Airworthiness Directives; Boeing Model 747-400, 747-400D, and 747-400F 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 all Boeing Model 747-400, 747-400D, and 747-400F series airplanes. The existing AD currently requires reviewing airplane maintenance records, doing repetitive inspections for cracking of the yaw damper actuator portion of the upper and lower rudder power control modules (PCMs), replacing the PCMs if necessary, and reporting all airplane maintenance records review and inspection results to the manufacturer. This proposed AD would limit the applicability, reduce the initial inspection threshold and repetitive interval, remove the reporting requirement, and require installation of a secondary retention device for the yaw damper modulating piston. Installation of the secondary retention device would terminate the repetitive inspection requirements. This proposed AD results from additional reports of failure or cracking of the PCM manifold in the area of the yaw damper cavity endcap at intervals well below the initial inspection threshold of the existing AD. We are proposing this AD to prevent an uncommanded left rudder hardover in the event of cracking in the yaw damper actuator portion of the upper or lower rudder PCMs, and subsequent failure of the PCM manifold, which could result in increased pilot workload, and possible runway departure upon landing.

DATES:

We must receive comments on this proposed AD by April 14, 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: 202-493-2251.
• 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 800-647-5527) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Douglas Tsuji, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6487; fax (425) 917-6590.

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-2008-0273; Directorate Identifier 2007-NM-369-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 30, 2006, we issued AD 2006-18-17, amendment 39-14756 (71 FR 52999, September 8, 2006), for all Boeing Model 747-400, 747-400D, and 747-400F series airplanes. That AD requires reviewing airplane maintenance records, doing repetitive inspections for cracking of the yaw damper actuator portion of the upper and lower rudder power control modules (PCMs), replacing the PCMs if necessary, and reporting all airplane maintenance records review and inspection results to the manufacturer. That AD resulted from manufacturer findings that the inspections required by the existing AD (AD 2003-23-01, amendment 39-13364, which AD 2006-18-17 superseded) must be performed at regular intervals. We issued AD 2006-18-17 to detect and correct cracking in the yaw damper actuator portion of the upper and lower rudder PCMs, which could result in an uncommanded left rudder hardover, consequent increased pilot workload, and possible runway departure upon landing.

Actions Since Existing AD Was Issued

Since the issuance of AD 2006-18-17, there have been additional reports of cracked rudder PCMs in the yaw damper portion of the PCM manifold that failed well below the initial inspection threshold of the AD. As part of the National Transportation Safety Board (NTSB) and FAA investigation, it was determined that a permanent design modification must be made to the rudder PCM that prevents a left rudder hardover in the event of a failed rudder PCM manifold.

The preamble to AD 2006-18-17 specified that we considered the requirements “interim action.” That AD explained that we might consider further rulemaking since the root cause of the cracking had not been determined. Because of the additional premature failures of the rudder PCM, the manufacturer has now developed a final action, which is installation of a secondary means of retention for the modulating piston assembly in the event of a rudder PCM manifold failure. Therefore, we have determined that further rulemaking is indeed necessary; this proposed AD follows from that determination.

The inspection thresholds and intervals in AD 2006-18-17 correspond to those in Boeing Alert Service Bulletin 747-27A2397, Revision 2, dated September 1, 2005, which we referred to in AD 2006-18-17 as the appropriate source of service information for doing the initial and repetitive inspections. However, since we issued that AD, we have received additional reports of failure or cracking of the PCM manifold in the area of the yaw damper cavity endcap at intervals well below the initial inspection threshold of the existing AD. These incidents happened between 20,000 and 46,000 total flight hours. The initial flight-hour threshold in AD 2006-18-17 is 56,000 total flight hours, which corresponds to the threshold in Boeing Alert Service Bulletin 747-27A2397, Revision 2. Therefore, we are proposing that operators accomplish the ultrasonic inspections required by AD 2006-18-17 at reduced inspection threshold and intervals, until the final action is accomplished. Boeing has no objection to the reduced inspection thresholds and intervals.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-27A2479, dated November 8, 2007. The service bulletin describes procedures for installing a new secondary retention device for the yaw damper piston assembly in both the upper and lower PCMs. The service bulletin specifies two options for installing the new secondary retention device:

• Replacing the existing PCM with a new improved PCM.
• Modifying, testing, and re-identifying the existing PCM while installed on the airplane.

Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

Boeing Alert Service Bulletin 747-27A2479 refers to Parker Service Bulletins 332700-27-312 and 333200-27-314, both dated September 13, 2007, as additional sources of service information for modifying the PCM.

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 2006-18-17, and retain all but the reporting requirement of that AD. This proposed AD would also limit the applicability, reduce the inspection threshold and repetitive interval, and require eventual installation of a secondary retention device for the yaw damper modulating piston. Installation of a secondary retention device would terminate the repetitive inspection requirements of the existing AD.

Explanation of Reporting Requirement

AD 2006-18-17 requires that operators report crack findings to Boeing and return cracked or broken PCMs to Parker Hannifin Corporation. This proposed AD would not include those actions. Boeing has now developed a final action, so the report and parts return are no longer necessary.

Explanation of 30 Day Comment Period

Operators should note that because of the critical need to prevent an uncommanded left rudder hardover, we have determined that a comment period of 30 days, rather than 45 days, is necessary in this case.

Costs of Compliance

There are about 655 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 86 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.

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.