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      02-13-2009, 11:18 PM   #41
777ER
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Drives: 2007 328xi
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Quote:
Originally Posted by E90SLAM View Post
I remember that accident happened at Washington national airport....coz the 732 was lined up for takeoff for too long after its only de-icing....snow and ice accumlate on its wings during the hold....and the crew did not turn on the de-icing switch....
the aircraft had liftoff a little bit but not enough to encounter the disruption of airflow on the wings....finally crashed into freezing river....
There's no de-icing switch on the 732. It's anti-ice.

There's more to the story than just inexperience and the hold...

The aircraft was deiced by the airport workers while it was at the gate waiting for the weather to clear up a lil.

then the tug had problems getting enough traction in the snow to pushback the 732...
the captain then elected to use the thrust reversers to assist in the pushback to reduce the departure delay...

it did work...but the thrust reversers did kick up snow and slush from the ground onto the top of the wing...and some of that ended up going into the intake of the engine

the pitot tube in the intake of the engines got snow/slush into it and it gave a false high reading (smaller diameter now, high velocity flow)...

so the crew sets the EPR (Engine Pressure Ratio, it's a power setting used on the P&W engines) for takeoff...down the runway it goes.....aircraft stalls (airspeed & angle of attack) and down it went into the river.

Right before the airspeed stalled (during climbout phase) the crew noticed the aircraft wasn't gaining enough speed as it should and added more power which was too late in this case (aircraft stalled already).
They did notice it took a long time to gain speed during the takeoff run...

The findings? Engine power was set too low due to false EPR reading.
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