Originally Posted by M. Mouse
We will never know
We can be never absolutely sure but if I may suggest somewhat radical approach towards the best possible understanding: reading the official report. As one PPRuNer mentioned:
Originally Posted by
AirRabbit
Please understand that my motive in saying what I’m saying (and what I’ve said previously), is in no way intending to impugn the fine reputation or the integrity of the NTSB or of the dedicated and professional employees at the Safety Board.
There you have it! It not just their integrity, dedication and professionalism that counts, it is their expertize laid open in their reports for all world to see and discuss.
Originally Posted by M. Mouse
calm and persistent statements do make me inclined to believe that what he says may well be the reality of what caused the accident that fateful day.
You should read the report. It's icy cold and consistent. I tend to rank consistency above persistence but it could be just me. It won't hurt to repeat the quote:
Originally Posted by The National Safety Transportation Board
The National Transportation Safety Board determines that the probable cause
of this accident was the flightcrew’s failure to use engine anti-ice during ground operation
and takeoff, their decision to take off with snow/ice on the airfoil surfaces of the
aircraft, and the captain’s failure to reject the takeoff during the early stage when his
attention was called to anomalous engine instrument readings. Contributing to the
accident were the prolonged ground delay between deicing and the receipt of ATC takeoff
clearance during which the airplane was exposed to continual precipitation, the known
inherent pitchup characteristics of the B-737 aircraft when the leading edge is
contaminated with even small amounts of snow or ice, and the limited experience of the
- flightcrew in jet transport winter operations.
Pitch up characteristic of frosted ower 732 was
contributing, not
casual factor. If (hypothetically) anyone puts forward the theory of it being the main culprit while dismissing the real casual factors as "red herring" it would be conductive to entertainment, not to learning and understanding.
Originally Posted by cwattters
I'm curious.. It's well known contamination can increase the stalling speed but would the stick shaker also operate at a higher airspeed? How does the stall warning sensor know there is contamination or is it only looking at air speed and AOA?
It looks only at AoA and I have to stand corrected here; what I wrote is valid for AoA, not airspeed as:
Originally Posted by NTSB report AAR82-08
Most air carrier aircraft are equipped with a stickshaker or some other type of
alarm to alert the pilot that his aircraft is approaching the stall angle of attack. In the
B-737, the stickshaker is activated when a fuselage-mounted vane aligns itself with the
airflow and reaches a preset angle of attack which is less than the stall angle of attack.
The normal alarm margin is equivalent to about 10 percent of the stall airspeed. Since
the stall warning activation is independent of the actual airflow conditions on the wing,
the angle of attack at which it will activate is not affected by snow or ice contamination
on the wing. However, if the wing’s lift-producing efficiency is reduced by such
contamination, the aircraft will be maintaining a higher than normal airspeed when flown
at the angle of attack at which the stickshaker will activate in order to compensate for
the degraded efficiency of the wing.
Thus, the stickshaker will activate at a higher-than-normal airspeed.
Furthermore, the angle of attack margin, and thus the airspeed margin, between
stall warning, stall buffet, and stall will be reduced significantly
or negated entirely.