E8-9122. Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, and 747SR 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 for cracking and corrosion of all exposed surfaces of the carriage spindles (including the inner bore and aft links) of the trailing edge flaps, and additional inspection and corrective action if necessary. The existing AD also requires repetitive overhaul of the carriage spindle and aft link, which terminates the repetitive inspections. This proposed AD would add a repetitive inspection to detect broken parts, and revise the overhaul threshold and repetitive intervals. This proposed AD results from analysis that showed additional inspections should be done to prevent the loss of a flap, and that the flight-hour-based interval should be revised to a flight-cycle-based interval, because the greatest loads on the spindles happen during takeoff and landing. We are proposing this AD to detect and correct failed carriage spindles or aft links for the inboard or outboard trailing edge flaps. Such failure could cause the flap to depart the airplane, reducing the flightcrew's ability to maintain the safe flight and landing of the airplane.

DATES:

We must receive comments on this proposed AD by June 12, 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:

Gary Oltman, 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-2008-0414; Directorate Identifier 2007-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 August 6, 1990, we issued AD 90-17-19, amendment 39-6705 (55 FR 33280, August 15, 1990), for all Boeing Model 747 series airplanes, except the Model 747SP. That AD requires repetitive inspections for cracking and corrosion of all exposed surfaces of the carriage spindles (including the inner bore and aft links) of the trailing edge flaps, and additional inspection and corrective action if necessary. The existing AD also requires repetitive overhaul of the carriage spindle and aft link, which terminates the repetitive inspections. That AD resulted from a report of failure of two aft links in the spindles on one flap, causing control problems during approach and landing. We issued that AD to prevent failure of the trailing edge flaps' carriage spindles, which could result in reduced controllability of the airplane.

Actions Since Existing AD Was Issued

Since we issued AD 90-17-19, the manufacturer conducted a dynamic aerodynamic analysis, which showed that the airplane might not have sufficient roll authority to overcome loss of lift caused by a departure of a single left- or right-hand inboard or outboard trailing edge flap. The manufacturer then conducted a structural analysis of the flap attach structure and fail-safe components, which showed that additional inspections should be done to prevent the loss of a flap, and that the flight-hour-based interval required by AD 90-17-19 should be revised to a flight-cycle-based interval because the greatest loads on the spindles happen during takeoff and landing and not during flight.

Relevant Service Information

We have reviewed Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 2008. We referred to Boeing Service Bulletin 747-27-2280, Revision 3, dated November 30, 1989, as the appropriate source of service information for accomplishing the actions required by AD 90-17-19. Revision 6 adds a repetitive inspection of all eight carriage spindles and aft links to detect a broken carriage spindle or aft link, and corrective action if necessary. The remaining procedures in Revision 6 of the service bulletin are unchanged from Revision 3 of the service bulletin. The corrective action is replacing the broken part before further flight.

Revision 6 of the service bulletin also revises the overhaul threshold and the repetitive overhaul interval as follows (AD 90-17-19 required the repetitive overhaul):

• The initial overhaul threshold is the earlier of 8 years or a specified number of flight cycles. The number of flight cycles is either 6,000 or 9,000, depending on the airplane group specified in the service bulletin and the type and location of carriage originally installed.
• The repetitive overhaul interval is also the earlier of 8 years or the same specified number of flight cycles based on the same variables.

We have also reviewed Boeing Service Bulletin 747-27-2371, dated December 20, 2000, which applies only to Group 1 and Group 3 airplanes identified in Boeing Service Bulletin 747-27-2280, Revision 6. Boeing Service Bulletin 747-27-2371 describes procedures for replacing the link assemblies with new link assemblies made from improved corrosion-resistant steel (CRES) that has a bearing race that is machined into the link. Doing this replacement eliminates the need for the repetitive overhauls specified in Boeing Service Bulletin 747-27-2280, Revision 6, for that aft link only.

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 90-17-19 and would retain certain requirements of the existing AD at revised intervals. This proposed AD would also require a repetitive inspection to detect a broken carriage spindle or broken aft link, and corrective action if necessary. The proposed AD would also include, for certain airplanes, procedures for replacing the link assemblies with new link assemblies made from improved CRES that has a bearing race that is machined into the link, which would end the need for the repetitive overhauls specified in Boeing Service Bulletin 747-27-2280, Revision 6, for that aft link only.

Changes to Existing AD

This proposed AD would retain certain requirements of AD 90-17-19. Since AD 90-17-19 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 90-17-19	Corresponding requirement in this proposed AD
paragraph A.	paragraph (f).
paragraph A.1.	paragraph (f).
paragraph A.2.	paragraph (f)(1).
paragraph A.3.	paragraph (f)(2).
paragraph A.4.	paragraph (f)(3).
paragraph A.5.	paragraph (f)(4).
paragraph B.	paragraph (g).

We have revised paragraph A.5. of AD 90-17-19 (paragraph (f)(4) of this proposed AD) to allow any part of both carriage spindle/aft link assemblies to be repaired according to data that conform to the airplane's type certificate and that are approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make such findings.

In this proposed AD, the “detailed visual inspection” specified in AD 90-17-19 is referred to as a “detailed inspection.” We have included the definition for a detailed inspection in Note 1 of the proposed AD. We have also included the definition of a general visual inspection in Note 2 of this AD. That definition was not included in AD 90-17-19.

Costs of Compliance

There are about 925 airplanes of the affected design in the worldwide fleet, which includes 160 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD. The average labor rate is $80 per work hour.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Fleet cost
Inspection and overhaul (required by AD 90-17-19)	Between 120 and 140, per flap per cycle	$0	Between $9,600 and $11,200, per flap per overhaul cycle	Between $1,536,000 and $1,792,000, per flap per cycle.
Repetitive inspection for broken parts (new proposed action)	2, per inspection cycle	0	$160, per inspection cycle	$25,600, 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 39-6705 (55 FR 33280, August 15, 1990) and adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2008-0414; Directorate Identifier 2007-NM-095-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by June 12, 2008.

Affected ADs

(b) This AD supersedes AD 90-17-19.

Applicability

(c) This AD applies to all Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, and 747SR series airplanes, certificated in any category.

Unsafe Condition

(d) This AD results from analysis that showed that additional inspections should be done to prevent the loss of a flap, and that the flight-hour-based interval should be revised to a flight-cycle-based interval, because the greatest loads on the spindles happen during takeoff and landing. We are issuing this AD to detect and correct failed carriage spindles or aft links for the inboard or outboard trailing edge flaps. Such failure could cause the flap to depart the airplane, reducing the flightcrew's ability to maintain the safe flight and landing 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 90-17-19

Repetitive Inspections

(f) For all airplanes except those airplanes on which the repetitive overhauls required by paragraph B. of AD 90-17-19 are being accomplished as of the effective date of this AD: Prior to the accumulation of 30,000 flight hours or 8 years on each new or previously overhauled flap carriage spindle, whichever occurs first, remove the aft link and thrust collars from the trailing edge flaps' carriage spindles and perform a detailed inspection of all exposed surfaces of the carriage spindles, including inner bore, and aft links to detect cracking and corrosion, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27-2280, Revision 3, dated November 30, 1989.

Note 1:

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

(1) If no cracking or corrosion is found, repeat the inspections required by paragraph (f) of this AD at intervals not to exceed 12 months until the carriage spindles are overhauled in accordance with paragraph (g) of this AD.

(2) If a cracked carriage spindle or aft link is found, prior to further flight, replace the part(s) in accordance with the service bulletin.

(3) If corrosion is found on any part of the carriage spindle/aft link assembly, but not on the other assembly on the same flap, perform a repetitive general visual inspection in accordance with the service bulletin at intervals not to exceed 2 months. Overhaul or replace corroded parts in accordance with the service bulletin within 36 months after detection of the corrosion.

(4) If corrosion is found on any part of both carriage spindle/aft link assemblies on the same flap, prior to further flight, overhaul or replace the part(s) in accordance with the service bulletin or repair in accordance with the procedures specified in paragraph (m) of this AD.

Note 2:

For the purposes of this AD, a general visual inspection is: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to ensure visual access to all surfaces in the inspection area. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or droplight and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.”

Initial and Repetitive Overhauls

(g) For all airplanes: Prior to the accumulation of 8 years or 30,000 flight hours on any new or previously overhauled flap carriage spindle, whichever occurs later, remove the carriage spindle and aft link, and overhaul in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27-2280, Revision 3, dated November 30, 1989. Repeat the overhaul thereafter at intervals not to exceed 8 years or 30,000 flight hours, whichever occurs earlier. Accomplishment of initial overhaul required by this paragraph terminates the requirements of paragraph (f) of this AD.

New Requirements of This AD

Terminating Requirements

(h) The actions specified in paragraphs (i) and (j) of this AD must be accomplished in their entirety, at the specified compliance times, to terminate the requirements of paragraphs (f) and (g) of this AD. There is no terminating action for the requirements of paragraphs (i) and (j) of this AD.

Repetitive Inspection for Broken Parts

(i) For all airplanes: Within 12 months or 400 flight cycles after the effective date of this AD, whichever occurs earlier, do a general visual inspection of all eight carriage spindles and aft links to detect a broken carriage spindle or broken aft link, and do all applicable corrective actions before further flight. Repeat the inspection thereafter at intervals not to exceed 400 flight cycles. Do all actions in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 2008. For airplanes identified in Note (d) of Table 1 in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 2008, the initial compliance time and repetitive interval for a flap may be extended to 1,000 flight cycles when new carriages are installed at both the inboard and outboard carriage locations on the flap.

Repetitive Overhauls

(j) For all airplanes: At the later of the times specified in paragraph (j)(1) or (j)(2) of this AD, remove the carriage spindle and aft link, and overhaul in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 2008. Repeat the overhaul thereafter at the applicable repeat interval specified in paragraph 1.E., “Compliance,” of Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 2008.

(1) The applicable threshold specified in paragraph 1.E. “Compliance,” of Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 2008.

(2) Within 48 months after the effective date of this AD.

Optional Terminating Action

(k) For Groups 1 and 3 airplanes identified in Boeing Service Bulletin 747-27-2280, Revision 6, dated February 14, 2008: Replacing the existing 4340M aft link with a new corrosion resistant steel (CRES) aft link in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27-2371, dated December 20, 2000, terminates the repetitive inspection requirements of paragraph (f) of this AD, and the repetitive overhaul requirements of paragraphs (g) and (j) of this AD for that aft link only. The repetitive inspections for broken parts required by paragraph (i) of this AD cannot be terminated.

Credit for Previous Revision of Service Bulletin

(l) Actions done before the effective date of this AD in accordance with Boeing Service Bulletin 747-27-2280, Revision 4, dated April 26, 2001, are acceptable for compliance with the corresponding requirements of paragraphs (f) and (g) of this AD. Actions done before the effective date of this AD in accordance with Boeing Service Bulletin 747-27-2280, Revision 5, dated April 5, 2007, are acceptable for compliance with the corresponding requirements of paragraphs (i) and (j) of this AD.

Alternative Methods of Compliance (AMOCs)

(m)(1) The Manager, Seattle Aircraft Certification Office (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) 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) AMOCs approved previously in accordance with AD 90-17-19 are approved as AMOCs for the corresponding provisions of this AD.

(4) Adjustments to the compliance times approved previously in accordance with AD 90-17-19 are not approved for the corresponding provisions of this AD.

(5) 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 April 18, 2008.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.