AD 2020-18-20 Prompted By Reports Of Abrasion Strips Departing The Main Rotor (MR) Blade In-Flight

The FAA is adopting a new airworthiness directive (AD) for certain MD Helicopters Inc. (MDHI) Model 369A, 369D, 369E, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters.

This AD was prompted by reports of abrasion strips departing the main rotor (MR) blade in-flight. This AD requires tap inspecting each MR blade leading edge abrasion strip. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective October 28, 2020.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to MDHI Model 369A, 369D, 369E, 369FF, 369H, 369HE, 369HM, 369HS, 500N, and 600N helicopters with a MR blade part number (P/N) 500P2100-105, P/N 500P2100-305, P/N 500P2300-505, P/N 369D21120-505, P/N 369D21121-505, or P/N 369D21123-505 with a 1.25 inch chord length nickel abrasion strip (abrasion strip) manufactured or installed by Helicopter Technology Company, LLC (HTC), or where the manufacturer of the abrasion strip is unknown, except if the abrasion strip has accumulated 700 or more hours time-in-service (TIS). The NPRM published in the Federal Register on May 14, 2020 (85 FR 28895).

The NPRM was prompted by reports of leading edge abrasion strips manufactured by HTC departing the MR blades during flight. An investigation determined that the abrasion strips were manufactured from electroformed nickel, have a chord length of 1.25 inch, and are delaminating from the MR blade before departing from the helicopter. HTC has determined that a repetitive tap inspection of the abrasion strips should be performed on all blades with abrasion strips that have less than 700 hours TIS to detect any voids, including blistering, bubbling, or lifting of the abrasion strip.

Identical looking electroformed nickel abrasion strips with a chord length of 1.25 inch manufactured by other repair stations have not departed in flight and therefore were not proposed as the subject of this AD.

To address this unsafe condition, the NPRM proposed to require tap inspecting the abrasion strip within 10 hours TIS and thereafter before the first flight of each day until the abrasion strip has accumulated 700 or more hours TIS since installation.

FMI: www.regulations.gov