Bleed air + ground air

[CW247]

Airbus states that APU bleed should not be on with ground air plugged in (in other words providing conditioned air at the same time) due to damage of certain valves? But when was the last time you arrived on stand to have ground ops plug in air and actually advise you that they've done so? (normally you get the buzzer or a knock for ground power). Been flying commercially 7 years and never seen this happen. The one doing the walk around normally discovers it and then advises the one in the cockpit to deselect APU bleed.

We can't make the assumption that if ext power is connected so will ground air be connected as that really depends on where you're going and what's working/ being provided on that day by handling. Does your airline have a policy for determining / being advised that ground air is plugged in?

[Swedish Steve]

Here in ARN running the APU on the ground except for engine start is not allowed, so we have no problem. If the crew leave the APU running after arriving on the gate they have only themselves to blame.
But, connecting up ground airconditioning and nothing happens. There is an NRV in the ground air connection that stops the ground air entering the aircraft until the packs are off. (the packs produce much more pressure). It is only if this NRV is broken open that there will be a problem, and the ground crew will hear that when they open the panel.
Don't worry about having both connected, it is very hard to damage the aircraft.
But.... do not connect air start air and APU bleed at the same time. This could damage the bleed system, if an NRV was stuck open.

[NSEU]

On the airline I used to work for, there was co-ordination between ground engineers and the cockpit in relation to both air and power. Although there is a check valve on the ground air inlet, we saw several failures of these after we started using ground air as standard practice. The operators of the ground air equipment also warned us that back pressure from the aircraft could damage their equipment.

I suggest that you forward your concerns to management so that they can can sent out memos to ground staff. However, the installation and removal of ground equipment can be fairly labour intensive. I imagine those airlines working on a limited budget may not be able to provide sufficient manpower to follow the correct procedures without incurring delays (the ground handlers usually have numerous other duties to perform)

[CaptainMongo]

We do not operate packs with APU bleed and external air to prevent damage to the non return valve. As an aside, below is an incident of a non return valve failure leading to a rapid depressurization:

https://assets.publishing.service.gov.uk/media/5422efe440f0b61342000275/dft_avsafety_pdf_501105.pdf

[ACMS]

Yes it's called coordination.......

Our mob seem to cope quite ok.

[vilas]

Also there is an issue of pack contamination with external air. That is why generally packs are switched off before connecting external air unless it is confirmed free of contamination.

[Cak]

Do you have any reference for turning off the packs in this case?

[Check Airman]

I've seen mtx run the packs from the HP air...

[Swedish Steve]

Also there is an issue of pack contamination with external air.
The original question was about external conditioned air, not HP air.
with external conditioned air, the packs are not involved.

[whitelabel]

The air from a ground airco unit goes directly to the mixing unit so packs are not involved and as there is no bleed air.

You can check if ground air is connected by observing duct temps on ecam. Although sometimes the units dont work well so you still dont know if the airco is on. Then switch off cabin fans and check if you feel any air from the "eye ball" if not then you know there is no air provided and you can stick on apu bleed. (Of course provided you switched apu bleed off before)

Not really sure why airbus could not create an indication on ecam.

[Check Airman]

Not really sure why airbus could not create an indication on ecam.

Presumably for the same reason they thought you'd want to transmit on a radio without listening to that frequency...:ugh:

It's a great airplane, but it does have its weird bits.