Airworthiness Directives; Boeing Model 737-100 and -200 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 96-NM-152-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 737-100 and -200 Series

Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: This document proposes the adoption of a new airworthiness

directive (AD) that is applicable to all Boeing Model 737-100 and -200

series airplanes. This proposal would require replacement of certain

outboard and inboard wheel halves with improved wheel halves. This

proposal also would require cleaning and inspecting certain outboard

and inboard wheel halves for corrosion, missing paint in large areas,

and cracks; and repair or replacement of the wheel halves with

serviceable wheel halves, if necessary. 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 failure of the wheel flanges, which could result in failure of

the hydraulics systems, jammed flight controls, loss of electrical

power, or other combinations of failures; and consequent 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-152-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 Allied Signal Aerospace Company, Bendix Wheels and Brakes

Division, South Bend, Indiana 46624; and Bendix, Aircraft Brake and

Strut Division, 3520 West Mestmoor Street, South Bend, Indiana 46624.

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, Seattle Aircraft

Certification Office, 1601 Lind Avenue, SW., Renton, Washington;

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.

[[Page 44246]]

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-152-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-152-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 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 received a report indicating that failure of the wheel

flanges can result in metallic debris impacting the hydraulics systems

and other critical elements associated with control of the airplane

that are within the proximity of the wheel. Such impact can result in

failure of the hydraulics systems, jammed flight controls, loss of

electrical power, or other combinations of failures. These conditions,

if not corrected, could result in reduced controllability of the

airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Bendix Service Information Letter

(SIL) 392, Revision 1, dated November 15, 1979, which describes

procedures for replacement of any outboard wheel half having serial

number (S/N) H-999 and lower with an outboard wheel half having part

number (P/N) 2607047; and replacement of any inboard wheel half having

S/N H-1799 and lower with a wheel half having P/N 2607046. These

replacements must be accomplished on airplanes equipped with a Bendix

main wheel assembly having part number (P/N) 2601571-1, S/N B-5999 and

lower. The improved wheel halves incorporate additional material that

will ensure greater tolerance for corrosion and handling damage of the

wheel.

The FAA also has reviewed and approved Allied Signal Service

Bulletin No. 737-32-026, dated April 26, 1988, including Attachments 1

and 2. The service bulletin describes procedures for cleaning any

outboard wheel half having P/N 2601454, S/N H0001 through H1049

inclusive, and any inboard wheel half having P/N 2601567, S/N H0001

through H1799 inclusive; inspecting the wheel halves for corrosion or

missing paint in large areas, stripping or removing any paint, and

removing any corrosion; and performing an eddy current inspection for

cracks. These actions must be accomplished on airplanes equipped with a

Bendix main wheel assembly having P/N 2601571, S/N B0001 through B5999

inclusive.

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 replacement of certain outboard and inboard

wheel halves with improved wheel halves. The proposed AD also would

require cleaning and inspecting certain outboard and inboard wheel

halves for corrosion, missing paint in large areas, and cracks; and

repair or replacement of the wheel halves with serviceable wheel

halves, if necessary. Replacement of inboard and outboard wheel halves

would be required to be accomplished in accordance with the SIL

described previously. The cleaning and inspection would be required to

be accomplished in accordance with the service bulletin described

previously.

Explanation of Proposed Compliance Time

In developing an appropriate compliance time for the proposed

actions, the FAA's intent is that it be performed 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. In

addition, the FAA considered the availability of necessary parts. The

FAA finds that 180 days corresponds closely to the interval

representative of most of the affected operators' normal maintenance

schedules. The FAA considers that this interval will provide an

acceptable level of safety.

Cost Impact

There are approximately 634 Model 737-100 and -200 series airplanes

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

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

The FAA estimates that it would take approximately 4 work hours per

airplane to accomplish the proposed replacement of wheel halves, and

that the average labor rate is $60 per work hour. Required parts would

cost approximately $20,212 per airplane. Based on these figures, the

cost impact of the proposed replacement on U.S. operators is estimated

to be $4,928,932, or $20,452 per airplane.

The FAA also estimates that it would take approximately 2 work

hours per airplane to accomplish the proposed cleaning and inspection,

and that the average labor rate is $60 per work hour. Based on these

figures, the cost impact of the proposed cleaning and inspection on

U.S. operators is estimated to be $28,920, or $120 per airplane.

The cost impact figures discussed above are 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.

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

[[Page 44247]]

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, 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

proposed 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 proposed AD,

makes a finding of an unsafe condition, this means that the original

cost-beneficial level of safety is no longer being achieved and that

the proposed 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 proposed AD would be

redundant and unnecessary.

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-152-AD.

Applicability: All Model 737-100 and -200 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

otherwise 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 (d) 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 failure of the wheel flanges, which could result in

failure of the hydraulics systems, jammed flight controls, loss of

electrical power, or other combinations of failures; and consequent

reduced controllability of the airplane, accomplish the following:

(a) For airplanes equipped with a Bendix main wheel assembly

having part number (P/N) 2601571-1, serial number (S/N) B-5999 or

lower: Within 180 days after the effective date of this AD,

accomplish the actions specified in paragraphs (a)(1) and (a)(2) of

this AD, in accordance with Bendix Service Information Letter (SIL)

392, Revision 1, dated November 15, 1979.

(1) Remove any outboard wheel half having S/N H-999 or lower,

and replace it with an outboard wheel half having P/N 2607047; and

(2) Remove any inboard wheel half having S/N H-1799 or lower,

and replace it with a wheel half having P/N 2607046.

(b) For airplanes equipped with a Bendix main wheel assembly

having P/N 2601571, S/N B0001 through B5999 inclusive, accomplish

the following:

(1) Within 180 days after the effective date of this AD, and

thereafter at each tire change, accomplish the actions specified in

paragraphs (b)(1)(i), (b)(1)(ii), and (b)(1)(iii) of this AD, in

accordance with the Accomplishment Instructions of Allied Signal

Service Bulletin No. 737-32-026, dated April 26, 1988, including

Attachments 1 and 2.

(i) Clean any outboard wheel half having P/N 2601454, S/N H0001

through H1049 inclusive, and any inboard wheel half having P/N

2601567, S/N H0001 through H1799 inclusive; and

(ii) Inspect the wheel halves for corrosion or missing paint in

large areas, strip or remove any paint, and remove any corrosion;

and

(iii) Perform an eddy current inspection to detect cracks.

(2) If any cracking is found during the inspections required by

this paragraph, prior to further flight, repair or replace the wheel

halves with serviceable wheel halves in accordance with procedures

specified in the Component Maintenance Manual.

(c) As of the effective date of this AD, no person shall install

an outboard wheel half having S/N H-999 or lower, or an inboard

wheel half having S/N H-1799 or lower, on a main wheel assembly

having P/N 2601571, S/N B0001 through B5999 inclusive, on any

airplane.

(d) 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.

(e) 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. 96-21884 Filed 8-23-96; 9:03 am]

BILLING CODE 4910-13-U