Will the APU starter engage before the FLAP OPEN annunciation appears on the ECAM APU page?

Will the APU starter engage before the FLAP OPEN annunciation appears on the ECAM APU page?

• A. No
• B. Yes
• C. Sometimes
• D. Not specified

Answer: (A)

The starting sequence of the APU is governed by airflow availability. Before the APU can start spinning, its ram air inlet/door must open to supply ambient air for combustion and for the starter to function. On the ECAM APU page, the FLAP OPEN indication shows that this intake door is open, which is a prerequisite for starting. Only after this door is open does the APU starter engage to drive the compressor and bring the turbine up to speed with ignition. Therefore, the starter does not engage before the FLAP OPEN annunciation appears; the air intake must be open first. In normal operation, there is a defined order rather than variability, so options suggesting “sometimes” or “not specified” aren’t correct.

The starting sequence of the APU is governed by airflow availability. Before the APU can start spinning, its ram air inlet/door must open to supply ambient air for combustion and for the starter to function. On the ECAM APU page, the FLAP OPEN indication shows that this intake door is open, which is a prerequisite for starting. Only after this door is open does the APU starter engage to drive the compressor and bring the turbine up to speed with ignition.

Therefore, the starter does not engage before the FLAP OPEN annunciation appears; the air intake must be open first. In normal operation, there is a defined order rather than variability, so options suggesting “sometimes” or “not specified” aren’t correct.