E9-27632. Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-300, 747SR, and 747SP Series Airplanes

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 series airplanes. The existing AD currently requires repetitive inspections to detect cracking in certain fuselage skin lap joints, and repair if necessary. This proposed AD would expand the inspection area in the existing AD, add a modification of certain lap joints, and add certain post-repair inspections of the lap joints. Accomplishing the modification would end the repetitive inspections required by the existing AD for the length of lap joint that is modified. This proposed AD results from a structural review of affected skin lap joints for widespread fatigue damage. We are proposing this AD to prevent fatigue cracking in certain lap joints, which could result in rapid depressurization of the airplane.

DATES:

We must receive comments on this proposed AD by January 4, 2010.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, P.O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone [phone], extension 1, fax [phone]; e-mail [e-mail]; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221 or 425-227-1152.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov;​; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Ivan Li, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2009-1066; Directorate Identifier 2009-NM-028-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

On May 31, 1994, we issued AD 94-12-04, Amendment 39-8932 (59 FR 30277, June 13, 1994), for certain Boeing Model 747 series airplanes. That AD requires repetitive inspections to detect cracking in certain fuselage skin lap joints, and repair, if necessary. That AD was prompted by the results of extensive pressure fatigue tests conducted by the manufacturer. We issued that AD to detect and repair fatigue cracking in certain lap joints, which will ensure safe operation of airplanes that have exceeded their economic design goal.

Actions Since Existing AD Was Issued

Since we issued AD 94-12-04, the manufacturer has conducted a structural review of affected skin lap joints for widespread fatigue damage, and has identified additional inspection and modification requirements. It was determined that it is necessary to inspect lap joints with an upper skin thickness of 0.09 inch in addition to the areas inspected in accordance with the existing AD. For Model 747SP airplanes, the skin lap joints in Section 44 are also included in those inspections. It was determined that lap joints in Sections 41 and 42 with an upper skin thickness of 0.071 inch or less should be modified; and post-repair inspections are necessary.

Revised Service Information

We have reviewed Boeing Alert Service Bulletin 747-53A2367, Revision 2, dated October 30, 2008 (“Revision 2 of the service bulletin”); and Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009 (“Revision 3 of the service bulletin”). We referred to Boeing Service Bulletin 747-53-2367, dated December 18, 1991 (“the original issue of the service bulletin”); and Boeing Service Bulletin 747-53-2367, Revision 1, dated January 27, 1994 (“Revision 1 of the service bulletin”); as the appropriate sources of service information for accomplishing the actions required by AD 94-12-04.

Revisions 2 and 3 of the service bulletin retain the procedures described in the original issue of the service bulletin and Revision 1 of the service bulletin; however, those revisions add procedures for a new inspection area (Area 2) in Sections 41, 42, 44, and 46. Revisions 2 and 3 of the service bulletin also add procedures for a modification of the lap joints in Sections 41 and 42 for Groups 1, 2, 4, 5, and 7 through 10 airplanes. For airplanes on which any crack is found during the external surface high frequency eddy current (HFEC) inspection, the related investigative action is doing an open-hole HFEC inspection before further flight for further cracking; and for airplanes on which any crack is found, during that inspection, the corrective action is repairing the crack before further flight.

The compliance time for accomplishing the new Area 2 inspections is before the accumulation of 22,000 total flight cycles, or within 3,000 flight cycles after the last HFEC inspection of the area (as specified in the Boeing Model 747 Supplemental Structural Inspection Document), or within 1,000 flight cycles from the date on Revision 2 of the service bulletin, whichever occurs latest.

The compliance time for accomplishing the inspections in Section 41 at stringer 6 for Groups 2, 4, 8, and 9 airplanes not affected by Boeing Service Bulletin 747-53-2253 is within 10,000 flight cycles after doublers are installed per Boeing Service Bulletin 747-53-2272. These requirements are specified in AD 2008-10-15, Amendment 39-15522 (73 FR 29042, May 20, 2008).

For areas on which a lap joint repair was installed and the repair doubler is greater than or equal to 40 inches long, Revision 3 of the service bulletin describes procedures for repetitive internal surface HFEC inspections for cracks. The compliance time for accomplishing the initial inspection is within 15,000 flight cycles after the repair was installed.

Revision 3 of the service bulletin specifies repeating the applicable inspection at intervals not to exceed 3,000 flight cycles, or at intervals not to exceed 1,500 flight cycles for airplanes that have accumulated 30,000 total flight cycles or more. For Group 7, 8, and 9 airplanes, the inspections of the lap joints in Section 46 at stringer 4 left, between body stations 1720 and 1740, and between body stations 1960 and 1980, are repeated at intervals not to exceed 1,500 flight cycles.

For all airplanes, the compliance time for accomplishing the lap joint modification is before the accumulation of 30,000 total flight cycles, or within 3,000 flight cycles from the date of Revision 2 of the service bulletin, whichever is later. Accomplishing this modification eliminates the need for the repetitive inspections for the length of lap joint that is modified.

Revision 3 of the service bulletin also specifies that no lap joint modification instructions are included for Groups 3 and 6 airplanes and recommends contacting Boeing for modification instructions.

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 94-12-04 and would retain the requirements of the existing AD. This proposed AD would also require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the Proposed AD and Service Information.”

Differences Between the Proposed AD and Service Information

Revision 3 of the service bulletin specifies to contact the manufacturer for instructions on how to repair or modify certain conditions, but this proposed AD would require those conditions be done in one of the following ways:

• Using a method that we approve; or
• Using data that meet the certification basis of the airplane, and that have been approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

Revision 3 of the service bulletin recommends that the modification be done before the accumulation of 30,000 total flight cycles or within 3,000 flight cycles after the release date of Revision 2 of the service bulletin, “whichever is earlier.” However, the manufacturer has informed us that an error was made in that compliance time and it should specify “whichever occurs later.” The correct compliance time is specified in paragraph (j) of this AD.

Changes to Existing AD

This proposed AD would retain all requirements of AD 94-12-04. Since that AD 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 94-12-04	Corresponding requirement in this proposed AD
Paragraphs (a), (b), and (c)	Paragraph (g).

We have also revised paragraph (g)(2)(i) of this AD (paragraph (c)(1) of AD 94-12-04) to remove reference to Chapter 53-30-03 of the Boeing 747 Structural Repair Manual (SRM). Instead, that paragraph instructs operators to contact the FAA for repair instructions. We have also added a new Note 1 to specify that guidance on repairing any subject cracking can be found in Chapter 53-30-03 of the Boeing 747 SRM.

Costs of Compliance

There are about 209 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 69 airplanes of U.S. registry.

The actions that are required by AD 94-12-04 and retained in this proposed AD take about 14 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the currently required actions is $1,120 per airplane, per inspection cycle.

The new proposed Area 2 inspections would take about 477 work hours per airplane, depending on airplane configuration, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the new actions specified in this proposed AD for U.S. operators is between $38,160 and $2,633,040, or between $2,400 and $3,840 per airplane, per inspection cycle.

The new proposed modification would take about 171 work hours per airplane, at an average labor rate of $80 per work hour. Required parts cost per airplane would be minimal. Based on these figures, the estimated cost of the new actions specified in this proposed AD for U.S. operators is $943,920, or $13,680, per airplane.

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.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 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. The FAA amends § 39.13 by removing Amendment 39-8932 (59 FR 30277, June 13, 1994) and adding the following new AD:

Boeing: Docket No. FAA-2009-1066; Directorate Identifier 2009-NM-028-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 4, 2010.

Affected ADs

(b) This AD supersedes AD 94-12-04, Amendment 39-8932.

Applicability

(c) This AD applies Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-300, 747SR, and 747SP series airplanes, certificated in any category, as identified in Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009.

Subject

(d) Air Transport Association (ATA) of America Code 53: Fuselage.

Unsafe Condition

(e) This AD results from a structural review of affected skin lap joints for widespread fatigue damage. The Federal Aviation Administration is issuing this AD to prevent fatigue cracking in certain lap joints which could result in rapid depressurization of the airplane.

Compliance

(f) 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 94-12-04, With Revised Service Information

Repetitive Inspections

(g) For airplanes identified in Boeing Service Bulletin 747-53-2367, dated December 18, 1991: Prior to the accumulation of 22,000 full pressure flight cycles (or, if the external skin panel of an affected lap joint has been replaced, prior to the accumulation of 22,000 full pressure flight cycles since skin replacement), or within 1,000 landings after July 13, 1994 (the effective date of AD 94-12-04), whichever occurs later, perform an external surface high frequency eddy current (HFEC) inspection of the skin around the upper row of fasteners, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53-2367, dated December 18, 1991; Revision 1, dated January 27, 1994; Boeing Alert Service Bulletin 747-53A2367, Revision 2, dated October 30, 2008; or Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009. As of the effective date of this AD, only Revision 3 of the service bulletin may be used.

(1) If no crack is found, repeat the inspection thereafter at intervals not to exceed 3,000 full pressure flight cycles until the inspections required by paragraph (h) of this AD are done.

(2) If any crack is found, accomplish paragraphs (g)(2)(i) and (g)(2)(ii) of this AD.

(i) Prior to further flight, perform an open hole HFEC inspection to detect cracking in the upper row fastener holes between the adjacent frames, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53-2367, dated December 18, 1991; Revision 1, dated January 27, 1994; Boeing Alert Service Bulletin 747-53A2367, Revision 2, dated October 30, 2008; or Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009. Prior to further flight, repair any crack found, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA.

Note 1:

Guidance on repairing cracking can be found in Chapter 53-30-03 of the Boeing 747 Structural Repair Manual.

(ii) Repeat the inspection required by paragraph (g) of this AD thereafter at intervals not to exceed 3,000 full pressure flight cycles until the inspections required by paragraph (h) of this AD are done.

New Requirements of This AD

Repetitive Inspections/Investigative and Corrective Actions

(h) For all airplanes: Do initial and repetitive HFEC inspections for cracks of lap joints in Sections 41, 42, 44, and 46, by doing all the actions, including all applicable related investigative and corrective actions, specified in the Accomplishment Instructions of Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009, except as provided by paragraph (l) of this AD. Do the inspections at the applicable times specified in paragraph 1.E. of Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009, except as required by paragraph (k) of this AD. Do all applicable related investigative and corrective actions before further flight. Accomplishing the inspections required by this paragraph ends the repetitive inspections required by paragraph (g) of this AD. Do the actions required by paragraph (h) of this AD until the modification required by paragraph (j) of this AD is done.

(i) For areas on which a lap joint repair was installed and the repair doubler is greater than or equal to 40 inches long: Do initial and repetitive internal HFEC inspections for cracks, as required by paragraph (h) of this AD, by doing all the applicable actions, including applicable corrective actions, specified in the Accomplishment Instructions of Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009, except as provided by paragraph (l) of this AD. Do the inspection and corrective actions at the times specified in paragraph 1.E. of Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009, except as required by paragraph (k) of this AD.

Terminating Action

(j) Before the accumulation of 30,000 total flight cycles or within 3,000 flight cycles after the effective date of this AD, whichever occurs later: Modify the applicable lap joints in Sections 41 and 42 by doing all the actions specified in the Accomplishment Instructions of Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009, except as required by paragraph (l) of this AD. Accomplishing this modification terminates the repetitive inspection requirements of this AD for the length of lap joint that is modified.

Exceptions to Boeing Service Bulletin 747-53A2367, Revision 3

(k) Where Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009, specifies compliance times “from the date on the original issue of this service bulletin [12/18/91],” and “from the date on Revision 2 of this service bulletin [10/30/08],” this AD requires compliance within the specified compliance time after the effective date of this AD.

(l) Where Boeing Service Bulletin 747-53A2367, Revision 3, dated January 15, 2009, specifies to contact Boeing for repair or modification instructions: Before further flight, repair or modify using a method approved in accordance with the procedures specified in paragraph (m) of this AD.

Alternative Methods of Compliance (AMOCs)

(m)(1) The Manager, Seattle ACO, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Ivan Li, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]. Or, e-mail information to [e-mail].

(2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your principal maintenance inspector (PMI) or principal avionics inspector (PAI), as appropriate, or lacking a principal inspector, your local Flight Standards District Office. The AMOC approval letter must specifically reference this AD.

(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization 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.

(4) AMOCs approved previously in accordance with AD 94-12-04 are approved as alternative methods of compliance with the corresponding requirements of this AD.

Issued in Renton, Washington, on November 6, 2009.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.