Airworthiness Directive · Amendment 39-13870 · MD Helicopters, Inc. Model MD900 Helicopters
MD Helicopters, Inc. Model MD900 Helicopters
Superseded. A later AD replaced this one: AD 2006-18-01. Comply with the one in force.
Model MD900 helicopters, with a Notar fan system that has a tension-torsion (TT) strap, part number (P/N) 900R3442009-103, 900R6442009-103, 900R3442009-101, or 500N5311-5, installed, certificated in any category.
This amendment adopts a new airworthiness directive (AD) for the MD Helicopters, Inc. (MDHI) Model MD900 helicopters. This action requires reducing the life limit of certain Notar fan system tension- torsion (TT) straps. This action also requires, at a specified time interval, removing each affected TT strap from the helicopter, doing a visual and x-ray inspection, and replacing any unairworthy part before further flight. Reporting the discovery of any unairworthy TT strap is also required. This amendment is prompted by two recent in-flight TT strap failures. The actions specified in this AD are intended to prevent failure of a TT strap resulting in loss of directional control and subsequent loss of control of the helicopter.
To prevent failure of a TT strap in the Notar fan system, which could result in loss of directional control and subsequent loss of control of the helicopter, accomplish the following:
(a) Before further flight, for TT straps, P/N 900R3442009-103 and 900R6442009-103, reduce the life limit from 3034 to 2500 hours time-in-service (TIS).
(b) Within 10 hours TIS, for any TT strap that has accumulated 1190 or more hours TIS, remove the TT strap from the helicopter and do a visual and x-ray inspection in accordance with the Inspection Instructions, paragraph 2.B.(1). through (5). and Figures 1 and 2 of MD Helicopters Service Bulletin SB900-095, dated November 3, 2004 (SB). Replace any unairworthy part before further flight.
(c) Before the TT strap accumulates 1200 hours TIS, for any TT strap with less than 1190 hours TIS, remove the TT strap from the helicopter and do a visual and x-ray inspection in accordance with the Inspection Instructions, paragraph 2.B.(1). through (5). and Figures 1 and 2 of the SB. Replace any unairworthy part before further flight.
(d) The x-ray inspection of the TT strap must be performed by a Level II or higher x-ray technician who is qualified under the guidelines established by MIL-STD-410E, ATA Specification 105, AIA-NAS-410, or an FAA-accepted equivalent for qualification standards.
(e) Within 7 days, for any TT strap that you find unairworthy, report the helicopter serial number (S/N), the TT strap P/N and S/N, the total hours TIS on the TT strap, and a description of the part condition rendering it unairworthy. Report the information to Roger Durbin, Aviation Safety Engineer, FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5233, fax (562) 627-5210.
(f) Information collection requirements contained in this AD have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.
(g) This AD revises the Airworthiness Limitations section of the maintenance manual by reducing the life limit of the TT strap, P/N 900R3442009-103 and 900R6442009-103, from 3034 hours TIS to 2500 hours TIS.
(h) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Los Angeles Aircraft Certification, Transport Airplane Directorate, FAA, for information about previously approved alternative methods of compliance.
