Airworthiness Directives; Boeing Model 707/720 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-80-AD; Amendment 39-8913; AD 94-10-06]

Airworthiness Directives; Boeing Model 707/720 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to certain Boeing Model 707/720 series airplanes, that

requires certain structural inspections of older airplanes. This

amendment is prompted by reports of incidents involving fatigue

cracking and corrosion in transport category airplanes that are

approaching or have exceeded their economic design service goal. The

actions specified by this AD are intended to prevent degradation of the

structural capabilities of the affected airplanes. This amendment

relates to the recommendations of the Airworthiness Assurance Task

Force assigned to review Model 707/720 series airplanes, which indicate

that, to assure long term continued operational safety, various

structural inspections should be accomplished.

DATES: Effective June 20, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of June 20, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,

Washington 98124-2207. This information may be examined at the Federal

Aviation Administration (FAA), Transport Airplane Directorate, Rules

Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of

the Federal Register, 800 North Capitol Street, NW., suite 700,

Washington, DC.

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: A proposal to amend part 39 of the Federal

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to certain Boeing Model 707/720 series airplanes was

published in the Federal Register on October 18, 1993 (58 FR 53678).

That action proposed to require inspections of certain structural

components on older airplanes for cracks, corrosion, and other

discrepancies, and repair or correction of discrepancies, if necessary.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the proposed rule.

One commenter requests that the structural inspections and

modifications referenced in section A.3 and section A.4 of appendix A

of Boeing Document Number D6-54996, ``Aging Airplane Service Bulletin

Structural Modification and Inspection Program--Model 707/720,''

Revision D, dated January 23, 1992, be combined and addressed as a

single AD action, rather than in two separate actions, as proposed by

the FAA in this notice. This commenter points out that the FAA

previously issued AD 94-06-08, Amendment 39-8856 (59 FR 13446, March

22, 1994), which requires the accomplishment of a certain structural

modification of the wing front spar lower chord in accordance with

section A.3 of appendix A of the Boeing Document. This commenter

contends that by issuing a single AD to cover both sections of the

Boeing Document, the FAA will contribute to reducing the cost and

complexity of publishing and tracking multiple AD's, while maintaining

the same level of safety.

The FAA does not concur with this commenter's request, specifically

because of the nature of the requirements of the rules. The

requirements contained in AD 94-06-08 address a single structural

modification applicable to Model 707 series airplanes listed in

Appendix A.3 of the Boeing Document. The compliance time for

accomplishing that modification is based on either the number of flight

cycles on the airplane or a specific calendar time. The requirements of

this AD, however, address structural inspections for both Model 707 and

Model 720 series airplanes listed in section 4 and appendix A.4 of the

Boeing Document. The compliance times for implementation of these

various inspections vary, as do the repetitive inspection intervals.

The FAA considers that combining the requirements for these dissimilar

actions into one complex AD would create unnecessary confusion for

affected operators. Therefore, the FAA finds it appropriate to issue

one AD addressing the modification and another AD addressing

``inspections only.'' This method of issuance will ease tracking of and

facilitate compliance with the requirements of these two separate AD's.

Since the issuance of the proposal, the FAA has reviewed and

approved Revision E of Boeing Document Number D6-54996, ``Aging

Airplane Service Bulletin Structural Modification and Inspection

Program--Model 707/720,'' dated March 8, 1994. The inspections

described in this revision are identical to those described in Revision

D, which was referenced in the proposal as the appropriate source of

service information. The only change effected by Revision E is that it

excludes the inspections of the upper skin on the wing center section

described in Boeing Service Bulletin 2590. The actions specified in

Boeing Service Bulletin 2590 currently are the subject of AD 68-18-03,

Amendment 39-2056. In light of this, the final rule has been revised to

reference Revision E of the Boeing Document as the appropriate source

of service information in order to eliminate these redundant inspection

requirements. The applicability of the final rule has also been revised

to reference those airplanes listed in Revision E of the Boeing

Document in order to exclude those airplanes that are subject to the

requirements of Boeing Service Bulletin 2590. Additionally, the

economic impact information, below, has been revised to reflect the

deletion of these inspections from the required number of work hours

for accomplishment of the actions required by this final rule.

Upon further review of the inspection actions required by this AD,

the FAA has revised the final rule to extend the proposed 15-month

compliance time to 18 months (for airplanes that have surpassed the

specified compliance threshold in terms of accumulated flight cycles or

time-in-service). The FAA has determined that increasing the compliance

time by an additional three months will not adversely affect safety,

and will allow the inspections to be performed during regularly

scheduled maintenance at a main base where special equipment and

trained maintenance personnel will be available if necessary. Moreover,

this is the compliance time currently recommended by the manufacturer

in the latest revision to the Boeing Document, which is referenced in

the final rule.

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the changes previously

described. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

There are approximately 416 Model 707/720 series airplanes of the

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

airplanes of U.S. registry will be affected by this AD, that it will

take approximately 691 work hours per airplane to accomplish the

required actions, and that the average labor rate is $55 per work hour.

Based on these figures, the total cost impact of the AD on U.S.

operators is estimated to be $3,116,410, or $38,005 per airplane.

The total cost impact figure discussed above is based on

assumptions that no operator has yet accomplished any of the

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

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

The FAA recognizes that the obligation to maintain aircraft in an

airworthy condition is vital, but sometimes expensive. Because AD's

require specific actions to address specific unsafe conditions, they

appear to impose costs that would not otherwise be borne by operators.

However, because of the general obligation of operators to maintain

aircraft in an airworthy condition, this appearance is deceptive.

Attributing those costs solely to the issuance of this AD is

unrealistic because, in the interest of maintaining safe aircraft, most

prudent operators would accomplish the required actions even if they

were not required to do so by the AD.

A full cost-benefit analysis has not been accomplished for this AD.

As a matter of law, in order to be airworthy, an aircraft must conform

to its type design and be in a condition for safe operation. The type

design is approved only after the FAA makes a determination that it

complies with all applicable airworthiness requirements. In adopting

and maintaining those requirements, the FAA has already made the

determination that they establish a level of safety that is cost-

beneficial. When the FAA, as in this AD, makes a finding of an unsafe

condition, this means that this cost-beneficial level of safety is no

longer being achieved and that the required actions are necessary to

restore that level of safety. Because this level of safety has already

been determined to be cost-beneficial, a full cost-benefit analysis for

this AD would be redundant and unnecessary.

The regulations adopted herein will 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from the Rules Docket at the location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 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:

94-10-06 Boeing: Amendment 39-8913. Docket 93-NM-80-AD.

Applicability: Model 707/720 series airplanes, as listed in

section 4 and appendix A.4 of Boeing Document D6-54996, ``Aging

Airplane Service Bulletin Structural Modification and Inspection

Program-- Model 707/720,'' Revision E, dated March 8, 1994;

certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent degradation of the structural capability of the

airplane, accomplish the following:

(a) Accomplish the inspections specified in Section 4 and

Appendix A.4 of Boeing Document Number D6-54996, ``Aging Airplane

Service Bulletin Structural Modification and Inspection Program--

Model 707/720,'' Revision E, dated March 8, 1994, in accordance with

the schedule specified in paragraph (b) of this AD. Repeat these

inspections thereafter at intervals not to exceed those specified in

the Boeing Document for each inspection.

(b) The maximum initial inspection time for the inspections

required by paragraph (a) of this AD shall be the later of the times

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

(1) The threshold for inspection time for the inspection

specified in the Boeing Document, measured as an accumulated total

of flight cycles or time-in-service, as appropriate; or

(2) The ``phase-in'' period for the inspection specified in the

Boeing Document, measured from a date 18 months after the effective

date of this AD.

Note 1: For the purposes of this AD, the ``phase-in period'' is

defined as the allowable period to accomplish the initial inspection

when the ``threshold'' specified in paragraph (b)(1) of this AD is

imminent or has elapsed.

(c) If any discrepant condition identified in the service

bulletins (that are specified in the Boeing Document) is found as a

result of the inspections required by this AD, prior to further

flight, accomplish the corresponding corrective action specified in

the service bulletins.

(d) The terminating action for each inspection required by

paragraph (a) of this AD consists of the accomplishment of the

modification specified in the corresponding service bulletin.

(e) 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.

(f) 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.

(g) The inspections and corrective actions shall be done in

accordance with Boeing Document Number D6-54996, ``Aging Airplane

Service Bulletin Structural Modification and Inspection Program--

Model 707/720,'' Revision E, dated March 8, 1994, which includes the

following list of effective pages:

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Page No. Revision level shown on page

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List of active pages:

Pages c.1 and c.2................... E

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(Note: The issue date of Revision E is indicated only on the

title page; no other page of the document is dated.) This

incorporation by reference was approved by the Director of the

Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part

51. Copies may be obtained from Boeing Commercial Airplane Group,

P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be

inspected at the FAA, Transport Airplane Directorate, 1601 Lind

Avenue, SW., Renton, Washington; or at the Office of the Federal

Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(h) This amendment becomes effective on June 20, 1994.

Issued in Renton, Washington, on May 6, 1994.

S. R. Miller,

Acting Manager,

Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 94-11523 Filed 5-18-94; 8:45 am]

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