AD 90-01-11

90-01-11 BELL HELICOPTER TEXTRON, INC.: Amendment 39-6450. Docket No. 89-ASW-50.

Applicability: Bell Helicopter Textron, Inc., Model 204B helicopters, certificated in any category, with tail rotor gearbox duplex bearing sets, P/N 204-040-424-001, with serial numbers (S/N's) 1 thru 182, MB183 thru MB382, MB442, MB486, MB513, MB518, MB519, MB524, MB530, MB531, MB544, MB545, MB548, MB549, MB551, MB553, MB554, MB561, MB659, MB743, MB744, MB760 thru MB769 and MB927 thru MB936, installed in tail rotor gearbox output quill, P/N 204-040-012-009.

Compliance: Required as indicated, unless already accomplished.

To prevent failure of the tail rotor duplex bearing which could result in loss of tail rotor control and subsequent loss of the helicopter, accomplish the following:

(a) Within the next 100 hours' time in service after the effective date of this AD, remove the tail rotor gearbox duplex bearing set, P/N 204-040-424-001, from service and replace with a serviceablepart before further flight.

(b) In accordance with FAR Sections 21.197 and 21.199, the helicopter may be flown to a base where the requirements of this AD may be accomplished.

(c) An alternate method of compliance or adjustment of the compliance time which provides an acceptable level of safety may be used when approved by the Manager, Rotorcraft Certification Office, ASW-170, Rotorcraft Directorate, FAA, Southwest Region, Fort Worth, Texas.

This amendment (39-6450, AD 90-01-11) becomes effective on February 1, 1990.