It isn't any wonder so many fear this tragedy to be yet another act of terrorism straight from the evil mind of Osama Bin Laden. However, what we know so far doesn't seem to add up to the kind of crash that would be produced by a deliberate act of sabotage.
All airliners are design-certified to be able to continue to climb, at maximum certified gross weight and at the most critical time in the takeoff profile, in the event of a total loss of power from one engine.
Then, why did that plane crash?
Witnesses were said to have seen smoke and flames trailing from one engine, and finally observing that engine fall off, shortly before the crash. In addition, a loud "explosion" sound was also reported by ground witnesses, prior to the crash. That led to initial speculation that engine failure was the cause of this crash.
When thrust is lost from one engine, the pilot must quickly act by pushing in the rudder and rolling in aileron, towards the side of the remaining good engine. If a pilot fails to respond in that manner, the plane would roll upside down and total control would quickly be lost.
The rudder is attached to the trailing edge of the vertical stabilizer. When a vertical stabilizer breaks free from a plane, the rudder goes with it. At that point, the only way a pilot could prevent the plane from rolling over on its back, is by retarding the throttle on the remaining good engine. With the power from that good engine no longer available to the pilot, he would have no choice but to descend towards mother earth. If he tried to arrest that descent, by pushing the throttle forward again, the plane would start to roll, because the rudder was gone. Caught between a rock and a hard place, a pilot could only try to extend his glide to a certain crash, by advancing the thrust lever no more than his limited aileron roll control would permit.
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Pictures of the vertical stabilizer, as it was lifted from Jamaica Bay, revealed a very clean break at the bottom edge, where it had been bolted to the fuselage. It looked pristine, as if it was being moved from a production line to be mated to a new production fuselage. Without any visible damage to that stabilizer, one could not reasonably conclude it had been ripped away by physical contact with other parts flying off the plane. Neither would that pristine condition allow for a terrorist bomb inside of the fuselage, as a sensible explanation. The "black boxes" (CVR and FDR) were found in the main crash site area, indicating the rest of the tail section, below the departed vertical stabilizer/rudder, remained attached to the fuselage. That would tend to indicate a bomb was not the cause of the stabilizer/rudder separation from the fuselage.
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It now seems the failure of the stabilizer/rudder is the key to analyzing the causal factors in this accident. Could it have been an act of sabotage? Nothing can be ruled out at this early stage of the investigation, but I see that to be a very remote possibility. Human failure in the design, operation, or maintenance of the airplane is much more likely.
November 14, 2001
Robert J. Boser
Editor-in-Chief
AirlineSafety.Com
Aviation Week & Space Technology:
November 4, 2002AA587 Hearing: Rudder
'Key' To Solving MysteryFRANCES FIORINO and MICHAEL A. DORNHEIM/WASHINGTON
Investigators remain puzzled by A300-600R flight crew's reaction to mild wake encounter
Last week's NTSB public hearing into the American Airlines Flight 587 accident left the main question unanswered--why did the Airbus A300-600R's rudder move from stop to stop five times, causing the vertical stabilizer to be torn from the transport?
The hearing proceeded with the implicit assumption that a crewman was moving the rudder, and not a system malfunction. "To date, investigators have found no indications of any rudder system anomalies, but investigation in this area continues," said Robert Benzon, the NTSB investigator-in-charge.
Keeping in mind that until the Nov. 12, 2001, crash of Flight 587, most transport pilots were unaware that rapid rudder reversals could cause the tail to rip off the aircraft, the safety board zeroed in on why and how this crucial information, familiar to flight test engineers and manufacturers, is not included in pilot upset training programs.
Edward States was captain of Flight 587 and First Officer Sten Molin was at the controls when the A300-600R, N14053, Serial No. 420, departed New York JFK International Airport at 9:14:35 a.m. en route to Santo Domingo. The aircraft twice encountered wake vortices of Japan Airlines Flight 47, a Boeing 747-400 that had departed about 1 min. 45 sec. earlier from the same runway.
DIGITAL FLIGHT DATA Recorder and Cockpit Voice Recorder (DFDR and CVR) data (see pp. 50, 51) shows the A300-600R encountered the first wake vortex at 9:15:36 a.m., the second at 9:15:51 a.m. In the last 8 sec. of FDR data, the A300-600R experienced three lateral movements, two to the right at 0.3g, and 0.4g and one to the left at 0.4g, which were consistent with rudder movements.
Shortly after the second occurred, Molin called for "max power"but why, if airspeed was only about 10 kt. below target of 250 kt. (see p. 50)?John Cox, Air Line Pilots Assn. executive air safety chairman, suggested the first officer, reacting perhaps to a sluggish feel to the aircraft, might have wanted to reduce the number of variables he was dealing with and increase power from climb to max. continuous.
At about 9:15:59 a.m., the vertical tail fin departed the aircraft and the A300-600R crashed into the Belle Harbor, N.Y., residential community, killing 260 onboard and five people on the ground.
Immediate actions were taken, with the FAA issuing an emergency AD 2002-23-51 that called for visual inspection of the composite tail structure. In addition, Airbus reviewed service histories of A300 and A310 aircraft that had encountered inflight upsets that resulted in heavy lateral loads that might have compromised structural integrity of the aircraft.
They found three A300-600 cases where limit load was exceeded, including one where ultimate load was exceeded, probably several times--the FDR failed for part of the sequence. This was American Airlines Flight 903, an A300B4-605R (N90070) the most striking in similarity to the high lateral loads on Flight 587. On May 12, 1997, the aircraft experienced several rudder "doublets" or reversals.
The A310 had the same record--three cases where limit load was exceeded, including one that exceeded ultimate load. This was an Interflug flight in 1991 that lost control during a go-around, with speeds ranging from 50-300 kt. and pitch attitudes up to 80 deg. during the event, caused by mistrim from a pilot-autopilot fight (AW&ST Jan. 30, 1995, p. 57). All aircraft were inspected and only the Flight 903 tail showed damage.
But the most stunning of all actions in the wake of the Nov. 12 accident was NTSB's interim recommendations, A-02-01/-02, on Feb. 8, which said transport pilots must be made aware that sudden rudder movements could jeopardize structural integrity of the aircraft. Most pilots had never heard of this possibility (AW&ST Feb. 18, p. 44 and Jan. 21, p. 24).
Upon discovering this information, an American Airlines Boeing 737 captain, John F. Lavelle, reported to the airline that he had observed Molin, whom he described as a "perfectionist" with excellent skills, applying excessive rudder input on several 727 flights they operated in 1997.
On one occasion, during initial climb in a 727 at Flaps 5 and 1,000-1,500 ft., the aircraft crossed a mild wake and Molin stroked the rudder pedals "1-2-3, about that fast," to nearly full deflection while using little or no aileron. Lavelle thought they had lost an engine and asked Molin what he was doing. Molin said his action was "per the American Airlines Advanced Aircraft Maneuvering Program," which he claimed directed him to use rudder.
Lavelle said the rudder pulses didn't level the wings and just caused yaw motions with heavy side loads, and the wake only required a little aileron. Molin insisted the AAMP directed the use of rudder in this manner, but Lavelle said that was for lower speeds.