COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Hiller UH-12 Series Helicopters
AD/HILLER 12/40
Amdt 2
Main Rotor Assembly Drag Strut and T-T Bar Pin
1/98
Applicability: Models UH-12A, UH-12B, UH-12C, UH-12D, and UH-12E, and all models converted by STCs 177WE and 178WE.
Requirement: 1. Inspect the alignment of the outboard T-T bar pin, part number 51452, and adjust the alignment, if necessary, in accordance with Hiller Aviation Service Letter 51-2, dated March 31, 1978.
2. Inspect the head of the outboard T-T bar pin for cracks using a dye penetrant or magnetic particle inspection method.
3. Install shims between the inboard end of the drag strut and the outboard T-T bar pin in accordance with the Accomplishment Instructions of Hiller Aviation Service Bulletin 51-9, dated April 8, 1983.
Note: FAA AD 97-20-15 Amdt 39-10151 refers.
Compliance: 1. Unless the initial inspection is already accomplished, within 25 hours’ time in service after 1 January 1998, or at the next 100 hour inspection, whichever occurs first; thereafter at intervals not to exceed 100 hours’ time in service.
2. Unless the initial inspection is already accomplished, within 25 hours’ time in service after 1 January 1998, or at the next 100 hour inspection, whichever occurs first; thereafter at intervals not to exceed 100 hours’ time in service.
3. Unless already accomplished, within 25 hours’ time in service after 1 January 1998, or at the next 100 hour inspection, whichever occurs first.
The compliance of the previous issue of this Directive is unchanged for the repetitive inspection requirement and the one-time requirement.
This amendment becomes effective on 1 January 1998.
Background: Overseas reports were received of T-T bar pin failure due to fretting corrosion, which caused unacceptable vibration and emergency landings.
Amendment 1 included a repetitive inspection for cracks in the head of the outboard T-T bar pin as well as the shimming required by the initial issue of this Directive.
This amendment was prompted by two accidents overseas that were determined to have been caused by failure of the pin.
Amendment 2 is issued in response to a new FAA AD which allows a magnetic particle inspection of the T-T bar pin as an alternative to the currently required dye penetrant inspection.