Originally Posted by code0
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!)
High EGT is only indication of high load (or maybe FCU problems during start), not overspeed. On the classic, you have a very simple indication that the APU has overspeeded - the OVERSPEED light on the APU panel illumintaes and the APU shuts itself down automatically.
I don't see a point in having tons of parameters instantaneously available to the crew, since the APU is very simple and fully automatically controlled turbine engine. It can detect and shut down for many types of failures (low oil pressure, overspeed, high oil temperature, fire, ...) and it can also prevent excessive EGT by modulating or fully closing bleed valve.
We could have same set of indications for an APU that we have for an engine, but then we could have some more indications for some other systems, panel space would be a problem and we could reintroduce flight engineer - just to monitor something automatics have been doing quite OK for the last 30 years.
By the way, does APU RPM monitoring on more "sophisticated" types than 737 works when doing battery electrical power-up (e.g. no ground power)?