Airworthiness Directive · Amendment 39-15756 · MD Helicopters, Inc. Model MD900 Helicopters
MD Helicopters, Inc. Model MD900 Helicopters
Superseded. A later AD replaced this one: AD 2008-22-52, AD 2011-22-08. Comply with the one in force.
Model MD900 helicopters with a Vertical Stabilizer Control System (VSCS) adapter tube, part number 500N7218-1, installed, certificated in any category.
This document supersedes AD 2008-18-52 and publishes in the Federal Register an amendment adopting Emergency Airworthiness Directive (AD) 2008-22-53 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 turning ON both Vertical Stabilizer Control System (VSCS) switches and turning OFF the autopilot (AP/SAS) switch; pulling certain AP/SAS circuit breakers; installing a placard near the AP/SAS master switch; installing an airspeed limitation placard on the instrument panel; and making changes to the Rotorcraft Flight Manual (RFM). This AD is prompted by 4 occurrences in which the left VSCS adapter tubes failed on the MD900 helicopters and the vertical stabilizer became uncontrollable, resulting in reduced yaw control of the helicopter. There were no injuries, but in one occurrence, due to the high speed quick yaw, the helicopter lost a window and a door. 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) Turn ON both VSCS switches.
(b) If installed, de-energize the autopilot (AP/SAS) as follows:
(1) Determine if the AP/SAS trim actuators are centered. If the AP/SAS trim actuators are not centered, center them.
(2) After the AP/SAS trim actuators are centered:
(i) Turn the AP/SAS MSTR switch to the OFF position.
(ii) Pull the following AP circuit breakers located on the A601 Essential Bus Circuit Breaker Panel, mounted in the cockpit console, and install a plastic cable tie on each circuit breaker to prevent accidental energizing of the circuit:
(A) AP/SAS CMPTR (CB28),
(B) AP/SAS DISC (CB29), and
(C) AP/SAS ACCEL (CB30).
(3) Install a placard next to the AP Mode Select panel that contains the AP/SAS MSTR switch stating “AP/SAS DEACTIVATED.”
(c) Install a placard on the instrument panel as close as practicable to the airspeed indicator that states:
“AIRSPEED LIMIT 100 KIAS or V NE, WHICHEVER IS LESS. VFR FLIGHT ONLY, AUTOPILOT OFF.”
(d) Make pen and ink changes or insert a copy of this AD into the limitations section of the rotorcraft flight manual (RFM) to revise the limitations as follows: “V NE is limited to 100 KIAS or less as determined by referring to the airspeed V NE placard already installed on the helicopter. VFR Flight Only, Autopilot OFF.”
(e) Make pen and ink changes or insert a copy of this AD into the limitations section of the RFM to revise the emergency procedures as follows: “If you experience an anti-torque system malfunction, turn both VSCS switches to OFF during final approach for a run-on landing.”
Note: MDHI Service Bulletin SB900N-110, dated October 17, 2008, pertains to the subject of this AD.
(f) 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.
(g) Copies of the applicable service information may be obtained from MD Helicopters Inc., Attn: Customer Support Division, 4555 E. McDowell Rd., Mail Stop M615, Mesa, Arizona 85215-9734, telephone 1-800-388-3378, fax 480-346-6813, or on the Web at http://www.mdhelicopters.com.
