Airworthiness Directive · Amendment 39-19031 · Rotorcraft flight control
Sikorsky Aircraft Corporation Helicopters
This AD applies to Model S-76A, S-76B, S-76C, and S-76D helicopters, serial numbers up to and including 761075, with a main rotor (M/R) servo pushrod (pushrod) assembly part number (P/N) 76400-00034-059, 76400-00014-074, 76400-00014-076, or 76400-00014-077 installed, certificated in any category.
Note 1 to paragraph (a) of this AD: M/R pushrod P/N 76400-00034-059 is included in the Applicability section of AD 2015-19-51, Amendment 39-18300 (80 FR 65128, October 26, 2015). This AD does not affect AD 2015-19-51.
We are adopting a new airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-76A, S-76B, S-76C, and S-76D helicopters. This AD requires inspecting the main rotor (M/R) servo pushrod (pushrod) assembly and applying slippage marks. This AD was prompted by an accident of a Sikorsky Model S-76C helicopter caused by a failed pushrod assembly. The actions of this AD are intended to prevent an unsafe condition on these products.
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.
Within 300 hours time-in-service:
(1) Inspect the control rod of each pushrod assembly (control rod) to determine whether 0.020 inch diameter lockwire can pass through the inspection hole.
(i) If the lockwire passes through the inspection hole, before further flight, replace the pushrod assembly.
(ii) If the lockwire does not pass through the inspection hole, inspect the jamnut to determine whether it is seated against the control rod and whether it can be turned with finger pressure.
(A) If the jamnut is not seated against the control rod or can be turned with finger pressure, before further flight, replace the pushrod assembly.
(B) If the jamnut is seated against the control rod and cannot be turned with finger pressure, using a pushrod tool, apply 140 inch-pounds of torque to the jamnut.
(2) Apply two slippage marks across each control rod and jamnut as follows:
(i) Clean the area where a slippage mark is to be applied.
(ii) Apply two slippage marks across the control rod and jamnut, parallel and on opposite sides of each other. Each slippage mark must extend at least 0.5 inch onto the control rod and must not cover the inspection hole. Figure 1 (Sheet 2) of Sikorsky S-76 Helicopter Alert Service Bulletin 76-67-58, Basic Issue, dated November 19, 2015, illustrates a slippage mark across a control rod and jamnut.
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.
