AD #: 2003-24-51

This Emergency Airworthiness Directive (AD) is prompted by a report of the failure of the bolt that secures parts of the main rotor swashplate and attaches the tail rotor blade. An examination revealed that the bolt failed due to hydrogen embrittlement. Hydrogen embrittlement is suspected to have occurred during the cadmium plating process of an entire batch of bolts, which makes the batch suspect. This condition, if not corrected, could result in failure of the bolt that secures parts of the main rotor swashplate and attaches the tail rotor blade, and subsequent loss of control of the helicopter.

The FAA has reviewed RHC Service Bulletin No. SB-51, dated November 24, 2003, that describes a daily preflight inspection and replacement of bolt, part number (P/N) NAS6605-31.

This unsafe condition is likely to exist or develop on other helicopters of the same type design.
Therefore, this AD requires, the following:

• Determining if maintenance has been performed on certain areas of the helicopter,
  determining if any bolt, P/N NAS6605-31, has been replaced, determining if the bolt
  vendor identification is 01DO, and determining the helicopter serial number.
• Visually inspecting and replacing if necessary, any unairworthy bolt before further
  flight and before the first flight each day of operation.
• Replacing certain bolts within 10 hours time-in-service or by December 31, 2003,
  whichever occurs first.

The AD also makes any bolt, P/N NAS6605-31, with vendor identification marking 01DO on the bolt head, ineligible for installation on any helicopter.
This rule is issued under 49 U.S.C. Section 44701 pursuant to the authority delegated... by the Administrator, and is effective immediately upon receipt of this emergency AD.

FMI: AD #: 2003-24-51