Pitch Housings Vertical Pin Lugs

FAA Aviation Safety SPECIAL AIRWORTHINESS INFORMATION BULLETIN SAIB: SW-11-03 SUBJ: Pitch Housings Vertical Pin Lugs Date: October 22, 2010 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) advises you, the owners and operators of Columbia Helicopters, Inc (CHI) Model 234 (previously designated as Boeing model 234) helicopters to follow certain practices when performing maintenance and overhaul of the Aft Rotor Assembly, containing a pitch housing, part number (P/N) 145R2075/234R2075-all dash numbers.

Background

On March 26, 2009, a CHI Model 234 helicopter experienced a failure due to a crack on the aft rotor head pitch housing vertical pin lower lug, P/N 145R2075-12. CHI found the crack during an inspection following a flight. No secondary indication or damage resulted from this failure. In November 2007, Boeing reported the failure of the same part on a Model CH-47 helicopter owned and operated by the Japanese Ground Self Defense Force. The fatigue cracks in both cases initiated from fretting between the liner and the machined surface of the interior diameter of the lower lug.

Recommendations

We recommend that all owners and operators of the CHI Model 234 helicopter perform ultrasonic inspections specified in Columbia Helicopters, Inc. Alert Service Bulletin Number 234-62-A0002. This Alert Service Bulletin supersedes Service Letter 234-0014.

For Further Information Contact

Jean Aby, Rotorcraft Program Manager; Seattle Aircraft Certification Office, ANM-100S, 1601 Lind Ave SW, Renton, WA 98059; phone: (425) 917-6406; fax: (425) 917-6590; e-mail: [email protected]. 1