Airworthiness Directives; Boeing Model 707 and 720 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-14-AD]

Airworthiness Directives; Boeing Model 707 and 720 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 707

and 720 series airplanes, that currently requires repetitive visual and

dye penetrant inspections to detect cracks on the upper forward skin

panels of the wing center section, and repair, if necessary. That AD

also provided an optional terminating modification for the repetitive

inspections. This action would require visual and eddy current

inspections to detect cracks on the upper forward skin panels of the

wing center section, and repair, if necessary. This proposal is

prompted by reports that the currently required inspections are not

effective in detecting fatigue cracks in a timely manner. The actions

specified by the proposed AD are intended to prevent fatigue cracking

and subsequent failure of the upper forward skin panels of the wing

center section.

DATES: Comments must be received by October 5, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-14-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: Phil Forde, Aerospace Engineer,

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

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

Washington 98055-4056; telephone (206) 227-2771; 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-14-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-14-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA issued AD 68-18-03, amendment 39-2056, applicable to

certain Boeing Model 707 and 720 series airplanes, to require

repetitive inspections to detect cracks on the upper forward skin

panels of the wing center section, and repair, if necessary. That AD

also provided an optional terminating modification for the repetitive

inspections. That action was prompted by several reports of fatigue

cracking and one report of skin blowout (failure of the wing skin

panel) on Model 720 series airplanes. Model 707 series airplanes were

included in the applicability of AD 68-18-03 because those airplanes

are similar in design to Model 720 series airplanes. The requirements

of that AD are intended to prevent fatigue cracking and subsequent

failure of the upper forward skin panels of the wing center section.

Since the issuance of AD 68-18-03, the FAA has received several

reports that the visual and dye penetrant inspection techniques

required by that AD have not been effective in detecting cracks in a

timely manner. The FAA, in conjunction with the airplane manufacturer

and the Boeing Model 707 Aging Fleet Structures Working Group (SWG),

conducted a structural review of those airplanes and determined that

inspections using visual and eddy current methods are necessary in

order to effectively detect cracks in a timely manner for airplanes on

which the optional terminating modification specified in AD 68-18-03

has not been accomplished.

Fatigue cracking in the upper forward skin panels of the wing

center section, if not detected and corrected in a timely manner, could

result in failure of the wing skin panels.

The FAA has reviewed and approved Boeing Service Bulletin 2590,

Revision 11, dated December 12, 1991, that describes procedures for

repetitive visual and eddy current inspections to detect cracks in

certain areas of the upper forward skin panels of the wing center

section, and repair, if necessary. This service bulletin is part of

Boeing Master Inspection Service Bulletins 3484 (for Model 707-100 and

-200 airplanes), 3485 (for Model 720 and 720B airplanes), and 3486 (for

Model 707-300, -300B, -300C, and -400 airplanes), all dated December

12, 1991. Boeing Service Bulletin 2590 references these master

inspection service bulletins as additional sources of service

information concerning accomplishment of the repetitive inspections.

The master inspection service bulletins describe an expanded inspection

area that includes a 4-inch wide strip centered on each chordwise bulb

angle stiffener installed in accordance with AD 68-18-03.

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 68-18-03 to require repetitive visual

and eddy current inspections to detect cracks in certain areas of the

upper forward skin panels of the wing center section, and repair, if

necessary. This AD also would provide an optional terminating action

for the repetitive inspections. The actions would be required to be

accomplished in accordance with Boeing Service Bulletin 2590, described

previously.

There are approximately 416 Model 707 and 720 series airplanes of

the affected design in the worldwide fleet. The FAA estimates that 82

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

it would take approximately 32 work hours per airplane to accomplish

the proposed inspections, 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 $144,320, or $1,760

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 that would be provided by this AD action, it would take

approximately 1,250 work hours to accomplish it, at an average labor

rate of $55 per work hour. The cost of required parts would be

approximately $45,000 per airplane. Based on these figures, the total

cost impact of the optional terminating action would be $113,750 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 39-2056, and by

adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 94-NM-14-AD. Supersedes AD 68-18-03, Amendment 39-

2056.

Applicability: All Model 707 and 720 series airplanes,

certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent fatigue cracking and subsequent failure of the upper

forward skin panels of the wing center section, accomplish the

following:

(a) For Model 707-100, -200, -300, -300B, -300C, and -400

airplanes on which no bulb angle stiffeners have been installed in

accordance with Boeing Service Bulletin 2590: Perform a visual

inspection and an eddy current inspection to detect cracks in the

areas of the upper forward skin of the wing center section specified

in paragraphs b. and f.(1) of Part I of the Accomplishment

Instructions of Boeing Service Bulletin 2590, Revision 8, dated June

2, 1972; Revision 9, dated March 14, 1975; Revision 10, dated

January 31, 1991; or Revision 11, dated December 12, 1991. Perform

the inspections at the time specified in paragraph (a)(1) or (a)(2)

of this AD, as applicable, in accordance with the procedures

specified in the service bulletin. Repeat these inspections

thereafter at intervals not to exceed 1,000 landings or 18 months,

whichever occurs first.

(1) For Model 707-300, -300B, -300C, and -400 airplanes: Inspect

at the later of the times specified in paragraphs (a)(1)(i) and

(a)(1)(ii) of this AD.

(i) Prior to the accumulation of 6,000 total landings; or

(ii) Within 500 landings or 18 months after the effective date

of this AD, whichever occurs first.

(2) For Model 707-100 and -200 airplanes: Inspect at the later

of the times specified in paragraphs (a)(2)(i) and (a)(2)(ii) of

this AD.

(i) Prior to the accumulation of 7,000 total landings; or

(ii) Within 500 landings or 18 months after the effective date

of this AD, whichever occurs first.

(b) For Model 720 and 720B airplanes on which no bulb angle

stiffeners have been installed in accordance with Boeing Service

Bulletin 2590: Perform a visual inspection and an eddy current

inspection to detect cracks in the area of the upper forward skin of

the wing center section specified in paragraph b. of Part I of the

Accomplishment Instructions of Boeing Service Bulletin 2590,

Revision 8, dated June 2, 1972; Revision 9, dated March 14, 1975;

Revision 10, dated January 31, 1991; or Revision 11, dated December

12, 1991. Perform the inspections at the later of the times

specified in paragraphs (b)(1) and (b)(2) of this AD, in accordance

with the procedures specified in the service bulletin. Repeat these

inspections thereafter at intervals not to exceed 1,000 landings or

18 months, whichever occurs first.

(1) Prior to the accumulation of 4,000 total landings; or

(2) Within 500 landings or 18 months after the effective date of

this AD, whichever occurs first.

(c) For Model 720 and 720B, and 707-100, -200, -300, -300B, -

300C, and -400 airplanes on which bulb angle stiffeners have been

installed, but on which the wing skin has not been replaced, in

accordance with Boeing Service Bulletin 2590: Accomplish the

inspections required by paragraph (c)(1), (c)(2), or (c)(3) of this

AD, as applicable, in accordance with Boeing Service Bulletin 2590,

Revision 11, dated December 12, 1991. Repeat these inspections

thereafter at intervals not to exceed 1,000 landings or 18 months,

whichever occurs first.

Note 1: Revision 11 of Boeing Service Bulletin 2590 is part of

Boeing Master Inspection Service Bulletins 3484 (for Model 707-100

and -200 airplanes), 3485 (for Model 720 and 720B airplanes), and

3486 (for Model 707-300, -300B, -300C, and -400 airplanes), all

dated December 12, 1991. Boeing Service Bulletin 2590 references

these master inspection service bulletins as additional sources of

service information concerning accomplishment of the inspections

required by paragraph (c) of this AD.

(1) For Model 720 and 720B airplanes: Perform a visual and an

eddy current inspection to detect cracks in the areas of the upper

forward skin of the wing center section specified in Boeing Master

Inspection Service Bulletin 3485, dated December 12, 1991, at the

later of the times specified in paragraphs (c)(1)(i) and (c)(1)(ii)

of this AD.

(i) Prior to the accumulation of 2,200 landings after

installation of the bulb angle stiffeners; or

(ii) Within 500 landings or 18 months after the effective date

of this AD, whichever occurs first.

(2) For Model 707-300, -300B, -300C, and -400 airplanes: Perform

a visual and an eddy current inspection to detect cracks in the

areas of the upper forward skin of the wing center section specified

in Boeing Master Inspection Service Bulletin 3486, dated December

12, 1991, at the later of the times specified in paragraphs

(c)(2)(i) and (c)(2)(ii) of this AD.

(i) Prior to the accumulation of 2,200 landings after

installation of the bulb angle stiffeners; or

(ii) Within 500 landings or 18 months after the effective date

of this AD, whichever occurs first.

(3) For Model 707-100 and -200 airplanes: Perform a visual and

an eddy current inspection to detect cracks in the areas of the

upper forward skin of the wing center section specified in Boeing

Master Inspection Service Bulletin 3484, dated December 12, 1991, at

the later of the times specified in paragraphs (c)(3)(i) and

(c)(3)(ii) of this AD.

(i) Prior to the accumulation of 2,200 landings after

installation of the bulb angle stiffeners; or

(ii) Within 500 landings or 18 months after the effective date

of this AD, whichever occurs first.

(d) If any crack is found during any of the inspections required

by paragraphs (a), (b), and (c) of this AD, prior to further flight,

repair in accordance with Part II of the Accomplishment Instructions

of Boeing Service Bulletin 2590, Revision 7, dated September 22,

1969; Revision 8, dated June 2, 1972; Revision 9, dated March 14,

1975; Revision 10, dated January 31, 1991; or Revision 11, dated

December 12, 1991.

(e) Accomplishment of the ``Reinforcing Stiffener Installation

and Skin Panel Replacement'' in accordance with Part III of the

Accomplishment Instructions of Boeing Service Bulletin 2590,

Revision 6, dated July 8, 1968; Revision 7, dated September 22,

1969; Revision 8, dated June 2, 1972; Revision 9, dated March 14,

1975; Revision 10, dated January 31, 1991; or Revision 11, dated

December 12, 1991; constitutes terminating action for the repetitive

inspections required by paragraphs (a), (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 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 2: 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

Sec. Sec. 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 July 12, 1994.

S.R. Miller,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-17326 Filed 7-15-94; 8:45 am]

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