DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0546; Project Identifier MCAI-2021-00387-P;
Amendment 39-21815; AD 2021-23-17]
RIN 2120-AA64

Airworthiness Directives; Hoffmann GmbH & Co. KG Propellers

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2020-25-05
for all Hoffmann GmbH & Co. KG (Hoffmann) model HO-V 72 propellers. AD
2020-25-05 required amending the existing aircraft flight manual (AFM)
with abnormal propeller vibration instructions. AD 2020-25-05 also
required 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.
AD 2020-25-05 also required replacement of the propeller hub before
exceeding 30 years since the date of manufacture. This AD was prompted
by reports of cracks at different positions on two affected propeller
hubs and subsequent manufacturer revision of the service information,
which showed that the 30-year life limit of the propeller hub is no
longer needed. This AD requires amending the existing AFM by inserting
abnormal propeller vibration instructions, visual inspection and 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. The FAA is issuing this AD to address the unsafe
condition on these products.

DATES: This AD is effective January 10, 2022.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of January 10,
2022.

ADDRESSES: For service information identified in this final rule,
contact Hoffmann GmbH & Co. KG, K[uuml]pferlingstrasse 9, 83022,
Rosenheim, Germany; phone: +49 0 8031 1878 0; email: info@hoffmann-prop.com;
website: prop.com">https://hoffmann-prop.com. You may view this service
information at the FAA, Airworthiness Products Section, Operational
Safety Branch, 1200 District Avenue, Burlington, MA 01803. For
information on the availability of this material at the FAA, call (781)
238-7759. It is also available at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0546.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0546; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains this AD, the mandatory
continuing airworthiness information (MCAI), any comments received, and
other information. The address for Docket Operations is Document
Operations, U.S. Department of Transportation, Docket Operations, M-30,
West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE,
Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Michael Schwetz, Aviation Safety
Engineer, Boston ACO Branch, FAA, 1200 District Avenue, Burlington, MA
01803; phone: (781) 238-7761; fax: (781) 238-7199; email:
michael.schwetz@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 2020-25-05, Amendment 39-21347 (85 FR
78702, December 7, 2020), (AD 2020-25-05). AD 2020-25-05 applied to all
Hoffmann model HO-V 72 propellers. The NPRM published in the Federal
Register on July 6, 2021 (86 FR 35416). The NPRM was prompted by
reports of cracks at different positions on two affected propeller hubs
and subsequent manufacturer revision of the service information, which
showed that the 30-year life limit of the propeller hub is no longer
needed. In the NPRM, the FAA proposed to continue to require amending
the existing AFM with abnormal propeller vibration instructions. In the
NPRM, the FAA also proposed to continue to require visual inspection
and 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. The FAA is issuing this AD to address the
unsafe condition on these products.
The European Union Aviation Safety Agency (EASA), which is the
Technical Agent for the Member States of the European Community, has
issued EASA AD 2020-0226R1, dated March 31, 2021
(referred to after this as ``the MCAI''), to address the unsafe
condition on these 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, providing applicable instructions.
For the reasons described above, EASA issued Emergency AD 2020-
0226-E 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 action(s) during overhaul
in paragraph (6) [of EASA AD].

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-2021-0546.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from one individual commenter. The
individual commenter supported the NPRM without change.

Clarification of Required Actions

The FAA revised paragraph (g), Required Actions, of this AD by
clarifying that the propeller hub must be replaced with a part eligible
for installation if any crack is detected during an overhaul
inspection.

Conclusion

The FAA reviewed the relevant data, considered the comment
received, and determined that air safety requires adopting the AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. This AD is adopted as proposed in the
NPRM.

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. The service bulletin describes
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.

Costs of Compliance

The FAA estimates that this AD affects 35 propellers installed on
airplanes of U.S. registry.
The FAA estimates the following costs to comply with this AD:

Estimated Costs

The FAA estimates the following costs to do any necessary
replacements that would be required based on the results of the
mandated inspections. The FAA has no way of determining the number of
aircraft that might need this replacement:

On-Condition Costs

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, Section 106, describes the
authority of the FAA Administrator. Subtitle VII, Aviation Programs,
describes in more detail the scope of the Agency's authority.
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 with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.

Regulatory Findings

This AD will not have federalism implications under Executive Order
13132. This AD will not have a substantial direct effect on the States,
on the relationship between the national government and the States, or
on the distribution of power and responsibilities among the various
levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by:

a. Removing Airworthiness Directive 2020-25-05, Amendment 39-21347 (85
FR 78702, December 7, 2020); and

b. Adding the following new airworthiness directive: