Airworthiness Directive · Amendment 39-18835 · Tail rotor drive system
Airbus Helicopters
This AD applies to Airbus Helicopters Model EC120B helicopters with an Air Comm Corporation (Air Comm) air conditioning kit installed in accordance with supplemental type certificate (STC) No. SR00491DE, where the compressor is driven by a pulley installed aft of the rotor brake, certificated in any category.
We are superseding Emergency Airworthiness Directive (Emergency AD) 2015-24-51 for Airbus Helicopters Model EC120B. Emergency AD 2015-24-51 required inspections of the air conditioning system. This supersedure revises the applicability, some of the terminology, and the inspection requirements. This AD was prompted by a report of an abnormal noise during flight of a Model EC120B helicopter that resulted in a precautionary landing. We are issuing this AD 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.
(1) Before further flight, and at intervals not to exceed 25 hours time-in-service, disassemble the tail rotor drive system and remove the pulley.
(i) Visually inspect the pulley splines for wear. If any splines are not straight, contain any inconsistent cross-sections end-to-end, or contain any localized material deformation or any material loss, replace the pulley before further flight.
Note 1 to paragraph (f)(1)(i) of this AD: End-to-end (fore-and-aft) movement witness marks and polishing are acceptable as the pulley is allowed to slip fore and aft on the wheel per its intended function.
(ii) Inspect the exposed portion of each wheel spline for cracking, scoring, metal pick-up, and wear by using Figure 1 to paragraph (f)(1)(ii) of this AD. To inspect for wear, position two 3 mm (0.118 inch) rods in all diametrically opposed splines and measure to determine whether there is a minimum of 37.3 mm (1.47 inches) across the outside diameter of the rods. If there is any cracking, scoring or metal pick-up, or if a measurement is less than 37.3 mm, replace the wheel.
(2) Within 10 days after completing the initial inspection, report the information requested in Appendix 1 to this AD by mail to the Denver Aircraft Certification Office, FAA, Technical Operations Center, 26805 East 68th Avenue, Room 214, Denver, CO 80249, attn. Richard R. Thomas; by fax to (303) 342-1088; or by email to richard.r.thomas@faa.gov.
(3) Replacing the Air Comm pulley with Airbus Helicopters output flange part number C632A2158201 constitutes terminating action for this AD.
