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

SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to certain McDonnell Douglas Model DC-10-10, -15, -30, and -

40 series airplanes and KC-10A (military) airplanes, that requires

inspections to detect fatigue-related cracking in certain areas of the

horizontal stabilizer; and repair of cracked parts. It also requires

installation of terminating modifications, which, when accomplished,

would eliminate the repetitive inspections. This amendment is prompted

by reports of fatigue-related cracks found on the horizontal

stabilizer. The actions specified by this 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, due to the problems associated

with fatigue cracking.

DATES: Effective October 31, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of November 3, 1994.

ADDRESSES: The service information referenced in this AD 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 Federal Aviation Administration (FAA), Transport

Airplane Directorate, Rules Docket, 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; or at the Office of the Federal Register, 800 North Capitol

Street, NW., suite 700, Washington, DC.

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: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an 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 was published as a notice of proposed rulemaking (NPRM) in

the Federal Register on March 30, 1994 (59 FR 14800). That action

proposed to require inspections to detect fatigue-related cracking in

certain areas of the horizontal stabilizer; and repair of cracked

parts. It also proposed to require the installation of certain

terminating modifications that would eliminate the need for the

repetitive inspections.

Immediate Adoption of This Regulation

Since issuance of the NPRM, one operator has reported finding a

crack in the area of the forward spar upper cap on the horizontal

stabilizer on a Model DC-10-10 series airplane that had accumulated

approximately 16,000 landings. This evidence indicates that fatigue

cracking may begin in this area much earlier than what was previously

considered. In light of this, the FAA has reconsidered the compliance

time proposed for the initiation of inspections to detect cracking in

this subject area on these airplanes. The FAA now has determined that

the initiation of inspections of Model DC-10-10 and -15 series

airplanes must begin prior to the accumulation of 12,000 total landings

or 90 days after the effective date of this AD, whichever occurs later.

(The compliance time for this action that was proposed in the notice

was 18,000 total landings.) The lowered threshold of 12,000 total

landings is necessary to ensure that cracking is detected and corrected

in a timely manner, and to prevent the loss of load-carrying and fail

safe capability of the horizontal stabilizer due to the problems

associated with fatigue cracking. The compliance time for the

inspections specified in paragraph (a) of this final rule has been

revised accordingly.

In making this revision, the FAA finds that, with respect to the

reduced compliance threshold, a situation exists that requires the

immediate adoption of this regulation. Therefore, it is found that

notice and opportunity for prior public comment hereon are

impracticable, and that good cause exists for making this amendment

effective in less than 30 days.

Comments Invited

Although this action is in the form of a final rule that involves

requirements affecting flight safety and, thus, was not preceded by

notice and an opportunity for public comment, comments are invited on

this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All

communications received on or before the closing date for comments will

be considered, and this rule may be amended in light of the comments

received. Factual information that supports the commenter's ideas and

suggestions is extremely helpful in evaluating the effectiveness of the

AD action and determining whether additional rulemaking action would be

needed.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the rule that might

suggest a need to modify the 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 that

summarizes each FAA-public contact concerned with the substance of this

AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this rule 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.

Discussion of Comments Received to the NPRM

Interested persons have been afforded an opportunity to participate

in the making of a portion of this amendment. Due consideration has

been given to the comments received.

One commenter supports the proposal.

Several commenters request that the proposed rule be revised to

exclude the Models DC-10-30 and -40 from the applicability until more

information is gathered to substantiate that these airplanes are

subject to the addressed unsafe condition. These commenters point out

that cracks have been reported on Model DC-10-10 series airplanes only.

One commenter states that the airframe manufacturer previously had

requested that operators of Model DC-10 series airplanes inspect their

airplanes for cracking and, as a result, none was found on any models

other than the Model DC-10-10 and -15 series. Another commenter

suggests that the spar cap and skin panel installed on Models DC-10-30

and -40 are thicker than those on Models DC-10-10 and -15; therefore,

the possibility of these items cracking on the Model DC-10-30 and -40

airplanes is very low.

The FAA does not concur with these commenters' request. Although

fatigue cracking may not have been detected on in-service Model DC-10-

30 and -40 series airplanes, the airframe manufacturer has conducted

load, fatigue, and damage-tolerance analyses, which indicate that

fatigue-related cracking is likely to occur on all Model DC-10 series

airplanes as these airplanes accumulate flight cycles. The compliance

thresholds specified in this AD, as well as the compliance times for

the required initial and repetitive inspections, were developed in

consideration of these analyses and with the participation of the

airframe manufacturer.

Several commenters request that the rule be revised to give credit

for visual inspections of the area that were performed previously, and

to add a visual inspection as an option for accomplishment of the

initial eddy current inspection. These commenters state that a damage

tolerance assessment conducted by the airframe manufacturer has shown

that an initial visual inspection will ensure that the structural

integrity of the horizontal stabilizer spar cap and skin is maintained.

Additionally, by permitting a visual inspection to be performed, which

takes less time and materials than an eddy current inspection, the

economic impact of non-scheduled maintenance and removal of aircraft

from service would be reduced for operators, as well as the

corresponding inconvenience for the traveling public.

The FAA concurs with these commenters' request. Subsequent to the

issuance of the notice, the FAA reviewed and approved Revision 1 to

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

August 3, 1994. These revised service bulletins contain revised

instructions for accomplishing the eddy current inspection (to make it

less complicated), and instructions for performing an optional visual

inspection in lieu of the initial eddy current inspection to determine

if cracks exist in the horizontal stabilizer forward cap and skin

panel. The FAA has revised the final rule to permit operators to

perform this optional visual inspection as the initial inspection only.

All repetitive inspections must be performed using eddy current

techniques.

Several commenters request that the proposed rule be revised to

eliminate the compliance time for the terminating modifications. These

commenters consider that these modifications should be optional instead

of mandatory. Other commenters indicate that fatigue-related cracks are

cycle-dependent, not calendar time-dependent; therefore, it is

inappropriate to impose a calendar time compliance time on a cycle-

dependent phenomenon. The commenters also consider that the proposed

compliance time of five years for installation of the terminating

modifications could be unfair to operators of low-time airplanes,

since, in some cases, an operator could be required to install the

terminating modifications before the airplane has reached the threshold

for the initial inspection.

The FAA does not concur with the commenters' request to allow the

terminating action to be optional. The FAA has determined that long

term continued operational safety will be better assured by design

changes to remove the source of the problem, rather than by repetitive

inspections. Long term inspections may not be providing the degree of

safety assurance necessary for the transport airplane fleet. This,

coupled with a better understanding of the human factors associated

with numerous continual inspections, has led the FAA to consider

placing less emphasis on inspections and more emphasis on design

improvements. The modifications required by this AD are in consonance

with these considerations.

The FAA does acknowledge, however, that the proposed compliance

time for installation of the terminating modifications could present an

unfair situation to operators of low-time airplanes. This was not the

FAA's intent. Therefore, the FAA has revised paragraph (d) of the final

rule to specify modification prior to the accumulation of a certain

number of cycles (depending upon airplane model) or within 5 years,

whichever occurs later.

The FAA has revised paragraphs (a)(1), (b)(1), and (c)(1) of the

final rule to delete the previously proposed requirement to continue

inspections after installation of a repair that has been approved by

the Manager of the Los Angeles Aircraft Certification Office. The FAA

has determined that deletion of this requirement is appropriate, since

some repairs that have been approved have incorporated a terminating

action, thereby eliminating the need for continuing repetitive

inspections.

Cost Impact

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 will be affected by this AD.

The accomplishment of the optional initial visual inspection will

take approximately 1 workhour per airplane per inspection, at an

average labor charge of $55 per workhour. Based on these figures, the

total cost impact of this optional inspection on U.S. operators who

elect to accomplish it is estimated to be $55 per airplane.

The accomplishment of the eddy current inspections will take

approximately 3 workhours per airplane per inspection, at an average

labor charge of $55 per workhour. Based on these figures, the total

cost impact of the inspection requirement on U.S. operators is

estimated to be $39,765, or $165 per airplane, per inspection cycle.

The accomplishment of the modification of the forward spar upper

cap will take approximately 248 workhours per airplane. Likewise, the

accomplishment of the modification of the forward upper skin panel will

take approximately 248 workhours per airplane. The average labor rate

is $55 per workhour. Required parts will cost approximately $10,600 per

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

modification actions AD on U.S. operators is estimated to be

$9,129,080, or $37,880 per airplane.

The FAA recognizes that the required modifications require a large

number of workhours 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

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 adopted herein will 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency

regulation that must be issued immediately to correct an unsafe

condition in aircraft, and that it is not a ``significant regulatory

action'' under Executive Order 12866. It has been determined further

that this action involves an emergency regulation under DOT Regulatory

Policies and Procedures (44 FR 11034, February 26, 1979). If it is

determined that this emergency regulation otherwise would be

significant under DOT Regulatory Policies and Procedures, a final

regulatory evaluation will be prepared and placed in the Rules Docket.

A copy of it, if filed, may be obtained from the Rules Docket at the

location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 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:

94-20-10 McDonnell Douglas: Amendment 39-9039. 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, Revision 1, both

dated August 3, 1994; 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 12,000 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 either an

initial an eddy current inspection or visual inspection to detect

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

horizontal stabilizer, in accordance with McDonnell Douglas DC-10

Service Bulletin 55-24, Revision 1, dated August 3, 1994.

Note 1: Eddy current inspections accomplished in accordance with

McDonnell Douglas DC-10 Service Bulletin 55-24, dated October 25,

1993, are considered acceptable for compliance with this paragraph.

(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.

(2) If no crack is detected, perform repetitive inspections

thereafter in accordance with the service bulletin and in accordance

with the following schedule:

(i) If the initial inspection was performed using visual

techniques, perform an eddy current inspection within 1,000 landings

after the visual inspection. Thereafter, repeat the eddy current

inspection at intervals not to exceed 4,500 landings.

(ii) If the initial inspection was performed using eddy current

techniques, repeat the eddy current inspection thereafter at

intervals not to exceed 4,500 landings.

(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 either an

initial eddy current inspection or visual inspection to detect

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

horizontal stabilizer, in accordance with McDonnell Douglas DC-10

Service Bulletin 55-25, Revision 1, dated August 3, 1994.

Note 2: Eddy current inspections performed in accordance with

McDonnell Douglas DC-10 Service Bulletin 55-25, dated October 25,

1993, are considered acceptable for compliance with this paragraph.

(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.

(2) If no crack is detected, perform repetitive eddy current

inspections thereafter in accordance with the service bulletin and

in accordance with the following schedule:

(i) If the initial inspection was performed using visual

techniques, perform an eddy current inspection within 1,000 landings

after the visual inspection. Thereafter, repeat the eddy current

inspection at intervals not to exceed 4,500 landings.

(ii) If the initial inspection was performed using eddy current

techniques, repeat the eddy current inspection thereafter at

intervals not to exceed 4,500 landings.

(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 either an

initial eddy current inspection or visual inspection to detect

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

horizontal stabilizer, in accordance with McDonnell Douglas DC-10

Service Bulletin 55-25, Revision 1, dated August 3, 1994.

Note 3: Eddy current inspections performed in accordance with

McDonnell Douglas DC-10 Service Bulletin 55-25, dated October 25,

1993, are considered acceptable for compliance with this paragraph.

(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.

(2) If no crack is detected, perform repetitive eddy current

inspections thereafter in accordance with the service bulletin and

in accordance with the following schedule:

(i) If the initial inspection was performed using visual

techniques, perform an eddy current inspection within 1,000 landings

after the visual inspection. Thereafter, repeat the eddy current

inspection at intervals not to exceed 4,500 landings.

(ii) If the initial inspection was performed using eddy current

techniques, repeat the eddy current inspection thereafter at

intervals not to exceed 4,500 landings.

(d) For all airplanes: Install the preventative modifications

specified in McDonnell Douglas DC-10 Service Bulletin 55-24,

Revision 1, dated August 3, 1994; and McDonnell Douglas DC-10

Service Bulletin 55-25, Revision 1, dated August 3, 1994; in

accordance with the following schedule. Accomplishment of these

preventative modifications constitutes terminating action for the

repetitive inspections required by this AD.

Note 4: Accomplishment of these preventative modifications in

accordance with McDonnell Douglas DC-10 Service Bulletin 55-24,

dated October 25, 1993; or McDonnell Douglas DC-10 Service Bulletin

55-25, dated October 25, 1993; as applicable; is considered

acceptable for compliance with this paragraph.

(1) For Model DC-10-10 and -15 series airplanes:

(i) Prior to the accumulation of 21,000 total landings, or

within 5 years after the effective date of this AD, whichever occurs

later, accomplish the preventative modifications of the forward spar

upper cap on the horizontal stabilizer in accordance with McDonnell

Douglas DC-10 Service Bulletin 55-24, Revision 1, dated August 3,

1994.

(ii) Prior to the accumulation of 19,000 total landings, or

within 5 years after the effective date of this AD, whichever occurs

later, accomplish the modification of the forward upper skin panel

on the horizontal stabilizer in accordance with McDonnell Douglas

DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994.

(2) For Model DC-10-30 and -40 series airplanes:

(i) Prior to the accumulation of 44,250 total landings, or

within 5 years after the effective date of this AD, whichever occurs

later, accomplish the modification of the forward spar upper cap on

the horizontal stabilizer in accordance with McDonnell Douglas DC-10

Service Bulletin 55-24, Revision 1, dated August 3, 1994.

(ii) Prior to the accumulation of 26,500 total landings, or

within 5 years after the effective date of this AD, whichever occurs

later, accomplish the modification of the forward upper skin panel

on the horizontal stabilizer in accordance with McDonnell Douglas

DC-10 Service Bulletin 55-25, Revision 1, dated August 3, 1994.

(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 5: 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

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.

(g) The inspections and modifications shall be done in

accordance with McDonnell Douglas DC-10 Service Bulletin 55-24,

Revision 1, dated August 3, 1994; and McDonnell Douglas DC-10

Service Bulletin 55-25, Revision 1, dated August 3, 1994. This

incorporation by reference was approved by the Director of the

Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part

51. Copies 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. Copies may be inspected 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; or at the Office of the Federal Register, 800 North

Capitol Street, NW., suite 700, Washington, DC.

(h) This amendment becomes effective on October 31, 1994.

Issued in Renton, Washington, on September 26, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-24199 Filed 10-3-94; 8:45 am]

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