Airworthiness Directive · Amendment 39-17322 · Rotorcraft servo system
Bell Helicopter Textron Canada Limited (Bell) Helicopters
This AD applies to Bell Model 206L, 206L-1, and 206L-3 helicopters, all serial numbers (S/N), and Model 206L-4 helicopters, S/Ns 52001 through 52430, with a hydraulic servo actuator assembly (servo), part number (P/N) 206-076-062-103, installed, certificated in any category.
We are adopting a new airworthiness directive (AD) for Bell Model 206L, 206L-1, 206L-3, and 206L-4 helicopters. This AD requires inspecting certain hydraulic servo actuator assemblies (servo) for a loose nut, shaft, and clevis assembly, modifying or replacing the servo as necessary, and reidentifying the servo. This AD is prompted by an investigation after an accident and the determination that there was a loose connection due to improper lock washer installation. These actions are intended to detect loose or misaligned parts of the servo to prevent failure of the servo and subsequent loss of control of the helicopter.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
Before further flight, for each servo:
(1) Retract the boot as depicted in Figure 1 of Bell Alert Service Bulletin (ASB) No. 206L-11-169, Revision B, dated August 29, 2011 (ASB).
(2) Applying only hand pressure, determine whether the nut, shaft, and clevis assembly turn independently from each other.
(i) If the shaft turns independently of the nut or the clevis assembly, before further flight, replace the servo with an airworthy servo.
(ii) If the shaft does not turn independently of the nut or the clevis assembly, inspect to determine whether at least one tab of the lock washer (tab) is aligned with and bent flush against a flat surface of the nut and whether at least one tab is aligned with and bent flush against a flat surface of the clevis assembly.
(A) If at least one tab is aligned with and bent flush against a nut flat surface and at least one tab is aligned with and bent flush against a flat surface of the clevis assembly, for any tab that is not bent flush against either a flat surface of the nut or clevis assembly, bend it flush against a flat surface.
(B) If at least one tab is not aligned with and bent flush against a nut flat surface and at least one tab is not aligned with and bent flush against a flat surface of the clevis assembly, before further flight, replace the servo with an airworthy servo.
(3) Re-identify the servo by metal-impression stamping or by vibro-etching the letter “V” at the end of P/N 206-076-062-103V on the identification plate.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
