APU bleed use after APU Auto Shutdown (A320

[narapusnapus]

Happened in the sim to me-Started Eng 1 and during Eng 2 start we had a APU auto shutdown. We followed the Ecam and switched off the APU master accordingly.The APU bleed switch was however,still on.I suggested to my training partner to switch off the APU bleed and attempt a crossbreed engine start.The instructor then paused the sim and told us we don’t need to do anything because since the APU bleed switch is on the Crossbleed would automatically be open so engine 2 would be pneumatically supplied by eng 1 bleed.He said we didn’t have to do a crossbreed engine start supplementary procedure.Can anyone explain this a little better please?

[Tail-take-off]

I don’t think your instructor is right. The APU bleed valve closes when the APU is below 95% even if the bleed pb is on. With the crossbleed valve in Auto it closes when the APU valve closes (valve position not PB position).

More importantly though… Why would your instructor be teaching you to ignore the published crossbleed start procedure in favour of making up your own?

[sonicbum]

Originally Posted by narapusnapus

Happened in the sim to me-Started Eng 1 and during Eng 2 start we had a APU auto shutdown. We followed the Ecam and switched off the APU master accordingly.The APU bleed switch was however,still on.I suggested to my training partner to switch off the APU bleed and attempt a crossbreed engine start.The instructor then paused the sim and told us we don’t need to do anything because since the APU bleed switch is on the Crossbleed would automatically be open so engine 2 would be pneumatically supplied by eng 1 bleed.He said we didn’t have to do a crossbreed engine start supplementary procedure.Can anyone explain this a little better please?

Let’s skip the technical for a moment. The main issue I see here is that the bloke you had in the sim should rather be doing something else instead of conducting type rating sessions, and this is regardless of the fact that this person is wrong in what has been taught to you, but primarily because you stated “can anyone explain this a little better” and this means the instructor failed its purpose to instruct, be it even wrong stuff.

The instructor should have highlighted at what moment did the APU fail, i.e. during the engine start with or without fuel fuel flow, hence the need to run a dry crank? How to behave from a maintenance point of view, from an MEL point of view and from an operational point of view with associated supplementary procedures.
Consider that during engine start you are still considered under dispatch phase, i.e. you have not started to move under your own power for the purpose of taking off, hence failures that cannot be reset must be recorded in the techlog and maintenance needs to be involved, i.e. back to the gate. Should You have a PART-145 limited crew authorisation (that’s EASA I don’t know how that works in India) you can dispatch yourself provided no maintenance action is required as it is the case of the APU AUTO SHUTDOWN.

I am 100% sure the purpose of the SIM script exercise was to discuss the implications of this failure in terms of TEM and conduct a crossbleed engine start. I believe none of which happened.

[boeing747430]

I vaguely remember, that on ground the the APU bleed switch in on and on ground does indeed open the crossbleed valve. It’s been a while, though.

Still, since you will have to set brakes first in order to be able to then increase power to have enough duct pressure for an engine-friendly start, it seems sensible to at least consider entering the supplementary procedure. This being mandatory or not may be a company issue.

Also, APU auto-shutdown does trigger an ECAM caution, or not!? Surely one has to take care of this first!?