A320 engine start

[sabenaboy]

Aah, it's about a V2500 engine...

I found the passage in the FCOM for V2500 equipped engines. It says that the FADEC runs an abort sequence if a start aborts on the ground when N2 < 50 %. That doesn't mean that the FADEC doesn't monitor the eng start any more.

For the CFM56 engine the FCOM says that the Fadec will abort the start in case of start problems without mentioning a 50 % N2 or other N2 limit.

So apparently this is strictly a V2500 thing. I guess that if a problem occurs after 50 % N2, it will not be considered as a start problem any more and that you will get an ecam message, but no automatic abort. I suppose however that it's unlikely for a start problem not to be detected before N2 reaches 50 %.

Last year a crew in my outfit reported an eng failure just after the start. (don't remember if it was on a CFM56 or V2500) Investigation revealed that it wasn't actually a real eng failure, but rather a (late) eng start problem. After that we received a reminder not to start the second engine before it was fully stabilized (grey background on N2 indication disappears) (ref FCOM 3.03.08 P2)

I don't think there's a technical reason why you couldn't start the second engine right after the first start valve closed but it's simply believed to be a good operating practice to wait for the first start to be fully completed as per sop. (It's annoying because it appears to take ages before that grey background disappears when starting an old V2500)

Should anybody know a technical reason why one shouldn't start the second engine right after the first start valve closure, I'd be very interested to hear about it.

Smooth flights,
Sabenaboy