NSEU
Not current on these types, but Autostart has varied little ...
Does this mean it keeps starting and stopping the engine for 5 minutes?
The starter motor is run continuously up to its duty limit timer (5 minutes).
The initially selected ignition plug is operated until fault condition is detected, turned off for thirty seconds, then selected (along with the alternate plug) until ...
The HP fuel shut-off-valve is opened until fault condition is detected, then closed for thirty seconds, then opened until ...
Is it up to the pilots to stop the autostart after seeing the messages, or will the Supplemental Control Unit abort the start on the second failed start?
The control system completes its autostart procedure with the starter motor not running, ignition plugs not operating and HP fuel shut-off valve closed.
The flight crew must deselect the switches that initiated the autostart procedure. The reselection of auotostart procedure by the control switches will then be available. It may be desireable, before trying further engine operation, to allow the starter motor to cool and/or effect some repairs!
Also, I understand it's not standard practice, but it's also not clear what happens if BOTH ignitors are selected for the first start. Does the system not bother a restart (because it already knows dual ignitors won't work).
I don't know for the PW engine, but I think it's desireable to use one logic (i.e. having two start attempts), because it gives the engine two chances including with the much extended motoring, and it means most (starter and fuel) system control logic only needs one design and test; the ignition plug control and fault reporting may vary by design.