AD 83-25-02

83-25-02 HILLER AVIATION: Amendment 39-4784. Applies to Models UH-12D, UH-12E, UH12E 4 Place, H-23F, and OH-23G series helicopters equipped with main rotor blades P/N 53200-03, serial numbers 038 through 286, certificated in any category. Hiller Model UH-12 series helicopters converted to turbine power by STC SH177WE or SK178WE are affected by this AD.

Compliance is required as indicated (unless already accomplished).

To prevent possible main rotor blade failure due to the delamination of the main rotor blade root doublers or skin bond separation, accomplish the following:

(a) Prior to further flight after the effective date of this AD, and prior to each subsequent flight, visually check the main rotor blade root doubler area for evidence of delamination. This check includes all doublers on the leading edge and trailing edge surfaces, upper and lower, from the fork attachment plate to the tip of the outboard doubler. Delamination will be evidenced by a lifting of the doubler edges and/or cracks in the painted surface.

(b) If the check indicates delamination, prior to further flight, replace the blade with a like serviceable part or consult the Manager, Western Aircraft Certification Office, for instructions and disposition of the blade. Descriptive data regarding the extent of the delamination must be made available to the FAA.

(c) The check required by paragraph (a) of this AD may be performed by the pilot, provided his logbook is endorsed by a properly rated mechanic stating that the pilot has been trained to conduct the check.

(d) Within the next 50 hours time in service after the effective date of this AD, and thereafter at intervals not to exceed 50 hours time in service from the last inspection, inspect the main rotor blade root doubler area for evidence of delamination in accordance with paragraph 2.B of Hiller Aviation Service Letter 51-3A, Revision 1, dated October 17, 1983, or an equivalent as noted in paragraph (i).If delamination is found, comply with paragraph (b).

(e) Within the next 100 hours time in service after the effective date of this AD, and thereafter at intervals not to exceed 100 hours time in service from the last inspection, inspect main rotor blades for evidence of skin bond separation in accordance with paragraph 2.A of Hiller Aviation Service Bulletin UH-12-51-7, Revision 1, dated October 3, 1983, or an equivalent as noted in paragraph (i).

NOTE: The main rotor blade bond separation occurred on the blade tip leading edge and extended a distance of approximately 2 feet.

(f) If the main rotor blade inspection indicates skin bond separation, prior to further flight, replace blade with a like serviceable part or consult the Manager, Western Aircraft Certification Office, for instructions and disposition of the blade. Descriptive data regarding the extent of the skin bond separation must be made available to the FAA.

(g) Mark all rejected blades "UNAIRWORTHY"on the blade upper and lower surface at the approximate mid span with lettering at least 2 inches high, and using a metal stamp, impress "UNAIRWORTHY" on the data plate.

(h) All checks and inspections are to be recorded in aircraft maintenance records.

(i) Alternative inspections, modifications, or other actions which provide an equivalent level of safety may be used when approved by the Manager, Western Aircraft Certification Office, FAA, P.O. Box 92007, Worldway Postal Center, Los Angeles, California 90009.

This supersedes Amendment 39-3897 (45 FR 56331), as amended by Amendment 39- 3935 (45 FR 65997), AD 80-18-01 R1.

This amendment becomes effective December 29, 1983.