This data I have copied from flightaware:
Time speed altitude vs
18:28 147 22.500 600
18:29 147 23.100 600
18:30 147 23.700 540
18:31 147 24.200 480
18:32 147 24.700 480
18:33 147 25.200 600
18:34 68 26.000 360
18:35 60 26.000
18:36 255 26.000
18:37 255 26.000
18:38 255 26.000 -720
I am flying the PC12 since 7 Years now. Both, the old 45 , 47 and also the NG.
I very much doubt the flightaware data.
From 18:28 till 1833 the aircraft is keeping an airspeed of 147 kt.
During this time the aircraft climbed from 22500 ft till 25200 ft.
I have never had a flight where the groundspeed was exactly the same for 5 Minutes during a climb. Given that the autopilot was running, holding the airspeed constant, the true airspeed would have increased and the wind would have changed.
18:34 the airplane reached 26000 ft. The airspeed is so low, that the airplane would have stalled. 60 kt true airspeed equals 39 knots indicated airspeed.
If it stalled, it definetely wouldnīt hold the altitude constant during the stall.
At 18:36 for 3 Minutes it has a normal cruise speed of 255 kt again.
The PC12 canīt hold the altitude and accelerate from 60 to 255 knots in one minute.
The Stallspeed oft he PC12/47 clean, max take off weight is 95 kias.
The Stick pusher activates at VSx1.1. So it would kick in at 104,5 kias.
At 26000 ft that would eqal 158 kt true airspeed.
To keep the airplane unstalled with the 60 knots groundspeed flightaware is showing, we need some 98 knots of headwind. Just one minute before that the airplane is climbing with 147 kt of groundspeed.
Add the 98 knots of headwind and the airplane would have climbed with a true airspeed of 245 knots. At this high airspeed the PC12 isnīt climbing in 26000 ft.
This is another Point, that the data in flightaware isnt correct.
It is possible to recover from the stick shaker without altitude loss if you know what will happen and if you are very good trained.
It is impossible to do the same during pusher activation.
During Training at Pilatus for the NG, I had some thousand hours on the 45 already.
The best recovery from pusher was with 500 or 600 ft Altitude loss.
And I was expecting it, had just completed a type rating with EX military instructors and it was in VCM daytime.
I never recovered from that at 26000.
For the last 5 minutes the airplane holds 26000 ft. Any stall or pusher and the aircraft wouldnīt have stayed at 26000.
What ever happened, the flightaware data isnīt showing it.
So I am with Sydy, lets wait for the NTSB
Last edited by inbalance; 9th June 2012 at 21:38.