Airworthiness Directives; Boeing Model 737 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 96-NM-149-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 737 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 all Boeing Model 737 series

airplanes. This proposal would require revising the FAA-approved

maintenance program to prohibit the use of pressure washing within the

wheel well or on the landing gear and to prohibit the use of pumps and/

or nozzles for washing wheel wells or the landing gear. This proposal

is prompted by a review of the design of the flight control systems on

Model 737 series airplanes. The actions specified by the proposed AD

are intended to prevent corrosion of certain equipment due to the use

of inappropriate pressure washing techniques. Corrosion of bearings,

cables, electrical connectors, or other equipment in the main wheel

well, if not detected and corrected in a timely manner, could result in

reduced controllability of the airplane.

DATES: Comments must be received by October 24, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 96-NM-149-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: David Herron, Aerospace Engineer,

Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane

Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,

SW., Renton, Washington 98055-4056; telephone (206) 227-2672; 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 96-NM-149-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. 96-NM-149-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

In October 1994, the FAA organized a team to conduct a Critical

Design Review (CDR) of the flight control systems installed on Boeing

Model 737 series airplanes in an effort to confirm the continued

operational safety of these airplanes. The formation of the CDR team

was prompted by questions that arose following an accident involving a

Model 737-200 series airplane that occurred near Colorado Springs,

Colorado, and one involving a Model 737-300 series airplane that

occurred near Pittsburgh, Pennsylvania. The CDR team's analysis of the

flight control systems was performed independent of the investigations

of these accidents, which are conducted by the National Transportation

Safety Board (NTSB). The cause of the accidents has not yet been

determined.

The CDR team was composed of representatives from the FAA, the

NTSB, other U.S. government organizations, and foreign airworthiness

authorities. The team reviewed the service history and the design of

the

[[Page 44240]]

flight control systems of Model 737 series airplanes. The team

completed its review in May 1995. The recommendations of the team

include various changes to the design of the flight control systems of

these airplanes, as well as correction of certain design deficiencies.

This proposed AD is one of nine rulemaking actions being issued by the

FAA to address the recommendations of the CDR team.

Reports Received by FAA

The FAA has received reports indicating that inappropriate pressure

washing techniques, such as the use of high pressure washing, have been

used to clean equipment within the wheel wells of Model 737 series

airplanes. High pressure washing of the bearings, cables, electrical

connectors, and other equipment in the main wheel well can result in

fluids (or additives in the fluids) being forced into these areas.

Retention of fluid in these areas can result in the development of

corrosion. Corrosion of bearings, cables, electrical connectors, or

other equipment in the main wheel well, if not detected and corrected

in a timely manner, could result in reduced controllability of the

airplane.

FAA's Findings

The FAA finds that Model 737 series airplanes were not designed to

withstand high pressure washing of the wheel wells and landing gears.

The FAA concludes that these airplanes were designed to operate with

contaminate buildup in the wheel wells and landing gears. In light of

this, the FAA has determined that the FAA-approved maintenance program

must be revised to prohibit the use of pressure washing within the

wheel well or on the landing gear. Pressure washing is defined as the

use of any fluid under pressure greater than 80 pounds per square inch,

gauge (psig). The FAA also finds that the use of pumps and/or nozzles

must be prohibited, since such use results in pressure greater than 80

psig.

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 require revising the FAA-approved maintenance program

to prohibit the use of pressure washing within the wheel well or on the

landing gear and to prohibit the use of pumps and/or nozzles for

washing wheel wells or the landing gear.

Cost Impact

There are approximately 2,463 Model 737 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 1,040

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

it would take approximately 5 work hours per airplane to accomplish the

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

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

operators is estimated to be $312,000, or $300 per airplane.

The 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.

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.''

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 adding the following new

airworthiness directive:

Boeing: Docket 96-NM-149-AD.

Applicability: All Model 737 series airplanes, 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 corrosion in the bearings, cables, electrical

connectors, or other equipment in the main wheel well, which could

result in reduced controllability of the airplane, accomplish the

following:

(a) Within 90 days after the effective date of this AD,

incorporate a revision into the FAA-approved maintenance program

that prohibits the use of pressure washing within the wheel well or

on the landing gear, and that prohibits the use of pumps and/or

nozzles for washing wheel wells or the landing gear. Pressure

washing is defined as the use of any fluid under pressure greater

than 80 pounds per square inch, gauge (psig).

(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.

Issued in Renton, Washington, on August 21, 1996.

Ronald T. Wojnar,

Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 96-21881 Filed 8-23-96; 9:02 am]

BILLING CODE 4910-13-U