XF5U/V-173 "Flying Pancake"

[sequoiaranger]

Do we REALLY need go any further??? I mean, this thing **IS** a "whif" all by itself, with no need of any alteration, isn't it???

Well, since I can't leave ANYTHING alone, I made (just some photo-trickery--not a model) a two-seat trainer I will call the "Halibut" (I think it is obvious WHY!).

I do intend to build the fine Hasegawa kit someday, with "camo" from an Aunt Jemima pancake mix box--that is, the top surface of the aircraft will be painted tan-and-brown-and-yellow to look like a stack of pancakes with butter and syrup on them!!!

Hey! Can you guys loosen my strait-jacket so I can take my meds? 

[Weaver]

Heh - it would make a fine advertising hoarding for everything from pancakes to pizzas to frizbees to LPs......

[jcf]

You could do a turbojet-powered 'plane-in-every-garage' version.

http://blog.modernmechanix.com/2007/12/24/the-flying-flapjack/



Jon

[dy031101]

Someone (not me of course) beats GTX to it.

[GTX]

Someone (not me of course) beats GTX to it.

- what's the story behind it?

Regards,

Greg

[dy031101]

- what's the story behind it?

That I have no idea. 

[kitnut617]

Seeing this thread just happens to coincide with me reading my copy of the Ginter book on the 'Pancakes'.  Very interesting but some comments made by an engineer in the aviation field after 1990, says he doubts it would have been very successful.  He points out the complicated drive shaft arrangement it had with two 90 degree gearboxes and the cross connection would probably have been it's undoing, given in light that all the gearbox problems various other projects had.

I find the aircraft very interesting indeed though, I've got the Sword kit of the V-173 and the Hasegawa XF5U-1 (both in 1/72 scale) and I wonder if instead of having radial engines and two 90 degree gearboxes, it could have had a couple of Napier Sabres but angled so there would have been one gearbox at around 45 degrees. Just some of my thoughts.

[PhaseSpace]

I read those comments too and I thought they were a bit unfair. The person in question was a Bell helicopter engineer and might have been transposing the problems of helicopter transmission to the Pancakes. On the Pancake the transmission is not transferring all the torque needed to generate lift as in a helicopter just enough for thrust. Since they are inherently twin engine aircraft the gearboxes only have to handle 50% of the torque needed for thrust. This is a lot less than for a single rotor helicopter's gearbox. Also other Pancake designs from Vought have the need for only a single right angle turn by using a transverse mounted inline engine.



This is something I had written into a Communist Germany WW2 AH I have been working on for a while until I dumped it for something a bit more obscure and likely (less of a blatant theft from the USA). In my AH I had the two transverse engines joined by a cross shaft joining their rear ends. Though I doubt this would be too effective if one of the engines seized up you couldn't drive power through it to the other propeller.

The biggest problem a Pancake would have on a flight deck is the danger of two exposed and spinning props. But the advantage of having a carrier aircraft able to fly at the same speed as the carrier is huge.

[PR19_Kit]

Hindsight is the world's only exact science of course..... 

With current day gearbox tech it would have worked a treat I'm sure, viz the V-22 which has almost exactly the same arrangement and has to pivot the 'props' as well. The XF5U-1 was just 40 years ahead of its time..........

[Librarian]

Just wanted to pick up on this thread as I'm considering a whif of the XF5U. We're dealing with propeller technology from the early/mid-forties so I can fully understand the necessity of those very long blades considering the aircraft's flight envelope. Could the same flight characteristics have been accomplished with a shorter but broader propeller such as:

https://www.hannants.co.uk/product/QB48337

Looking for any excuse to shorten those tooooo long u/c legs

[Dizzyfugu]

You need more blades, not certain about the depth. AFAIK the propellers were very similar to a helicopter's rotor construction (e .g. a UH-1's), and when you take a careful look at the props you will recognize that they are actually composed of two pairs of two-bladed rotors that are set in front of each other and mounted at 90° to each other. O.K., it's whifworld, after all, but I guess that these things were not easily replaced... And the high angle was also necessary in order to direct the air stream downwards and under the fuselage for lift. I doubt that the F5U could take off in a "normal" way!?

[KJ_Lesnick]

You know a larger attack variant would be useful... wings a bit larger, bigger engines with higher horsepower (R-3350's to R-4360's), and possibly an internal bay...

[Air21]

I've got more than just the Guiles book on this subject, Zimmerman saw the applications as a flying truck with even LONGER legs and a hinged belly pallet for cargo that lowered like a drawbridge, used to deliver quickly goods to factory yards and job sites... So, helicopter work.

What the design needed was transverse inline engines.  The gearbox there would be a simple transmission of two side by side gears and an overrunning clutch, cutting out one ninety degree turn.  Everything becomes more aerodynamic with an unobstructed lifting body.

As for propellers, 1/144 scale V-22 prop rotors would be the correct size on a 1/72 flapjack.  It would be neat to see one with it's big rotor blades folded for carrier stowage.

Some ideas for Flapjack Wiffs:

Air racer with transverse engines and a gaudy paint scheme

Weather Research aircraft... The storm hunter that can't stall and crash with lots of probes and sensors hanging off of it

Helicopter Escort... Imagine if Skyraiders could Sprint to the scene then drop in low and super slow looking for downed pilots or enemy positions.  Think of that SEA scheme!

[KJ_Lesnick]

kitnut617

Seeing this thread just happens to coincide with me reading my copy of the Ginter book on the 'Pancakes'.

For everybody, the ISBN-13 is 978-0942612219; ISBN-10 is 0942612213

Very interesting but some comments made by an engineer in the aviation field after 1990, says he doubts it would have been very successful.  He points out the complicated drive shaft arrangement it had with two 90 degree gearboxes and the cross connection would probably have been it's undoing, given in light that all the gearbox problems various other projects had.

At the penalty of sounding stupid, would the problems have been maintenance intensive?  I do know the V-173 flew...


Air21

I've got more than just the Guiles book on this subject

This might make me sound dumb, but I can't find this online...

Zimmerman saw the applications as a flying truck with even LONGER legs and a hinged belly pallet for cargo that lowered like a drawbridge, used to deliver quickly goods to factory yards and job sites... So, helicopter work.

Now that's interesting

What the design needed was transverse inline engines

Would a turboprop work?

Helicopter Escort... Imagine if Skyraiders could Sprint to the scene then drop in low and super slow looking for downed pilots or enemy positions.  Think of that SEA scheme!

Sounds like a really good idea...

[Air21]

Whoops, I meant Ginter 

I'm sure a turboprop would work fine, or more appropriately a turboshaft.  Two General Electric T700 turboshafts would weigh 1/3 of the two R2000 Twin Wasps the XF5U was designed for with anywhere from the same to double the horsepower.  Then you'd have parts commonality with Apaches and Blackhawks, Cobras, NH90's... Anything it was flying to escort would be using the same engine and parts.

The vibration in operation came from the very long drivetrain.  The Osprey has a common shaft connecting both motors but it's made up of a bunch of smaller linked shafts coupled with universal joints.  The rotor head is also a funky sandwich of some elastomer and metal shells, the whole thing just sort of flexes under load from the lift dissimmetry.  The new AH-1Z and UH-1Z rotor hubs work similarly.  If it's something your interested in you might want to Google it though, I'm no expert.

But it would seem that the o e engineer they quoted might not have been totally correct.

I also have a NASA study on using cyclic control on airplane propellers to generate directional forces. The XF5U having only two propellers couldn't get all it's controls made by the propellers but it might be easier to handle that way.

I like imagining it with a big red hurricane emblem on its back and an armored windscreen blasting through storms.  Like This guy!