?? B737NG APU Auto-shutdown ??

[HalinTexas]

Can someone answer:

The APU has an auto-shutdown feature for fire. Why does it not automatically fire the extinguishers?

[spannersatcx]

Apu's are either monitored or unmonitored, by the a/c systems, if it's unmonitored then the a/c should not be left unattended so in case of a fire YOU fire the bottle.

[NSEU]

Some aircraft APUs auto-extinguish on the ground, but not in the air. In the air, the pilots are monitoring the aircraft. On the ground, there may be no one in attendance.

Rgds
NSEU