Airworthiness Directive · Amendment 39-12028 · Siam Hiller Holdings, Inc. Model UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12E, UH-12E-L, UH-12L, and UH-12L4 Helicopters
Siam Hiller Holdings, Inc. Model UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12E, UH-12E-L, UH-12L, and UH-12L4 Helicopters
Model UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12E, UH-12E-L, UH-12L, UH-12L4 helicopters, certificated in any category.
Note 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD), for Siam Hiller Holdings, Inc. (Hiller), formerly Rogerson Hiller Corporation, Model UH-12, UH-12A, UH-12B, UH-12C, UH-12D, UH-12E, UH- 12E-L, UH-12L, and UH-12L4 helicopters, that requires replacing all undrilled-shank bolts at pivoting joints in the control system linkage with drilled-shank bolts and installing castellated nuts and cotter pins. This amendment is prompted by an accident caused by separation of the control system linkage of a Model UH-12E helicopter. The actions specified by this AD are intended to prevent separation of the control system attachments at pivoting points and subsequent loss of control of the helicopter.
To prevent separation of the control system attachments at pivoting points and subsequent loss of control of the helicopter, accomplish the following:
(a) Replace all undrilled-shank bolts at pivoting joints in the control system linkage with drilled-shank bolts, and install castellated nuts and cotter pins in accordance with Hiller Aircraft Corporation Service Bulletin No. 10-4, Revision 2, dated December 20, 1999.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
