Performance Class A requirement is
that an a/c is able to sustain an engine failure and continue to be operated
safely. So we always consider the engine out and all engines case for our
calculations of TORR, TODR and ASDR.
A balanced field is where TODA = ASDA. This then is the field length.
If I suffer an engine failure at V1 and GO then I will just make the screen
height of 35ft and V2 within TODA.
If I decide to STOP then I will just stop within ASDA. This then must be the minimum required field length.