The official aviation quiz topic!

MD-11 · Post by **MD-11** » 11 Dec 2005, 17:13

Extended range for Twin Engine Operations
But this answer was already given by me on another question. So if I'm correct I give my turn to Avro

I see he was already before me with his correction.

SN_Bigbirdy · Post by **SN_Bigbirdy** » 11 Dec 2005, 17:28

Avro wrote: i always tend to use the other one it's shorter :p

Chris

hehe

how do we call it when somebody doesn't do anything more then he wishes to? lazy?

it's completely correct Avro, you are cleared for TO, have a nice flight

Simon

Avro · Post by **Avro** » 11 Dec 2005, 17:38

SN_Bigbirdy wrote:
hehe how do we call it when somebody doesn't do anything more then he wishes to? lazy?

OK the Boeing model 201 Super Guppy was derived from the Boeing 377 Stratocruiser, by installing the huge bulb on the fuselage.

Explain why the cruise speed of the Gupy was only 290mph while the cruise speed of the stratocruiser was 375mph ?

Chris

fokker_f27 · Post by **fokker_f27** » 11 Dec 2005, 18:36

Because the Guppy is much larger.

SN_Bigbirdy · Post by **SN_Bigbirdy** » 11 Dec 2005, 20:31

I would say that the Guppy is less aerodynamic then the Stratocruiser (thanks to the bulb?)

fokker_f27 · Post by **fokker_f27** » 11 Dec 2005, 21:46

That too.

Avro · Post by **Avro** » 11 Dec 2005, 21:49

SN_Bigbirdy wrote:I would say that the Guppy is less aerodynamic then the Stratocruiser (thanks to the bulb?)

nearly... keep trying

fokker_f27 · Post by **fokker_f27** » 11 Dec 2005, 21:53

Did it maybe have to be more careful?

Avro · Post by **Avro** » 11 Dec 2005, 22:18

No it has nothing to do with that.

Keep searching on the aerodynamic shape of the plane as mentioned above. I'm sure you'll find an answer..

Chris

SN_Bigbirdy · Post by **SN_Bigbirdy** » 11 Dec 2005, 22:25

because the bulb was larger in volume on the Super Guppy as on the Stratocruiser?

Avro · Post by **Avro** » 11 Dec 2005, 22:39

Yes the bulb was larger, but my question is why does the cruise speed decrease when adding such a big bulb.
Maybe I didn't express mysekf very well in my question - sorry

Chris

realplaneshaveprops · Post by **realplaneshaveprops** » 11 Dec 2005, 23:06

Well, in an aerodynamic point of view, the big bulb increases the aerodynamic drag a lot. So with the same engines (thrust), the cruise a,d maximum speed are lower

Koen

Avro · Post by **Avro** » 11 Dec 2005, 23:10

realplaneshaveprops wrote:Well, in an aerodynamic point of view, the big bulb increases the aerodynamic drag a lot. So with the same engines (thrust), the cruise a,d maximum speed are lower

Koen

Indeed. Due to the high bulb the flow will be accelerated over it. At the top of it the flow velocity will be maximum and will be higher than the speed of sound. those supervelocities at the top of the bulb will induce some high drag due to the local shockwaves. To reduce this amount of drag the cruising speed is simply reduced.

Your turn

Chris

realplaneshaveprops · Post by **realplaneshaveprops** » 12 Dec 2005, 11:42

http://coppermine.luchtzak.be/displayim ... =502&pos=0

What can you see in the middle of the picture ( the thing on the exhaust of the core engine).

What is it
What's the purpose of that thing

Koen

Avro · Post by **Avro** » 12 Dec 2005, 11:55

It's a device mixing the cold and slow bypass air with the hot and fast core air. By having such a form you increase the effective area which will be used for the mixing.

Thanks to this mixing you will reduce the noise of the engine by reducing the shear which otherwise is quite big between the slower fan flow and fast core flow.

Chris

SN_Bigbirdy · Post by **SN_Bigbirdy** » 12 Dec 2005, 11:59

It features exhaust design featuring mixer and an integrated nozzle for good efficiency (this design is also found in IAE V2500 series and on some Rolls-Royce RB211 series) and it also features the unique 'petal' thrust reversers rather than the conventional cascade design. This is due to the A340 requirements of maximum range and efficiency.

I don't know if this is correct but I think that you should have erased the name of the photographer

Simon

Avro · Post by **Avro** » 12 Dec 2005, 12:25

SN_Bigbirdy wrote:it also features the unique 'petal' thrust reversers rather than the conventional cascade design.

Are you sure ?

AFAIK there are two basic types of thrust reversers in use:

- Target- or bucket-type reversers
- Cascade reversers.

The latter one can be of the clamshell (B727), blocker door(B767 etc..) and "petal" type with internal or external cascade baffles.

Cascade reversers have the advantage that the exhaust flow can be better directed into optimum directions. They are however heavier and require more maintenance.

This would mean that the petal type is in fact a cascade reverser !!

Chris

realplaneshaveprops · Post by **realplaneshaveprops** » 12 Dec 2005, 13:03

Avro was the first with the correct answer, so he's next

Koen

Avro · Post by **Avro** » 12 Dec 2005, 13:07

Ok let's assume we have a twin turboprop plane. (something for you Koen

)

Let's also asume that we are looking at the plane from the back and that both engines are turning clockwise.

Which one of the engines is called the critical engine when the other one fails? (looking from the back)

And why is one of the engines more critical than the other. ? During one engine ops

Chris

SN_Bigbirdy · Post by **SN_Bigbirdy** » 12 Dec 2005, 16:28

doesn't it has to do with the fact that one engine provides the energy for airsupply for the pax during the flight?

Simon