# AD 2005-23-03: Spherical accumulator for the main hydraulic system - Type: Airworthiness directive - Status: Current - Products: Learjet 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25 and 5 more - Effective: December 19, 2005 - Published: November 14, 2005, 70 FR 69069–69071 - Issued: October 26, 2005 - Issued as: Final rule - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Large airplane - Amendment: 39-14361 - Docket: FAA-2005-22169 (https://www.regulations.gov/docket/FAA-2005-22169) - Project: 2005-NM-094-AD - Registered aircraft: 72 may be affected, by airframe or engine model (OpenAirDocs) - Official PDF: https://openairdocs.org/files/sha256/56/7b/567ba212d8490d502f2412f35243d70d854dbc9c545046d3d730eb47b4b02019 (from https://www.govinfo.gov/content/pkg/FR-2005-11-14/pdf/05-22220.pdf) - Federal Register: https://www.federalregister.gov/documents/2005/11/14/05-22220/airworthiness-directives-learjet-model-23-24-24a-24b-24b-a-24c-24d-24d-a-24e-24f-24f-a-25-25a-25b - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1135B2F1BD0B453E862570B9005F920B.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/2005-23-03 ## Summary The FAA is adopting a new airworthiness directive (AD) for certain Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, and 25F airplanes. This AD requires replacement of the spherical accumulator for the main hydraulic system with a new cylindrical accumulator. For certain airplanes, this AD also requires modification of the accumulator pressure gauge. This AD results from reports of the failure of two thrust reverser accumulators (which are similar to the main hydraulic system's spherical accumulator) and fatigue cracks found on four thrust reverser accumulators. We are issuing this AD to prevent failure of the spherical accumulator for the main hydraulic system, due to fatigue cracking on the threads, which could result in the loss of hydraulic power, damage to the surrounding airplane structure, and loss of airplane control. The failure of the accumulator could also result in injury to any persons in the surrounding area. The loss of hydraulic fluid could also leak onto a potential source of ignition and result in a consequent fire. ## The airworthiness directive 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): 2005-23-03 Learjet: Amendment 39-14361. Docket No. FAA-2005-22169; Directorate Identifier 2005-NM-094-AD. ### (a) Effective Date (a) This AD becomes effective December 19, 2005. ### (b) Affected ADs (b) None. ### (c) Applicability (c) This AD applies to Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, and 25F airplanes, certificated in any category; having serial numbers 23-003 through 23-099 inclusive, 24-100 through 24-284 inclusive, and 25-003 through 25-153 inclusive. ### (d) Unsafe Condition (d) This AD results from reports of the failure of two thrust reverser accumulators (which are similar to the main hydraulic system's accumulator) and fatigue cracks found on four thrust reverser accumulators. We are issuing this AD to prevent failure of the spherical accumulator for the main hydraulic system, due to fatigue cracking on the threads, which could result in the loss of hydraulic power, damage to the surrounding airplane structure, and loss of airplane control. The failure of the accumulator could also result in injury to any persons in the surrounding area. The loss of hydraulic fluid could also leak onto a potential source of ignition and result in a consequent fire. ### (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) Replacement (f) Within 60 days after the effective date of this AD, replace the spherical accumulator having part number (P/N) 2380025-() or P/N 2380167-() with a new cylindrical accumulator having P/N 2497202-801, in accordance with the Accomplishment Instructions of Bombardier Alert Service Bulletin A23/24/25-29-4, Revision 1, dated January 17, 2005. ### (g) Concurrent Action (g) For airplanes having serial numbers 23-003 through 23-014 inclusive: Prior to or concurrently with the actions in Bombardier Alert Service Bulletin A23/24/25-29-4, Revision 1, dated January 17, 2005, relocate the accumulator pressure gauge in accordance with Learjet Service Kit SK23-215, dated April 4, 1966. ### (h) Parts Installation (h) As of the effective date, no spherical accumulator having P/N 2380025-() or P/N 2380167-() may be installed on any airplane. ### (i) Previous Actions (i) Replacements done before the effective date of this AD in accordance with Bombardier Alert Service Bulletin A23/24/25-29-4, dated August 20, 2004, are acceptable for compliance with the requirements of paragraph (f) of this AD. ### (j) No Reporting Required (j) Although the service bulletin referenced in this AD specifies to submit certain information to the manufacturer, this AD does not include that requirement. ### (k) Alternative Methods of Compliance (AMOCs) (k)(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) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office. ### (l) Material Incorporated by Reference (l) You must use Bombardier Alert Service Bulletin A23/24/25-29-4, Revision 1, dated January 17, 2005; and Learjet Service Kit SK23-215, dated April 4, 1966; as applicable, to perform the actions that are required by this AD, unless the AD specifies otherwise. (The issue date of Learjet Service Kit SK23-215 is located only on the first and last pages of the document.) The Director of the Federal Register approved the incorporation by reference of this document 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 Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call (202) 741-6030, or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. ## Rule preamble ### Dates This AD becomes effective December 19, 2005. The Director of the Federal Register approved the incorporation by reference of certain publications listed in the AD as of December 19, 2005. ### Addresses You may examine the AD docket on the Internet at http://dms.dot.gov or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, Washington, DC. Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942, for service information identified in this AD. ### For further information contact Robert Busto, 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) 946-4157; fax (316) 946-4107. ### Examining the Docket You may examine the airworthiness directive (AD) docket on the Internet at http://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 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 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, and 25F airplanes. That NPRM was published in the Federal Register on August 23, 2005 (70 FR 49210). That NPRM proposed to require replacement of the spherical accumulator for the main hydraulic system with a new cylindrical accumulator. For certain airplanes, that proposed AD would also require modification of the accumulator pressure gauge. ### 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. ### Clarification of Alternative Method of Compliance (AMOC) Paragraph We have revised this action to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies. ### Conclusion We have carefully reviewed the available data, and determined that air safety and the public interest require adopting the AD with the change described previously. We have determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. ### Costs of Compliance There are about 434 airplanes of the affected design in the worldwide fleet. This AD will affect about 242 airplanes of U.S. registry. The actions will take about 9 to 13 work hours per airplane, at an average labor rate of $65 per work hour. Required parts will cost about $1,336 to $1,363 per airplane. Based on these figures, the estimated cost of the AD for U.S. operators is $464,882 to $534,336, or $1,921 to $2,208 per airplane. ### 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 16 of 29 models: 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E… - [TCDS A5CE](https://openairdocs.org/tcds/A5CE): Learjet Inc.; names 1 of 1 models: 23 ## 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: 72 (72 by airframe model, 0 by engine model) - Makers: Gates Lear Jet 27, Learjet 25, Gates Learjet 20 Models with the most aircraft: - [Gates Learjet 25D](https://openairdocs.org/model/gates-learjet-25d): 20 aircraft (airframe model) - [Gates Lear Jet 25B](https://openairdocs.org/model/gates-lear-jet-25b): 12 aircraft (airframe model) - [Learjet 24](https://openairdocs.org/model/learjet-24): 7 aircraft (airframe model) - [Gates Lear Jet 24D](https://openairdocs.org/model/gates-lear-jet-24d): 7 aircraft (airframe model) - [Learjet 23](https://openairdocs.org/model/learjet-23): 6 aircraft (airframe model) - [Learjet 24D](https://openairdocs.org/model/learjet-24d): 4 aircraft (airframe model) - [Gates Lear Jet 24F](https://openairdocs.org/model/gates-lear-jet-24f): 4 aircraft (airframe model) - [Learjet 24B](https://openairdocs.org/model/learjet-24b): 3 aircraft (airframe model) - [Learjet 24A](https://openairdocs.org/model/learjet-24a): 2 aircraft (airframe model) - [Gates Lear Jet 24E](https://openairdocs.org/model/gates-lear-jet-24e): 2 aircraft (airframe model) - [Learjet 25](https://openairdocs.org/model/learjet-25): 2 aircraft (airframe model) - [Gates Lear Jet 25](https://openairdocs.org/model/gates-lear-jet-25): 1 aircraft (airframe model) - [Gates Lear Jet 25C](https://openairdocs.org/model/gates-lear-jet-25c): 1 aircraft (airframe model) - [Learjet 25D](https://openairdocs.org/model/learjet-25d): 1 aircraft (airframe model) All 14 models: https://openairdocs.org/ad/2005-23-03/models.md Every aircraft: https://openairdocs.org/ad/2005-23-03/aircraft.md ## Related documents - [Proposed rule FAA-2005-22169](https://openairdocs.org/proposed/FAA-2005-22169): Notice of proposed rulemaking (NPRM), published Aug 23, 2005 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.