SAIB SW-03-44 —

No. SW-03-44 June 20, 2003 We post SAIBs on the internet at www.airweb.faa.gov This is information only. Recommendations are not mandatory.

[This copy corrects the “For Further Information Contact”]

Potential Unsafe Condition Agusta A109 Helicopters Tail Rotor Trunnion P/N 109-0131-05

Purpose The purpose of this Special Airworthiness Information Bulletin is to inform operators of the Agusta A109 series helicopters of a potential unsafe condition which may exist on their helicopters. The FAA and ENAC, the airworthiness authority in Italy, are still investigating this potential unsafe condition.

Introduction On June 7, 2003, an Agusta A109K2 helicopter was involved in a fatal mishap. Investigation, although not complete, has revealed a potential unsafe condition with the Tail Rotor (T/R) trunnion, P/N 109-0131- 05-( ). Field investigation of the failed part indicated a fatigue crack that may have originated from a tool mark.

Examination The trunnion failed through the splined portion in approximately two equal halves (See photo 1). Initial examination reveals indications of fatigue (Photo 2). A mark on the outboard surface of the trunion was observed and appears to be a possible fatigue initiation point (Photo 3).

Although the exact cause of the mark is unknown we suspect it is a tool mark that was made during reassembly of the T/R hub after an inspection. During the installation and removal process of the T/R hub a washer (Fig 1 item 12) is bent to provide a locking feature to the spacer (Fig 1 item 13) and the retaining nut (Fig 1 item 10). The maintenance manual does not specify the method or tool for bending the washer, nor does it specify limits for scratches, dents, or other damage. However, the Component Maintenance Manual (Fig 2.) does specify a damage limit of 0.1 mm (0.004 inches) in Area 1.

Recommendation During disassembly and reassembly of the T/R hub, use extreme caution to not scratch, dent or otherwise damage the T/R trunnion. A one-time inspection should be accomplished to ensure the trunnion has not been previously damaged.

For Further Information Contact: Charles Harrison, Aerospace Engineer, ASW-112, FAA Rotorcraft Directorate; phone: (817) 222 5128; fax: (817) 222-5961; email: [email protected] 1

Figure 1.

Figure 2. 2

Photo 1 Separated Trunnion P/N 109-0131-05-115

Photo 2 Fracture Surfaces 3

Photo 3 Unknown Mark on Surface 4

U.S. Department of Transportation

Federal Aviation Administration

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