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RULES and REGULATIONS

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

(Docket No. 91-NM-214-AD; Amendment 39-8129; AD 91-22-51)

Airworthiness Directives; Boeing Model 757 Series Airplanes

Thursday, January 9, 1992

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

SUMMARY: This action publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 

91-22-51, which was made effective previously to all known U.S. owners and operators of Boeing Model 757 series 

airplanes by individual telegrams. This AD requires repetitive inspections to detect delamination of or physical 

damage to the trailing edge wedges on the leading edge wing slats, and repair, if necessary. This amendment is 

prompted by reports of skin separation on trailing edge wedges on wing leading edge slats. The actions specified by 

this AD are intended to prevent separation of one or more of the trailing edge wedges from the airplane, which could 

adversely affect the controllability of the airplane.

DATES: Effective January 24, 1992, to all persons except those persons to whom it was made immediately effective 

by telegraphic AD T91-22-51, issued October 17, 1991, which contained this amendment.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the 

Federal Register as of January 24, 1992.

ADDRESSES: The applicable service information may be obtained from Boeing Commercial Airplane Group, P.O. 

Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane 

Directorate, 1601 Lind Avenue SW., Renton, Washington; or at the Office of the Federal Register, 1100 L Street NW., 

Room 8401, Washington, DC.

FOR FURTHER INFORMATION CONTACT:Thomas Rodriguez, Aerospace Engineer, Airframe Branch, 

ANM-120S, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate, 1601 Lind Avenue SW., 

Renton, Washington 98055-4056; telephone (206) 227-2779.

SUPPLEMENTARY INFORMATION: On October 17, 1991, the FAA issued telegraphic AD T91-22-51, applicable 

to Boeing Model 757 series airplanes, which requires repetitive inspections to detect delamination of or physical 
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damage to the trailing edge wedges on the leading edge wing slats, and repair, if necessary. That action was prompted 

by reports from four operators of indications of skin separation of the upper skin on the forward part of the trailing 

edge wedge on a wing leading edge slats on five Model 757 series airplanes. On two of the slats, inboard pieces of the 

upper skin were lost from the wedge. This condition, if not corrected, could result in separation of one or more of 

trailing edge wedges from the airplane, which could adversely affect controllability of the airplane.

The FAA reviewed and approved Boeing Alert Service Bulletin 757-57A0045, dated October 16, 1991, which describes procedures for a close detailed visual inspection, followed by repetitive detailed visual and “coin-tap” inspections, of the trailing edge wedges on the wing leading edge slats to detect delamination and physical damage.

Since the unsafe condition described is likely to exist or develop on other airplanes of the same type design, the FAA 

issued telegraphic AD T91-22-51 to require repetitive close visual and “coin tap” inspections of the trailing edge 

wedges on the wing leading edge slats to detect delamination and physical damage. The required inspections are to be 

accomplished in accordance with the alert service bulletin previously described. If damage or defective parts are 

found, they must be repaired in accordance with an FAA-approved procedure or replaced with new parts.

Since it was found that immediate corrective action was required, notice and public procedure thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual 

telegrams issued on October 17, 1991, to all known U.S. owners and operators of Boeing Model 757 series airplanes. 

These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to § 39.13 of part 

39 of the Federal Aviation Regulations (FAR) to make it effective to all persons.

This is considered to be interim action until the manufacturer develops non-destructive inspection (NDI) procedures, 

at which time the FAA may consider further rulemaking.

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 and that it is not considered to be major under

Executive Order 12291. It is impracticable for the agency to follow the procedures of Order 12291 with respect to this 

rule since the rule must be issued immediately to correct an unsafe condition in aircraft. 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.
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Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration 

amends 14 CFR part 39 of the Federal Aviation Regulations as follows:

PART 39—(AMENDED)1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

14 CFR § 39.13

§ 39.13 (Amended)

14 CFR § 39.13

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

91-22-51. Boeing: Amendment 39-8129.Docket 91-NM-214-AD.

Applicability: Model 757 series airplanes, line numbers 140 through 335, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent the separation of the trailing edge wedges from the airplane, accomplish the following:

(a) Perform a close detailed visual inspection of the trailing edge wedges of slats 1 through 4 and 7 through 10, for 

delamination and physical damage in accordance with Boeing Alert Service Bulletin 757-57A0045, dated October 16, 

1991, at the times specified below:

(1) For airplanes that have accumulated 5,000 or more flight hours as of the effective date of this AD: Within the next 

10 calendar days after the effective date of this AD, and thereafter at intervals not to exceed 300 flight hours.

(2) For airplanes that have accumulated less than 5,000 flight hours as of the effective date of this AD: Within the next 

300 flight hours after the effective date of this AD, and thereafter at intervals not to exceed 300 flight hours.

(b) Within the next 300 flight hours after the effective date of this AD, perform a “coin-tap” inspection of the trailing 

edge wedges of slats 1 through 4 and 7 through 10 for delamination and physical damage, in accordance with Boeing 

Alert Service Bulletin 757-57A0045, dated October 16, 1991. Repeat this inspection at intervals not to exceed 1,500 

flight hours.
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(c) If delamination and/or physical damage are found as a result of the inspections required by paragraph (a) or (b) of 

this AD, prior to further flight, repair in accordance with an FAA-approved procedure or replace with new parts. If a 

repair is accomplished or if new parts are installed, the inspections required by paragraphs (a) and (b) of this AD must 

be continued.

(d) An alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of 

safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport 

Airplane Directorate.

Note: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO.

(e) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in 

order to comply with the requirements of this AD.

(f) The inspections required by this AD shall be done in accordance with Boeing Alert Service Bulletin 757-57A0045,

dated October 16, 1991. 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 Boeing Commercial Airplane 

Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane 

Directorate, 1601 Lind Avenue SW., Renton, Washington; or at the Office of the Federal Register, 1100 L Street NW., 

room 8401, Washington, DC.

(g) This amendment (39-8129), AD 91-22-51, becomes effective January 24, 1992, to all persons except those persons 

to whom it was made immediately effective by telegraphic AD T91-22-51, issued October 17, 1991, which contained 

the requirements of this amendment.

Issued in Renton, Washington, on December 18, 1991.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

57 FR 781