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HS.681 - What might have been
Posted: 01 Jul 2006, 21:55
by Chris558
In this months issue of 'Air Enthusiast', there is a feature about this proposed RAF Tactical Transport Jet, intended instead of the Hercules, and looking like a not-so-ugly C-17.
There's also a small cutaway drawing of the economical alternative, the Turboprop AW.680 - an enlarged 'sexy' looking Argosy.
Posted: 01 Jul 2006, 23:13
by ianhind
Now which governement was it that cancelled that?
Hint: about the same time the TSR2 was cancelled.
Posted: 01 Jul 2006, 23:22
by Rick Piper
Hi Chris
I'm guessing the AW.680 was the double decker one ?.
Makes the single decker look pretty in comparison
Regards
Rick
Posted: 02 Jul 2006, 12:37
by VC10
ianhind wrote:Now which governement was it that cancelled that?
Hint: about the same time the TSR2 was cancelled.
Don't forget the supersonic Harrier
Posted: 02 Jul 2006, 13:10
by TobyV
Cancelling the supersonic Harrier probably wasnt a bad idea though, for one it was a technically unrealistic project that if it had been allowed to proceed, would probably have been cancelled at a later stage and then there wouldnt have been a subsonic Harrier either.
I still cant see how they would get around the problem of having a 2 engine with vectored nozzle design and what happens if you get a single engine failure whilst in the hover? I would have thought it would become a large and rather nasty Catherine wheel

Posted: 02 Jul 2006, 13:20
by andy
TobyVickers wrote:.
I still cant see how they would get around the problem of having a 2 engine with vectored nozzle design and what happens if you get a single engine failure whilst in the hover? I would have thought it would become a large and rather nasty Catherine wheel

I think the only way around that, would be to vector both engines through the same nozzles, so if one fails, you just end up with 50% power. :think:
Posted: 02 Jul 2006, 14:06
by Chris Trott
Which would end up with the result that Dassault had when they had an engine failure on their Mirage IV-VTOL testbed when several of the lift engines failed- a squashed airplane.
Posted: 07 Jul 2006, 12:45
by VC10
andy wrote:TobyVickers wrote:.
I still cant see how they would get around the problem of having a 2 engine with vectored nozzle design and what happens if you get a single engine failure whilst in the hover? I would have thought it would become a large and rather nasty Catherine wheel

I think the only way around that, would be to vector both engines through the same nozzles, so if one fails, you just end up with 50% power. :think:
I think that solution would be fraught with problems. If one engine was producing more power for a given throttle angle, due to say one engine being newer than the other or it was hovering in a crosswind, so one intake was blanked, that excess EPR would 'bung' up the the gas exit from the second engine and possibly cause it to surge.
I believe you would require a modern day EEC system to control thrust very accurately for it to work,
Posted: 07 Jul 2006, 14:02
by TobyV
I agree with Paul, two engines close together... attempting and needing to 'work together' is very difficult.. one way or another they will more likely interfere with each other's safe operation, in a variety of ways. I think this is one of the reasons why no further aircraft have been built around the Harrier principle. The Harrier works very well for its size and speed but if you want anything more than that then unfortunately you end up going down the JSF/Yak-41M route.