02-457. Airworthiness Directives; Boeing Model 747 Series Airplanes Powered by General Electric (GE) CF6-45/50, Pratt & Whitney (P&W) JT9D-70, or JT9D-7 Series Engines

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 series airplanes powered by GE CF6-45/50, P&W JT9D-70, or JT9D-7 series engines. This proposal would require repetitive inspections to find cracks and broken fasteners of the inboard and outboard nacelle struts of the rear engine mount bulkhead, and repair, if necessary. For certain airplanes, this proposal provides for an optional terminating modification for the inspections of the outboard nacelle struts. This action is necessary to find and fix cracks and broken fasteners of the inboard and outboard nacelle struts, which could result in possible loss of the bulkhead load path and consequent separation of the engine from the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by February 25, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-40-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. 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-40-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:

Tamara Anderson, 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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2001-NM-40-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. 2001-NM-40-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports indicating that fatigue cracking of the inboard and outboard nacelle struts of the rear engine mount bulkhead was found on certain Boeing Model 747 series airplanes powered by General Electric CF6-45/50 and Pratt & Whitney (P&W) JT9D-3, -7, and -70 series engines. Cracking found on airplanes powered by P&W JT9D-3 and -7 series engines was located in the frame webs at the inner angles, extending in a radial direction. Cracking also was found in the inner flange radius and web. Cracking found on airplanes powered by GE CF6-45/50 and P&W JT9D-70 series engines was located in the frame flange common to the strut skin. Such cracking, if not found and fixed, could result in possible loss of the bulkhead load path and consequent separation of the engine from the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000, which describes procedures for repetitive detailed visual and high frequency eddy current (HFEC) inspections to find cracks and broken fasteners of the inboard and outboard nacelle struts of the rear engine mount bulkhead, and repair, if necessary. For certain airplanes with web doublers installed per the Boeing service bulletins listed below, an HFEC inspection is to be done in the stop-drilled holes or around the fasteners, if installed. The service bulletin specifies contacting Boeing for repair instructions if discrepancies (cracks, broken fasteners) are found.

The FAA also has reviewed and approved Boeing Service Bulletins 747-54-2033, Revision 2, dated July 29, 1977, and 747-54-2065, Revision 6, dated May 29, 1997. These service bulletins describe procedures for a detailed visual inspection for cracks and broken fasteners, and modification of the outboard nacelle struts of the rear engine mount bulkhead. These service bulletins are referenced in Boeing Alert Service Bulletin 747-54A2202.

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 alert service bulletin described previously, except as discussed below.

Differences Between Alert Service Bulletin and This Proposed AD

The alert service bulletin specifies that the manufacturer must be contacted for repair of certain conditions, but this proposal would require the repair of those conditions to be accomplished per a method approved by the FAA, or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

Interim Action

This is considered to be interim action. At this time, the FAA is considering a separate rulemaking action to mandate accomplishment of the optional terminating modification for certain outboard struts, and the manufacturer has advised that it currently is developing a terminating modification for the inboard struts and the remaining outboard struts.

Cost Impact

There are approximately 456 airplanes of the affected design in the worldwide fleet. The FAA estimates that 165 airplanes of U.S. registry would be affected by this proposed AD.

It would take approximately 4 work hours per airplane to accomplish the proposed detailed visual inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed inspection on U.S. operators is estimated to be $39,600, or $240 per airplane, per inspection cycle.

It would take approximately 32 work hours per airplane to accomplish the proposed high frequency eddy current inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed high frequency eddy current inspection on U.S. operators is estimated to be $316,800, or $1,920 per airplane, per inspection cycle.

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 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.

Should an operator elect to accomplish the optional terminating modification that would be provided by this AD action, it would take approximately 368 work hours to accomplish, at an average labor rate of $60 per work hour. The cost of required parts would be approximately $20,000 per airplane. Based on these figures, the cost impact of the optional terminating action is estimated to be $42,080 per airplane.

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-40-AD.

Applicability: Model 747 series airplanes, as listed in Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000, 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 (g) 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 find and fix cracks and broken fasteners of the inboard and outboard nacelle struts of the rear engine mount bulkhead, which could result in possible loss of the bulkhead load path and consequent separation of the engine from the airplane, accomplish the following:

Detailed Visual Inspections

(a) Do a detailed visual inspection to find cracks and broken fasteners of the inboard and outboard nacelle struts of the rear engine mount bulkhead at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable. Do the inspection per Part 1 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000. Repeat the inspection at least every 350 flight cycles until paragraph (b) of this AD has been done.

(1) For airplanes on which the inspections specified in Boeing Service Bulletin 747-54-2065, Revision 6, dated May 29, 1997, HAVE NOT been done: Within 120 days after the effective date of this AD.

(2) For airplanes on which the inspections specified in Boeing Service Bulletin 747-54-2065, Revision 6, dated May 29, 1997, HAVE been done: Within 1,600 flight hours after doing the last inspection with no crack finding, or within 600 flight hours after doing the last inspection with a crack finding.

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.”

Detailed Visual/High Frequency Eddy Current Inspections

(b) Within 1,200 flight cycles or 18 months after the effective date of this AD, whichever is first: Do detailed visual and high frequency eddy current (HFEC) inspections to find cracks and broken fasteners of the inboard and outboard nacelle struts of the rear engine mount bulkhead per Part 1 and Part 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000, as applicable. Doing the inspections required by this paragraph terminates the inspections required by paragraph (a) of this AD.

(1) For airplanes on which the modification of the inboard struts specified in Boeing Service Bulletin 747-54-2065, Revision 6, dated May 29, 1997, HAS NOT been done: Repeat the applicable inspection at least every 1,200 flight cycles or 18 months, whichever is first.

(2) For Groups 3 and 4 airplanes on which the modification of the inboard struts specified in Boeing Service Bulletin 747-54-2065, Revision 6, dated May 29, 1997, HAS been done: Repeat the applicable inspection at least every 1,200 flight cycles.

(c) For Groups 1 and 5 airplanes, as listed in Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000, with web doublers and angle chords installed to repair cracking, as specified in Boeing Service Bulletin 747-54-2065, Revision 6, dated May 29, 1997; or Boeing Service Bulletin 747-54-2033, Revision 2, dated July 29, 1977: Within 1,200 flight cycles or 18 months after the effective date of this AD, whichever is first, do an HFEC inspection of the stop-drilled holes per Figure 1, Flag Notes 1 and 2, of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000. Repeat the inspection at least every 600 flight cycles.

Note 3:

Accomplishment of the actions specified in paragraphs (b)(1), (b)(2), and (c) of this AD before the effective date of this AD, per Boeing Service Bulletin 747-54-2033, dated September 13, 1974; or Revision 1, dated November 14, 1975; or Boeing Service Bulletin 747-54-2065, dated October 30, 1981; Revision 1, dated December 19, 1983; Revision 2, dated October 23, 1984; Revision 3, dated March 14, 1986; or Revision 5, dated November 2, 1989; is considered acceptable for compliance with the applicable actions specified in this AD.

Repair

(d) Except as provided by paragraph (e) of this AD: Before further flight, repair any discrepancy (crack or broken fastener) found during any inspection required by this AD, per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

(e) Web cracks in the existing bulkhead frames repaired with the web doublers and angle chords are acceptable, provided they are stop drilled and are within the limits specified in Figure 1, Flag Notes 1 and 2, of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000.

Optional Terminating Modification

(f) For Groups 3, 4, and 5 airplanes, as listed in Boeing Alert Service Bulletin 747-54A2202, dated December 21, 2000: Accomplishment of the modification of the outboard nacelle struts, as specified in Boeing Service Bulletin 747-54-2065, Revision 6, dated May 29, 1997, terminates the repetitive inspections required by paragraphs (a) and (b) of this AD for the outboard nacelle struts only.

Note 4:

Accomplishment of the modification of the outboard nacelle struts before the effective date of this AD per Boeing Service Bulletin 747-54-2065, dated October 30, 1981; Revision 1, dated December 19, 1983; Revision 2, dated October 23, 1984; Revision 3, dated March 14, 1986; or Revision 5, dated November 2, 1989; is considered acceptable for compliance with paragraph (e) of this AD.

Alternative Methods of Compliance

(g) 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 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 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 Permit

(h) 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 January 2, 2002.

Lirio Liu Nelson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.