DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2016-0457; Directorate Identifier 2015-NM-084-AD;
Amendment 39-18751; AD 2016-25-25]
RIN 2120-AA64

Airworthiness Directives; BAE Systems (Operations) Limited
Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).

ACTION: Final rule.

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SUMMARY: We are superseding Airworthiness Directive (AD) 2012-11-15 for
all BAE Systems (Operations) Limited Model 4101 airplanes. AD 2012-11-
15 required a one-time detailed inspection for cracks, corrosion, and
other defects of the rear face of the wing rear spar, and repair if
necessary. This new AD requires repetitive detailed inspections, and
repair if necessary. This AD was prompted by new reports of cracking
found in the wing rear spar and technical analysis results, which
confirmed that the crack initiation and propagation are due to fatigue,
with no indication of any other crack initiation mechanism (e.g.,
stress corrosion). We are issuing this AD to address the unsafe
condition on these products.

DATES: This AD is effective February 7, 2017.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of February 7,
2017.

ADDRESSES: For service information identified in this final rule,
contact BAE Systems (Operations) Limited, Customer Information
Department, Prestwick International Airport, Ayrshire, KA9 2RW,
Scotland, United Kingdom; telephone +44 1292 675207; fax +44 1292
675704; email RApublications@baesystems.com; Internet http://www.baesystems.com/Businesses/RegionalAircraft/index.htm. You may view
this referenced service information at the FAA, Transport Airplane
Directorate, 1601 Lind Avenue SW., Renton, WA. For information on the
availability of this material at the FAA, call 425-227-1221. It is also
available on the Internet at http://www.regulations.gov by searching
for and locating Docket No. FAA-2016-0457.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov
by searching for and locating Docket No. FAA-2016-
0457; or in person at the Docket Management Facility between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays. The AD docket
contains this AD, the regulatory evaluation, any comments received, and
other information. The address for the Docket Office (telephone 800-
647-5527) is Docket Management Facility, 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: Todd Thompson, Aerospace Engineer,
International Branch, ANM-116, Transport Airplane Directorate, FAA,
1601 Lind Avenue SW., Renton, WA 98057-3356; telephone 425-227-1175;
fax 425-227-1149.

SUPPLEMENTARY INFORMATION:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR
part 39 to supersede AD 2012-11-15, Amendment 39-17079 (77 FR 36127,
June 18, 2012) (``AD 2012-11-15''). AD 2012-11-15 applied to all BAE
Systems (Operations) Limited Model 4101 airplanes. The NPRM published
in the Federal Register on January 21, 2016 (81 FR 3350) (``the
NPRM''). The NPRM was prompted by new reports of cracking found in the
wing rear spar and technical analysis results, which confirmed that the
crack initiation and propagation are due to fatigue, with no indication
of any other crack initiation mechanism (e.g., stress corrosion). The
NPRM proposed to require a one-time detailed inspection for cracks,
corrosion, and other defects of the rear face of the wing rear spar,
and repair if necessary. The NPRM also proposed to require repetitive
detailed inspections, and repair if necessary. We are issuing this AD
to detect and correct cracking in the wing rear spar, which could
propagate to a critical length, possibly affecting the structural
integrity of the area and resulting in a fuel tank rupture, with
consequent damage to the airplane and possible injury to its occupants.
The European Aviation Safety Agency (EASA), which is the Technical
Agent for the Member States of the European Union, has issued EASA
Airworthiness Directive 2015-0100, dated June 3, 2015 (referred to
after this as the Mandatory Continuing Airworthiness Information, or
``the MCAI''), to correct an unsafe condition for all BAE Systems
(Operations) Limited Model 4101 airplanes. The MCAI states:

During an investigation of a fuel leak on the rear spar of a
Jetstream 4100 aeroplane, 4 cracks were found between Ribs 6 and 7
(immediately inboard of the inboard engine rib). The cracks
initiated at adjacent fastener bores in the rear spar upper boom,
and progressed downwards, diagonally, into the rear spar web.
These cracks, if not detected and corrected, could propagate to
a critical length, affecting the structural integrity of the area,
possibly resulting in a fuel tank rupture with consequent damage to
the aeroplane and injury to occupants.
Prompted by these findings, EASA issued AD 2011-0096 [which
corresponds to FAA AD 2012-11-15, Amendment 39-17079 (77 FR 36127,
June 18, 2012)] to require a one-time [detailed] inspection [for
cracks, corrosion, and other defects] of the rear face of the wing
rear spar and the accomplishment of applicable corrective actions
[i.e., repair], depending on findings. Initial analysis of the event
did not lead to the conclusion that the cracking was fatigue
related, therefore [EASA] AD 2011-0096 did not require repetitive
inspections.
Since that [EASA] AD [2011-0096] was issued, the results of the
technical analysis confirmed that the cracks were due to fatigue,
with no indication of any other crack initiation mechanism (e.g.
stress corrosion). In addition, further similar in-service events
have been reported. During investigation of those events, further
metallurgical analysis indicated that the crack initiation and
propagation are indeed fatigue driven and occur at the same
location.
To address this unsafe condition, a review of the inspection
interval was undertaken based on the cracks from both aeroplanes and
BAE Systems (Operations) Ltd issued Service Bulletin (SB) J41-A57-
029 Revision 3 in order to reduce the inspection interval of the
wing rear spar from 2 000 flight cycles (FC) to 1 600 FC.
For the reasons described above, this [EASA] AD supersedes
[EASA] AD 2011-0096, without retaining its requirements, introduces
repetitive inspections and, depending on findings, requires the
accomplishments of applicable corrective action(s) [i.e., repair].

You may examine the MCAI in the AD docket on the Internet at http://www.
regulations.gov by searching for and locating Docket No. FAA-2016-0457.

Comments

We gave the public the opportunity to participate in developing
this AD. We received no comments on the NPRM or on the determination of
the cost to the public.

Explanation of Change in This AD

The NPRM incorrectly referred to Subject 57-00-00, Wings General,
of Chapter 57, Wings, of the BAE Systems (Operations) Limited Jetstream
Series 4100 Structural Repair Manual (SRM), Volume 1, Revision 32,
dated October 15, 2014, for damage criteria and repair instructions. We
have revised this final rule to refer to Chapter 57 of the SRM instead
of Subject 57-00-00.

Conclusion

We reviewed the available data and determined that air safety and
the public interest require adopting this AD as proposed, except for
minor editorial changes. We have determined that these minor changes:
Are consistent with the intent that was proposed in the
NPRM for correcting the unsafe condition; and
Do not add any additional burden upon the public than was
already proposed in the NPRM.

Related Service Information Under 1 CFR Part 51

BAE Systems (Operations) Limited has issued Alert Service Bulletin
J41-A57-029, Revision 3, dated April 8, 2014. The service information
describes detailed inspections for cracks, corrosion, and other defects
of the rear face of the wing rear spars.
BAE Systems (Operations) Limited also has issued Chapter 57, Wings,
of the Jetstream Series 4100 SRM, Volume 1, Publication Ref. No.
(Transmittal No.) SA 4-4100/SRM/400, Revision 32, dated October 15,
2014. Among other actions, Chapter 57 describes damage criteria and
procedures for repairing the wing structure.
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.

Costs of Compliance

We estimate that this AD affects 15 airplanes of U.S. registry.
We also estimate that it takes up to 25 work-hours per product to
comply with the basic requirements of this AD. The average labor rate
is $85 per work-hour. Based on these figures, we estimate the cost of
this AD on U.S. operators to be up to $31,875, or up to $2,125 per
product.
We have received no definitive data that enables us to provide a
cost estimate for the on-condition actions (repairing cracks,
corrosion, and defects) specified in this AD.

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.
We are 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

We 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. Is not a ``significant rule'' under the DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979);
3. Will not affect intrastate aviation in Alaska; and
4. 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.

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 removing Airworthiness Directive (AD)
2012-11-15, Amendment 39-17079 (77 FR 36127, June 18, 2012), and adding
the following new AD: