Airworthiness Directives; Boeing Model 727 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-323-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 727 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 727

series airplanes, that currently requires repetitive inspections of the

front spar web between the upper and lower seals of the center section

of the wings, and repair, if necessary. That AD also provides for an

optional terminating modification for the repetitive inspections. This

action would require a new terminating modification for the repetitive

inspections. For certain airplanes, this action would require new

repetitive inspections to detect discrepancies of the front spar web.

This proposal is prompted by a report indicating that the optional

terminating modification in the existing AD does not address the

identified unsafe condition. The actions specified by the proposed AD

are intended to prevent fatigue cracks in the front spar web, which

could lead to fuel leakage into the air-conditioning distribution bay

and/or depressurization of the cabin, and to prevent fuel fumes in the

cabin of the airplane.

DATES: Comments must be received by September 24, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 97-NM-323-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: Walter Sippel, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (425) 227-2774; 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.

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 97-NM-323-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. 97-NM-323-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

On December 21, 1989, the FAA issued AD 90-02-16, amendment 39-6452

(55 FR 602, January 8, 1980), applicable to certain Boeing Model 727

series airplanes, to require inspection of the front spar web of the

center section of the wings, and repair, if necessary. That action was

prompted by reports of cracks in the front spar web. The requirements

of that AD are intended to detect and correct such cracking, which

could lead to fuel leakage and/or depressurization of the cabin.

Actions Since Issuance of Previous Rule

Since issuance of AD 90-02-16, the FAA has received a report

indicating that modification procedures specified in Boeing Service

Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated

November 21, 1991; and Revision 2, dated September 16, 1993; do not

adequately address airplanes equipped with internal fuel tanks in the

center section of the wings. Specifically, the service bulletin does

not include procedures for application of the secondary fuel seal on

the forward side of the front spar and on the fillet seals on the aft

side of the front spar. The service bulletin also describes procedures

for the application of sealant Boeing material specification (BMS) 5-95

inside the fuel tank instead of the fuel-proof sealant BMS 5-26, and

the installation of non-fluid tight fasteners instead of fluid tight

fasteners.

Boeing Service Bulletin 727-57-0177, dated December 22, 1988, was

referenced in AD 90-02-16 as the appropriate source of service

information for accomplishment of the required modification and close

visual and high frequency eddy current (HFEC) inspections. Revisions 1

and 2 of that service bulletin were approved by the FAA as alternative

methods of compliance for accomplishment of those actions.

[[Page 43319]]

In light of this information, the FAA has determined that the

optional modification specified in AD 90-02-16 does not adequately

preclude fuel leakage into the air-conditioning distribution bay, which

could result in fuel fumes in the cabin of the airplane.

In addition, the FAA finds that the subject service bulletin does

not contain procedures for accomplishing an HFEC inspection as an

option to the close visual inspection, as required by paragraph A. of

AD 90-02-16. The actual procedures used to accomplish that HFEC

inspection and the effectiveness of those procedures are unknown to the

FAA. The FAA has determined that performing an HFEC inspection in

accordance with an unknown procedure does not ensure that cracks will

be detected in a timely manner. Therefore, the FAA has determined that

all affected airplanes must accomplish repetitive detailed visual

inspections to ensure that cracks are detected in a timely manner.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 727-57-

0177, Revision 3, dated February 15, 1996, which describes procedures

for repetitive detailed visual inspections to detect cracks of the

front spar web between the upper and lower seals of the center section

of the wings, and repair, if necessary. The service bulletin also

describes procedures for modification of the front spar web between the

upper and lower seals of the center section of the wings, which would

eliminate the need for the repetitive inspections. For certain

airplanes, the service bulletin describes procedures for repetitive

visual inspections of the front spar web to detect fuel leakage and

penetrations in the secondary fuel barrier, and to verify the

installation of the secondary fuel barrier. Accomplishment of the

actions specified in the service bulletin are 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 supersede AD 90-02-16, amendment 39-6452 (55 FR 602,

January 8, 1980), to continue to require repetitive detailed visual

inspections of the front spar web between the upper and lower seals of

the center section of the wings, and repair, if necessary. The proposed

AD also would require modification of the subject front spar web, which

would constitute terminating action for the repetitive inspections. For

certain airplanes, the proposed AD would require repetitive visual

inspections of the front spar web to detect fuel leakage and

penetrations in the secondary fuel barrier, and to verify the

installation of the secondary fuel barrier. The actions would be

required to be accomplished in accordance with the service bulletin

described previously; except as discussed below.

The FAA has determined that, for airplanes equipped with integral

fuel tanks in the center section of the wings, the repairs and

modifications specified in Figure 2 and Figure 3 of Boeing Service

Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated

November 21, 1991; and Revision 2, dated September 16, 1993; do not

describe procedures for installation of a fuel proof sealant in these

tanks, which could lead to identified unsafe condition of this AD. The

procedures specified in the original version, Revision 1, and Revision

2 of the service bulletin are acceptable for airplanes without integral

fuel tanks in the center section of the wings. However, the FAA finds

that Revision 3 of the subject service bulletin does provide procedures

for installation of a fuel proof sealant for integral fuel tanks.

Other Relevant Rulemaking

The FAA has previously issued AD 94-05-04, amendment 39-8842 (59 FR

13442, March 22, 1994), which requires incorporation of certain

structural modification on certain Boeing Model 747 series airplanes.

Accomplishment of certain actions required by this proposed AD would

constitute terminating action for the requirements specified in

paragraph (a) of AD 94-05-04 with respect to the modification specified

in Boeing Service Bulletin 727-57-0177, dated December 22, 1998. This

service bulletin is one of many service bulletins referenced in Boeing

Document D6-54860, Revision G, Appendix A.3, dated March 5, 1993. All

other service bulletins referenced in that document still apply.

Cost Impact

There are approximately 1,524 Model 727 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 1,098

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

The detailed visual inspection that is currently required by AD 90-

02-16, and retained in this AD, takes approximately 3 work hours per

airplane to accomplish, at an average labor rate of $60 per work hour.

Based on these figures, the cost impact of the currently required

detailed visual inspection on U.S. operators is estimated to be

$197,640, or $180 per airplane, per inspection cycle.

The modification that is proposed in this new AD action would take

approximately 360 work hours per airplane to accomplish, at an average

labor rate of $60 per work hour. Required parts would cost

approximately $1,430 per airplane. Based on these figures, the cost

impact of the proposed modification required by this AD on U.S.

operators is estimated to be $25,286,940, or $23,030 per airplane.

For certain airplanes, the visual inspection that is proposed in

this new AD action would take approximately 1 work hour per airplane to

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

these figures, the cost impact of the proposed modification required by

this AD on U.S. operators is estimated to be $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 current or 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.

[[Page 43320]]

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 removing amendment 39-6452 (55 FR

602, January 8, 1990), and by adding a new airworthiness directive

(AD), to read as follows:

Boeing: Docket 97-NM-323-AD. Supersedes AD 90-02-16, Amendment 39-

6452.

Applicability: Model 727 series airplanes, as listed in Boeing

Service Bulletin 727-57-0177, dated December 22, 1988; certificated

in any category.

Note 1: This AD applies to each airplane identified in the

preceding applicability provision, regardless of whether it has been

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 (g)(1)

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 prevent fatigue cracks of the front spar web of the center

section of the wings, which could lead to fuel leakage and/or

depressurization of the cabin, or to prevent fuel fumes in the cabin

of the airplane, accomplish the following:

Repetitive Detailed Visual Inspections

(a) For areas on which the front spar web between the upper and

lower seals of the center section of the wings has not been repaired

or modified in accordance with Figure 2 or 3 of Boeing Service

Bulletin 727-57-0177, dated December 22, 1988; Revision 1, dated

November 21, 1991; or Revision 2, dated September 16, 1993: Prior to

the accumulation of 40,000 total flight cycles, or with the next

2,300 flight cycles after February 12, 1990 (effective date of AD

90-02-16, amendment 39-6452), whichever occurs later, unless

accomplished with the last 700 flight cycles, perform a detailed

visual inspection to detect cracks in the front spar web, in

accordance with Figure 1 of Boeing Service Bulletin 727-57-0177,

dated December 22, 1988; Revision 1, dated November 21, 1991;

Revision 2, dated September 16, 1993; or Revision 3, dated February

15, 1996. Repeat the detailed visual inspection thereafter at

intervals not to exceed 3,000 flight cycles, until accomplishment of

the requirements specified in either paragraph (b) or (c) of this

AD.

Note 2: For the purposes of this AD, a detailed 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 3: Accomplishment of the high frequency eddy current (HFEC)

inspection required by AD 90-02-16, is considered acceptable for

compliance with the initial detailed visual inspection required by

paragraph (a) of this AD.

Repair of Cracks

(b) If any crack is detected during any inspection required by

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

actions specified in either paragraph (b)(1) or (b)(2) of this AD,

as applicable. Accomplishment of the repair action constitutes

terminating action for the repetitive inspection requirements of

paragraph (a) of this AD for that repaired area.

(1) For airplanes equipped with integral fuel tanks in the

center section of the wings: Repair in accordance with Figure 2 of

Boeing Service Bulletin 727-57-0177, Revision 3, dated February 15,

1996.

(2) For airplanes not equipped with integral fuel tanks in the

center section of the wings: Repair in accordance with Figure 2 of

Boeing Service Bulletin 727-57-0177, dated December 22, 1988,

Revision 1, dated November 21, 1991; Revision 2, dated September 16,

1993; or Revision 3, dated February 15, 1996.

Note 4: Where there are differences between the referenced

service bulletins and this AD, the AD prevails.

Modification

(c) Except as provided by paragraph (d) of this AD, prior to the

accumulation of 60,000 total flight cycles, or within 48 months

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

accomplish the actions specified in either paragraph (c)(1) or

(c)(2) of this AD, as applicable. Accomplishment of this action

constitutes terminating action for the repetitive inspection

requirements of paragraph (a) of this AD.

(1) For airplanes equipped with integral fuel tanks in the

center section of the wings: Modify the front spar web, between the

upper and lower seals, of the center section of the wings, in

accordance with Part I of the Accomplishment Instructions of Boeing

Service Bulletin 727-57-0177, Revision 3, dated February 15, 1996.

(2) For airplanes not equipped with integral fuel tanks in the

center section of the wings: Modify the front spar web, between the

upper and lower seals, of the center section of the wings, in

accordance with Boeing Service Bulletin 727-57-0177, dated December

22, 1988, Revision 1, dated November 21, 1991; Revision 2, dated

September 16, 1993; or Revision 3, dated February 15, 1996.

Repetitive Visual Inspections and Repair/Modification of the Front Spar

Web

(d) For areas on which the front spar web between the upper and

lower seals of the center section of the wings has been repaired or

modified in accordance with Figure 2 or 3 of Boeing Service Bulletin

727-57-0177, dated December 22, 1988; Revision 1, dated November 21,

1991; or Revision 2, dated September 16, 1993: Accomplish the

actions required by either paragraph (d)(1) or (d)(2) of this AD, as

applicable.

(1) For airplanes not equipped with integral fuel tanks in the

center section of the wings: No further action is required by this

AD for those areas repaired or modified.

(2) For airplanes equipped with integral fuel tanks in the

center section of the wings: Accomplish the actions required by both

paragraphs (d)(2)(i) and (d)(2)(ii) of this AD.

(i) Within 500 flight cycles after the effective date of this

AD, perform a detailed visual inspection of the front spar web to

detect fuel leakage and penetrations in the secondary fuel barrier,

and to verify the installation of the secondary fuel barrier; in

accordance with Boeing Service Bulletin 727-57-0177, Revision 3,

dated February 15, 1996. Repeat the visual inspection thereafter at

intervals not to exceed 1,500 flight cycles, until accomplishment of

the actions required by paragraph (d)(2)(ii) of this AD.

(ii) Prior to the accumulation of 14,000 flight cycles, or

within 96 months after the effective date of this AD, whichever

occurs later, repair/modify the front spar web in accordance with

Part II of the Accomplishment Instructions of Boeing Service

Bulletin 727-57-0177, Revision 3, dated February 15, 1996.

Accomplishment of this action constitutes terminating action for the

repetitive inspection requirements of paragraph (d)(2)(i) of this AD

for that repaired/modified area.

Follow-On Corrective Action

(e) During any inspection required by paragraph (d)(2)(i) of

this AD, if any fuel leakage or penetration in the secondary fuel

barrier is detected, or if any secondary fuel barrier is verified as

not being installed, prior to further flight, repair in accordance

with Part II of the Accomplishment Instructions of Boeing Service

Bulletin 727-57-0177, Revision 3, dated February 15, 1996.

Accomplishment of this action constitutes terminating action for the

repetitive inspection requirements of paragraph (d)(2)(i) of this AD

for that repaired area.

Terminating Action for AD 94-05-04

(f) Accomplishment of the actions required by paragraph (b),

(c), (d)(2)(ii), or (e) of this AD constitutes terminating action

for the requirements specified in paragraph (a) of AD 94-05-04,

amendment 39-8842 (59 FR 13442

[[Page 43321]]

dated March 22, 1994), with respect to the modification specified in

Boeing Service Bulletin 727-57-0177, dated December 22, 1988. This

service bulletin is one of many service bulletins referenced in

Boeing Document D6-54860, Revision G, Appendix A.3, dated March 5,

1993. All other service bulletins referenced in that document still

apply.

Alternative Method of Compliance

(g)(1) 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 5: Information concerning the existence of approved

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

obtained from the Seattle ACO.

(g)(2) For airplanes not equipped with integral fuel tanks in

the center section of the wings: Alternative methods of compliance,

approved previously in accordance with AD 90-02-16, amendment 39-

6452, are approved as alternative methods of compliance with this

AD. For airplanes equipped with integral fuel tank in the center

section of the wings: Alternative methods of compliance, approved

previously in accordance with AD 90-02-15, are NOT approved as

alternative methods of compliance with this AD.

Special Flight Permits

(h) 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 4, 1999.

D.L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-20504 Filed 8-9-99; 8:45 am]

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