AD 2001-25-02 Airworthiness Directives; Enstrom Helicopter Corporation Model TH-28 and 480 Helicopters

Makes named: enstrom. Models named: TH-28, 480. Read the applicability below — it usually turns on serial or part numbers too.

Model TH-28 and 480 helicopters, with upper hub plate, part number (P/N) 28-14280-1, and lower hub plate, P/N 28-14281-1, installed, 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 (c) 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.

Required as indicated, unless accomplished previously. To prevent failure of a hub plate, loss of control of the main rotor, and subsequent loss of control of the helicopter, accomplish the following: (a) Within 30 days after the effective date of this AD, for upper hub plate, P/N 28-14280-1, and for lower hub plate, P/N 28-14281-1, create a component history card or equivalent record, and determine the total hours time-in-service (TIS). Thereafter, record the hours TIS for each hub plate and replace each hub plate having 5000 or more hours TIS as follows: (1) Install hub plates, P/N 28-14280-3 and 28-14281-3, on helicopters with main rotor damper, P/N 28-14375-8. (2) Install hub plates, P/N 28-14280-5 and 28-14281-5, on helicopters with main rotor damper, P/N 28-14375-10. (b) This AD revises the Limitations section of the applicable maintenance manual by establishing a life limit of 5000 hours TIS for the upper hub plate, P/N 28-14280-1, and for the lower hub plate, P/N 28-14281-1. (c) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Chicago Aircraft Certification Office (ACO), 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 ACO. Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Chicago ACO. (d) Special flight permits may be issued in accordance with 14 CFR 21.197 and 21.199 to operate the helicopter to a location where the requirements of this AD can be accomplished. (e) This amendment becomes effective on January 15, 2002. Issued in Fort Worth, Texas, on November 30, 2001. David A. Downey, Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 01-30499 Filed 12-10-01; 8:45 am] BILLING CODE 4910-13-U