Proposed Rule2026-07218
Airworthiness Directives; Columbia Helicopters, Inc. and Restricted Category Model CH-47D Helicopters
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
April 14, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA proposes to adopt a new airworthiness directive (AD) for all Columbia Helicopters, Inc. Model 234 helicopters and all Restricted Category Model CH-47D helicopters. This proposed AD was prompted by reports of corrosion detected on certain flight control rigid connecting links (connecting link). This proposed AD would require repetitive borescope inspections of the connecting links for corrosion and, depending on the results of the inspection, repair of the corrosion or replacement of the connecting link with a serviceable part. This proposed AD would also require reporting the results of these inspections and would prohibit installing a certain part-numbered connecting link or a connecting link with an unknown part number on a helicopter unless certain requirements are met. The FAA is proposing this AD to address the unsafe condition on these products.
Full Text
<html>
<head>
<title>Federal Register, Volume 91 Issue 71 (Tuesday, April 14, 2026)</title>
</head>
<body><pre>
[Federal Register Volume 91, Number 71 (Tuesday, April 14, 2026)]
[Proposed Rules]
[Pages 19087-19089]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-07218]
[[Page 19087]]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-3483; Project Identifier AD-2024-00454-R]
RIN 2120-AA64
Airworthiness Directives; Columbia Helicopters, Inc. and
Restricted Category Model CH-47D Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for all Columbia Helicopters, Inc. Model 234 helicopters and all
Restricted Category Model CH-47D helicopters. This proposed AD was
prompted by reports of corrosion detected on certain flight control
rigid connecting links (connecting link). This proposed AD would
require repetitive borescope inspections of the connecting links for
corrosion and, depending on the results of the inspection, repair of
the corrosion or replacement of the connecting link with a serviceable
part. This proposed AD would also require reporting the results of
these inspections and would prohibit installing a certain part-numbered
connecting link or a connecting link with an unknown part number on a
helicopter unless certain requirements are met. The FAA is proposing
this AD to address the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by May 29,
2026.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
<bullet> Federal eRulemaking Portal: Go to <a href="http://regulations.gov">regulations.gov</a>. Follow
the instructions for submitting comments.
<bullet> Fax: (202) 493-2251.
<bullet> Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
<bullet> Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
AD Docket: You may examine the AD docket at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2026-3483; 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 NPRM, any comments received, and other
information. The street address for Docket Operations is listed above.
FOR FURTHER INFORMATION CONTACT: David Herron, Aviation Safety
Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone:
(206) 231-3544; email: <a href="/cdn-cgi/l/email-protection#9bfffaedf2ffb5f3fee9e9f4f5dbfdfafab5fcf4ed"><span class="__cf_email__" data-cfemail="92f6f3e4fbf6bcfaf7e0e0fdfcd2f4f3f3bcf5fde4">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments using a method listed
under ADDRESSES. Include ``Docket No. FAA-2026-3483; Project Identifier
AD-2024-00454-R'' at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may revise
this proposal because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
<a href="http://regulations.gov">regulations.gov</a>, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.
Confidential Business Information
CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this NPRM contain commercial
or financial information that is customarily treated as private, that
you actually treat as private, and that is relevant or responsive to
this NPRM, it is important that you clearly designate the submitted
comments as CBI. Please mark each page of your submission containing
CBI as ``PROPIN.'' The FAA will treat such marked submissions as
confidential under the FOIA, and they will not be placed in the public
docket of this NPRM. Submissions containing CBI should be sent to David
Herron, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard,
Lakewood, CA 90712. Any commentary that the FAA receives which is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.
Background
The FAA received reports regarding corrosion detected on connecting
links with part numbers (P/N) 145C3340-1, -2, -7, -8, -9, -10, -11, and
-12 installed on Columbia Helicopters, Inc. Model 234 helicopters and
Restricted Category Model CH-47D helicopters. The connecting links are
hollow control tubes that have witness holes to facilitate verification
of proper rod end thread engagement during installation. When
manufactured from non-stainless steel, these links are susceptible to
corrosion over time. This corrosion is internal to the connecting link
and is attributed to a lack of proper corrosion inhibition methods or
damage to corrosion protection during installation or inspection. This
condition, if not addressed, could result in connecting link failure
within the flight control system that could lead to reduced
controllability of the helicopter and reduced ability of the flight
crew to maintain the safe flight and landing of the helicopter.
FAA's Determination
The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.
Proposed AD Requirements in This NPRM
This proposed AD would require repetitive borescope inspections of
the connecting links to identify if there is light corrosion (less than
0.001 inches), moderate corrosion (0.001 to 0.005 inches), or severe
corrosion (greater than 0.005 inches), as defined in this proposed AD.
Depending on the results of these inspections, this proposed AD would
require repair of the corrosion or removal of the affected connecting
link from service and replacement with a serviceable part.
Additionally, this proposed AD would require reporting the results of
the borescope inspections to the FAA for four inspection cycles and
would prohibit the installation of an affected link on a helicopter
unless certain requirements are met.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 36 helicopters of U.S. registry. There are 324 connecting links
identified as having this unsafe condition. There are nine connecting
links installed per helicopter. The FAA has no way of knowing the
number of helicopters of U.S. registry that may have the affected
connecting links installed. The estimated cost on U.S. operators
reflects
[[Page 19088]]
the costs based on the number of connecting links that need to be
inspected and, if necessary, repaired or replaced.
The FAA estimates the following costs to comply with this proposed
AD:
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators
----------------------------------------------------------------------------------------------------------------
Perform borescope inspection.......... 1.5 work-hours x $85 per $0 $128 $4,608
hour = $128.
Report results........................ 1 work-hour x $85 per 0 85 3,060
hour = $85.
----------------------------------------------------------------------------------------------------------------
The FAA estimates the following costs to do any repairs or
replacements that would be required based on the results of the
proposed borescope inspection. The agency has no way of determining the
number of helicopters that might need these repairs or replacements:
On-Condition Costs
----------------------------------------------------------------------------------------------------------------
Action Labor cost Parts cost Cost per product
----------------------------------------------------------------------------------------------------------------
Remove corrosion..................... 2 work-hours x $85 per $0..................... $170 (per link).
hour = $170.
Replace connecting links............. 2 work-hours x $85 per Up to $2,535 (per link) Up to $2,705 (per
hour = $170 (per link). link).
----------------------------------------------------------------------------------------------------------------
Paperwork Reduction Act
A federal agency may not conduct or sponsor, and a person is not
required to respond to, nor shall a person be subject to a penalty for
failure to comply with a collection of information subject to the
requirements of the Paperwork Reduction Act unless that collection of
information displays a currently valid OMB Control Number. The OMB
Control Number for this information collection is 2120-0056. Public
reporting for this collection of information is estimated to be
approximately 1 hour per response, including the time for reviewing
instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing the
collection of information. All responses to this collection of
information are mandatory. Send comments regarding this burden estimate
or any other aspect of this collection of information, including
suggestions for reducing this burden, to: Information Collection
Clearance Officer, Federal Aviation Administration, 10101 Hillwood
Parkway, Fort Worth, TX 76177-1524.
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 determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 this proposed
regulation:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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 Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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:
Columbia Helicopters, Inc. and Restricted Category Helicopters:
Docket No. FAA-2026-3483; Project Identifier AD-2024-00454-R.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by May 29, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to the helicopters identified in paragraphs
(c)(1) and (2) of this AD:
(1) Columbia Helicopters, Inc. Model 234 helicopters,
certificated in any category; and
(2) Restricted Category Model CH-47D helicopters; current type
certificate holders include, but are not limited to, Billings Flying
Service, Inc., Columbia Helicopters, Inc., Tandem Rotor, LLC, and
Unical Air Inc.
(d) Subject
Joint Aircraft System Component (JASC) Code 2700, Flight Control
System.
[[Page 19089]]
(e) Unsafe Condition
This AD was prompted by reports of corrosion detected on certain
connecting links. The FAA is issuing this AD to detect and address
corrosion on certain connecting links. The unsafe condition, if not
addressed, could result in failure of the connecting link within the
flight control system that could lead to reduced controllability of
the helicopter and reduced ability of the flight crew to maintain
the safe flight and landing of the helicopter.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
(1) For helicopters identified in paragraphs (c)(1) and (2) of
this AD with a flight control rigid connecting link (connecting
link) having part numbers (P/N) 145C3340-1, 145C3340-2, 145C3340-7,
145C3340-8, 145C3340-9, 145C3340-10, 145C3340-11, or 145C3340-12, or
a link with an unknown P/N installed, within 30 days after the
effective date of this AD, accomplish a borescope inspection to
determine the level of corrosion (if any) by accomplishing the
actions required by paragraphs (g)(1)(i) and (ii) of this AD:
(i) With connecting links removed from the helicopter, loosen
the locknut and unscrew the rod end bearing on non-riveted end.
(ii) Using a borescope, inspect the interior surface of the
support rod for corrosion. Complete the following actions depending
on the results:
(A) For connecting links properly treated with primer and no
corrosion is found, before further flight, using a label or paint
pen, if unmarked, mark the tube with the part number, and mark the
following, ``H-47-24-ASAM-03 Compliant'' after each part number, and
repeat the borescope inspection at the intervals specified in table
1 to paragraph (g)(1)(ii) of this AD.
Note 1 to paragraph (g)(1)(ii)(A): This note applies to
paragraphs (g)(1)(ii)(A) through (C). Aviation Safety Action Message
(ASAM) Flight Control Link Corrosion Assessment and Repair, H-47-24-
ASAM-03, dated April 26, 2024 (H-47-24-ASAM-03), contains
information regarding corrosion and part marking.
(B) If no corrosion is found and the connecting link is not
treated with primer, or if any light or moderate corrosion is found
on any connecting link during any inspection required by this AD,
depending on the condition found, before further flight, repair the
primer defects or remove or repair the corrosion by using a method
approved by the Manager, West Certification Branch, FAA. For a
repair method to be approved by the Manager, West Certification
Branch, FAA as required by this paragraph, the Manager's approval
letter must specifically refer to this AD. After repair as approved
by the FAA, mark the following, ``H-47-24-ASAM-03 Compliant'' after
each part number. Repeat the borescope inspection at the intervals
specified in table 1 to paragraph (g)(1)(ii) of this AD.
(C) For connecting links that are determined to have severe
corrosion during any inspection required by this AD, before further
flight, remove the connecting link from service and replace it with
a serviceable part. If the replacement connecting link is not marked
``H-47-24-ASAM-03 Compliant'', mark it in accordance with paragraph
(g)(1)(ii)(A) of this AD. Repeat the borescope inspection of the
replacement connecting link at the intervals specified in table 1 to
paragraph (g)(1)(ii) of this AD.
Table 1 to Paragraph (g)(1)(ii): Repetitive Borescope Inspection
Intervals
------------------------------------------------------------------------
Repetitive borescope inspection
Type of corrosion found intervals
------------------------------------------------------------------------
No Corrosion........................... At intervals not to exceed 24
months.
Light corrosion........................ At intervals not to exceed 18
months.
Moderate corrosion..................... At intervals not to exceed 12
months.
Severe corrosion....................... No repetitive inspections.
------------------------------------------------------------------------
(2) Within 30 days after each inspection required by paragraph
(g)(1) of this AD or within 30 days after the effective date of this
AD, whichever occurs later, and for 3 reporting/inspection intervals
thereafter, report the results of these inspections to the FAA by
either email: <a href="/cdn-cgi/l/email-protection#2d14006c7b7e007a6e6f006e425f5f485e5d42434948434e486d4b4c4c034a425b"><span class="__cf_email__" data-cfemail="8cb5a1cddadfa1dbcfcea1cfe3fefee9fffce3e2e8e9e2efe9cceaededa2ebe3fa">[email protected]</span></a>; or mail: Attn:
Continued Operational Safety, West Certification Branch (AIR-770),
FAA, 3960 Paramount Boulevard, Lakewood, CA 90712-4137.
(h) Parts Installation Limitation
After the effective date of this AD, do not install a connecting
link having P/N 145C3340-1, 145C3340-2, 145C3340-7, 145C3340-8,
145C3340-9, 145C3340-10, 145C3340-11, or 145C3340-12 on any
helicopter, unless it is a serviceable part as defined in paragraph
(i)(1) of this AD.
(i) Definitions
For the purpose of this AD:
(1) A ``serviceable'' part is a connecting link that has been
inspected and repaired if necessary, as required by paragraphs
(g)(1)(i) and (ii) of this AD, or a connecting link that is new
(zero hours).
(2) Light corrosion involves scaling, blistering, or flaking of
the surface and penetrates to a depth less than 0.001 inches.
(3) Moderate corrosion involves scaling, pitting, blistering, or
flaking of the surface area and penetrates to a depth between 0.001
inches to 0.005 inches.
(4) Severe corrosion involves scaling, pitting, blistering, or
flaking of the surface area and penetrates to a depth greater than
0.005 inches.
(j) Special Flight Permits
Special flight permits, as described in 14 CFR 21.197 and
21.199, are not allowed.
(k) 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 (l)(1) of this
AD and email to: <a href="/cdn-cgi/l/email-protection#ebaaa6a4a8ab8d8a8ac58c849d"><span class="__cf_email__" data-cfemail="e0a1adafa3a0868181ce878f96">[email protected]</span></a>.
(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.
(l) Additional Information
(1) For more information about this AD, contact David Herron,
Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood,
CA 90712; phone: (206) 231-3544; email: <a href="/cdn-cgi/l/email-protection#472326312e23692f22353528290721262669202831"><span class="__cf_email__" data-cfemail="056164736c612b6d6077776a6b456364642b626a73">[email protected]</span></a>.
(2) For material identified in this AD that is not incorporated
by reference, contact U.S. Army Aviation and Missile Command
(AMCOM), AMCOM Safety, 5300 Martin Road, Redstone Arsenal, AL 35898-
5000; phone: (256) 313-4870.
(m) Material Incorporated by Reference
None.
Issued on April 10, 2026.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft
Certification Service.
[FR Doc. 2026-07218 Filed 4-13-26; 8:45 am]
BILLING CODE 4910-13-P
</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js" defer></script></body>
</html>Indexed from Federal Register on April 14, 2026.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.