A330/340 Question??

[lucky7]

Hi all
One question...is it recommended to use ground start air unit to supply bleed air for running the air cond packs should say the apu be inop on the ground? The Grd air unit is NOT turbine type and says it has a selection for MES(main eng start) and also ECS(environmental control system). Reasons please....Thank you:D

[SeldomFixit]

The only reason is one of wear and tear on the ground unit. The packs are perfectly happy to run using the GTSU in ECS mode. One pack run in such a manner is actually more efficient in cooling the cabin than a refrigerated air truck used over the same period of time.
The only related area of concern is that you must never supply pneumatics from ground and APU sources at the same time, unless you want to go AOG for the resulting duct damage. :{

[virginpaul]

Running conditioning packs from non turbine type HP ground carts (ie deisel units) is not recommended (at my airline).
The reason is one of potential/possible oil vapour contamination of the pheumatic ducting - the air supplied must be "clean". If oil/vapours do enter via a ground start unit used to power the packs, then they will quickly pass these vapours/odurs/smoke to the cabin, contaminating the LP side.
Using these units to start engines should always be accompanied with ensuring the packs are off to prevent this air from passing through the ACM units.

Turbine (APU type) ground air units are much more reliable deliverers of "clean" HP air - we don;t use these to run packs either for 2 reasons.
1/ They are expensive to use - as we use 3rd party units
2/ They have limited run times due to their fuel usage.

Ground conditioning carts (which deliver cold air) plug into the LP side (usually into the mixer) but are not that effective on widebody aircraft.

[QFBUSBOY]

I would back up everything that ViginPaul says.

I have heard what he has said before as the truth.:D:ok: