Airworthiness Directive · Amendment 39-15755 · MD Helicopters, Inc. Model MD900 Helicopters
MD Helicopters, Inc. Model MD900 Helicopters
Model MD900 helicopters, serial numbers 900-00008 through 900-00128, with part number (P/N) 900C3010045-105 forward directional control cable (control cable), P/N 900C2010582-103 rotating cone control rod, and P/N 9000F2318021 (all dash numbers) tailboom assembly, installed, certificated in any category.
This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2008-17-51, which was sent previously to all known U.S. owners and operators of MD Helicopters, Inc. (MDHI) Model MD900 helicopters by individual letters. This AD requires, before further flight, fluorescent magnetic particle inspecting the aft threads of the forward directional control cable (control cable) for a crack and replacing the control cable with an airworthy part if you find a crack. If you do not find a crack, this AD requires that you demagnetize the cable threads until you reach a certain gauss level. This AD also requires visually inspecting the aft cable attach bracket for a crack and for interference with movement of the control cable or for deformation of the aft cable attach bracket. If a crack or interference with movement of the control cable or deformation of the aft cable attach bracket exists, this AD requires replacing the bracket with an airworthy part. This AD also requires modifying the control cable conduit and the rotating cone control rod and identifying the rotating cone control rod with a certain part number. This amendment is prompted by three reports of in-flight failure of the control cable and loss of yaw control resulting in emergency landings and subsequent damage to the helicopter. The actions specified by this AD are intended to prevent loss of yaw control and subsequent loss of control of the helicopter.
To prevent loss of yaw control and subsequent loss of control of the helicopter, do the following:
(a) Remove the rotating cone, the thruster extension, the rotating cone control rod, and the NAS1193K4CP lock device (2 parts). Do not reinstall the lock device. Use your hand and turn the telescopic part on the aft end of the control cable until it is fully forward on the control cable.
Note: The MDHI maintenance manuals CSP-900RMM-2, Sections 67-20-00, 29-00-00, 53-40-00; CSP-SPM, Section 20-30-00; and CSP-900IPL-4 Illustrated Parts pertain to the subject of this AD.
(b) Do a fluorescent magnetic particle inspection for a crack in the aft threads of the control cable as depicted in Figure 2 and by following MD Helicopters, Inc. (MDHI) Service Bulletin SB900-108R1, dated August 13, 2008, Section 2, Accomplishment Instructions (SB), paragraphs (5)(a) through 5(j). The inspection must be done by an inspector qualified under the guidelines established by MIL-STD-410E, ATA Specification 105, AIA-NAS-410, or an FAA-accepted equivalent for qualification standards of NDT Inspection/Evaluation Personnel. The inspector that accepts or rejects the inspected part must be certified to a Non-Destructive Testing (NDT) UT minimum Level II. The part must be inspected to the inspection facilities written procedure approved by a person certified to a Level III. For the magnetic particle examination process and qualifications, follow the American Society for Testing and Material (ASTM) E 1444-93 ε1.
(1) If you find a crack, replace the control cable with an airworthy part.
(2) If you do not find a crack, demagnetize the cable threads by following paragraphs (6)(a) or (6)(b) of the SB until you reach a gauss level of +/−3.
(c) Visually inspect the aft cable attach bracket, depicted in Figure 3 of the SB, for a crack. Inspect for interference with the movement of the control cable or for deformation of the aft cable attach bracket by following paragraphs (9)(a) through (9)(c) of the SB. If a crack or interference with the movement of the control cable or deformation of the aft cable attach bracket exists, replace the bracket with an airworthy part.
(d) Cut and modify the aft end of the control cable conduit as depicted in Figure 4 of the SB by following paragraphs (10)(a) through (10)(g) of the SB.
(e) Modify the rotating cone control rod by drilling lock wire holes as depicted in Figure 5 of the SB by following paragraphs (11)(a) through (11)(g) of the SB. Using permanent ink, mark the rotating cone control rod with “900C2010582-105.”
(f) Inspect the control cable for proper adjustment by following paragraphs (12)(a) through (12)(c), of the SB.
(g) Install the rotating cone control rod as depicted in Figure 6 of the SB by following paragraphs (13)(a) through (13)(c) of the SB. Make sure the control cable threads are past the witness hole in the rotating cone control rod.
(h) Install the thruster extension.
(i) Install the rotating cone. If you adjust the control cable at the attach brackets, inspect for interference with the movement of the control cable or for deformation of the aft cable attach bracket by following paragraph (15) of the SB. If interference with the movement of the control cable or deformation of the aft cable attach bracket exists, replace the bracket with an airworthy part.
(j) Rerig the antitorque directional control system.
(k) 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 Manager, Los Angeles Aircraft Certification Office, FAA, ATTN: Eric D. Schrieber, Aviation Safety Engineer, Airframe Branch, 3960 Paramount Blvd., Lakewood, California 90712, telephone 562-627-5348, fax 562-627-5210, for information about previously approved alternative methods of compliance.
