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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. FAA-2008-0933; Directorate Identifier 2007-NM-261-AD]
          - RIN 2120-AA64

# 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 777 airplanes. The existing AD requires, for the drive mechanism of the horizontal stabilizer, repetitive detailed inspections for discrepancies, 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 would revise the compliance times of the existing AD. This proposed AD results from a report of extensive corrosion of a ballscrew in the drive mechanism of the horizontal stabilizer on a Boeing Model 757 airplane, which is similar in design to the ballscrew on Model 777 airplanes. We are proposing 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.

# DATES:

We must receive comments on this proposed AD by October 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:

Kelly McGuckin, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6490; fax (425) 917-6590.

# SUPPLEMENTARY INFORMATION:

## Comments Invited

                    We invite you to send any written relevant data, views, or arguments about                           ( print page 50897)                        this proposed AD. Send your comments to an address listed under the                     **ADDRESSES**                     section. Include “Docket No. 2008-0933; Directorate Identifier 2007-NM-261-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 14, 2007, we issued AD 2007-17-12, amendment 39-15170 (72 FR 49158, August 28, 2007), for all Boeing Model 777 airplanes. That AD requires, for the drive mechanism of the horizontal stabilizer, repetitive detailed inspections for discrepancies, repetitive lubrication of the ballnut and ballscrew, repetitive measurements of the freeplay between the ballnut and the ballscrew, and corrective action if necessary. That AD resulted from a report of extensive corrosion of a ballscrew in the drive mechanism of the horizontal stabilizer on a Boeing Model 757 airplane, which is similar in design to the ballscrew on Model 777 airplanes. We issued that 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.

## Actions Since Existing AD Was Issued

Since we issued AD 2007-17-12, Boeing submitted a letter asking that we clarify the compliance times specified in that AD. In this letter Boeing states that the wording in the existing AD has resulted in some confusion and may not adequately account for airplanes that have replacement actuators that are new or have been overhauled. Boeing proposes that the AD use the following three different categories for the horizontal stabilizer trim actuator (HSTA):
    - HSTA not replaced;
    - HSTA replaced with a new or overhauled HSTA; and
    - HSTA replaced with a HSTA that was not new or overhauled.

Boeing further states that the existing AD does not account for airplanes receiving a certificate of airworthiness after the effective date of the AD. Boeing suggests that the following changes be made to the existing AD to address the three different categories and revise the compliance times.

Boeing proposes that we make changes to paragraph (g) of AD 2007-17-12 to include subparagraphs (g)(1), (g)(2), and (g)(3) as follows:

(g) For airplanes that have received a certificate of airworthiness prior to the effective date of this AD: Within 180 days or 3,500 [flight hours] after the effective date of this AD, whichever occurs first, perform a maintenance records check or inspect to determine the status of the horizontal stabilizer trim actuator as follows:

(1) Original horizontal stabilizer trim actuator still installed;

(2) Original horizontal stabilizer trim actuator replaced with a new or overhauled horizontal stabilizer trim actuator;

(3) Original horizontal stabilizer trim actuator replaced with a serviceable horizontal stabilizer trim actuator that was not new or overhauled, and has not received a detailed inspection and freeplay measurement since the replacement conducted per the Service Bulletin identified in paragraph (f) of this AD.

Boeing further suggests that we change paragraphs (h)(1), (h)(2), (i)(1), (i)(2), (j)(1), and (j)(2) of AD 2007-17-12, as follows:

(1) For airplanes identified in sub-paragraph (g)(1) of this AD and those receiving a certificate of airworthiness on or after the effective date of this AD: Before the accumulation of 15,000 total flight hours or within 18 months after the effective date of this AD, whichever occurs later.

(2) For airplanes identified in sub-paragraph (g)(2) of this AD: Before the accumulation of 15,000 flight hours since replacement of the horizontal stabilizer trim actuator, or within 18 months after the effective date of this AD, whichever occurs later.

Boeing further suggests that we add a new subparagraph (3) to paragraphs (h), (i), and (j) of AD 2007-17-12, as shown:

(3) For airplanes identified in sub-paragraph (g)(3) of this AD: Before the accumulation of 3,500 flight hours or within 12 months after the effective date of this AD, whichever occurs later.

We agree with Boeing that the compliance times need to be clarified. Therefore, we are proposing this AD, which would supersede AD 2007-17-12, and retain the actions specified in the existing AD but with revisions to paragraphs (g), (h), (i), and (j) to reflect Boeing's suggestions and to clarify the compliance times. This proposed AD also contains new paragraphs (h)(4), (i)(4), and (j)(4) to address airplanes that received an original airworthiness certificate or original export certificate of airworthiness on or after the effective date of this AD.

We have also determined that an additional category is needed to account for airplanes on which the HSTA has been replaced with an actuator that is not new or not overhauled but that has received a detailed inspection and freeplay measurement as described in paragraphs (h) and (i) of this proposed AD since that replacement. Accordingly, we have added paragraph (g)(4) to this proposed AD.

We have also clarified the wording in paragraph (l) of this proposed AD to specify that the credit is for replacement of the HSTA.

## 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 2007-17-12, to retain the actions specified in the existing AD but with new initial inspection compliance times.

## Costs of Compliance

There are about 596 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 203 airplanes of U.S. registry. The new requirements of this proposed AD add no additional economic burden. The current costs of the existing AD are repeated for the convenience of affected operators, as follows.

The maintenance records check would take about 1 work hour per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the maintenance records check for U.S. operators is $16,240, or $80 per airplane.

The proposed detailed inspection would take about 1 work hour per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the inspection for U.S. operators is $16,240, or $80 per airplane, per inspection cycle.

The proposed freeplay measurement would take about 5 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the freeplay measurement for U.S. operators is $81,200, or $400 per airplane, per measurement cycle.

                    The proposed required lubrication would take about 1 work hour per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the lubrication for U.S. operators is $16,240, or $80 per airplane, per lubrication cycle.                          ( print page 50898)    

## 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

2. The Federal Aviation Administration (FAA) amends § 39.13 by removing amendment 39-15170 (72 FR 49158, August 28, 2007) and adding the following new airworthiness directive (AD):

**Boeing:**                                 Docket No. FAA-2008-0933; Directorate Identifier 2007-NM-261-AD.                            

## Comments Due Date

(a) The FAA must receive comments on this AD action by October 14, 2008.

## Affected ADs

(b) This AD supersedes AD 2007-17-12.

## Applicability

(c) This AD applies to all Boeing Model 777 airplanes, certificated in any category.

## Unsafe Condition

(d) This AD results from a report of extensive corrosion of a ballscrew in the drive mechanism of the horizontal stabilizer on a Boeing Model 757 airplane, which is similar in design to the ballscrew on Model 777 airplanes. 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.

## Restatement of Requirements of AD 2007-17-12 With Revised Compliance Times

## Service Bulletin Reference

(f) The term “service bulletin,” as used in this AD, means Boeing Alert Service Bulletin 777-27A0059, Revision 1, dated August 18, 2005.

# Note 1:

The service bulletin refers to the Boeing 777 Aircraft Maintenance Manual (AMM), Subjects 12-21-05, 27-41-13, and 29-11-00, as additional sources of service information for accomplishing the actions required by this AD.

## Maintenance Records Check

(g) For airplanes that have received an original airworthiness certificate or original export certificate of airworthiness prior to the effective date of this AD: Within 180 days or 3,500 flight hours after the effective date of this AD, whichever occurs first, perform a maintenance records check or inspect to determine the status of the horizontal stabilizer trim actuator (HSTA) as specified in paragraph (g)(1), (g)(2), (g)(3), or (g)(4) of this AD, as applicable:

(1) The original HSTA has been neither replaced nor overhauled;

(2) The original HSTA has been replaced with a new or overhauled HSTA;

(3) The original HSTA has been replaced with a serviceable HSTA that was not new or not overhauled, and which has not received a detailed inspection and freeplay measurement as described in paragraphs (h) and (i) of this AD since that replacement; or

(4) The original HSTA has been replaced with a serviceable HSTA that was not new or not overhauled, and which has received a detailed inspection and freeplay measurement as described in paragraphs (h) and (i) of this AD since that replacement.

## Detailed Inspection

(h) Within the compliance time specified in paragraph (h)(1), (h)(2), (h)(3), or (h)(4) of this AD, as applicable: Perform a detailed inspection for discrepancies of the horizontal stabilizer trim actuator ballnut and ballscrew in accordance with Part 1 of the Accomplishment Instructions of the service bulletin. Repeat the detailed inspection thereafter at intervals not to exceed 3,500 flight hours or 12 months, whichever occurs first. If any discrepancy is found during any inspection required by this AD, before further flight, replace the actuator with a new or serviceable actuator, in accordance with the Accomplishment Instructions of the service bulletin.

(1) For airplanes identified in paragraph (g)(1) of this AD: Before the accumulation of 15,000 total flight hours, or within 18 months after the effective date of this AD, whichever occurs later.

(2) For airplanes identified in paragraph (g)(2) or (g)(4) of this AD: Before the accumulation of 15,000 flight hours since the replacement of the HSTA, or within 18 months after the effective date of this AD, whichever occurs later.

(3) For airplanes identified in paragraph (g)(3) of this AD: Before the accumulation of 3,500 flight hours since the replacement of the HSTA, or within 12 months after the effective date of this AD, whichever occurs later.

(4) For airplanes that have received an original airworthiness certificate or original export certificate of airworthiness on or after the effective date of this AD: Before the accumulation of 15,000 total flight hours, or within 18 months after the issuance of the original airworthiness certificate or original export certificate of airworthiness, whichever occurs later.

## Freeplay Measurement (Inspection)

(i) Within the compliance times specified in paragraphs (i)(1), (i)(2), (i)(3), and (i)(4) of this AD, as applicable: Perform a freeplay measurement of the ballnut and ballscrew in accordance with Part 2 of the Accomplishment Instructions of the service bulletin. Repeat the freeplay measurement thereafter at intervals not to exceed 18,000 flight hours or 60 months, whichever occurs first. If the freeplay is found to exceed the limits specified in the service bulletin during any measurement required by this AD, before further flight, replace the actuator with a new or serviceable actuator in accordance with the Accomplishment Instructions of the service bulletin.

                                (1) For airplanes identified in paragraph (g)(1) of this AD: Before the accumulation of                                       ( print page 50899)                                    15,000 total flight hours, or within 18 months after the effective date of this AD, whichever occurs later.                            

(2) For airplanes identified in paragraph (g)(2) or (g)(4) of this AD: Before the accumulation of 15,000 flight hours since the replacement of the HSTA, or within 18 months after the effective date of this AD, whichever occurs later.

(3) For airplanes identified in paragraph (g)(3) of this AD: Before the accumulation of 3,500 flight hours since the replacement of the HSTA, or within 12 months after the effective date of this AD, whichever occurs later.

(4) For airplanes that have received an original airworthiness certificate or original export certificate of airworthiness on or after the effective date of this AD: Before the accumulation of 15,000 total flight hours, or within 18 months after the issuance of the original airworthiness certificate or original export certificate of airworthiness, whichever occurs later.

## Lubrication

(j) Within the compliance times specified in paragraphs (j)(1), (j)(2), (j)(3), and (j)(4) of this AD, as applicable: Lubricate the ballnut and ballscrew in accordance with Part 3 of the Accomplishment Instructions of the service bulletin. Repeat the lubrication thereafter at intervals not to exceed 2,000 flight hours or 12 months, whichever occurs first.

(1) For airplanes identified in paragraph (g)(1) of this AD: Before the accumulation of 15,000 total flight hours, or within 18 months after the effective date of this AD, whichever occurs later.

(2) For airplanes identified in paragraph (g)(2) or (g)(4) of this AD: Before the accumulation of 15,000 flight hours since the replacement of the HSTA, or within 18 months after the effective date of this AD, whichever occurs later.

(3) For airplanes identified in paragraph (g)(3) of this AD: Before the accumulation of 3,500 flight hours since the replacement of the HSTA, or within 12 months after the effective date of this AD, whichever occurs later.

(4) For airplanes that have received an original airworthiness certificate or original export certificate of airworthiness on or after the effective date of this AD: Before the accumulation of 15,000 total flight hours, or within 18 months after the issuance of the original airworthiness certificate or original export certificate of airworthiness, whichever occurs later.

## Credit for Using Original Issue of Service Bulletin

(k) Actions performed prior to the effective date of this AD, in accordance with Boeing Alert Service Bulletin 777-27A0059, dated September 18, 2003, are considered acceptable for compliance with the corresponding actions specified in paragraphs (h), (i), and (j) of this AD.

## Credit for Hard-Time Replacement of HSTA

(l) Any HSTA overhauled within the compliance times specified in paragraphs (h), (i), and (j) of this AD or before the effective date of this AD—as part of a “hard-time” replacement program that includes removal of the HSTA from the airplane and overhaul of the stabilizer ballscrew in accordance with original equipment manufacturer component maintenance manual instructions—meets the intent of one detailed inspection, one freeplay inspection, and one lubrication of the HSTA. Therefore, any such HSTA is considered acceptable for compliance with the initial accomplishment of the actions specified in paragraphs (h), (i), and (j) of this AD, and repetitions of those actions may be determined from the performance date of that overhaul.

## Parts Installation

(m) As of the effective date of this AD, no person may install, on any airplane, a horizontal stabilizer trim actuator that is not new or overhauled, unless a detailed inspection, freeplay measurement, and lubrication of that actuator are performed in accordance with paragraphs (h), (i), and (j) of this AD, as applicable.

## Alternative Methods of Compliance (AMOCs)

(n)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, ATTN: Kelly McGuckin, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle ACO, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone (425) 917-6490; fax (425) 917-6590; 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.

Issued in Renton, Washington, on August 21, 2008.

Kevin Hull,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. E8-20087 Filed 8-28-08; 8:45 am]

BILLING CODE 4910-13-P