The Airbus document, entitled "APU bleed air oil contamination", states that "oil smell or smoke in the cabin resulting from APU oil contamination can occur at almost any time and not necessarily ...

while starter-assisted relights restart one engine at a time – two on the A380 – due to auxiliary power unit (APU) bleed air limitations and can only be performed below FL200. An engine ...

This is because nearly every plane uses roughly all the bleed air supplied by an operating APU to get the high-pressure turbine in the engine's core to start rotating for the initial part of the ...