2010-15054. Airworthiness Directives; The Boeing Company Model 747-100, 747-200B, and 747-200F Series Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede two existing airworthiness directives (AD) that apply to certain Model 747-100, 747-200B, and 747-200F series airplanes. The existing ADs currently require inspections to detect fatigue-related skin cracks and corrosion of the skin panel lap joints in the fuselage upper lobe, and repair if necessary. One of the existing ADs, AD 94-12-09, also requires modification of certain lap joints and inspection of modified lap joints. The other AD, AD 90-15-06, requires repetitive detailed external visual inspections of the fuselage skin at the upper lobe skin lap joints for cracks and evidence of corrosion, and related investigative and corrective actions. This proposed AD would reduce the maximum interval of the post-modification inspections, and adds post-repair inspection requirements for certain airplanes. This proposed AD results from reports of cracking on modified airplanes. We are proposing this AD to detect and correct fatigue cracking and corrosion in the fuselage upper lobe skin lap joints, which could lead to rapid decompression of the airplane and inability of the structure to carry fail-safe loads.

DATES:

We must receive comments on this proposed AD by August 6, 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-2010-0552; Directorate Identifier 2009-NM-095-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 July 3, 1990, we issued AD 90-15-06, Amendment 39-6653 (55 FR 28600, July 12, 1990), for certain Boeing Model 747-100, 747-200B, and 747-200F series airplanes. That AD requires repetitive detailed external visual inspections of the fuselage skin at the upper lobe skin lap joints for cracks and evidence of corrosion, and related investigative and corrective actions. We issued that AD to detect and correct fatigue cracking and corrosion in the fuselage skins, which could lead to rapid decompression of the airplane and inability of the structure to carry fail-safe loads.

On June 2, 1994, we issued AD 94-12-09, Amendment 39-8937 (59 FR 30285, June 13, 1994), for certain Boeing Model 747-100, 747-200B, and 747-200F series airplanes. That AD requires inspections to detect fatigue cracking and corrosion of the skin panel lap joints in the fuselage upper lobe, and repair if necessary. That AD also requires modification of certain lap joints and inspections of modified lap joints. That AD resulted from reports of cracking, corrosion, and bulging of the skin lap joints on Boeing Model 747-100, 747-200B, and 747-200F series airplanes. We issued that AD to prevent rapid decompression of the airplane and the inability of the structure to carry fail-safe loads.

Actions Since Existing AD Was Issued

Since we issued AD 94-12-09 and AD 90-15-06, Boeing has performed a fleet-wide evaluation of the skin panel lap joints for widespread fatigue damage (WFD) and determined that the post-modification inspection interval of AD 94-12-09 needs to be reduced. In addition, lap joints where the upper (overlapping) skin thickness at the upper row of fasteners is 0.071 inch or less need to be further modified to preclude WFD. WFD of the lap joints can link up and result in large skin cracks, and possible rapid in-flight decompression of the airplane.

Related Rulemaking

We are considering issuing related rulemaking to address the identified unsafe condition. The related rulemaking would refer to Revision 1, dated April 16, 2009, of Boeing Service Bulletin 747-53A2463, which is related to this unsafe condition. That AD would require further modification of all the affected lap joints with an upper skin thickness of 0.071 inch or less. Once the modification in accordance with Boeing Service Bulletin 747-53A2463 is accomplished, the post-modification inspections will be accomplished in accordance with that rule, not this one.

Relevant Service Information

AD 90-15-06 refers to Boeing Service Bulletin 747-53-2307, dated December 21, 1989, as the appropriate source of service information for the required actions specified in that AD. AD 94-12-09 refers to Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993, as the appropriate source of service information for the required actions specified in that AD. We have reviewed Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009. Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009, reduces the maximum post-modification inspection interval specified in Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993, from 3,000 to 1,000 flight cycles and references a structural modification for lap joints where the upper (overlapping) skin thickness at the upper row of fasteners is 0.071 inch or less. In addition, Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009, specifies a post-repair internal surface high frequency eddy current (HFEC) inspection of the skin at any external doubler repairs greater than 40 inches in length (in the horizontal direction).

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 90-15-06 and AD 94-12-09. This proposed AD does not retain any requirements of AD 90-15-06. This proposed AD would retain the inspection requirements of AD 94-12-09 but with reduced maximum intervals of the post-modification inspections from 3,000 flight cycles to 1,000 flight cycles. In addition, this proposed AD would require a post-repair internal surface HFEC inspection of the skin at any external doubler repairs greater than 40 inches in length (in the horizontal direction). This proposed AD would also require accomplishing the actions specified in Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009, described previously, except as discussed under “Differences Between the Proposed AD and Service Bulletin.”

Differences Between the Proposed AD and Service Bulletin

Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009, specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repairing those conditions 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 the Boeing Commercial Airplanes Organization Designation Authorization that we have authorized to make those findings.

Change to Existing AD

This proposed AD would retain the requirements of AD 94-12-09, and none of the requirements of AD 90-15-06. Since AD 94-12-09 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 94-12-09	Corresponding requirement in this proposed AD
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).

Costs of Compliance

There are about 23 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.

Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Inspection (required by AD 94-12-09)	208	$85	$0	$17,680 per inspection cycle	7	$123,760 per inspection cycle.
Modification (required by AD 94-12-09)	8,160	85	0	$693,600	7	$4,855,200.
Post-Modification Inspection (required by AD 94-12-09)	56	85	0	$4,760 per inspection cycle	7	$33,320 per inspection cycle.

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 39-6653 (55 FR 28600, July 12, 1990), and Amendment 39-8937 (59 FR 30285, June 13, 1994), and adding the following new AD:

The Boeing Company: Docket No. FAA-2010-0552; Directorate Identifier 2009-NM-095-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by August 6, 2010.

Affected ADs

(b) This AD supersedes AD 90-15-06, Amendment 39-6653; and AD 94-12-09, Amendment 39-8937.

Applicability

(c) This AD applies to The Boeing Company Model 747-100, 747-200B, and 747-200F series airplanes, certificated in any category, as identified in Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009.

Subject

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

Unsafe Condition

(e) This AD results from reports of fatigue cracking. The Federal Aviation Administration is issuing this AD to detect and correct fatigue cracking and corrosion in the fuselage upper lobe skin panel lap joints, which could lead to the rapid decompression of the airplane and the inability to carry fail-safe loads.

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 94-12-09, With Revised Service Information

Inspection

(g) Within 1,000 flight cycles after July 13, 1994 (the effective date of AD 94-12-09), and thereafter at the intervals specified in paragraphs (g)(1), (g)(2), and (g)(3) of this AD, perform inspections at the upper lobe skin panel lap joints in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used.

(1) Perform a detailed external visual inspection to detect cracks and evidence of corrosion (bulging skin between fasteners, blistered paint, dished fasteners, popped rivet heads, or loose fasteners) in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used. Repeat that inspection thereafter at intervals not to exceed 2,000 flight cycles until the modification required by paragraph (k) of this AD is accomplished.

(2) Perform a high frequency eddy current (HFEC) inspection to detect cracks in the skin at the upper row of fasteners of the skin panel lap joints forward of body station (BS) 1000 in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used. Repeat that inspection thereafter at intervals not to exceed 4,000 flight cycles until the modification required by paragraph (k) of this AD is accomplished.

(3) Perform a HFEC inspection to detect cracks in the skin at the upper row of fastener holes of the skin panel lap joints aft of BS 1480 to 2360 in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used. Repeat that inspection thereafter at intervals not to exceed 6,000 flight cycles until the modification required by paragraph (k) of this AD is accomplished.

(h) If any crack is found during any inspection required by paragraph (g) or (l) of this AD, or if any corrosion is found for which material loss exceeds 10 percent of the material thickness, accomplish paragraphs (h)(1) and (h)(2) of this AD in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, use only Revision 3.

(1) Prior to further flight, repair any crack or corrosion found, in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used.

(2) Within 18 months after accomplishing the repair, accomplish the “full” modification described in Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009; for the remainder of any skin panel lap joint in which a crack is found, or in which corrosion is found that exceeds 10 percent of the material thickness, in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used.

(i) If no crack is found during any inspection required by paragraph (g) of this AD, but corrosion is found for which the material loss does not exceed 10 percent of the material thickness: Accomplish the actions specified in paragraphs (i)(1) and (i)(2) of this AD for the entire affected skin panel lap joint, in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used.

(1) Within 500 flight cycles after accomplishing the inspection during which the corrosion was found, and thereafter at intervals not to exceed 500 flight cycles until the “full” modification required by paragraph (i)(2) of this AD is accomplished: Perform a HFEC inspection to detect cracks of the corroded skin panel lap joint, in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used.

(2) Within 36 months after accomplishing the inspection during which the corrosion was found: Accomplish the “full” modification, in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, only Revision 3 may be used.

(j) The inspections required by paragraph (g) of this AD shall be performed by removing the paint and using an approved chemical stripper; or by ensuring that each fastener head is clearly visible.

(k) Except as provided in paragraph (m) of this AD, prior to the accumulation of 20,000 total flight cycles, or within the next 1,000 flight cycles after July 13, 1994, whichever occurs later: Accomplish the modification described in Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009; as a “full” modification of the skin panel lap joints at the locations specified in paragraphs (k)(1) and (k)(2) of this AD, as applicable, in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. After the effective date of this AD, use only Revision 3. Accomplishment of this modification terminates the repetitive inspection requirements of paragraph (g) of this AD.

(1) For airplane line numbers 001 through 058, inclusive: Modify the skin panel lap joints at Stringer 12 (left and right), station 520 to 1,000; and Stringer 19 (left and right), station 520 to 740.

(2) For airplane line numbers 59 through 200, inclusive: Modify the skin panel lap joints at Stringer 12 (left and right), station 740 to 1,000; and Stringer 19 (left and right), station 520 to 740.

(l) For all airplanes: Perform an external HFEC inspection to detect skin cracks of any modified skin panel lap joints at the times specified in paragraphs (1)(1), (1)(2), and (1)(3) of this AD, as applicable, in accordance with Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009. As of the effective date of this AD, only Revision 3 may be used. Repeat that inspection thereafter at intervals not to exceed 3,000 flight cycles, except as required by paragraph (n) of this AD.

(1) For skin panel lap joints on which the “full” modification has been accomplished: Within 10,000 flight cycles after accomplishment of that modification.

(2) For skin panel lap joints on which the “optional” (partial) modification has been accomplished: Within 7,000 flight cycles after accomplishment of that modification.

(3) For skin panel lap joints having deep countersink fasteners located at Section 42 on which the “full” modification, as described in Boeing Service Bulletin 747-53-2307, dated December 21, 1989, has been accomplished: Within 5,000 flight cycles after accomplishment of that modification.

(m) In lieu of the “full” modification required by paragraph (k) of this AD, the “optional” (partial) modification described in Boeing Service Bulletin 747-53-2307, Revision 2, dated October 14, 1993; or Revision 3, dated April 16, 2009; may be accomplished for skin panels that have an outer thickness of 0.090 inches or less, and that do not have any cracks, corrosion, or an existing structural repair on the skin panel lap joint. After the effective date of this AD, only Revision 3 may be used. The “optional” (partial) modification shall not be accomplished at deep countersink fastener locations. Accomplishment of this modification terminates the repetitive inspection requirements of paragraph (g) of this AD.

New Requirements of This AD

Post-Modification Inspection at Reduced Intervals

(n) Repeat the inspection required by paragraph (l) of this AD at the earlier of the times specified in paragraphs (n)(1) and (n)(2) of this AD. Thereafter, repeat the inspection at intervals not to exceed 1,000 flight cycles.

(1) Within 3,000 flight cycles after the last inspection done in accordance with paragraph (l) of this AD.

(2) Within 1,000 flight cycles after the last inspection done in accordance with paragraph (l) of this AD or 500 flight cycles after the effective date of this AD, whichever occurs later.

Post-Repair Inspection for External Doubler Repair

(o) For all airplanes: Do an internal surface HFEC inspection for cracking of the skin at any external doubler repairs greater than 40 inches in length (in the horizontal direction) within 1,000 flight cycles after the effective date of this AD, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009. Thereafter, perform that inspection at intervals not to exceed 3,000 flight cycles.

(p) If any cracking is found during any inspection required by paragraph (o) of this AD, repair in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-53-2307, Revision 3, dated April 16, 2009.

Alternative Methods of Compliance (AMOCs)

(q)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, 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 Aircraft Certification Office, 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 Organization Designation 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.

(4) AMOCs approved previously in accordance with AD 90-15-06, Amendment 39-6653; and AD 94-12-09, Amendment 39-8937; are approved as AMOCs for the corresponding provisions of this AD.

Issued in Renton, Washington, on June 16, 2010.

Robert D. Breneman,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.