Airworthiness Directives; McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 Series Airplanes and C-9 (Military) Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 series airplanes, that currently requires repetitive radiographic and ultrasonic or eddy current inspections, and modification of the upper cap of the front spar of the left and right engine pylons, if necessary. This action would require new, improved x-ray and eddy current inspections to detect cracks of the upper cap of the front spar of the left and right engine pylons, and repetitive inspections or corrective actions, if necessary. This action also would require modification of the subject area, which would constitute terminating action for the repetitive inspection requirements. This proposal is prompted by additional reports of fatigue cracking in the subject area of these airplanes. The actions specified by the proposed AD are intended to prevent failure of the upper cap of the front spar of the engine pylons due to fatigue cracking, and consequent reduced structural integrity of the airplane.

DATES:

Comments must be received by August 21, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-04-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-04-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Aircraft Group, Long Beach 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 the FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California.

FOR FURTHER INFORMATION CONTACT:

Wahib Mina, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Transport Airplane Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5324; 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.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

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 2000-NM-04-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. 2000-NM-04-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

In 1977, the FAA issued AD 77-44-19, amendment 39-2971, applicable to certain McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 series airplanes, to require repetitive radiographic and ultrasonic or eddy current inspections, and modification of the upper cap of the front spar of the left and right engine pylons, if necessary. The requirements of that AD are intended to detect fatigue cracks and/or failure of the upper cap of the front spar of the left and right engine pylons.

Actions Since Issuance of Previous Rule

Since the issuance of AD 77-14-19, the FAA has received additional reports of fatigue cracking in the subject area of the upper cap of the front spar of the left and right engine pylons. The airplanes on which the cracking occurred had accumulated between 10,162 and 23,850 total flight hours. Investigation revealed that the repetitive ultrasonic and eddy current inspections, as required by AD 77-14-19, do not adequately detect fatigue cracking in the subject area. Such fatigue cracking, if not detected and corrected, could result in failure of the upper cap of the front spar of the left and right engine pylons, and consequent reduced structural integrity of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved McDonnell Douglas Service Bulletin DC9-54-030, Revision 06, dated November 11, 1999. The service bulletin describes procedures for x-ray and eddy current inspections to detect cracks of the upper cap of the front spar of the left and right engine pylons, and repetitive inspections or corrective actions (i.e., the modification described below), if necessary. The service bulletin also describes procedures for an optional modification of the upper cap of the front spar of the left and right engine pylons, which would eliminate the need for the repetitive inspections. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

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 supersede AD 77-14-19 to continue to require radiographic and ultrasonic or eddy current inspections. The proposed AD also would require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.

Differences Between the Proposed AD and Relevant Service Information

Operators should note that this AD proposes to mandate, prior to the accumulation of 100,000 total landings, or within 6 months after the effective date of this AD, whichever occurs later, the modification of the upper cap of the front spar of the left and right engine pylons described in McDonnell Douglas Service Bulletin DC9-54-030, Revision 06, as terminating action for the repetitive inspections. (Incorporation of the terminating action is specified in this service bulletin as 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 proposed modification requirement is consistent with these conditions.

Explanation of Change of Applicability

The applicability of AD 77-14-19 includes affected airplanes having fuselage numbers 1 through 837. However, the applicability of this proposed AD removes several of those fuselage numbers because those airplanes are out of service.

Cost Impact

There are approximately 809 Model DC-9-10, -20, -30, -40, and -50 series airplanes and C-9 (military) airplanes of the affected design in the worldwide fleet. The FAA estimates that 572 airplanes of U.S. registry would be affected by this proposed AD.

The actions that are currently required by AD 77-14-19, and retained in this proposed AD, take approximately 12 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $411,840, or $720 per airplane, per inspection cycle.

The new inspection that is proposed in this AD action would take approximately 12 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this inspection proposed by this AD on U.S. operators is estimated to be $411,840, or $720 per airplane, per inspection cycle.

The new modification that is proposed in this AD action would take approximately 110 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $30,496 per airplane. Based on these figures, the cost impact of the modification proposed by this AD on U.S. operators is estimated to be $21,218,912, or $37,096 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or 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 a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132.

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.