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Federal Register / Vol. 86, No. 126 / Tuesday, July 6, 2021 / Proposed Rules Actions Since AD 20202505 Was Issued Since the FAA issued AD 202025
05, the European Union Aviation Safety Agency EASA, which is the Technical Agent for the Member States of the European Community, has issued EASA
AD 20200226R1, dated March 31, 2021
referred to after this as the MCAI, to address the unsafe condition on these products. The MCAI states:

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.
FAA20210546.
In addition, Hoffmann issued Service Bulletin SB E53, Rev. D, dated February 18, 2021, to no longer specify that the propeller hub be replaced before exceeding 30 years since the date of manufacture.

Proposed AD Requirements in This NPRM

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, providing applicable instructions.
For the reasons described above, EASA
issued Emergency AD 20200226E to require inspections of affected parts and, depending on findings, replacement, and introduces a life limit for affected parts. That EASA AD also required, for certain aeroplanes, amendment of the applicable Aircraft Flight Manual AFM.
Since that EASA AD was issued, recent analyses of inspection results showed that the life limit of 30 years is no longer necessary and Hoffmann Propeller issued Revision D of the SB accordingly.
This EASA AD is revised to delete the life limit and to introduce a clarification for corrective actions during overhaul in paragraph 6 of EASA AD.

FAAs Determination This product has been approved by EASA and is approved for operation in the United States. Pursuant to the FAAs bilateral agreement with the European Community, EASA has notified the FAA
of the unsafe condition described in the MCAI and service information. The FAA is issuing this NPRM because the agency evaluated all the relevant information provided by EASA and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.

Differences Between the Proposed AD
and MCAI or Service Information
Related Service Information Under 1
CFR Part 51
The FAA reviewed Hoffmann Propeller GmbH & Co. KG Service Bulletin SB E53, Rev. D, dated February 18, 2021. This service information specifies procedures for visual and NDT
inspections of the propeller hub for cracks. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in ADDRESSES.

This proposed AD would retain certain requirements of AD 20202505.
This proposed AD would no longer require that the propeller hub be replaced before exceeding 30 years since the date of manufacture or within 30
days after the effective date of AD 2020
2505.

EASA AD 20200226R1, dated March 31, 2021, applies to Hoffmann HOV 72
propellers with propeller hub HOV 72
that have been used or are expected to be used for aerobatic maneuvers. This proposed AD applies to all Hoffmann model HOV 72
propellers regardless of their use.
Hoffmann Propeller GmbH & Co. KG
Service Bulletin SB E53, Rev. D, dated February 18, 2021, specifies that operators must send any propeller found with a crack to Hoffmann for investigation. The service bulletin also specifies that operators must report any propeller with cracked hubs to Hoffmann. This proposed AD does not mandate sending the propeller or information to Hoffmann.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 35
propellers installed on airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this proposed AD:

ESTIMATED COSTS
Action
Labor cost
Amend AFM
Visually inspect propeller hub
NDT inspect propeller hub

1 work-hour $85 per hour = $85
1 work-hour $85 per hour = $85
8 work-hours $85 per hour = $680

The FAA estimates the following costs to do any necessary replacement that would be required based on the
Cost per product
Parts cost
results of the proposed inspection. The agency has no way of determining the
$0
0 0

$85
85
680

Cost on U.S.
operators $2,975
2,975
23,800

number of aircraft that might need this replacement:

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ON-CONDITION COSTS
Action
Labor cost
Replace propeller hub

5 work-hours $85 per hour = $425

Authority for This Rulemaking Title 49 of the United States Code specifies the FAAs authority to issue rules on aviation safety. Subtitle I,
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Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agencys authority.

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Parts cost $1,600

Cost per product $2,025

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, General requirements. Under that section, Congress charges the FAA

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