Much appreciated... Thanks.
I'm also hoping someone has some knowledge about the Pratt & Whitney Autostart system on the 747-400. Perhaps the pilot's FCOMs (or PPRuNe resident experts) can provide some answers.
The Boeing AMM says this about the 747-400 PW4000 Autostart system...
On the ground...
"Starting Anomaly: No Light(up) | Symptom Seen By Autostart Controller: EGT increase less than 28*C after 20 seconds | Autostart Controller Response: Motors the engine for 30 seconds, then starts fuel supply and ignition (using both ignitors). If N2 > 50% (starter cutout speed), the controller stops the start procedure."
It's not clear what happens if the second attempt fails (below 50%N2).
Underneath, it says .. If Starter Duty Cycle Time Exceeds 5 minutes, the starter valve is closed and the controller stops the start procedure.
Does this mean it keeps starting and stopping the engine for 5 minutes?
In flight, the manuals do say the Autostart system will continue indefinitely (no 5 minute limit).
I understand that the AUTOSTART Caution and the AUTOSTART, ignitor 1 and 2 Status messages appear after the second attempt. 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?
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).