Thanks for all replies! made it clear
And thanks Yeelep for the points and thanks Amp lol yeah no hands on for experiments! but I did try this on simulator! Thanks Safe for the equation!
Yeah now it seems like the monitoring of the RPM of the APU is not a requirement. So now it triggers that in a APU overspeed (lets say during startup) if the APU has to be shutdown, you only rely on the EGT gauge (?) Those classics and originals how do you know your APU has overspeeded? again monitoring EGT? (in fact they have a red marking!)
I think my question now points to manufacture in fact this is now confirmed a product feature than anything else. I dont know about other Boeings but 757 do have APU RPM monitoring during startups (and continuous)
I am sure 737 MAX will have the APU RPM monitoring if not that
at least Southwest can demand that
Code0