Point taken guys, but at lower altitudes where you need to know the climb gradient info, doesn't tas almost equal ias almonst equal gs.
I mean, in my examples above, 3.3 % required at 120 kts, requires 396 fpm. The books quote 401 fpm. I aint ever flown an aircraft with gauges that accurate, nor am I able to fly an aircraft that accurately with one donk out in IMC and me shitting my pants all at the same time.
Chill out guys, it was only a helpful 'ball park' figure, because I know some guys would blast off in the smuck with no idea of required performance requirements and just pray like hell that they don't need to know or find out !!
This is just a convenient way to have SOME IDEA of what we should be hoping to get in the event of a EFATO.