Boeing was looking at what was called a "thrusting APU" as an alternative to development of a new 115k thrust class engine
Perhaps a 747 classic pilot can confirm my memory:
The baseline TO performance in the Boeing AFM is "APU ON", meaning that the few Newtons worth of APU thrust is tallied in with the four real engines for TO and climb. And if APU is inop, a small TOGW penalty is taken.
Or - am I losing it?
