Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
SW-07-37
June 8, 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. Model OH-58A, OH-58B
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-58B 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.