Nigegilb,
I agree with Mr P the air in this pipe fulfills a number of functions. Would CLA confirm that Nimrod is no longer operated on 2 engines because there is not enough air to start another engine if one of them fails?
Due to the Limitation Log entry of keeping that pipe closed, after all engines are ground started, we cannot air start the engines at the moment. We can windmill start them. An engine can get air from the adjacent engine for an air start but, frustratingly, the electrics that control the air start also opens up the crossfeed pipe. So, we do not shut down any engine in flight unless in an emergency, such that when an engine that is shut down will not be considered to be safe to relight it.
Before you ask, yes, we are looking at ways we could air start an engine in the event of a failure to windmill relight following a precautionary shut down.
And, yes, that pipe has had this limitation in place since 3 Sep 06.
Regards
Ed Set