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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-255-AD] 
          - RIN 2120-AA64 

# 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 series airplanes and C-9 (military) airplanes, that currently requires repetitive ultrasonic or magnetic particle inspections to detect cracking of the engine pylon aft upper spar straps (caps); and if necessary, replacement of the strap with a new strap, or modification of the engine pylon rear spar straps, which constitutes terminating action for the repetitive inspections. This action would require new, improved repetitive ultrasonic inspections, and corrective actions, if necessary. This action also would require, among other items, a terminating action for the repetitive inspection requirements. This proposal is prompted by additional reports of fatigue cracking in the subject area on these airplanes. The actions specified by the proposed AD are intended to detect and correct such fatigue cracking, which could result in major damage to the adjacent structure of the pylon aft spar upper cap, and consequent reduced structural integrity of the airplane. 

# DATES:

Comments must be received by June 26, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-255-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 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 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                           ( print page 30026)                        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 99-NM-255-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. 99-NM-255-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

In 1978, the FAA issued AD 78-01-16, amendment 39-3117, applicable to certain McDonnell Douglas Model DC-9 series airplanes and C-9 (military) airplanes. That AD requires repetitive ultrasonic or magnetic particle inspections to detect cracking of the engine pylon aft upper spar straps (caps); and if necessary, replacement of the strap with a new strap, or modification of the engine pylon rear spar straps (caps), which constitutes terminating action for the repetitive inspections. That action was prompted by reports of fatigue cracking of the pylon aft upper spar straps (caps). The requirements of that AD are intended to detect cracks and prevent failure of the engine pylon aft upper spar straps (caps). 

## Actions Since Issuance of Previous Rule 

Since the issuance of AD 78-01-16, the FAA has received additional reports of fatigue cracking in the subject area on these airplanes. The airplanes on which the cracking occurred had accumulated between 19,000 and 36,000 landings. Investigation revealed that the repetitive ultrasonic inspections, as required by AD 78-01-16, do not adequately detect fatigue cracking in the subject area. Such fatigue cracking, if not detected and corrected, could result in major damage to the adjacent structure of the pylon aft spar upper cap, and consequent reduced structural integrity of the airplane. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved McDonnell Douglas Alert Service Bulletin DC9-54A031, Revision 08, dated January 31, 2000, which describes procedures for new repetitive ultrasonic or magnetic particle inspections of the engine pylon aft upper spar straps (caps) to detect cracking; and corrective actions, if necessary. The corrective actions include reapplication of a sealant; modification of the rear spar upper strap (cap); and replacement of the bearing on the spar strap (cap) with a new annular groove bearing; as applicable. The service bulletin references McDonnell Douglas DC-9 Service Bulletin 54-31, Revision 4, dated March 28, 1991, as an additional source of service information for accomplishment of the modification. 

The FAA also has reviewed and approved McDonnell Douglas DC-9 Service Bulletin 54-31, Revision 4, dated March 28, 1991. The service bulletin describes procedures for modification of the rear spar upper strap (cap), which would eliminate the need for the repetitive inspections specified in McDonnell Douglas Alert Service Bulletin DC9-54A031, Revision 08, dated January 31, 2000. The modification includes installation of access doors on the pylon rear spars, if applicable; replacement of the strap on the pylon upper rear spar cap with a new strap using new close tolerance attaching parts; and modification of the pylon-to-vibration isolator link. 

Accomplishment of the actions specified in the service bulletins 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 78-01-16 to continue to require repetitive ultrasonic or magnetic particle inspections to detect cracking of the engine pylon aft upper spar straps (caps); and if necessary, replacement of the strap with a new strap, or modification of the engine pylon rear spar straps (caps), which constitutes terminating action for the repetitive inspections. The proposed AD also would require accomplishment of the actions specified in the service bulletins described previously. 

## 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 ultrasonic inspection that is currently required by AD 78-01-16, and retained in this proposed AD, takes approximately 3 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 $180 per airplane, per inspection cycle. 

The new ultrasonic inspection that is proposed in this AD action would take approximately 4 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 new ultrasonic inspection proposed by this AD on U.S. operators is estimated to be $240 per airplane, per inspection cycle. 

The new modification of the rear spar upper strap (cap) that is proposed in this AD action would take between approximately 349 and 412 work hours depending on the configuration of the affected airplane to accomplish, at an average labor rate of $60 per work hour. The cost of required parts would be between approximately $1,865 and $7,947 per airplane. Based on these figures, the cost impact of the new modification proposed by this AD on U.S. operators is estimated to be between $22,805 and $32,667 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. 

Should an operator elect to accomplish the optional magnetic particle inspection that would be provided by this AD action, it would take approximately 7 work hours to accomplish it, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this action would be $420 per airplane, per inspection cycle. 

## 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                           ( print page 30027)                        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. 

§ 39.13 

2. Section 39.13 is amended by removing amendment 39-3117, and by adding a new airworthiness directive (AD), to read as follows:

**McDonnell Douglas:**                                 Docket 99-NM-255-AD. Supersedes AD 78-01-16, Amendment 39-3117.                            

*Applicability:*                                 Model DC-9-10, -20, -30, -40, and -50 series airplanes, and C-9 (military) airplanes, fuselage numbers 1 through 851, inclusive; certificated in any category.                             

# Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (p) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

*Compliance:*                                 Required as indicated, unless accomplished previously.                             

To detect and correct fatigue cracking of the pylon aft upper spar straps (caps), which could result in major damage to the adjacent structure of the pylon aft spar upper cap, and consequent reduced structural integrity of the airplane, accomplish the following: 

## Restatement of Requirements of AD 78-01-16, Amendment 39-3117 

### Compliance Times 

(a) For airplanes that have accumulated 35,000 or more total landings as of February 13, 1978 (the effective date of AD 78-01-16, amendment 39-3117): Within 600 landings after February 13, 1978, unless already accomplished within the last 1,800 landings, and thereafter at intervals not to exceed 2,400 landings, accomplish the actions specified in paragraph (f) of this AD. 

(b) For airplanes that have accumulated between 30,000 and 34,999 total landings inclusive, as of February 13, 1978: Within 900 landings after February 13, 1978, unless already accomplished within the last 1,500 landings, and thereafter at intervals not to exceed 2,400 landings, accomplish the actions specified in paragraph (f) of this AD. 

(c) For airplanes that have accumulated between 25,000 and 29,999 total landings inclusive, as of February 13, 1978: Within 1,200 landings after February 13, 1978, unless already accomplished within the last 1,200 landings, and thereafter at intervals not to exceed 2,400 landings, accomplish the actions specified in paragraph (f) of this AD. 

(d) For airplanes that have accumulated between 15,000 and 24,999 total landings inclusive, as of February 13, 1978: Within 2,000 landings after February 13, 1978, unless already accomplished within the last 400 landings, and thereafter at intervals not to exceed 2,400 landings, accomplish the actions specified in paragraph (f) of this AD. 

(e) For airplanes that have accumulated less than 15,000 total landings as of February 13, 1978: Within 2,000 landings after the accumulation of 15,000 total landings, and thereafter at intervals not to exceed 2,400 landings, accomplish the actions specified in paragraph (f) of this AD. 

### Repetitive Inspections and Corrective Actions 

(f) At the times specified in paragraphs (a) through (e), except as provided by paragraph (g) of this AD, perform an ultrasonic inspection of the engine pylon aft upper spar straps (caps), part number (P/N) 9958154-5/-6, or P/N 9958154-37/-38, to detect cracking, in accordance with paragraph 2.B of McDonnell Douglas DC-9 Service Bulletin A54-31, dated December 22, 1976, or in accordance with a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. 

# Note 2:

Alternative methods of compliance approved previously prior to the effective date of this AD in accordance with the Chief, Aircraft Engineering Division, Western Region, are considered acceptable for compliance with paragraph (f) of this AD.

(1) If there is evidence of cracking, the magnetic particle inspection specified in paragraph 2.C of the service bulletin may be used to confirm the evidence of cracking. 

(2) If any cracking is detected, prior to further flight, accomplish either paragraph (f)(2)(i) or (f)(2)(ii) of this AD in accordance with the service bulletin. 

(i) Replace the strap with a new strap, P/N 9958154-5/-6, or P/N 9958154-37/-38, and repeat the inspection thereafter at intervals not to exceed 15,000 landings. Or 

(ii) Modify the engine pylon rear spar straps (caps) in accordance with the service bulletin. Accomplishment of the modification constitutes terminating action for the repetitive inspection requirements of this AD. 

# Note 3:

Modification of the engine pylon rear spar straps (caps) accomplished prior to the effective date of this AD in accordance with McDonnell Douglas DC-9 Alert Service Bulletin A54-31, Revision 2, dated December 22, 1977; Revision 3, dated June 20, 1986; Revision 4, dated March 26, 1987; Revision 5, dated March 25, 1991; or Revision 6, dated November 23, 1992; is considered acceptable for compliance with the requirements of paragraph (f)(2)(ii) of this AD.

### Optional Magnetic Particle Inspection 

(g) In lieu of accomplishing the ultrasonic inspection, at the times specified in paragraphs (a) through (e) of this AD, perform a magnetic particle inspection of the engine pylon aft upper spar straps (caps), P/N 9958154-5/-6, or P/N 9958154-37/-38, to detect cracking, in accordance with paragraph 2.C of McDonnell Douglas DC-9 Service Bulletin A54-31, dated December 22, 1976. If any cracking is detected, prior to further flight, accomplish the action specified in paragraph (f) of this AD. After two bearing replacements, accomplish the action specified in either paragraph (f)(2)(i) or (f)(2)(ii) of this AD. 

# Note 4:

Ultrasonic or magnetic particle inspection of the engine pylon aft upper spar straps (caps) accomplished prior to the effective date of this AD in accordance with McDonnell Douglas DC-9 Alert Service Bulletin A54-31, Revision 2, dated December 22, 1977; Revision 3, dated June 20, 1986; Revision 4, dated March 26, 1987; Revision 5, dated March 25, 1991; or Revision 6, dated November 23, 1992; is considered acceptable for compliance with the inspection requirements of paragraph (f) or (g) of this AD, as applicable.

## New Requirements of This AD 

### Repetitive Ultrasonic Inspections 

                                (h) For airplanes on which the modification/replacement specified in paragraph (f)(2)(ii) or (n) of this AD has not been accomplished, and on which the replacement specified in paragraph (f)(2)(i) of this AD has not been accomplished: Except as provided by paragraph (m) of this AD, perform an ultrasonic inspection of the engine pylon aft upper spar straps (caps) to detect cracking, in accordance with McDonnell Douglas Alert Service Bulletin DC9-54A031, Revision 08, dated January 31, 2000; at the time specified in paragraph                                       ( print page 30028)                                    (h)(1), (h)(2), (h)(3), or (h)(4) of this AD, as applicable. Repeat this inspection thereafter at intervals not to exceed 2,400 landings.                             

Accomplishment of the ultrasonic inspection constitutes terminating action for the repetitive inspection requirements of paragraphs (a) through (f), (f)(2)(i), and (g) of this AD. 

(1) For airplanes that have accumulated between 15,000 and 24,999 total landings as of the effective date of this AD: Within 2,000 landings or 6 months after the effective date of this AD, whichever occurs later. 

(2) For airplanes that have accumulated between 25,000 and 29,999 total landings as of the effective date of this AD: Within 1,200 landings or 6 months after the effective date of this AD, whichever occurs later. 

(3) For airplanes that have accumulated between 30,000 and 34,999 total landings as of the effective date of this AD: Within 900 landings or 6 months after the effective date of this AD, whichever occurs later. 

(4) For airplanes that have accumulated 35,000 or more total landings as of the effective date of this AD: Within 600 landings or 6 months after the effective date of this AD, whichever occurs later. 

(i) For airplanes on which the modification/replacement specified in paragraph (f)(2)(ii) or (n) of this AD has not been accomplished, and on which the replacement specified in paragraph (f)(2)(i) of this AD has been accomplished: Except as provided by paragraph (m) of this AD, perform an ultrasonic inspection of the engine pylon aft upper spar straps (caps) to detect cracking, in accordance with McDonnell Douglas Alert Service Bulletin DC9-54A031, Revision 08, dated January 31, 2000; at the time specified in paragraph (i)(1), (i)(2), (i)(3), or (i)(4) of this AD, as applicable. Repeat this inspection thereafter at intervals not to exceed 2,400 landings. 

(1) For airplanes that have accumulated between 15,000 and 24,999 landings since installation of the new spar strap (cap): Within 2,000 landings or 6 months after the effective date of this AD, whichever occurs later. 

(2) For airplanes that have accumulated between 25,000 and 29,999 landings since installation of the new spar strap (cap): Within 1,200 landings or 6 months after the effective date of this AD, whichever occurs later. 

(3) For airplanes that have accumulated between 30,000 and 34,999 landings since installation of the new spar strap (cap): Within 900 landings or 6 months after the effective date of this AD, whichever occurs later. 

(4) For airplanes that have accumulated 35,000 or more landings since installation of the new spar strap (cap): Within 600 landings or 6 months after the effective date of this AD, whichever occurs later. 

(j) If no cracking is detected during any inspection required by paragraph (h), (i), or (m) of this AD, prior to further flight, reapply sealant in accordance with McDonnell Douglas Alert Service Bulletin DC9-54A031, Revision 08, dated January 31, 2000. 

(k) If any cracking is detected during any inspection required by paragraph (h) or (i) of this AD, prior to further flight, accomplish the actions specified in paragraph (m) of this AD. 

(l) If any cracking is detected during any inspection required by paragraph (h), (i), or (m) of this AD, prior to further flight, modify the rear spar upper strap (cap) in accordance with McDonnell Douglas DC-9 Service Bulletin 54-31, Revision 4, dated March 28, 1991. Accomplishment of the modification constitutes terminating action for the repetitive inspection requirements of paragraphs (h) and (i) of this AD. 

(m) In lieu of accomplishing the ultrasonic inspection required by paragraphs (h) and (i) of this AD, at the applicable times specified in paragraphs (h), (h)(1), (h)(2), (h)(3), (h)(4), (i), (i)(1), (i)(2), (i)(3), or (i)(4) of this AD, perform a magnetic particle inspection of the engine pylon aft upper spar strap (cap) for cracks, in accordance with McDonnell Douglas Alert Service Bulletin DC9-54A031, Revision 08, dated January 31, 2000. If no cracking is detected, prior to further flight, replace the bearing on the spar strap (cap) with a new annular groove bearing, in accordance with the service bulletin. 

### Terminating Modification 

(n) Prior to the accumulation of 100,000 total landings, or within 6 months after the effective date of this AD, whichever occurs later, modify the rear spar upper strap (cap) in accordance with McDonnell Douglas DC-9 Service Bulletin 54-31, Revision 4, dated March 28, 1991. Accomplishment of the modification constitutes terminating action for the repetitive inspection requirements of paragraphs (h) and (i) of this AD. 

(o) Accomplishment of the modification required by paragraph (l) or (n) of this AD constitutes compliance with the following: 

(1) The actions specified in McDonnell Douglas Service Bulletin 54-27, Revision 4, dated April 2, 1990, that are required by AD 96-10-11, amendment 39-9618 (61 FR 24675, May 16, 1996) [which references “DC-9/MD80 Aging Aircraft Service Action Requirements Document” (SARD), McDonnell Douglas Report MDC K1572, Revision B, dated January 15, 1993, as the appropriate source of service information for accomplishment of the modification]; and

(2) The requirements of AD 72-09-01, amendment 39-2844 (which references McDonnell Douglas Service Bulletin 54-31, dated August 24, 1976, and McDonnell Douglas Service Bulletin 54-27, Revision 4, dated April 2, 1990, as appropriate sources of service information for accomplishment of the modification). 

### Alternative Methods of Compliance 

(p) 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 5:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO.

# Note 6:

Alternative methods of compliance, approved previously in accordance with AD 78-01-16, amendment 39-3117, are approved as alternative methods of compliance with this AD.

### Special Flight Permits 

(q) 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 May 3, 2000. 

Vi L. Lipski, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-11722 Filed 5-9-00; 8:45 am] 

BILLING CODE 4910-13-U