Hi all,
The Classic B747 will fly quite controllibly with all four engines windmilling, with all four hydraulic systems functioning, albeit at a lower output.
The book specifies a minimum IAS of 160 to maintain all this, but a slightly higher speed would be nice to try the re-starts!
It also mentions that gear and flaps should not be operated!
The re-starts would be powered by the battery, and the Captn. would lose his heading info during this time, on essential, although, on RR powered aircraft, heading info is not lost!
The B747 is a very well designed aircraft, proven day after day with it's reliability!
I believe the 'u/c indicating' (bottom LHS of the P12 panel), when that relay is de-energised, it will allow the APU to be started inflight - it will also stop the spoilers coming up automattically when landing, without the 'autospoilers' ennunciator light to warn you.
Cheers