The engine starting sequence was also in airline operation 3-4-2-1. At the gate the altered sequence was 3-2 prior the pushback and 4-1 after due to safety reasons for ground crew and for noise restrictions at some airport stands.
Brit312 explained in post #140:
Yes we always started just the two inboard engines prior to push back and the outers when the push back was complete. This was for a number of reasons, but I do seem to remember it was not unheard of to break the tow bar shear pin on the initial push, so the less power the better
Remember that Concorde had no APU and no across the ship ducting for stating engines, therefore prior to push an air start unit was plugged into each pair of engines and the inboard engines would be started. This allowed, after push back, air from each inboard engine to be used to start it's outboard engine.
The other good reason for starting the inboards prior to push was that with no APU the cabin temp would rise quite quickly [specially in places like Bahrain in summer] and never mind the passengers
comfort, but some of M2dude and ChristiaanJ fancy electronic equipment was very temp sensitive , especially those intake control units down the rear galley. With Two engines running we could use their bleed air to at least try and hold the cabin air temp during the push back
I must admit that I am no expert (not yet
), but it seems both sequences follow the logic to feed the blue hydraulic by engine#3 first, then one of the two yellow systems (2 or 4) and the green hydraulic (engines 1&2) which supplies power to some more services than the blue (droop nose and visor, landing gear, main wheel brakes with anti-skid and nosewheel steering).
Well, I hope, this was not a stupid answer before I took a chance for a nonstupid question
- but I am so exited about this thread and just want a little bit to give back!
Thanks for the probably best thing ever I have found in the internet. Thank you M2dude, Brit312, ChristiaanJ, Exwok, Bellerophon, Landlady et al.!