Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, that requires repetitive inspections to detect damage of certain taxi light assemblies, and replacement with a new or serviceable part, if necessary. This AD also requires eventual replacement of certain taxi light assemblies with improved parts, which constitutes terminating action for the repetitive inspections. This amendment is prompted by a report that a damaged taxi light detached from an airplane and was ingested into the airplane engines. The actions specified by this AD are intended to prevent damage to the taxi light assembly, which could result in detachment of the taxi light assembly from the airplane, ingestion of taxi light debris into an engine, and consequent loss of thrust from one or both engines.

EFFECTIVE DATE:

May 31, 2000.

ADDRESSES:

Information pertaining to this amendment may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

David Herron, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2672; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes was published in the Federal Register on May 10, 1999 (64 FR 24963). That action proposed to require repetitive detailed visual inspections to detect damage (including cracking, corrosion, deformation, or evidence of impact) of certain taxi light assemblies, and replacement with a new or serviceable part, if necessary. That action also proposed to require eventual replacement of certain taxi light assemblies with improved parts, which constitutes terminating action for the repetitive inspections.

Comments Received

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Support for the Proposal

One commenter supports the proposed rule. Another commenter considers the daily repetitive inspection interval to be unnecessarily restrictive, but has no objections to the proposed rule.

Requests To Extend Repetitive Inspection Interval

Two commenters request that the FAA extend the repetitive daily inspection interval for the visual inspection to detect damage of the taxi light assembly mounted on the nose landing gear of the airplane.

One commenter states that the daily inspection is redundant and the interval should be extended to every five days. The commenter states that, during the pre-flight walk-around, the flight crew checks the nose taxi light bracket prior to each flight. If damage is found, the flight crew notifies maintenance to correct the discrepancy.

Therefore, the commenter states that its suggested change would provide an equivalent level of safety to the daily inspections.

Another commenter states that a daily repetitive inspection is excessive and suggests a weekly inspection interval. The commenter justifies its request by stating that it has recently placed additional focus on proper towing procedures, which will “dramatically” reduce the potential for impact damage.

The FAA does not concur with the commenters' request. Inspections at a frequency of every five or seven days, instead of daily, reduce the opportunity for discovering damage and are not adequate to ensure that any damage is detected in a timely manner.

With regard to the first commenter's reference to the pre-flight walk-around performed by the flight crew, the FAA does not consider flight crews to be trained in the same manner as maintenance personnel to carry out the detailed visual inspections required by this AD. These expectations and definitions are contained within Parts 1 and 43 of the Federal Aviation Regulations (FAR) (14 CFR parts 1 and 43).

With regard to the second commenter's justification of additional focus on proper towing procedures, the FAA finds that there is no meaningful way to gauge the effectiveness of training procedures in mitigating the unsafe condition addressed in this AD. The FAA expects that the individuals who have been performing towing operations were properly trained; however, there have still been numerous incidents of damage to the taxi light assemblies.

In developing an appropriate repetitive interval for this action, the FAA considered the average utilization of the affected fleet (average of 7 flight cycles per day), the numerous reports of damaged taxi light assemblies, and the degree of urgency associated with addressing the subject unsafe condition. In consideration of all of these factors, the FAA has determined that daily inspections are appropriate to ensure that an acceptable level of safety can be maintained. No change to the final rule is necessary.

Request To Include Approved Repair

One commenter requests that an approved repair be included as a terminating action for the repetitive inspections. The commenter promotes repair as a cost effective means of compliance, but does not provide any reason why a repair would provide a level of safety equivalent to that achieved by accomplishment of the proposed AD.

The FAA does not concur with the commenter's request. The new taxi light assemblies listed in paragraph (c) of this AD as acceptable replacement parts differ from the taxi light assemblies that are the subject of this AD in both the dimensions of the part and the material from which the part is made. These design changes address the inherent failure mode associated with the unsafe condition (i.e., damaged taxi light assemblies due to towing operation practices and design deficiencies). However, repair of the taxi light assemblies subject to this AD would not affect the failure mode. No change to the final rule is necessary.

Request To Clarify Degree of Damage That Warrants Replacement

One commenter requests that the FAA clarify the degree of damage that warrants replacement of the light assembly, because minor superficial damage would not reduce the airworthiness of the assembly. The commenter provides no data or analysis beyond the statement made.

The FAA does not concur with the commenter's request. The FAA has defined the type of damage and level of inspection necessary in paragraph (a) of the AD. The FAA has determined that any damage found at this inspection level would decrease the safety of the aircraft to the point where replacement is necessary. No change to the final rule is necessary.

Clarification of the Term “Inspector”

One commenter requests clarification of the term “inspector” referenced in Note 2 of the NPRM. The commenter wants to know if this term refers to a job title or the person conducting the inspection.

The FAA concurs that clarification should be provided in this case. The term “inspector,” as used in the note, refers to the person performing the inspection. It is not intended as a job title and does not refer to a person with any special technical qualifications. The FAA notes that Part 43 of the FAR (14 CFR part 43) specifies who may perform maintenance. Note 2 of this final rule has been revised accordingly to clarify the term “inspector” as “the person performing the inspection.”

Request to Include Additional Instructions for Identification of Parts

One commenter recommends that the proposed AD include additional instructions or reference a Boeing or original equipment manufacturer document to assist in identification and reidentification of parts. The commenter states that many of the light assemblies will be difficult to identify due to part numbers “wearing off.” The commenter states that an alternative method of identifying parts would preclude unnecessary removals and inspections.

The FAA does not concur with the commenter's request. The FAA understands the difficulty the commenter may have in identifying which airplanes are configured with what parts. However, to develop procedures for identifying a part by a means other than part number would take time and would delay the issuance of this final rule. In consideration of the safety implications of the unsafe condition identified in this rule, the FAA finds that it would be inappropriate to delay the issuance of this rule in this way. The economic benefit that would be gained (by minimizing unnecessary inspections and replacements) does not outweigh the safety benefits that will be gained by implementing the requirements of this rule in a timely manner. In addition, considering the estimated time necessary for replacement of the taxi light assembly (2 hours), it may cost more in time and effort for operators to properly identify a part as needing replacement than to replace the part. Therefore, the FAA finds that it would be more efficient and cost effective to accomplish the requirements of the AD as proposed. No change to the final rule is necessary.

Comment on Use of Lights Identified in Parts Catalog

One commenter states that it has only authorized the use of light assemblies that are identified within the airplane manufacturer's illustrated parts catalog. However, the commenter makes no request for a specific change to the proposed rule and provides no justification for a change. Therefore, no change to the final rule is necessary in this regard.

Conclusion

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change described previously.

Cost Impact

There are approximately 2,857 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,159 airplanes of U.S. registry will be affected by this AD.

It will take approximately 1 work hour per airplane to accomplish the required inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $69,540, or $60 per airplane, per inspection cycle.

It will take approximately 2 work hours per airplane to accomplish the required replacement, at an average labor rate of $60 per work hour. Required parts will cost approximately $549 per airplane. Based on these figures, the cost impact of the replacement required by this AD on U.S. operators is estimated to be $775,371, or $669 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Regulatory Impact

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.

For the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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
• 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.

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

2000-08-17 Boeing: Amendment 39-11703. Docket 98-NM-253-AD.

Applicability: Model 737-100, -200, -300, -400, and -500 series airplanes; that are not equipped with a Grimes Aerospace taxi light assembly having part number (P/N) 50-0199-9, 50-0199-11, 50-0128-1A, 50-0128-1MA, 50-0128-3A, or 50-0128-3MA; 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 (d) 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 damage to the taxi light assembly, which could result in detachment of the taxi light from the airplane, ingestion of taxi light debris into an engine, and consequent loss of thrust from one or both engines; accomplish the following:

Initial and Repetitive Inspections

(a) Within 60 days after the effective date of this AD, perform a detailed visual inspection to detect damage (including cracking, corrosion, deformation, or evidence of impact) of the taxi light assembly mounted on the nose landing gear of the airplane. Repeat the inspection thereafter at intervals not to exceed 1 day, until the requirements of paragraph (c) have been accomplished.

Note 2:

For the purposes of this AD, a detailed visual inspection is defined as an intensive visual inspection of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of lighting at an intensity deemed appropriate by the inspector (i.e., the person performing the inspection). Inspection aids such as mirrors, magnifying glasses, etc., may be used. Surface cleaning and elaborate access procedures may be necessary.

Replacement

(b) If any damage of the taxi light assembly is detected during any inspection performed in accordance with paragraph (a) of this AD, prior to further flight, replace the existing taxi light assembly with a new or serviceable taxi light assembly in accordance with the applicable maintenance manual. If the existing taxi light assembly is replaced with a Grimes Aerospace taxi light assembly having P/N 50-0199-9, 50-0199-11, 50-0128-1A, 50-0128-1MA, 50-0128-3A, or 50-0128-3MA: no further action is required by this AD.

Terminating Action

(c) Within 2 years after the effective date of this AD: Replace the existing taxi light assembly with a Grimes Aerospace taxi light assembly having P/N 50-0199-9, 50-0199-11, 50-0128-1A, 50-0128-1MA, 50-0128-3A, or 50-0128-3MA; in accordance with the applicable maintenance manual. Such replacement constitutes terminating action for the repetitive inspection requirement of paragraph (a) of this AD.

Alternative Methods of Compliance

(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 nager, Seattle Aircraft Certification Office (ACO), FAA, Transport 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, Seattle ACO.

Note 3:

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

Special Flight Permits

(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.

Effective Date

(f) This amendment becomes effective on May 31, 2000.