E8-23824. Airworthiness Directives; Boeing Model 747 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 airplanes. The existing AD currently requires repetitive inspections to detect evidence of wear damage in the area at the interface between the vertical stabilizer seal and fuselage skin, and corrective actions, if necessary. The existing AD also provides for an optional terminating action for the repetitive inspections. For all airplanes, this proposed AD would require doing repetitive inspections for wear damage and cracks of the fuselage skin in the interface area of the vertical stabilizer seal and fuselage skin, doing a detailed inspection for wear damage and cracks of the surface of any skin repair doubler in the area, and doing corrective actions. For airplanes on which the fuselage skin has been blended to remove wear damage, this proposed AD would require doing repetitive external detailed inspections or high frequency eddy current inspections for cracks of the blended area of the fuselage skin, and corrective actions if necessary. This proposed AD results from reports of wear damage on airplanes with fewer than 8,000 total flight cycles. In addition, there have been three reports of skin wear damage on airplanes that applied BMS 10-86 Teflon-filled coating (terminating action per AD 2002-26-15). We are issuing this AD to detect and correct wear damage and cracks of the fuselage skin in the interface area of the vertical stabilizer seal and fuselage skin in sections 46 and 48, which could cause in-flight depressurization of the airplane.

DATES:

We must receive comments on this proposed AD by November 24, 2008.

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 AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

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-2008-1071; Directorate Identifier 2008-NM-093-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 December 24, 2002, we issued AD 2002-26-15, amendment 39-13003 (68 FR 476, January 6, 2003), for certain Boeing Model 747 series airplanes. That AD requires repetitive inspections to detect evidence of skin wear damage in the interface area of the vertical stabilizer seal and fuselage skin, and corrective actions, if necessary. The existing AD also provides for an optional terminating action for the repetitive inspections. That AD resulted from reports of wear damage at the interface area of the vertical stabilizer seal and fuselage skin in sections 46 and 48. We issued that AD to detect and correct wear damage of the fuselage skin, which could result in thinning and cracking of the fuselage skin, and consequent in-flight depressurization of the airplane.

Actions Since Existing AD Was Issued

Since we issued AD 2002-26-15, we have received several reports of skin wear damage on airplanes with less than 8,000 total flight cycles. As a result, Boeing has revised the initial inspection threshold of the repetitive inspections to 20,000 total flight hours. In addition, there have been three reports of skin wear damage on airplanes that have received the Boeing Material Specifications (BMS) 10-86 Teflon-filled coating application (terminating action per AD 2002-26-15). We have concluded that the one-time Teflon-filled coating application does not provide the necessary skin wear resistance; therefore, the terminating action no longer terminates the repetitive inspections. The requirements of 2002-26-15 do not adequately address the identified unsafe condition of that AD.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-53A2478, Revision 1, dated March 27, 2008. The service bulletin describes the following procedures:

• For all airplanes: Do repetitive external inspections for wear damage and cracks of the fuselage skin at the interface area of the vertical stabilizer seal and fuselage skin, and do a detailed inspection for wear damage and cracks of the surface of any repair doubler installed in the area.
• For airplanes on which the fuselage skin has been blended to remove wear damage: Do repetitive external detailed inspections or high frequency eddy current inspections for cracks of the blended area of the fuselage skin.
• If no wear damage or crack is found: Before further flight, apply BMS 10-86 Teflon-filled coating.
• If any wear damage or crack is found: Before further flight, measure the depth of the wear and location, repair any wear damage and crack, and apply BMS 10-86 Teflon-filled coating.

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 2002-26-15. This proposed AD would retain the requirements of that AD and also require accomplishing the actions described previously, except as discussed under “Differences Between the Proposed AD and the Service Bulletin.”

Differences Between the Proposed AD and Service Bulletin

The service bulletin specifies to contact the manufacturer for actions if corrosion resistant steel rubstrips are installed in the interface area of the vertical stabilizer seal and fuselage skin, but this proposed AD would require contacting the FAA for inspections using a method that we approve.

Costs of Compliance

There are about 917 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 2002-26-15)	12	$80	None	$960, per inspection cycle	253	$242,880, per inspection cycle.
Inspection and application of BMS 10-86 Teflon-filled coating (new proposed action)	8	80	None	$640, per inspection cycle	165	$105,600, 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
• 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 Federal Aviation Administration (FAA) amends § 39.13 by removing amendment 39-13003 (68 FR 476, January 6, 2003) and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2008-1071; Directorate Identifier 2008-NM-093-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by November 24, 2008.

Affected ADs

(b) This AD supersedes AD 2002-26-15.

Applicability

(c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-53A2478, Revision 1, dated March 27, 2008.

Unsafe Condition

(d) This AD results from reports of skin wear damage on airplanes with fewer than 8,000 total flight cycles. In addition, there have been three reports of skin wear damage on airplanes on which BMS 10-86 Teflon-filled coating was applied (terminating action per AD 2002-26-15). We are issuing this AD to detect and correct wear damage and cracks of the fuselage skin in the interface area of the vertical stabilizer seal and fuselage skin in sections 46 and 48, which could cause in-flight depressurization of the airplane.

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.

Requirements of AD 2002-26-15

Inspections for Damage/Corrective Actions

(f) For airplanes identified in Boeing Alert Service Bulletin 747-53A2478, dated February 7, 2002: Prior to the accumulation of 15,000 total flight cycles, or within 1,200 flight cycles after February 10, 2003 (the effective date of AD 2002-26-15), whichever occurs later, perform a detailed inspection to detect evidence of wear damage of the fuselage skin at the interface area of the vertical stabilizer seal and fuselage skin, per the service bulletin.

(1) If no wear damage of the fuselage skin is detected or any existing blendout is within the structural repair manual (SRM) allowable damage limits: Repeat the detailed inspection at intervals not to exceed 6,000 flight cycles.

(2) If any wear damage of the fuselage skin is detected or any existing blendout exceeds the allowable damage limits specified in the SRM: Before further flight, repair the vertical stabilizer seal interface and refinish the skin with BMS 10-86 Teflon-filled coating, per the alert service bulletin. Accomplishment of the repair and refinishing is terminating action for the repetitive inspections required by paragraph (f)(1) of this AD.

Note 1:

For the purposes of this AD, a detailed inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

Previously Accomplished Inspections and Terminating Action

(g) For airplanes identified in Boeing Alert Service Bulletin 747-53A2478, dated February 7, 2002: Inspections and terminating action done before February 10, 2003, per Boeing Service Bulletin 747-53-2192, dated July 21, 1981, are acceptable for compliance with the corresponding actions required by paragraph (f) of this AD, provided BMS 10-86 Teflon-filled coating was used, and the new allowable damage limits specified in Boeing Alert Service Bulletin 747-53A2478, dated February 7, 2002, are met.

New Requirements of This AD

New Service Bulletin Revision

(h) The term “service bulletin,” as used in paragraphs (i) through (l) of this AD, means Boeing Alert Service Bulletin 747-53A2478, Revision 1, dated March 27, 2008, unless otherwise specified.

New Repetitive Inspections

(i) Except as provided by paragraph (j) of this AD: At the applicable times specified in Table 1 of this AD, do the actions specified in paragraphs (i)(1) and (i)(2) of this AD, as applicable. Accomplishing the initial inspection specified in paragraph (i) terminates the requirements of paragraph (f) of this AD.

(1) For all airplanes: Do the actions specified in paragraphs (i)(1)(i) and (i)(1)(ii) of this AD, as applicable.

(i) Do repetitive external detailed inspections for wear damage and cracks of the fuselage skin in the interface area of the vertical stabilizer seal and fuselage skin, in accordance with the Accomplishment Instructions of the service bulletin.

(ii) Where a skin repair doubler is present in the interface area of the vertical stabilizer seal and fuselage skin, do a detailed inspection for wear damage and cracks of the surface of the repair doubler.

(2) For airplanes that have reduced skin thickness in Section 46 due to blending without reinforcement: Do repetitive external detailed inspections or high frequency eddy (HFEC) current inspections for cracks of the blended area of the fuselage skin, in accordance with the Accomplishment Instructions of the service bulletin.

Table 1—Compliance Times

Action	Compliance time (whichever occurs later)		Repeat interval (not to exceed)
	Threshold	Grace period
For actions required by paragraph (i)(1) of this AD	Prior to the accumulation of 20,000 total flight hours since the date of issuance of the original airworthiness certificate or the date of issuance of the original export certificate of airworthiness, or within 7,500 flight hours after the last inspection of this AD, whichever occurs later	Within 6,000 flight hours after the effective date of this AD	7,500 flight hours.
For actions required by paragraph (i)(2) of this AD	Prior to the accumulation of 20,000 total flight cycles since the date of issuance of the original airworthiness certificate or the date of issuance of the original export certificate of airworthiness, or within 6,000 flight cycles after the initial blend, whichever occurs later	Within 1,000 flight cycles after the effective date of this AD	1,200 flight cycles for external detailed inspection, or 6,000 flight cycles for HFEC inspection.

Exception to the Repetitive Inspections

(j) If corrosion-resistant steel rubstrips are installed in the interface area of the vertical stabilizer seal and fuselage skin: Within the applicable compliance times specified in paragraph (i) of this AD, inspect the fuselage skin using a method approved in accordance with the procedures specified in paragraph (m) of this AD.

For No Wear Damage or Cracks Found: Apply Teflon

(k) If no wear damage or crack is found in the fuselage skin during any inspection required by paragraph (i) of this AD: Before further flight, apply Boeing Material Specifications (BMS) 10-86 Teflon-filled coating in accordance with the Accomplishment Instructions of the service bulletin.

For Any Wear Damage or Crack Found: Applicable Corrective Actions

(l) If any wear damage or crack is found in the fuselage skin during any inspections required by paragraph (i) of this AD: Before further flight, after the inspection required by paragraph (i), do the actions specified in paragraphs (l)(1), (l)(2), and (l)(3) of this AD, in accordance with the Accomplishment Instructions of the service bulletin.

(1) Measure the depth of the wear and record the location.

(2) Repair any wear damage and any crack.

(3) Apply BMS 10-86 Teflon-filled coating.

Alternative Methods of Compliance (AMOCs)

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

(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 appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.

(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.

Issued in Renton, Washington, on September 26, 2008.

Michael Kaszycki,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.