Bell Helicopter Textron 412 Series Helicopters
AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/BELL 412/39 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
AD/BELL 412/39
Amdt 1
Tail Rotor Yoke and Tail Rotor Flapping Stop/Indicator
8/2001
Applicability: All Model 412, 412CF, and 412EP helicopters, with tail rotor yoke assembly, part number 212-011-702-all dash numbers, installed.
Requirement: 1. Review the historical records of the yoke assembly, for any static or dynamic overload damage that could have imposed a bending load on the yoke. The damage may not have required replacing the yoke assembly; for example, an incident in which a damaged tail rotor blade was replaced due to a blade strike. If the records indicate that overload damage may have occurred, replace the yoke with a serviceable yoke.
2. (a) Install a Never Exceed Velocity (Vne) red line at 120 knots indicated airspeed (KIAS) on the pilot and copilot airspeed indicators using red tape or paint, and a slippage indicator on the instrument case and glass.
(b) Install a placard made of material that is not easily erased, or disfigured, or obscured on the instrument panel in clear view of the pilot and copilot:
“Observe temporary Maximum Never Exceed (Vne) airspeed red line (marked at 120 knots indicated airspeed (KIAS). Vne is 20 KIAS less than the value presented on the airspeed limitation placard for each ambient condition”.
(c) A Rotorcraft Flight Manual Temporary Revision, dated 16 August 1996 is required.
3. (a) Remove rotor yoke assembly, part number 212-011-702-all dash numbers, and replace it with a serviceable yoke assembly, part number 212-011-702-all dash numbers, with zero hours time in service, or an airworthy yoke that has passed a one-time x-ray diffraction inspection in accordance with Bell Helicopter Textron Alert Service Bulletin (ASB) 412-96-89 Revision A, dated 17 October 1997, or ASB 412CF-96-01, dated 3 September 1996, as applicable.
(b) Install a serviceable tail rotor flapping stop, part number 212-011-713-103.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
(c) If requirements 3(a) and 3(b) are accomplished in accordance with this Directive, remove the 120 KIAS redline from the pilot and copilot airspeed indicators; remove the Vne airspeed restriction placard; and remove the Bell Helicopter Textron Temporary Revision, dated 16 August 1996, from the Rotorcraft Flight Manual.
4. Inspect the yoke assembly and tail rotor flapping stop in accordance with Part III, Recurring 25-Hour Special Inspection and Conditional Inspection Requirement, of Bell Helicopter Textron ASB 412-96-89, Revision A, dated 17 October 1996, or ASB 412CF-96-01, dated 3 September 1996, as applicable.
Note: FAA AD 2001-09-11 Amdt 39-12217 refers.
Compliance: 1. Unless already accomplished, before further flight after 29 April 1998.
2. Unless Requirement 3 is already accomplished, before further flight after 29 April 1998.
3. Unless already accomplished, before 30 Oct 1998.
4. After accomplishment of Requirement 3; at intervals not to exceed 25 hours time in service.
The compliance times of the original issue of this Directive remain unchanged by this issue.
This amendment becomes effective on 9 August 2001.
Background: The actions required by the FAA are prompted by laboratory tests and engineering analysis that indicated that the yoke assembly is susceptible to fatigue damage due to unforeseen static and dynamic loading of the tail rotor against the original flapping stop. Failure of the yoke could result in loss of the tail rotor and subsequent loss of control of the helicopter.
Amendment 1 is issued in response to a new FAA AD which expands applicability to all Model 412 helicopters. This action was prompted by the determination that the unsafe condition exists on all Model 412 helicopters, regardless of serial number.
The original issue of this Airworthiness Directive became effective on 29 April 1998.
David Alan Villiers
Delegate of the Civil Aviation Safety Authority 3 July 2001
The above AD is notified in the Commonwealth of Australia Gazette on 11 July 2001.