Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
JAGflyer
Topic Author
Posts: 3570
Joined: Tue Aug 10, 2004 5:31 am

Packs and Supplementary Air Supplies

Mon Jul 30, 2018 1:27 am

Is it possible for the air conditioning packs (Environmental Control System) to be run off the bleed air supplied by a supplementary source (air start cart)? I have seen several references to air start carts that have an "ECS Mode" so that presumably they can supply air to run the packs for heating/cooling/pressurization testing. I've never heard of an air cart being used to run packs on the 737 during normal operations. Obviously in most cases where the APU is not usable/serviceable, there would be a pre-conditioned air source available for use in cooling/heating the cabin.
If you flew today, thank a Flight Dispatcher!
 
User avatar
Francoflier
Posts: 5216
Joined: Wed Oct 31, 2001 12:27 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 1:56 am

Technically, you can. It is however not recommended, and forbidden by most operators as the cart's air might be contaminated by oil and such... They are not designed to provide breathable air, that's what ground air con is for. :wink2:
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
arcticcruiser
Posts: 433
Joined: Tue Aug 22, 2017 2:16 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 8:26 am

JAGflyer wrote:
Obviously in most cases where the APU is not usable/serviceable, there would be a pre-conditioned air source available for use in cooling/heating the cabin.


You wish... amazed at how difficult that can be at both European and US major airports. I really hate operating with an inop APU to the US. EUR is not much better, with all them limitations on running APUs you would thank they had a good alternate option. But no.
 
User avatar
Starlionblue
Posts: 19876
Joined: Fri Feb 27, 2004 9:54 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 8:43 am

As Francoflier says, you can do it but it isn't recommended.

There are some situations where you'd consider it. For example, if you're at a diversion port and there's no low-pressure air available. You get on board and the cabin is over 30 degrees.

arcticcruiser wrote:
JAGflyer wrote:
Obviously in most cases where the APU is not usable/serviceable, there would be a pre-conditioned air source available for use in cooling/heating the cabin.


You wish... amazed at how difficult that can be at both European and US major airports. I really hate operating with an inop APU to the US. EUR is not much better, with all them limitations on running APUs you would thank they had a good alternate option. But no.


Quite. And even if there's low-pressure air available, in many cases it doesn't really keep up with demand.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Dalmd88
Posts: 3106
Joined: Fri Jul 28, 2000 3:19 am

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 9:11 am

We use air carts or hangar shop air to run the packs for mtc tests. The packs never run at their best with that air source. The volume and temp are lower than engine bleed air.
 
User avatar
Starlionblue
Posts: 19876
Joined: Fri Feb 27, 2004 9:54 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 9:28 am

Dalmd88 wrote:
We use air carts or hangar shop air to run the packs for mtc tests. The packs never run at their best with that air source. The volume and temp are lower than engine bleed air.


Indeed. Which is why when you start the engines on external air you have to check the available pressure.

Since those are "your" air carts, you can guarantee the quality of the air, and you don't have to worry about contamination. A bit of a different story if you end up at a minor port somewhere in diversion-land and they roll up with their rusty old cart which has been sitting outside in the rain for three years doing nothing and started service cranking De Havilland Comets... ;)
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
User avatar
fr8mech
Posts: 7994
Joined: Mon Sep 26, 2005 9:00 am

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 11:25 am

Francoflier wrote:
Technically, you can. It is however not recommended, and forbidden by most operators as the cart's air might be contaminated by oil and such... They are not designed to provide breathable air, that's what ground air con is for. :wink2:


Forbidden? With my operator, It’s actually standard procedure when the APU is inop. We don’t use or own conditioned air carts, since we are a cargo operator. And, in 28’ish years with cargo operators, I’ve never come across an air cart that contaminated a pneumatic system. Can it happen? Sure, just like an engine or APU can contaminate the system.

As stated, air carts aren’t really as efficient as the APU, but they are a suitable substitute for PACK operation and operational checks. It’s how we do it when the aircraft is in the hangar.
When seconds count...the police are minutes away.
Unless it's expressly prohibited, it's allowed.
You are not entitled to a public safe space.
Ego Bibere Capulus, Ut Aliis Sit Vivere
 
User avatar
zeke
Posts: 14900
Joined: Thu Dec 14, 2006 1:42 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 11:38 am

Despite what my colleagues above have written we do at times run the packs at some ports off HP external air. The issue with those units at some ports is the equipment is not designed for delivering HP air for extended times.

It works well when used.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
arcticcruiser
Posts: 433
Joined: Tue Aug 22, 2017 2:16 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 7:11 pm

zeke wrote:
Despite what my colleagues above have written we do at times run the packs at some ports off HP external air. The issue with those units at some ports is the equipment is not designed for delivering HP air for extended times.

It works well when used.


Agreed
 
User avatar
fr8mech
Posts: 7994
Joined: Mon Sep 26, 2005 9:00 am

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 8:49 pm

zeke wrote:
Despite what my colleagues above have written we do at times run the packs at some ports off HP external air. The issue with those units at some ports is the equipment is not designed for delivering HP air for extended times.

It works well when used.


Not to be pedantic, but it’s not HP air, it is low pressure air at high volume.
When seconds count...the police are minutes away.
Unless it's expressly prohibited, it's allowed.
You are not entitled to a public safe space.
Ego Bibere Capulus, Ut Aliis Sit Vivere
 
User avatar
Florianopolis
Posts: 332
Joined: Sun Mar 29, 2015 2:54 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 9:11 pm

Is this hooked up to the HP engine start air source, and routed to the pacs instead of to the engine starter? Or is there a separate HP air hookup for PAC feed air, in addition to the fat yellow hoses that hookup air conditioned air right to the distribution system downstream of the PACs?
 
User avatar
zeke
Posts: 14900
Joined: Thu Dec 14, 2006 1:42 pm

Re: Packs and Supplementary Air Supplies

Mon Jul 30, 2018 10:32 pm

fr8mech wrote:
Not to be pedantic, but it’s not HP air, it is low pressure air at high volume.


It is called “HP Ground Air Supply” in the FCOM. LP Air in FCOM is external PCA that is connected directly to the mixing unit.

Florianopolis wrote:
Is this hooked up to the HP engine start air source, and routed to the pacs instead of to the engine starter? Or is there a separate HP air hookup for PAC feed air, in addition to the fat yellow hoses that hookup air conditioned air right to the distribution system downstream of the PACs?


Connected the same way as an external start, once the system is pressurised the systems downstream do not know how it is being supplied, external HP, APU, or engines. LP air is not used at the same time as the packs as it is possible to get back flow.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
User avatar
fr8mech
Posts: 7994
Joined: Mon Sep 26, 2005 9:00 am

Re: Packs and Supplementary Air Supplies

Tue Jul 31, 2018 1:44 am

The max pressure produced by those carts is about 50psi, in jet start. Hardly high pressure. Yes, higher than a conditioned air source, but not high pressure, by any definition of the word.

I just looked at the AMM (B757), and the max pressure allowed at the pneumatic ground connection is 45psi.
When seconds count...the police are minutes away.
Unless it's expressly prohibited, it's allowed.
You are not entitled to a public safe space.
Ego Bibere Capulus, Ut Aliis Sit Vivere
 
Max Q
Posts: 8171
Joined: Wed May 09, 2001 12:40 pm

Re: Packs and Supplementary Air Supplies

Tue Jul 31, 2018 4:07 pm

We used to have a centralized built in high pressure air system at every gate in one of our hubs


We ran the packs off it and could use it for an external start if the APU was inop


If most gates were occupied and all aircraft were using the system pressure would drop off and so would the effectiveness of the packs



Several airlines had this built in system including AA at DFW, don’t know if theirs still exists, ours was removed
The best contribution to safety is a competent Pilot.


GGg

Who is online

Users browsing this forum: A340TLS and 10 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos