Pneumatics Systems

[Military Man]

Hi there

I was just wanting to ask if anyone has any information about the maintenance of aircraft pneumatic systems. I have been looking around the internet and in various text books and can only find a very small amount of information on this subject. Any help would be greatly appreciated.

Thanks a lot

[fruitloop]

Military Man,Due to the fact that only a few A/c still use Pneumatic systems data will become harder to get,Any particular questions in mind ??

[mono]

Military Man,Due to the fact that only a few A/c still use Pneumatic systems data will become harder to get,Any particular questions in mind ??

Rubbish!

Just about every large transport a/c uses or has pnuematic systems. How do you think they maintain cabin pressure, heat the cabin, start the engines, de-ice the wings/engines and a vast number of other things?

Military man, to be honest there is very little maintenance on these systems these days. Ducts, etc are all 'on condition' items. There will be periodic replacement of filters and traps and the function checks of valves, etc. There will also be leak checks carried out whenever any of these systems is disturbed for maintenance action. That's about it!

[B73567AMT]

Very basic, but very good...

http://www.amtbooks.com/airframe_textbook.htm

[Military Man]

Thanks, i have A & P tech and i must say it is a useful book but does not describe the working of the system in much detail as you say.

I have a couple of questions

1. Does an air bleed valve remove contaminants and gases in order to allow use of air for the ECS and deice or is that process doen at the filter.

Also, how exactly does the air travel through the system once it has came out of the comrpessor, through bleed valve, unloading valve, shuttle valve, moisture seperator, dessicantr and check valve and filter. I am not too sure what happens to the airflow once all of the tanks are full.

I understand its a bit of a heavy question but any input would be greatly appreciated.

Thanks in advance

[fruitloop]

My apology,I thought you were refering to pneumatic's as opposed to hydraulics (e.g landing gears,brakes etc Harrier)
After reading the question I'm now confused !! Are you refering to air regards de-icing,anti-icing,air-conditioning-pressurization or for operating systems (you mentioned a tank)eg.brakes etc.

[Military Man]

I am referring to pressurisation of the emergency system, primary bottle and brake system on startup of the aircraft

Final question, lol

In an aircraft which does not have a hydraulic system and obtains all of its power from pneumatics, how does th emergency pneumatic system work?

Does this involve the use of a control valve?

[B73567AMT]

MM
You have got to be a bit more specific.
What type of airplane and exactly what system are we talking about??

Emergency Pneumatic System??

[spannersatcx]

In most modern a/c the hudraulic brake system has an accumulator that is charged to a nominal px say 1000psi of n2 and is not charged by the a/c pnuuematic system.

I think you are referring to something like the shackleton where it had a pneumatic braking system, of which I don't have a clue how it works.

[fruitloop]

Military Man, I think I now know where you are coming from regards pneumatics !!!! Yes the give a way was the water trap and dehydrator. One A/C that comes to mind is the F27 (not the -50).Engine gearbox driven compressor (4 stages) 2 pipes off the compressor (3rd and 4th stages) 4th stage goes through the water separator,dehyradrator and is then t-ed into the regulator and main supply (the regulator dumps 3rd stage when the required pressure is obtained,reducing load on the compressor)Air is then supplied to a common supply pipe (individual check valves per engine) to All 3 bottles at the same time (main,emergency and brake bottles)ensuring they are equal.On the F27 there is an Isolation Bar which can be pulled which will isolate the main bottle and the brake bottle so the emergency bottle can be charged up first.Emergency down-pressure is the same as normal down except it uses different plumbing.Emergency braking bypasses the Maxarets(anti-skid) and reaches full pressure in a pre-determined time,so its either on or off depending on how long it has been selected on (pressure gauges tell the crew how much line pressure is being supplied) In the emergency brake system there is a pressure reducing valve and a on-off control valve.
I hope I've answered the question with-out confusing you too much
Cheers