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.”

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.”

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.

Early in the investigation, then NTSB Chairperson Marion Blakey said, “We do not know [if those rudder movements] were caused by the pilots.”

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:

The NTSB did not find any fault with the composite plastic design of the tail fin; however, it did immediately order a one-time visual inspection of all A300-600 and A310 tail fins within 15 days to look for “edge delaminations, cracked paint, surface distortions, other surface damage, and failure of the transverse (side) load fittings.  Similarly, indications of failure of the rudder assembly, which could lead to failure of the vertical stabilizer, may be detectable with such an inspection.”

Ellen Connors, the former chairperson of the NTSB has stated that the report was delayed because of “inappropriate and intense lobbying by Airbus over its contents” and that “the potential for contaminating the investigation exists.”

Following the crash of AA587, United Airlines decided to go beyond the required visual inspection to conduct ultrasound tests on three of its A320 jets, whose plastic tail fins had also been repaired at the factory before delivery.  The test found a flaw in a six-year-old A320 on the opposite side of the stabilizer from where the factory defect had been repaired.  In spite of the defect, Airbus spokesman David Venz said the defect is in an area that doesn’t support the weight of the tail.  He said, “We are confident this airplane is fit to fly.”

Airbus claimed that damage that couldn’t be seen cannot weaken the plastic tail fins and that visual examinations were sufficient.  One official said, “Invisible damage cannot produce a significant sub-surface flaw.”

Unconvinced, some American Airlines pilots called for more detailed inspections, such as ultrasound to locate hidden flaws. 

More than 20 American Airlines pilots asked to be transferred to Boeing aircraft, “although this meant months of retraining and loss of earnings.” One pilot wrote that “he had refused to let any of his family take an A300 or A310 and had paid extra to take a circuitous route on holiday purely to avoid them.”

Saying there was no way to adequately inspect the plastic tail fins, dozens of American Airlines pilots demanded that the company ground its fleet of Airbus A300 jets until the cause of the crash of AA587 could be determined.

More than 70 pilots signed a statement stating, “Until a definitive cause for the crash of Flight 587 can be determined, along with ways to prevent a similar occurrence, and/or a definitive test can be developed to truly check the structural integrity of the vertical stabilizers of our remaining 34 A300s, I recommend that American Airlines’s fleet of A300s be grounded.”

Weighing in on the side of the pilots, Professor James H. Williams, Jr., of the Massachusetts Institute of Technology, School of Engineering, stated that the Airbus position regarding the adequacy of visual inspections was “lamentably naive policy.  It is analogous to assessing whether a woman has breast cancer by simply looking at her family portrait.”

Regarding the repairs performed by Airbus on composite tails with discovered defects prior to deliver, Dr. Williams states, “Such repairs of structural damage in composites are frequently unreliable, especially for joints and attachments involving primary (load-bearing) structures.  The rupture of the vertical stabilizer on Flight 587 occurred in the vicinity of repairs, adjacent to an attachment point.  Therefore, the FAA must carefully establish and articulate a policy for the repair of primary composite structures.” 

“Finally,” Dr. Williams concludes, “Airbus’s extensive design and testing programs for the A300-600 composite vertical stabilizer may be currently deficient if they were based on outmoded or flawed engineering assumptions or an inadequate certification process.  No amount of analysis can overcome faulty assumptions or insufficient requirements.”

Even in the absence of an overloading or catastrophic event, Dr. Williams believes that, “When subjected to the loading histories of some aircraft, composites will lose both strength and stiffness.  Furthermore, studies of the long-term effects of exposure to aircraft environments of moisture, pressure and temperature, as well as fuels, hydraulic fluids, lubricants and deicers remain to be conducted for many composite materials.”

His research has shown that, “repeated journeys to and from the sub-zero temperatures found at cruising altitude causes a build-up of condensation inside composites, and separation of the carbon fibre layers as this moisture freezes and thaws.” Dr. Williams says it is “like a pothole in a roadway in winter, over time these gaps may grow.”

January 2002 - Federal Express Flight.  A pilot flying an Airbus A-300 freighter “complained about strange ‘uncommanded inputs’ – rudder movements which the plane was making without his moving his control pedals.  In FedEx’s own test on the rudder on the ground, engineers claimed its ‘actuators’ – the hydraulic system which causes the rudder to move – tore a large hole around its hinges....” 

The mechanics “found that hydraulic fluid had caused some of the composite material in the plane’s rudder to ‘disbond,’ or come apart.”

The mechanics also “found bent and broken rudder control system components, as well as associated disbonding of the composite tailfin.” The mechanics “unearthed a synchronization issue, wherein hydraulic pressure pulses from different sources can get out of phase.” The resulting “oscillation was felt as a sustained vibration, and then a loud bang was heard.”

The rudder assembly “may represent a telltale of “yaw oscillation.” NTSB investigators immediately focused on the implications of the damaged/broken rudder control components found on the FedEx airplane and their possible relevance to the AA587 crash.  “It appears that the system damaged the rudder.  ‘That is not supposed to happen; the system should break out first,’ states an NTSB official.”

March 2005 - Aboard Air Transat Flight 961 Over the Caribbean Sea.  On March 6, 2005, an Airbus A310-300 with 262 passengers was cruising at 35,000 feet when the “flight crew heard a loud bang followed by vibrations that lasted a few seconds.  The aircraft entered a repetitive rolling motion, known as a Dutch roll, which decreased as the aircraft descended to a lower altitude.”

The crew was able to turn the plane around and return to Varadero, Cuba, where they carried out an uneventful landing.  Upon arrival, it was discovered that the aircraft rudder had been torn off the plane, except for its “bottom closing rib and the length of spar between the rib and the hydraulic actuators.”

“An examination of the vertical tail fin of the aircraft, to which the rudder is attached, determined that the two rearmost fin attachment lugs were delaminated, likely the result of stresses that existed during the rudder separation.”

In its report about the occurrence, The Transportation Safety Board of Canada (TSB) observed, “At the time of this occurrence, composite materials in general were from a maintenance perspective, believed to have a no damage growth design philosophy.  It was also believed that from a fatigue point of view, more frequent inspections of composite materials would not prove to be more effective.”

The TSB report recommended:

On March 27, 2006, TSB reported that the required inspections “found examples of disbonds, damage around hoisting points and trailing edge fasteners of the rudder, corrosion and abrasion at hinges, seized hinges, hinges with excessive free play, water ingress, and hydraulic fluid ingress.”

TSB commenced “work with the National Research of Canada to identify suitable inspection techniques that will detect failures in composite materials.”

November 27, 2005 - Aboard Federal Express Flight.  During routine maintenance, the rudder on an Airbus A300-600 was accidently damaged.  To access the extent of damage, “the rudder was shipped to the manufacturer’s facility and examined.  In addition to the damage that occurred during maintenance, the examination found a substantial area of disbonding between the inner skin of the composite rudder surface and the honeycomb core, which is located between two composite skins.

Further examination “of the disbonded area revealed traces of hydraulic fluid.  Hydraulic fluid contamination between the honeycomb skin and the fiberglass composite skin can lead to progressive disbonding, which compromises the strength of the rudder.  Tests on the damaged rudder also revealed that disbonding damage could spread during the flight.”

The NTSB determined that existing “tap tests” on the external surfaces of the rudder were unlikely to disclose “the disbonding of an internal surface.” The NTSB recommended a more stringent compliance time for inspections and requested that the FAA make the inspections mandatory.

In December 2007, the European Aviation Safety Agency ordered frequent and extensive testing on the composite rudders of the Airbus A300/310 series due to safety concerns.  Only about 20 wide-body A330 and A340 planes were included in the order, which did not include any of the A320 series.  The tests had to be completed with six months, and certain airplanes had to be retested every 1,400 flights.

The rudders of approximately 420 older Airbuses “are being subjected to repetitive ultrasonic and other enhanced inspections, the first time airlines and safety regulators have resorted to such recurring, high-tech procedures to determine the integrity of composite parts on airliners already in service”

It is not known whether the inspection order applied to the A330 operated by Air France Flight 447 (see below), or if the aircraft was ever tested.

The order represents a vindication of the American Airlines pilots, who had called for such inspections five years earlier and for Dr. Williams, who had supported their efforts.

The order also represented a repudiation of Airbus’ maintenance standards that “simple visual inspections, combined with a mechanic’s manually tapping on the surface of the composite rudders, were adequate to detect any potentially hazardous internal flaws or structural weaknesses.”

November 18, 2008 - Aboard XL Airways (Air New Zealand) Flight 888T Over Mediterranean Sea Off the French Coast.  Two German XL Airways pilots, accompanied by five representatives of Air New Zealand and a member of the Civil Aviation Authority of New Zealand, were operating an A320 in a test flight.

The aircraft had been leased by Air New Zealand to XL Airways and had been serviced and repainted in preparation for a return to Air New Zealand service.

The aircraft disintegrated when it crashed into the water and its tail fin was found floating at the crash site.  The flight recorders were recovered, along with several of the bodies.

The cause of the crash is still under investigation by French, German, New Zealand and U.S. regulators; however, the interim findings are that the “crew lost control of the aircraft.  While conducting an incompletely-planned test of low-speed flight at low altitude, the aircraft was descending through 3,000 feet on full autopilot for a go-around.  Landing gear was just extended when ... the speed dropped from 136 to 99 knots in 35 seconds.”

“The stall warning sounded four times during violent maneuvering to regain control.... the warning had silenced as the aircraft regained speed in a rapid descent, but six seconds later, at 263 knots, the aircraft had only 340 feet elevation and was 14 degrees nose down.  A second later it was in the water.”