# SAIB NM-04-37: - Type: Special airworthiness information bulletin (advisory, not mandatory) - Status: Current - Revision: 0 - Issued: December 22, 2003 - Products: Transport Category Seat belt attachment fittings - Product type: Appliance - PDF: https://openairdocs.org/files/sha256/b0/64/b06416ea32da00536a5401a473a1606b4eedf846c60341764c556493386648ab - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/CE4712DFCC23AD3C8625721F0052ECB1.0001 - Page: https://openairdocs.org/saib/NM-04-37 ## Text Some pages are OCR from the scanned FAA bulletin. OCR can misread letters and numbers. **SPECIAL** **AIRWORTHINESS** **INFORMATION** **BULLETIN** Aircraft Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration No. NM-04-37 December 22, 2003 We post SAIBs on the internet at www.airweb.faa.gov This is information only. Recommendations aren’t mandatory. Introduction This Special Airworthiness Information Bulletin alerts you, owners and operators of airplanes with passenger seats equipped with “D-ring” type seat belt attachment fittings (see figure 1), that these fittings have the potential of inadvertently releasing the seat belts attached to them. The “D-ring” type of seat belt attachment fitting is a type that has been commonly used by most seat manufacturers. These fittings may be installed on, but not limited to the following aircraft: Aerospatiale (S.N.I.A.) ATR42 ATR72 SN-601 "Corvette" Airbus Industries A300 A310 A318 A319 A320 A321 A330 A340 BAE Systems Limited ATP BAe 146 Jetstream 4100 Series Boeing 707 717 727 737 747 757 767 777 2 Bombardier Aerospace Inc. BD-100-1A10 (Challenger) Bombardier Inc. BD-700- 1A10 (Global Express) CL-600-1A11 (CL-600 series) CL-600-2C10 (CRJ 700 series) CL-600-2D24 (CRJ 900 series) DHC-3 DHC-4 DHC-6 DHC-7 British Aerospace Airbus Limited BAC 1-11 Cessna Aircraft Company 500 550 S550 560 560XL 750 Dassault-Aviation Fan Jet Falcon Mystere-Falcon 20 Mystere-Falcon 200 Mystere-Falcon 50 Mystere-Falcon 900 Falcon 900EX Falcon 2000 Falcon 2000EX Embraer EMB-120 EMB-135 EMB-145 Fairchild Dornier GmbH 328-100 328-300 Fokker Services F27 F.28 Gulfstream Aerospace Corporation G-IV GV GV-SP Gulfstream Aerospace LP (Israel Aircraft Industries, Ltd.) Astra Galaxy Israel Aircraft Industries, Ltd. 1121 Learjet 24 25 31 35 45 55 60 Lockheed Martin Corporation L-1011 3 McDonnell Douglas DC-8 DC-9 DC-10 MD-11 Raytheon BAe.125 BH.125 DH.125 HS.125 Saab Aircraft AB SAAB 2000 SAAB 340 Short Brothers PLC SD3-30 SD3-60 Background The FAA has received reports indicating 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 (figure 2). 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. Figure 1 "D-ring" type attachment fitting ~ "D-ring" type attachment fitting fastener CAMI 11/15/1999 Figure 2 Spring keeper on the seat belt hook end is depressed by the seat belt attachment fitting Hook end of the seat belt is contacting two points on the attachment fitting 5 Recommendation The FAA recommends that you inspect your passenger seat (seat) belts. If the seats have the “D- ring” type of seat belt attachment fitting, we highly recommend that you replace the fitting with an improved design fitting. The seat belts on the passenger seats are replaced periodically because of wear in service. We recommend that you replace the “D-ring” type of seat belt attachment fittings as soon as possible but no later than when you replace the passenger seat belts. For seats that have Technical Standard Order (TSO) approval, the operator should contact the seat manufacturer of the seats for service information. For seats that aren’t TSO approved, the operator should contact the airplane manufacturer for service information. For Further Information Contact Jayson Claar, Aerospace Engineer, FAA Transport Airplane Directorate, Standards Staff, Airframe/Cabin Safety Branch, 1601 Lind Ave. SW, Renton, Washington 98055; phone: (425) 227- 2194; fax: (425) 227-1149; email: jayson.claar@faa.gov --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.