Simviation Forum - A380 Reversers

Reply #15 - Apr 17^th, 2005 at 4:32am

Craig. Offline
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Poor old Craig. It seems you've been misunderstood again. Not sure what that was all about but never mind

LOL. It happens, alot Roll Eyes

I dont hate the A380, but we all know my feelings on Airbus Lips Sealed

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That's cause the Nimrod was not so loosely based on the Comet.

nooooooo waaaayy, Shocked

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Reply #16 - Apr 17^th, 2005 at 4:57am

French Connection Ex Member
Forza Lazio!!

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Looking thorugh Google for A380, something interesting popped up...See for your self:

Tongue

Strictly speaking however, it kind of does resemble the A380...

Cheers,
Ashar Grin

&&SS Lazio Website

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Reply #17 - Apr 17^th, 2005 at 7:06am

Vic Offline
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It was the American way of doing it. If the first Comet's didn't have their nasty habit of disintegrating at cruise altitude then the chances are the British design of having the engines in the wings would have caught on. Tongue

I think that the comets actually disintigrated because of the structure of fusulage, not the engine placement. The windows on the first comets were square and they were bolted into place (d'oh) like the DC-3 and the older prop planes. This would cause warping and this gave it it's habit of disintigrating. As we all know, a rectangular structure is one of the weakest, the strongest being a circle and then a triangle.
To prove my point - look at the Tupolev 104, 124. They had engines in the wing but had circular windows, and they never disintigrated. (The 104 was the second commercial jet after the comet).
The engines placed in the wings have a different problem - in the case of an engine fire, the wing has a habit of melting and the fire does a good job of spreading to the rest of the aircraft. I am not even going to start about what happens in the case of an engine explosion Grin

Fortunately, the latter never happened on a 104.

A380 Reversers:
Everyone here is correct in a way. As mentioned, engines 1 and 4 hang over the edge of the runway. The danger isn't with anything being SUCKED into the engine (if you think about, it has nothing to do with reversers, since ALL of the engines are at TO/GA thrust anyways) besides, engines can withstand grass and dirt being sucked into the engines. As someone already mentioned - The problem is when reverse thrust is activated, the the airflow from the engines goes downwards and it is pretty strong. This airflow can rip out clotches of dirt with grass, which are then THROWN at a very high velocity (by the airflow) toward the fusulage. They aren't really afraid of FOD to the engines, but damage to the body.
The only effect this will have on its landing performance is that it may not be able to use some of the earlier taxiway exits. To be certified, it has to stop on a dry runway WITHOUT the use of reversers. Besides, spoilers do a better job of stopping than you think.
Vic

When you ASSUME, you make an ASS out of U and ME.

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Reply #18 - Apr 17^th, 2005 at 7:14am

Hagar Offline
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I think that the comets actually disintigrated because of the structure of fusulage, not the engine placement.

I don't think Woody was suggesting that. It's well-known what caused the problems with the Comet. Without these problems the Comet would have been a world-beater & it's quite possible other manufacturers would have followed suit. I think this is unlikely as later British airliners (including the HS Trident which was originally a DH design) had their engines mounted externally at the rear of the fuselage. The Vickers VC10 is another example.

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Reply #19 - Apr 17^th, 2005 at 7:50am

Vic Offline
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Sorry for the misunderstanding.
It really is a pity also, I heard that DH used the square windows in part because it would give the passengers a better view!
Vic

When you ASSUME, you make an ASS out of U and ME.

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Reply #20 - Apr 17^th, 2005 at 8:23am

Craig. Offline
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It was inevitable engines became external. Just look at the size of them.

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Reply #21 - Apr 17^th, 2005 at 8:52am

Vic Offline
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It was inevitable engines became external. Just look at the size of them.

True, although it would be entartaining to see a 777 with internals Grin

When you ASSUME, you make an ASS out of U and ME.

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Reply #22 - Apr 17^th, 2005 at 9:52am

Hagar Offline
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It was inevitable engines became external. Just look at the size of them.

You have a very good point there Craig. At the time the Comet & similar aircraft were designed, axial-flow gas turbines were thought the way to go. These were more powerful than the original centrifugal-flow gas turbines & their much smaller diameter is what allowed them to be mounted integrally in the wing roots. They also have a much smaller diameter than the far more economical & quieter turbofan engines that were later developed & in use for many years now. As you say, it wouldn't be practical to mount one of those huge engines in each wing root, never mind two.

Someone mentioned that the turbofan actually goes back to the idea of the original Whittle gas turbine so once again we came round in a big circle.

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Reply #23 - Apr 17^th, 2005 at 4:24pm

Woodlouse2002 Offline
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nooooooo waaaayy, Shocked

It's true. Unbelievable, but true. Grin

Woodlouse2002 PITA and BAR!!!!!!!!&&&&Our Sovereign Lord the King chargeth and commandeth all persons, being assembled, immediately to disperse themselves, and peaceably to depart to their habitations, or to their lawful business, upon the pains contained in the Act made in the first year of King George the First for preventing tumults and riotous assemblies. God Save the King.&&&&Viva la revolution!

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Reply #24 - Apr 18^th, 2005 at 2:42pm

C Offline
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The engines placed in the wings have a different problem - in the case of an engine fire, the wing has a habit of melting and the fire does a good job of spreading to the rest of the aircraft. I am not even going to start about what happens in the case of an engine explosion

Search google for XW666 - and see what you get - I haven't looked myself...

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Reply #25 - Apr 18^th, 2005 at 2:45pm

C Offline
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Sorry for the misunderstanding.
It really is a pity also, I heard that DH used the square windows in part because it would give the passengers a better view!
Vic

I expect they used square windows as they were the norm. Incidentally I think that at the Comet crashes were caused by fatigue in the windows in the top of the cabin...

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Reply #26 - Apr 18^th, 2005 at 6:53pm

Hagar Offline
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I expect they used square windows as they were the norm. Incidentally I think that at the Comet crashes were caused by fatigue in the windows in the top of the cabin...

From what I've read on the subject the big square (rectangular) windows were a feature to improve passenger appeal. This was insisted on by top management at DH, possibly the old man himself, despite warnings from engineers who happened to see what was going on. The Comet was designed & built in secrecy & many people commented on it when they first saw it. I don't think any other pressurised aircraft was ever designed like that, even before the results of the investigation after the fatal accidents were published. Any boiler engineer could have told them you don't have square openings on a pressurised chamber & it's difficult to know what they were thinking of. I also think a lot of the truth was covered up by the government of the time. The success of the aircraft had been regarded as a matter of national importance.

I can't quote any sources but this was always my understanding of this tragedy.

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