Main Landing Gear: Drag Arm

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FAA Aviation Safety SPECIAL AIRWORTHINESS INFORMATION BULLETIN SAIB: NM-12-39 SUBJ: Main Landing Gear: Drag Arm Date: August 1, 2012 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin advises registered owners and operators of all North American Model B-25 series airplanes of an airworthiness concern regarding failure of the drag arm of the main landing gear (MLG).

Background

A recent incident occurred during flight on a Model B-25 airplane which resulted in failure of the drag arm of the MLG located at the top of the shock strut. The drag arm forging failed upon landing, resulting in a forward collapse of the MLG and significant damage to the airplane.

Lab results from a National Transportation Safety Board investigation indicated that fatigue cracking initiated at multiple locations on the exterior surface of the I-beam flange, adjacent to a blend radius of the drag arm, resulting in such failure.

S & R Aviation Services Inc. has issued Mandatory Service Bulletin B-25-001, dated April 1, 2012. The service bulletin provides operators with guidelines for inspecting for cracking of the drag arm (part number (P/N) 65081) of the MLG, located at the top of the Bendix Pneudraulic landing gear shock strut (P/N 65929 (left-hand) or 65930 (right-hand)); and replacing the drag arm or strut, as applicable, if necessary.

The FAA has determined that the risk due to this issue is low enough that airworthiness directive (AD) action under Title 14 of the Code of Federal Aviation Regulations (14 CFR) part 39 is not needed. The risk is low due to several factors: the extremely low utilization of these airplanes, the high degree of voluntary compliance with the corrective action, the low fleet size, and the relatively low severity of a gear collapse.

Recommendations

The FAA recommends that owners and operators of all Model B-25 series airplanes comply with the guidelines outlined in S & R Aviation Services Inc. Mandatory Service Bulletin B-25-001, dated April 1, 2012.

For Further Information Contact

Dara Albouyeh, Aerospace Engineer, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Blvd., Suite 100, Lakewood, California 90712; phone: (562)627-5222; fax: (562) 627-5210; email: [email protected].

2 For Related Service Information Contact

S & R Aviation Services, Inc., 7000 Merrill Avenue, Chino Airport, Chino, California, 91710; phone: (909) 393-0074.