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

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-90-AD; Amendment 39-8933; AD 94-12-05]

Airworthiness Directives; McDonnell Douglas Model DC-10 Series

Airplanes and Model KC-10A (Military) Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

applicable to all McDonnell Douglas Model DC-10 series airplanes and

Model KC-10A (military) airplanes, that requires inspections to detect

cracks in wing stringer number 41; installation of a repair, if

necessary; and modification of that stringer. This amendment is

prompted by reports of fatigue cracks in outer wing stringer number 41.

The actions specified by this AD are intended to prevent reduced

structural integrity of the wing.

DATES: Effective July 13, 1994.

The incorporation by reference of certain publications listed in

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

of July 13, 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: Maureen Moreland, Aerospace Engineer,

Airframe Branch, ANM-120L, FAA, Transport Airplane Directorate, Los

Angeles Aircraft Certification Office, 3229 East Spring Street, Long

Beach, California 90806-2425; telephone (310) 988-5238; fax (310) 988-

5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to all McDonnell Douglas Model DC-10 series airplanes and

Model KC-10A (military) airplanes was published in the Federal Register

on September 24, 1993 (58 FR 49946). That action proposed to require

inspections to detect cracks in wing stringer number 41; installation

of a repair, if necessary; and modification of that stringer.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the proposed rule.

The Air Transport Association (ATA) of America, on behalf of one of

its members, requests that the FAA include a flow diagram in the

proposal since its provisions are complex. The FAA does not concur. The

FAA considers that the requirements of this AD are presented in a

reasonably clear manner in the text of the final rule. In addition,

McDonnell Douglas DC-10 Service Bulletin 57-114, Revision 1, dated July

26, 1993, which is referenced in the AD as the appropriate source of

service information, provides corresponding guidance for accomplishment

of the actions required by this AD.

ATA also suggests that, prior to issuance of the final rule, the

FAA should verify that the service bulletin will not create problems

for operators, and that accomplishment of the service bulletin should

be verified by an operator before the AD is finalized. One ATA member

experienced difficulty accomplishing the permanent repair specified in

the service bulletin because parts listed did not fit, drawings were

erroneous, and fastener grip lengths were inadequate for the repair.

The FAA concurs with the commenter's request. The FAA has conveyed

these concerns to the manufacturer, and has verified that the initial

problems expressed by the commenter have been corrected in Revision 1

of the service bulletin. Since Revision 1 of the service bulletin was

cited in the proposal as the appropriate source of service information,

the FAA finds that no change to the AD is necessary.

One commenter requests that the FAA allow visual inspection methods

to be used in lieu of the proposed eddy current inspection methods. The

commenter indicates that fastener accessibility enables accomplishment

of a visual inspection and provides an equivalent level of crack

detection. The FAA does not concur. Based on the results of crack

growth analysis, the FAA has determined that a visual inspection of the

stringer cannot provide an acceptable level of crack detection. In

addition, the FAA based the repetitive inspection intervals on the

crack growth analysis results based upon the minimum crack length

detectable by eddy current inspection.

The commenter also requests that credit be given for general visual

inspections accomplished previously. A second commenter supports the

proposed rule, but requests that the AD be revised to state that

inspections accomplished within 1,500 landings prior to the effective

date of the AD are acceptable in lieu of the initial inspection. The

commenters provide no justification for these requests. Since the FAA

has determined that a visual inspection of the stringer does not

provide an acceptable level of crack detection, as discussed

previously, the FAA considers that the requirement for eddy current

inspections is appropriate and credit cannot be extended for general

visual inspections accomplished previously. However, the phrase

``unless accomplished previously,'' which appears in the ``Compliance''

paragraph of the final rule, provides credit for operators that have

accomplished the required inspection prior to the effective date of

this AD in accordance with McDonnell Douglas DC-10 Service Bulletin 57-

114, Revision 1, dated July 26, 1993.

One commenter requests that the first inspection accomplished to

comply with this AD be required during the airplane's next heavy

maintenance visit if a general visual inspection has been accomplished

prior to the effective date of the AD. The FAA does not concur. A

general visual inspection of the stringer does not provide an

acceptable level of crack detection, as discussed previously. In

developing an appropriate initial compliance time for this action, the

FAA considered the safety implications and normal maintenance schedules

for timely accomplishment of the inspection. In consideration of these

items, the FAA has determined that 6,500 total landings or 1,500

landings after the effective date of the AD, whichever occurs later,

represents the maximum interval of time allowable wherein the

inspection can reasonably be accomplished and an acceptable level of

safety can be maintained.

The same commenter states that the service bulletin cited in the AD

specifies that one reason for accomplishing the actions described in

the service bulletin is to prevent unscheduled maintenance downtime for

replacement of a cracked stringer; therefore, the commenter questions

the need for this AD. The commenter adds that, to date, stringer 41

cracking has not impacted its maintenance due to the viable maintenance

program currently in place. The commenter states that imposing an AD at

this time would only complicate its maintenance program and would

contribute little toward ensuring that the airplane wing structure is

operating in good condition.

The FAA does not concur. As explained in the preamble of the

proposal, the FAA has received reports of fatigue cracks in outer wing

stringer number 41 and, in one case, complete failure of the stringer.

Such fatigue cracking presents an unsafe condition in airplanes, since

it could eventually lead to failure of the stringer and reduced

structural integrity of the wing. The FAA has determined that this

unsafe condition could exist or eventually develop on Model DC-10

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

repetitive inspections of the affected area must be mandated to ensure

that safety is not degraded. The appropriate vehicle for mandating such

action to correct an unsafe condition is the airworthiness directive.

One commenter requests that the proposed compliance time for

accomplishment of the initial inspection specified in paragraph (b)(1)

of the proposal be changed from ``[p]rior to the accumulation of 6,500

total landings, or within 1,500 landings after the effective date of

the AD, whichever occurs later,'' to ``[p]rior to the accumulation of

6,500 total landings, or within one year after the effective date of

this AD, whichever occurs later.'' The commenter operates Model DC-10-

40 series airplanes of non-U.S. registry for training flights for

cockpit crews. The commenter explains that, during one training flight

period of a few weeks, the number of flight cycles accumulated may be

more than 1,500 landings. The commenter adds that the proposed

inspections and modifications require entry into the fuel tanks;

therefore, the commenter plans to accomplish the initial inspections

and the modifications during regularly scheduled maintenance.

The FAA does not concur with the commenter's request. Compliance

times for AD's are normally based on a parameter related to failure of

a particular component. In this case, fatigue cracking in outer wing

stringer number 41 and subsequent failure of the stringer are

undoubtedly related to the number of landings. The FAA has determined,

in this case, that there is no apparent direct relationship between

failure of the stringer and calendar time. In light of this, and in

consideration of the average utilization rate of the affected U.S.

operators and the practical aspects of orderly inspections of the U.S.

fleet during regular maintenance periods, the FAA established the

compliance times specified in this AD. The FAA maintains that those

compliance times are appropriate. However, the FAA would consider a

request for adjustment of the compliance time, in accordance with the

provisions of paragraph (c) of this AD, provided that, for example,

continued operational safety of the airplane could be assured until the

required action is accomplished.

One commenter requests that, in order for the AD requirements to

align with the actions described in the service bulletin,

accomplishment of the preventative modification should be considered

optional, and that operators should be permitted to accomplish

repetitive inspections at intervals of 4,000 landings in lieu of the

preventative modification. The FAA does not concur. The degree of

assurance necessary as to the adequacy of inspections needed to

maintain the safety of the aging transport airplane fleet, coupled with

a better understanding of the human factors associated with numerous

repetitive inspections, has caused the FAA to place less emphasis on

repetitive inspections and more emphasis on design improvements and

material replacement. Thus, in lieu of its previous position of

continual inspection, and repair or modification on condition if cracks

are found, the FAA has decided to require, whenever practicable,

airplane modifications necessary to remove the source of the particular

aging phenomena.

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the changes previously

described. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

There are approximately 426 Model DC-10 series airplanes and Model

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

fleet. The FAA estimates that 121 Model DC-10-10 and -15 series

airplanes of U.S. registry will be affected by this AD, that it will

take approximately 13.6 work hours per airplane to accomplish the

required actions, and that the average labor rate is $55 per work hour.

Required parts for Model DC-10-10 and -15 series airplanes will cost

approximately $586 per airplane. Based on these figures, the total cost

impact of the AD on U.S. operators of Model DC-10-10 and -15 series

airplanes is estimated to be $161,414, or $1,334 per airplane.

The FAA estimates that 148 Model DC-10-30 and -40 series airplanes

and Model KC-10A (military) airplanes of U.S. registry will be affected

by this AD, that it will take approximately 13.6 work hours per

airplane to accomplish the required actions, and that the average labor

rate is $55 per work hour. Required parts for Model DC-10-30 and -40

series airplanes and Model KC-10A (military) airplanes will cost

approximately $1,420 per airplane. Based on these figures, the total

cost impact of the AD on U.S. operators of Model DC-10-30 and -40

series airplanes and Model KC-10A (military) airplanes is estimated to

be $320,864, or $2,168 per airplane.

Based on these figures, the total cost impact of the AD on U.S.

operators is estimated to be $482,278. The total cost impact figure is

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. -

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. -

For the reasons discussed above, I certify that this action: (1) Is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it 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 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:

94-12-05 McDonnell Douglas: Amendment 39-8933. Docket 93-NM-90-AD.

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

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

certificated in any category. -

Compliance: Required as indicated, unless accomplished

previously. -

To prevent reduced structural integrity of the wing, accomplish

the following: -

(a) For Model DC-10-10, -10F, and -15 series airplanes:

Accomplish paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this AD

in accordance with McDonnell Douglas DC-10 Service Bulletin 57-114,

Revision 1, dated July 26, 1993. -

(1) Prior to the accumulation of 6,500 total landings, or within

1,500 landings after the effective date of this AD, whichever occurs

later: Perform an eddy current surface inspection or an eddy current

bolt hole inspection to detect cracks on stringer number 41 on the

left- and right-hand wings, in accordance with the service bulletin.

-

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

intervals not to exceed 4,000 landings. -

(3) If any crack is found, prior to further flight, accomplish

paragraph (a)(3)(i), (a)(3)(ii), or (a)(3)(iii) of this AD, as

applicable. -

(i) If any crack is found that extends upward from the fastener

hole, and if that crack is outside the limits specified in Condition

2 of the service bulletin, accomplish a temporary repair in

accordance with Condition 2, Phase I of the service bulletin, or a

permanent repair in accordance with Condition 2, Phase II of the

service bulletin. If the temporary repair is accomplished, prior to

the accumulation of 5,000 landings after accomplishing that

temporary repair, accomplish the permanent repair in accordance with

Condition 2, Phase II of the service bulletin. After accomplishment

of the permanent repair, no further action is required by this AD. -

(ii) If any crack is found that extends downward from the

fastener hole, and if that crack is outside the limits specified in

Condition 2 of the service bulletin, accomplish the permanent repair

in accordance with Condition 2, Phase II of the service bulletin.

After such repair, no further action is required by this AD. -

(iii) If any crack is found in a fastener hole, and if that

crack is within the limits specified in Condition 2 of the service

bulletin, accomplish the preventative modification in accordance

with Condition 1, Option II of the service bulletin. If the crack

was detected using techniques other than the eddy current bolt hole

inspection described in the service bulletin, prior to accomplishing

the preventative modification, perform an eddy current bolt hole

inspection to detect cracks, in accordance with the service

bulletin, and accomplish paragraph (a)(3)(iii)(A), (a)(3)(iii)(B),

or (a)(3)(iii)(C) of this AD, as applicable. -

(A) If any crack is found that extends upward from the fastener

hole, and if that crack is outside the limits specified in Condition

2 of the service bulletin, accomplish the requirements of paragraph

(a)(3)(i) of this AD. -

(B) If any crack is found that extends downward from the

fastener hole, and if that crack is outside the limits specified in

Condition 2 of the service bulletin, accomplish the requirements of

paragraph (a)(3)(ii) of this AD.

(C) If any crack is found that is within the limits specified in

Condition 2 of the service bulletin, accomplish the preventative

modification in accordance with Condition 1, Option II of the

service bulletin. After accomplishment of the preventative

modification, no further action is required by this AD.

(4) Except for airplanes on which the preventative modification

(Condition 1, Option II) or the permanent repair (Condition 2, Phase

II) has been accomplished, prior to the accumulation of 6,500 total

landings, or within 5 years after the effective date of this AD,

whichever occurs later: Perform an eddy current bolt hole inspection

to detect cracks in the fastener holes in accordance with the

service bulletin.

(i) If no crack is found, or if any crack is found that is

within the limits specified in Condition 2 of the service bulletin,

prior to further flight, accomplish the preventative modification in

accordance with Condition 1, Option II of the service bulletin.

After accomplishment of the preventative modification, no further

action is required by this AD.

(ii) If any crack is found that exceeds the limits specified in

Condition 2 of the service bulletin, prior to further flight,

accomplish a permanent repair in accordance with Condition 2, Phase

II of the service bulletin. After accomplishment of the permanent

repair, no further action is required by this AD.

(b) For Model DC-10-30, -30F, -40, and -40F series airplanes and

Model KC-10A (military) airplanes: Accomplish paragraphs (b)(1),

(b)(2), (b)(3), and (b)(4) of this AD in accordance with McDonnell

Douglas DC-10 Service Bulletin 57-114, Revision 1, dated July 26,

1993. -

(1) Prior to the accumulation of 6,500 total landings, or within

1,500 landings after the effective date of this AD, whichever occurs

later: Perform an eddy current surface inspection or an eddy current

bolt hole inspection to detect cracks on stringer number 41 on the

left- and right-hand wings in accordance with the service bulletin.

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

intervals not to exceed 3,200 landings.

(3) If any crack is found, prior to further flight, accomplish

paragraph (b)(3)(i), (b)(3)(ii), or (b)(3)(iii) of this AD, as

applicable.

(i) If any crack is found that extends upward from the fastener

hole, and if that crack is outside the limits specified in Condition

2 of the service bulletin, accomplish a temporary repair in

accordance with Condition 2, Phase I of the service bulletin, or a

permanent repair in accordance with Condition 2, Phase II of the

service bulletin. If the temporary repair is accomplished, prior to

the accumulation of 5,000 landings after accomplishing that

temporary repair, accomplish the permanent repair in accordance with

Condition 2, Phase II of the service bulletin. After accomplishment

of the permanent repair, no further action is required by this AD.

(ii) If any crack is found that extends downward from the

fastener hole, and if that crack is outside the limits specified in

Condition 2 of the service bulletin, accomplish the permanent repair

in accordance with Condition 2, Phase II of the service bulletin.

After such repair, no further action is required by this AD.

(iii) If any crack is found in a fastener hole, and if that

crack is within the limits specified in Condition 2 of the service

bulletin, accomplish the preventative modification in accordance

with Condition 1, Option II of the service bulletin. If the crack

was detected using techniques other than the eddy current bolt hole

inspection described in the service bulletin, prior to accomplishing

the preventative modification, perform an eddy current bolt hole

inspection to detect cracks, in accordance with the service

bulletin, and accomplish paragraph (b)(3)(iii)(A), (b)(3)(iii)(B),

or (b)(3)(iii)(C) of this AD, as applicable.

(A) If any crack is found that extends upward from the fastener

hole, and if that crack is outside the limits specified in Condition

2 of the service bulletin, accomplish the requirements of paragraph

(b)(3)(i) of this AD.

(B) If any crack is found that extends downward from the

fastener hole, and if that crack is outside the limits specified in

Condition 2 of the service bulletin, accomplish the requirements of

paragraph (b)(3)(ii) of this AD.

(C) If any crack is found that is within the limits specified in

Condition 2 of the service bulletin, accomplish the preventative

modification in accordance with Condition 1, Option II of the

service bulletin. After accomplishment of the preventative

modification, no further action is required by this AD.

(4) Except for airplanes on which the preventative modification

(Condition 1, Option II) or the permanent repair (Condition 2, Phase

II) has been accomplished, prior to the accumulation of 6,500 total

landings, or within 5 years after the effective date of this AD,

whichever occurs later: Perform an eddy current bolt hole inspection

to detect cracks in the fastener holes in accordance with the

service bulletin.

(i) If no crack is found, or if any crack is found that is

within the limits specified in Condition 2 of the service bulletin,

prior to further flight, accomplish the preventative modification in

accordance with Condition 1, Option II of the service bulletin.

After accomplishment of the preventative modification, no further

action is required by this AD.

(ii) If any crack is found that exceeds the limits specified in

Condition 2 of the service bulletin, prior to further flight,

accomplish a permanent repair in accordance with Condition 2, Phase

II of the service bulletin. After accomplishment of the permanent

repair, no further action is required by 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

Federal Aviation Regulations (FAR) Sec. 21.197 and Sec. 21.199 to

operate the airplane to a location where the requirements of this AD

can be accomplished.

(e) The inspections, repairs, and modification shall be done in

accordance with McDonnell Douglas DC-10 Service Bulletin 57-114,

Revision 1, dated July 26, 1993. 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.

(f) This amendment becomes effective on July 13, 1994.

Issued in Renton, Washington, on May 31, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-13627 Filed 6-10-94; 8:45 am]

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