Corrosion on Main Rotor Blade

FAA Aircraft Certification Service SPECIAL AIRWORTHINESS INFORMATION BULLETIN SUBJ: Corrosion on Main Rotor Blade SAIB: SW-07-37R1 Date: June 21, 2007 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) advises you, owners and operators of Garlick Helicopters, Inc., Arrow Falcon Exporters, Inc., and San Joaquin Helicopters Model OH-58A, OH-58A+ and OH-58C helicopters, that corrosion has been found in the area around the inertia weight on main rotor blades. In a recent incident, this type of corrosion has initiated a main rotor blade spar crack. This bulletin also provides you with information on how to inspect the blades to determine if corrosion or cracks exist in that area.

Background

The FAA is aware of reports that corrosion has occurred in the area of the inertia weight on main rotor blade, part number (P/N) 206-011-250-003 and -113. This type of corrosion has been known to initiate cracks in the main rotor blade spar resulting in unserviceable blades. Main rotor blades, P/N 206-011-250-003 and -113, are susceptible to this problem as a result of the materials and processes used to manufacture these blades. In particular, the adhesive used to bond the inertia weight to the blade is known to absorb moisture which contributes to a corrosive environment. Bell Helicopter discontinued production of these blades in 1990 and began production of main rotor blade, P/N 206- 011-250-119, that same year as a replacement blade.

Recommendations

We recommend that you perform a recurring visual inspection on main rotor blades, P/N 206-011- 250-003 and -113, to ensure these blades are in a serviceable condition. The inspection should be performed at intervals not to exceed 8 hours time-in-service or 32 cumulative flights, whichever occurs first. The visual inspection is performed around the area of the inertia weight screw heads on the spar using a 10X power scope. Remove the paint from the area of the inertia weight and perform a visual inspection of the inertia weight screw heads and spar for evidence of corrosion or cracking. Any cracks in and around the inertia weight screw heads are cause for rejection and will render the blade unserviceable. If no cracks are present, remove any corrosion present in this area in accordance with the maintenance procedures provided in the applicable helicopter maintenance manual. Apply a clear coat as recommended by the manufacturer to ease in the recurring visual inspection. The current version of U.S. Army Technical Manual TM-55-1520-228-23 provides information to inspect and maintain OH-58A, OH-58A+ and OH-58C helicopters and should be referred to when performing any inspections and maintenance on these helicopters. Bell Helicopter Military Alert Bulletin USA-OH- 58-87-1, Rev. B, dated April 20, 2007, pertains to this subject.

For Further Information Contact

Mike Kohner, Aerospace Engineer, Rotorcraft Certification Office, ASW-170, 2601 Meacham Blvd, Fort Worth, TX 76137, telephone (817) 222-5447, fax: (817) 222-5783, Email: [email protected].