747-400 RB211 Autostart Windmilling Start
Folks...
Disregarding QRH procedures for windmilling autostarts .... Is there any airplane logic requirement for the Autostart system to see a transition of the Fuel Control/cutoff Switch (FCS) from OFF to RUN on this aircraft before Autostart begins?
My (engineering) training notes are ambiguous. In one section it just has the logic "FCS in run", but elsewhere, the text says "moving to RUN" (as if a transition is required).
Auto Ignition and Auto Relight are less ambiguous. The RB211 Auto Relight System senses abnormal engine deceleration and, until N2 rpms are below 35%, the Auto Relight logic will override the normal Auto Ignition logic (Auto Ignition logic is N3 <58%, HP fuel valve open).
I guess the only difference you would notice is if the auto ignition and autorelight failed to stop the engine flaming out and the Autostart had problems relighting the engine. The Autostart controls fuel flow: Unsuccessful autostarts see the fuel being cut off prior to successive autostart attempts... although the duration might be short, depending on engine temperature.
Experts?