AD 93-24-13

93-24-13 THE ENSTROM HELICOPTER CORPORATION: Amendment 39-8968. Docket Number 93-SW-24-AD.

Applicability: Model F-28C, F-28C-2, F-28F, 280C, 280F, and 280FX series helicopters, equipped with a 24 volt D.C. electrical system, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the trim motor relay that could result in full deployment of the trim system, high cyclic control forces, and loss of control of the helicopter, accomplish the following:

(a) Within the next 5 hours' time-in-service (TIS) after the effective date of this airworthiness directive (AD), inspect the trim motor, wiring, and relays (trim system) for failure in accordance with the Compliance Section of The Enstrom Helicopter Corporation Service Directive Bulletin No. 0082 (SDB 0082), Revision A, dated March 18, 1993.

(1) Rewire the trim system and replace the trim actuator circuit breaker in accordance with paragraph 5.3 ofSDB 0082, Revision A, dated March 18, 1993, to preclude trim overtravel.

(2) After rewiring the trim system in accordance with paragraph (a)(1) of this AD, verify proper operation of the trim system and the limit switch stop position in accordance with the applicable maintenance manual.

(b) When installing a replacement or zero-time relay or circuit breaker, install in accordance with paragraph 5.3 of SDB 0082, Revision A, dated March 18, 1993. After wiring the trim system in accordance with SDB 0082, Revision A, dated March 18, 1993, verify proper operation of the trim system at the limit switch stop position in accordance with the applicable maintenance manual.

(c) Inspect the trim system for failure in accordance with the Compliance Section of SDB 0082, Revision A, dated March 18, 1993, at intervals not to exceed 100 hours' TIS from the last inspection or at each annual inspection, whichever occurs first.

(d) Replace any unairworthy trim system part with an airworthy part in accordance with the applicable maintenance manual.

(e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when approved by the Manager, Chicago Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Chicago Aircraft Certification Office.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Chicago Aircraft Certification Office.

(f) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the helicopter to a location where the requirements of this AD can be accomplished.

(g) The inspection, rewiring, and replacement shall be done in accordance with The Enstrom Helicopter Corporation Service Directive Bulletin No. 0082, Revision A, dated March 18, 1993. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from The Enstrom Helicopter Corporation, Twin County Airport, P.O. Box 490, Menominee, Michigan 49858. Copies may be inspected at the FAA, Office of the Assistant Chief Counsel, 2601 Meacham Boulevard, Room 663, Fort Worth, Texas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(h) This amendment becomes effective on August 26, 1994, to all persons except those persons to whom it was made immediately effective by Priority Letter AD 93-24-13, issued December 6, 1993, which contained the requirements of this amendment.