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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 99-NM-313-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 747-100, -200, -300, -400, and 747SR series airplanes. This proposal would require repetitive inspections to detect cracks and corrosion around the lower bearing of the actuator attach fittings of the inboard and outboard flaps. This proposal also would require repetitive overhauls for certain attach fittings or repetitive replacement of the attach fittings with new attach fittings, as applicable, which would constitute terminating action for certain repetitive actions. This proposal is prompted by reports of cracks on the lower bearing journal of the inboard actuator attach fittings of the outboard trailing edge flaps due to stress corrosion. The actions specified by the proposed AD are intended to detect and correct cracking on the actuator attach fittings of the trailing edge flaps, which could result in abnormal operation or retraction of a trailing edge flap, and consequent reduced controllability of the airplane. 

# DATES:

Comments must be received by June 8, 2000. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-313-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 Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. 

# FOR FURTHER INFORMATION CONTACT:

Tamara L. Anderson, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2771; fax (425) 227-1181. 

# 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. 

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-313-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-313-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

                    The FAA has received reports of stress corrosion cracks on the lower                           ( print page 21676)                        bearing journal of the number 2 and 7 inboard attach fittings of the outboard trailing edge flaps on Boeing Model 747-200 and -300 series airplanes. Each flap assembly has two attach fittings, one on each ballscrew which is attached to the flap transmission. Such cracking, if not detected and corrected, could result in abnormal operation or retraction of a trailing edge flap, and consequent reduced controllability of the airplane.                 

The subject actuator attach fittings on the inboard and outboard flaps on Boeing Model 747-100, -400, and 747SR series airplanes are identical to that of the affected Boeing Model 747-200 and -300 series airplanes. Therefore, all of these airplanes may be subject to the same unsafe condition. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved Boeing Service Bulletin 747-57A2310, Revision 1, dated November 23, 1999. This service bulletin describes procedures for repetitive ultrasonic and detailed visual inspections (as applicable) to detect cracks and corrosion around the lower bearing of the actuator attach fittings of the inboard and outboard flaps. This service bulletin also describes procedures for repetitive overhauls for the attach fittings on the outboard flaps or repetitive replacement of the attach fittings with new attach fittings, as applicable, which would eliminate the need for certain repetitive actions. In addition, the service bulletin describes procedures for accomplishing a terminating action for the inboard flap attach fittings. 

## 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 require accomplishment of the actions specified in the service bulletin described previously. 

## Interim Action 

This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking. 

## Cost Impact 

There are approximately 1,008 airplanes of the affected design in the worldwide fleet. The FAA estimates that 206 airplanes of U.S. registry would be affected by this proposed AD. 

It would take approximately 2 work hours per airplane to accomplish the proposed inspection(s), at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection(s) proposed by this AD on U.S. operators is estimated to be $24,720, or $120 per airplane, per inspection cycle. 

Should an operator be required to accomplish the proposed overhaul, it would take approximately 5 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 overhaul proposed by this AD on U.S. operators is estimated to be $61,800, or $300 per airplane, per overhaul cycle. 

Should an operator be required to accomplish the proposed replacement, it would take approximately 2 work hours per airplane to accomplish at an average labor rate of $60 per work hour. Required parts would cost approximately $6,623 (for each of the 4 attach fittings on the outboard flaps) and $7,566 (for each 4 attach fittings on the inboard flaps) per airplane. Based on these figures, the cost impact of the replacement proposed by this AD on U.S. operators is estimated to be $26,972 (outboard flaps) and $30,744 (inboard flaps) 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 proposed herein would 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. 

                    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 adding the following new airworthiness directive:

**Boeing:**                                 Docket 99-NM-313-AD.                            

*Applicability:*                                 All Model 747-100, -200, -300, -400, and 747SR series airplanes; 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 (f) 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 cracking on the actuator attach fittings of the trailing edge flaps, which could result in abnormal operation or retraction of a trailing edge flap, and consequent reduced controllability of the airplane, accomplish the following: 

## Attach Fittings That Have Not Been Overhauled or Replaced 

                                (a) For attach fittings on the outboard flaps that have not been overhauled in accordance with Boeing 747 OHM 57-52-55, dated June 1, 1997, or replaced with a new fitting; and for attach fittings on the inboard actuators that have not been replaced with a new fitting: Accomplish the actions of paragraph (c) of this AD at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD.                                       ( print page 21677)    

(1) Prior to the accumulation of 8 years since date of manufacture or 8,000 total flight cycles, whichever occurs first. 

(2) Within 6 months after the effective date of this AD. 

## Attach Fittings That Have Been Overhauled or Replaced 

(b) For attach fittings on the outboard flaps that have been overhauled in accordance with Boeing 747 OHM 57-52-55, dated June 1, 1997, prior to the effective date of this AD, or replaced with a new fitting; and for attach fittings on the inboard actuators that have been replaced with a new fitting: Accomplish the actions of paragraph (c) of this AD at the later of the times specified in paragraphs (b)(1) and (b)(2) of this AD. 

(1) Within 8 years or 8,000 total flight cycles after the attach fitting was overhauled or replaced, whichever occurs first. 

(2) Within 6 months after the effective date of this AD. 

## Inspections and Corrective Action 

(c) Perform a detailed visual inspection to detect corrosion around the lower bearing journal on the actuator attach fittings on the inboard and outboard flaps, and perform an ultrasonic inspection to detect cracks around the lower bearing journal of the attach fittings of the outboard flaps, in accordance with Boeing Service Bulletin 747-57A2310, Revision 1, dated November 23, 1999. 

# Note 2:

For the purposes of this AD, a detailed 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 mirrors, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

# Note 3:

Inspections and replacements accomplished in accordance with Boeing Alert Service Bulletin 747-57A2310, dated June 17, 1999, are acceptable for compliance with the requirements of paragraph (c) of this AD.

(1) If no corrosion or cracks are detected, repeat the inspections required by paragraph (c) of this AD at intervals not to exceed 18 months. Within 5 years after the initial inspections required by paragraph (c) of this AD, accomplish the actions specified in paragraph (d) or (e) of this AD. 

(2) If any corrosion is detected, prior to further flight, remove the corrosion by accomplishing the actions of either paragraph (c)(2)(i) or (c)(2)(ii) of this AD. 

(i) If corrosion is within the limits of the Boeing 747 Overhaul Manual, prior to further flight, accomplish the actions specified in paragraph (d) or (e) of this AD. 

(ii) If corrosion is not within the limits of the Boeing 747 Overhaul Manual, prior to further flight, accomplish the actions specified in paragraph (e) of this AD. 

(3) If any crack is detected, prior to further flight, accomplish the actions specified in paragraph (e) of this AD. 

## Overhaul 

(d) Overhaul the actuator attach fittings on the outboard flaps in accordance with Boeing OHM 57-52-55, Temporary Revision 57-7, dated June 1, 1999. Repeat the overhaul of actuators on the outboard flaps as specified in Part 2 of the Work Instructions of the service bulletin thereafter at intervals not to exceed 8 years or 8,000 flight cycles, whichever occurs first. Accomplishment of the overhaul of the attach fittings on the outboard flaps constitutes terminating action for the repetitive inspection requirements of paragraph (c)(1) of this AD. Overhaul the attach fittings on the inboard flaps in accordance with Boeing OHM 57-52-35, Temporary Revision 57-8, dated June 10, 1999. Accomplishment of the overhaul of the actuators on the inboard flaps constitutes terminating action for the requirements of this AD for the inboard flap attach fittings. 

## Replacement 

(e) Replace the attach fittings on the inboard and outboard flap actuators with new attach fittings in accordance with Boeing Service Bulletin 747-57A2310, Revision 1, dated November 23, 1999. Accomplishment of the replacement constitutes terminating action for the repetitive inspection and overhaul requirements of paragraphs (c)(1), (c)(2), and (c)(3) of this AD. Within 8 years or 8,000 flight cycles following accomplishment of the replacement, whichever occurs first, repeat the replacement or accomplish the overhaul specified in paragraph (d) of this AD. 

# Note 4:

Replacement of the attach fitting on the inboard flaps with fittings that have been overhauled in accordance with Boeing OHM 57-52-35, Temporary Revision 57-8, dated June 10, 1999, constitutes terminating action for the requirements of this AD for the inboard flap attach fittings.

## Alternative Methods of Compliance 

(f) 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, Seattle 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, Seattle ACO. 

# Note 5:

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

## Special Flight Permits 

(g) 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 April 18, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-10162 Filed 4-21-00; 8:45 am] 

BILLING CODE 4910-13-U