DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2020-0907; Product Identifier 2017-SW-072-AD; Amendment
39-21429; AD 2021-04-08]
Airworthiness Directives; Airbus Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
Airbus Helicopters Model AS350B3 helicopters. This AD requires
modifying the electrical system of the throttle twist grip, inspecting
the routing of a microswitch electrical harness, and correcting the
electrical harness routing if it is incorrect. This AD was prompted by
reports of the engine remaining in idle when the twist grip was turned
from the "forced idle" position to the "flight" position. The
actions of this AD are intended to address an unsafe condition on these
DATES: This AD is effective April 1, 2021.
The Director of the Federal Register approved the incorporation by
reference of a certain document listed in this AD as of April 1, 2021.
ADDRESSES: For service information identified in this final rule,
contact Airbus Helicopters, 2701 N Forum Drive, Grand Prairie, TX
75052; telephone 972-641-0000 or 800-232-0323; fax 972-641-3775; or at
may view the referenced service information at the FAA, Office of the
Regional Counsel, Southwest Region, 10101 Hillwood Pkwy., Room 6N-321,
Fort Worth, TX 76177. It is also available on the internet at https://www.regulations.gov
by searching for and locating Docket No. FAA-2020-0907.
Examining the AD Docket
You may examine the AD docket on the internet at https://www.regulations.gov
by searching for and locating Docket No. FAA-2020-
0907; or in person at Docket Operations between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays. The AD docket contains
this AD, the European Aviation Safety Agency (now European Union
Aviation Safety Agency) (EASA) AD, any service information that is
incorporated by reference, any comments received, and other
information. The street 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
FOR FURTHER INFORMATION CONTACT: Ronnea Derby, Aviation Safety
Engineer, Denver ACO Branch, FAA, 26805 E 68th Ave., Denver, CO 80249;
telephone 303-342-1093; email firstname.lastname@example.org.
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to Airbus Helicopters
Model AS350B3 helicopters with a Turbomeca ARRIEL 2B engine installed.
The NPRM published in the Federal Register on October 15, 2020 (85 FR
65285). The NPRM proposed to require, based on helicopter
configuration, modifying the electrical system of the throttle twist
grip. The proposed AD also proposed to require inspecting the routing
of a microswitch electrical harness, and depending on the routing of
that electrical harness, correcting the routing. The proposed
requirements were intended to prevent failure of the electrical
operation of the throttle twist grip, which can prevent switching from
"IDLE" mode to "FLIGHT" mode. During autorotation training or
during governor failure training (when the throttle grip is turned in
the low flow direction), this condition prohibits recovery from a
practice autorotation and compels the pilot to continue the
autorotation to the ground. This condition could result in unintended
touchdown to the ground at a flight-idle power setting, damage to the
helicopter, and injury to occupants.
The NPRM was prompted by EASA AD No. 2017-0035, dated February 20,
2017 (EASA AD 2017-0035), to correct an unsafe condition for Airbus
Helicopters (formerly Eurocopter) Model AS 350 B3 helicopters with
ARRIEL 2B engines installed. EASA advises of an initial report of the
microswitch pin jammed in the pushed-in position resulting in the
engine remaining in idle when the twist grip had been turned back to
the "flight" position during an autorotation training exercise. This
condition could also occur during governor failure training when the
twist grip is turned in the low flow rate direction. EASA also advises
of two later reports of this condition, with one of those reports
related to an incorrectly routed electrical harness. EASA advises that
this condition, if not detected and corrected, could lead to reduced
control of the helicopter.
EASA initially issued AD No. 2006-0094, dated April 21, 2006, which
required repetitive testing of the microswitch and established a life
limit for the microswitch. Subsequent EASA AD action required reducing
that life limit, inspecting the travel of the collective lever,
performing an additional check of the collective lever for free travel,
and installing a terminating action modification that was available for
certain helicopter configurations. That modification gave priority to
the HydroMechanical Unit (HMU) flight position when the microswitch
failed to operate correctly at forced idle. EASA most recently issued
AD 2017-0035, which prompted this AD action, to include all of the
previous AD requirements and expand the terminating action modification
to other helicopter configurations.
The FAA gave the public the opportunity to participate in
developing this final rule, but the FAA did not receive any comments on
the NPRM or on the determination of the cost to the public.
This helicopter has been approved by EASA and is approved for
operation in the United States. Pursuant to the FAA's bilateral
agreement with the European Union, EASA has notified the FAA of the
unsafe condition described in its AD. The FAA is issuing this AD after
evaluating all of the information provided by EASA and determining the
unsafe condition exists and is likely to exist or develop on other
helicopters of the same type design and that air safety and the public
interest require adopting the AD requirements as proposed, except for a
minor editorial change. The FAA has determined that this minor
editorial change is consistent with the intent that was proposed in the
NPRM for addressing the unsafe condition and does not add any
additional burden upon the public than was already proposed in the NPRM.
Differences Between This AD and the EASA AD
The EASA AD specifies a repetitive test of the microswitch, a life
limit for the microswitch, and inspecting the travel of the collective
lever, until the terminating action of modifying the electrical system
of the throttle twist grip and inspecting the routing of a microswitch
electrical harness are completed. This AD only requires modifying the
electrical system of the throttle twist grip and inspecting the routing
of a microswitch electrical harness. The EASA AD specifies performing
that terminating action in a compliance time of calendar months. This
AD requires performing the required actions before the next practice
autorotation, before the next simulated governor failure, or within 330
hours time-in service, whichever occurs first.
Related Service Information Under 1 CFR Part 51
The FAA reviewed Airbus Helicopters Alert Service Bulletin (ASB)
No. AS350-67.00.43, Revision 3, dated June 16, 2016, which specifies
procedures, based on different configurations, to modify the electrical
operation to give priority to the HMU flight position when the
microswitch does not operate correctly at forced idle (corresponds to
Airbus Helicopters Modification (MOD) 073357). This service information
also specifies instructions to inspect the routing of microswitch
electrical harness number "53K".
This service information is reasonably available because the
interested parties have access to it through their normal course of
business or by the means identified in the ADDRESSES section.
Other Related Service Information
The FAA also reviewed Eurocopter ASB No. 05.00.49, Revision 3,
dated March 8, 2012. This service information specifies procedures, for
helicopters without MOD 073357 installed, for repetitive testing of the
microswitch, a life limit for the microswitch, inspecting the travel of
the collective lever, and verifying correct wiring harness installation.
Costs of Compliance
The FAA estimates that this AD affects 517 helicopters of U.S.
Registry. The FAA estimates that operators may incur the following
costs in order to comply with this AD. Labor costs are estimated at $85
per work-hour. Modifying the electrical system and inspecting the
electrical harness routing takes about 30 work-hours and parts will
cost about $9,692 for an estimated cost of $12,242 per helicopter and
$6,329,114 for the U.S. fleet.
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 helicopters 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,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
Adoption of the Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by adding the following new airworthiness