Airworthiness Directives; Boeing Model 757-200 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-54-AD; Amendment 39-10747; AD 98-19-05]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 757-200 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

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

applicable to certain Boeing Model 757-200 series airplanes, that

requires the application of a sealant, secondary fuel barrier, and

corrosion-inhibiting compound to certain portions of the wing center

section. This amendment is prompted by reports indicating that, during

manufacture, the secondary fuel barrier was not applied to certain

portions of the wing center section. The actions specified by this AD

are intended to prevent leakage of fuel through the fasteners, sealant,

or structural cracks in the center section structure, which could

result in fuel or fuel vapors entering the cargo or passenger

compartment of the airplane.

DATES: Effective October 15, 1998.

The incorporation by reference of certain publications listed in

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

of October 15, 1998.

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 Registe, 800 North Capitol Street, NW., suite 700,

Washington, DC.

FOR FURTHER INFORMATION CONTACT: Kathrine Rask, Aerospace Engineer,

Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,

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

Washington 98055-4056; telephone (425) 227-1547; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to certain Boeing Model 757-200

series airplanes was published in the Federal Register on September 25,

1997 (62 FR 50263). That action proposed to require the application of

a sealant, secondary fuel barrier, and corrosion-inhibiting compound to

certain portions of the wing center section.

Comments

Interested persons have been afforded an opportunity to participate

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

the comments received.

Support for the Proposal

One commenter supports the proposed rule.

Request for Extension of the Compliance Time

Several commenters request that the compliance time for the actions

required by this proposed AD be extended, and suggest that the

compliance thresholds

[[Page 48424]]

be revised to coincide with the next scheduled heavy maintenance check.

Compliance times of 36 months, 48 months, and 72 months are suggested

as appropriate for the extension. The commenters state that the

extensive access required to fully clean the corrosion inhibiting

compound applied at the factory, the cure times for the sealants, and

the application of the corrosion inhibiting compounds, are all factors

making it prohibitive to incorporate the modification during ``C''

checks. One commenter estimates that it could save $36,000 by

retrofitting its 17 airplanes during a heavy maintenance check instead

of during a ``C'' check. Another operator states that to accomplish the

modification on its affected fleet of airplanes within 18 months would

require special scheduling and would create an economic burden. Another

commenter states that it does not agree with the logic used to

determine the urgency of this issue because there have not been any

reports or evidence of fuel vapors reaching the pressurized area.

The FAA concurs that the compliance times can be extended somewhat.

The intent of the AD is that the inspections be conducted during a

regularly scheduled maintenance visit for the majority of the affected

fleet, when the airplanes would be located at a base where special

equipment and trained personnel would be readily available, if

necessary. Based on the information supplied by the commenters, the FAA

now recognizes that a compliance time of 48 months corresponds more

closely to the interval representative of most of the affected

operators' normal maintenance schedules. Paragraph (a) of the final

rule has been revised to require accomplishment of the required actions

``at the next scheduled heavy maintenance check (i.e., a ``4C'' check)

or within 48 months after the effective date of the AD, whichever

occurs first.'' The FAA does not consider that this extension will

adversely affect safety. The affected area is small, approximately 200

square inches, and there have been no reported leaks in this area of

the front spar of the wing center section. In addition, the barrier

does not function as the primary barrier but is designed to provide a

fume-proof and fuel-proof barrier in the event of a failure of the

fastener sealant or structural cracks in the center section.

Request for Use of Equivalent Methods and Finishes

One commenter requests that the proposed AD be revised to allow the

use of an ``industry accepted standard or practice'' material, in lieu

of ``original equipment manufacturer approved parts and procedures.''

The commenter states that Boeing Service Bulletin 757-57-0053, dated

February 6, 1997, lists secondary fuel barrier BMS 5-81, Type II, which

is not stocked by the airplane manufacturer or this operator.

The FAA does not concur with the commenter's request. The material

in question, secondary fuel barrier, is used on all current generation

Boeing airplanes and, from time to time, may require replacement

following structural work on the fuel tank walls. Although such

material may not currently be stocked by this operator, it should be

readily available. Further, BMS 5-81, Type II, has specific property

requirements needed to ensure a fume-proof and fuel-proof barrier over

the life of the airplane. Allowing use of other substances without a

detailed review by the FAA could compromise the performance of the

barrier. However, for any material or process an operator may wish to

substitute, the operator may request approval of an alternative method

of compliance in accordance with the provisions of paragraph (b) of

this AD.

Request for Revision of Cost Impact Information

Two commenters state that the proposed AD underestimates the cost

of the modification, in that the economic analysis did not include the

18 to 36 work hours required to gain access to the front spar of the

wing center section and to return the airplane to a serviceable

condition. Another commenter states that the airplane downtime required

to accomplish the modification during a ``C'' check was not included in

the cost impact information.

The FAA acknowledges that the cost impact information, below,

describes only the ``direct'' costs of the specific actions required by

this AD. The estimate of 2 work hours necessary to accomplish the

required actions was provided to the FAA by the manufacturer, and

represents the time necessary to perform only the actions actually

required by this AD. The FAA recognizes that, in accomplishing the

requirements of any AD, operators may incur ``incidental'' costs in

addition to the ``direct'' costs. The cost analysis in AD rulemaking

actions, however, typically does not include incidental costs, such as

the time required to gain access and close up; planning time; or time

necessitated by other administrative actions. Because incidental costs

may vary significantly from operator to operator, they are almost

impossible to calculate.

Furthermore, because the FAA generally attempts to impose

compliance times that coincide with operators' scheduled maintenance,

the FAA considers it inappropriate to attribute the costs associated

with aircraft ``downtime'' to the cost of the AD because, normally,

compliance with the AD will not necessitate any additional downtime

beyond that of a regularly scheduled maintenance hold. Even if, in some

cases, additional downtime is necessary for some airplanes, the FAA

does not possess sufficient information to evaluate the number of

airplanes that may be so affected or the amount of additional downtime

that may be required. Therefore, attempting to estimate such costs

would be futile. No change to the final rule is necessary.

Explanation of Changes Made to Proposal

Since the issuance of the proposed AD, the manufacturer has issued

Boeing Service Bulletin 757-57-0053, Revision 1, dated January 15,

1998. This revision is essentially the same as Boeing Service Bulletin

757-57-0053, dated February 6, 1997 (which is cited in the proposal as

the appropriate source of service information for accomplishment of the

requirements of the AD), with minor editorial changes incorporated. The

FAA has reviewed and approved this revision as an additional source of

service information for accomplishment of the actions required by this

AD, and has revised the final rule accordingly.

Conclusion

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 described

previously. The FAA has determined that these changes will neither

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

the AD.

Cost Impact

There are approximately 724 Boeing Model 757-200 series airplanes

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

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

will take approximately 2 work hours per airplane to accomplish the

required actions, and that the average labor rate is $60 per work hour.

Required parts will cost approximately $100 per airplane. Based on

these figures, the cost impact of the AD on U.S. operators is estimated

to be $101,860, or $220 per airplane.

[[Page 48425]]

The 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.

Regulatory Impact

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 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:

98-19-05 Boeing: Amendment 39-10747. Docket 97-NM-54-AD.

Applicability: Model 757-200 series airplanes, line numbers 1

through 724 inclusive, 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 (b) 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 leakage of fuel through the fasteners, sealant, or

structural cracks in the center section structure, which could

result in fuel or fuel vapors entering into the cargo or passenger

compartment of the airplane, accomplish the following:

(a) At the next scheduled heavy maintenance check (i.e., ``4C''

check) or within 48 months after the effective date of this AD,

whichever occurs first, apply sealant, secondary fuel barrier, and

corrosion-inhibiting compound to areas on the front spar of the wing

center section, in accordance with Figure 3 of Boeing Service

Bulletin 757-57-0053, dated February 6, 1997, or Boeing Service

Bulletin 757-57-0053, Revision 1, dated January 15, 1998.

(b) 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.

(c) 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.

(d) The actions shall be done in accordance with Boeing Service

Bulletin 757-57-0053, dated February 6, 1997, or Boeing Service

Bulletin 757-57-0053, Revision 1, dated January 15, 1998. 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.

(e) This amendment becomes effective on October 15, 1998.

Issued in Renton, Washington on September 1, 1998.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 98-24059 Filed 9-9-98; 8:45 am]

BILLING CODE 4910-13-U