DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0099; Project Identifier 2019-CE-019-AD; Amendment
39-22045; AD 2022-10-07]
RIN 2120-AA64

Airworthiness Directives; Viking Air Limited (Type Certificate
Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 89-24-06
R1, which applied to all Boeing of Canada, Ltd. and de Havilland (now
Viking Air Limited) Model DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300
airplanes. AD 89-24-06 R1 required repetitively inspecting the elevator
quadrant for damage and taking corrective action as necessary. Since
the FAA issued AD 89-24-06 R1, Transport Canada, the aviation authority
for Canada, revised its mandatory continuing airworthiness information
(MCAI) to correct this unsafe condition on these products. This AD
retains the actions required by AD 89-24-06 R1, extends the compliance
time intervals for the repetitive inspections, adds Model DHC-6-400
airplanes to the applicability, and adds a fluorescent penetrant
inspection requirement. The FAA is issuing this AD to address the
unsafe condition on these products.

DATES: This AD is effective June 23, 2022.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of June 23,
2022.

ADDRESSES: For service information identified in this final rule,
contact Viking Air Ltd., 1959 de Havilland Way, Sidney British
Columbia, Canada V8L 5V5; phone: (800) 663-8444; email:
continuing.airworthiness@vikingair.com; website: https://www.vikingair.com.
You may view this service information 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. It is also available at
https://www.regulations.gov by searching for and locating Docket No.
FAA-2022-0099.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2022-0099; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains this final rule, the
MCAI, any comments received, and other information. The address for
Docket Operations is U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Darren Gassetto, Aviation Safety
Engineer, New York ACO Branch, FAA, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590; phone: (516) 228-7323; email: 9-avs-nyaco-cos@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 89-24-06 R1, Amendment 39-6670 (Docket No.
89-CE-29-AD; 55 FR 29347, July 19, 1990) (AD 89-24-06 R1). AD 89-24-06
R1 applied to all Boeing of Canada, Ltd. and de Havilland (type
certificate currently held by Viking Air Limited) Model DHC-6-1, DHC-6-
100, DHC-6-200, and DHC-6-300 airplanes. AD 89-24-06 R1 required
repetitively inspecting the elevator quadrant, part number (P/N) C6CFM
1138-27 (Pre Mod 6/1394), P/N C6CFM 1450-27 (Post Mod 6/1394 or
production cut-in (PCI) serial number (S/N) 331, Pre Mod 6/1678), or P/
N C6CFM 1450-29 (Post Mod 6/1678 or PCI S/N 602), for distortion
(warping, buckling, and score marks on the quadrant topside face caused
by rubbing against the side of the cable guard) and replacing if
distortion is found. AD 89-24-06 R1 also required inspecting the
elevator quadrant mounting support bracket, P/N C6CFM 1142-1, for
cracks if distortion in the elevator quadrant is found and replacing
any cracked P/N C6CFM 1142-1. The FAA issued AD 89-24-06 R1 to prevent
failure of the flight control system, which could result in loss of
control of the airplane.
The NPRM published in the Federal Register on February 11, 2022 (87
FR 7965). The NPRM was prompted by Transport Canada AD CF-1972-06R5,
dated June 22, 2018 (referred to after this as ``the MCAI''), issued by
Transport Canada, which is the aviation authority for Canada. The MCAI
states:

Damage to the flight control system of DHC-6 aeroplanes was
found during inspection. The damage has been attributed to ground
gusts. The damage included cracks in the base of the lower control
column, cracks and buckles in the elevator/rudder pulley bracket,
and distortion of the elevator quadrant. Damage to the elevator
quadrant may produce abnormal loads on the quadrant support bracket
that damage the bracket.
Damaged flight control components may fail when subjected to
service loads, resulting in loss of control of the aeroplane.
This revision of the [Transport Canada] AD clarifies the
applicability of the corrective actions and endorses Service
Bulletin (SB) 6/511 as a means of accomplishing some of the required
inspections. In corrective action Part III, dye penetrant inspection
has been replaced by fluorescent penetrant inspection.

You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2022-0099.
In the NPRM, the FAA proposed to retain the actions of AD 89-24-06
R1, extend the compliance time intervals for the repetitive
inspections, add Model DHC-6-400 airplanes to the applicability, and
add a fluorescent penetrant inspection requirement.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from the Airline Pilots Association,
International, which supported the NPRM without change.

Conclusion

These products have been approved by the aviation authority of
another country and are approved for operation in the United States.
Pursuant to the FAA's bilateral agreement with this State of Design
Authority, it has notified the FAA of the unsafe condition described in
the MCAI referenced above. The FAA reviewed the relevant data,
considered the comment received, and determined that air safety
requires adopting the AD as proposed. Accordingly, the FAA is issuing
this AD to address the unsafe condition on these products. This AD is
adopted as proposed in the NPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Viking DHC-6 (Twin Otter) Service Bulletin 6-511,
Revision A, dated June 22, 1990. This service bulletin specifies
procedures for repetitively inspecting the elevator quadrant for
distortion (warping, buckling, and score marks), performing a one-time
dye penetrant inspection of the elevator quadrant support bracket for
cracks, and taking corrective actions. 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.

Differences Between This AD and the MCAI

The MCAI addresses actions on the control column lower assembly,
the elevator pulley bracket system, and the elevator quadrant. This AD
only requires actions on the elevator quadrant and elevator quadrant
support bracket. The FAA is not requiring the repetitive inspections of
the control column lower sub-assembly, lower horizontal torque tube,
and top and bottom channels of the pulley bracket assembly, and the
modifications that terminate those inspections, because those actions
are addressed by AD 69-05-01 R2, Amendment 39-3824 (Docket No. 79-EA-
63; 45 FR 45258, July 3, 1980); and AD 69-8-12 R1, Amendment 39-867
(Docket No. 69-EA-133; 34 FR 18226, November 14, 1969).

Costs of Compliance

The FAA estimates that this AD affects 133 airplanes of U.S. registry.
The FAA estimates the following costs to comply with this AD:


Estimated Costs

The FAA estimates the following costs to do any repairs or
replacements that would be required based on the results of the
inspections. The FAA has no way of determining the number of airplanes
that might need these repairs/replacements:

On-Condition Costs

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII, Aviation Programs,
describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: General requirements.
Under that section, Congress charges the FAA with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.

Regulatory Findings

The FAA has determined that this AD will not have federalism
implications under Executive Order 13132. This AD will not have a
substantial direct effect on the States, on the relationship between
the national government and the States, or on the distribution of power
and responsibilities among the various levels of government.
For the reasons discussed above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by:

a. Removing Airworthiness Directive 89-24-06 R1, Amendment 39-6670
(Docket No. 89-CE-29-AD; 55 FR 29347, July 19, 1990); and

b. Adding the following new airworthiness directive: