Reply to: An airplane on a treadmill: will it take off?

[ASB]

I believe that is a debate that should be resolved within its own Thread.

Yes, I do seem to have inadvertantly hijacked this. 'Twas the fault of the original poor spec.

[Drewster]

What is the 'business end' of a harrier?

Is it the pilot's seat or is it the place he's shooting at?

I believe that is a debate that should be resolved within its own Thread.

[Mich the Tester]

somebody who has spent considerably more time at the business end of one than you.

What is the 'business end' of a harrier?

Is it the pilot's seat or is it the place he's shooting at?

[ASB]

Oh dear. I think someone has heard a word 'injestion' and confused it.

The problem with VTOL on the harrier is the risk of sucking it's own exhaust back in.

There's your clue, now carry on arguing. You all are quite amusing in a clueless kinda way.

I imagine you're right. I was only describing how it was described to me in laymans terms by somebody who has spent considerably more time at the business end of one than you.

[Menelaus]

My understanding (possibly wrong) from my old mates dad (who did some of the original handover to the USM as it happens) is that full VTOL is awkward because even with full tanks there is the risk of what he decribed as "impeller contamination". He said (I paraphrase) vertical thrust can be lost and flight can be compromised. I undestand (again possibly wrongly) that the hover - whilst very impressive - was very expensive and gave quite a lot of guranteed downtime. The most impressive bit for me was the backwards VTOL.

As it happens a mate of mines hubby got seconded to the RN in the falklands. He was not popular for parking one at the bottom of the south atlantic after the Argentinians had figured the combat time of a harrier was not great and a second wave of SE's could cause a certain amount of mayhem. Came back through the swiss diplomatic mission.

Edit: when they still had the phantom squadron at Coningsby they were impressive to watch rotate with ab's on.

29 Sqdn and 228OCU? I was at RAF Coningsby in the early 1980s and seeing the aircraft take off on full after-burner reminded me of the joke of two pigeons sitting at the end of Coningsby runway, one saying to the other "Wouldn't you like to be able to fly that fast?" to which the other replies "Well, you would if your arse was on fire!".

viz Harrier at VTOL - can be done but as others have mentioned its astonishingly wasteful of fuel and to the best of my knowledge is now only done at air displays as a matter of course. I'd imagine the people at RAF Wittering teach it though before pilots go off to JFH at RAF Cottesmore.

viz "ingestion of exhaust" for Harrier - I've not heard of this (not that this means it doesn't happen) but I've seen an A-10 at a range firing its main cannon with such ferocity that (a) it appears to be hanging in mid air (recoil) and (b) the exhaust gasses from the cannon have caused the engines to need to be relit in mid flight.

[threaded]

Oh dear. I think someone has heard a word 'injestion' and confused it.

The problem with VTOL on the harrier is the risk of sucking it's own exhaust back in.

There's your clue, now carry on arguing. You all are quite amusing in a clueless kinda way.

[TykeMerc]

It's difficult and astonishingly noisy, but it's done. The risks of ingestion of ground crap are mitigated by using a large, very sturdy and brushed off concrete apron. The noise really is impressive as is the fuel consumption in vectored flight, they don't have massive fuel tanks either as they weren't designed for long range duties and it's a design of compromises.

The pilots and the aerodromes prefer STOL which is fantastic to watch, doesn't spit bits of ground at high velocity and a hell of a lot quieter.

Seeing them with the engine stripped out is interesting too as there's bog all left apart from the tail, stubby wings and cockpit.

[ASB]

I've seen them do full VTOL takeoffs, hovers and landings, they're only done when the water tanks are full and the ground is clear or ideally several inches (8-12ish) thick concrete.

My understanding (possibly wrong) from my old mates dad (who did some of the original handover to the USM as it happens) is that full VTOL is awkward because even with full tanks there is the risk of what he decribed as "impeller contamination". He said (I paraphrase) vertical thrust can be lost and flight can be compromised. I undestand (again possibly wrongly) that the hover - whilst very impressive - was very expensive and gave quite a lot of guranteed downtime. The most impressive bit for me was the backwards VTOL.

As it happens a mate of mines hubby got seconded to the RN in the falklands. He was not popular for parking one at the bottom of the south atlantic after the Argentinians had figured the combat time of a harrier was not great and a second wave of SE's could cause a certain amount of mayhem. Came back through the swiss diplomatic mission.

Edit: when they still had the phantom squadron at Coningsby they were impressive to watch rotate with ab's on.

[TykeMerc]

Fair cop.

But, if memory serves a Harrier won't normally actually do full VTOL (from a mates dad who Menelaus might just know from Gutersloh in a different life for both of). The reason being ingestion of crap, so there is at least a chance, that the treadmill as it is destroyed might not be ingested. But, yes, if it was it would be embarassing. Still assumes engines though.

I've seen them do full VTOL takeoffs, hovers and landings, they're only done when the water tanks are full and the ground is clear or ideally several inches (8-12ish) thick concrete.

[ASB]

As pointed out VTOL via Harrier engine wouldn't be practical as it wasn't stated that the treadmill was indestructible.

Mind you it wasn't stated that the aircraft had engines so it's necessary to make far too many assumptions for the question to be answered.

Fair cop.

But, if memory serves a Harrier won't normally actually do full VTOL (from a mates dad who Menelaus might just know from Gutersloh in a different life for both of). The reason being ingestion of crap, so there is at least a chance, that the treadmill as it is destroyed might not be ingested. But, yes, if it was it would be embarassing. Still assumes engines though.

[TykeMerc]

Quite. But VTOL wasn't excluded by the question was it?

As pointed out VTOL via Harrier engine wouldn't be practical as it wasn't stated that the treadmill was indestructible.

Mind you it wasn't stated that the aircraft had engines so it's necessary to make far too many assumptions for the question to be answered.

[ASB]

Ah but that is lift in the form of thrust from the Pegasus engine, not lift created by difference in air pressure created by the distance the air has to travel over the surface of a wing compared with that travelling under it.

Quite. But VTOL wasn't excluded by the question was it?

[Churchill]

One of my favourite aircraft, the Fieseler Storch, was once landed on a tennis court to rescue Mussolini, and then took off again with him on board.

Now, one must admit that he was even fatter than Churchill, so a treadmill would not be too much to carry.

Oi fatso, nice try! Yow is considerably more fatterer than me.

[TimberWolf]

In answer to (ii) it won't take off if the thrust is only enough to counteract the treadmill friction of the wheels but assuming normal conditions and the fact that aircraft wheels are designed to have little friction any aircraft should be able to overcome the treadmill with ease no mater how fast it went, the only limiting factor is how fast the wheels could turn before they disintegrate.

Imagine standing on a treadmill with a pair of roller skates on, would it take a lot of effort to hold onto the side and keep stationary? Now someone gives you a rope to hold whilst they pull, would it take much effort on their part to pull you forward?

If the plane is going at the same speed as the treadmill, i.e. it is not moving with respect to the ground, it has no airspeed and will not take off.

[gingerjedi]

The poll answers reflect the correct answer. It will take off or not take off depending on how you interpret the question. That is:

(i)The plane could of course take off if you don't care about it matching the speed of the treadmill, this is unlike how treadmills are usually used, and the treadmill is a red herring. You would need a bit more power to take off than usual.
(ii) The plane will not lift off the treadmill if their speeds match (i.e. if the plane is stationary on the moving treadmill) as there is no lift on the wings.

In answer to (ii) it won't take off if the thrust is only enough to counteract the treadmill friction of the wheels but assuming normal conditions and the fact that aircraft wheels are designed to have little friction any aircraft should be able to overcome the treadmill with ease no mater how fast it went, the only limiting factor is how fast the wheels could turn before they disintegrate.

Imagine standing on a treadmill with a pair of roller skates on, would it take a lot of effort to hold onto the side and keep stationary? Now someone gives you a rope to hold whilst they pull, would it take much effort on their part to pull you forward?