# AD 2007-17-17: Unsealed gaps on the pylon side of the engine firewall - Type: Airworthiness directive - Status: Current - Products: Learjet 31, 31A, 35, 35A (C-21A), 36, 36A, 45, 55, 55B and 55C - Effective: October 2, 2007 - Published: August 28, 2007, 72 FR 49162–49164 - Issued: August 14, 2007 - Issued as: Final rule - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane, Small/large airplane - Amendment: 39-15175 - Docket: FAA-2007-28016 (https://www.regulations.gov/docket/FAA-2007-28016) - Project: 2006-NM-227-AD - Registered aircraft: 830 may be affected, by airframe or engine model (OpenAirDocs) - Official PDF: https://openairdocs.org/files/sha256/39/85/39858e1ad3415d73d5cfa37efd88d840bb3d4be802cb41fd734b841e2da055ee (from https://www.govinfo.gov/content/pkg/FR-2007-08-28/pdf/E7-16676.pdf) - Federal Register: https://www.federalregister.gov/documents/2007/08/28/E7-16676/airworthiness-directives-learjet-model-31-31a-35-35a-c-21a-36-36a-55-55b-and-55c-airplanes-and-model - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/62023CBA34D006AC862573450061FFDA.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/2007-17-17 ## 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. ## The airworthiness directive ### Adoption of the Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows: 1. The authority citation for part 39 continues to read as follows: 2. The Federal Aviation Administration (FAA) amends § 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. ### (a) Effective Date (a) This AD becomes effective October 2, 2007. ### (b) Affected ADs (b) None. ### (c) 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 Bulletin 31-54-2 | 1 | August 21, 2006. | | 45 | Bombardier Service Bulletin 45-54-3 | 2 | August 15, 2003. | | 35/35A (C-21A) and 36/36A | Learjet Service Bulletin 35/36-54-3 | Original | March 16, 2001. | | 55/55B/55C | Learjet Service Bulletin 55-54-3 | Original | March 16, 2001. | ### (d) 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. ### (e) 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. ### (f) 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. ### (g) 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. ### (h) 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. ### (i) 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* | Service Bulletin | Revision level | Date | | --- | --- | --- | | Bombardier Service Bulletin 31-54-2 | 1 | August 21, 2006. | | Bombardier Service Bulletin 45-54-3 | 2 | August 15, 2003. | | Learjet Service Bulletin 35/36-54-3 | Original | March 16, 2001. | | Learjet Service Bulletin 55-54-3 | Original | March 16, 2001. | ## Rule preamble ### 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. ### 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* | Learjet airplane model | Work hours | Cost per airplane | Number of U.S.-registered airplanes | Fleet cost | | --- | --- | --- | --- | --- | | 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. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS A10CE](https://openairdocs.org/tcds/A10CE): Learjet Inc.; names 9 of 29 models: 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B… - [TCDS T00008WI](https://openairdocs.org/tcds/T00008WI): Learjet Inc.; names 1 of 1 models: 45 ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 830 (830 by airframe model, 0 by engine model) - Makers: Learjet 581, Gates Learjet 199, Gates Lear Jet 50 Models with the most aircraft: - [Learjet 45](https://openairdocs.org/model/learjet-45): 433 aircraft (airframe model) - [Gates Learjet 35A](https://openairdocs.org/model/gates-learjet-35a): 135 aircraft (airframe model) - [Learjet 31A](https://openairdocs.org/model/learjet-31a): 104 aircraft (airframe model) - [Gates Learjet 55](https://openairdocs.org/model/gates-learjet-55): 54 aircraft (airframe model) - [Learjet 35A](https://openairdocs.org/model/learjet-35a): 24 aircraft (airframe model) - [Gates Lear Jet 36A](https://openairdocs.org/model/gates-lear-jet-36a): 21 aircraft (airframe model) - [Gates Lear Jet 35](https://openairdocs.org/model/gates-lear-jet-35): 16 aircraft (airframe model) - [Learjet 31](https://openairdocs.org/model/learjet-31): 15 aircraft (airframe model) - [Gates Lear Jet 36](https://openairdocs.org/model/gates-lear-jet-36): 13 aircraft (airframe model) - [Gates Learjet 55C](https://openairdocs.org/model/gates-learjet-55c): 6 aircraft (airframe model) - [Learjet 55](https://openairdocs.org/model/learjet-55): 4 aircraft (airframe model) - [Gates Learjet 55B](https://openairdocs.org/model/gates-learjet-55b): 3 aircraft (airframe model) - [Learjet 35](https://openairdocs.org/model/learjet-35): 1 aircraft (airframe model) - [Gates Learjet 35A (C-21A)](https://openairdocs.org/model/gates-learjet-35a-c-21a): 1 aircraft (airframe model) All 15 models: https://openairdocs.org/ad/2007-17-17/models.md Every aircraft: https://openairdocs.org/ad/2007-17-17/aircraft.md ## Related documents - [Proposed rule FAA-2007-28016](https://openairdocs.org/proposed/FAA-2007-28016): Notice of proposed rulemaking (NPRM), published Apr 26, 2007 Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.