American Airlines and several other U.S. airlines have changed the emergency procedure their DC10 pilots use if they lose power in one engine during takeoff. The new procedure might have saved the DC10 that crashed here May 25 and killed 273 people.
The change was announced this morning by Capt. Walter Estridge, the director of flight training for American Airlines, during his testimony in the National Transportation Safety Board's hearing on the accident.
The new procedure is merely a modification of the choice between altitude and speed inherent in powered flight. Under the new procedure, if an engine fails as a DC10 is taking off, the pilot will lessen the plane's angle of climb, which will permit the plane to fly at a higher rate of speed.
If American Airlines pilot Walter Lux had chosen to lower his DC 10's nose to gain speed -- a move contrary to his training and his airline's instructions -- it is probable that the plane would have survived.
A series of speed calculations must be made before every takeoff. Those calculations include variables such as the weight of the payload and the fuel needed, the temperature, wind conditions and the length of the runway.
The first calculated figure is called V-1. V stands for velocity; 1 is the point of no return. Once an airlrner has reached that speed, it must continue to take off, because there is not enough runway left to break to a halt.
The next point is V-R, standing for velocity-rotation. That is the point at which the plane is going fast enough for the nose wheel to lift off the ground.
The third point is called V-2. V-2 is calculated at 120 percent of stall speed, the speed at which the plane will no longer fly because there is inadequate lift or air flow on the wings.
In flight 191, the left engine and support pylon fell off the wing just as the plane was leaving the ground. In the process, some high-lift devices on the left wing, called slats, were knocked out.
Stall speed for a healthy wing with slats extended was calculated at 128 knots; V-2, thus was 153 knots. But when the slats retracted unexpectedly on the left wing, the loss of lift pushed the stall speed to 159 knots -- six knots faster than the plane was flying.
After a normal takeoff, with all engines functioning, American's procedures call for an initial speed of V-2 plus 10 knots. If one engine fails, however, the emergency procedure in effect May 25 called for the pilot to maintain only V-2 until he reached an altitude of 800 feet.
Shortly after takeoff, flight 191 was measured at V-2 plus 19 knots. The two remaining engines were developing full power and Capt. Lux chose to use that power to gain altitude and clear obstructions. Therefore he keep the nose of the airplane up, and let his air speed drop to V-2. At the point the left wing stalled and the plane rolled to the left and crashed.
Capt. Lux and the electronic aids in his cockpit were programmed to do just what he did.He never received warning of an impending stall because the fallen engine ripped with it the electrical power to his stall warning.
Under Ameriican's new emergency takeoff procedure, which was sent to DC10 pilots July 23, in most but not all conditions the correct speed with an engine failure will be V-2 plus 10 knots, which would have given flight 191 a four-knot margin.
The power to the engine would not have changed but the plane's angle of climb would have lessened. A Federal Aviation Administration official testified yesterday that some other U.S. airlines with DC10s are adopting similar procedures.
Estridge, American's training director, said that Capt. Lux had the authority to create almost any procedure he wanted in the emergency. However, the loss of the engine and the electrical system gave him few clues to the true condition of his plane. He had no way of knowing the slats on one wing had retracted, for example.
"To me, the situation was extremely difficult, if not impossible (for the crew), to assess during the time they had," Estridge said. "I was extremely proud."
The flight lasted 31 seconds.