autofeather question
It has been 10 years since I went from turbo prop to jet, and I cannot remember the details. Also I flew the F50 and DHC8 and not the ATR. My questions:
What does the autofeather do? (I know the basis function but what else):
-what triggers autofeather?
- does it reduce fuel flow to the "failed" engine?
- is the "objective TQ" increase a power up trim on the "working engine" or just a adjusted position of the torq bug requiring manual power increase on the working engine?
It looks like at 02:52:35 pretty much simultaneously :
- MW ENG 2 (flame out warning)
- start of increase in Beta ENG2 (feather in progress)
-ENG1 Bleed valve close (more power available on working engine)
- drop in all engine parameters for ENG 2 (FF, NH, NL, ITT) without PLA ENG2 movement (so that is a big one, will an autofeather of a working engine lead to over torque or reduce fuel flow?)
Looks like an autofeather but before the torque started dropping of. (is torque the only trigger for autofeather?)
From there on it looks like the pilot started reducing power on ENG 1 (02:52:43-02:53:15), tried to increase power on ENG 2 (PLA2 increase 02:53:15), and ENG 1 shut off at 02:53:20.
My cent (two cents corrected for inflation since it has been 10 years of the props)
I don't think any of the indications were crossed, it would have been apparent during start.
To me it looks like while they were looking at the problem they kept reducing power on the working engine, all engine indications on ENG 2 are consistent with the PLA change and subsequent shutdown.
Because I don't know if the autofeather reduces fuel flow after it senses failure and tries to feather I don't know if ENG 2 failed with a working autofeather or if the autofeather system feathered a working ENG 2 BUT:
The pilots should know how/what the autofeather does.
I was always trained to use power reduction as a confirmation for the failed engine, if you get a stall warning after you reduce power the power should have been pushed up (followed by a sheepish chuckle and "darn, I guess it was the other one").
It doesn't really matter what was wrong with ENG 2, it seems clear the pilots shut down a working engine for no apparent reason. I would love a well translated CVR readout, seems appropriate considering the leaked/released FDR data (and required testing of the remaining pilots) pretty much hangs them already.
Last edited by hans brinker; 27th Feb 2015 at 00:16.