Air Starter Unit to supply air conditioning packs on ground

[senseimatty]

Hello,
Is it possible to use an Air Starter Unit to supply the packs? Or does it connect to a specific port on the engines and it is not linked to the aircraft pneumatic system?
To be more specific: I've seen an air starter unit that provides 42 PSI which is the same pressure that is supplied from the APU to the packs on the B737. I would like to know if I can use the starter unit to operate the packs on ground for extended time, so that I don't need to start the APU instead.
Thanks

[Acie]

Hi.
Yes, you can use ASU for packs operation. It doesn't need to supply exactly 42 psi, it may be less. I believe that 25-30 psi is more than enough for packs operation.

[senseimatty]

Thank you!

[Tom Sawyer]

Hi.
Yes, you can use ASU for packs operation. It doesn't need to supply exactly 42 psi, it may be less. I believe that 25-30 psi is more than enough for packs operation.

I'm not sure it is as straight forward as that. The ASUs we use for supplying the packs have a separate selection for air con or engine start. I'm guessing the compressor must have to be rated or controlled to supply a slightly lower pressure over a longer period of time compared to engine start pressure for a minute or two?

[Uplinker]

Would an ASU have the same oil contamination standards as a set designed specifically for air conditioning?

[Acie]

I'm not sure it is as straight forward as that. The ASUs we use for supplying the packs have a separate selection for air con or engine start. I'm guessing the compressor must have to be rated or controlled to supply a slightly lower pressure over a longer period of time compared to engine start pressure for a minute or two?

Apparently it depends on ASU type. The one we use is with adjustable output pressure and it just maintains it either during engine start or packs operation. For sure if it is start tank, it doesn't suit for packs as they can be operated only for very limited time.