was ahead of its time and really, what that aircraft could have benefitted from was gas turbines, but that's how tech advances is by trying new ideas. The V-22 Osprey, despite its faults is a valued asset within the US armed forces and brings a wide range of capabilities to the table. That it was/is troublesome could have almost been expected given its advances over existing technologies, but its the vanguard of that type of system; it's the first of its type and most certainly won't be the last. The next iteration of the tilt-rotor will benefit from all the mistakes and delays brought about through the Osprey's development.

I got talking to some V-22 crews last year at an airshow I attended; it's an amazing piece of kit, astonishingly easy to fly and operate; the crews who do love it. Well, these guys do.


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## NVSMITH (Jul 13, 2019)

-Back to the first photographs: what was the purpose of the clear nose dome? Is that a mock-up radar installation? Later photos apparently show a nose dome clear in the lower hemisphere.


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