Airworthiness Directives; Learjet Model 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C Airplanes, and Model 45 Airplanes, 20775-20777 [E7-8001]

Download as PDF Federal Register / Vol. 72, No. 80 / Thursday April 26, 2007 / Proposed Rules electrical in origin (for example an electrical short circuit, arcing caused by chafed wiring, or a ruptured ballast case). In September 2003, in an effort to limit use of materials that sustain or propagate a fire in inaccessible areas, the FAA promulgated 14 CFR 25.856(a), which requires that thermal/acoustic insulation material installed in the fuselage meet newly developed flame propagation test requirements. That rule was Amendment 25–111. These requirements were developed to address a realistic fire threat. We consider that threat generally applicable to the 787. Conventional aluminum fuselage material does not contribute to in-flight fire propagation. As a result, there are no standards that address in-flight fire safety of the fuselage structure itself. The 787 will make extensive use of composite materials in the fabrication of the majority of the • Wing, • Fuselage skin, • Stringers, • Spars, and • Most other structural elements of all major sub-assemblies of the airplane. As a result of this extensive use of a new construction material, the fuselage cannot be assumed to have the fire resistance previously afforded by aluminum during the in-flight fire scenario mentioned above. These proposed special conditions would require that the 787 provide the same level of in-flight survivability as a conventional aluminum fuselage airplane. This includes its thermal/ acoustic insulation meeting requirements of § 25.856(a). Resistance to flame propagation must be shown, and all products of combustion that may result must be evaluated for toxicity and found acceptable. Applicability As discussed above, these proposed special conditions are applicable to the 787. Should Boeing apply at a later date for a change to the type certificate to include another model incorporating the same novel or unusual design features, these proposed special conditions would apply to that model as well under the provisions of § 21.101. jlentini on PROD1PC65 with PROPOSALS Conclusion This action affects only certain novel or unusual design features of the 787. It is not a rule of general applicability, and it affects only the applicant that applied to the FAA for approval of these features on the airplane. VerDate Aug<31>2005 21:14 Apr 25, 2007 Jkt 211001 List of Subjects in 14 CFR Part 25 Aircraft, Aviation safety, Reporting and recordkeeping requirements. The authority citation for these Special Conditions is as follows: Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704. The Proposed Special Conditions Accordingly, the Administrator of the Federal Aviation Administration (FAA) proposes the following special conditions as part of the type certification basis for the Boeing Model 787–8 airplane. In addition to the requirements of 14 CFR 25.853(a) governing material flammability, the following special conditions apply: The 787 composite fuselage structure must be shown to be resistant to flame propagation under the fire threat used to develop 14 CFR 25.856(a). If products of combustion are observed beyond the test heat source, they must be evaluated and found acceptable. Issued in Renton, Washington, on April 18, 2007. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. E7–7840 Filed 4–25–07; 8:45 am] BILLING CODE 4910–13–P DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA–2007–28016; Directorate Identifier 2006–NM–227–AD] RIN 2120–AA64 Federal Aviation Administration (FAA), Department of Transportation (DOT). ACTION: Notice of proposed rulemaking (NPRM). AGENCY: SUMMARY: The FAA proposes to adopt 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 proposed AD would 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. This proposed AD results from a report that unsealed gaps (penetration points) of the engine Frm 00002 Fmt 4702 firewall were discovered during production. We are proposing 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: We must receive comments on this proposed AD by June 11, 2007. ADDRESSES: Use one of the following addresses to submit comments on this proposed AD. • DOT Docket Web site: Go to https://dms.dot.gov and follow the instructions for sending your comments electronically. • Government-wide rulemaking Web site: Go to https://www.regulations.gov and follow the instructions for sending your comments electronically. • Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL–401, Washington, DC 20590. • Fax: (202) 493–2251. • Hand Delivery: Room PL–401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209–2942, for the service information identified in this proposed AD. FOR FURTHER INFORMATION CONTACT: James Galstad, Aerospace Engineer, 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: Comments Invited Airworthiness Directives; Learjet Model 31, 31A, 35, 35A (C–21A), 36, 36A, 55, 55B, and 55C Airplanes, and Model 45 Airplanes PO 00000 20775 Sfmt 4702 We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number ‘‘FAA–2007–28016; Directorate Identifier 2006–NM–227–AD’’ at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments. We will post all comments we receive, without change, to https:// dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that web site, anyone can find and read the E:\FR\FM\26APP1.SGM 26APP1 20776 Federal Register / Vol. 72, No. 80 / Thursday April 26, 2007 / Proposed Rules section. Comments will be available in the AD docket shortly after the Docket Management System receives them. comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review DOT’s complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477–78), or you may visit https:// dms.dot.gov. Discussion Examining the Docket You may examine the AD docket on the Internet at https://dms.dot.gov, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647–5227) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES We have received a report indicating that the engine firewall sealing application on certain Learjet Model 45 airplanes does not meet engineering standards, as unsealed gaps (penetration points) of the engine firewall were discovered during production. Further investigation revealed that the same condition could be present on Model 31, 31A, 35, 35A (C–21A), 36, 36A, 55, 55B, and 55C airplanes. Such gaps could include those provided for bleed air, anti-ice, fuel, and fire extinguishing systems, as well as engine mounts, control cables, access panels, and others not described. This condition, if not corrected, could result in penetration of flammable liquids or fire through the engine firewall into the engine pylon, which could lead to fire inside the airplane. Relevant Service Information We have reviewed the service bulletins specified in the following table. For all airplanes, the service bulletins describe procedures for inspecting for unsealed gaps on the pylon side of the engine firewall and cleaning/sealing any unsealed gap. For Model 45 airplanes only, Service Bulletin 45–54–3 also describes procedures for inspecting for unsealed gaps on the pylon trailing edge and cleaning/sealing any unsealed gap. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition. APPLICABLE SERVICE INFORMATION Learjet airplane model Service bulletin Revision level 31/31A ......................................... 45 ................................................ 35/35A (C–21A) and 36/36A ...... 55/55B/55C ................................. Bombardier Service Bulletin 31–54–2 ............................................. Bombardier Service Bulletin 45–54–3 ............................................. Learjet Service Bulletin 35/36–54–3 ............................................... Learjet Service Bulletin 55–54–3 .................................................... 1 ....................... 2 ....................... Original ............. Original ............. FAA’s Determination and Requirements of the Proposed AD We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously. Costs of Compliance There are about 1,243 airplanes of the affected design in the worldwide fleet. Date August 21, 2006. August 15, 2003. March 16, 2001. March 16, 2001. This proposed AD would affect about 945 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed 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 Learjet airplane model 31/31A .............................................................................................................. 35/35A (C–21A) ............................................................................................... 36/36A .............................................................................................................. 45 ..................................................................................................................... 55/55B/55C ...................................................................................................... jlentini on PROD1PC65 with PROPOSALS 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 VerDate Aug<31>2005 21:14 Apr 25, 2007 Jkt 211001 Cost per airplane Work hours 2 2 2 5 2 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 proposed AD would not have federalism implications under Executive Order PO 00000 Frm 00003 Fmt 4702 Sfmt 4702 $160 160 160 400 160 Number of U.S.-registered airplanes 173 507 42 102 121 Fleet cost $27,680 81,120 6,720 40,800 19,360 13132. This proposed AD would 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 the proposed regulation: 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); and E:\FR\FM\26APP1.SGM 26APP1 20777 Federal Register / Vol. 72, No. 80 / Thursday April 26, 2007 / Proposed Rules 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 proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation. The Proposed Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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. List of Subjects in 14 CFR Part 39 § 39.13 Air transportation, Aircraft, Aviation safety, Safety. [Amended] 2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD): LEARJET: Docket No. FAA–2007–28016; Directorate Identifier 2006–NM–227–AD. Comments Due Date (a) The FAA must receive comments on this AD action by June 11, 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 31/31A ......................................... 45 ................................................ 35/35A (C–21A) and 36/36A ...... 55/55B/55C ................................. Bombardier Service Bulletin 31–54–2 ............................................. Bombardier Service Bulletin 45–54–3 ............................................. Learjet Service Bulletin 35/36–54–3 ............................................... Learjet Service Bulletin 55–54–3 .................................................... 1 ....................... 2 ....................... Original ............. Original ............. 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. DEPARTMENT OF TRANSPORTATION (h)(1) The Manager, Wichita Aircraft Certification Office (ACO), 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. Federal Aviation Administration Issued in Renton, Washington, on April 19, 2007. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. E7–8001 Filed 4–25–07; 8:45 am] BILLING CODE 4910–13–P jlentini on PROD1PC65 with PROPOSALS (g) Actions accomplished before the effective date of this AD according to Bombardier 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. 21:14 Apr 25, 2007 Jkt 211001 August 21, 2006. August 15, 2003. March 16, 2001. March 16, 2001. Alternative Methods of Compliance (AMOCs) Credit for Actions Done Using Previous Service Information VerDate Aug<31>2005 Date PO 00000 Frm 00004 Fmt 4702 Sfmt 4702 14 CFR Part 39 [Docket No. FAA–2006–26353; Directorate Identifier 2006–NM–189–AD] RIN 2120–AA64 Airworthiness Directives; Bombardier Model CL–600–1A11 (CL–600), CL– 600–2A12 (CL–601), CL–600–2B16 (CL– 601–3A, CL–601–3R, and CL–604) Airplanes Federal Aviation Administration (FAA), Department of Transportation (DOT). ACTION: Supplemental notice of proposed rulemaking (NPRM); reopening of comment period. AGENCY: SUMMARY: The FAA is revising an earlier NPRM for an airworthiness directive (AD) that applies to certain Bombardier Model CL–600–1A11 (CL–600) airplanes, CL–600–2A12 (CL–601) airplanes, and CL–600–2B16 (CL–601– 3A, CL–601–3R, and CL–604) airplanes. The original NPRM would have required inspecting to identify the part number and serial number of the selector valves of the nose landing gear (NLG) and the nose gear door; and doing related investigative and corrective actions if necessary. The original NPRM resulted from reports of uncommanded partial retractions of the NLG. This action revises the original NPRM by adding airplanes to the applicability. E:\FR\FM\26APP1.SGM 26APP1

Agencies

[Federal Register Volume 72, Number 80 (Thursday, April 26, 2007)]
[Proposed Rules]
[Pages 20775-20777]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E7-8001]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-28016; Directorate Identifier 2006-NM-227-AD]
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: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt 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 proposed AD would 
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. This proposed AD results from a report that 
unsealed gaps (penetration points) of the engine firewall were 
discovered during production. We are proposing 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: We must receive comments on this proposed AD by June 11, 2007.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to https://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to https://
www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: Docket Management Facility, U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, 
Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942, 
for the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT: James Galstad, Aerospace Engineer, 
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:

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed in the ADDRESSES section. Include the docket number ``FAA-2007-
28016; Directorate Identifier 2006-NM-227-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments received by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to https://
dms.dot.gov, including any personal information you provide. We will 
also post a report summarizing each substantive verbal contact with FAA 
personnel concerning this proposed AD. Using the search function of 
that web site, anyone can find and read the

[[Page 20776]]

comments in any of our dockets, including the name of the individual 
who sent the comment (or signed the comment on behalf of an 
association, business, labor union, etc.). You may review DOT's 
complete Privacy Act Statement in the Federal Register published on 
April 11, 2000 (65 FR 19477-78), or you may visit https://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at https://
dms.dot.gov, or in person at the Docket Management Facility office 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The Docket Management Facility office (telephone (800) 647-
5227) is located on the plaza level of the Nassif Building at the DOT 
street address stated in the ADDRESSES section. Comments will be 
available in the AD docket shortly after the Docket Management System 
receives them.

Discussion

    We have received a report indicating that the engine firewall 
sealing application on certain Learjet Model 45 airplanes does not meet 
engineering standards, as unsealed gaps (penetration points) of the 
engine firewall were discovered during production. Further 
investigation revealed that the same condition could be present on 
Model 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C airplanes. 
Such gaps could include those provided for bleed air, anti-ice, fuel, 
and fire extinguishing systems, as well as engine mounts, control 
cables, access panels, and others not described. This condition, if not 
corrected, could result in penetration of flammable liquids or fire 
through the engine firewall into the engine pylon, which could lead to 
fire inside the airplane.

Relevant Service Information

    We have reviewed the service bulletins specified in the following 
table. For all airplanes, the service bulletins describe procedures for 
inspecting for unsealed gaps on the pylon side of the engine firewall 
and cleaning/sealing any unsealed gap. For Model 45 airplanes only, 
Service Bulletin 45-54-3 also describes procedures for inspecting for 
unsealed gaps on the pylon trailing edge and cleaning/sealing any 
unsealed gap. Accomplishing the actions specified in the service 
information is intended to adequately address the unsafe condition.

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

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require accomplishing the actions specified in the service 
information described previously.

Costs of Compliance

    There are about 1,243 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 945 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed 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 hours       Cost per       registered      Fleet cost
                                                                     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 proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would 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 the proposed 
regulation:
    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); and

[[Page 20777]]

    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 proposed 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, Safety.

The Proposed Amendment

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

LEARJET: Docket No. FAA-2007-28016; Directorate Identifier 2006-NM-
227-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by June 11, 
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.
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 Bombardier 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 (ACO), 
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.

    Issued in Renton, Washington, on April 19, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-8001 Filed 4-25-07; 8:45 am]
BILLING CODE 4910-13-P
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