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

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-79-AD]

Airworthiness Directives; McDonnell Douglas Model DC-10 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 all McDonnell Douglas Model DC-10

series airplanes and KC-10A (military) airplanes. This proposal would

require inspections to detect cracking of H-11 attach bolts of the

upper vertical stabilizer and replacement of these bolts and associated

nuts with Inconel bolts and nuts. This proposal is prompted by reports

of failure of the attach bolts of the upper vertical stabilizer due to

stress corrosion. The actions specified by the proposed AD are intended

to prevent undetected cracked or failed attach bolts that may lead to

reduced structural integrity of the vertical stabilizer.

DATES: Comments must be received by November 10, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-79-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, Department 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: Maureen Moreland, Aerospace Engineer,

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

Angeles Aircraft Certification Office, 3229 East Spring Street, Long

Beach, California; telephone (310) 988-5238; 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-79-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-79-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

On August 25, 1993, the FAA issued AD 93-17-09, Amendment 39-8680

(58 FR 54949, October 25, 1993), which is applicable to McDonnell

Douglas Model DC-10 series airplanes and KC-10A (military) airplanes.

That AD requires the implementation of a Structural Inspection Document

(SID) program of structural inspections to detect fatigue cracking, and

repair or replacement, as necessary, to ensure the continued

airworthiness of these airplanes as they approach the manufacturer's

original fatigue design life goal. AD 93-17-09 requires inspection of

the attach bolts of the upper vertical stabilizer [designated Principal

Structural Element (PSE) 55.10.001/002 in McDonnell Douglas Report

Number L26-012, ``DC-10 Supplemental Inspection Document,'' which is

referenced in that AD as the appropriate source of service information]

under the fleet leader operator sampling criteria. The fatigue life for

these attach bolts is (Nth) 119,334 flight hours. The sampling

period for this PSE started in September 1989, and will end in June

2001. Sampling inspections are to be accomplished within that interval

for airplanes in the candidate fleet that have accumulated more than

59,667 total flight hours (Nth/2).

The inspection threshold for the SID program was based upon a

fatigue analysis conducted by the manufacturer. The FAA is not aware of

any operator having, as yet, accomplished the inspection of these bolts

for the purpose of complying with the requirements of AD 93-17-09.

McDonnell Douglas has advised the FAA that the planning data contained

in Volume III of the SID will be revised to indicate that H-11 bolts

have been replaced with new Inconel bolts.

Since the issuance of that AD, operators of Model DC-10 series

airplanes have recently reported that the attach bolts of the upper

vertical stabilizer had failed on several in-service airplanes. These

failures had occurred on airplanes that had accumulated between 40,000

total flight hours and 67,000 total flight hours. The attach bolts and

associated nuts on these airplanes were made of H-11 material, which is

susceptible to failure due to stress corrosion. The FAA has determined

that replacement of the H-11 bolts and associated nuts with Inconel

bolts and associated nuts will eliminate the possibility of failure due

to stress corrosion. Failure of the attach bolts in the upper vertical

stabilizer, if not corrected, could compromise the structural integrity

of the vertical stabilizer.

The FAA has reviewed and approved Revision 1, dated March 8, 1991,

and Revision 2, dated August 4, 1994, of McDonnell Douglas DC-10

Service Bulletin 55-20, which describe procedures for repetitive

ultrasonic inspections at 12-month intervals to detect cracking in H-11

attach bolts of the upper vertical stabilizer, and replacement of H-11

attach bolts and associated nuts with Inconel attach bolts and

associated nuts.

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 ultrasonic inspections at 18-month intervals

to detect cracking in H-11 attach bolts of the upper vertical

stabilizer, and replacement of H-11 attach bolts and associated nuts

with Inconel attach bolts and associated nuts. The actions would be

required to be accomplished in accordance with the procedures specified

in the service bulletins described previously.

Although the referenced service bulletins recommend that these

inspections be performed at 12-month intervals, the FAA has determined

that 18-month intervals will not adversely affect safety and will allow

these repetitive inspections to be performed at a base during regularly

scheduled maintenance where special equipment and trained maintenance

personnel will be available.

There are approximately 426 McDonnell Douglas Model DC-10 series

airplanes and KC-10A (military) airplanes of the affected design in the

worldwide fleet. The FAA estimates that 269 airplanes of U.S. registry

would be affected by this proposed AD.

It would take approximately 2 work hours per airplane to accomplish

the proposed inspections at an average labor rate of $55 per work hour.

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

proposed by this AD on U.S. operators is estimated to be $29,590, or

$110 per airplane, per inspection cycle.

It would take approximately 8 work hours per airplane to accomplish

the proposed replacements at an average labor rate of $55 per work

hour. Required parts would cost approximately $9,009 per airplane.

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

proposed by this AD on U.S. operators is estimated to be $2,541,781, or

$9,449 per airplane.

Based on the above figures, the total cost impact of the

inspections and replacements proposed by this AD on U.S. operators is

estimated to be $2,571,371, or $9,559 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 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 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, most

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.

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-79-AD.

Applicability: All Model DC-10-10, -10F, -15, -30, -30F, -40,

and -40F series airplanes, and KC-10A (military) airplanes;

certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent undetected cracked or failed attach bolts that may lead

to reduced structural integrity of the vertical stabilizer, accomplish

the following:

(a) Within 12 months after the effective date of this AD, perform

an ultrasonic inspection to detect cracking in the attach bolts of the

upper vertical stabilizer, in accordance with McDonnell Douglas DC-10

Service Bulletin 55-20, Revision 2, dated August 4, 1994, unless

accomplished within the last 18 months prior to the effective date of

this AD in accordance with McDonnell Douglas DC-10 Service Bulletin 55-

20, Revision 1, dated March 8, 1991, or Revision 2, dated August 4,

1994.

(1) If no cracking is detected in any bolt, repeat the

inspection of the uncracked bolt thereafter at intervals not to

exceed 18 months, until the requirements of paragraph (c) of this AD

are accomplished.

(2) If cracking is detected in any bolt, prior to further

flight, replace the cracked bolt and associated nut with a new

Inconel attach bolt and associated nut, in accordance with the

service bulletin. No further action is required by this AD for the

new Inconel bolts and associated nuts.

(b) Compliance with the inspections required by paragraph (a) of

this AD constitutes compliance with the inspections and reports

required by paragraph (b) of AD 93-17-09, Amendment 39-8680, for

Principal Structural Element (PSE) 55.10.001/002. However, after

installation of new Inconel bolts and associated nuts, in accordance

with the requirements of paragraphs (a) and (c) of this AD, PSE

55.10.001/002 must continue to be inspected in accordance with AD

93-17-09.

(c) Within 5 years after the effective date of this AD, replace

all H-11 attach bolts and associated nuts of the upper vertical

stabilizer with new Inconel attach bolts and associated nuts, in

accordance with McDonnell Douglas DC-10 Service Bulletin 55-20,

Revision 1, dated March 8, 1991; or Revision 2, dated August 4,

1994. Such replacement constitutes terminating action for the

requirements of this AD.

(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, 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.

(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 September 13, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-23100 Filed 9-16-94; 8:45 am]

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