A320 LP and HP Ground connectors

[arrow28]

Hi
Could somebody explain a few queries that I have. Having looked at the Pneumatic Schematic and reading the description. I am puzzled that on the schematic it only shows the external HP inlet.
1. So if the LP ground connector is attached to the a/c what indicators do you have that it is connected and providing conditioned air to the aircraft. I assume this is done to cater for a u/s APU or where the APU due to a malfunction cannot provide the air.
2. The description mentions that the HP ground connector can also be used for air conditioning. I thought it was only meant for engine starts. There is no HP connection shown on the schematics, where as the LP connector shows LP air piped in to the mixing manifold. What is the path of the HP air from the time it leaves the external source to the cabin and flight deck?

Thanks

[TURIN]

From memory, you have no indications that the LP air is connected which is why the packs are selected off when its connected and should only be selected on when clearance has been given.

The Ext HP air can be used to drive the air con packs just like any other HP air source such as engine or APU but the ground cart needs to be certified to be capable of providing clean air.

I think.

Hope this helps.

[Metro man]

I was told that if you used external HP air for the packs, the cart would overheat so possibly the supply has to certified as powerful enough as well as clean.

Normally we use a seperate ground air conditioner which pumps cold air straight into the duct.

[CaptainMongo]

Metro Man - correct. The carts at our company have both a low and hi setting. We can use the low setting for a short period of time to run the packs, basically the (hopefully very) short time between conditioned air disconnect and engine start. It is encumbant on pilots not using APU air to operate the packs and external conditioned air at the same time.

The following is an incident report of a non return valve failure. While the report doesn't indicate the failure was because of simultaneous use of APU bleed air to operate the packs and external conditioned, I could imagine after repeated non compliance, the NRV could fail.


https://assets.digital.cabinet-office.gov.uk/media/5422efe440f0b61342000275/dft_avsafety_pdf_501105.pdf

[Escape Path]

So far as I can tell, there's no indication of LP ground connection to the aircraft. Normally we coordinate with the ground crew via interphone so as to not have both APU bleed and LP air providing the packs simultaneously.

Indication of the air cart actually providing conditioned air can be seen on the COND sd page. The zone duct temperature indication shows an according value (i.e. not 30 degrees or something like that but an actually comfortable temperature)

[CaptainMongo]

Escape Path

- true that wrt to zone duct temps. No cockpit indications of external air connected. I also look out the left window and see if the hose is inflated, if it's deflated I feel as if I am at home.....

That said, if the galley wants H2o pressure (no potable water electric pumps on our AC) we fire up the APU, pack off, APU bleed on for 90 seconds and make that €135 cup of coffee!

[sierra_mike]

switch the CAB FANS to OFF and wait for a few seconds. if there is still air coming out of the air vents the external air is connected+working (PACKs of course OFF).

[fruitloop]

"Not" a good Idea to use external HP conection to drive A/C (packs) system...!!

[CaptainMongo]

"Not" a good Idea to use external HP conection to drive A/C (packs) system...!!

There is no restriction using external HP air to drive the packs.

[dream747]

Agreed, FCOM states that HP air can be used to supply air for the packs provided it is free from oil contamination.

[fruitloop]

Ok But please explain to me what shuts the external bleed off if a over-pressure or fire starts ?? When I did the school "35" years ago the instructor warned us about using the HP port for that purpose...I guess over the years that the value of life has diminished so go ahead and use it...BTW does the IGGS system work when external HP air is being supplied on the ground ..?? Have a great day..

[CaptainMongo]

The ground crew shut off the external air when I tell them to shut off the external air. Our SOP requires ground personal to be on intercom when HP air is being supplied to the AC. So you did a school 35 years ago - great. A lot of things can change in 35 years, but the value of life isn't one of them.

Finally no, the FTIS does not work with external HP air being supplied on the ground. Then again it doesn't work with internal air being supplied on the ground - in fact it doesn't work on the ground at all, it only operates in flight, but thanks for asking.

You have a great day as well.

[aurel90]

Hi guys I know it's an old post but as summer is going on, I still wondering what shall I do in case of a hot day with no APU nor ACU.

Agreed, FCOM states that HP air can be used to supply air for the packs provided it is free from oil cntamination.

I remember this reference but it seems it has disappeared from FCOM a while ago, the only thing I can find now is "An external HP source may be used for air conditioning." FCOM A/C system 36-10-10.

Nevertheless it makes sense to ask if the HP external is free from contamination and certified for it, but how can you check that in real life, you just ask ground staff and believe them ?

Where I work nobody is using HP source for air conditioning purpose, could be a cultural thing as according FCOM nothing prevent you to do it.

I would be glad to here your argument and experience returns in order for me to make up my mind. Thanks a lot.

[gearlever]

There should be a sticker on the HP AIR cart which says it may be used for AC.

BTW I have also never seen one neither in Europe nor the US.....

MAK twin mode unit (https://www.makcontrols.com/index.php/makcon_products/air-starter-unit-asu/)