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Proposed Rule

Airworthiness Directives; Boeing Model 747 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

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Start Preamble

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of two existing airworthiness directives (AD), applicable to all Boeing Model 747 series airplanes, which currently require that the FAA-approved maintenance inspection program be revised to include inspections that will give no less than the required damage tolerance rating for each structural significant item, and repair of cracked structure. Those ADs were prompted by a structural re-evaluation that identified additional structural elements where, if damage were to occur, supplemental inspections may be required for timely detection of fatigue cracking. This action would require additional and expanded inspections, and repair of cracked structure. This action also would expand the applicability of the existing ADs to include additional airplanes. The actions specified by the proposed AD are intended to ensure the continued structural integrity of the entire fleet of Model 747 series airplanes.

DATES:

Comments must be received by April 28, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-47-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 (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2003-NM-47-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.

Start Further Info

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) 917-6421; fax (425) 917-6590.

End Further Info End Preamble Start Supplemental Information

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 Start Printed Page 11765in 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 2003-NM-47-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. 2003-NM-47-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

In the early 1980's, as part of its continuing work to maintain the structural integrity of older transport category airplanes, the FAA concluded that the incidence of fatigue cracking may increase as these airplanes reach or exceed their design service objective (DSO). A significant number of these airplanes were approaching or had exceeded the DSO on which the initial type certification approval was predicated. In light of this, and as a result of increased utilization, longer operational lives, and the high levels of safety expected of the currently operated transport category airplanes, we determined that a supplemental structural inspection program (SSIP) was necessary to ensure a high level of structural integrity for all airplanes in the transport fleet.

Issuance of Advisory Circular

As a follow-on from that determination, the FAA issued Advisory Circular (AC) No. 91-56, “Supplemental Structural Inspection Program for Large Transport Category Airplanes,” dated May 6, 1981. That AC provides guidance material to manufacturers and operators for use in developing a continuing structural integrity program to ensure safe operation of older airplanes throughout their operational lives. This guidance material applies to transport airplanes that were certified under the fail-safe requirements of part 4b (“Airplane Airworthiness, Transport Categories”) of the Civil Air Regulations or damage tolerance structural requirements of part 25 (“Airworthiness Standards: Transport Category Airplanes”) of the Federal Aviation Regulations (FAR) (14 CFR part 25), and that have a maximum gross weight greater than 75,000 pounds. The procedures set forth in that AC are applicable to transport category airplanes operated under subpart D (“Special Flight Operations”) of part 91 of the FAR (14 CFR part 91); part 121 (“Operating Requirements: Domestic, Flag, and Supplemental Operations”); part 125 (“Certification and Operations: Airplanes having a Seating Capacity of 20 or More Passengers or a Maximum Payload of 6,000 Pounds or More”); and part 135 (“Operating Requirements: Commuter and On-Demand Operations”) of the FAR (14 CFR parts 121, 125, and 135). The objective of the SSIP was to establish inspection programs to ensure timely detection of fatigue cracking.

Development of the SSIP

In order to evaluate the effect of increased fatigue cracking with respect to maintaining fail-safe design and damage tolerance of the structure of Boeing Model 747 series airplanes, Boeing conducted a structural reassessment of those airplanes, using modern damage tolerance evaluation techniques. Boeing accomplished this reassessment using the criteria contained in AC No. 91-56, as well as Amendment (Amdt.) 25-45 of section 25.571 (“Damage-tolerance and fatigue evaluation of structure”) of the FAR (14 CFR 25.571). During the reassessment, members of the airline industry participated with Boeing in working group sessions and developed the SSIP for Model 747 series airplanes. Engineers and maintenance specialists from the FAA also attended these sessions to observe these developments. Subsequently, based on the working group's recommendations, Boeing developed the Supplemental Structural Inspection Document (SSID).

Current Model 747 Series Airplanes ADs

On July 18, 1994, the FAA issued AD 94-15-12, amendment 39-8983 (59 FR 37933, July 26, 1994), applicable to certain Boeing Model 747-100SR series airplanes. Additionally, on July 22, 1994, we issued AD 94-15-18, amendment 39-8989 (59 FR 41233, August 11, 1994), applicable to certain Boeing Model 747 series airplanes. Both of those ADs currently require that the FAA-approved maintenance inspection program be revised to include inspections that will give no less than the required damage tolerance rating (DTR) for each structural significant item (SSI), and repair of cracked structure. AD 94-15-12 references Boeing Document No. D6-35655, “Supplemental Structural Inspection Document (SSID) for 747-100SR,” dated April 2, 1986; and AD 94-15-18 references Boeing Document No. D6-35022, “Supplemental Structural Inspection Document (SSID) for Model 747 Airplanes,” Revision E, dated June 17, 1993; as the appropriate sources of service information. Those actions were prompted by a structural re-evaluation that identified additional structural components where fatigue cracking is likely to occur. The requirements of those ADs are intended to ensure the continued structural integrity of the entire Model 747 fleet in service at the time of issuance of those ADs.

Other ADs Regarding SSIPs

On December 30, 1998, the FAA issued SSIP AD 98-11-03 R1, amendment 39-10983 (64 FR 989, January 7, 1999) for Boeing Model 727 series airplanes and SSIP AD 98-11-04 R1 (64 FR 987, January 7, 1999) for Boeing Model 737 series airplanes. Those ADs, in addition to their primary purpose to require inspection of baseline structure, also address repairs, alterations, and modifications (RAMs). Those ADs require operators to provide damage tolerance-based inspection programs for RAMs that affect principal structural elements or that create new principal structural elements.

This proposed AD for Boeing Model 747 series airplanes will address a damage tolerance-based inspection program only for the baseline structure and will not include RAMs. If a RAM interferes with the inspection of baseline structure, then this area must be addressed per Note 1 of the proposed AD. Start Printed Page 11766

Addressing RAMs

In April of 2000, an FAA team was chartered to address standardization of the SSIP ADs with regard to RAMs. The team was formed due to concerns of operators regarding different approaches to addressing RAMs for the McDonnell Douglas series airplanes versus the Boeing Model 727 and 737 series airplanes. Also, since the issuances of AD 98-11-03 R1 and AD 98-11-04 R1, operators have had various problems addressing RAMs. As announced in a Notice of Public Meeting, published in the Federal Register on January 15, 2003 (68 FR 2103), a public meeting will be held to present our view and to receive comments from the public. Due to the many issues that have arisen in addressing RAMs, this proposed AD will not require damage tolerance-based inspections for RAMs on Boeing Model 747 series airplanes.

Aging Airplane Safety Rule (AASR)

The AASR was published in the Federal Register on December 6, 2002 (67 FR 72726). That rule requires the maintenance program applicable to affected airplanes to include damage tolerance-based inspections and procedures that include all major structural repairs, alterations, and modifications. The compliance time for these procedures is four years after December 8, 2003 (the effective date of the AASR). The FAA intends to eventually require damage tolerance-based inspections for RAMs during subsequent rulemaking. (See the information under the “Interim Action” paragraph of this proposed AD.)

Other SSIP Issues

Since the issuance of the current SSIP ADs for Model 747 series airplanes (ADs 94-15-12 and 94-15-18), the FAA has reconsidered the following two aspects of the existing SSIP:

1. Candidate fleet vs. inspection threshold approach. Paragraph 4.4 of AC No. 91-56, Change 2, dated April 15, 1983, states, “Inspection thresholds for supplemental inspections should be established. These inspections would be supplemental to the normal inspection including the detailed internal inspections.” Moreover, paragraph 4.4.2 of AC No. 91-56 states, “ * * * this threshold should be such as to include sufficient [high-cycle] airplanes in the inspection to develop added confidence in the integrity of the structure . . . .”

A properly established inspection threshold ensures that: (1) The SSI inspections are accomplished; (2) fatigue cracks in SSIs are detected in a timely manner; (3) airplanes are automatically added to the SSIP; and (4) the SSIP includes a statistically valid number of airplanes.

Among other things, SSID D6-35655 and Revision E of SSID D6-35022 (referenced as the appropriate service information in ADs 94-15-12 and 94-15-18) define a candidate fleet approach to ensure that fatigue cracks in SSIs are detected in a timely manner in the entire fleet of Model 747 series airplanes. The initial candidate fleet of Model 747-100 and -200 series airplanes, as defined in SSID D6-35022, consisted of a number of airplanes that had exceeded 10,000 total flight cycles by June 30, 1983. The initial candidate fleet of Model 747SR series airplanes, as defined in SSID D6-35655, consisted of a number of airplanes that had exceeded 12,000 total flight cycles by January 1, 1985. In other words, Boeing considered 10,000 total flight cycles for Model 747-100 and -200 series airplanes, and 12,000 total flight cycles for Model 747SR series airplanes, to be the threshold for the airplanes in the candidate fleets. Those airplanes were the most likely airplanes in the fleets to experience initial fatigue damage, because they had the highest number of flight cycles. Boeing produced those SSIDs with the assumption that the airplanes in the candidate fleets would continue to represent the entire fleet and would have the highest number of flight cycles in the fleet.

Under the existing SSIP, Boeing intended to periodically review the airplanes in the candidate fleet for significant changes in fleet distribution, composition, or utilization, and update of the candidate fleet, if any significant change was detected. It was intended that the FAA would then mandate any change to the SSID through the rulemaking process.

The FAA finds that the candidate fleet approach is deviating from Boeing's original philosophy in that the candidate fleet has not been updated to reflect changes in the fleet. This situation could result in a statistically invalid number of airplanes in the SSIP and undetected fatigue cracks in SSIs. The candidate fleet approach also does not automatically account for non-candidate airplanes that eventually accumulate more flight cycles than those of certain candidate airplanes. High-cycle airplanes are more likely to experience initial fatigue damage in the fleet. The confidence in the structural integrity of the fleet of airplanes could be reduced if high-cycle airplanes are excluded from the SSIP.

The FAA has reconsidered the candidate fleet approach described in SSID D6-35655 and Revision E of SSID D6-35022 because it does not meet the guidelines of AC No. 91-56. We have also determined that the Model 747 SSIP must contain inspection thresholds for all Model 747 series airplanes to ensure the timely detection of fatigue cracks in the SSIs.

The FAA has reviewed the thresholds derived from Boeing's statistical analysis. The analysis is based on a certain probability that cracks will be detected in the inspected fleet before they initiate on other airplanes that have not been inspected. We find that the thresholds recommended in Revision G of SSID D6-35022 for the Model 747 airplane fleet are acceptable. Therefore, we have determined that a threshold of 20,000 total flight cycles or 100,000 total flight hours, whichever comes first, on wing structure, and 20,000 total flight cycles on all other structures are necessary in order to produce a statistically valid assessment of the service history for these airplanes. The original threshold for the Model 747SR series airplane was set higher by the manufacturer because it was believed that these airplanes were not subject to the same fatigue cycles due to use of a lower cabin differential pressure. We have since determined that an adjustment of flight cycles due to a lower cabin differential pressure is not substantiated and will not be allowed for use in determining the flight cycle threshold and inspection intervals of the SSID program. Therefore, the threshold for Model 747SR series airplanes is now the same as that of other Model 747 series airplanes.

It should be noted that, although the proposed AD specifies a threshold, the FAA may approve requests for adjustments to the compliance time (i.e., under the provisions of paragraph (g)(1) of this proposed AD) provided that no cracking is detected in the airplane structure. The request should include a new proposed inspection threshold and must include data to substantiate that such an adjustment would provide an acceptable level of safety.

Operators also should note that the alternative inspection threshold may be based solely on the analysis of the data of the existing fleet. However, the FAA has determined that the analysis that derives the new inspection threshold must include: (1) Data relevant to a sufficient number of high-cycle airplanes, and (2) data that show accomplishment of the inspections of the SSIs. An adequate statistical sampling size will provide confidence in the structural integrity of the fleet of airplanes. Therefore, additional airplanes may need to be added to the inspected fleet until a sufficient number Start Printed Page 11767of airplanes have been inspected with no crack findings.

2. Transferability of airplanes. Since issuance of AD 94-15-12 and AD 94-15-18, the FAA has issued several ADs that implement Corrosion Prevention and Control Programs (CPCP) for aging airplanes. While developing the ADs that mandated the CPCP, we recognized that an operator of an airplane that has been transferred from another operator could revise its maintenance or inspection program to restart the compliance times for the required corrosion tasks. This situation could lead to corrosion not being detected and corrected in a timely manner, which could reduce the structural integrity of the airplane.

As a result, the CPCP ADs require that operators establish a program for accomplishment of the subject corrosion tasks before any airplane can be added to an air carrier's operations specification. Establishment of such a program ensures that airplanes transferred from operator to operator are inspected and that corrosion is detected in a timely manner.

The FAA's intent in AD 94-15-12 and AD 94-15-18 was that operators of candidate fleet airplanes that have been previously operated under an FAA-approved maintenance or inspection program would accomplish the SSID inspections within the compliance time established by the previous operator. We assumed that, under the existing SSIDs, these airplanes would be inspected in a manner similar to CPCP requirements. However, the SSID ADs, AD 94-15-12 and AD 94-15-18, do not specifically address the transfer of airplanes in the candidate fleet from one operator to another.

AD 94-15-12 and AD 94-15-18 currently require that the revision to the maintenance inspection program be included and be implemented per the procedures specified in Sections 5.0 and 6.0 of the SSIDs. However, the FAA finds that those sections do not provide explicit instructions to repetitively inspect airplanes that have been transferred from one operator to another. Those sections also do not specify that new operators must continue the SSID inspections at the same frequency established by the previous operator.

In addition, as AD 94-15-12 and AD 94-15-18 are currently worded, the FAA finds that operators, who acquire candidate fleet airplanes that have been previously operated under a maintenance inspection program, could revise their programs to restart the compliance times. This situation is contrary to standard AD requirements. An AD typically mandates an initial compliance time and a repetitive interval that remains unchanged for all operators of the affected airplanes.

As a result of these omissions, the SSID inspections of a candidate fleet airplane could be deferred until it is required by the maintenance inspection program of the new operator. For airplanes that are transferred frequently, this situation could continue for the life of the airplane. As a result, the size of the candidate fleet is in effect reduced because fewer candidate fleet airplanes are being inspected. Even if airplanes are ultimately inspected under these circumstances, inspections would not be performed frequently enough to maintain the applicable DTR. The FAA has determined that such a reduction of the candidate fleet and the resulting reduction in the number of airplanes being inspected do not ensure the continued structural integrity of the entire fleet of Model 747 series airplanes.

Implementation of procedures in the SSID that are similar to the CPCP will ensure that: (1) Airplanes transferred from operator to operator are inspected; (2) the SSIP includes a statistically valid number of airplanes; and (3) fatigue cracks are detected in a timely manner.

Therefore, the FAA finds that, to ensure the continued structural integrity of the entire fleet of Model 747 series airplanes, AD 94-15-12 and AD 94-15-18 must be superseded to include provisions that address the transfer of airplanes. We also find that a program must be established to ensure that inspections are accomplished before any applicable airplane can be added to an air carrier's operations specifications.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Document No. D6-35022, “Supplemental Structural Inspection Document” (SSID), Revision F, dated May 1996, as an alternative method of compliance to AD 94-15-18. Revision F of SSID D6-35022 describes procedures for revising the FAA-approved maintenance inspection program for all Model 747-100, -200B, -200C, and -200F series airplanes. This revision of the SSID for Model 747 series airplanes incorporates additional and expanded inspections from those that were contained in the previous version and mandated by AD 94-15-18. We also reviewed and approved Boeing Document No. D6-35022, “Supplemental Structural Inspection Document” (SSID), Revision G, dated December 2000. Revision G affects all Model 747-SP, -SR, -100, -100B, -100SUD, -200B, -200C, -200F, -300, -400, -400D, and -400F series airplanes, and supersedes Boeing Document No. D6-35655 for 747-SR series airplanes. This revision also adds additional inspection requirements. We find that accomplishment of these inspections in Boeing Document No. D6-35022, “Supplemental Structural Inspection Document” (SSID), Revision G, dated December 2000, will ensure the continuing structural integrity of the identified fleet of Model 747 series airplanes. Accomplishment of the actions specified in Revision G 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 94-15-12 and AD 94-15-18 to require the following actions:

Paragraph (a) of the proposed AD restates the requirements of AD 94-15-

12. Paragraph (b) of the proposed AD restates the requirements of paragraph (b) of AD 94-15-18. Although AD 94-15-18 specifies Revision E of Boeing Document No. D6-35022 as the appropriate source of service information for that AD, this proposed AD also permits incorporation of Revision F, of Boeing Document No. D6-35022, dated May 1996, until the compliance time for incorporation of Revision G is reached. (Paragraph (a) of AD 94-15-12 is no longer necessary because that paragraph required an earlier revision of the SSID than that required by paragraph (b).)

Paragraph (c) of the proposed AD would require incorporation of a revision into the FAA-approved maintenance or inspection program that provides no less than the required DTR for each SSI listed in Revision G of SSID D6-35022.

Paragraph (d) of the proposed AD would establish specific compliance times for performing the initial inspection of the structure identified in Revision G of SSID D6-35022. Once the initial inspection has been performed, operators would be required to perform repetitive inspections at the intervals specified in Revision G of SSID D6-35022 in order to remain in compliance with their maintenance or inspection programs, as specified in paragraph (c) of this proposed AD.

Paragraph (e) of the proposed AD would require that repair of any cracked structure is to be accomplished per an FAA-approved method. Start Printed Page 11768

Paragraph (f) of the proposed AD specifies the requirements of the inspection program for transferred airplanes. Before any airplane that is subject to this proposed AD can be added to an air carrier's operations specifications, a program for the accomplishment of the inspections required by this proposed AD must be established. Paragraph (f) of the proposed AD would require accomplishment of the following:

1. For airplanes that have been inspected per this proposed AD, the inspection of each SSI must be accomplished by the new operator per the previous operator's schedule and inspection method, or per the new operator's schedule and inspection method, at whichever time would result in the earlier accomplishment date for that SSI inspection. The compliance time for accomplishment of this inspection must be measured from the last inspection accomplished by the previous operator. After each inspection has been performed once, each subsequent inspection must be performed per the new operator's schedule and inspection method.

2. For airplanes that have not been inspected per this proposed AD, the inspection of each SSI must be accomplished either prior to adding the airplane to the air carrier's operations specification, or per a schedule and an inspection method approved by the FAA. After each inspection has been performed once, each subsequent inspection must be performed per the new operator's schedule.

Accomplishment of these actions will ensure that: (1) An operator's newly acquired airplanes comply with its SSIP before being operated; and (2) frequently transferred airplanes are not permitted to operate without accomplishment of the inspections defined in the SSID.

Interim Action

This is considered to be interim action. The FAA is currently considering requiring damage tolerance-based inspections and procedures that include all major structural RAMs in a superseding AD. That superseding AD would include appropriate recommendations from the previously mentioned FAA team and public meeting on how to address RAMs.

Differences Between SSID and Proposed AD

Operators should note the following differences between the procedures specified in Revision G of SSID D6-35022 and the proposed requirements of this AD:

1. Revision G of SSID D6-35022 provides for phased inspections or rotational sampling of inspections. This proposed AD would not allow phased inspections or rotational sampling.

2. Revision G of SSID D6-35022 allows individual operators to combine their affected airplanes with those of other operators to fulfill requirements of the SSIP. This proposed AD would not allow for phased inspections or a candidate fleet; therefore, this proposed AD would not allow an operator to take credit for inspections accomplished on another operator's airplane.

3. Revision G of SSID D6-35022 contains blanket provisions for touch-and-go training flights, which are not allowed by this proposed AD. Revision G of SSID D6-35022 also allows for fleet averaging, and arbitrary 10% escalations for flight cycles to achieve the required DTR. These procedures are not allowed in this proposed AD.

4. Revision G of SSID D6-35022 does not provide an implementation grace period when an operator's airplane is near or passed the threshold. This proposed AD will allow 12 months after the effective date of the AD to incorporate Revision G of SSID D6-35022 into the FAA-approved maintenance or inspection program. This proposed AD will also allow a grace period of 1,000 flight cycles measured from 12 months after the effective date of the proposed AD.

Cost Impact

There are approximately 1,000 airplanes of the affected design in the worldwide fleet.

The FAA estimates that 87 airplanes of U.S. registry are currently affected by the requirements of AD 94-15-12 and AD 94-15-18. Those required actions take approximately 1,000 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 $5,220,000, or $60,000 per airplane, per inspection cycle.

The FAA estimates that 181 airplanes of U.S. registry would be affected by this proposed AD. The new actions that are proposed in this AD action would take approximately 1,275 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 proposed requirements of this AD on U.S. operators is estimated to be $13,846,500, or $76,500 per airplane, per inspection cycle.

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.

The number of proposed work hours, as indicated above, is presented as if the accomplishment of the actions proposed in this AD were to be conducted as “stand alone” actions. However, in actual practice, these actions for the most part would be accomplished coincidentally or in combination with normally scheduled airplane inspections and other maintenance program tasks. Therefore, the actual number of necessary additional work hours would be minimal in many instances. Additionally, any costs associated with special airplane scheduling would be minimal.

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.

Start List of Subjects

List of Subjects in 14 CFR Part 39

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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:

Start Part

PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Start Authority

Authority: 49 U.S.C. 106(g), 40113, 44701.

End Authority
Start Printed Page 11769
[Amended]

2. Section 39.13 is amended by removing amendments 39-8983 (59 FR 37933, July 26, 1994) and 39-8989 (59 FR 41233, August 11, 1994), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2003-NM-47-AD. Supersedes AD 94-15-12, amendment 39-8983, and AD 94-15-18, amendment 39-8989.

Applicability: All Model 747 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 per paragraph (g)(1) 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 ensure the continued structural integrity of the entire fleet of Model 747 series airplanes, accomplish the following:

Note 2:

Where there are differences between this AD and the Supplemental Structural Inspection Document (SSID) specified in this AD, the AD prevails.

Inspection Program Required by AD 94-15-12

(a) For Model 747-100SR series airplanes having line numbers 346, 351, 420, 426, 427, and 601: Within 1 year after August 10, 1994 (the effective date of AD 94-15-12, amendment 39-8983), incorporate a revision into the FAA-approved maintenance inspection program that provides no less than the required damage tolerance rating (DTR) for each structural significant item (SSI) listed in Boeing Document No. D6-35655, “Supplemental Structural Inspection Document (SSID) for 747-100SR,” dated April 2, 1986. The revision to the maintenance program must include and be implemented per the procedures specified in Sections 5.0 and 6.0 of the SSID D6-35655. Revision to the maintenance program shall be per the SSID D6-35655, dated April 2, 1986, until Revision G of the SSID D6-35022 is incorporated into the FAA-approved maintenance or inspection program per the requirements of paragraph (c) of this AD.

Note 3:

For the purposes of this AD, an SSI is defined as a principal structural element (PSE). A PSE is a structural element that contributes significantly to the carrying of flight, ground, or pressurization loads, and whose integrity is essential in maintaining the overall structural integrity of the airplane.

Inspection Program Required by AD 94-15-18

(b) For airplanes listed in Boeing Document No. D6-35022, Volumes 1 and 2, “Supplemental Structural Inspection Document (SSID) for Model 747 Airplanes,” Revision E, dated June 17, 1993; and manufacturer's line numbers 42, 174, 221, 231, 234, 239, 242, and 254: Within 12 months after September 12, 1994 (the effective date of AD 94-15-18, amendment 39-8989), incorporate a revision into the FAA-approved maintenance inspection program that provides no less than the required DTR for each SSI listed in Boeing Document No. D6-35022, Volumes 1 and 2, “Supplemental Structural Inspection Document (SSID) for Model 747 Airplanes,” Revision E, dated June 17, 1993, or Revision F, dated May 1996. (The required DTR value for each SSI is listed in the document.) The revision to the maintenance program shall include Sections 5.0 and 6.0 of the SSID D6-35022 and shall be implemented per the procedures contained in those sections. Revision to the maintenance program shall be per Revision E or F of SSID D6-35022, until Revision G of the SSID D6-35022 is incorporated into the FAA-approved maintenance or inspection program per the requirements of paragraph (c) of this AD.

New Inspection Program Requirements

(c) For all Model 747 series airplanes: Prior to reaching either of the thresholds specified in paragraph (d)(1)(i) or (d)(2)(i) of this AD, or within 12 months after the effective date of this AD, whichever occurs later, incorporate a revision into the FAA-approved maintenance or inspection program that provides no less than the required DTR for each SSI listed in Boeing Document No. D6-35022, “Supplemental Structural Inspection Document,” Revision G, dated December 2000 (hereinafter referred to as “Revision G”). (The required DTR value for each SSI is listed in Revision G.) The revision to the maintenance or inspection program shall include and shall be implemented per the procedures in Section 5.0, excluding paragraphs 5.1.2, 5.1.6, item 5; 5.1.8; 5.2; 5.2.1; 5.2.2; 5.2.3; and 5.2.4; “Damage Tolerance Rating (DTR) System Application;” and Section 6.0, “SSI Discrepancy Reporting;” of Revision G. Upon incorporation of Revision G required by this paragraph, the revision required by either paragraph (a) or (b) of this AD, as applicable, may be removed.

Initial Inspection

(d) For all Model 747 series airplanes: Perform an inspection to detect cracks of all structure identified in Revision G of SSID D6-35022 at the time specified in paragraph (d)(1) or (d)(2) of this AD, as applicable.

(1) For wing structure: At the times specified in paragraph (d)(1)(i) or (d)(1)(ii) of this AD, whichever occurs later.

(i) Prior to the accumulation of 20,000 total flight cycles or 100,000 total flight hours, whichever comes first. Or,

(ii) Within 1,000 flight cycles measured from 12 months after the effective date of this AD.

(2) For all other structure: At the times specified in paragraph (d)(2)(i) or (d)(2)(ii) of this AD, whichever occurs later.

(i) Prior to the accumulation of 20,000 total flight cycles, or

(ii) Within 1,000 flight cycles measured after 12 months from the effective date of this AD.

Note 4:

Notwithstanding the provisions of paragraphs 5.1.2, 5.1.6, item 5, 5.2, 5.2.1, 5.2.2, 5.2.3, and 5.2.4 of the General Instructions of Revision G, which would permit operators to perform fleet and rotational sampling inspections to perform inspections on less than whole airplane fleet sizes and to perform inspections on substitute airplanes, this AD requires that all airplanes that exceed the threshold be inspected per Revision G. Paragraph 5.1.8 allows provisions for touch-and-go training flights, fleet averaging, and 10% escalations of flight cycles to achieve the required DTR. This AD does not allow for these provisions as well.

Note 5:

Once the initial inspection has been performed, operators are required to perform repetitive inspections at the intervals specified in Revision G in order to remain in compliance with their maintenance or inspection programs, as revised per paragraph (c) of this AD.

Repair

(e) Cracked structure found during any inspection required by this AD shall be repaired, prior to further flight, in accordance with an FAA-approved method.

Inspection Program for Transferred Airplanes

(f) Before any airplane that is subject to this AD and that has exceeded the applicable compliance times specified in paragraph (d) of this AD can be added to an air carrier's operations specifications, a program for the accomplishment of the inspections required by this AD must be established per paragraph (f)(1) or (f)(2) of this AD, as applicable.

(1) For airplanes that have been inspected per this AD, the inspection of each SSI must be accomplished by the new operator per the previous operator's schedule and inspection method, or the new operator's schedule and inspection method, at whichever time would result in the earlier accomplishment date for that SSI inspection. The compliance time for accomplishment of this inspection must be measured from the last inspection accomplished by the previous operator. After each inspection has been performed once, each subsequent inspection must be performed per the new operator's schedule and inspection method.

(2) For airplanes that have not been inspected per this AD, the inspection of each SSI required by this AD must be accomplished either prior to adding the airplane to the air carrier's operations specification, or per a schedule and an inspection method approved by the Manager, Seattle Aircraft Certification Office (ACO). After each inspection has been performed once, each subsequent inspection must be performed per the new operator's schedule. Start Printed Page 11770

Alternative Methods of Compliance

(g)(1) 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. 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.

(2) Alternative methods of compliance, approved previously per AD 94-15-12, amendment 39-8983, are approved as alternative methods of compliance with paragraphs (a) and (e) of this AD.

(3) Alternative methods of compliance, approved previously per AD 94-15-18, amendment 39-8989, are approved as alternative methods of compliance with paragraphs (b) and (e) of this AD.

(4) Alternative methods of compliance, approved previously per AD 94-15-18 and AD 94-15-12 that provide alternative inspections are approved as alternative methods of compliance for the inspections of that area only in this AD.

Note 6:

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

(h) Special flight permits may be issued per 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.

Start Signature

Issued in Renton, Washington, on March 5, 2003.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 03-5857 Filed 3-11-03; 8:45 am]

BILLING CODE 4910-13-P