DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0980; Project Identifier MCAI-2022-00448-P;
Amendment 39-22212; AD 2022-21-13]
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) 2021-23-17
for all Hoffmann GmbH & Co. KG (Hoffmann) model HO-V 72 propellers. AD
2021-23-17 required amending the existing aircraft flight manual (AFM)
by inserting abnormal propeller vibration instructions, 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. Since the FAA
issued AD 2021-23-17, further investigation by the manufacturer
revealed that cracks found on propeller hubs likely resulted from
propeller blade retention nuts that were not tightened using published
service information during blade installation. This AD is prompted by
reports of cracks at different positions on two affected propeller
hubs. This AD retains the required actions of AD 2021-23-17. This AD
also requires a maintenance records review and, depending on the
results of the maintenance records review, tightening of each propeller
blade retention nut to specific torque values. Depending on the results
of the maintenance records review, this AD requires physically
inspecting the propeller blade for shake. If any axial play is detected
during the performance of the inspection, this AD requires the removal
of the propeller from service and the performance of an NDT inspection
of the propeller hub, and depending on the NDT inspection results,
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 December 6, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of December 6,
2022.
The Director of the Federal Register approved the incorporation by
reference of a certain other publication listed in this AD as of
January 10, 2022 (86 FR 68905, December 6, 2021).

ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2022-0980; 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 final rule, the mandatory continuing airworthiness
information (MCAI), any comments received, and other information. The
address for Docket Operations is U.S. Department of Transportation,
Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200
New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
For Hoffmann service information identified in this final
rule, contact Hoffmann GmbH & Co. KG, Kupferlingstrasse 9, 83022,
Rosenheim, Germany; phone: +49 0 8031 1878 0; email: info@hoffmann-prop.com;
website: 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 (817) 222-5110. It is
also available at regulations.gov under Docket No. FAA-2022-0980.

FOR FURTHER INFORMATION CONTACT: Michael Schwetz, Aviation Safety
Engineer, Boston ACO Branch, FAA, 1200 District Avenue, Burlington, MA
01803; phone: (781) 238-7761; email: 9-AVS-AIR-BACO-COS@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 2021-23-17, Amendment 39-21815 (86 FR
68905, December 6, 2021) (AD 2021-23-17). AD 2021-23-17 applied to all
Hoffmann GmbH & Co. KG model HO-V 72 propellers. AD 2021-23-17 required
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 issued AD
2021-23-17 to prevent failure of the propeller hub.
The NPRM published in the Federal Register on August 01, 2022 (87
FR 46903). The NPRM was prompted by EASA AD 2022-0061, dated April 4,
2022 (referred to after this as ``the MCAI''), issued by the European
Union Aviation Safety Agency (EASA), which is the Technical Agent for the
Member States of the European Union. 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.
Subsequent investigation determined that improper tightening of
blade nuts has caused or contributed to those events.
This condition, if not detected and corrected, could lead to in-
flight propeller detachment, possibly resulting in damage to the
aeroplane and/or injury to persons on the ground.
To address this potential unsafe condition, Hoffmann Propeller
issued the SB, providing applicable instructions, and EASA issued
Emergency AD 2020-0226-E (later revised [to EASA AD 2020-0226R1]) to
require inspections of affected parts and, depending on findings,
replacement. That AD also required, for certain aeroplanes,
amendment of the applicable Aircraft Flight Manual (AFM).
Since that [EASA] AD was issued, further investigation revealed
that not all propeller blade nuts were tightened in accordance with
the Hoffman Propeller blade nut tightening procedure B2.23 which
requires a certain over-torquing and loosening of the blade nut to
limit a preload reduction due to material settlement. Prompted by
this development, Hoffmann Propeller issued SB057 (incorporating
blade nut tightening procedure B2.23) providing torquing
instructions, and SB58 providing instructions for setting correct
counterweight angles. Additionally, Hoffmann Propeller issued the
torque tightening SB (referencing SB57 and SB58) providing
inspections and corrective action instructions.
For the reasons described above, this [EASA] AD retains the
requirements of EASA AD 2020-0226R1, which is superseded, and
requires additional blade checks, inspections, and re-tightening of
the propeller blade nuts

You may examine the MCAI in the AD docket at regulations.gov under
Docket No. FAA-2022-0980.
In the NPRM, the FAA proposed to retain all of the requirements of
AD 2021-23-17. In the NPRM, the FAA also proposed to require a
maintenance records review and, depending on the results of the
maintenance records review, tightening of each propeller blade
retention nut to specified torque values. Depending on the results of
the maintenance records review, the NPRM also proposed to require
physically inspecting the propeller blade for shake. If any axial play
is detected during inspection, the NPRM proposed to require the removal
of the propeller from service and the performance of an NDT inspection
of the propeller hub, and depending on the NDT inspection results,
replacement of the propeller hub with a part eligible for installation.

Discussion of Final Airworthiness Directive

Comments

The FAA received no comments on the NPRM or on the determination of
the costs.

Conclusion

These products have been approved by the aviation authority of
another country and are approved for operation in the United States.
Pursuant to the FAA's bilateral agreement with this State of Design
Authority, it has notified the FAA of the unsafe condition described in
the MCAI referenced above. The FAA reviewed the relevant data and
determined that air safety requires adopting this AD as proposed.
Accordingly, the FAA is issuing this AD to address the unsafe condition
on these products. Except for minor editorial changes, and the removal
of the reference to Hoffmann Propeller Service Bulletin SB059 B, dated
February 23, 2022, from paragraph (j)(2), this AD is adopted as
proposed in the NPRM. None of the changes will increase the economic
burden on any operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed the following service information:
Hoffmann Propeller Service Bulletin SB057 C, dated
February 22, 2022. This service bulletin (SB) specifies procedures for
tightening the propeller blade retention nut.
Hoffmann Propeller Service Bulletin SB059 B, dated
February 23, 2022. This SB specifies procedures for tightening the
propeller blade retention nut with the correct torque and inspecting
the propeller blade for shake.
Hoffmann Propeller GmbH & Co. KG Service Bulletin SB E53
Rev. D, dated February 18, 2021, which was previously approved by the
Director of the Federal Register for incorporation by reference on
January 10, 2022 (86 FR 68905, December 6, 2021). This SB 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.

Other Related Service Information

The FAA also reviewed the following service information:
Hoffmann Propeller Service Bulletin SB058 A, dated
February 2, 2022. This SB specifies the updated definition of the
counterweight angle.

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 actions
that are required based on the results of the inspections. The agency
has no way of determining the number of aircraft that might need these
replacements:

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

The FAA has determined that 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 2021-23-17, Amendment 39-21815 (86
FR 68905, December 6, 2021); and

b. Adding the following new airworthiness directive: