AD 93-15-10

93-15-10 THE ENSTROM HELICOPTER CORPORATION: Amendment 39-8766. Docket Number 93-SW-21-AD. Final Rule of a Priority Letter AD.

Applicability: Model F-28A, F-28C, F-28C2, F-28F, 280, 280C, 280F, and 280FX helicopters equipped with composite-wrapped main rotor shaft, part number (P/N) 28-13183, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the main rotor shaft (shaft), loss of the main rotor, and subsequent loss of control of the helicopter, accomplish the following:

(a) Before further flight, after the effective date of this airworthiness directive (AD), perform a one-time inspection of the shaft in accordance with paragraph 5.1 of The Enstrom Helicopter Corporation Service Directive Bulletin No. 0083, dated July 16, 1993.

(b) If the shaft is found with composite-wrapping separation, corrosion, red color residue or cracks during the inspections in paragraph (a) of this AD, remove the shaft from further service and install an airworthy shaft, P/N 28-13140-11 or P/N 28-13104-1.

(c) If main rotor (M/R) vibrations occur that cannot be corrected with track and balance procedures; or, if M/R track and balance procedures are required more than once, replace the shaft with an airworthy shaft, P/N 28-13140-11 or P/N 28-13104-1, before further flight.

(d) Within the next 10 hours' time-in-service, or at the next annual inspection after the effective date of this AD, whichever occurs first, remove the shaft, P/N 28-13183, and install an airworthy shaft, P/N 28-13140-11 or P/N 28-13104-1.

(e) Installation of airworthy shafts, P/N 28-13140-11 or P/N 28-13104-1, constitutes terminating action for the requirements of this AD.

(f) An alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Chicago Aircraft Certification Office, 2300 East Devon Avenue, room 232, Des Plaines, IL 60018. 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.

(g) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the helicopter to a location where the requirements of only paragraphs (a) and (d) of this AD can be accomplished.

(h) The inspection, removal and replacement shall be done in accordance with The Enstrom Helicopter Corporation Service Directive Bulletin No. 0083, dated July 16, 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.

(i) This amendment becomes effective January 28, 1994, to all persons except those persons to whom it was made immediately effective by Priority Letter AD 93-15-10, issued August 3, 1993, which contained the requirements of this amendment.