Airworthiness Directive · Amendment 39-15752 · MD Helicopters, Inc. Model 500N and 600N Helicopters
MD Helicopters, Inc. Model 500N and 600N Helicopters
Model 500N and 600N helicopters, with a Yaw Stability Augmentation System (YSAS) adapter tube, part number 500N7218-1, installed, certificated in any category. Adapter tubes that have a production date code stamp are not included in the applicability of this AD.
This document supersedes AD 2008-18-52 and publishes in the Federal Register an amendment adopting Emergency Airworthiness Directive (AD) 2008-22-52 which was sent previously to all known U.S. owners and operators of MD Helicopters, Inc. (MDHI) Model 500N and 600N helicopters by individual letters. This AD requires turning OFF the Yaw Stability Augmentation System (YSAS); installing a placard that limits airspeed to 100 KTS or V<INF>NE</INF>, whichever is less; and revising the limitations section of the Rotorcraft Flight Manual (RFM) to reflect that limitation. Finally, replacing the adapter tubes with airworthy adapter tubes that have a production date code stamp is required. This AD is prompted by several occurrences of failed adapter tubes on the Model MD900 helicopter which uses the same adapter tubes. 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) Before further flight:
(1) Turn OFF the YSAS switch.
(2) Install a placard on the instrument panel as close as practicable to the airspeed indicator that states:
“YSAS SYSTEM IS OFF. AIRSPEED LIMIT 100 KIAS or V NE, WHICHEVER IS LESS.”
Note: MDHI Service Bulletin SB500N-040R1/SB600N-047R1, dated August 27, 2008, and maintenance manual CSP-HMI-3, Section 96-00-00, pertain to the subject of this AD.
(3) Make pen and ink changes or place a copy of this AD in 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.”
(b) Within 45 days, replace each affected adapter tube with an airworthy adapter tube that has a production date code stamp. This replacement is terminating action for the requirements of this AD. Once this replacement has been done, remove the placards, remove the airspeed restriction revisions that were made to the RFM, and return the YSAS system to its normal position.
(c) 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.
(d) 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.
