Airworthiness Directives; Boeing Model 747-100 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-27-AD]

Airworthiness Directives; Boeing Model 747-100 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to certain Boeing Model 747-

100 series airplanes, that currently requires repetitive inspections to

detect cracking of the wing front spar web above engine numbers 2 and

3, and repair, if necessary. This action would require repetitive

inspections to detect cracks in the web and cracked or broken fasteners

in an area beyond that specified in the existing AD. This action also

would provide an optional terminating action for the repetitive

inspections. This proposal is prompted by reports of broken fasteners

and cracking of the web common to the upper and lower chords in an area

outside the inspection zone specified in the existing AD. The actions

specified by the proposed AD are intended to prevent fuel leakage onto

an engine and a resultant fire due to cracking or broken fasteners in

the wing front spar.

DATES: Comments must be received by October 17, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-27-AD, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056. Comments may be inspected at this location

between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal

holidays.

The service information referenced in the proposed rule 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.

FOR FURTHER INFORMATION CONTACT: Tim Backman, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (206) 227-2776; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed 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 above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals contained in this notice may be changed in

light of the comments received.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket Number 94-NM-27-AD.'' The postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules

Docket No. 94-NM-27-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

On March 10, 1992, the FAA issued AD 92-07-11, amendment 39-8207

(57 FR 10415, March 26, 1992), applicable to certain Boeing Model 747-

100 series airplanes, to require inspections to detect cracking of the

wing front spar web above engine numbers 2 and 3, and repair, if

necessary. That action was prompted by a report of an 18-inch crack in

the front spar web at the attach fitting of the number 3 engine. The

requirements of that AD are intended to prevent fuel leakage onto an

engine and a resultant fire.

Since the issuance of that AD, the FAA has received reports of

broken fasteners and cracking in the fastener holes of the web common

to the upper and lower chords in areas outside the inspection zone

specified in AD 92-07-11. The airplanes on which these cracks and

broken fasteners were found had accumulated between 13,700 and 22,000

flight cycles. Based on these findings, the FAA has determined that

inspections to detect cracks and broken fasteners in an area beyond

that specified in AD 92-07-11 are necessary.

The FAA has reviewed and approved Boeing Alert Service Bulletin

747-57A2266, Revision 3, dated March 31, 1994, which describes

procedures for repetitive detailed visual inspections of the chords,

stiffeners, and rib posts between the fastener heads and ultrasonic

inspections to detect cracks of the wing front spar web between front

spar stations (FSS) 570 and 684. The alert service bulletin also

describes procedures for repetitive ultrasonic inspections of the

fasteners in the web-to-chords, web-to-stiffeners, and web-to-rib posts

to detect cracked or broken fasteners between FSS 570 and 684. For

those airplanes on which cracks or broken fasteners are found, the

alert service bulletin also describes procedures for oversizing

fastener holes, performing an eddy current inspection to detect

cracking of the fastener holes, and replacing cracked fasteners with

oversized fasteners. The alert service bulletin also describes

procedures for replacement of certain fasteners with oversized

fasteners, which, if accomplished, would eliminate the need for the

repetitive inspections.

Since an unsafe condition has been identified that is likely to

exist or develop on other products of this same type design, the

proposed AD would supersede AD 92-07-11 to require repetitive detailed

visual and ultrasonic inspections to detect cracks in an area beyond

that specified in the existing AD; and repetitive ultrasonic

inspections of the fasteners in the web-to-chords, web-to-stiffeners,

and web-to-rib posts to detect cracked or broken fasteners between FSS

570 and 684. If any cracked or broken fastener is found, this proposed

AD would require oversizing the fastener holes, performing an eddy

current inspection to detect cracking of the fastener holes, and

replacing cracked fasteners with oversized fasteners. This proposed AD

also would provide an optional terminating action for the repetitive

inspections. The actions would be required to be accomplished in

accordance with the alert service bulletin described previously.

There are approximately 190 Model 747-100 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 95

airplanes of U.S. registry would be affected by this proposed AD.

The inspections that were required previously by AD 92-07-11, and

retained in this AD, take approximately 16 work hours per airplane to

accomplish, at an average labor rate of $55 per work hour. Based on

these figures, the total cost impact of that inspection requirement on

U.S. operators is estimated to be $83,600, or $880 per airplane, per

inspection cycle.

The FAA estimates that it would take approximately 54 work hours

per airplane to accomplish the proposed inspections of the expanded

area specified in this AD, and that the average labor rate is $55 per

work hour. Based on these figures, the future total cost impact of the

inspection requirement of the expanded zone on U.S. operators is

estimated to be $282,150, or $2,970 per airplane.

Based on these figures, the total cost impact of the proposed AD on

U.S. operators is estimated to be $365,750, or $3,850 per airplane.

The total cost impact figure discussed above is based on

assumptions that no operator has yet accomplished any of the proposed

requirements of this AD action, and that no operator would accomplish

those actions in the future if this AD were not adopted.

Should an operator elect to accomplish the optional terminating

action (fastener replacement between FSS 570 and FSS 684) that would be

provided by this AD action, it would take approximately 306 work hours

to accomplish it, at an average labor rate of $55 per work hour. The

cost of required parts would be provided by the manufacturer at no cost

to operators. Based on these figures, the total cost impact of the

optional terminating action would be $16,830 per airplane.

The regulations proposed herein would 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

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

regulation (1) is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, 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 copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend

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 removing amendment 39-8207 (57 FR

10415, March 26, 1992), and by adding a new airworthiness directive

(AD), to read as follows:

Boeing: Docket 94-NM-27-AD. Supersedes AD 92-07-11, Amendment 39-

8207.

Applicability: Model 747-100 series airplanes; as listed in

Boeing Alert Service Bulletin 747-57A2266, Revision 3, dated March

31, 1994; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent fuel leakage onto an engine and a resultant fire,

accomplish the following:

Restatement of Actions Required by AD 92-07-11, Amendment 39-

8207:

(a) For airplanes listed in Boeing Alert Service Bulletin 747-

57A2266, dated June 6, 1991, on which the optional terminating

action (fastener replacement) specified in the original issue, dated

June 6, 1991; Revision 1, dated May 21, 1992; or Revision 2, dated

June 10, 1993; of the alert service bulletin has not been

accomplished: Perform a visual inspection and an ultrasonic

inspection to detect cracks of the wing front spar web between front

spar station (FSS) 636 and FSS 675 in accordance with Boeing Alert

Service Bulletin 747-57A2266, dated June 6, 1991; Revision 1, dated

May 21, 1992; Revision 2, dated June 10, 1993; or Revision 3, dated

March 31, 1994; at the time specified in paragraph (a)(1), (a)(2),

or (a)(3) of this AD, as applicable. Repeat these inspections

thereafter at intervals not to exceed 2,000 flight cycles until the

inspections required by paragraph (b) of this AD are accomplished.

(1) For airplanes that have accumulated more than 20,000 total

flight cycles as of May 4, 1992 (the effective date of AD 92-07-11,

amendment 39-8207): Inspect within 6 months after May 4, 1992.

(2) For airplanes that have accumulated between 15,000 and

20,000 total flight cycles as of May 4, 1992: Inspect within 15

months after May 4, 1992.

(3) For airplanes that have accumulated less than 15,000 total

flight cycles as of May 4, 1992: Inspect within 15 months after

accumulating 15,000 total flight cycles.

New Actions Required by This AD:

(b) For airplanes on which the terminating action (fastener

replacement) specified in Boeing Alert Service Bulletin 747-57A2266,

dated June 6, 1991; Revision 1, dated May 21, 1992; or Revision 2,

dated June 10, 1993; has not been accomplished: Prior to the

accumulation of 13,000 total flight cycles, or within 6 months after

the effective date of this AD, or within 1,000 flight cycles after

the immediately preceding inspection accomplished in accordance with

paragraph (a) of this AD, whichever occurs later, accomplish the

inspections specified in paragraphs (b)(1), (b)(2), and (b)(3) of

this AD in accordance with Boeing Alert Service Bulletin 747-

57A2266, Revision 3, dated March 31, 1994. Repeat these inspections

thereafter at intervals not to exceed 2,000 flight cycles.

Accomplishment of these inspections terminates the inspections

required by paragraph (a) of this AD. After the effective date of

this AD, the inspections required by this paragraph shall be

accomplished only in accordance with Revision 3 of the alert service

bulletin.

(1) Perform a detailed visual inspection of the chords,

stiffeners, and rib posts between the fastener heads; and

(2) Perform an ultrasonic inspection of the web under the upper

and lower chord footprints to detect cracking of the wing front spar

web between FSS 570 and FSS 684; and

(3) Perform an ultrasonic inspection of the fasteners in the

web-to-chords, web-to-stiffeners, and web-to-rib posts to detect

cracked or broken fasteners between FSS 570 and FSS 684. -

(c) For airplanes on which the terminating action (fastener

replacement) specified in Boeing Alert Service Bulletin 747-57A2266,

dated June 6, 1991; Revision 1, dated May 21, 1992; or Revision 2,

dated June 10, 1993; has been accomplished: Within 18 months after

accomplishing the terminating action specified in the original

issue, Revision 1, or Revision 2 of the alert service bulletin, or

within 9 months after the effective date of this AD, whichever

occurs later, accomplish the inspections specified in paragraphs

(c)(1), (c)(2), and (c)(3) of this AD in accordance with Boeing

Alert Service Bulletin 747-57A2266, Revision 3, dated March 31,

1994. Repeat these inspections thereafter at intervals not to exceed

2,000 flight cycles. After the effective date of this AD, the

inspections required by this paragraph shall be accomplished only in

accordance with Revision 3 of the alert service bulletin.

(1) Perform a detailed visual inspection of the chords,

stiffeners, and rib posts between the fastener heads; and -

(2) Perform an ultrasonic inspection of the web under the upper

and lower chord footprints to detect cracking of the wing front spar

web between FSS 570 and FSS 636 and between FSS 675 and FSS 684; and

(3) Perform an ultrasonic inspection of the fasteners in the

web-to-chords, web-to-stiffeners, and web-to-rib posts to detect

cracked or broken fasteners between FSS 570 and FSS 636 and between

FSS 675 and 684. -

(d) If any crack in the web or any cracked or broken fastener is

found during any inspection required by this AD, prior to further

flight, oversize the fastener hole, perform an eddy current

inspection to detect cracks in the fastener hole, and replace the

fastener with an oversized fastener, in accordance with Boeing Alert

Service Bulletin 747-57A2266, Revision 3, dated March 31, 1994.

Thereafter, continue to inspect the remaining fasteners in

accordance with paragraph (b) or (c) of this AD, as applicable,

until the terminating action specified in paragraph (e) of this AD

is accomplished. If any crack is found that cannot be removed by

oversizing the fastener hole, prior to further flight, repair in

accordance with a method approved by the Manager, Seattle Aircraft

Certification Office (ACO), FAA, Transport Airplane Directorate.

(e) Replacement of the fasteners in the web-to-chords and of the

fasteners in the web-to-stiffeners and web-to-rib posts, as

specified in Boeing Alert Service Bulletin 747-57A2266, Revision 3,

dated March 31, 1994, with oversized fasteners on each wing spar in

accordance with the alert service bulletin constitutes terminating

action for the repetitive inspections required by paragraph (b) and

(c) of this AD.

(f) 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.

(g) 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.

Issued in Renton, Washington, on August 17, 1994.

James V. Devany,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-20593 Filed 8-22-94; 8:45 am]

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