A320 APU

[B737NG_Pilot]

Why this change in N% (Honeywell 131-9)

The ECB always sets the APU speed to 100 % except for air conditioning demand, if the ambient temperature is between -18 °C and 35 °C. In this case, the ECB sets the APU speed to 99 %. For all other ambient temperatures (less than -18 °C or more than 35 °C), the ECB sets the APU speed to 100 %.


On the APS3200



In the case of an automatic, non-emergency shutdown, the air inlet flap closes 15 min after the APU speed is lower than 7%. If an automatic, non-emergency shutdown happens on ground, the 15 min countdown starts after liftoff.

Why the delay ?

[Ultranomad]

I have no experience with A320, but just from the general principles, flap closure may be delayed to let the APU turbine cool down properly.

[Acie]

737NG Pilot, never seen that delay on ground on A320. There is max 2 min cooldown cycle before APU shuts down (depends on bleed usage). Inlet flap closes immediately after APU rpm is less that 7%. Where did you find information about 15 minutes delay and could you please insert a quote from a document here? Could you also tell what do you mean under automatic shutdown? There is no automatic shutdowns on APU - it is either normal, protective or emergency.

[aeo]

737NG Pilot, never seen that delay on ground on A320. There is max 2 min cooldown cycle before APU shuts down (depends on bleed usage). Inlet flap closes immediately after APU rpm is less that 7%. Where did you find information about 15 minutes delay and could you please insert a quote from a document here? Could you also tell what do you mean under automatic shutdown? There is no automatic shutdowns on APU - it is either normal, protective or emergency.

I think you’ll find Airbus classes all abnormal APU shutdowns as Auto with an ECAM message APU AUTO (EMER) SHUT DOWN… Good question about the 15 minutes though.

[swissairMD11]

Good question. Am wondering too now. Could it be that it suck the air out of the cowl flap? Hmmm