AD 2020-04-21 Airworthiness Directives; Bell Helicopter Textron Canada Limited Helicopters

This AD becomes effective March 31, 2020.

A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a currently valid OMB Control Number. The OMB Control Number for this information collection is 2120-0056. Public reporting for this collection of information is estimated to be approximately 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. All responses to this collection of information are mandatory. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to: Information Collection Clearance Officer, Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177-1524.

(1) The Manager, Safety Management Section, Rotorcraft Standards Branch, FAA, may approve AMOCs for this AD. Send your proposal to: Kristi Bradley, Aerospace Engineer, Safety Management Section, Rotorcraft Standards Branch, FAA, 10101 Hillwood Pkwy., Fort Worth, TX 76177; telephone 817-222-5110; email 9-ASW-FTW-AMOC-Requests@faa.gov. (2) For operations conducted under a 14 CFR part 119 operating certificate or sunder 14 CFR part 91, subpart K, the FAA suggests that you notify your principal inspector, or lacking a principal inspector, the manager of the local flight standards district office or certificate holding district office, before operating any aircraft complying with this AD through an AMOC.

(1) Within 10 hours time-in-service, using a light source, flap the inboard and outboard T/R blades to inspect for proper engagement of the inboard and outboard curvic coupling teeth with the inboard and outboard flapping bearing teeth as shown in Figure 2 of Bell Alert Service Bulletin 429-19-45, dated April 16, 2019 (ASB 429-19-45). (i) If the teeth are not properly engaged, before further flight, remove the T/R hub and blade assembly and do the following: Note to paragraph (e)(1)(i) of this AD: Figure 1 of ASB 429-19-45 shows an example of improperly engaged teeth. (A) Inspect the inboard flapping bearing teeth and the curvic coupling teeth that mate to them for a crack, wear, mechanical damage, and corrosion. If there is a crack, wear, mechanical damage, or corrosion on the teeth, before further flight, replace with an airworthy part. (B) Inspect the outboard flapping bearing teeth and the curvic coupling teeth that mate to them for a crack, wear, mechanical damage, and corrosion. If there is a crack, or wear, mechanical damage, or corrosion on the teeth, before further flight, replace with an airworthy part. (C) With the T/R hub and blade assembly installed, perform a rigging check of the directional control system. (ii) If the teeth are properly engaged, before further flight, inspect for axial play between both the inboard and outboard T/R hub and blade assemblies. (A) If there is axial play, remove the T/R hub and blade assembly, and perform the actions required by paragraph (e)(1)(i)(A) through (C) of this AD. (B) If there is no axial play, inspect for play between the teeth of the curvic coupling and both the inboard and outboard flapping bearing teeth by applying a lead/lag force to the inboard and outboard T/R hub and blade assemblies. If there is play, remove the T/R hub and blade assembly, and perform the actions required by paragraph (e)(1)(i)(A) through (C) of this AD. (2) Within 10 days after an inspection that resulted in replacing any part as required by paragraph (e)(1) of this AD, email a description of the inspection results that includes a description of each replaced part to: productsupport@bellflight.com. Include the following information in the email subject line: “ASB 429-19-45,” the helicopter's serial number, and the operator's name.

This AD defines the unsafe condition as an improperly installed curvic coupling of the tail rotor (T/R) hub and blade assembly. This condition could result in loosening of the T/R assembly, which could cause vibration and loss of drive to the outboard T/R blades, and subsequent degraded directional control.