PHILADELPHIA -- January 25, 1995 -- "It's incomprehensible, says nationally-known aviation litigator, pilot and spokesperson for aviation safety, Arthur A. Wolk, "that the FAA today finally admitted the rudder played a likely role in the Pittsburgh USAIR crash, but does not know why. (The FAA previously certified the Boeing 737 and its rudder control system.) Anyone who has studied the Pittsburgh crash, and its striking similarity to the United 585 Colorado Springs crash, can point to the rudder as the most likely cause, and provide two simple interim solutions.
"What happened, on September 8th, was the airplane's power control unit (PCU) design flaw stuck again. When the yaw damper signaled the PCU to move the rudder, the unit activated the rudder to compensate, to a limit of 2 to 4 degrees. But that 2 to 4 degree limit doesn't work, because in both Pittsburgh and Colorado Springs, the unit overreacted and went into full deflection, causing the airplane to roll over."
Wolk says the FAA's recent suggestion for pilots to switch off the yaw damper when uncommanded rudder movement occur, is too late. "The rudder can move into full deflection within seconds and the pilot doesn't have a chance. If the rudder moves 18 degrees, the airplane rolls over and dives."
"Before more innocent passengers are killed, and before the PCU is redesigned, the FAA should mandate two mechanical adjustments. First, the authority of rudder movement must be limited to less than 18 degrees. Second, pilots must be given sufficient means to control the roll by training them to increase power to the "down" wing engine, reduce power to the "up" wing engine, and use the ailerons on the wing opposite to the direction of the roll.
