Airworthiness Directives; McDonnell Douglas Model DC-10-10, -15, -30, and -40 Series Airplanes and KC-10A (Military) Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-221-AD]

Airworthiness Directives; McDonnell Douglas Model DC-10-10, -15,

-30, and -40 Series Airplanes and KC-10A (Military) 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 certain McDonnell Douglas Model

DC-10-10, -15, -30, and -40 series airplanes and KC-10A (military)

airplanes. This proposal would require inspections to detect fatigue-

related cracking in certain areas of the horizontal stabilizer; and

repair of cracked parts. This proposal would also require installation

of terminating modifications, which, when accomplished, would eliminate

the repetitive inspections. This proposal is prompted by reports of

fatigue-related cracks found on the horizontal stabilizer. The actions

specified by the proposed AD are intended to prevent loss of the load

carrying and fail safe capability of the horizontal stabilizer, damage

to the adjacent structure, and subsequent reduced structural integrity

of the airplane.

DATES: Comments must be received by May 23, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 93-NM-221-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056. Comments may be inspected at this

location between 9 a.m. and 3 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,

CA 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 (ACO), 3229 East Spring

Street, Long Beach, California.

FOR FURTHER INFORMATION CONTACT: Wahib Mina, Aerospace Engineer,

Airframe Branch, ANM-121L, FAA, Transport Airplane Directorate, Los

Angeles ACO, 3229 East Spring Street, Long Beach, California 90806-

2425; telephone (310) 988-5324; 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 93-NM-221-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. 93-NM-221-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The manufacturer reports that fatigue-related cracks have been

found on the horizontal stabilizer on several McDonnell Douglas Model

DC-10-10, -15, -30, and -40 series airplanes and KC-10A (military)

airplanes. One operator reported two instances of fatigue-related

cracks on the forward spar upper cap near the closing rib on the

horizontal stabilizer on airplanes that had accumulated approximately

22,643 landings. Two operators reported three cases of fatigue-related

cracks in the forward upper skin panel in the outboard section of the

horizontal stabilizer on airplanes that had accumulated between 17,339

and 19,627 total landings. This skin panel is located immediately aft

of (and attaches to) the forward spar upper cap on the horizontal

stabilizer. Investigation by the manufacturer has revealed that these

cracks are the result of fatigue-related stress. Fatigue-related cracks

in the outboard section of the horizontal stabilizer, if not detected

and corrected in a timely manner, could result in loss of the load

carrying and fail safe capability of the forward spar upper caps and

the forward upper skin panels, damage to the adjacent structure, and

subsequent reduced structural integrity of the airplane.

The FAA has reviewed and approved McDonnell Douglas DC-10 Service

Bulletin 55-24, dated October 25, 1993, that describes procedures for

repetitive eddy current inspections to detect fatigue-related cracking

in the forward spar upper cap of the horizontal stabilizer. The service

bulletin also describes procedures for accomplishment of a preventative

modification for the forward spar upper cap. The preventative

modification entails rework of the fastener holes of the forward spar

upper cap. Incorporation of this preventative modification would

eliminate the need for repetitive inspections of the forward spar upper

cap. Accomplishment of this preventative modification will restore the

structural integrity of the forward spar upper cap.

The FAA has also reviewed and approved McDonnell Douglas DC-10

Service Bulletin 55-25, dated October 25, 1993, that describes

procedures for performing repetitive eddy current inspections to detect

fatigue-related cracking in the forward upper skin panel of the

horizontal stabilizer. The service bulletin also describes procedures

for accomplishment of a preventative modification for the forward upper

skin panel. The preventative modification entails rework of the

fastener holes of the forward upper skin panel. Incorporation of this

preventative modification would eliminate the need for repetitive

inspections of the forward upper skin panel. Accomplishment of this

preventative modification will restore the structural integrity of the

forward upper skin panel.

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 repetitive eddy current inspections to detect

fatigue-related cracking on the forward spar upper caps and the forward

upper skin panels in the outboard section of the horizontal stabilizer.

The proposed AD would also require that cracked parts be repaired in

accordance with a method approved by the FAA. This proposal would also

require accomplishment of preventative modifications, which, when

accomplished, would terminate the repetitive inspections of the forward

spar upper caps and the forward upper skin panels. The inspections and

modifications would be required to be accomplished in accordance with

the service bulletins described previously.

There are approximately 427 Model DC-10-10, -15, -30, and -40

series airplanes and KC-10A (military) 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 accomplishment of the proposed inspection would take

approximately 3 work hours per airplane, at an average labor charge of

$55 per work hour. Based on these figures, the total cost impact of the

proposed inspection actions on U.S. operators is estimated to be

$39,765, or $165 per airplane, per inspection cycle.

The accomplishment of the proposed modification of the forward spar

upper cap would take approximately 248 work hours per airplane.

Likewise, the accomplishment of the proposed modification of the

forward upper skin panel would take approximately 248 work hours per

airplane. The average labor rate is $55 per work hour. Required parts

would cost approximately $10,600 per airplane. Based on these figures,

the total cost impact of the proposed modification actions AD on U.S.

operators is estimated to be $9,129,080, or $37,880 per airplane.

The FAA recognizes that the proposed modifications would require a

large number of work hours to accomplish. However, the 5-year

compliance time specified in paragraph (d) of this proposed AD should

allow ample time for the modifications to be accomplished

coincidentally with scheduled major airplane inspection and maintenance

activities, thereby minimizing the costs associated with special

airplane scheduling.

The total 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 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 14

CFR part 39 of the Federal Aviation Regulations 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 93-NM-221-AD.

Applicability: Model DC-10-10, -15, -30, and -40 series

airplanes and KC-10A (military) airplanes; as listed in McDonnell

Douglas DC-10 Service Bulletins 55-24 and 55-25, both dated October

25, 1993; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent reduced structural integrity of the airplane,

accomplish the following:

(a) For Model DC-10-10 and -15 series airplanes: Prior to the

accumulation of 18,000 total landings, or within 90 days after the

effective date of this AD, whichever occurs later, unless previously

accomplished within the last 4,500 landings, perform an eddy current

inspection to detect fatigue-related cracking of the forward spar

upper caps on the horizontal stabilizer, in accordance with

McDonnell Douglas Service Bulletin 55-24, dated October 25, 1993.

(1) If any crack is detected, prior to further flight, repair

the crack in accordance with a method approved by the Manager, Los

Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane

Directorate. After repair, repeat the inspection thereafter at

intervals not to exceed 4,500 landings in accordance with the

service bulletin.

(2) If no crack is detected, repeat the inspection thereafter at

intervals not to exceed 4,500 landings in accordance with the

service bulletin.

(b) For Model DC-10-10 and -15 series airplanes: Prior to the

accumulation of 10,000 total landings, or within 120 days after the

effective date of this AD, whichever occurs later, unless previously

accomplished within the last 4,500 landings, perform an eddy current

inspection to detect fatigue-related cracking of the forward upper

skin panel of the horizontal stabilizer, in accordance with

McDonnell Douglas Service Bulletin 55-25, dated October 25, 1993.

(1) If any crack is detected, prior to further flight, repair

the crack in accordance with a method approved by the Manager, Los

Angeles ACO, FAA, Transport Airplane Directorate. After repair,

repeat the inspection thereafter at intervals not to exceed 4,500

landings in accordance with the service bulletin.

(2) If no crack is detected, repeat the inspection thereafter at

intervals not to exceed 4,500 landings in accordance with the

service bulletin.

(c) For Model DC-10-30 and -40 series airplanes: Prior to the

accumulation of 17,500 total landings, or within 120 days after the

effective date of this AD, whichever occurs later, unless previously

accomplished within the last 4,500 landings, perform an eddy current

inspection to detect fatigue-related cracking of the forward upper

skin panel of the horizontal stabilizer, in accordance with

McDonnell Douglas Service Bulletin 55-25, dated October 25, 1993.

(1) If any crack is detected, prior to further flight, repair

the crack in accordance with a method approved by the Manager, Los

Angeles ACO, FAA, Transport Airplane Directorate. After repair,

repeat the inspection thereafter at intervals not to exceed 4,500

landings in accordance with the service bulletin.

(2) If no crack is detected, repeat the inspection thereafter at

intervals not to exceed 4,500 landings in accordance with the

service bulletin.

(d) For all airplanes: Within 5 years after the effective date

of this AD, install the preventative modifications for the forward

spar upper cap on the horizontal stabilizer, in accordance with

McDonnell Douglas Service Bulletin 55-24, dated October 25, 1993;

and for the forward upper skin panel on the horizontal stabilizer,

in accordance with McDonnell Douglas Service Bulletin 55-25, dated

October 25, 1993. Accomplishment of these preventative modifications

in accordance with these service bulletins constitutes terminating

action for the repetitive inspections required by this AD.

(e) 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 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.

(f) Special flight permits may be issued in accordance with

Federal Aviation Regulations (FAR) 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 March 24, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-7493 Filed 3-29-94; 8:45 am]

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