HS.681 - What might have been

Chris558 · Post by **Chris558** » 01 Jul 2006, 21:55

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.

ianhind · Post by **ianhind** » 01 Jul 2006, 23:13

Now which governement was it that cancelled that?

Hint: about the same time the TSR2 was cancelled.

Post by **Rick Piper** » 01 Jul 2006, 23:22

Hi Chris

I'm guessing the AW.680 was the double decker one ?.
Makes the single decker look pretty in comparison

Regards
Rick

VC10 · Post by **VC10** » 02 Jul 2006, 12:37

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

TobyV · Post by **TobyV** » 02 Jul 2006, 13:10

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

andy · Post by **andy** » 02 Jul 2006, 13:20

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:

Chris Trott · Post by **Chris Trott** » 02 Jul 2006, 14:06

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.

VC10 · Post by **VC10** » 07 Jul 2006, 12:45

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,

TobyV · Post by **TobyV** » 07 Jul 2006, 14:02

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.