A fair question well asked.
First thing, inspection. The aircraft will have been signed off no doubt by one or more very able technicians, despite which you need to do your own inspection. This may cause offence, but probably not - it's your neck after all. Get hold of a similar checklist to that used for final sign-off to the senior technician on the rebuild and don't expect to spend less than half a day on it, for an aircraft of that complexity a full day is more realistic. Ask as many daft questions as you wish, and don't accept anything less than an apparently perfect aircraft.
Second thing, functionality - you want to have seen everything hydraulic or electrical operated (ideally on jacks to simulate flight loads) at least a couple of dozen times. This particularly applies to the gear. Have all the pressure instruments been on a test set in situe, has there been a leak check (often neglected)?
Third thing, weight and balance. For first flight you want it loaded as near mid as possible, in case somebody got their sums wrong. Also, I would decline to accept a weight and balance based upon the aircraft pre-rebuild, insist upon a new weighing.
Eventually you'll run out of reasons not to fly it (which should be the mentality pre-flight). The next thing depends upon site.
- If you have a nice long runway available, I'd recommend some fast taxis and low hops. The purpose of all this is to check basic stability and controllability - you want to have checked all of the controls during these hops except probably gear retraction.
- If you haven't, get airborne fast and flat (erring on the safe side, you don't absolutely know if the pitot works properly yet) then get yourself to a good safe height and check all of the controls for normal operation, including trim range, ability to hold wings level hands-off, etc.
- Having satisfied yourself that the beastie is basically safe, think about flying the formal test schedule. It is likely that the schedule will call for 2 sorties - one at LW-aft, the other at MTOW-fwd, in which case you may need to land after the first shakedown sortie and re-ballast.
- Take a handheld GPS as a get-out-of-gaol-card in case all the avionics go tits-up.
- Finally, if your local procedures permit it, take the senior technician from the rebuild in the right hand seat. He or she can then see any fault first hand and make notes they'll fully understand concerning what needs doing.
- Finally Finally, DO NOT AT ANY TIME HURRY ANYTHING.
All a bit general, but I hope that this helps.
Merry Christmas,
Genghis.