Airworthiness Directives; McDonnell Douglas Model DC-9-80 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-149-AD]

Airworthiness Directives; McDonnell Douglas Model DC-9-80 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 McDonnell Douglas Model DC-9-80

series airplanes. This proposal would require the replacement of

certain suspect horizontal stabilizer primary trim motors. This

proposal is prompted by an analysis which revealed that certain

incorrectly manufactured motor shafts could fail prematurely and, in

turn, cause the primary trim motor to fail. The actions specified by

the proposed AD are intended to prevent such failures of the primary

trim motor, which could ultimately result in reduced controllability of

the airplane.

DATES: Comments must be received by December 13, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-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 McDonnell Douglas Corporation, P.O. Box 1771, Long Beach,

California 90801-1771, Attention: Business Unit Manager, Technical

Administrative support, Dept. L51, M.C. 2-98. This information may be

examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue,

SW., Renton, Washington; or at FAA, Los Angeles Aircraft Certification

Office, Transport Airplane Directorate, 3229 East Spring Street, Long

Beach, California.

FOR FURTHER INFORMATION CONTACT: Walter Eierman, Aerospace Engineer,

Systems & Equipment Branch, ANM-130L, Los Angeles Aircraft

Certification Office, FAA, Transport Airplane Directorate, 3229 East

Spring Street, Long Beach, California 90806-2425; telephone (310) 988-

5336; fax (310) 988-5210.

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-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. 94-NM-149-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

McDonnell Douglas Corporation and a supplier of horizontal

stabilizer primary trim motors recently conducted an analysis of the

horizontal stabilizer primary trim motors installed on Model DC-9-80

series airplanes. Results of this analysis have revealed a condition in

the motor that could lead to its premature failure. This condition has

been attributed to the omission of a hardening process (heat treatment)

during the manufacture of a specific lot of motor output shafts.

Without this hardening process, the defective output shafts may

experience excessive wear, which could lead to failure of the shaft

and, consequently, failure of the trim motor. A shaft failure in the

primary trim motor could also result in the inability of the trim

gearbox to transmit the input from the alternate trim motor. This

condition, if not corrected, could result in the loss of all stabilizer

trim and subsequent reduced controllability of the airplane. No

failures have actually occurred in service, however.

The FAA has reviewed and approved McDonnell Douglas MD-80 Alert

Service Bulletin A27-342, dated August 4, 1994, which describes

procedures for inspecting the horizontal stabilizer primary trim motor

to determine if the motor is one having a suspect serial number, and

replacing the suspect motors.

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 inspecting the horizontal stabilizer primary

trim motor to determine if the motor is one having a suspect serial

number, and replacing the suspect motors. The actions would be required

to be accomplished in accordance with the service bulletin described

previously.-

There are approximately 26 Model DC-9-80 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 13

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

it would take approximately .5 work hour per airplane to accomplish the

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

Based on these figures, the total cost impact of the proposed

inspection requirements of this AD on U.S. operators is estimated to be

$357.50, or $27.50 per airplane. -

Replacement of suspect motors would require 4.5 work hours to

accomplish, at an average labor charge of $55 per work hour. Required

replacement parts would be provided by Sundstrand Electric Power

Systems (the manufacturer of the horizontal stabilizer primary trim

motors) at no charge to operators. Based on these figures, the total

cost impact of the proposed replacement requirements of this AD on U.S.

operators is estimated to be $3,217.50, or $247.50 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. -

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 adding the following new

airworthiness directive:

McDonnell Douglas: Docket 94-NM-149-AD.

-Applicability: Model DC-9-80 series airplanes; as listed in

McDonnell Douglas MD-80 Alert Service Bulletin A27-342, dated August

4, 1994; certificated in any category. -

Compliance: Required as indicated, unless accomplished

previously. -

To prevent failure of the horizontal stabilizer primary trim

motor, accomplish the following: -

(a) Within 6 months after the effective date of this AD, conduct

a visual inspection of the horizontal stabilizer primary trim motor

to determine if the motor is identified with one of the suspect

serial numbers listed in McDonnell Douglas MD-80 Alert Service

Bulletin A27-342, dated August 4, 1994. Conduct this inspection in

accordance with the procedures specified in that service bulletin. -

(1) If the horizontal stabilizer primary trim motor is not

identified with a suspect serial number, no further action is

required by this AD. -

(2) If the horizontal stabilizer primary trim motor is

identified with a suspect serial number, prior to further flight,

replace the motor in accordance with the service bulletin. -

(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, Los Angeles 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, Los Angeles ACO.

-Note: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Los Angeles 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 October 12, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-25691 Filed 10-17-94; 8:45 am]

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