sieggie wrote on Jan 27^th, 2012 at 9:41pm:

Thanks for the info. I was in fact using engine 3 with out ground power/air. It is strange that CS did not provide an APU on the bird. At least one 707 manual I have found shows APU controls on the FE console. Dave

That question of adding an APU to the 707 has been thrown around the forum several times. If you do a search on it in the 707 forum, you will find out why there isn't an APU. I pretty sure it is because many of the original 707's didn't have them installed. Here is a quote regarding the APU on the 707:

dmb201 wrote on Jun 18^th, 2011 at 3:58am:

the reason there is no apu on the 707 is that they weren't in commercial use yet military yes but civilian no because they were to big at the time.

Mark