2
2
1
Between March 4 -11, 2002, the tail was physically removed from the plane and "two marks were found to be visible on the right rear attachment lug, one of six that attaches the fin to the fuselage. During ultrasound inspections, technicians [found] spots where the layers of composite material [had] separated, a condition called delamination." The right rear lug is in the same area where the tail from Flight 587 first broke away. [20]
Replacement of the tail by American Airlines cost more than $1 million. [21]
November 12, 2001 - Aboard American Airlines Flight 587 Over Queens, New York. Taking off a few minutes behind a Japan Airlines Boeing 747, the pilots of an Airbus A300-650R carrying 251 passengers on a flight from New York City to Santo Domingo quickly experienced air turbulence resulting from a wake vortex caused by the earlier flight.What the pilots did not know was that, when their plane had been originally delivered in 1988, layers of its plastic tail fin had separated, or delaminated, in the area where it was attached to the fuselage. The defect had been repaired by adding additional layers of plastic and rivets. American Airlines was informed by Airbus that no further inspections of the tail were required. [22]
The pilots did not know that their plane had experienced such severe high altitude air turbulence seven years earlier that 47 people were injured. Nor did they know the extent of any resulting damage was concealed within the plastic tail fin. [23]
Finally, the pilots did not know that their plane was designed with extraordinarily sensitive rudder controls that allowed the rudder to be moved beyond its design limits at low speeds by a movement of approximately one-and-one-half inches on the rudder pedal.
What we do know is that during the next few seconds, a series of right, left, right rudder commands moved the rudder beyond its design limits causing the entire plastic stabilizer to be torn from the fuselage by the force of flowing air.
What we still do not know is why. The pilots were killed along with everyone else aboard the plane and five people on the ground.
With the tail fin and both engines torn from the aircraft, the terror for those aboard, including five infants, was short-lived. The entire flight, from takeoff to impact, only lasted 103 seconds.
Following its investigation, the NTSB "determined that the probable cause of this accident was the in-flight separation of the vertical stabilizer as a result of the loads beyond ultimate design that were created by the first officer’s unnecessary and excessive rudder pedal inputs." [24]
Inasmuch as the plane was climbing from takeoff through a steady-state left turn when the turbulence was encountered, there is also the possibility that the first officer either was unintentionally thrown against the rudder pedal, he was unable to exercise such delicate movement of the rudder as to avoid exceeding the limitations of its overly sensitive design, or the rudder’s movements were independent of the pilot’s actions.
Captain Glenn Schafer, an A300 pilot who had flown with both the pilot and first officer of AA587, stated, "Both were excellent, well-seasoned pilots. Nothing I observed while flying with either of them could possibly lead me to conclude they would even attempt to move the rudder around in the fashion the FDR [flight data recorder] says it was moved." [25]
Schafer argues that, "in a wake turbulence encounter, such as occurred in the accident scenario, a pilot would not normally make a large rudder input and then snap-reverse it at 255 knots, the speed at which the accident airplane was climbing when the tail separated." He suggested, "a simple exercise with a stopwatch to illustrate that the pilots of Flight 587 could not have moved their feet that quickly." [26]
An aircraft control engineer supports Captain Schafer by maintaining "that if the pilots caused the rudder motion, it is doubtful, in a wake turbulence encounter, that they would have achieved virtually the same rudder deflection on each swing. The rudder always stopped at 10 degrees, a pattern that could be ‘explained’ by the yaw damper oscillating at its mechanical limit." [27]
The only information learned from cockpit voice recorder is a series of "rattling" noises as the plane encountered wake vortices generating a lateral force equal to 0.1 the force of gravity. Then, lateral forces equal to 0.3, 0.4 and 0.3 Gs were experienced coexistent with rudder movements. [28]
Early in the investigation, then NTSB Chairperson Marion Blakey said, "We do not know [if those rudder movements] were caused by the pilots." [29]
In its submission to the NTSB, the Allied Pilots Association pointed out ten previous incidents in which A300 tail fins had been stressed beyond their design limits and stated:
