05-20268. Airworthiness Directives; Boeing Model 747 Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 747 airplanes. This proposed AD would require the following actions for the drive mechanism of the horizontal stabilizer: Repetitive detailed inspections for discrepancies and loose ball bearings; repetitive lubrication of the ballnut and ballscrew; repetitive measurements of the freeplay between the ballnut and the ballscrew; and corrective action if necessary. This proposed AD is prompted by a report of extensive corrosion of a ballscrew in the drive mechanism of the horizontal stabilizer on a similar airplane model. We are proposing this AD to prevent an undetected failure of the primary load path for the ballscrew in the horizontal stabilizer and subsequent wear and failure of the secondary load path, which could lead to loss of control of the horizontal stabilizer and consequent loss of control of the airplane.

DATES:

We must receive comments on this proposed AD by November 21, 2005.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, Room PL-401, Washington, DC 20590.
• By fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

You can get the service information identified in this proposed AD from Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov,, or at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Room PL-401, on the plaza level of the Nassif Building, Washington, DC.

FOR FURTHER INFORMATION CONTACT:

Kelly McGuckin, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Airplane Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

The FAA has implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, new AD actions are posted on DMS and assigned a docket number. We track each action and assign a corresponding directorate identifier. The DMS AD docket number is in the form “Docket No. FAA-2005-99999.” The Transport Airplane Directorate identifier is in the form “Directorate Identifier 2005-NM-999-AD.” Each DMS AD docket also lists the directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes.

Comments Invited

We invite you to submit any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2005-22624; Directorate Identifier 2004-NM-81-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments submitted by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov,, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at http://www.faa.gov/​language and http://www.plainlanguage.gov.

Examining the Docket

You can examine the AD docket in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone [phone]) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

On January 31, 2000, there was an accident involving a McDonnell Douglas Model DC-9-83 (MD-83) airplane. The National Transportation Safety Board (NTSB) determined that the probable cause of this accident was a loss of airplane pitch control resulting from the in-flight failure of the acme nut threads of the jackscrew assembly of the horizontal stabilizer trim system. The NTSB concluded that the thread failure was caused by excessive wear, resulting from insufficient lubrication of the jackscrew assembly.

The drive mechanism of the horizontal stabilizer on McDonnell Douglas Model DC-9-83 (MD-83) airplanes has a jackscrew assembly with an acme screw. The drive mechanism of the horizontal stabilizer on Boeing Model 747 airplanes uses a ballscrew. Acme screws and ballscrews have some differences in design, but perform similar functions and have the same airplane level effect following failure. The manufacturer's safety analysis of the 747 drive mechanism found no safety problems with the configuration of the drive mechanism, but showed that changes to the maintenance procedures and maintenance intervals are required to keep the drive mechanism properly maintained and operating as designed.

We have received a report indicating that the ballscrew in the drive mechanism of the horizontal stabilizer on a Boeing Model 757 series airplane showed extensive corrosion, which could lead to excessive wear. The ballscrew on Boeing Model 757 airplanes is similar to that on the Boeing Model 747 airplanes that are the subject of this proposed AD. Therefore, both of these airplane models could have the same unsafe condition. We are considering separate action for Boeing Model 757 airplanes and other similar Boeing airplanes.

Extensive corrosion of the ballscrew in the drive mechanism of the horizontal stabilizer, if not corrected, could cause an undetected failure of the primary load path for the ballscrew and subsequent wear and failure of the secondary load path, which could lead to loss of control of the horizontal stabilizer and consequent loss of control of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 747-27A2396, Revision 1, dated August 4, 2005.

The compliance times specified in the service bulletin is as follows:

For all airplanes: The compliance times for the initial detailed inspections and lubrication of the ballnut and ballscrew is 15,000 total flight hours or 18 months after the original issue date on the service bulletin, whichever occurs later. The inspection is repeated at intervals not to exceed between 2,000 and 4,000 flight hours or 24 months, whichever occurs first; the lubrication is repeated at intervals not to exceed 2,000 flight hours or 12 months, whichever occurs first.

For all airplanes except those on which an FAA-approved low utilization maintenance program is in effect: The compliance time for the initial ballscrew-to-ballnut freeplay inspection is 15,000 flight hours after accomplishing the last ballscrew-to-ballnut freeplay inspection or 18 months after the original issue date on the service bulletin, whichever occurs later. If the inspection has never been done, the compliance time for the initial inspection is 15,000 flight hours after the delivery date of the airplane or 18 months after the original issue date on the service bulletin, whichever occurs later. The inspection is repeated at intervals not to exceed between 18,000 flight hours and 21,000 flight hours.

For all airplanes except those on which an FAA-approved low utilization maintenance program is in effect: The compliance time for the initial ballscrew-to-ballnut freeplay inspection is 60 months after accomplishing the last ballscrew-to-ballnut freeplay inspection. If the inspection has never been done, the compliance time for the initial inspection is within 60 months after the delivery date of the airplane. The inspection is repeated at intervals not to exceed 72 months.

The service bulletin also describes the procedures in the following table for the drive mechanism of the horizontal stabilizer.

Procedures Specified in Boeing Alert Service Bulletin 747-27A2396

Work package	Repetitive actions	Corrective action
1	Accomplishing detailed visual inspections for discrepancies (including cracks, corrosion, damage, and worn areas); and a detailed inspection for loose ball bearings of the external areas of the drive mechanism and areas below the drive mechanism	Replacing the ballscrew actuator with a new or overhaulted actuator if any discrepancy is found during any inspection.
2	Lubricating the ballnut and ballscrew of the horizontal stabilizer drive mechanism	Not applicable.
3	Measuring the freeplay between the ballnut and ballscrew	Replacing the ballscrew actuator with a new or overhauled actuator if the freeplay is more than the specified limit.

We have determined that accomplishing the actions specified in the service bulletin will adequately address the unsafe condition.

The service bulletin refers to the 747 Airplane Maintenance Manuals (AMM) in the following table as additional sources of service information for accomplishing the detailed inspections, lubrications, freeplay measurements, and corrective action.

Additional Sources of Service Information

Boeing AMM	Subject
747-100/200/300 AMM	12-21-19
747-100/200/300 AMM	27-41-06
747-400 AMM	12-21-19
747-400 AMM	27-41-06

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. Therefore, we are proposing this AD, which would require the following actions for the drive mechanism of the horizontal stabilizer:

• Repetitive detailed inspections for discrepancies of the ballscrew assembly;
• Repetitive lubrication of the ballnut and ballscrew;
• Repetitive measurements of freeplay between the ballnut and the ballscrew; and
• Corrective action if necessary.

The proposed AD would require you to use the service bulletin described previously to perform these actions; except as discussed under “Difference Between the Proposed AD and Service Information.”

Differences Between the Proposed AD and Service Information

The service bulletin specifies compliance times relative to the date of issuance of the service bulletin; however, this proposed AD would require compliance before the specified compliance time after the effective date of this AD.

Costs of Compliance

This proposed AD would affect about 1,082 Model 747 series airplanes worldwide. The following table provides the estimated costs for U.S. operators to comply with this proposed AD, per cycle.

Estimated Costs

Repetitive actions	Work hours	Average labor rate per hour	Parts	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Detailed inspection	1	$65	None	$65	236	$15,340
Lubrication	1	65	None	65	236	15,340
Freeplay measurement	3	65	None	195	236	46,020

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 will not have federalism implications under Executive Order 13132. This proposed AD will 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. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

• Air transportation
• Airplane
• 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 FAA amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2005-22624; Directorate Identifier 2004-NM-81-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by November 21, 2005.

Affected ADs

(b) None.

Applicability

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

Unsafe Condition

(d) This AD was prompted by a report of extensive corrosion of a ballscrew in the horizontal stabilizer of a similar airplane model. We are issuing this AD to prevent an undetected failure of the primary load path for the ballscrew in the drive mechanism of the horizontal stabilizer and subsequent wear and failure of the secondary load path, which could lead to loss of control of the horizontal stabilizer and consequent loss of control 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 Detailed Inspection/Lubrication/Freeplay Measurement and Corrective Action

(f) Do all the applicable actions, including any applicable corrective action, specified in Work Packages 1, 2, and 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-27A2396, Revision 1, dated August 4, 2005. Do the actions at the applicable compliance time specified in Table 1 of paragraph 1.E. “Compliance” of the service bulletin; except, where the service bulletin specifies a compliance time relative to the original issue date of the service bulletin, this AD requires compliance relative to the effective date of this AD. Where the service bulletin specifies a compliance time relative to the delivery date of the airplane, this AD requires compliance relative to the date of issuance of the original standard airworthiness certificate. Do any applicable corrective action before further flight. Repeat the actions at the applicable repeat interval specified in Table 1 of paragraph 1.E “Compliance” of the service bulletin.

Note 1:

Boeing Alert Service Bulletin 747-27A2396, Revision 1, dated August 4, 2005, refers to the Airplane Maintenance Manuals (AMMs) in Table 1 of this AD as additional sources of service information for accomplishing the detailed visual inspections, lubrications, freeplay measurements, and corrective actions.

Table 1.—Additional Sources of Service Information

Boeing AMM	Subject
747-100/200/300 AMM	12-21-19
747-100/200/300 AMM	27-41-06
747-400 AMM	12-21-19
747-400 AMM	27-41-06

Previously Accomplished Actions

(g) For airplanes on which the drive mechanism of the horizontal stabilizer was replaced before the effective date of this AD with a drive mechanism that was not new or overhauled, and the detailed and freeplay inspections were not accomplished in accordance with Boeing Alert Service Bulletin 747-27A2396, dated September 4, 2003: Within 4,000 flight hours or 24 months after the effective date of this AD, whichever is first, accomplish the inspections, and perform any applicable corrective action before further flight, in accordance with Work Package 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-27A2396, Revision 1, dated August 4, 2005.

Parts Installation

(h) As of the effective date of this AD, no person may install on any airplane a horizontal stabilizer trim actuator unless it is new or has been overhauled in accordance with Boeing Alert Service Bulletin 747-27A2396, Revision 1, dated August 4, 2005; or has been inspected, lubricated, and measured in accordance with paragraph (f) of this AD.

Alternative Methods of Compliance (AMOCs)

(i) The Manager, Seattle Airplane Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19.

Issued in Renton, Washington, on September 30, 2005.

Ali Bahrami,

Manager, Transport Airplane Directorate, Airplane Certification Service.