DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-0951; Project Identifier AD-2021-01047-R;
Amendment 39-21804; AD 2021-23-06]
Airworthiness Directives; Various Model 234 and Model CH-47D
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule; request for comments.
SUMMARY: The FAA is adopting a new airworthiness directive (AD)
various Model 234 and Model CH-47D helicopters. This AD was prompted by
two reports of mechanical failures of the longitudinal cyclic trim
actuator (LCTA). This AD requires determining the maintenance history,
and hours time-in-service (TIS) and number of lift cycles for each LCTA
since last overhaul, and then requires initial and repetitive overhauls
of each LCTA based on that maintenance and service history. This AD
also prohibits installing an LCTA unless it meets certain requirements.
Finally, this AD requires reporting certain information to the FAA. The
FAA is issuing this AD to address the unsafe condition on these
DATES: This AD is effective January 4, 2022.
The FAA must receive comments on this AD by February 3, 2022.
ADDRESSES: You may send comments, using the procedures found in
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
for submitting comments.
Fax: (202) 493-2251.
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.
Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
Examining the AD Docket
You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0951; 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 street address for the
Docket Operations is listed above.
FOR FURTHER INFORMATION CONTACT: David Herron, Aerospace Engineer,
Systems & Equipment Section, Seattle ACO Branch, FAA, 2200 South 216th
St., Des Moines, WA 98198; phone and fax: (206) 231-3554; email
The FAA received two reports of mechanical failure of an LCTA, the
function of which is to constrain and control the non-rotating
swashplate. In both failures, which occurred on Model CH-47D
helicopters, the flight crew was forced to make an emergency landing as
they had difficulty controlling the helicopter. Model 234 and Model CH-
47D helicopters both have the same LCTA installed, with two installed
on each rotorcraft. Investigation as to the root cause of these
failures has determined that inadequate maintenance overhaul procedures
and scheduled overhaul intervals for this critical flight component
with a single structural load path likely contributed to this unsafe
condition. One event occurred due to excessive wear of the acme screw
threads from degradation or lack of lubrication. The other event was
due to metal fatigue leading to the fracture of the fourth stage spur
gear shaft (part of the acme screw) caused by repetitive abnormal
loading. The repetitive abnormal loading occurred because of the
incorrect installation of a travel limit switch, which rendered the
switch ineffective in removing power from the electric motor at the
designed travel limit, thus allowing the electric motor to repetitively
overstroke the actuator into a mechanical stop. While the failure modes
were different, the failure effects were the same: Loss of the
constraint and control normally provided by the LCTA. Failure of the
LCTA, if not prevented, could result in loss of control of the rotor
blades and subsequent loss of control of the helicopter or the rotor
blades striking the fuselage. The FAA is issuing this AD to address the
unsafe condition on these products.
The type certificate (TC) holder for Model 234 helicopters is
Columbia Helicopters Inc. (TC previously held by Boeing Defense & Space
Group), and the TC holders for Model CH-47D helicopters currently
include Columbia Helicopters, Inc., Billings Flying Service, Inc.,
Tandem Rotor, LLC, and Unical Aviation, Inc. (originally
manufactured for military use). The FAA did not limit this AD to these
TC holders because the FAA expects that additional TC holders of
helicopters are subject to this same unsafe condition.
The FAA is issuing this AD because the agency has determined the
unsafe condition described previously is likely to exist or develop in
other products of the same type design.
This AD requires, within 3 calendar days after the effective date
of the AD, determining the hours TIS and lift cycles since last
overhaul for each LCTA. If LCTA lift cycles cannot be determined,
counting 6 lift cycles for each hour TIS is required. For purposes of
this AD, a lift cycle is defined as takeoff from ground for flight, a
lift of a new external load while in flight, or a lift of a new
internal load while in flight (e.g., fluid drawn into an internal
If the last LCTA overhaul was not approved for return to service by
a person that meets the requirements of 14 CFR part 43, or, if you are
unable to establish hours TIS and lift cycles since last overhaul of an
LCTA (e.g., hours TIS and lift cycles for each LCTA were not tracked),
this AD requires, within 10 calendar days after the effective date of
the AD, and thereafter at intervals not to exceed 3,000 hours TIS or
18,000 lift cycles, whichever occurs first, overhauling that LCTA. For
purposes of any overhaul required by this AD, the overhaul must include
an inspection of each acme screw for wear and cracking, lubricating all
drive threads and gears, and a test to ensure proper operation of the
extend and retract travel limit switches.
If the last LCTA overhaul was approved for return to service by a
person that meets the requirements of 14 CFR part 43, overhauling the
LCTA as described in this AD is required within 500 hours TIS or 3,000
lift cycles since last overhaul, whichever occurs first; or within 90
days after the effective date of the AD, whichever occurs later.
Thereafter, overhauling each LCTA at intervals not to exceed 3,000
hours TIS or 18,000 lift cycles, whichever occurs first, is required.
This AD also prohibits, as of the AD's effective date, installing
any LCTA on any helicopter unless it has been approved for return to
service by a person that meets the requirements of 14 CFR part 43 after
an overhaul as described in this AD, and that LCTA has not been in
service for more than 3,000 hours TIS or 18,000 lift cycles since that
overhaul. Finally, this AD requires, within 10 calendar days after
completing each LCTA overhaul required by this AD, reporting certain
information to the FAA.
The FAA considers this AD to be an interim action. The FAA is
currently considering requiring overhaul of the LCTA at different time
intervals or takeoff and lift cycles. However, the planned compliance
time for those actions would allow enough time to provide notice and
opportunity for prior public comment on the merits of those actions.
Additionally, the inspection reports that are required by this AD will
enable the FAA to obtain better insight into the cause of the unsafe
condition and to eventually develop final action to address the unsafe
condition. Once final action has been identified, the FAA might
consider further rulemaking.
Justification for Immediate Adoption and Determination of the Effective
Section 553(b)(3)(B) of the Administrative Procedure Act (APA) (5
U.S.C. 551 et seq.) authorizes agencies to dispense with notice and
comment procedures for rules when the agency, for ``good cause,'' finds
that those procedures are ``impracticable, unnecessary, or contrary to
the public interest.'' Under this section, an agency, upon finding good
cause, may issue a final rule without providing notice and seeking
comment prior to issuance. Further, section 553(d) of the APA
authorizes agencies to make rules effective in less than thirty days,
upon a finding of good cause.
An unsafe condition exists that requires the immediate adoption of
this AD without providing an opportunity for public comments prior to
adoption. The FAA has found that the risk to the flying public
justifies foregoing notice and comment prior to adoption of this rule
because the LCTAs are critical flight control components with design
elements that must be properly and regularly maintained to ensure
continued safe flight of the identified rotorcraft. The two reported
in-service events evidence a deficiency in the maintenance of the LCTAs
that must be resolved. Additionally, the compliance time for some of
the required actions is within 3 calendar days after the effective date
of this AD, which is shorter than the time necessary for the public to
comment and for publication of the final rule. Accordingly, notice and
opportunity for prior public comment are impracticable and contrary to
the public interest pursuant to 5 U.S.C. 553(b)(3)(B).
In addition, the FAA finds that good cause exists pursuant to 5
U.S.C. 553(d) for making this amendment effective in less than 30 days,
for the same reasons the FAA found good cause to forego notice and
The FAA invites you to send any written data, views, or arguments
about this final rule. Send your comments to an address listed under
ADDRESSES. Include ``Docket No. FAA-2021-0951 and Project Identifier
AD-2021-01047-R'' at the beginning of your comments. The most helpful
comments reference a specific portion of the final rule, explain the
reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may amend
this final rule 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
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this final rule.
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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to David
Herron, Aerospace Engineer, Systems & Equipment Section, Seattle ACO
Branch, FAA, 2200 South 216th St., Des Moines, WA 98198; phone and fax:
(206) 231-3554; email email@example.com. Any commentary that the FAA
receives which is not specifically designated as CBI will be placed in
the public docket for this rulemaking.
Regulatory Flexibility Act
The requirements of the Regulatory Flexibility Act (RFA) do not
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt
without prior notice and comment. Because FAA has determined that it
has good cause to adopt this rule without prior notice and comment, RFA
analysis is not required.
Costs of Compliance
The FAA estimates that this AD affects 74 helicopters of U.S.
Registry. Labor rates are estimated at $85 per work-hour. Based on
these numbers, the FAA estimates the following costs to comply with
Removing and reinstalling both LCTAs on each helicopter will take
about 4 work-hours, with no parts costs, for an estimated cost of about
$340 per helicopter or $25,160 for the U.S. fleet.
Overhauling both LCTAs on each helicopter will take about 56 work-
hours, and parts costs will be about $200, for an estimated cost of
about $4,960 per overhaul.
Reporting information to the FAA will take about 1 work hour per
helicopter, for an estimated cost of about $85 per report.
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.
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, and
(2) Will not affect intrastate aviation in Alaska.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
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 adding the following new airworthiness