US FAA officials say they have found evidence that an AAR maintenance facility in Miami improperly maintained and approved for return-to-service Boeing 707, 747, 757, and 767 series main landing gear (MLG) truck beams.
But AAR is apparently disputing and seeking to clarify certain points cited in the 25 March FAA unapproved parts notification (UPN), which originated from a South Florida Flight Standards District Office (FSDO), and has received press attention at a time when US regulators are focusing their spotlight on aircraft maintenance programs in the face of high-profile infractions.
FAA says evidence received by the agency between 1 January 2001 and 26 November 2007 indicates AAR Landing Gear Services approved MLG truck beams for return-to-service that were not maintained in accordance with the manufacturer’s maintenance manual.
The notice specifically addresses enamel paint applied to the inside surfaces of the Boeing airliners’ MLG truck beams. Among the discrepancies cited by the FAA was the approval and return to service by AAR Landing Gear Services of MLG truck beams that had been overhauled with the application of Boeing “color 707 gray gloss enamel” inside the surface area of the truck beams, contrary to maintenance manuals.
AAR in a lengthy statement today notes that the UPN does not require taking any corrective action “nor does it change the time a landing gear with painted interior surfaces can remain in service nor does it require the removal of any landing gear from service”.
AAR Landing Gear Services also failed to document in maintenance records the application of this enamel inside the surface area of the truck beams or deviations from the manuals, FAA says.
Additionally, the agency notes AAR Landing Gear Services failed to document - and approved for return-to-service - Boeing 757s with the application of the enamel inside the surface area of the truck beams, contrary to manuals and an alert service bulletin directed by a 2001 airworthiness directive.
The AD, applicable to certain 757-200 and -300 series airplanes, required repetitive clearing of the drain passage at the aft end of the MLG truck beam to ensure moisture and contaminants within the truck beam can properly drain; and, for certain airplanes, an internal inspection of the truck beam to detect discrepancies, and follow-on actions. The actions specified by this AD were intended to prevent stress corrosion cracking, leading to fracture of a MLG truck beam during ground operations, which could result in either reduced controllability of the airplane or a fire, according to AD.
The FAA is encouraging the inspection of 707, 747, 757, and 767 MLG truck beams approved by AAR Landing Gear Services for return-to-service; hundreds of beams are known to have been returned to service by AAR during the near six-year period mentioned in the report.
In addition, the FAA says it “would appreciate any information concerning the discovery of the Boeing series MLG truck beams from any source, the means used to identify the source, and action taken to remove the MLG truck beam assemblies or aircraft accessories from service”.
In its response to the notice today, AAR says: “Painting the internal bore of landing gear beams has been an industry standard practice for years. The paint is applied as an additional layer of protection against the environment, thereby inhibiting corrosion from forming. While the requirement to paint the internal bore previously contained in the Boeing manual has been dropped as a requirement, painting of the internal bore continued to be a standard industry practice.”
With respect to the referenced airworthiness directive, AAR says it appears this “is not applicable to the application of paint to the inside surfaces of MLG truck beams. Rather, the airworthiness directive applies to operators of 757-200s and -300s with respect to periodic in-service landing gear inspections designed to ensure that the aft drain hole of the main landing gear truck beam is clear.
“The enamel paint applied to the inner surface of the truck beam, is not the subject of the airworthiness directive and the paint does not extend to the area where the drain hole is located,” AAR explains.
When performing MLG overhauls pursuant to the maintenance manual, it adds, AAR “complies with the airworthiness directive and related alert service bulletins on behalf of the operator and ensures that the drain hole, which is the subject of the referenced airworthiness directive, is open”.
No accidents have been linked to the FAA’s concerns, although one major airline – US Airways – is openly discussing a 28 October landing gear failure while the 757 was parked at the gate preparing to close the door. There were no crew or passenger injuries reported.
“We had a truck beam fracture in the landing gear and the aircraft settled. As a result, we inspected five other 757s that had gear work performed by the same vendor, and we replaced some of the truck beams based on the indicators we were using,” says a US Airways spokesman.
“However none of the other aircraft ended up having a similar problem. And we (as well as the rest of the industry) did receive an Unapproved Parts Notice from the FAA but since we already inspected and replaced the truck beams we’re already in compliance,” the carrier says.
AAR states that Boeing has advised the company and the FAA that painting as an alternate finish application, as noted in the UPN, should be considered equivalent to the maintenance manual requirement provided the other overhaul instructions are followed. “Boeing also advised that the alternate finish scheme is not considered to be a time limited repair and overhaul intervals should continue as scheduled.”
Source: flightglobal.com's sister premium news site Air Transport Intelligence news