Originally Posted by
Dash8Pilot
I believe a couple of accidents led to this. The first was a CRJ-200 in China which crashed after taking off with ice on the wings and over-rotated. The second was the Challenger crash with Dick Ebersol form NBC sports.
Doesn't change the fact that it's a stupid procedure.
This is not a ‘stupid’ procedure, but by your post shows you have little knowledge and or respect for the type of supercritical wing used on the jets some of us fly. That these jets suffer greatly from an increased coefficient of drag (and a much decreased coefficient of lift), if hoarfrost or other contamination is present for takeoff. CRJ models without slats have caused fatal icing takeoff accidents, as have also occurred in the Yak 40, Citation, Falcon, etc.
The main problem lies within in the flight director, which commands 15 degrees nose up (average) for most flap and temperature/pressure conditions.
These new procedures cover the dangerous scenario where a pilot boards his plane under a clear blue sky, not noticing that the overnight temperatures and a super-cold fuel load have coated his wings with a dangerously uniform and transparent coating of invisible frost. Time and again it's been proved that a light coating of contamination can be missed or disregarded as inconsequential.
This scenario is apparently what happened to a Challenger 604 crew at Birmingham UK and a CRJ200LR crew at Baotou China. The Challenger 850 crew in Moscow (Vnukovo Airport) on Feb. 13 and the CL604 at Montrose appear to have been victims of an excessive hold-over time and snow-showers.
We are talking about a deadly contamination stall upon takeoff. Why? Because the CRJ 100/200 can easily be rotated into a wing-stalled condition (before the stall protection system can react) where wing drop (aka "roll-off") is highly likely and any attempt to "pick up" a stalled wing with aileron just compounds that wing drop.
That is what happened in the Fokker 100 accident at Skopje.
That stall occurred at an angle of attack between 10 degrees and 11 degrees and was preceded by heavy buffet just before the stall. The stall itself is characterized by a sharp roll-off, followed by severe wing rock. The crew of the (not de-iced) accident aircraft concentrated on controlling the wing rock, but at the same time kept pitching up towards the FD cue above the current pitch angle of 10-12 degrees. Each time they pitched up towards the FD, the aircraft stalled again.
So, remove the flight director until they fix the thing – you don’t need it to fly anyway. Initially pitch to 10, pause, then pitch to maintain proper airspeed and angle of attack during further pitch toward 15/18 degrees.
Last edited by sandlapper223; 09-18-2008 at 10:09 PM.