Originally Posted by
gums
And finally today's comment: @ driver. The first crew call I can see about AoA vane is about 4 minutes from WoW.
Gums sends...
From the preliminary accident report:
At 05:38:44, shortly after liftoff, the left and right recorded AOA values deviated. Left AOA decreased to 11.1° then increased to 35.7° while value of right AOA indicated 14.94°. Then after, the left AOA value reached 74.5° in 3⁄4 seconds while the right AOA reached a maximum value of 15.3°. At this time, the left stick shaker activated and remained active until near the end of the recording. Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording.
At 05:38:43 and about 50 ft radio altitude, the flight director roll mode changed to LNAV.
At 05:38:46 and about 200 ft radio altitude, the Master Caution parameter changed state. The First Officer called out Master Caution Anti-Ice on CVR. Four seconds later, the recorded Left AOA Heat parameter changed state.
<snip>
At 05:42:51, the First-Officer mentioned Master Caution Anti-Ice. The Master Caution is recorded on DFDR.
At 05:42:54, both pilots called out “left alpha vane”.
From the data provided, it appears that the Left Alpha Vane warning was triggered within 10 seconds after liftoff. The First Officer called out "Master Caution, Anti-Ice" as would have been procedure. Normally, that call should have been followed up with a verbalization of what particular malfunction triggered the Master Caution light. The crew did not actually get around to doing this until a little more than four minutes after the light first illuminated.
Further examination of the DFDR output indicates that the first Master Caution alert was reset. This is normal procedure to allow for additional alerts, but it also extinguished the "Anti-Ice" annunciator. It appears that the crew simply forgot to look for the actual malfunction annunciated on the overhead panel. For reasons, that are not entirely clear from the data, the Master Caution light came on again at around the 5:42:50 mark, re-illuminating the "Anti-Ice" annunciator. The Master Caution light was reset again. It is at this point, four minutes after the original alert, that the pilots looked up and confirmed the "L ALPHA VANE" annunciation.
737 Driver sends.....