Showing posts with label Turkish Airlines 1951. Show all posts
Showing posts with label Turkish Airlines 1951. Show all posts

Friday, March 28, 2014

Retraining airline pilots

Fundamental duty of a pilot is to keep the plane in the air.  "Keep the shiny side up and the greasy side down" the truckers say.   When an aircraft slows down, the air flowing over the wings slows down, reducing the lift.  To keep the plane in the air, you pitch the nose up, tilting the wings up (increasing the angle of attack) which makes the wings take a bigger bite of the air.  This can go on for quite some time, but sooner or later, the wing stalls, airflow becomes turbulent, lift vanishes, and the plane falls out of the sky.  This is a stall.  They have been known since Wilbur and Orville's time, and they are very dangerous.  If the plane keeps falling, it will hit the ground.
   In 2009 there were three bad fatal airline accidents, all caused when the aircraft stalled, the pilot was unable to recover, and the plane hit the ground.  In all three cases, the pilot's failed to fly out of the stall.  You fly out by pushing the stick forward, lowering the nose, trading off some altitude for speed.  The extra speed gives you more lift,  the reduced angle of attack reduces drag, which makes you go faster.  The worst case was the Air France crash in the South Atlantic.  With three pilots on the flight deck, they had the stick pulled full back right up until the plane hit the water.  Not one of the three pilots attempted to push the stick forward, get the nose down, and get some airspeed. 
   Investigation found that stall recovery pilot training emphasized adding power and not losing any altitude, rather than putting the nose down to gain speed.  Trouble with the add power strategy is simple, the engines probably don't have enough power to increase airspeed much.  By the time the aircraft is close to stalling, it already has pitched up quite a bit, increasing the angle of attack, which increases drag as well as lift.  The engines of airliners don't have the kind of power you find in fighter planes, they lack the power to accelerate the plane at high angles of attack.  In USAF we called this "Getting behind the power curve". 
   Anyhow, the industry is revamping pilot training, telling the pilots to push the stick forward, get some airspeed, and accept a loss of altitude.