Vought XF5U "Flying Pancake

[wuzak]

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.

 

[nuuumannn]

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.

 

[nuuumannn]

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..."

 

[chuter]

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.

 

[nuuumannn]

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.

 

[NVSMITH]

-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.