Question about the thrust reversers

[Avro]

Good evening everybody,

http://www.airliners.net/open.file/0976721/L/

When watching this picture I was asking myself a question. Are the actuators for the "petals" of the thrust reversers driven by pneumatics ? And if yes, what is the pressure used to open them ? Are there intermediate positions available or just on/off positions ?

Thanks

Chris

[realplaneshaveprops]

I can give you some more information about the thrust reversers on A320 family by monday evening.

Koen

[Avro]

I can give you some more information about the thrust reversers on A320 family by monday evening.

Koen

Thanks Koen

However you don't need to dig out too much info. I just wanted to know whether the actuators operate wih pneumatics or hydraulics and the pressure involved

Chris

[earthman]

Good evening everybody,

the actuators for the "pedals"

Petals, not pedals, as in the colourful leave-like things on flowers.

[sab319]

I know that the petals can be opened without reverse thrust, since a lot of company's use them to help the plane slow down without using reverse thrust (to save on fuel)

[Avro]

Petals, not pedals, as in the colourful leave-like things on flowers.

Petals indeed. Sorry for the mistake it was late and I was tired

I know that the petals can be opened without reverse thrust, since a lot of company's use them to help the plane slow down without using reverse thrust (to save on fuel)

I think you are talking about idle reverse aren't you ? Anyway if the petals are extended there will always be some reverse thrust since the petals will re-direct the bypass air towards the front of the plane. So it's not possible to extend the petals without having reverse thrust !!!

Chris

[Bilboone]

These type of " petals " or we call them blocker doors are operated by hydraulics. Other type of aircraft like A330 and A300 have pneumatic operating thrust reversers, the exact opening pressure I can't find it directly for A320

[Avro]

These type of " petals " or we call them blocker doors are operated by hydraulics. Other type of aircraft like A330 and A300 have pneumatic operating thrust reversers, the exact opening pressure I can't find it directly for A320

Thanks for your answer Bilbo. I wouldn't call them blocker though, since for me the blocker door is a sliding door and is associated with the cascade mechanism, but I might be wrong ...

Chris

[realplaneshaveprops]

I can confirm that the thrust reversers on the A320 are hydraulically operated, didn't found the pressure. (Had a quick look in the AMM)

Koen

[janhuub]

Hydraulic pressure on the A320 is 3000 PSI

Greetz,

Jan

[realplaneshaveprops]

Hydraulic pressure on the A320 is 3000 PSI

Greetz,

Jan

That is correct, but that doesn't mean that the thrust reverser actuators operated at 3000 PSI. Pressure can be reduced for some components.

Koen

[Avro]

I can confirm that the thrust reversers on the A320 are hydraulically operated, didn't found the pressure. (Had a quick look in the AMM)

Koen

Thanks for the answer Koen

[Avro]

Hydraulic pressure on the A320 is 3000 PSI

I'm not familiar enough with PSI numbers but I assume it's equivalent to 21MPa ?

Anyway, Since I know now that they work on hydraulics.

Can someone give me the pressure in a pneumatically operated reverse ?

Thanks again

Chris

EDIT: just checked myself and indeed 3000 psi is equal to 20.6 MPa

[Bilboone]

For CF6-50C2 engine (A300B4)
The source of air for the thrust reverser system comes from the fourteenth stage compressor and goes through the ground check valve, this valve allows to operate the T/R on ground without engine running but with air supplied from apu, the only thing i could found is the outlet pressure ( that goes to the pneumatic drive for T/R) of this ground valve is about 55 psi +/- 5 psi

[Avro]

Ok many thanks Bilbo

Chris

[regi]

hm, I can imagine the importance of the quality of seals. A lot of Freudenberg I assume?

[regi]

I was a bit surprised to read that pneumatics are also used. Is Festo doing something for airplanes as well?

[earthman]

The power generated by engines comes in the form of bleed air, which is compressed air, and as a result many systems on aircraft are pneumatic.

[Avro]

The power generated by engines comes in the form of bleed air, which is compressed air, and as a result many systems on aircraft are pneumatic.

Not totally correct You have shaft power and bleed air which you can use.

Bleed air is indeed used in many applications such as anti/de icing, environmental control systems etc....
But in general it isn't used very often to drive actuators. It has namely quite some disadvantages. The only region where it is used to drive actuators, is inside or near the engines (such as reversers - hence my question) .

The reasons why pneumatics aren't used very often in actuators are multiple. The available pressures are low and most of all, fluid compressibility makes the position of the actuator strictly dependent on the external load and then its control is difficult. The air-operated actuators are those with two positions only (on/off) and low external loads.

Now as stated above actuators in engines are often pneumatically operated since the use of hydraulic oils may be critical due to the very high temperatures.

It's interesting to see that some types have hydraulics operating the reversers and others pneumatics.

Chris

[earthman]

I doubt you need a lot of force to open those petals, probably more to prevent them from opening by themselves or to prevent them from being ripped off when they are open. After all, there is pressure on them from the inside (bypass air) and the airflow around the engine would actually help opening them.