# AGENCY: 

Federal Aviation Administration, DOT. 

# ACTION: 

Final rule. 

# SUMMARY: 

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model MD-90 series airplanes, that requires a one-time detailed visual inspection to detect fatigue cracking of certain longerons and the attaching frames of the lower left nose; and repair, if necessary. This amendment also requires installation of a preventive modification. This amendment is prompted by several reports of fatigue cracking of certain longerons and the attaching frames. The actions specified by this AD are intended to prevent such fatigue cracking, which could result in reduced structural integrity of the fuselage, and consequent loss of pressurization of the airplane. 

# DATES: 

Effective February 23, 2000. 

                        The incorporation by reference of certain publications listed in the regulations is approved by the Director of the                         **Federal Register**                         as of February 23, 2000.                     

# ADDRESSES: 

                        The service information referenced in this AD 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 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, 3960 Paramount Boulevard, Lakewood, California; or at the Office of the                         **Federal Register**                        , 800 North Capitol Street, NW., suite 700, Washington, DC.                     

# FOR FURTHER INFORMATION CONTACT: 

Carl Fountain, Aerospace Engineer, Airframe Branch, ANM-120L; FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712; telephone (562) 627-5222; fax (562) 627-5210. 

# 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 MD-90 series airplanes was published in the                     **Federal Register**                     on October 27, 1999 (64 FR 57789). That action proposed to require a one-time detailed visual inspection to detect fatigue cracking of certain longerons and the attaching frames of the lower left nose; and repair, if necessary. That action also proposed to require installation of a preventive modification.                 

## Comments 

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to single the comments received. 

The commenter states that it has no objection to the proposed rule. 

## Conclusion 

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed. 

## Cost Impact 

There are approximately 7 airplanes of the affected design in the worldwide fleet. The FAA estimates that 6 airplanes of U.S. registry will be affected by this AD. 

It will take approximately 1 work hour per airplane to accomplish the required inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $360, or $60 per airplane. 

It will take approximately 6 work hours per airplane to accomplish the required modification, at an average labor rate of $60 per work hour. Parts will cost approximately $312 per airplane. Based on these figures, the cost impact of the modification required by this AD on U.S. operators is estimated to be $4,032, or $672 per airplane. 

The cost impact figures discussed above are 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. 

## Regulatory Impact 

The regulations adopted herein will 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 final rule does not have federalism implications under Executive Order 13132. 

                    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 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 adding the following new airworthiness directive: 

**2000-01-17 McDonnell Douglas:**                            Amendment 39-11515. Docket 99-NM-209-AD.                        

*Applicability:*                            Model MD-90 series airplanes, as listed in McDonnell Douglas Service Bulletin MD90-53-004, dated August 20, 1998, 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 (b) 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 prevent fatigue cracking of longerons 22 through 26 and the attaching frames, which could result in reduced structural integrity of the fuselage, and consequent loss of pressurization of the airplane, accomplish the following: 

## Inspection and Modification 

(a) Prior to the accumulation of 40,000 total landings, or within 24 months after the effective date of this AD, whichever occurs later: Perform a detailed visual inspection to detect cracking of longerons 22 through 26 (inclusive) and the respective attaching frames at station frames Y=160.000 and Y=200.000 of the left lower nose, in accordance with McDonnell Douglas Service Bulletin MD90-53-004, dated August 20, 1998. 

# **Note 2:**

For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

(1) If no cracking is detected: Prior to further flight, install clips and doublers under the longeron flanges and shim the longerons in accordance with the service bulletin. 

(2) If any cracking is detected: Prior to further flight, repair the cracks and install clips and doublers under the longeron flanges and shim the longerons in accordance with the service bulletin.

## Alternative Methods of Compliance 

(b) 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 3:**

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

## Special Flight Permits 

(c) 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. 

## Incorporation by Reference 

(d) The actions shall be done in accordance with McDonnell Douglas Service 

                            Bulletin MD90-53-004, dated August 20, 1998. 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 Boeing Commercial Aircraft Group, Long Beach Division, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Technical Publications Business Administration, Dept. C1-L51 (2-60). 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, 3960 Paramount Boulevard, Lakewood, California; or at the Office of the                             **Federal Register**                            , 800 North Capitol Street, NW., suite 700, Washington, DC.                         

(e) This amendment becomes effective on February 23, 2000. 

Issued in Renton, Washington, on January 10, 2000. 

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 00-950 Filed 1-18-00; 8:45 am]

BILLING CODE 4910-13-U