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Proposed Rule

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

Document Details

Information about this document as published in the Federal Register.

Published Document

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Start Preamble Start Printed Page 12136

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747 airplanes. The existing AD currently requires repetitive inspections to detect cracks and/or corrosion of the girt bar support fitting at certain main entry doors (MED), and repair or replacement of the support fitting. The existing AD also provides for various terminating actions for the repetitive inspections. This proposed AD would require the following additional actions: An inspection, for certain airplanes, for correct installation of square and conical washers in the girt bar support fitting; an inspection, for certain other airplanes, to determine if the washers are installed; and related investigative and corrective action if necessary. This proposed AD results from a report that the square and conical washers may be installed incorrectly in the girt bar support fitting on airplanes on which the support fitting was repaired or replaced in accordance with the requirements of the existing AD. We are proposing this AD to detect and correct corrosion of the girt bar support fitting, which could result in separation of the escape slide from the lower door sill during deployment, and subsequently prevent proper operation of the escape slides at the main entry doors during an emergency. We are also proposing this AD to detect and correct incorrect installation of the square and conical washers in the girt bar support fitting, which could result in failure of the escape slide when deployed.

DATES:

We must receive comments on this proposed AD by April 30, 2007.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

  • DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
  • Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
  • Mail: Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, Washington, DC 20590.
  • Fax: (202) 493-2251.
  • Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for service information identified in this proposed AD.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Patrick Gillespie, Aerospace Engineer, Cabin Safety and Environmental Systems Branch, ANM-150S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6429; fax (425) 917-6590.

End Further Info End Preamble Start Supplemental Information

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “Docket No. FAA-2007-27525; Directorate Identifier 2006-NM-159-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Docket

You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647-5227) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them.

Discussion

On October 31, 1996, we issued AD 96-23-05, amendment 39-9810 (61 FR 58318, November 14, 1996), for certain Boeing Model 747 series airplanes. That AD requires repetitive inspections to detect cracks and/or corrosion of the girt bar support fitting at certain main entry doors (MED); and repair or replacement of the support fitting. That AD also provides for various terminating actions for the repetitive inspections. That AD resulted from reports that, during scheduled deployment tests of main entry door slides, corrosion was found on the floor structure supports for the escape slides of the main deck entry doors on these airplanes. We issued that AD to prevent such corrosion, which could result in separation of the escape slide from the lower door sill during deployment, and subsequently prevent proper operation of the escape slides at the main entry doors during an emergency.

Actions Since Existing AD Was Issued

Since we issued AD 96-23-05, Boeing has determined that the square and conical washers may be installed incorrectly in the girt bar support fitting on airplanes on which the support fitting was repaired or replaced in accordance with Boeing Service Bulletin 747-53A2378, dated June 24, 1993; Revision 1, dated March 10, 1994; or Revision 2, dated July 24, 2003 (Revision 1 of the service bulletin was referenced as the appropriate source of service information for doing the actions specified in AD 96-23-05).

Relevant Service Information

We have reviewed Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. The service bulletin contains essentially the same procedures for the actions described in the earlier revisions of the service bulletin, but Revision 3 revises the procedures for the installation of the square and conical washers on the girt bar support fitting. Start Printed Page 12137

Revision 3 also adds actions for airplanes on which the support fitting was replaced or repaired in accordance with any earlier revision of the service bulletin:

  • For Groups 7, 8, and 9 airplanes identified in the service bulletin: Do an inspection for correct installation of square and conical washers in the girt bar floor fitting, related investigative action, and corrective actions. The related investigative action is an inspection of the bolts and washers for damage. The corrective actions include installing the square and conical washers correctly and contacting the manufacturer if damage is found.
  • For Groups 1 through 6 airplanes identified in the service bulletin: Do an inspection to check if square and conical washers are installed in the girt bar floor fitting, related investigative actions, and corrective actions. The related investigative actions include doing an inspection for correct installation of square and conical washers in the girt bar floor fitting and an inspection of the bolts and washers for damage. The corrective actions include installing the square and conical washers correctly and contacting the manufacturer if damage is found.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to develop on other airplanes of the same type design. For this reason, we are proposing this AD, which would supersede AD 96-23-05 and would retain the requirements of the existing AD. This proposed AD would also require the following actions for airplanes on which the support fitting was repaired or replaced in accordance with Boeing Service Bulletin 747-53A2378, dated June 24, 1993; Revision 1, dated March 10, 1994; or Revision 2, dated July 24, 2003: An inspection, for certain airplanes, for correct installation of square and conical washers in the girt bar support fitting; an inspection, for certain other airplanes, to determine if the washers are installed; and related investigative and corrective action if necessary.

Differences Between the Proposed AD and the Service Bulletin

Although Boeing Service Bulletin 747-53A2378 specifies that operators may contact the manufacturer if certain damage is found, this proposed AD would require operators to repair those conditions using a method approved by the FAA.

Although Boeing Service Bulletin 747-53A2378, Revision 3, specifies doing certain actions if Boeing Service Bulletin 747-53A2378, dated June 24, 1993; Revision 1, dated March 10, 1994; or Revision 2, dated July 24, 2003; was accomplished, this proposed AD would require those actions to also be done if Boeing Service Bulletin 747-25A2831, dated August 29, 1991, was accomplished. Paragraph (m) of AD 96-23-05 allows installation of the girt bar fitting in accordance with Boeing Service Bulletin 747-25A2831 as an acceptable method of compliance. Therefore, installations done in accordance with Boeing Service Bulletin 747-25A2831 should also be inspected for incorrect installation of the square and conical washers in the girt bar support fitting.

Change to Existing AD

This proposed AD would retain all requirements of AD 96-23-05. Since AD 96-23-05 was issued, the AD format has been revised, and certain paragraphs have been rearranged. As a result, the corresponding paragraph identifiers have changed in this proposed AD, as listed in the following table:

Revised Paragraph Identifiers

Requirement in AD 96-23-05Corresponding requirement in this proposed AD
Note 1paragraph (f).
paragraph (a)paragraph (g).
paragraph (b)paragraph (h).
paragraph (c)paragraph (i).
paragraph (d)paragraph (j).
paragraph (e)paragraph (k).
paragraph (f)paragraph (l).
paragraph (g)paragraph (m).
paragraph (h)paragraph (n).
paragraph (i)paragraph (o).
paragraph (j)paragraph (p).
paragraph (k)paragraph (q).
paragraph (l)paragraph (r).
paragraph (m)paragraph (s).

Note 2 and paragraph (o) of AD 96-23-05 have been removed from this proposed AD. On July 10, 2002, the FAA issued a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs the FAA's airworthiness directives system. The regulation now includes material that relates to altered products and alternative methods of compliance (AMOCs), as well as special flight permits (e.g., ferry flights).

Clarification of Doors Affected by the Proposed AD

We have also revised Note 1 of AD 96-23-05, which has the corresponding requirement in paragraph (f) of this proposed AD. We have added the statement “the requirements of this AD are also not applicable to doors on airplanes converted to an all-cargo configuration.”

Explanation of Change to Applicability

We have revised the applicability of the existing AD to identify model designations as published in the most recent type certificate data sheet for the affected models. Special freighters are not identified in the type certificate data sheet so the phrase “special freighters” has been removed from the applicability. However, as stated previously, we have added a statement to exempt doors on airplanes converted to an all-cargo configuration.

Explanation of Change Made to Existing Requirements

We have changed all references to a “detailed visual inspection” in the existing AD to “detailed inspection” in this proposed AD.

Clarification of Alternative Method of Compliance (AMOC) Paragraph

We have revised this action to clarify the appropriate procedure for notifying the principal inspector before using any approved AMOC on any airplane to which the AMOC applies.

Costs of Compliance

There are about 1,012 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this proposed AD. The average labor rate per hour is $80. The cost varies depending on the configuration of the airplane. Start Printed Page 12138

Estimated Costs

ActionWork hoursCost per airplaneNumber of U.S.-registered airplanesFleet cost
Inspection of MEDs (required by AD 96-23-05)Between 88 and 102Between $7,040 and $8,160, per inspection cycle169Between $1,189,760 and $1,379,040, per inspection cycle.
Inspection for correct installation (new proposed action)6$480Up to 169Up to $81,120.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.

For the reasons discussed above, I certify that the 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. 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.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

Start List of Subjects

List of Subjects in 14 CFR Part 39

End List of Subjects

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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
[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by removing amendment 39-9810 (61 FR 58318, November 14, 1996) and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-27525; Directorate Identifier 2006-NM-159-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by April 30, 2007.

Affected ADs

(b) This AD supersedes AD 96-23-05.

Applicability

(c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-300, 747-400, 747-400D, 747SR, and 747SP series airplanes, certificated in any category, line numbers 1 through 868 inclusive.

Unsafe Condition

(d) This AD results from reports that, during scheduled deployment tests of main entry door slides, corrosion was found on the floor structure supports for the escape slides of the main deck entry doors on these airplanes. This AD also results from a report that the square and conical washers may be installed incorrectly in the girt bar support fitting on airplanes on which the support fitting was repaired or replaced in accordance with the requirements of AD 96-23-05. We are issuing this AD to detect and correct corrosion of the girt bar support fitting, which could result in separation of the escape slide from the lower door sill during deployment, and subsequently prevent proper operation of the escape slides at the main entry doors during an emergency. We are also issuing this AD to detect and correct incorrect installation of the square and conical washers in the girt bar support fitting, which could result in failure of the escape slide when deployed.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Restatement of Requirements of AD 96-23-05 With New Service Information

Doors Exempt From/Affected by This AD

(f) The requirements of this AD are not applicable to doors where an escape slide or slide/raft is not installed or is not used for passenger egress (such as a deactivated door 3, at doors 4 and/or 5 of an airplane being operated in the “combi” configuration, or any door not used for passenger egress in a “convertible” (an airplane configured for quick change from passenger to cargo)). The requirements of this AD are also not applicable to doors on airplanes converted to an all-cargo configuration. The requirements of this AD become applicable at the time when an escape slide or slide/raft is installed on such doors, or when such doors are activated and/or converted for passenger use. The requirements also become applicable at the time an airplane operating in an all-cargo configuration is converted to a passenger or passenger/cargo configuration.

Inspections and Corrective Actions for Airplanes Equipped With Main Entry Door (MED) 1

(g) For airplanes equipped with MED 1: Prior to the accumulation of 16 years of service since date of manufacture of the airplane, or within 18 months after December 16, 1996 (the effective date of AD 96-23-05), whichever occurs later, perform a detailed inspection to detect cracking and/or corrosion of the girt bar support fitting at the left and right MED 1, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(h) If no cracking or corrosion is found during the inspection required by paragraph (g) of this AD, prior to further flight, accomplish either paragraph (h)(1) or (h)(2) of this AD, in accordance with the applicable instructions specified in Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin Start Printed Page 12139747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(1) Install a new fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by paragraph (h) of this AD; or

(2) Reinstall the threshold assembly with corrosion-resistant fasteners, in accordance with the service bulletin. Thereafter, repeat the inspection required by paragraph (g) of this AD at intervals not to exceed 6 years.

(i) If any cracking is found during the inspection required by paragraph (g) or (h)(2) of this AD, prior to further flight, install a new fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used. After these actions are accomplished, no further action is required by this paragraph.

(j) If any corrosion is found during the inspection required by paragraph (g) or (h)(2) of this AD, prior to further flight, accomplish either paragraph (j)(1) or (j)(2) of this AD, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(1) Install a new fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph; or

(2) Blend out corrosion in accordance with the service bulletin.

(i) If blend out of corrosion is beyond 10 percent of original thickness or any crack is found during accomplishment of the blend out procedures, install a new fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph.

(ii) If blend out of corrosion does not exceed 10 percent of original material thickness, accomplish either paragraph (j)(2)(ii)(A) or (j)(2)(ii)(B) of this AD:

(A) Install a new fitting with new fasteners, and reinstall threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph; or

(B) Install the repaired fitting with new fasteners and reinstall the threshold assembly with corrosion-resistant fasteners, in accordance with the service bulletin. Thereafter, repeat the inspection and applicable corrective actions required by paragraph (g) of this AD at intervals not to exceed 6 years.

Inspections and Corrective Actions for Airplanes Equipped With MED 2, 4, and/or 5 (MED 2, 3, and/or 4 on Model 747SP Series Airplanes)

(k) For airplanes equipped with MED 2, 4, and/or 5 (MED 2, 3, and/or 4 on Model 747SP series airplanes): Prior to the accumulation of 10 years of service since date of manufacture of the airplane, or within 18 months after December 16, 1996, whichever occurs later, perform a detailed inspection to detect cracking and/or corrosion of the girt bar support fitting at the left and right MED 2, 4, and 5 (MED 2, 3, and 4 on Model 747SP series airplanes), in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(l) If no cracking or corrosion is found during the inspection required by paragraph (k) of this AD, prior to further flight, accomplish either paragraph (l)(1) or (l)(2) of this AD, in accordance with the applicable instructions in Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(1) Remove the inspected fitting and reinstall it with a new coat of primer and new fasteners; and reinstall the threshold assembly with new corrosion-resistant fasteners; in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph; or

(2) Reinstall the serrated plate assembly and the girt bar floor fitting with corrosion-resistant fasteners, in accordance with the service bulletin. Thereafter, repeat the inspection required by paragraph (k) of this AD at intervals not to exceed 6 years.

(m) If any cracking is found during the inspection required by paragraph (k) or (l)(2) of this AD, prior to further flight, install a new fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used. After these actions are accomplished, no further action is required by this paragraph.

(n) If any corrosion is found during the inspection required by paragraph (k) or (l)(2) of this AD, prior to further flight, accomplish either paragraph (n)(1) or (n)(2) of this AD, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(1) Install a new fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph; or

(2) Blend out corrosion in accordance with the service bulletin.

(i) If blend out of corrosion is beyond 10 percent of original thickness or any crack is found during accomplishment of the blend out procedures, install a new fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph.

(ii) If blend out of corrosion does not exceed 10 percent of original material thickness, install the repaired fitting with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph.

(o) For airplanes equipped with main entry door (MED) 3 (this paragraph does not apply to Model 747SP series airplanes): Prior to the accumulation of 16 years of service since date of manufacture of the airplane, or within 18 months after December 16, 1996, whichever occurs later, perform a detailed inspection to detect cracking and/or corrosion of the girt bar support angles at the left and right MED 3, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(p) If no cracking or corrosion is found during the inspection required by paragraph (o) of this AD, prior to further flight, accomplish either paragraph (p)(1) or (p)(2) of this AD in accordance with the applicable instructions in Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(1) Remove the inspected angle and reinstall it with a new coat of primer and new fasteners; and reinstall the threshold assembly with new corrosion-resistant fasteners; in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph; or

(2) Reinstall the corner scuff plate and the threshold apron with corrosion-resistant fasteners, in accordance with the service bulletin. Thereafter, repeat the inspection required by paragraph (o) of this AD at intervals not to exceed 6 years.

(q) If any crack common to the support angles is found during the inspection required by paragraph (o) or (p)(2) of this AD, prior to further flight, accomplish the actions specified in paragraph (q)(1) or (q)(2), as applicable, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used:

(1) Install the new angles with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners. After these actions are accomplished, no further action is required by this paragraph of this AD; or Start Printed Page 12140

(2) For any cracking found only in the corner casting as specified in the service bulletin, accomplish either paragraph (q)(2)(i) or (q)(2)(ii) prior to further flight:

(i) Replace the corner casting in accordance with the service bulletin; or

(ii) Repair the cracked part in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Refer to paragraph (w) of this AD for the appropriate procedure for seeking such an approval. (This option is provided in order to give operators time to obtain a replacement corner casing without grounding an airplane.) This repair is considered temporary action only; replacement of the corner casting eventually must be accomplished in accordance with a schedule prescribed by the Manager, Seattle ACO.

(r) If any corrosion is found during the inspection required by paragraph (o) of this AD, prior to further flight, accomplish either paragraph (r)(1) or (r)(2) of this AD, in accordance with Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005. After the effective date of this AD, only Revision 3 may be used.

(1) Install the new angles with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph; or

(2) Blend out corrosion in accordance with the service bulletin.

(i) If blend out of corrosion is beyond 10 percent of original thickness, or if any crack common to the support angles is found during accomplishment of the blend out procedures, install the new angles with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph.

(ii) If blend out of corrosion does not exceed 10 percent of original material thickness, install the repaired angles with new fasteners, and reinstall the threshold assembly with new corrosion-resistant fasteners, in accordance with the service bulletin. After these actions are accomplished, no further action is required by this paragraph.

Actions Accomplished According to Previous Issue of Service Bulletin

(s) Installation of a girt bar support fitting in accordance with Boeing Service Bulletin 747-25A2831, dated August 29, 1991, before the effective date of this AD, is considered acceptable for compliance with the corresponding requirements of paragraphs (h), (i), (j), (l), (m), and (n) of this AD for each affected fitting location.

New Requirements of This AD

Inspections for the Washers and Related Investigative/Corrective Actions

(t) For Groups 7, 8, and 9 airplanes identified in Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005, on which the support fitting was replaced or repaired in accordance with Boeing Service Bulletin 747-53A2378, dated June 24, 1993; Revision 1, dated March 10, 1994; or Revision 2, dated July 24, 2003; or Boeing Service Bulletin 747-25A2831, dated August 29, 1991: Within 18 months after the effective date of this AD, do a general visual inspection for correct installation of square and conical washers in the girt bar floor fittings, and, before further flight, do all applicable related investigative and corrective actions. Do all actions in accordance with Figure 18 and the applicable steps specified on page 52 of the Accomplishment Instructions of Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005, except as provided by paragraph (v) of this AD.

(u) For Groups 1 through 6 airplanes identified in Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005, on which the support fitting was replaced or repaired in accordance with Boeing Service Bulletin 747-53A2378, dated June 24, 1993; Revision 1, dated March 10, 1994; or Revision 2, dated July 24, 2003; or with Boeing Service Bulletin 747-25A2831, dated August 29, 1991: Within 18 months after the effective date of this AD, do a general visual inspection to determine if square and conical washers are installed in the girt bar floor fittings, and before further flight, do all applicable related investigative and corrective actions. Do all actions in accordance with Figure 18 and the applicable steps specified on pages 52 and 53 of the Accomplishment Instructions of Boeing Service Bulletin 747-53A2378, Revision 3, dated August 11, 2005, except as provided by paragraph (v) of this AD.

(v) If any damage is found during any inspection required by paragraphs (t) and (u) of this AD, and the bulletin specifies contacting Boeing for appropriate action: Before further flight, do the repair using a method approved by the Manager, Seattle ACO, FAA, or in accordance with data meeting the certification basis of the airplane approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane, and the approval must specifically refer to this AD.

Alternative Methods of Compliance (AMOCs)

(w)(1) The Manager, Seattle ACO, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

(3) AMOCs approved previously in accordance with AD 96-23-05, are approved as AMOCs for the corresponding provisions of this AD.

Start Signature

Issued in Renton, Washington, on March 7, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. E7-4738 Filed 3-14-07; 8:45 am]

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