Autofeather vs NTS

[GravityHater]

OK, read and tried to digest all that, thanks.

Next a question about operating an twin turboprop with AF in the event of an engine failure. Completely hypothetical.

Would you expect most flight manuals to say when one quits, do NOT pull a power lever to idle (ie the dying engine) as this will inactivate the AF system?

 

[pilotyip]

When it autofeathers, you don'ta toucha nothin. Unless of course it is on fire then follow fire procedures

 

[Donsa320]

OK, read and tried to digest all that, thanks.

Next a question about operating an twin turboprop with AF in the event of an engine failure. Completely hypothetical.

Would you expect most flight manuals to say when one quits, do NOT pull a power lever to idle (ie the dying engine) as this will inactivate the AF system?

I can only speak for the Allison engine installation and there, once the feather button has been sucked in by the autofeather system, it would make no difference what you did. The fuel has already been shut off and the feather solenoid actuated and electric pump is already running. In my experience, turbine engines usually don't gradually die. They either run or they don't. The exception could be bird ingestion, hence the need to turn off autofeather if you see birds about to collide on take off. My failures were instantaneous. Only had one on take-off at about 90 knots. I heard the bang, perceived the left prop feathering as the nosewheels started to howl and I stopped. Enroute with the autofeather not armed of course, bang and the safety coupling let go so that the prop and engine were no longer connected. The NTS never had a chance to operate and prop sync never even was broken. Manually feathered it and landed.

 

[avbug]

As others said, with autofeather, your first indication of a problem is quite possibly that the propeller has already feathered. Your function at that point is securing items after you address flying the airplane.

The failure I experienced late this summer was a case of the engine continuing to run, but the prop feathering, without an autofeather system available. All my oil ported overboard with a turbine bearing seal failure, and the prop moved toward feather (kept turning, however), while I had engine response. I could push the power up, see the EGT climb, but had no thrust through the prop as I'd lost propeller control. I didn't have much time to evaluate it, but in the back of my mind I was thinking about a possible shaft failure. The propeller didn't fully feather, the engine didn't quit turning, and while I had appropriate power response through the power lever, I had no torque. In that case, the trained response for that engine installation was to keep pushing up the power lever, as the lever controls both the fuel controller and the propeller; it offered the best chance for minimal prop drag in the event the propeller didn't automatically feather. Lots of conflicting signals and no altitude to sort it out. Temps went through the roof, but the engine was already toast, and my only concern was making my forced landing site.

With autofeather, once the system has done it's job, you follow up with the appropriate pilot actions per normal. However, in order for it to work, the power levers must be far enough advanced to activate the microswitches that arm the system.