External Air cart use

Question 1

Should be be ON when using airplane air conditioning unit?

Answer 1

yes, protective circuits are DC. Ensures protection in event of loss of AC power.

Question 2

What is external air cart cant hold 20PSI and APU is operating?

Answer 2

Isolation valve AUTO, APU BLEED air switch ON…then the left pack use APU air and right pack used external air source air.