Originally Posted by
MarkerInbound
The autofeather system is armed by raising the guard and then the switch under it found at the center of the pedestal aft of the prop controls. There is one green light to the left of the switch that indicates the system is armed. When the throttles are advanced to a point that equates to ~45 inches MAP and the BMEP drops below ~70 for more than one second a solenoid pulls the feather button in and the prop feathers as if the feather button was pushed. The system also then disarms to prevent autofeathering the other prop.
Thanks to you and others for the added detail on the operation of the R2800 auto-feathering system, which sounds comparable with that fitted to the Rolls Royce Dart turboprop engine some years later.
This preliminary report does not discuss the background to the captain's statement that the "auto-feather light was not illuminating" [1.1.12]. That begs a few questions, some or all of which may be answered by the Go-Pro recording.
Was this light failure revealed during some kind of pre-take-off test of the auto-feathering system?
Was the light failure simply due to a defective bulb, which presumably could have been quickly changed by the LAME, or did it imply a fault in the system?
Was any pre-take-off check made of the manual feathering system on the #1 (L/H) engine?
Mach E Avelli rightly points out that, on jets, the first action on receipt of any fire warning is normally to retard the throttle to idle, which action may in itself put the fire out. In this case, that action would immediately inhibit auto-feathering, as well as creating a lot of drag from a propellor in full-fine pitch.These were jet pilots but, fortunately, the Go-Pro recording should settle that argument.