AD 95-21-03

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Learjet Model 31A and 60 airplanes. This action requires an inspection to identify the serial numbers of the engine fire pull switch assemblies, and replacement of the assembly with a serviceable assembly, if necessary. This amendment is prompted by a report indicating that certain engine fire pull switch assemblies may contain microswitches that were manufactured with internal defects. Such defects could result in electrical failure of the switch in the open or closed position. The actions specified in this AD are intended to prevent failure of the switch, which could result in the inability of the flight crew to shut down certain systems or to arm the fire extinguishers due to inoperation of the fire tee handle, or inadvertent shutdown of one or both engines due to fuel starvation

Final rule; request for comments

95-21-03 LEARJET: Amendment 39-9388. Docket 95-NM-178-AD.

Applicability: Model 31A airplanes, serial numbers 31-093 through 31-108 inclusive; and Model 60 airplanes, serial numbers 60-034 through 60-061 inclusive; certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (d) of this AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on theunsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent electrical failure of the microswitches in the engine fire pull switch assembly, which could result in the inability of the flight crew to shut down certain systems or to arm the fire extinguishers, or inadvertent shutdown of one or both engines, accomplish the following:

(a) For Model 31A airplanes: Within 50 hours time-in-service after the effective date of this AD, perform an inspection to identify the serial numbers of the left-hand (pilot) and right-hand (copilot) engine fire pull switch assemblies in accordance with Learjet Alert Service Bulletin SB A31-26-3, dated July 14, 1995.

(1) If the serial number of the assembly is not identified as 2326, 2363 through 2377 inclusive, or 3000 through 3019 inclusive: No further action is required by this AD.

(2) If the serial number of the assembly is identified as 2326, 2363 through 2377 inclusive, or 3000 through 3019 inclusive: Prior to further flight, replace the engine fire pull switch assembly with a serviceable assembly in accordance with the alert service bulletin.

(b) For Model 60 airplanes: Within 50 hours time-in-service after the effective date of this AD, perform an inspection to identify the serial numbers of the left-hand (pilot) and right-hand (copilot) engine fire pull switch assemblies in accordance with Learjet Alert Service Bulletin SB A60-26-1, dated July 14, 1995.

(1) If the serial number of the assembly is not identified as 106 through 168 inclusive: No further action is required by this AD.

(2) If the serial number of the assembly is identified as 106 through 168 inclusive: Prior to further flight, replace the engine fire pull switch assembly with a serviceable assembly in accordance with the alert servicebulletin.

(c) As of the effective date of this AD, no person shall install on any airplane an engine fire pull switch assembly having a serial number identified in paragraph (c)(1) or (c)(2) of this AD, as applicable, unless such serial number is preceded by the letters "RS" and accompanied by a repair date code later than June 1, 1995.

(1) For Model 31A airplanes: Serial numbers 2326, 2363 through 2377 inclusive, and 3000 through 3019 inclusive.

(2) For Model 60 airplanes: Serial numbers 106 through 168 inclusive.

(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Wichita Aircraft Certification Office (ACO), FAA, Small Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Wichita ACO.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Wichita ACO.

(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

(f) The inspection and replacement shall be done in accordance with Learjet Alert Service Bulletin SB A31-26-3, dated July 14, 1995, and Learjet Alert Service Bulletin SB A60-26-1, dated July 14, 1995. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Gates Learjet, Mid-Continent Airport, P.O. Box 7707, Wichita, Kansas 67277. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Wichita Aircraft Certification Office, Small Airplane Directorate, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(g) This amendment becomes effective on October 26, 1995.

The FAA has received a report indicating that a certain batch of engine fire pull switch assemblies may contain microswitches that were manufactured with internal defects. These assemblies are installed on Learjet Model 31A and 60 airplanes. The left-hand (pilot) and right-hand (copilot) engine fire pull switch assemblies contain four microswitches each, all of which may be affected. Such internal defects can cause electrical failure of the switch in the open or closed position, regardless of the position of the ENG FIRE PULL tee handle. If the switch fails in the open position, the fire tee handle would be inoperable. This condition, if not corrected, could result in the inability of the flight crew to shut down certain systems (such as the fuel or hydraulics system) or to arm the fire extinguishers. Failure of the switch in the closed position could result in fuel starvation. This condition, if not corrected, could result in inadvertent shutdown of one or both engines during flight.

The FAA has reviewed and approved Learjet Alert Service Bulletin SB A31-26-3 (for Model 31A airplanes) and SB A60-26-1 (for Model 60 airplanes), both dated July 14, 1995, which describe procedures for an inspection to identify the serial numbers of the left-hand (pilot) and right-hand (copilot) engine fire pull switch assemblies, and replacement of any suspect assembly with a serviceable assembly. Replacement of suspect assemblies will restore the integrity of the engine fire pull switch.

Since an unsafe condition has been identified that is likely to exist or develop on other Learjet Model 31A and 60 airplanes of the same type design, this AD is being issued to prevent electrical failure of the microswitches in the engine fire pull switch assembly, which could result in the inability of the flight crew to shut down certain systems or to arm the fire extinguishers, or inadvertent shutdown of one or both engines. This AD requires an inspection to identify the serial numbers of the left-hand (pilot) and right-hand (copilot) engine fire pull switch assemblies, and replacement of any suspect assembly with a serviceable assembly. The actions are required to be accomplished in accordance with the alert service bulletins described previously.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 95-NM-178-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 USC 106(g), 40101, 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: