APU electrical and pneumatic outputs
The APU can provide electrical power and pneumatic air. These are related to the same machine, but their availability and distribution should be checked separately.
APU start conditions
Follow the FSS power-up flow and confirm that the aircraft has the electrical power and fuel state needed for the simulated start.
Start the APU
After EICAS is energised, wait 30 seconds. Move the APU selector to ON, then momentarily to START. Watch the aircraft indications.
APU indications
Monitor APU speed and any CAS messages. FSS says electrical and pneumatic power become available three seconds after the APU reaches 95% RPM.
Check electrical supply
On ELEC, verify whether the APU generator is available and selected and whether the intended buses are powered.
Check pneumatic supply
On ECS, compare the APU bleed selection, valve indications and manifold pressure. A running APU does not by itself prove a particular pack is receiving air.
APU shutdown
If the aircraft still needs APU bleed air, establish another source before selecting OFF. If it still needs APU electrical power, confirm a replacement source is ready. OFF removes pneumatic power immediately; electrical power remains through the one-minute cooldown. Before switching the batteries off, wait for APU OFF and APU FUEL SOV CLSD on EICAS.
Use the normal selector for a normal shutdown. FSS says moving it back to ON during shutdown cancels the shutdown sequence. The emergency-stop button is for an emergency condition, not routine shutdown. The documentation does not confirm immediate-shutdown simulation in every build.
The APU fuel source changes with the electrical and engine state. FSS describes the DC fuel pump with DC power only, AC fuel pump 2 with AC power available and engines off, and the right ejector pump with the right engine running. FSS also notes that fuel can be supplied from either wing tank through crossfeed. Check the relevant fuel indications and valve configuration for the current setup. [99] [10] [94]