Airworthiness Directives; McDonnell Douglas Model DC-8-70 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-65-AD]

Airworthiness Directives; McDonnell Douglas Model DC-8-70 Series

Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to all McDonnell Douglas Model

DC-8-70 series airplanes, that currently requires replacement of all

attachment screws at the exhaust nozzle plug splice, and a check of nut

plates for running torque and replacement of nut plates, if necessary.

This action would require modification of the engine exhaust plug

assemblies; when accomplished, this modification would terminate the

need for the currently required replacement and check. This proposal is

prompted by reports of loose or missing attachments at the splice joint

of the engine forward and aft exhaust plugs, and loss of the rear

exhaust plug following an engine bird strike. The actions specified by

the proposed AD are intended to prevent reduced integrity of the engine

exhaust plug installation, which may lead to separation of exhaust

plugs from the airplane, and create a hazard to persons and property on

the ground.

DATES: Comments must be received by September 9, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-65-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 the FAA, Transport Airplane Directorate,

Los Angeles Aircraft Certification Office, 3229 East Spring Street,

Long Beach, California.

FOR FURTHER INFORMATION CONTACT: Robert Baitoo, Aerospace Engineer,

Propulsion Branch, ANM-141L, FAA, Transport Airplane Directorate, Los

Angeles Aircraft Certification Office, 3229 East Spring Street, Long

Beach, California 90806-2425; telephone (310) 988-5245; 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-65-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-65-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

On January 17, 1983, the FAA issued AD 83-02-05, amendment 39-4544

(48 FR 5539, February 7, 1983), applicable to all McDonnell Douglas

Model DC-8-70 series airplanes, to require replacement of all

attachment screws at the exhaust nozzle plug splice. That AD also

requires a check of nut plates for running torque and replacement of

nut plates not meeting the minimum run down torque of five inch-pounds.

That action was prompted by reports of loose or missing attachment

screws at the plug splice joint. In one reported incident, the exhaust

plug nozzle separated from one engine while the airplane was in flight.

The requirements of that AD are intended to prevent separation of the

exhaust nozzle plug from the engine.

Since the issuance of that AD, three operators have reported four

incidents of loose or missing attachments at the splice joint of the

engine forward and aft exhaust plugs. These discrepancies were found on

airplanes subsequent to the accomplishment of AD 83-02-05. One operator

reported loss of the rear exhaust plug on one airplane after the engine

sustained a bird strike. Investigation revealed that the cause of these

loose or missing splice joint attachments was attributed to higher

temperatures and vibration effects of the engine exhaust.

Operators also reported loose nuts at the forward plug-to-engine

turbine flange attachments. The cause of these loose nuts has been

attributed to high temperature and incompatibility of the nut threads

with associated threaded studs.

These conditions, if not corrected, could result in reduced

integrity of the engine exhaust plug installation, which may lead to

separation of exhaust plugs from the airplane, and create a hazard to

persons and property on the ground.

The FAA has reviewed and approved McDonnell Douglas DC-8-70 Service

Bulletin 78-112, Revision 2, dated March 8, 1994, that describes

procedures for modification of the engine exhaust plug assemblies. The

modification entails replacement of existing fasteners with permanent

fasteners having larger diameters; this will serve to strengthen the

splice installation and minimize the possibility of loose splice joint

fasteners. Further, this modification entails replacement of existing

nuts with nuts that are less susceptible to the effects of higher

temperatures and have compatible thread pitch, which minimizes the

possibility of forward plug-to-engine turbine attachments becoming

loose.

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 supersede AD 83-02-05 to require modification of the

engine exhaust plug assemblies. The actions would be required to be

accomplished in accordance with the service bulletin described

previously. Accomplishment of this modification would constitute

terminating action for the currently required replacement and check.

There are approximately 110 Model DC-8-70 series airplanes of the

affected design in the worldwide fleet. The FAA estimates that 78

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

it would take approximately 46 work hours per airplane to accomplish

the proposed modification, and that the average labor rate is $55 per

work hour. Required parts would cost approximately $21,400 per

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

AD on U.S. operators is estimated to be $1,866,540, or $23,930 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 removing amendment 39-4544 (48 FR

5539, February 7, 1983), and by adding a new airworthiness directive

(AD), to read as follows:

McDonnell Douglas: Docket 94-NM-65-AD. Supersedes AD 83-02-05,

Amendment 39-4544.

Applicability: All Model DC-8-70 series airplanes, certificated

in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent reduced integrity of the engine exhaust plug

installation, which may lead to separation of exhaust plugs from the

airplane, and create a hazard to persons and property on the ground,

accomplish the following:

(a) Within 300 flight hours after February 7, 1983 (the

effective date of AD 83-02-05, amendment 39-4544), accomplish the

procedures specified in paragraphs (a)(1) and (a)(2) of this AD in

accordance with McDonnell Douglas DC-8-70 Alert Service Bulletin

A78-107, dated November 30, 1982; McDonnell Douglas DC-8-70 Service

Bulletin 78-107, dated January 16, 1984; or McDonnell Douglas DC-8-

70 Service Bulletin 78-107, Revision 1, dated June 12, 1984.

(1) Replace all NAS560XK4-5 screws with NAS560XK4-4 screws at

the exhaust nozzle plug splice.

(2) Check nut plates for running torque and replace all nut

plates not meeting the minimum run down torque of five inch-pounds.

(b) Within 24 months after the effective date of this AD, modify

the engine exhaust plug assemblies in accordance with McDonnell

Douglas DC-8-70 Service Bulletin 78-112, Revision 2, dated March 8,

1994. Accomplishment of this modification constitutes terminating

action for the replacement and check requirements of paragraph (a)

of this AD.

(c) 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.

(d) 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.

Issued in Renton, Washington, on July 20, 1994.

Darrell M. Pederson, Acting Manager,

Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 94-18226 Filed 7-26-94; 8:45 am]

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