Airworthiness Directive · Amendment 39-17484 · Tail rotor drive
Eurocopter Deutschland (Eurocopter) Helicopters
Superseded. A later AD replaced this one: AD 2014-06-51. Comply with the one in force.
This AD applies to Eurocopter Model MBB-BK 117 A-3, MBB-BK 117 A-4, MBB-BK 117 B-1, and MBB-BK 117 C-2 helicopters with a Metro Aviation, Inc. (Metro) vapor-cycle air conditioning kit installed in accordance with Supplemental Type Certificate (STC) No. SH3880SW, certificated in any category.
We are adopting a new airworthiness directive (AD) for Eurocopter Model MBB-BK117 A-3, MBB-BK117 A-4, MBB-BK117 B-1, and MBB- BK117 C-2 helicopters with a Metro Aviation (Metro) vapor-cycle air conditioning kit installed in accordance with Supplemental Type Certificate (STC) No. SH3880SW. This AD requires repetitively inspecting the air conditioning drive pulley (pulley) for looseness and properly installed lockwire, and also requires reinstalling the pulley. This AD is prompted by two reports of the pulley detaching from the rotor brake disc on the tail rotor (T/R) driveshaft. These actions are intended to prevent separation of the pulley, damage to the T/R driveshaft, and subsequent loss of control of the helicopter.
You are responsible for performing each action required by this AD within the specified compliance time.
(1) Before further flight, and thereafter at intervals not exceeding 10 hours time-in-service (TIS), inspect the lockwire securing the pulley mount bolts for proper installation and the pulley for looseness. If the lockwire is damaged or broken, or is not installed in a tightening direction, or if the pulley is loose, remove and inspect the pulley as described in paragraphs (e)(2)(i) and (e)(2)(ii) of this AD.
(2) Within 25 hours TIS:
(i) Remove the pulley from the rotor brake disc and, using a 10X or higher power magnifying glass, inspect the bolts and mounting holes glass for damage or distortion. If there is any damage or distortion, replace the pulley.
(ii) Install the pulley and torque each mount bolt to 90 inch-pounds. After torqueing, determine whether a gap exists among each bolt head, washer, and the mating surface of the rotor brake disc. If there is a gap, replace the pulley.
(iii) Lock wire each pulley mount bolt to its adjacent rotor brake mounting bolt with 0.6 millimeter lockwire.
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.
