12 February 2004
Transport Canada has received Special Airworthiness Information Bulletin (SAIB) NM-04-37 from the United States Federal Aviation Administration (FAA), alerting maintainers, operators and owners of this potential safety issue.
The following are excerpts from that publication:
"The FAA has received reports stating that during two accidents involving transport category airplanes, several passengers' seat belts had released from the seat attachments (i.e., the seat belts remained buckled but had become unhooked at their attachment fittings to the seat). The absence of damage to the hook end of the seat belts and the "D-ring" type seat belt attachment fittings suggests that in each case, the fitting aligned with the opening in the hook end of the seat belt, and the seat belt became detached from the "D-ring" type seat belt attachment fittings. Detachment of a seat belt from the "D-ring" type seat belt attachment fittings could result in injury to the seat occupant during an accident, turbulence, or a hard landing."
"During our investigation, we discovered one repeatable method of demonstrating the seat belt detachment. When the hook end of the seat belt is near the seat belt fastener that attaches the fitting to the seat, the seat belt hook end can become aligned such that the hook end is contacting two points on the "D-ring" fitting. In this configuration, the spring keeper on the hook end of the seat belt is in alignment with the upper portion of the "D-ring" type attachment fitting. Detachment occurs when an out-of-plane load is applied to the hook end of the seat belt by the seat belt webbing. As the seat belt attempts to align the hook end of the seat belt with the load, the spring keeper is depressed and the seat belt becomes detached from the fitting."
Below is a list of known aircraft manufacturers that may have this type of "D-Ring" installed in their aircraft. For specific models, please refer to FAA Special Airworthiness Information Bulletin (SAIB) NM-04-37 which can be found at http://www.faa.gov/. Other manufacturers and models may also have this type of "D-Ring" installed.
BAE Systems Limited
British Aerospace Airbus Ltd.
Cessna Aircraft Company
Dassault-Aviation Fan Jet Falcon
Gulfstream Aerospace Corporation
Gulfstream Aerospace LP (Israel Aircraft Industries, Ltd.)
Israel Aircraft Industries, Ltd.
Lockheed Martin Corporation
SAAB Aircraft AB
Shorts Brothers PLC
Transport Canada recommends that operators and AMEs inspect passenger seat belts at the earliest possible convenience. If the seats have the "D-Ring" type belt attachment fitting, an inspection should be carried out for security and proper operation of the "D-Ring". Operators may elect to change the "D-Ring" style for an improved style of attachment fitting.
For further information contact a Transport Canada Centre, or call Mr. Steve Dudka, Continuing Airworthiness, Ottawa, telephone (613) 952-4361, facsimile (613) 996-9178 or e-mail firstname.lastname@example.org
Any further defects or occurrences should be reported to Transport Canada, Continuing Airworthiness, Ottawa via the Service Difficulty Reporting program.
For Director, Aircraft Certification
for Bohdan Goyaniuk
Chief, Continuing Airworthiness
Note: For the electronic version of this document, please consult the following Web address:http://www.tc.gc.ca/eng/civilaviation/certification/menu.htm