To my knowledge, yes it would be unusual.

Apart from anything else, your typical start cart is not intended for that use and the air it supplies may not be the cleanest as a result.

21 minutes ago, killairbus said:

Hey I just thought of using the air starter for running the packs, is that unusual with a functioning APU?

Very unusual, yes.

Start carts aren't very numerous, and are used specifically for aircraft with inop APUs. Outside of that, they're sitting at the ready to handle that situation, and sitting needlessly running the packs of an aircraft with an operable APU.

19 minutes ago, scandinavian13 said:

Very unusual, yes.

Start carts aren't very numerous, and are used specifically for aircraft with inop APUs. Outside of that, they're sitting at the ready to handle that situation, and sitting needlessly running the packs of an aircraft with an operable APU.

Indeed! In fact many ground air start units are basically nothing more than a large tank of compressed air on wheels. They have sufficient capacity to do one, or maybe two engine start cycles, but then their tank has to be recharged with a compressor. Not suitable for running packs.

In my days in the Air Force, we had a ground power cart called the "Dash 60" that could do the job. (I'll bet Dan is familiar with these).

That unit was essentially a portable APU. It was normally used to supply 3 phase 115 volt AC (and/or 28 volt D.C.) power for aircraft, but also has a flexible hose that could supply continuous bleed air to any aircraft with the connection to receive it. The Dash 60 was typically used to start fighter jet engines on the ramp, as those aircraft had no onboard way to generate bleed air on the ground without the engines running.

 

10 hours ago, killairbus said:

Hey I just thought of using the air starter for running the packs, is that unusual with a functioning APU?

 

-Angelo Busato

Very unusual, those air start ground units are loud and expensive.  You will not normally even see one close by.