Logic within most aircraft systems take 50% N2/N3 as the figure for the engine having been started. High heat on probes etc.
Airbus has sufficient engine oil pressure at this speed as a lot of systems require this info to enter the next phase, simulating engines running on ground requires LOP CBs to be pulled.
On v2500s The auto starting phase is controlled by the Engine Interface units EIUs commanding the EEC, the EEC monitors and protects. With the Starter cutting out at 50% the EIU passes to the EEC and the FADEC system to assume control of the stabilisation phase and operating ranges. Hence if an EIU is U/s you have no auto start capability.
Would never attempt a double engine start on the bus; you are asking for a hot/hung start, doubt the APU would have enough puff anyway.
Last edited by Beeline; 6th Jun 2011 at 15:19.