Airworthiness Directives; McDonnell Douglas Model MD-90 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-209-AD]

RIN 2120-AA64

Airworthiness Directives; McDonnell Douglas Model MD-90 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 certain McDonnell Douglas Model

MD-90 series airplanes. This proposal would require a one-time detailed

visual inspection to detect fatigue cracking of certain longerons and

the attaching frames of the lower left nose; and repair, if necessary.

The proposal also would require installation of a preventive

modification. This proposal is prompted by several reports of fatigue

cracking of certain longerons and the attaching frames. The actions

specified by the proposed AD are intended to prevent such fatigue

cracking, which could result in reduced structural integrity of the

fuselage, and consequent loss of pressurization of the airplane.

DATES: Comments must be received by December 13, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-114,

Attention: Rules Docket No. 99-NM-209-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 The Boeing Company, Douglas Products Division, 3855

Lakewood Boulevard, Long Beach, California 90846, Attention: Technical

Publications Business Administration, Dept. C1-L51 (2-60). 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, 3960

Paramount Boulevard, Lakewood, California.

FOR FURTHER INFORMATION CONTACT: Carl Fountain, Aerospace Engineer,

Airframe Branch, ANM-120L; FAA, Los Angeles Aircraft Certification

Office, 3960 Paramount Boulevard, Lakewood, California 90712; telephone

(562) 627-5222; fax (562) 627-5210.

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 99-NM-209-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-114, Attention: Rules

Docket No. 99-NM-209-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The FAA has received reports indicating that cracking of the

fuselage longerons-to-frame attachment holes occurred on three

McDonnell Douglas Model DC-9 series airplanes. The fatigue cracking was

found between longerons 22 though 26 on the left side at stations

Y=160.000 and Y=200.000. These airplanes had accumulated between 59,110

and 74,445 total flight cycles. The cracking of the longeron segments

has been attributed to fatigue. Such fatigue cracking, if not

corrected, could result in reduced structural integrity of the

fuselage, and consequent loss of pressurization of the airplane.

The fuselage longerons-to-frame attachments of McDonnell Douglas

Model MD-90 series airplanes are similar to those of the affected

McDonnell Douglas Model DC-9 series airplanes. Therefore, the Model MD-

90 may be subject to the same unsafe condition.

Other Relevant Rulemaking

On November 20, 1998, the FAA issued AD 98-24-33, amendment 39-

10919 (63 FR 66739, December 3, 1998), applicable to certain McDonnell

Douglas DC-9 and MD-88 series airplanes, to require a one-time visual

inspection to detect fatigue cracks between longerons 22 through 26 and

the attaching frames, and corrective action, if necessary. However,

this proposed AD would not affect the current requirements of that

previously issued AD.

Explanation of Relevant Service Information

The FAA has reviewed and approved McDonnell Douglas Service

Bulletin MD90-53-004, dated August 20, 1998, which describes procedures

for a one-time detailed visual inspection to detect cracking of

longerons 22 through 26 and the attaching frames at stations Y=160.000

and Y=200.000 of the lower left nose, and repair, if necessary. The

service bulletin also provides procedures for a preventive modification

(i.e., installation of clips and doublers under longeron flanges and

shims longeron) to relieve preloads.

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 accomplishment of the actions specified in

the service bulletin described previously.

Cost Impact

There are approximately 7 airplanes of the affected design in the

worldwide fleet. The FAA estimates that 6 airplanes of U.S. registry

would be affected by this proposed AD.

[[Page 57790]]

It would take approximately 1 work hour per airplane to accomplish

the proposed inspection, at an average labor rate of $60 per work hour.

Based on these figures, the cost impact of the inspection proposed by

this AD on U.S. operators is estimated to be $360, or $60 per airplane.

It would take approximately 6 work hours per airplane to accomplish

the proposed modification, at an average labor rate of $60 per work

hour. Parts would cost approximately $312 per airplane. Based on these

figures, the cost impact of the modification proposed by this AD on

U.S. operators is estimated to be $4,032, or $672 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.

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:

McDonnell Douglas: Docket 99-NM-209-AD.

Applicability: Model MD-90 series airplanes, as listed in

McDonnell Douglas Service Bulletin MD90-53-004, dated August 20,

1998; 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 fatigue cracking of longerons 22 through 26 and the

attaching frames, which could result in reduced structural integrity

of the fuselage, and consequent loss of pressurization of the

airplane; accomplish the following:

Inspection and Modification

(a) Prior to the accumulation of 40,000 total landings, or

within 24 months after the effective date of this AD, whichever

occurs later: Perform a detailed visual inspection to detect

cracking of longerons 22 through 26 (inclusive) and the respective

attaching frames at station frames Y=160.000 and Y=200.000 of the

left lower nose, in accordance with McDonnell Douglas Service

Bulletin MD90-53-004, dated August 20, 1998.

Note 2: For the purposes of this AD, a detailed visual

inspection is defined as: ``An intensive visual examination of a

specific structural area, system, installation, or assembly to

detect damage, failure, or irregularity. Available lighting is

normally supplemented with a direct source of good lighting at

intensity deemed appropriate by the inspector. Inspection aids such

as mirror, magnifying lenses, etc., may be used. Surface cleaning

and elaborate access procedures may be required.''

(1) If no cracking is detected: Prior to further flight, install

clips and doublers under the longeron flanges and shim the longerons

in accordance with the service bulletin.

(2) If any cracking is detected: Prior to further flight, repair

the cracks and install clips and doublers under the longeron flanges

and shim the longerons in accordance with the service bulletin.

Alternative Methods of Compliance

(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 3: Information concerning the existence of approved

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

obtained from the Manager, Los Angeles ACO.

Special Flight Permits

(c) 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 October 21, 1999.

D.L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-28079 Filed 10-26-99; 8:45 am]

BILLING CODE 4910-13-U