E7-22926. Airworthiness Directives; Boeing Model 737-200 Series Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-200 series airplanes. This proposed AD would require repetitive inspections to detect cracking of the support fittings of the Krueger flap actuators, and corrective actions if necessary. This proposed AD also would require eventual replacement of any existing aluminum support fitting on each wing with a steel fitting, and modification of the aft attachment of the actuator. Doing these actions would terminate the repetitive inspection requirements. This proposed AD results from reports of cracking due to fatigue and stress corrosion of the support fittings of the Krueger flap actuator. We are proposing this AD to prevent cracking of the support fittings, which could result in fracturing of the actuator attach lugs, separation of the actuator from the support fitting, severing of the hydraulic lines, resultant loss of hydraulic fluids, and consequent reduced controllability of the airplane.

DATES:

We must receive comments on this proposed AD by January 10, 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:

Nancy Marsh, 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-2007-0228; Directorate Identifier 2007-NM-107-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

We have received reports of cracks in the support fitting of the Krueger flap actuator mounted on the front spar of eight affected airplanes. On one airplane, the lugs on the No. 1 Krueger flap actuator support fitting severed completely, the actuator separated from the front spar, and the hydraulic lines were severed. On another airplane, both actuator attach lugs of a No. 1 flap support fitting were also completely severed. The cracking is attributed to fatigue and stress corrosion, and it is suspected that high clamp-up stresses may be contributing to cracks in the actuator attach lugs. Cracking of the support fittings, if not corrected, could result in fracturing of the actuator attach lugs, separation of the actuator from the support fitting, severing of the hydraulic lines, resultant loss of hydraulic fluids, and consequent reduced controllability of the airplane.

Other Relevant Rulemaking

On July 31, 2000, we issued AD 2000-15-18, amendment 39-11851 (65 FR 48371, August 8, 2000). That AD applies to certain Boeing Model 737-100 and -200 series airplanes, line numbers 001 through 813 inclusive. That AD requires inspections to detect cracking of the support fittings of the Krueger flap actuator; and, if necessary, replacement of existing fittings with new steel fittings and modification of the aft attachment of the actuator. That AD also requires eventual replacement of any existing aluminum Krueger flap actuator support fitting on each wing with a steel fitting, which terminates the repetitive inspection requirements. That AD resulted from reports of cracking due to fatigue and stress corrosion of the support fittings of the Krueger flap actuator. The actions in that AD are intended to prevent such cracking, which could result in fracturing of the actuator attach lugs, separation of the actuator from the support fitting, severing of the hydraulic lines, and resultant loss of hydraulic fluids. These conditions, if not corrected, could result in possible failure of one or more hydraulic systems, and consequent reduced controllability of the airplane.

Since we issued AD 2000-15-18, we have determined that the same unsafe condition addressed in that AD exists on certain additional Model 737-200 series airplanes. We were advised that Model 737-200 series airplanes, line numbers 814 through 826 inclusive, are also subject to the same unsafe condition addressed in AD 2000-15-18.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 737-57-1129, Revision 3, dated March 19, 2007. The service bulletin describes procedures for repetitive high frequency eddy current (HFEC) inspections to detect cracking of the support fittings of the Krueger flap actuators, and corrective actions if necessary. The corrective actions are replacement of existing fittings with new steel fittings and modification of the aft attachment of the actuator. This replacement and modification eliminates the need for the repetitive inspection requirements. 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 exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously.

Costs of Compliance

There are about 13 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	5	$80	$0	$400, per inspection cycle	3	$1,200, per inspection cycle.
Replacement	88	$80	$29,642	$36,682	3	$110,046.

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 adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-0228; Directorate Identifier 2007-NM-107-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 10, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-200 series airplanes, line numbers 814 through 826 inclusive, certificated in any category.

Unsafe Condition

(d) This AD results from reports of cracking due to fatigue and stress corrosion of the support fittings of the Krueger flap actuator. We are issuing this AD to prevent cracking of the support fittings, which could result in fracturing of the actuator attach lugs, separation of the actuator from the support fitting, severing of the hydraulic lines, resultant loss of hydraulic fluids, and consequent reduced controllability 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.

Repetitive Inspections

(f) Within 12 months after the effective date of this AD, do a high frequency eddy current (HFEC) inspection to detect cracking of the support fittings of the Krueger flap actuator on each wing, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-57-1129, Revision 3, dated March 19, 2007.

(1) If no cracking is detected, repeat the inspection thereafter at intervals not to exceed 3,000 flight hours until the terminating action required by paragraph (g) of this AD is accomplished.

(2) If any cracking is detected, before further flight, do the replacement and modification specified in paragraph (g) of this AD.

Terminating Action

(g) Within 60 months after the effective date of this AD: Replace any existing Krueger flap actuator aluminum support fitting on each wing with a steel fitting, and modify the actuator aft attachment, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-57-1129, Revision 3, dated March 19, 2007. Doing this replacement and modification terminates the repetitive inspection requirements of paragraph (f) of this AD.

Parts Replacement

(h) As of the effective date of this AD, no person may install on any airplane any aluminum support fitting (actuator support assembly) identified in the “Existing Part Number” column of paragraph 2.C. of Boeing Special Attention Service Bulletin 737-57-1129, Revision 3, dated March 19, 2007.

Actions Accomplished in Accordance With Previous Revisions of Service Bulletin

(i) Actions done before the effective date of this AD in accordance with the service bulletins listed in Table 1 of this AD, are acceptable for compliance with the corresponding requirements of this AD.

Table 1.—Previous Revisions of Service Bulletins

Boeing service bulletin	Revision level	Date
737-57-1129	1	October 30, 1981.
737-57-1129	2	May 28, 1998.

Alternative Methods of Compliance (AMOCs)

(j)(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) 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 November 13, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.