02-207. Airworthiness Directives; Boeing Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, -300, -400, -400D, and -400F Series Airplanes; and Model 747SR Series Airplanes

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 certain Boeing Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, -300, -400, -400D, and -400F series airplanes; and Model 747SR series airplanes. For certain airplanes, this proposal would require repetitive inspections of the clevis bushings on the inboard and outboard sequence carriages of the wing foreflap for bushing migration, and corrective action, if necessary; replacement of existing bushings with new bushings, which would terminate the repetitive inspections; and replacement of the bushing markers with new markers, if necessary, to indicate the correct bushing orientation. For certain other airplanes, this proposal would require a one-time inspection to determine whether the bushings are in the correct orientation, and follow-on actions. This action is necessary to prevent the loss of an inboard trailing edge foreflap during flight, and subsequent damage to the airplane in flight. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by February 19, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket 2001-NM-117-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2001-NM-117-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 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:

John Craycraft, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

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 action 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 2001-NM-117-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 2001-NM-117-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report indicating that an operator of a Boeing Model 747 series airplane with 22,141 total flight hours and 7,268 total flight cycles discovered a broken lug on the inboard sequence carriage clevis of the wing foreflap during a routine check. Subsequently, another operator, with a Model 747 series airplane that had accumulated 5,790 total flight hours and 1,965 total flight cycles, found a cracked lug. In both cases, the bushing at the outboard lug had migrated out of place, resulting in bending loads on the lug. In one event, a Model 747 series airplane that had accumulated 114,036 total flight hours and 20,438 total flight cycles had the wing foreflap separate from the airplane during flight as a result of migrated bushings. The detached foreflap impacted the fuselage, creating a 5.5-foot-by-3-foot hole in the main cabin during flight. No operational problems had been reported prior to the discovery of the cracked or broken lugs. Continued operation of the airplane without detecting and replacing migrated bushings could result in loss of an inboard trailing edge foreflap during flight, which could subsequently cause damage to the airplane in flight.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993, which, for certain airplanes, describes procedures for a general visual inspection of the bushings of the clevis on the inboard and outboard sequence carriages of the inboard trailing edge foreflap to detect bushing migration, and corrective action, if necessary; repetitive inspections of the bushings until they have been replaced; replacement of the bushings with new bushings; and replacement of the markers installed on the airplane, if necessary, to ensure correct orientation of the bushings. For certain other airplanes, the service bulletin describes procedures for a one-time general visual inspection to determine whether the bushings are in the correct orientation, and follow-on actions. If the bushings are correctly oriented, follow-on action involves replacement of the existing markers on the airplane with new markers, if applicable, to ensure that bushings are oriented correctly in future replacements. If the bushings are incorrectly oriented, follow-on actions in the service bulletin involve correction of the orientation and replacement of the existing markers with new markers. 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 require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.

Differences Between Proposed Rule and Service Bulletin

Operators should note that this proposed AD would require, within 5 years, the bushing replacement described in Boeing Service Bulletin 747-57-2166, Revision 5, as terminating action for the repetitive inspections. (Incorporation of the terminating action is optional in the service bulletin.) 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 provide 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 replacement requirement is consistent with these conditions.

Operators also should note that, for airplanes on which the bushings have been replaced prior to the effective date of this AD in accordance with Boeing Service Bulletin 747-57-2166, Revision 4, dated December 6, 1990, or prior revisions, this proposed AD would require accomplishment of an inspection to determine whether the bushings are correctly oriented, and follow-on actions. This proposed AD would differ from the service bulletin in that, if any bushing is incorrectly oriented, the follow-on actions would involve accomplishment of the repetitive inspections for bushing migration and eventual replacement of the bushings with new bushings.

Operators should also note that the number of airplanes to which this AD is applicable is larger than that published in the service bulletin. Additional line numbers of airplanes have been included, as advised in Boeing Service Letter 747-SL-57-77, dated November 18, 1993. However, the FAA has further learned that the Boeing 747SP flaps are of a different design and are excluded from the proposed rule.

Cost Impact

There are approximately 589 airplanes of the affected design in the worldwide fleet. The FAA estimates that 222 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 7 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Required parts costs would be negligible. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $93,240, or $420 per airplane.

The cost impact figure discussed above is 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 proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

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.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Boeing: Docket 2001-NM-117-AD.

Applicability: Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, -300, -400, -400D, and -400F series airplanes; and Model 747SR series airplanes; certificated in any category; line numbers 1 through 1009, except 968, 999, 1004, and 1007.

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 (e) 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 the loss of an inboard trailing edge foreflap during flight, and subsequent damage to the airplane in flight, accomplish the following:

Inspections (Bushings Not Yet Replaced)

(a) For airplanes on which the bushings have not been replaced prior to the effective date of this AD in accordance with Boeing Service Bulletin 747-57-2166, Revision 4, dated December 6, 1990, or prior revisions: Prior to the accumulation of 5,000 total flight cycles, or within 1,200 flight cycles after the effective date of this AD, whichever occurs later, perform a general visual inspection of the bushings of the clevis on the inboard and outboard sequence carriages, flap tracks 3, 4, 5, and 6 of the inboard trailing edge foreflap, for bushing migration, in accordance with Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993.

Note 2:

For the purposes of this AD, a general visual inspection is defined as: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or drop-light, and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.”

(1) For each nondiscrepant bushing (with no migration): Repeat the inspection of that bushing at intervals not to exceed 1,200 flight cycles, until the terminating action required by paragraph (c) of this AD has been accomplished.

(2) For any discrepant bushing: Prior to further flight, replace the discrepant bushing with a new bushing and, if applicable, replace the bushing marker with a new marker, in accordance with Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993. No further action is required by this AD for that bushing only.

Note 3:

It is not necessary to replace the marker if the marker installed on the airplane shows the correct bushing orientation (flange reversed, as shown in NEW CONFIGURATION, Figure 1, of Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993).

Inspection (Bushings Replaced)

(b) For airplanes on which the bushings have been replaced prior to the effective date of this AD in accordance with Boeing Service Bulletin 747-57-2166, Revision 4, dated December 6, 1990, or previous revisions: Prior to the accumulation of 5,000 total flight cycles, or within 1,200 flight cycles after the effective date of this AD, whichever occurs later, perform a one-time general visual inspection of the bushings of the clevis on the inboard and outboard sequence carriages, flap tracks 3, 4, 5, and 6 of the inboard trailing edge foreflap, to determine whether the bushings are oriented correctly, in accordance with Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993.

(1) For each bushing that is oriented correctly: Within 5 years after the effective date of this AD, replace the markers installed on the airplane with new markers, as applicable, in accordance with Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993.

Note 4:

It is not necessary to replace the marker if the marker installed on the airplane shows the correct bushing orientation (flange reversed, as shown in NEW CONFIGURATION, Figure 1, of Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993).

(2) For any bushing that is oriented incorrectly: Prior to further flight, perform a general visual inspection of the bushing for bushing migration, in accordance with Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993.

(i) For each nondiscrepant bushing (with no migration), repeat the inspection specified by paragraph (b)(2) of this AD at intervals not to exceed 1,200 flight cycles, until the terminating action required by paragraph (c) of this AD has been accomplished.

(ii) For any discrepant bushing: Prior to further flight, replace the discrepant bushing with a new bushing and, if applicable, replace the bushing marker with a new marker, in accordance with the service bulletin. No further action is required by this paragraph for that bushing only.

Note 5:

It is not necessary to replace the marker if the marker installed on the airplane shows the correct bushing orientation (flange reversed, as shown in NEW CONFIGURATION, Figure 1, of Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993).

Terminating Action

(c) Within 5 years after the effective date of this AD, replace the existing bushings of the clevis on the inboard and outboard sequence carriages, in flap tracks 3, 4, 5, and 6 of the inboard trailing edge foreflap, in accordance with Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993. Replacement of the bushings in accordance with Boeing Service Bulletin 747-57-2166, Revision 4, dated December 6, 1990, or earlier, is acceptable, provided the bushings are inspected as required by paragraph (b) of this AD and found to be in the correct orientation. Also, as applicable, before further flight, replace the markers installed on the airplane with new markers in accordance with Boeing Service Bulletin 747-57-2166, Revision 5. Replacement of all bushings, and markers as applicable, terminates the requirements of this AD.

Note 6:

It is not necessary to replace the marker if the marker installed on the airplane shows the correct bushing orientation (flange reversed, as shown in NEW CONFIGURATION, Figure 1, of Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993).

Spares

(d) As of the effective date of this AD, no person shall install on any airplane a carriage and toggle assembly unless it has been modified in accordance with Boeing Service Bulletin 747-57-2166, Revision 5, dated May 13, 1993.

Alternative Methods of Compliance

(e) 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. 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 7:

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

(f) 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 December 28, 2001.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.