Airworthiness Directives; Boeing Model 747 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-282-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness

directive. (AD) that is applicable to certain Boeing Model 747 series

airplanes. This proposal would require repetitive inspections to detect

broken fasteners and cracking of the forward edge frame for main entry

door number 3, and repair, if necessary. This proposal is prompted by

reports of fatigue cracks at the inner chord and web of the body

station 1265 edge frame between stringers 23 and 27. The actions

specified by the proposed AD are intended to detect and correct such

cracking, which could result in rapid depressurization of the airplane.

DATES: Comments must be received by October 4, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-114,

Attention: Rules Docket No. 98-NM-282-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: Robert Breneman, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (425) 227-2776; fax (425) 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.

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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 98-NM-282-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-114, Attention: Rules

Docket No. 98-NM-282-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA has received reports indicating that fatigue cracking has

been detected in the frame web and frame inner chord at stringer 26 at

body station 1265. In addition, one report indicates that, on one

airplane, the fuselage frame web and frame inner chord had severed

above stringer 24 near the top of a frame inner chord reinforcement

strap. This frame is the forward edge frame for main entry door number

3. Such fatigue cracking, if not detected and corrected in a timely

manner, could result in rapid depressurization of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin

747-53A2416, Revision 1, dated May 6, 1999, which describes procedures

for repetitive inspections to detect broken fasteners and cracking of

the forward edge frame for main entry door number 3, and repair, if

necessary. The inspection of the frames at the floor intercostal

includes a detailed visual inspection for broken fasteners, an open

hole high frequency eddy current (HFEC) inspection of certain fasteners

in the frame inner chord to detect cracking, and a surface HFEC

inspection of the frame web to detect cracking. For certain airplanes,

the service bulletin recommends a surface HFEC inspection and an open

hole HFEC inspection of the frames at the top of the inner chord

reinforcement strap to detect cracking. Accomplishment of the actions

specified in the alert service bulletin is intended to adequately

address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

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 require accomplishment of the actions specified in

the alert service bulletin described previously, except as discussed

below.

Differences Between Alert Service Bulletin and This AD

Operators should note that, although the alert service bulletin

specifies that the manufacturer may be contacted for repair data for

cracking conditions, this AD requires the repair of those conditions to

be accomplished in accordance with a method approved by the FAA, or in

accordance with data meeting the type certification basis of the

airplane approved by a Boeing Company Designated Engineering

Representative who has been authorized by the FAA to make such

findings.

The alert service bulletin also indicates that a modification to

the frame and lateral intercostal can be made that will increase the

interval between frame inspections, and that the procedures for such a

modification will be included in a subsequent revision to the alert

service bulletin. Any modification incorporated to increase the

interval between inspections or as terminating action for the

inspections must be approved as an alternative method of compliance in

accordance with paragraph (d) of this AD.

Cost Impact

There are approximately 1,182 airplanes of the affected design in

the worldwide fleet. The FAA estimates that 251 airplanes of U.S.

registry would be affected by this proposed AD.

It would take approximately 1 work hour per airplane to accomplish

the proposed inspection of the frames at the floor intercostal, at an

average labor rate of $60 per work hour. Based on these figures, the

cost impact of this proposed inspection on U.S. operators is estimated

to be $15,060, or $60 per airplane, per inspection cycle.

The FAA estimates that the proposed inspection of the frames at the

top of the inner chord reinforcement strap would be required to be

accomplished on 103 U.S.-registered airplanes. It would take

approximately 1 work hour per airplane to accomplish the proposed

inspection, at an average labor rate of $60 per work hour. Based on

these figures, the cost impact of this proposed inspection on U.S.

operators is estimated to be $6,180, or $60 per airplane, per

inspection cycle.

The cost impact figures discussed above are 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.

Regulatory Impact

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. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

Boeing: Docket 98-NM-282-AD.

Applicability: Model 747 series airplanes, as listed in Boeing

Alert Service Bulletin 747-53A2416, Revision 1, dated May 6, 1999;

certificated in any category.

Note 1: This AD applies to airplanes that have been converted

from a passenger configuration to a special freighter configuration.

Note 2: This AD applies to each airplane identified in the

preceding applicability provision, regardless of whether it has been

[[Page 45468]]

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 detect and correct cracking of the inner chord and web of the

body station 1265 edge frame between stringers 23 and 27, which

could result in rapid depressurization of the airplane, accomplish

the following:

Inspections

(a) Accomplish the flight safety inspections of the frames at

the floor intercostal to detect broken fasteners and cracking, in

accordance with Figure 5 of Boeing Alert Service Bulletin 747-

53A2416, Revision 1, dated May 6, 1999, at the applicable time

specified in paragraph (a)(1), (a)(2), or (a)(3) of this AD. Repeat

the inspection thereafter at intervals not to exceed 3,000 flight

cycles.

Note 3: Figure 5 of the alert service bulletin includes a

detailed visual inspection for broken fasteners, an open hole high

frequency eddy current (HFEC) inspection of certain fasteners in the

frame inner chord to detect cracking, and a surface HFEC inspection

of the frame web to detect cracking.

Note 4: For the purposes of this AD, a detailed visual

inspection is defined as: ``An intensive visual examination 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 good lighting at

intensity deemed appropriate by the inspector. Inspection aids such

as mirror, magnifying lenses, etc., may be used. Surface cleaning

and elaborate access procedures may be required.''

Note 5: The alert service bulletin gives instructions to perform

an open hole inspection, but does not give instructions to oversize

the fastener hole after the inspection. This will keep sufficient

material to oversize the hole at a later date when the modification

work is accomplished.

(1) For airplanes that have accumulated fewer than 10,000 total

flight cycles as of the effective date of this AD: Inspect prior to

the accumulation of 10,000 total flight cycles, or within 1,000

flight cycles after the effective date of this AD, whichever occurs

later.

(2) For airplanes that have accumulated between 10,000 and

20,000 total flight cycles as of the effective date of this AD:

Inspect prior to the accumulation of 11,000 total flight cycles, or

within 750 flight cycles after the effective date of this AD,

whichever occurs later.

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

flight cycles as of the effective date of this AD: Inspect prior to

the accumulation of 20,750 total flight cycles, or within 500 flight

cycles after the effective date of this AD, whichever occurs later.

(b) For Group 1 airplanes, as identified in Boeing Alert Service

Bulletin 747-53A2416, Revision 1, dated May 6, 1999, on which the

extended chord reinforcement strap modification specified in Boeing

Service Bulletin 747-53-2066, dated June 28, 1972, has not been

accomplished or on which the extended chord reinforcement strap

modification was accomplished after the accumulation of 10,000 total

flight cycles: Accomplish the surface HFEC inspection and the open

hole HFEC inspection, as applicable, of the frames at the top of the

inner chord reinforcement strap to detect cracking, in accordance

with Figure 6 of the alert service bulletin at the applicable time

specified in either paragraph (b)(1) or (b)(2) of this AD. Repeat

the inspection thereafter at intervals not to exceed 800 flight

cycles.

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

cycles or fewer as of the effective date of this AD: Inspect prior

to the accumulation of 16,000 total flight cycles, or within 500

flight cycles after the effective date of this AD, whichever occurs

later.

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

flight cycles as of the effective date of this AD: Inspect prior to

the accumulation of 20,500 total flight cycles, or within 250 flight

cycles after the effective date of this AD, whichever occurs later.

Repair

(c) If any broken fastener or cracking is detected during the

inspections required by paragraph (a) or (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; or in accordance with data meeting the type

certification basis of the airplane approved by a Boeing Company

Designated Engineering Representative who has been authorized by the

Manager, Seattle ACO, to make such findings. For a repair method to

be approved by the Manager, Seattle ACO, as required by this

paragraph, the Manager's approval letter must specifically reference

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 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 6: 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

Secs. 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 16, 1999.

D. L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-21693 Filed 8-19-99; 8:45 am]

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