AD 2020-22-19 Requires Initial And Recurring Inspections Of The Main Rotor (M/R) Blade Spindle Cuff

The FAA is adopting a new airworthiness directive (AD) for various restricted category helicopters, originally manufactured by Sikorsky Aircraft Corporation (Sikorsky), Model EH-60A, HH-60L, S-70, S-70A, S-70C, S-70C(M), S-70C(M1), and UH-60A.

This AD requires initial and recurring inspections of the main rotor (M/R) blade spindle cuff for a crack. This AD was prompted by multiple reports of a cracked M/R blade spindle cuff. These actions are intended to prevent an unsafe condition on these products. This AD is effective December 3, 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 various restricted category helicopters, originally manufactured by Sikorsky, Model EH-60A, HH-60L, S-70, S-70A, S-70C, S-70C(M), S-70C(M1), and UH-60A, with an M/R blade spindle cuff part number 70150-09109-041 installed. The NPRM published in the Federal Register on July 9, 2020 (85 FR 41221).

The NPRM was prompted by multiple reports of a cracked M/R blade spindle cuff. In 2008, Sikorsky reported an M/R blade spindle cuff on a Model UH-60A helicopter that cracked across the lower inboard bolt holes. Investigation determined the crack was caused by a non-conforming hole edge break, specifically a burr, introduced during an overhaul at a non-Sikorsky overhaul facility.

Sikorsky issued Sikorsky Safety Advisory No. SSA-S70-08-002, dated December 11, 2008 (SSAS70-08-002), for Black Hawk  Model H-60- and S-70-series helicopters to inform operators of the incident and recommend compliance with Sikorsky's preventative maintenance inspections. The safety advisory also recommended that operators with M/R blades overhauled by a non-Sikorsky repair facility contact that facility to verify whether the hole edge radius requirement was met during the overhaul.

In 2015, the FAA received an additional report of an M/R blade spindle cuff on a military model helicopter that cracked. Investigation from this reporting has revealed no anomalies at the crack initiation site. In each instance, a crack initiated at a bolt hole and spread to either an adjacent bolt hole or to the free edge. Due to design similarity, Model EH-60A, HH-60L, S-70, S-70A, S-70C, S70C(M), S-70C(M1), and UH-60A helicopters are all affected by this unsafe condition.

Accordingly, the NPRM proposed to require initial and recurring inspections of the M/R blade spindle cuff for a crack. The proposed requirements were intended to detect a crack, prevent failure of an M/R blade spindle cuff, loss of an M/R blade, and loss of control of the helicopter.

FMI: www.regulations.gov