Airworthiness Directives; Boeing Model 747 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-204-AD]

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 inspections to detect cracking

in the upper row of fasteners in the lower lobe of the fuselage skin

lap joints, and repair, if necessary. This proposal is prompted by

reports of incidents involving fatigue cracking and corrosion in

transport category airplanes that are approaching or have exceeded

their design life goal. The actions specified by the proposed AD are

intended to prevent separation of the fuselage skin and rapid loss of

pressure in the airplane. This proposal also relates to the

recommendations of the Airworthiness Assurance Task Force assigned to

review Model 747 series airplanes, which indicate that, to assure long

term continued operational safety, various structural inspections

should be accomplished.

DATES: Comments must be received by May 9, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 93-NM-204-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056. Comments may be inspected at this

location between 9 a.m. and 3 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: Steven C. Fox , Aerospace Engineer,

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

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

Washington 98055-4056; telephone (206) 227-2777; 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 93-NM-204-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. 93-NM-204-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

In April 1988, a transport category airplane managed to land after

cracks in rivet holes in the upper fuselage linked together, causing

structural failure and uncontrolled decompression. An 18-foot section

ripped from the fuselage. This accident focused greater attention on

the problem of aging aircraft.

In June 1988, the FAA sponsored a conference on aging airplane

issues, which was attended by representatives of the aviation industry

from around the world. It became obvious that, because of the

tremendous increase in air travel, the relatively slow pace of new

airplane production, and the apparent economic feasibility of operating

older technology airplanes rather than retiring them, increased

attention needed to be focused on this aging fleet and maintaining its

continued operational safety.

The Air Transport Association (ATA) of America and the Aerospace

Industries Association (AIA) of America committed to identifying and

implementing procedures to ensure continuing structural airworthiness

of aging transport category airplanes. An Airworthiness Assurance Task

Force, with representatives from the aircraft operators, manufacturers,

regulatory authorities, and other aviation representatives, was

established in August 1988. The objective of the Task Force was to

sponsor ``Working Groups'' to:

1. Select service bulletins, applicable to each airplane model in

the transport fleet, to be recommended for mandatory modification of

aging airplanes,

2. Develop corrosion directed inspections and prevention programs,

3. Review the adequacy of each operator's structural maintenance

program,

4. Review and update the Supplemental Structural Inspection

Documents (SSID), and

5. Assess repair quality.

The Working Group assigned to review the Boeing Model 747 series

airplanes completed its work on Item 2 in July 1989 and developed a

baseline program for controlling corrosion problems that may jeopardize

the continued airworthiness of the Boeing Model 747 fleet. This program

is contained in Boeing Document Number D6-36022, ``Aging Airplane

Corrosion Prevention and Control Program--Model 747,'' dated July 1989.

The FAA issued AD 90-25-05, Amendment 39-6790 (55 FR 49268, November

27, 1990), which requires implementation of a corrosion prevention and

control program.

The Working Group completed a portion of its work on Item 1, above.

The Working Group's proposal is contained in Boeing Document Number D6-

35999, ``Aging Airplane Service Bulletin Structural Modification

Program--Model 747.'' The FAA issued AD 90-06-06, Amendment 39-6490 (55

FR 8374, March 7, 1990), which requires the installation of the

structural modifications identified in the Boeing Document, and AD 92-

27-04, Amendment 39-8437 (58 FR 8693, February 17, 1993), which

requires structural inspections of older airplanes.

Additional structural inspections are required by AD 86-09-07 R1,

Amendment 39-5580 (52 FR 7564, March 12, 1987), which references Boeing

Alert Service Bulletin 747-53A2267, dated March 28, 1986, and Revision

1, dated September 25, 1986.

The action being proposed herein follows from the ongoing

activities of the Working Group relative to Item 1. The Working Group

has identified certain service difficulties that warrant mandatory

inspections following mandatory modification of these airplanes. The

Working Group considers that these service difficulties can be

controlled safely by repetitively inspecting following modification of

these airplanes, and that, because of the safety implications, the

inspections should be mandatory to assure that all operators perform

them. Typically, the addressed unsafe conditions have occurred

infrequently on older airplanes, and the Working Group has a very high

degree of confidence in the ability of an inspection program to detect

the damage before it impairs safety.

The Working Group has reviewed Boeing Service Bulletin 747-53A2267,

and has recommended it to the FAA for mandatory inspection following

modification to ensure the successful long-term operation of Model 747

series airplanes. The procedures contained in this service bulletin

address reports of corrosion and cracking in the body skin of the lap

joints under the wing-to-body fairing on Model 747 series airplanes

that had accumulated between 21,500 flight hours and 33,000 flight

hours. Operators have also reported finding corrosion and cracks at the

lower body lap joints forward and aft of the wing-to-body fairing on

airplanes that had accumulated more than 9,000 flight hours.

Additionally, operators have reported finding fatigue cracking in the

body frames adjacent to the lap joints on airplanes that had

accumulated more than 10,000 flight cycles. Continued operation of

these airplanes with corroded lap joints and cracked or broken adjacent

frames could cause the skin to separate, which could lead to rapid loss

of pressure in the airplane.

The FAA has concurred with the Working Group's recommendations and

has determined that AD action is warranted to mandate the inspections

to assure the continued airworthiness of the Model 747 fleet.

The FAA has reviewed and approved Revision 3 of Boeing Service

Bulletin 747-53A2267, dated March 26, 1992, that describes procedures

for external high frequency eddy current (HFEC) inspections to detect

cracking in the upper row of fasteners in the lower lobe of the

fuselage skin lap joints. Certain inspections to detect cracking of the

lower lobe lap joints described in this service bulletin are required

by AD 86-09-07 R1, which references the original issue of this service

bulletin, dated March 8, 1986, and Revision 1, dated September 25,

1986. The ``full'' modification (including the ``permanent'' repair)

and the ``optional'' modification of the lower lobe lap joints

described in this service bulletin are required by AD 90-06-06, which

also references both the original issue of this service bulletin and

Revision 1. The inspections to detect corrosion described in this

service bulletin are required by AD 90-25-05, Amendment 39-6790 (55 FR

49268, November 27, 1990).

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 repetitive external high frequency eddy

current inspections to detect cracking in the upper row of fasteners in

modified lap joints, and repair, if necessary. The inspections would be

required to be accomplished in accordance with the service bulletin

described previously.

The requirements of this proposed AD are not intended to duplicate,

rescind, or supersede the requirements of AD 86-09-07 R1, AD 90-06-06,

or AD 90-25-05. The FAA's intent is to require the external HFEC

inspections, described above, of older airplanes following the

mandatory modifications required by AD 90-06-06, in addition to those

inspections required by AD 86-09-07 R1 and AD 90-25-05.

There are approximately 200 Model 747 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 118

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

it would take approximately 124 work hours per airplane to accomplish

the proposed actions, and that the average labor rate is $55 per work

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

on U.S. operators is estimated to be $804,760, or $6,820 per airplane.

This total cost figure assumes that no operator has yet accomplished

the proposed requirements of this AD action.

The FAA recognizes that the proposed inspections would require a

large number of work hours to accomplish. However, the compliance times

specified in paragraph (a) of this proposed AD should allow ample time

for the inspections to be accomplished coincidentally with scheduled

major airplane inspection and maintenance activities, thereby

minimizing the costs associated with special airplane scheduling.

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 14

CFR part 39 of the Federal Aviation Regulations 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:

Boeing: Docket 93-NM-204-AD.

Applicability: Model 747 series airplanes having line positions

1 through 200 inclusive; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent separation of fuselage skin and rapid loss of

pressure in the airplane, accomplish the following: (a) Perform an

external high frequency eddy current inspection to detect cracks in

the upper row of fasteners in the modified lap joints in accordance

with Boeing Service Bulletin 747-53A2267, Revision 3, dated March

26, 1992, at the time specified in paragraph (a)(1) or (a)(2) or

(a)(3) of this AD, as applicable.

(1) For airplanes on which the full modification required by AD

90-06-06, Amendment 39-6490, has been accomplished in accordance

with Revision 2 of Boeing Service Bulletin 747-53A2267, dated March

29, 1990, or Revision 3, dated March 26, 1992: Prior to the

accumulation of 10,000 flight cycles after accomplishment of the

full modification.

(2) For airplanes on which the full modification required by AD

90-06-06, Amendment 39-6490, has been accomplished in accordance

with Boeing Service Bulletin 747-53A2267, dated March 8, 1986, or

Revision 1, dated September 25, 1986: Prior to the accumulation of

7,000 flight cycles after accomplishment of the full modification.

(3) For airplanes on which the optional modification has been

accomplished in accordance with Boeing Service Bulletin 747-53A2267,

dated March 28, 1986; or Revision 1, dated September 25, 1986; or

Revision 2, dated March 29, 1990; or Revision 3, dated March 26,

1992: Prior to the accumulation of 7,000 flight cycles after

accomplishment of the optional modification.

(b) If no cracking is detected, repeat these inspections

thereafter at intervals not to exceed 3,000 flight cycles.

(c) If any cracking is detected, prior to further flight, repair

in accordance with the Section 53-30-03 of the 747 Structural Repair

Manual, and repeat these inspections thereafter at intervals not to

exceed 3,000 flight cycles.

(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 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: 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

Federal Aviation Regulations (FAR) 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 March 8, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-5853 Filed 3-11-94; 8:45 am]

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