Part 5
Through several in-flight turbulence and other instances where other portions of the structure was damaged, only the visual or coin tap methods were used to place these aircraft back into service. Over the years, many Airbus pilots noted water intrusion problems with the composite rudder and elevator of the A-300; many were concerned that the liquid would get inside the composite, freeze into ice at altitude, breaking the composite little by little, causing “fatigue” and that the fatigue would worsen—and weaken—the aircraft structure. This is known as “propagation.”
In Nov 2001, for the first time in large-jet-commercial-aviation history, the vertical fin breaks off of an airliner; 265 people die as a result. The aircraft is one of the first aircraft to feature a composite tail; it was the same tail that endured a 1995 turbulence incident that injured over 45 passengers—the worst turbulence incident in the history of its airline. No damage was discovered on the tail using the visual inspection methods directed by Airbus.
In 1997, another A-300, AA 903, encountered an “inflight upset” off Miami. The aircraft tumbled, stressing portions of the aircraft to the point where even both engines required replacement. The inspection methods advocated by Airbus revealed no damage, and the aircraft was placed back into service. Then-confidential memos between the carrier and Airbus indicated that Airbus “suspected empennage damage” and urged “deeper inspection.” Yet, the standard was simply to inspect using the visual method. Only when the aircraft was inspected in 2002, using ultrasound, was damage found that immediately grounded it and required removal of the vertical fin for good.
Air Transat 961—2002 Warnings Unheeded Nearly Cost More Lives
Then…in March 2005, Air Transat 961 had its entire rudder disintegrate in mid-air—an eerie reminder of the AA 587 catastrophe; yet, Airbus was nonchalant, issuing directives for more visual inspections; from the recent Safety Recommendation:
Following the Air Transat accident, on March 17, 2005, Airbus issued mandatory6 All Operators Telex (AOT) A300-55A6035 specifying a one-time rudder inspection for all A-300 series airplanes equipped with premodification 8827 or 40904 rudders. The AOT recommended that operators perform a tap test on the external surfaces of the rudder skin panels and spar in specific localized areas to inspect for disbonding damage. The AOT did not recommend that a tap test be performed on the inner surfaces. On March 28, 2005, the FAA issued Airworthiness Directive (AD) 2005-07-07, requiring operators to perform the inspections specified in the AOT. American Airlines and Federal Express (the only U.S. operators of these airplanes) complied with the AD.
Even these discovered delamination on Airbus rudders that required repair. (It is noteworthy that there is an apparent omission of UPS as a US Operator of “these airplanes”…which begs the question: did UPS comply with the AOT…or, better yet, were they ever notified?)
Airbus has issued another directive after yet another A-300 rudder-disbonding incident—the rudder was found to be disintegrating on a Fed Ex aircraft. Yet, even after all of these incidents, Airbus is seemingly nonchalant, ordering an inspection that allows the suspect aircraft to fly hundreds of flights before being looked-over—again, with visual inspections:
When the rudder from the Federal Express airplane was sent to Airbus for further testing, investigators found that the areas specified in the AOT did not include the areas in which the disbonds were found on the incident rudder. Further, it was determined that tap tests on the external surfaces of the rudder likely would not have disclosed the disbonding of an internal surface. As a result of these findings, Airbus issued mandatory7 AOTs A300-55A6042, A310-55A2043, A330-55A3036, and A340-55A403, on March 2, 2006, notifying operators of applicable A-300 series airplanes that large disbonds between the rudder’s inner skin and the honeycomb core could go undetected. The AOTs call for a visual examination, within 6 months or 500 cycles, for the presence of contaminant hydraulic fluids on rudder external surfaces and the performance of a manual tap test inspection at the inner side of the rudder panels.
NTSB Counters Irresponsible Airbus Policies
This time, the NTSB was concerned enough to make the inspections, in an urgent recommendation, “as soon as possible,” with a repetitive inspection “interval”…or, subsequent re-inspections.
On March 2, 2006 Airbus issued AOTs notifying operators of applicable A300 series airplanes that large disbonds between the rudder's inner skin and the honeycomb core could go undetected, and providing guidance for inspecting the rudders. The Safety Board is recommending a more stringent compliance time than specified in the AOT and also requesting that FAA make the inspections mandatory.
More recent examinations have disclosed that hydraulic fluid can exist along the edges of the rudder's inner surface along with an accompanying area of substantial disbonding and that the inspection specified in the AOTs cannot detect the presence of the hydraulic fluid or the disbonding along the edges.
Therefore, the Safety Board is recommending that the FAA require that all operators of Airbus A-300 series airplanes immediately (possibly before further flight) comply with four Airbus All Operators Telexes dated March 2, 2006. Any disbonding to the rudder skins that occurs in the presence of hydraulic fluid contamination should be repaired or the rudder should be replaced as soon as possible, well before the 2, 500 flights specified in the AOTs. (A-06-27) This is an urgent recommendation.
The NTSB further recommended that the FAA establish a repetitive inspection interval for Airbus premodification 8827 rudders until a terminating action is developed. The interval should be well below 2,500 flights. (A-06-28)
1 Airbus identifies the configuration by which the rudder skin panels were attached to the front spar on some A300s and A310s, including the incident airplane, as premodification 8827. In this configuration, rivets penetrate the rudder’s honeycomb core to join the rudder skin panels to the front spar. This configuration is identified as premodification 40904 when used on A330s or A340s. About 400 A-300 series airplanes were manufactured with the premodification 8827 or 40904 configuration before the rudder skin panel and front spar interface was redesigned. There are no A330s or A340s on the U.S. registry.
Incredibly, Airbus dictated that, even if some damage is discovered, it should not be repaired, but allowed to remain un-repaired for an extended time period:
The AOTs further stipulate that if one disbond (per panel) is found but does not exceed 130 mm (5.1 inches) in diameter, then the panel should be reinspected or permanently repaired within 2,500 flight cycles. If one disbond (per panel) is found and is greater than 130 mm diameter but less than 200 mm (7.9 inches) diameter, a permanent repair must be performed before the next flight or an immediate temporary repair must be performed; the permanent repair must then be performed within 1,500 flight cycles. If a disbond exceeds 200 mm in diameter8 or if more than one disbond is found on one panel (even if no disbond exceeds 130 mm in diameter), the operator must immediately contact Airbus before the next flight with a detailed inspection report to obtain further instructions.
The NTSB, however, rejected the Airbus “solution” expressing that the Board:
“…is concerned that allowing an undetected hydraulic-fluid-induced disbond to exist for 500 flights, without supporting analysis or tests to better understand the safety risks, is unacceptable. Further, the Safety Board is concerned that some hydraulic fluid disbonds, when detected, would be allowed to exist for as many as 2,500 flights before the disbond is repaired. Rudder skin disbonds that are a result of hydraulic fluid contamination are particularly troubling because little is known about the progression rate once such disbonding is initiated. Contamination with hydraulic fluid will lead to a reduction in the bond strength and an overall loss in the rudder’s structural integrity, as found on the Federal Express rudder, and leaves the airplane susceptible to the type of rudder separation experienced during the Air Transat flight. The consequences of a rudder separation include reduced directional control and possible separation of the vertical stabilizer.”
The prevalence of hydraulic fluid leakage onto the surface of rudders throughout the A300-series fleet is unknown. The rate of growth of existing damage in the presence of this hydraulic fluid contamination is uncertain and currently unpredictable, and the resulting safety risks associated with the potential loss of the rudder or vertical stabilizer are severe. The Safety Board is aware that Airbus is considering exempting 24 aircraft from compliance with the current AOTs because, following the issuance of AOT A300-55A6035, these aircraft underwent additional nondestructive examinations. The Board is concerned that these tests may not have detected disbonds and that these aircraft should not be exempt from the current AOTs. The Safety Board is also concerned that there is a reasonable likelihood that disbonding damage similar to that found on the FedEx rudder, or worse, exists on other airplanes flying in the fleet today and that, given the uncertainty in the number of cycles to failure for composite rudders contaminated with hydraulic fluid, the safety risk over 500 additional flights is unacceptable. As a result, the Safety Board believes that the inspections specified in the AOTs should be conducted with the utmost urgency on all premodification 8827 rudders.