Airworthiness Directive · Amendment 39-15978 · Vertical stabilizer, attach fittings
Bell Helicopter Textron Canada Model 427 Helicopters
This AD applies to Model 427 helicopters, serial numbers 56001 through 56057, 58001, and 58002, certificated in any category.
We are adopting a new airworthiness directive (AD) for Bell Helicopter Textron Canada (BHTC) Model 427 helicopters. This AD results from mandatory continuing airworthiness information (MCAI) originated by the aviation authority of Canada to identify and correct an unsafe condition on an aviation product. Transport Canada, the aviation authority of Canada, with which we have a bilateral agreement, states that it has been determined that the existing hardware connecting the vertical fin to the tail rotor gearbox needs to be upgraded to prevent the vertical fin from becoming loose. BHTC has received reports of loose vertical fins discovered during inspections. Investigation revealed that the current vertical fin attachment hardware may not provide adequate clamp-up. If not corrected, the vertical fin could become loose and cause vibration, which could lead to subsequent loss of control of the helicopter. This AD requires actions that are intended to address this unsafe condition.
Within the next 150 hours time-in-service, unless already done, do the following:
(1) Remove the vertical fin and visually inspect the inboard and outboard surfaces of the vertical fin where it attaches to the tail rotor gearbox support for a crack, an elongated bolt hole, fretting, distortion and corrosion.
(2) Visually inspect the tail rotor gearbox support attachment legs for a crack, fretting and corrosion.
(f) If a crack, elongated bolt hole, fretting, distortion or corrosion is detected, repair or replace the part with an airworthy part before further flight.
(g) Reinstall the vertical fin.
This AD differs from the MCAI AD as follows:
(1) We do not require compliance “no later than November 27, 2007”, because that date has passed.
(2) We refer to the compliance time as “hours time-in-service” rather than “air time hours.”
(i) Alternative Methods of Compliance (AMOCs): The Manager, Safety Management Group, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Sharon Miles, Aviation Safety Engineer, FAA, Rotorcraft Directorate, Regulations and Guidance Group, 2601 Meacham Blvd., Fort Worth, Texas 76137, telephone (817) 222-5122, fax (817) 222-5961.
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.
