AD 2020-25-05 Requires Visual Inspection And NDT Inspection Of The Propeller Hub

The FAA is adopting a new airworthiness directive (AD) for all Hoffmann GmbH & Co. KG (Hoffmann) model HO-V 72 propellers.

This AD was prompted by reports of cracks at different positions on two affected propeller hubs. This AD requires amending the existing aircraft flight manual (AFM) with abnormal propeller vibration instructions. This AD requires visual inspection and non-destructive test (NDT) inspection of the propeller hub and, depending on the results of the inspections, replacement of the propeller hub with a part eligible for installation. This AD also requires replacement of the propeller hub before exceeding 30 years since the date of manufacture or within 30 days after the effective date of this AD, whichever occurs later. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective December 22, 2020.

Supplementary Information: The European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community, has issued EASA AD 2020-0226-E, dated October 16, 2020 (referred to after this as “the MCAI”), to address an unsafe condition for the specified products.

The MCAI states:

• Cracks have been reported at different positions on two affected parts, both installed on Slingsby T67 “Firefly” aeroplanes. One crack was found during scheduled inspection, the other crack during an unscheduled inspection after abnormal vibrations occurred. Both cases are under investigation by Hoffmann Propeller.
• This condition, if not detected and corrected, could lead to in-flight propeller detachment, possibly resulting in damage to the airplane and/or injury to persons on the ground.
• To address this potential unsafe condition, Hoffmann issued the SB [service bulletin], providing applicable instructions.
• For the reasons described above, this [EASA] AD requires inspections of affected parts and, depending on findings, replacement, and introduces a life limit for affected parts. This [EASA] AD also requires, for certain aeroplanes, amendment of the applicable Aircraft Flight Manual (AFM).

You may obtain further information by examining the MCAI in the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-1104

FMI: www.regulations.gov