Airworthiness Directives; Learjet Model 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C Airplanes, and Model 45 Airplanes

[Federal Register Volume 72, Number 166 (Tuesday, August 28, 2007)]
[Rules and Regulations]
[Pages 49162-49164]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-16676]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-28016; Directorate Identifier 2006-NM-227-AD; 
Amendment 39-15175; AD 2007-17-17]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 31, 31A, 35, 35A (C-21A), 
36, 36A, 55, 55B, and 55C Airplanes, and Model 45 Airplanes

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

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain Learjet Model 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 
55C airplanes, and Model 45 airplanes. This AD requires inspecting for 
unsealed gaps on the pylon side of the engine firewall and cleaning/
sealing any unsealed gap; and, for certain airplanes, inspecting for 
unsealed gaps of the pylon trailing edge and cleaning/sealing any gap. 
This AD results from a report that unsealed gaps (penetration points) 
of the engine firewall were discovered during production. We are 
issuing this AD to prevent penetration of flammable liquids or fire 
through the engine firewall into the engine pylon, which could lead to 
fire inside the airplane.

DATES: This AD becomes effective October 2, 2007.
    The Director of the Federal Register approved the incorporation by 
reference of certain publications listed in the AD as of October 2, 
2007.

ADDRESSES: You may examine the AD docket on the Internet at http://dms.dot.gov or in person at the U.S. Department of Transportation, 
Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 
New Jersey Avenue, SE., Washington, DC.
    Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942, 
for service information identified in this AD.

FOR FURTHER INFORMATION CONTACT: James Galstad, Aerospace Engineer, 
Mechanical Systems and Propulsion Branch, ACE-116W, FAA, Wichita 
Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-
Continent Airport, Wichita, Kansas 67209; telephone (316) 946-4135; fax 
(316) 946-4107.

SUPPLEMENTARY INFORMATION: 

[[Page 49163]]

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov 
or in person at the Docket Operations office between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays. The Docket Operations 
office (telephone (800) 647-5527) is located on the ground floor of the 
West Building at the DOT street address stated in the ADDRESSES 
section.

Discussion

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to include an AD that would apply to certain Learjet Model 
31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C airplanes, and 
Model 45 airplanes. That NPRM was published in the Federal Register on 
April 26, 2007 (72 FR 20775). That NPRM proposed to require inspecting 
for unsealed gaps on the pylon side of the engine firewall and 
cleaning/sealing any unsealed gap; and, for certain airplanes, 
inspecting for unsealed gaps of the pylon trailing edge and cleaning/
sealing any gap.

Comments

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

Conclusion

    We have carefully reviewed the available data and determined that 
air safety and the public interest require adopting the AD as proposed.

Costs of Compliance

    There are about 1,243 airplanes of the affected design in the 
worldwide fleet. This AD affects about 945 airplanes of U.S. registry. 
The following table provides the estimated costs for U.S. operators to 
comply with this AD, at an average labor rate of $80 per work hour. 
Parts and materials may be supplied from operator stores or procured 
locally.

                             Estimated Costs To Perform Inspection and Modifications
----------------------------------------------------------------------------------------------------------------
                                                                                  Number of U.S.-
                 Learjet airplane model                    Work      Cost per       registered      Fleet cost
                                                          hours      airplane        airplanes
----------------------------------------------------------------------------------------------------------------
31/31A.................................................        2            $160             173         $27,680
35/35A (C-21A).........................................        2             160             507          81,120
36/36A.................................................        2             160              42           6,720
45.....................................................        5             400             102          40,800
55/55B/55C.............................................        2             160             121          19,360
----------------------------------------------------------------------------------------------------------------

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 have 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 DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this AD and placed it in the AD docket. See the ADDRESSES 
section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

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

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the FAA amends 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 Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

2007-17-17 Learjet: Amendment 39-15175. Docket No. FAA-2007-28016; 
Directorate Identifier 2006-NM-227-AD.

Effective Date

    (a) This AD becomes effective October 2, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Learjet Model 31, 31A, 35, 35A (C-21A), 
36, 36A, 55, 55B, and 55C airplanes, and Model 45 airplanes; 
certificated in any category; as identified in the service 
information specified in Table 1 of this AD.

                                    Table 1.--Applicable Service Information
----------------------------------------------------------------------------------------------------------------
       Learjet airplane model           Service Bulletin        Revision level                  Date
----------------------------------------------------------------------------------------------------------------
31/31A.............................  Bombardier Service      1...................  August 21, 2006.
                                      Bulletin 31-54-2.

[[Page 49164]]

 
45.................................  Bombardier Service      2...................  August 15, 2003.
                                      Bulletin 45-54-3.
35/35A (C-21A) and 36/36A..........  Learjet Service         Original............  March 16, 2001.
                                      Bulletin 35/36-54-3.
55/55B/55C.........................  Learjet Service         Original............  March 16, 2001.
                                      Bulletin 55-54-3.
----------------------------------------------------------------------------------------------------------------

Unsafe Condition

    (d) This AD results from a report that unsealed gaps 
(penetration points) of the engine firewall were discovered during 
production. We are issuing this AD to prevent penetration of 
flammable liquids or fire through the engine firewall into the 
engine pylon, which could lead to fire inside the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Inspecting, Cleaning, and Sealing of Gaps in Engine Firewall

    (f) Within 12 months after the effective date of this AD, do the 
actions described in paragraphs (f)(1) and (f)(2) of this AD, in 
accordance with the applicable service information specified in 
Table 1 of this AD.
    (1) For all airplanes: Inspect for unsealed gaps on the pylon 
side of the engine firewall and clean and seal any unsealed gap.
    (2) For Learjet Model 45 airplanes only: Inspect the engine 
pylon trailing edge for unsealed gaps, and clean and seal any 
unsealed gap.

Credit for Actions Done Using Previous Service Information

    (g) Actions accomplished before the effective date of this AD 
according to Learjet Service Bulletin 31-54-2, dated March 16, 2001; 
or Bombardier Service Bulletin 45-54-3, dated March 16, 2001; or 
Revision 1, dated December 12, 2001; as applicable; are considered 
acceptable for compliance with the corresponding action specified in 
this AD.

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Wichita Aircraft Certification Office, FAA, 
has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.

Material Incorporated by Reference

    (i) You must use the service documents identified in Table 2 of 
this AD to perform the actions that are required by this AD, unless 
the AD specifies otherwise. (For Bombardier Service Bulletin 45-54-
3, Revision 2, dated August 15, 2003, only the first page of that 
document contains the correct revision date.) The Director of the 
Federal Register approved the incorporation by reference of these 
documents in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. 
Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942, 
for a copy of this service information. You may review copies at the 
FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, 
Washington; or at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, call 202-741-6030, or go to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.

              Table 2.--Material Incorporated by Reference
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       Service Bulletin          Revision level            Date
------------------------------------------------------------------------
Bombardier Service Bulletin 31- 1..............  August 21, 2006.
 54-2.
Bombardier Service Bulletin 45- 2..............  August 15, 2003.
 54-3.
Learjet Service Bulletin 35/36- Original.......  March 16, 2001.
 54-3.
Learjet Service Bulletin 55-54- Original.......  March 16, 2001.
 3.
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    Issued in Renton, Washington, on August 14, 2007.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E7-16676 Filed 8-27-07; 8:45 am]
BILLING CODE 4910-13-P

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