Airworthiness Directives; Boeing Model 757 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-85-AD; Amendment 39-8956; AD 94-14-04]

Airworthiness Directives; Boeing Model 757 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that

is applicable to certain Boeing Model 757 series airplanes. This action

requires inspection to detect cracking of the lower spar chord of the

engine strut, removal of the stiffener straps from the mid-chord,

inspection of the fastener holes, and modification or repair. This

amendment is prompted by a report of cracking in the lower spar chord

of an engine strut. The actions specified in this AD are intended to

prevent cracking in the lower spar chord of the engine strut, which

could result in the inability of the strut to carry required engine

support loads.

DATES: Effective July 21, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of July 21, 1994.

Comments for inclusion in the Rules Docket must be received on or

before September 6, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 94-NM-85-AD, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056.

The service information referenced in this AD 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, 800 North Capitol Street, NW.,

suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Carrie Sumner, Aerospace Engineer,

Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle

Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056; telephone (206) 227-2778; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: Recently, the FAA received a report from an

operator that cracking was found in the lower spar chord of a strut on

a Boeing Model 757 series airplane equipped with a Rolls Royce Model

RB211-535 series engine. This cracking penetrated through the inboard

flange of the chord and propagated into the skin flange of the chord.

This fatigue crack in the skin flange was approximately five inches in

length.

Analysis indicates that stiffener straps, which were installed on

early production airplanes, increase the likelihood of cracking in the

spar chords. These stiffener straps are no longer installed on later

production airplanes.

Continued operation with the stiffener straps installed will cause

fatigue cracking or propagation of existing cracks in the lower chord.

Such cracking could result in the inability of the strut to carry

required engine support loads, and ultimately could lead to separation

of the engine from the strut.

The FAA has reviewed and approved Boeing Service Bulletin 757-54-

0028, dated March 31, 1994, that describes procedures for eddy current

inspection to detect cracking of the lower spar chord of the engine

strut, removal of the stiffener straps from the mid-chord, open hole

eddy current inspection of the fastener holes, and modification. This

modification, which includes installing fasteners, a strut pneumatic

duct, a fire extinguisher line, a bulkhead coverplate, and a panel,

will decrease the likelihood of fatigue cracking in the lower spar

chord of the engine strut.

Since an unsafe condition has been identified that is likely to

exist or develop on other Boeing Model 757 series airplanes of the same

type design, this AD is being issued to prevent cracking of the lower

spar chord of the engine strut. This AD requires eddy current

inspection to detect cracking of the lower spar chord of the engine

strut, removal of the stiffener straps from the mid-chord, open hole

eddy current inspection of the fastener holes, and modification. The

actions are required to be accomplished in accordance with the service

bulletin described previously. In certain cases, this AD requires

repair of cracking in accordance with an FAA-approved method.

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 94-NM-85-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 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. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-14-04 Boeing: Amendment 39-8956. Docket 94-NM-85-AD.

Applicability: Model 757 series airplanes having airplane line

numbers 2, 4, 5, 9 through 13 inclusive, 21, 26, 114, and 115,

certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent cracking in the lower spar chord of the engine strut,

which could result in the inability of the strut to carry required

engine support loads, accomplish the following:

(a) Within 60 days after the effective date of this AD, perform

an eddy current inspection to detect cracking of the lower chord, in

accordance with Boeing Service Bulletin 757-54-0028, dated March 31,

1994.

(b) If no cracking is detected during the inspection required by

paragraph (a) of this AD, prior to the accumulation of 1,500

landings after accomplishment of the inspection, remove the

stiffener straps from the mid-chord of the inboard and outboard

sides of the strut, and perform an open hole eddy current inspection

to detect cracking of the fastener holes in the mid-chord, in

accordance with Boeing Service Bulletin 757-54-0028, dated March 31,

1994.

(1) If no cracking is detected in the mid-chord strut during the

inspection required by paragraph (b) of this AD, prior to further

flight, modify in accordance with the service bulletin.

(2) If cracking is detected in the mid-chord strut during the

inspection required by paragraph (b) of this AD, prior to further

flight, repair in accordance with a method approved by the Manager,

Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane

Directorate.

(c) If cracking is detected during the inspection required by

paragraph (a) of this AD, prior to further flight, remove the

stiffener straps from the mid-chord of the inboard and outboard

sides of the strut, and perform an open hole eddy current inspection

to detect cracking of the fastener holes in the mid-chord, in

accordance with Boeing Service Bulletin 757-54-0028, dated March 31,

1994.

(1) If no cracking is detected in the mid-chord strut during the

inspection required by paragraph (c) of this AD, prior to further

flight, modify in accordance with the service bulletin.

(2) If cracking is detected in the mid-chord strut during the

inspection required by paragraph (c) of this AD, prior to further

flight, repair in accordance with a method approved by the Manager,

Seattle ACO, FAA, Transport Airplane Directorate.

(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, Seattle ACO. 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: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Seattle 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 inspections, strap removal, and modification shall be

done in accordance with Boeing Service Bulletin 757-54-0028, dated

March 31, 1994. 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, 800 North Capitol Street, NW., suite 700,

Washington, DC.

(g) This amendment becomes effective on July 21, 1994.

Issued in Renton, Washington, on June 23, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-15738 Filed 7-5-94; 8:45 am]

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