AD 2001-07-11

This amendment adopts a new airworthiness directive (AD) that is applicable to all Learjet Model 23, 24, 25, 28, 29, 31, 35, 36, and 55 series airplanes. This action requires an inspection to determine if tires on the main landing gear have a certain part number and certain serial numbers, and replacement with a tire having a part number that does not contain those certain serial numbers, if necessary. This action is necessary to prevent separation of the tread of main landing gear tires, which could cause damage to the structure and major systems of the airplane, and consequent reduced controllability of the airplane on the ground during takeoff and landing. This action is intended to address the identified unsafe condition.

Final rule; request for comments.

2001-07-11 LEARJET INC.: Amendment 39-12177. Docket 2001-NM-76-AD.

Applicability: All Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, 25F, 28, 29, 31, 31A, 35, 35A (C-21A military), 36, 36A, 55, 55B, and 55C airplanes; 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 request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent separation of the tread of main landing gear tires, which could cause damage to the structure and major systems of the airplane, and consequent reduced controllability of the airplane on the ground during takeoff and landing; accomplish the following:

Inspection, and Replacement If Necessary
(a) Within 5 days after the effective date of this AD: Perform a general visual inspection of the main landing gear tires to determine if any tire has Goodyear part number (P/N) 178K23-5 within the serial number range of 0148xxxx through 0152xxxx inclusive, per Bombardier (Learjet) Advisory Wire 32-021, dated February 5, 2001.

NOTE 2: For the purposes of this AD, a general visual inspection is defined as: "A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or drop-light, and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked."

NOTE 3: Bombardier (Learjet) AW 32-021 references Goodyear Service Bulletin GY SB 2001-32-001, dated February 2, 2001, as an additional source of service information.

(1) If no tires have P/N 178K23-5, no further actions is required by this paragraph.

(2) If any tire has P/N 178K23-5 but does not contain any serial number 0148xxxx through 0152 inclusive, no further action is required by this paragraph.

(3) If any tire has P/N 178K23-5 and does contain any serial number 0148xxxx through 0152xxxx inclusive: Before further flight, replace the tire with a new or serviceable tire that does not have P/N 178K23-5 with a serial number 0148xxxx through 0152xxxx inclusive.

(b) As of the effective date of this AD, no person shall install a main landing gear tire having P/N 178K23-5 that contains any serial number 0148xxxx through 0152xxxx inclusive, on any airplane.

Alternative Methods of Compliance
(c) 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). 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 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Wichita ACO.

Special Flight Permits
(d) 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 ADcan be accomplished.

Incorporation by Reference
(e) The inspection, and replacement if necessary, shall be done in accordance with Bombardier (Learjet) Advisory Wire 32-021, dated February 5, 2001. 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 Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 67209; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Effective Date
(f) This amendment becomes effective on May 1, 2001.

The FAA has received reports that certain main landing gear tires have lost the entire tread during takeoff or landing of Learjet Model 23, 24, 25, 28, 29, 31, 35, 36, and 55 series airplanes. Investigation by the tire manufacturer indicates that during manufacturing, a block of tires were processed that contained certain faults. The tire manufacturer has determined that tires having part number (P/N) 178K23-5 within the serial number range of 0148xxxx through 0152xxxx were affected. Separation of tire tread from the main landing gear tires could cause damage to the structure and major systems of the airplane, and consequent reduced controllability of the airplane on the ground during takeoff and landing.

Explanation of Relevant Service Information
Bombardier (Learjet) has issued Advisory Wire (AW), 32-021, dated February 5, 2001, which describes procedures for inspecting Goodyear Flight Eagle main landing gear tires to determine if a certain partnumber and certain serial numbers are installed. The AW also describes procedures to replace any of the specified tires with new or serviceable tires having a part number containing a serial number other than those specified in the AW. Accomplishment of the actions specified in the AW is intended to adequately address the identified unsafe condition.

The AW also references Goodyear Service Bulletin GY SB 2001-32-001, dated February 2, 2001, as an additional source of service information for accomplishment of the inspection, and replacement of main landing gear tires, if necessary.

Explanation of the Requirements of the Rule
Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to prevent damage to major systems of the airplane, and consequent reduced controllability of the airplane on the ground during takeoff and landing. This AD requires accomplishment of the actions specified in the AW described previously, except as discussed below.

Differences Between the Service Information and this AD
Operator's should note that, although the AW specifies that the inspection of the main landing gear tires, and replacement if necessary, should be accomplished "prior to next flight," this AD requires that those actions be accomplished within 5 days after the effective date of this AD. We find that a 5-day compliance time will provide the operator with a reasonable time to perform the inspection, but will not adversely affect the safety of the fleet.

Determination of Rule's Effective Date
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.

Submit comments using the following format:

Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.

For each issue, state what specific change to the AD is being requested.

Include justification (e.g., reasons or data) for each request.

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 2001-NM-76-AD." The postcard will be date stamped and returned to the commenter.

Regulatory Impact
The regulations adopted herein 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.

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 U.S.C. 106(g), 40113, 44701.

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