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[Federal Register Volume 90, Number 29 (Thursday, February 13, 2025)]
[Rules and Regulations]
[Pages 9507-9515]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-02528]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1893; Project Identifier AD-2023-00389-A; 
Amendment 39-22944; AD 2025-02-11]
RIN 2120-AA64

Airworthiness Directives; FS 2001 Corp, FS 2002 Corporation, FS 
2003 Corporation, Piper, and Piper Aircraft, Inc. Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain FS 2001 Corp, FS 2002 Corporation, FS 2003 Corporation, Piper, 
and Piper Aircraft, Inc. (Piper) airplanes. This AD was prompted by 
reports of broken rudders. This AD requires replacing any rudder 
equipped with a rudder post made from a certain carbon steel with a 
rudder equipped with a rudder post made from a certain low-alloy steel. 
The FAA is issuing this AD to address the unsafe condition on these 
products.

DATES: This AD is effective March 20, 2025.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2023-1893; 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, 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.

FOR FURTHER INFORMATION CONTACT: Joseph Zuklic, Aviation Safety 
Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone: 
(206) 231-3858; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to certain FS 2001 Corp, 
FS 2002 Corporation, FS 2003 Corporation, and Piper airplanes. The NPRM 
published in the Federal Register on October 6, 2023 (88 FR 69556). On 
November 20, 2023 (88 FR 80647) the FAA extended the comment period by 
90 days until February 20, 2024.
    The NPRM was prompted by reports of two non-fatal accidents 
involving airplanes designed and built by Piper that were caused by 
broken rudder posts that structurally failed above the upper hinge in 
flight. Both accidents occurred in Anchorage, Alaska. The first 
accident occurred on June 8, 2020, and involved an FS 2003 Model PA-12 
airplane and the second accident occurred on July 23, 2021, and 
involved an FS 2002 Model PA-14 airplane. Both airplanes sustained 
substantial damage when the rudder structurally failed.
    The National Transportation Safety Board (NTSB) published the 
report Structural Failure of Piper Part Number 40622 Rudder Posts Made 
of 1025 Carbon Steel, NTSB/AIR-22-02, dated January 10, 2022 (NTSB/AIR-
22-02), which provides information regarding the NTSB's investigations 
of these two accidents. The NTSB accident investigation report included 
a recommendation (Safety Recommendation No. A-22-3) to the FAA to issue 
an AD addressing this unsafe condition. The NTSB report can be found on 
ntsb.gov.
    The NTSB examined the rudders involved in these accidents and 
determined that the rudder posts fractured above the upper hinge and 
the top portion of the rudder folded over the upper tail brace wires. 
The NTSB also determined that the rudder posts were made from 1025 
carbon steel and fractured due to fatigue.
    Prior to the NPRM, the FAA issued an Airworthiness Concerns Sheet, 
dated September 4, 2020 (Airworthiness Concerns Sheet), which requested 
information from the aviation community regarding in-flight failure of 
the rudder just above the upper hinge on all Piper and FS2003 Corp 
(type certificate previously held by Piper) Model J-5A, J-5B, J-5C, J-
5D, AE-1, HE-1, PA-12, PA-12S, PA-14, PA-16, PA-18, L-21, PA-20, and 
PA-22 airplanes. The responses revealed that there were five additional 
broken rudder posts dating as far back as 1979.
    Before 1974, all rudders installed on Piper model airplanes were 
equipped

[[Page 9508]]

with rudder posts manufactured from 1025 carbon steel and starting in 
1974, the rudder posts were manufactured from 4130N low-alloy steel 
(Chromoly). Most parts manufacturer approval (PMA) rudders are equipped 
with rudder posts made from 4130N low-alloy steel.
    The NTSB determined that the broken rudder posts resulted from the 
combination of fatigue loading and corrosion affecting the rudder 
assemblies made from 1025 carbon steel. This condition, if not 
addressed, could result in a broken rudder and consequent reduced 
ability of the flight crew to maintain the safe flight and landing of 
the airplane.
    In the NPRM, the FAA proposed to require replacing any rudder 
equipped with a rudder post made from 1025 carbon steel with a rudder 
equipped with a rudder post made from 4130N low-alloy steel. The FAA is 
issuing this AD to address the unsafe condition on these products.

Discussion of Final Airworthiness Directive Changes After the NPRM Was 
Published

    After the NPRM was published, the FAA revised Note 2 to paragraph 
(c) of this AD to clarify that Piper Service Bulletin 1379B, dated May 
7, 2024, contains information on how to determine whether a rudder post 
is made from 4130N low-alloy steel and that this is not the only way to 
determine this, and this AD does not require the use of that service 
bulletin.
    In addition, the FAA determined that the Airplane Model column that 
was included in Table 2 to paragraph (g)--Compliance Times in the 
proposed AD is not needed and that column has been deleted in this AD.

Comments

    The FAA received comments from approximately 354 commenters. The 
FAA received comments from individual commenters as well as from 
organizations. The majority of the comments were from individuals. 
Organizations submitting comments included the Aircraft Owners and 
Pilots Association (AOPA), Experimental Aircraft Association (EAA), 
Light Aircraft Association (LAA), National Transportation Safety Board 
(NTSB), Royal Netherlands Air Force Historic Flight, The Short Wing 
Piper Club, and the Vintage Aircraft Association (VAA).
    The following summarizes the relevant comments received on the NPRM 
and provides the FAA's responses.

A. Requests To Extend the Comment Period

    Comment summary: Several commenters, including AOPA, The Short Wing 
Piper Club, and VAA, requested that the comment period for the NPRM be 
extended to allow more time for comments. AOPA requested an extension 
of 90 days to the NPRM's comment period to be able to prepare informed 
and meaningful comments with coordinated consensus among its members.
    FAA response: The FAA agreed with the commenters' requests and 
issued an extension of the NPRM's comment period that published in the 
Federal Register on November 20, 2023 (88 FR 80647). That document 
extended the comment period by 90 days, until February 20, 2024.

B. Requests To Withdraw the NPRM

    Comment summary: Numerous individual commenters, AOPA, EAA, LAA, 
and The Short Wing Piper Club requested that the NPRM be withdrawn.
1. Missing AD Docket Materials
    Numerous commenters, including individuals, AOPA, The Short Wing 
Piper Club, and VAA requested that the NPRM be withdrawn because the 
FAA did not post all required documents to the AD docket as required by 
the Federal Aviation Administration Airworthiness Directives Manual, 
FAA-IR-M-8040.1C, dated May 17, 2010 (AD Manual). The commenters 
requested additional information that the FAA used in its decision to 
publish the NPRM, specifically, the information required in Chapter 11, 
Section 3, paragraphs (a) through (g), page 63, of the AD Manual.
    FAA response: The FAA disagrees. When the NPRM was published, the 
AD docket contained all data required by the AD Manual. The list of 
requirements from Chapter 11, Section 3, paragraphs (a) through (g), 
page 63, of the AD Manual is listed below with data included in the AD 
docket, as applicable.
     Record of technical decision making: The NPRM was 
published in the Federal Register on October 6, 2023. Additionally, the 
presentation provided to the FAA by the VAA is also posted to the AD 
docket. The report by the VAA provides stress analysis utilized by the 
FAA.
     FAA reports, summaries or lists of facts, data, or reports 
that support the AD action: NTSB report NTSB/AIR-22-02 was referenced 
in the NPRM and provides a summary of the five airplanes that the NTSB 
considered in its evaluation. It provides additional information for 
each airplane (airplane model, engine horsepower, landing gear 
configuration, etc.). In the rulemaking process the FAA considered all 
five rudders that the NTSB evaluated. The FAA also considered two 
additional rudder post failures that were identified through responses 
to the Airworthiness Concerns Sheet. The NPRM identifies the two 
accidents that occurred in 2020 and 2021, which prompted the NTSB's 
safety investigation. The NPRM also identifies five additional rudder 
post failures that are considered in the AD action.
     ADs or other similar documents issued by an international 
civil aviation authority: No other ADs or similar documents issued by 
an international civil aviation authority are known, so none were 
published to the AD docket.
     Regulatory Evaluation Form: The Regulatory Evaluation Form 
is no longer required per FAA Deviation Memorandum AIR600-19-6D0-DM003, 
dated December 16, 2019.
     Records of each ex parte contact or series of contacts: 
One ex parte contact was posted to the AD docket--the presentation from 
the VAA to the FAA (a one-way presentation).
     Comments received on the proposed rulemaking: All comments 
received during the initial comment period that ended November 20, 
2023, and the extended comment period that ended February 20, 2024, are 
published to the AD docket.
     Records of approval of documents approved for 
incorporation by reference (IBR): Records of approval of IBR documents 
are no longer published to the AD docket per FAA Deviation Memorandum 
AIR100-14-140-DM08, dated April 17, 2014. Piper Service Bulletin 1379, 
dated December 2, 2022, is referenced in the NPRM, but it is not 
required to do the actions required by this AD and will not have IBR 
approval.
    The FAA has not changed this AD as a result of these comments.
2. Airworthiness Concerns Sheet
    Many commenters, including individuals, AOPA, and The Short Wing 
Piper Club, requested that the NPRM be withdrawn due to the lack of 
availability of data to interested parties. The commenters stated that 
the Airworthiness Concerns Sheet was not communicated to all interested 
parties. Some commenters also stated that they were not notified or 
were unaware of the Airworthiness Concerns Sheet posted to the FAA 
website.
    FAA response: The FAA disagrees. The Airworthiness Concerns Sheet 
is intended as a means for FAA Aviation

[[Page 9509]]

Safety Engineers to coordinate airworthiness concerns with airplane 
owners/operators through associations and type clubs before the 
decision to do an AD and before the establishment of an AD docket. At 
the time of an Airworthiness Concerns Sheet, the FAA has not made a 
determination on what type of corrective action (if any) should be 
taken. The resolution of an airworthiness concern could involve an AD 
or a special airworthiness information bulletin (SAIB), or the FAA 
could determine that no action is needed at that time. The FAA's final 
determination depends in part on the information received in response 
to the Airworthiness Concerns Sheet. The FAA endorses dissemination of 
this technical information to all manufacturers and requests 
association and type club comments. The FAA received feedback from 
several type clubs and individuals through the Airworthiness Concerns 
Sheet that helped determine the need for an AD. The FAA received 
comments through the NPRM process from 354 different commenters. Based 
on this, the FAA has determined that ample opportunity was provided for 
public input on this rulemaking action. The Airworthiness Concerns 
sheet was posted to the docket for NTSB Report ANC20LA059 and is 
available to the public.
    The FAA has not changed this AD as a result of these comments.
3. Improper Engine Installation
    Several commenters, including individuals and LAA, suggested that 
the NPRM be withdrawn because the cause of the rudder posts failing is 
that higher horsepower engines are being installed and are not 
compliant with FAA regulations. Several of the commenters further 
stated that the FAA should correct the illegal engine installations 
rather than impose an unneeded rudder replacement on the remaining 
fleet that does not have higher horsepower engines installed.
    FAA response: The FAA disagrees. These airplanes utilize higher 
horsepower engines through FAA-approved supplemental type certificates 
(STCs). The FAA has no data to show that any of the airplanes involved 
in the referenced accidents had incorrect engine installations. The 
FAA's analysis shows that the unsafe condition will occur on both the 
higher and lower horsepower engine. The FAA has added an additional 
category in table 2 to paragraph (g)(1)--Compliance Times, of this AD, 
for airplanes with lower horsepower engines (100-horsepower or below) 
that do not have a rudder post mounted beacon light, and the compliance 
time for the rudder replacement is within 10 years after the effective 
date of this AD. The FAA has no evidence that engines are being 
installed in a non-compliant manner.
    The FAA has not changed this AD as a result of these comments.
4. Risk Level
    Many commenters, including individuals, AOPA, EAA, LAA, The Short 
Wing Piper Club, and VAA, suggested that two reported incidents 
(referred to as accidents in the NPRM) does not justify an NPRM, 
therefore, it should be withdrawn. The commenters stated that two 
incidents out of over 31,000 airplanes does not represent a risk level 
that warrants an AD. Some of these individual commenters suggested that 
the NPRM be replaced by an SAIB.
    FAA response: The FAA disagrees. An SAIB contains non-mandatory 
information and guidance for certain safety issues. The SAIB is an 
information tool to alert, educate, and make recommendations to the 
aviation community about ways to improve the safety of a product. An 
SAIB is generally not issued where there is an unsafe condition. The 
FAA has data supporting its determination that an unsafe condition 
exists with the specified parts.
    The FAA evaluated two accidents and five rudder post failures to 
determine that an unsafe condition exists:
     Two separate accident investigations, referenced as 
ANC20LA059 and ANC21LA064, detailed in NTSB report NTSB/AIR-22-02.
     NTSB investigators obtained three additional previously 
broken rudders and included these broken rudders in their evaluation.
     Two additional rudder post failures that occurred in 1979 
and 1990 were reported to the FAA and the broken rudders were not 
available for the NTSB's examination. These rudder post failures were 
reported to the FAA in response to the Airworthiness Concerns Sheet. 
The 1979 airplane was a Model PA-18 with standard wheel landing gear 
and a 180-horsepower engine. The 1990 airplane was a Model PA-12 with 
ski landing gear and a 160-horsepower engine.
     The FAA also received comments from repair facilities 
indicating that this failure has happened on multiple other occasions 
over the years, although no specifics were available.
    The FAA determined that corrosion and fatigue will accelerate the 
failures over time as the strength of the rudder is continually 
compromised due to the combined effects of corrosion and fatigue. 
Furthermore, many of the approximately 31,000 airplanes are not 
currently in service (currently there are about 13,000 active airplanes 
in the fleet)--and many of these airplanes already have rudder 
assemblies made from 4130N low-alloy steel installed. Therefore, as the 
rudder post failures have accumulated over time, the number of active 
airplanes with rudder assemblies made from 1025 carbon steel has 
decreased. Given that more rudder post failures are occurring within a 
shrinking fleet size indicates that the failure is occurring more 
frequently as corrosion progresses and fatigue cycles accumulate.
    The FAA has not changed this AD as a result of these comments.
5. NPRM Not Warranted Due to No Crashes or Injury From Rudder Failure 
and Inaccuracy of the NTSB Report
    Several commenters, including individuals, AOPA, EAA, and The Short 
Wing Piper Club, suggested that the NPRM is not warranted and should be 
withdrawn. The commenters stated that there have never been any crashes 
or injuries from rudder failure. Some of the commenters further stated 
that the two reported accidents did not rise to the level of being 
called an accident and that they should be classified as ``incidents'' 
making the NPRM unnecessary.
    In addition, The Short Wing Piper Club stated that the NTSB report 
results were problematic. The Short Wing Piper Club stated that the 
NTSB report used an incorrect testing methodology to an extremely small 
sample. In addition, The Short Wing Piper Club claimed that there was 
evidence that at least one person believed the material was 4130N low-
alloy steel.
    FAA response: The FAA disagrees. The FAA issues an AD once an 
unsafe condition has been identified and the unsafe condition is likely 
to exist or develop in other products of the same type design; there 
does not need to be loss of life or significant damage to an airplane. 
Because it is a critical component, failure of a rudder could result in 
loss of control of the airplane.
    As indicated in NTSB report NTSB/AIR-22-02, the Piper Model PA-12 
and Model PA-14 airplanes that were investigated by the NTSB were both 
referred to as ``accidents.'' The FAA is adopting the same terminology 
as the NTSB. In the two accidents and five rudder post failures where a 
crash did not occur, although the airplane may have retained a limited 
amount of rudder control, it may not have been sufficient for control 
and landing in all flight conditions. In some cases, it

[[Page 9510]]

caused a permanent rudder input that the pilot could not override, and 
it also caused a pitch-up condition that the pilot had to compensate 
for with nose down elevator inputs. Even though many of the affected 
airplanes landed safely, had the weather or terrain conditions at the 
time of the flight been different, a crash could have occurred, and 
injuries could have resulted. Therefore, the FAA has determined that an 
unsafe condition exists and is likely to exist or develop in other 
products of the same type design and needs to be corrected.
    The FAA also does not agree that the NTSB reports are incorrect and 
determined that they are both technically and factually accurate. The 
hardness tests were initially performed to determine the material in 
the failed rudder posts. There is a correction used in the hardness 
tests to account for a curved surface. The failed rudder posts were 
oblong (not round) due to the failure. However, the NTSB concluded that 
the hardness tests were accurate enough to determine the material. In 
addition, the NTSB also had metallurgical tests performed on the failed 
rudders and these tests confirmed that the failed rudders were made 
from 1025 carbon steel. In addition, the FAA does not agree that a 
small sample size is inadequate or flawed. The FAA determined that the 
NTSB investigation, and the sample size, is adequate to draw a 
conclusion to the nature of the unsafe condition.
    The FAA has not changed this AD as a result of these comments.
6. Affected Airplanes on U.S. Registered Fleet
    Several commenters, including individuals, AOPA, EAA, LAA, The 
Short Wing Piper Club, and VAA, stated that the NPRM would be 
burdensome based on the sheer number of affected airplanes. The FAA 
infers that the commenters requested that the NPRM be withdrawn. The 
commenters stated that the NPRM was an overreach by the FAA based on 
only two incidents out of 31,000 airplanes in the U.S. general aviation 
fleet.
    FAA response: The FAA disagrees. Although approximately 31,000 of 
the affected airplanes were originally registered in the United States, 
about 13,000 of these airplanes are currently active. The FAA estimates 
that around half of the remaining 13,000 active airplanes already have 
a rudder assembly made from 4130N low-alloy steel. This brings the 
number of airplanes needing a new rudder down to roughly 6,500 
airplanes. Regardless of the final number of affected airplanes, the 
FAA issues ADs on airplane fleets of varying sizes to address an unsafe 
condition. As discussed above in paragraph B4, this AD was not based 
only on two accidents, but on these two accidents and five rudder post 
failures. In evaluating this information, the FAA determined that the 
unsafe condition is likely to exist on other airplanes with similar or 
the same type design.
    The FAA has not changed this AD as a result of these comments.
7. Rudder Post Failed, Not the Rudder
    Many commenters, including individuals and The Short Wing Piper 
Club, stated that the NPRM should be withdrawn or further limited in 
scope because the rudder post failed, not the rudder. The commenters 
also stated that the incident airplanes landed safely, therefore no 
unsafe condition exists.
    FAA response: The FAA disagrees. The FAA reviewed the photographs 
shown in NTSB report NTSB/AIR-22-02 and determined that the rudder had 
failed. Although the airplanes may have retained a limited amount of 
rudder control, it may not have been sufficient for controlling and 
landing those airplanes in all conditions. Additionally, just because 
airplanes have been able to land safely does not mean that rudder post 
failure would not present an unsafe condition. If the rudder post 
fails, the top of the rudder folds over in-flight, which leads to 
diminished control of the airplane and loss of control of the airplane.
    The FAA has not changed this AD as a result of these comments.
8. Rudder Availability
    Several commenters, including individuals, The Short Wing Piper 
Club, and VAA, stated that the NPRM should be withdrawn due to lack of 
rudder availability. The commenters stated that the PMA manufacturers 
will not be able to produce 31,000 new rudders to comply with the AD 
within the AD compliance times.
    FAA response: The FAA disagrees. Many of the 31,000 airplanes are 
not currently in service. There are an estimated 13,000 active 
airplanes in the U.S. fleet, and the FAA estimates that approximately 
half of those airplanes already have rudder assemblies with 4130N low-
alloy steel installed. This reduces the number of rudders needed to 
approximately 6,500. The FAA also anticipates that many operators will 
reinforce their rudders by using the alternative method of compliance 
(AMOC) process rather than replacing them. The FAA estimates that this 
will reduce the number of new rudder assemblies needed from the PMA 
manufacturers even further. In addition, the FAA anticipates that the 
PMA manufacturers can produce the necessary rudder assemblies within 
the compliance times of this AD. The FAA cannot base its AD action on 
whether spare parts are available or can be produced. While every 
effort is made to avoid grounding airplanes, the FAA must address the 
unsafe condition.
    The FAA has not changed this AD as a result of these comments.

C. Requests Regarding Applicability

    Comment summary: Numerous individual commenters, AOPA, EAA, LAA, 
NTSB, The Short Wing Piper Club, and VAA, requested applicability 
changes to the proposed AD.
1. Add Other Airplane Models to Applicability
    Several commenters, including individuals and the NTSB stated that 
other airplane models should be added to the applicability of the 
proposed AD. The commenters stated that other airplane models use the 
same rudder type.
    FAA response: The FAA partially agrees. The FAA received a letter 
from the NTSB dated November 14, 2023, which identified the Model PA-25 
airplane as a missing model in the applicability of the proposed AD. 
Piper sold the Model PA-25 airplane type certificate to a company 
located in Argentina. Therefore, the state of design for the Model PA-
25 airplane is Argentina. The FAA has transmitted the NTSB's letter to 
the National Civil Aviation Administration of Argentina, which is the 
civil aviation authority for Argentina. The FAA will work with the 
National Civil Aviation Administration of Argentina to assure that this 
condition is addressed on the Model PA-25 airplanes.
    The FAA has not changed this AD as a result of these comments.
2. Remove Model J-3 and Model PA-11 Airplanes From Applicability
    Several commenters, including individuals, LAA, The Short Wing 
Piper Club, and VAA, stated that the Model J-3 and Model PA-11 
airplanes should be removed from the applicability. The FAA infers 
that, by Model J-3 and Model PA-11 airplanes, the commenters are 
referring to all models that begin with ``J3'' and ``PA-11.'' The 
commenters stated that the rudder assembly part number for the Model 
``J3'' and Model ``PA-11'' airplanes is a different rudder assembly 
part number compared with the rudder assembly part number for the 
incident airplanes. The commenters also stated that these

[[Page 9511]]

models have never been involved in an incident where the rudder has 
failed.
    FAA response: The FAA disagrees. The rudder assembly part number 
for the Model ``J3'' and Model ``PA-11'' airplanes is different than 
the rudder assembly part number for other affected models. However, the 
part number of the rudder post itself is the same for both rudder 
assemblies. Given that the part number for the rudder post is the same 
for both rudder assemblies, the FAA disagrees with removing these 
models from this AD and has determined that the Model ``J3'' and Model 
``PA-11'' airplanes are applicable for this AD. Although stresses on 
the Model ``J3''and Model ``PA-11'' airplanes are somewhat lower than 
the rest of the fleet, the NTSB determined in NTSB report NTSB/AIR-22-
02 that the failure is a combination of fatigue and corrosion. Given 
the contribution of corrosion to the failure the FAA has determined 
that the same failure can also occur on the Model ``J3'' and Model 
``PA-11'' airplanes. The compliance times required by this AD are 
different based on category type as defined in Table 2 to paragraph 
(g)--Compliance Times of this AD.
    As previously stated, the FAA revised table 2 to paragraph (g)(1)--
Compliance Times of this AD to include a Category IV for airplanes that 
do not have a rudder post mounted beacon light and have an engine of 
100 hp or below installed. The compliance time for Category IV 
airplanes is within 10 years after the effective date of this AD. The 
Model ``J3'' and Model ``PA-11'' airplanes would fall into this 
category provided they do not have a post mounted beacon light and do 
not have an engine installed with more than 100 hp. VAA calculated 
loads and stresses on the rudder post for all affected airplane models 
and the results are posted to the AD docket.
    The FAA has not changed this AD as a result of these comments.
3. Limit to Airplanes With Floats
    Numerous commenters, including individuals, EAA, LAA, and The Short 
Wing Piper Club, requested that the applicability be limited to 
airplanes with floats installed. The commenters stated that the 
incidents occurred on airplanes that were on floats operating in a 
marine environment in Alaska. The commenters further stated that 
airplanes with floats installed require the installation of a ventral 
fin that reduces required rudder input.
    FAA response: The FAA disagrees. The FAA evaluated two accidents 
and five rudder post failures, and of the airplanes involved in those 
rudder post failures, only two airplanes were equipped with floats and 
those airplanes did not have a ventral fin installed, three airplanes 
had standard wheel landing gear, one airplane had ski landing gear, and 
one airplane had a wheel/ski landing gear configuration. Therefore, 
this failure has occurred on airplanes without floats more times than 
airplanes with floats installed. One of the affected airplanes based in 
Colorado had a standard wheel landing gear installed and was not 
operating in a marine environment; therefore, this failure mode cannot 
be attributed solely to float-equipped airplanes. Also, not all float 
configurations require a ventral fin to be installed so it cannot be 
presumed that if a ventral fin is not installed then the installation 
is incorrect. Although the ventral fin may be required for some float 
installations, it is not the only contributing factor, as this failure 
has also occurred on non-float airplanes.
    The FAA has not changed this AD as a result of these comments.
4. Limit Applicability to Model PA-12 and Model PA-14 Airplanes
    Many commenters, including individuals, AOPA, EAA, VAA, and LAA, 
suggested that the NPRM be limited to airplane configurations matching 
those of the incident airplanes (i.e., Model PA-12 and Model PA-14 
airplanes). The commenters stated that including other airplane models 
is an FAA overreach and those airplane models are not applicable to the 
unsafe condition.
    FAA response: The FAA disagrees. In addition to the airplane models 
identified by the commenters, the FAA identified a Model PA-18 airplane 
that experienced an in-flight rudder post failure. NTSB report NTSB/
AIR-22-02 also provides information on a failed rudder from a Model PA-
18 airplane. The FAA also reviewed the loads calculations in NTSB 
report NTSB/AIR-22-02 and determined that loads on other airplane 
models would not differ significantly, therefore other airplane models 
could also be susceptible to the rudder failure. This assumption is 
supported by the analysis that the VAA performed on all affected 
airplane models showing that the stresses on the rudders from both 
maneuver loads and gust loads are similar in magnitude across these 
airplane models. The VAA's analysis is posted to the AD docket. Based 
on the seven known rudder post failures on three different airplane 
models (Model PA-12, Model PA-14, and Model PA-18) and the analysis 
conducted by the NTSB and the VAA for all affected airplane models, the 
FAA has determined that issuing an AD is necessary. In accordance with 
14 CFR 39.5, the FAA issues an AD addressing a product when the FAA 
finds that an unsafe condition exists in the product and the condition 
is likely to exist or develop in other products of the same type 
design. Lastly, these rudder assemblies are rotable and can be salvaged 
from one airplane model and reinstalled on a different airplane model. 
Therefore, restricting the applicability of this AD to only include the 
airplane models referenced in NTSB/AIR-22-02 would not completely 
address the unsafe condition when considering the rotability of the 
rudder from one model to another.
    The FAA has not changed this AD as a result of these comments.
5. Limit to Airplanes With a Rudder-Mounted Beacon Light
    Numerous commenters, including individuals, EAA, LAA, The Short 
Wing Piper Club, and VAA, requested that the NPRM be limited to 
airplanes with a rudder-mounted beacon light installed. The commenters 
stated that the additional load due to the beacon light was the cause 
of the rudder post failure.
    FAA response: The FAA disagrees. Although the installation of the 
beacon light would contribute to the rudder post failure, the standard 
in-service rudder post loads and stresses likely exceed the endurance 
limit of the rudder post when corrosion, scratches, or surface 
roughness are present on the rudder post. Additionally, the propeller 
blade pass frequency is significantly higher than the natural frequency 
of the upper rudder post and would not significantly affect the bending 
stress on the rudder post. If the propeller blade pass frequency is in 
the same range as the natural frequency of the rudder post when there 
is a beacon light installed on the top of the rudder, then the stress 
on the rudder post would amplify significantly due to the propeller 
blade pass frequency. In addition, since the rudder assembly is rotable 
from one airplane to another, a rudder assembly that had the beacon 
light installed on top of the rudder could have the beacon light 
removed to avoid having to comply with this AD. Furthermore, the rudder 
assembly could be removed from one airplane, and then reinstalled on a 
different airplane without the beacon light installed. However, the 
compliance times in this AD do account for the presence of a beacon 
light as it is a contributing factor and even if an operator removed 
the beacon light to get a different compliance time, the rudder would 
still eventually need to be replaced.

[[Page 9512]]

    The FAA has not changed this AD as a result of these comments.
6. Limit to Airplanes With Higher Horsepower Engines
    Numerous commenters, including individuals, EAA, LAA, The Short 
Wing Piper Club, and VAA, requested that the NPRM be limited to 
airplanes with higher horsepower engines than what is listed on the 
type certificate data sheet for those airplane models. The commenters 
stated that the cause of the rudder post failure was the installation 
of engines with higher horsepower than specified on the applicable type 
certificate data sheet for those airplanes. The commenters suggested 
that higher horsepower engines increase p-factor (asymmetric blade 
effect), which increases rudder loading.
    FAA response: The FAA disagrees. Installation of a higher 
horsepower engine does not necessarily cause higher loads on the rudder 
if the modification did not include expanding the flight envelope of 
the airplane. Rudder inputs are common during regular flight of the 
affected fleet regardless of engine horsepower and are the primary 
source of the cyclical loading environment on the rudder post. 
Calculation of the rudder loads does not directly include the engine 
horsepower. Therefore, the rudder loads should remain largely unchanged 
for airplanes that have a higher horsepower engine installed. Although 
the p-factor would change, the FAA has no data or evidence that a 
higher p-factor contributes significantly to normal rudder loading 
during flight.
    The NTSB and VAA calculated loads and stresses on the rudder post 
that approach the endurance limit based on the maneuvering and gust 
loads prescribed in Civil Air Regulations (CAR 03), which is the 
predecessor to 14 CFR part 23, and is the original certification basis 
for the affected airplanes. With the presence of corrosion, pitting, or 
scratches, the strength of the rudder post is reduced, and the 
increased fatigue stress can exceed the endurance limit of 1025 carbon 
steel. The NTSB concluded that this is the primary mechanism that 
caused the rudder post failures.
    The FAA acknowledges that the rudders on the airplanes with lower 
horsepower engines may not need replacement as often as other models. 
As previously stated, the FAA revised Table 2 to paragraph (g)--
Compliance Times of this AD to include a Category IV for airplanes that 
do not have a rudder post mounted beacon light and have an engine of 
100 hp or below installed. The compliance time for Category IV 
airplanes is within 10 years after the effective date of this AD.
7. AD Applicability Match Piper Service Bulletin 1379
    Several individual commenters requested that the applicable serial 
numbers for various airplane models match Piper Service Bulletin 1379, 
dated December 2, 2022 (Piper Service Bulletin 1379). The commenters 
stated that the NPRM lists all serial numbers for the affected models 
whereas Piper Service Bulletin 1379 lists specific serial numbers for 
most of the affected airplane models. The commenters also stated that 
for some airplane models, Piper Service Bulletin 1379 does not call out 
all produced airplanes. The commenters further stated that matching the 
effectivity in Piper Service Bulletin 1379 would reduce the scope of 
the NPRM.
    FAA response: The FAA disagrees. Piper Aircraft, Inc. recently 
released Piper Service Bulletin 1379B, dated May 7, 2024, which 
includes all produced airplanes for each airplane model that has a type 
certificate owned by Piper. Because some of the affected airplane 
models' type certificates and design authority are now owned by FS 2001 
Corp, FS 2002 Corporation, and FS 2003 Corporation, those airplane 
models are not included in Piper Service Bulletin 1379 and that is why 
the applicability of this AD specifies all of the affected airplane 
models instead of referring to the Piper service bulletin.
    The FAA has not changed this AD as a result of these comments.

D. Requests Regarding Repetitive Inspections

    Comment summary: Many commenters, including individuals, AOPA, EAA, 
The Short Wing Piper Club, and VAA, requested an option to inspect the 
rudder post or perform strength testing on the rudder post on a regular 
basis instead of replacing the entire rudder. The commenters stated 
that corrosion is a contributor to the rudder failure, therefore, 
requiring inspections or performing strength tests would be a more 
logical and more cost-effective means to ensure the strength of the 
rudder post is adequate for flight.
    FAA response: The FAA disagrees. It would be impractical to 
repetitively inspect the rudder for cracks, corrosion, and other 
damage. The operators could inspect the inside of the rudder post tube 
with a borescope; however, they would not be able to inspect the outer 
surface of the tube without removing the fabric. An inspection interval 
that adequately monitors the rudder post condition may be too costly 
because it will require frequent removal of the covering. Furthermore, 
many of the existing 1025 carbon steel rudders have been in service for 
over 70 years, have endured multiple corrosion removal processes, and 
have been painted or powder coated several times, making accurate 
inspections more challenging.
    In addition, a load test as an inspection to determine 
airworthiness is problematic because the load test could further damage 
the rudder and contribute to an accident. It would be very difficult to 
determine an acceptable load test that would in all cases determine a 
suspect rudder and not unknowingly damage a rudder. Strength testing 
the rudder post up to approximately yield stress is also problematic. 
If the strength of the rudder has been degraded over the years due to 
corrosion and fatigue, a test load could cause permanent, but 
unnoticed, damage to the rudder and could be the cause of a rudder 
failure in a subsequent flight.
    If an owner/operator would like to implement an inspection program 
on its airplane to monitor the strength of the rudder in lieu of 
replacement, the FAA will consider the proposal upon submission of an 
AMOC request following the procedures in paragraph (h) of this AD.
    The FAA has not changed this AD as a result of these comments.

E. Requests Regarding Rudder Post Reinforcement

    Comment summary: Several commenters, including individuals, AOPA, 
EAA, LAA, The Short Wing Piper Club, and VAA, requested an option to 
reinforce the rudder post instead of replacing the entire rudder. The 
commenters stated that offering an option to reinforce the rudder post 
would be easier to accomplish and more cost-effective on the owner/
operator than replacing the entire rudder.
    FAA response: The FAA disagrees. Reinforcement could strengthen the 
critical location on the rudder post; however, many airplanes are over 
70 years old, which makes it difficult to design a repair that will 
work for all airplanes and provide that repair as an option in the 
final rule. With so many affected airplane types to consider and with 
differing in-service history, the FAA determined that the AMOC process 
would be more effective in allowing owner/operators to propose a 
reinforcement design of their choice. If an owner/operator would like 
to reinforce the rudder post in lieu of replacement, the FAA will 
consider the proposal upon submission of an AMOC

[[Page 9513]]

request following the procedures in paragraph (h) of this AD.
    The FAA has not changed this AD as a result of these comments.

F. Requests Regarding Estimated Costs

    Comment summary: Many commenters, including individuals, AOPA, The 
Short Wing Piper Club, and VAA, requested that the FAA increase the 
cost per work-hour specified in the NPRM. The commenters stated that 
$85 per work-hour is too low and does not reflect the current labor 
rate. The commenters also stated that most mechanics would not be able 
to perform the rudder replacement within 8 hours. Some of these 
commenters also stated that there should be an allowance for inflation 
over the compliance time.
    FAA response: The FAA disagrees. The FAA notes that the current 
wage rate for aviation mechanics as provided by the Bureau of Labor 
Statistics, found at bls.gov/oes/2023/may/oes493011.htm, after 
accounting for fringe benefits that are valued at roughly 50 percent of 
the nominal wage, is lower than the estimated fully burdened labor rate 
of $85 per hour. Therefore, the FAA is unable to justify increasing the 
labor rate from $85 per hour. The FAA's estimate that it would take 8 
work-hours to perform the rudder replacement was based on available 
data. The cost analysis in AD rulemaking actions typically includes 
only the costs associated with complying with the AD and does not 
include an allowance for inflation over the compliance time.
    The FAA has not changed this AD as a result of these comments.

G. Requests Regarding Compliance Times

    Comment summary: Several commenters, including individuals, the 
Royal Netherlands Airforce Historic Flight, and VAA, requested that the 
FAA use hours in service rather than years in service to establish 
compliance times. The commenters stated that hours in service should be 
the criteria that establishes when compliance action should be taken as 
it would be the causal factor in the rudder failure.
    FAA response: The FAA disagrees. The FAA determined that fatigue 
and corrosion were the contributing factors to the rudder failure. 
Hours in service may not directly correlate to the effects of corrosion 
depending on the storage conditions of the airplane. Since many of 
these airplanes are over 70 years old, and based on the unknown effects 
of corrosion, determining airplane categories based on hours in service 
would not accurately address the unsafe condition.
    The FAA has not changed this AD as a result of these comments.

H. Impact on Intrastate Aviation in Alaska and Small Entities

    Comment summary: Many commenters, including individuals and The 
Short Wing Piper Club, stated that the impact on intrastate aviation in 
Alaska was not properly assessed in the NPRM, since a significant 
number of affected airplanes are operated in Alaska and used to 
transport supplies. In addition, commenters also stated that the FAA 
did not properly assess whether there was a significant impact on a 
substantial number of small entities under the criteria of the 
Regulatory Flexibility Act. Some commenters stated that a significant 
number of small businesses and charitable operations would be impacted 
by this AD.
    FAA response: The FAA disagrees. Based on the PMA manufacturers' 
abilities to positively meet the fleet demand for parts, combined with 
the addition of the new Category IV airplane compliance time previously 
mentioned (airplanes with lower horsepower and no beacon light) that 
provides a 10-year compliance time, the FAA does not agree that this AD 
will negatively affect intrastate commerce in Alaska. In light of the 
heavy reliance on aviation for intrastate transportation in Alaska, the 
FAA has fully considered the effects of this final rule (including 
costs to be borne by affected operators) from the earliest possible 
stages of AD development. As previously stated, 14 CFR part 39 requires 
operators to correct an unsafe condition identified on an airplane to 
ensure operation of that airplane in an airworthy condition. The FAA 
has determined that the need to address fatigue loading and corrosion 
of rudder posts made from 1025 carbon steel which, if not addressed, 
could result in a broken rudder and consequent reduced ability of the 
flight crew to maintain the safe flight and landing of the airplane, 
outweighs any impact on aviation in Alaska.
    As far as this AD affecting a substantial number of small 
businesses, the FAA does not agree. The commenters did not provide any 
evidence or data to substantiate that this would affect a substantial 
number of small businesses. Based on the estimated cost impact of 
$3,000 (labor and parts cost) per each airplane affected by this final 
rule and that operators should be able to find replacement rudders 
without difficulty, the FAA has determined that this rule will not 
significantly impact a substantial number of small entities.
    The FAA has not changed this AD as a result of these comments.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, 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 the changes described 
previously, this AD is adopted as proposed in the NPRM. None of the 
changes will increase the economic burden on any operator.

Costs of Compliance

    The FAA estimates that this AD affects 30,992 airplanes of U.S. 
registry.
    The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                    Cost per       Cost on U.S.
              Action                        Labor cost            Parts cost        product         operators
----------------------------------------------------------------------------------------------------------------
Replace rudder....................  8 work-hours x $85 per             $2,320           $3,000      $92,976,000
                                     hour = $680.
----------------------------------------------------------------------------------------------------------------

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 airplane 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

[[Page 9514]]

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, Airplane, 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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2025-02-11 FS 2001 Corp, FS 2002 Corporation, FS 2003 Corporation, 
Piper, and Piper Aircraft, Inc.: Amendment 39-22944; Docket No. FAA-
2023-1893; Project Identifier AD-2023-00389-A.

(a) Effective Date

    This airworthiness directive (AD) is effective March 20, 2025.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all airplane models specified in table 1 to 
paragraph (c) of this AD, certificated in any category, that are not 
equipped with a rudder having a rudder post made from 4130N low-
alloy steel.

    Note 1 to paragraph (c):  Most parts manufacturer approval (PMA) 
rudders are equipped with a rudder post made from 4130N low-alloy 
steel. This can be verified by reviewing the individual PMA.

    Note 2 to paragraph (c):  Piper Service Bulletin 1379B, dated 
May 7, 2024, contains information on how to determine whether a 
rudder post is made from 4130N low-alloy steel. This is not the only 
way to determine this and this AD does not require the use of this 
service bulletin.

          Table 1 to Paragraph (c)--Applicable Airplane Models
------------------------------------------------------------------------
          Type certificate holder                  Airplane model
------------------------------------------------------------------------
FS 2001 Corp..............................  J5A (Army L-4F), J5A-80, J5B
                                             (Army L-4G), J5C, AE-1, HE-
                                             1.
FS 2002 Corporation.......................  PA-14.
FS 2003 Corporation.......................  PA-12, PA-12S.
Piper Aircraft, Inc.......................  J3C-40, J3C-50, J3C-50S, J3C-
                                             65, J3C-65S, PA-11, PA-11S.
Piper Aircraft, Inc.......................  J3F-50, J3F-50S, J3F-60, J3F-
                                             60S, (Army L-4D) J3F-65,
                                             J3F-65S.
Piper Aircraft, Inc.......................  J3L, J3L-S, J3L-65 (ARMY L-
                                             4C), J3L-65S.
Piper Aircraft, Inc.......................  J4, J4A, J4A-S.
Piper Aircraft, Inc.......................  J4E (ARMY L-4E).
Piper.....................................  J4F.
Piper Aircraft, Inc.......................  PA-15.
Piper Aircraft, Inc.......................  PA-16, PA-16S.
Piper Aircraft, Inc.......................  PA-17.
Piper Aircraft, Inc.......................  PA-18, PA-18S, PA-18 ``105''
                                             (Special), PA-18S ``105''
                                             (Special), PA-18A, PA-18
                                             ``125'' (Army L-21A), PA-
                                             18S ``125'', PA-18AS
                                             ``125'', PA-18 ``135''
                                             (Army L-21B), PA-18A
                                             ``135'', PA-18S ``135'', PA-
                                             18AS ``135'', PA-18
                                             ``150'', PA-18A ``150'', PA-
                                             18S ``150'', PA-18AS
                                             ``150'', PA-19 (Army L-
                                             18C), PA-19S.
Piper Aircraft, Inc.......................  PA-18A (Restricted), PA-18A
                                             ``135'' (Restricted), PA-
                                             18A ``150'' (Restricted).
Piper Aircraft, Inc.......................  PA-20, PA-20S, PA-20
                                             ``115'', PA-20S ``115'', PA-
                                             20 ``135'', PA-20S ``135''.
Piper Aircraft, Inc.......................  PA-22, PA-22-108, PA-22-135,
                                             PA-22S-135, PA-22-150, PA-
                                             22S-150, PA-22-160, PA-22S-
                                             160.
------------------------------------------------------------------------

(d) Subject

    Joint Airplane System Component (JASC) Code 5540, Rudder 
Structure.

(e) Unsafe Condition

    This AD was prompted by reports of broken rudders. The FAA is 
issuing this AD to address fatigue loading and corrosion of rudder 
posts made from 1025 carbon steel which, if not addressed, could 
result in a broken rudder and consequent reduced ability of the 
flight crew to maintain the safe flight and landing of the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Required Actions

    (1) At the applicable compliance time for the category type for 
your airplane specified in table 2 to paragraph (g)(1) of this AD, 
replace the rudder with a rudder that is equipped with a rudder post 
made from 4130N low-alloy steel.

              Table 2 to Paragraph (g)(1)--Compliance Times
------------------------------------------------------------------------
               Category type                       Compliance time
------------------------------------------------------------------------
Category I Airplanes: Airplanes having both  Within 2 years after the
 a rudder post mounted beacon light and a     effective date of this AD.
 150 or greater horsepower (hp) engine
 installed.
Category II Airplanes: Airplanes having      Within 3 years after the
 either a rudder post mounted beacon light    effective date of this AD.
 or a 150 or greater hp engine installed.
Category III Airplanes: All airplanes not    Within 5 years after the
 in Category I or Category II that do not     effective date of this AD.
 have a rudder post mounted beacon light
 and have an engine less than 150 hp and
 greater than 100 hp installed.

[[Page 9515]]

 
Category IV Airplanes: All airplanes not in  Within 10 years after the
 Category I, II, or III that do not have a    effective date of this AD.
 rudder post mounted beacon light and have
 an engine of 100 hp or below installed.
------------------------------------------------------------------------

    (2) As of the effective date of this AD, do not install any 
rudder that is equipped with a rudder post made from 1025 carbon 
steel on any airplane.

(h) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, West Certification Branch, FAA, has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, 
send your request to your principal inspector or local Flight 
Standards District Office, as appropriate. If sending information 
directly to the manager of the West Certification Branch, send it to 
the attention of the person identified in paragraph (i)(1) of this 
AD. Information may be emailed to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.

(i) Additional Information

    (1) For more information about this AD, contact Joseph Zuklic, 
Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, 
WA 98198; phone: (206) 231-3858; email: [email protected].
    (2) For material identified in this AD that is not incorporated 
by reference, contact Piper Aircraft, Inc., 2926 Piper Drive, Vero 
Beach, FL 32960; phone: (772) 299-2141; website: piper.com. You may 
view this material at the FAA, Airworthiness Products Section, 
Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For 
information on the availability of this material at the FAA, call 
(817) 222-5110.

(j) Material Incorporated by Reference

    None.

    Issued on January 31, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Airplane 
Certification Service.
[FR Doc. 2025-02528 Filed 2-12-25; 8:45 am]
BILLING CODE 4910-13-P
```