03-2097. Airworthiness Directives; Boeing Model 747-400 Series Airplanes Equipped With General Electric Model CF6-80C2 Series Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747-400 series airplanes, that currently requires repetitive tests of the cone brake of the central drive unit (CDU) of the thrust reversers, and corrective actions if necessary. This action would require installation of a thrust reverser actuation system (TRAS) lock and various related modifications and installations. Following installation of the TRAS lock, this action also would require repetitive functional tests of the TRAS lock, and corrective action if necessary. These actions are intended to prevent an inadvertent deployment of a thrust reverser during flight, which could result in loss of control of the airplane.

DATES:

Comments must be received by March 17, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-128-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2002-NM-128-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, PO Box 3707, Seattle, Washington 98124-2207; and AlliedSignal Aerospace Services, PO Box 52170, Phoenix, Arizona 85072-2170. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Sulmo Mariano, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2002-NM-128-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-128-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On April 26, 2000, the FAA issued AD 2000-09-03, amendment 39-11711 (65 FR 25829, May 4, 2000), to supersede AD 2000-02-33, amendment 39-11551 (65 FR 5742). AD 2000-09-03 is applicable to certain Boeing Model 747-400 series airplanes, and requires repetitive tests of the cone brake of the central drive unit (CDU) of the thrust reversers, and corrective actions if necessary. That action was prompted by a report indicating that completion of a cone brake test required by AD 2000-02-33 was ineffective for certain airplanes. The requirements of that AD 2000-09-03 are intended to ensure the integrity of the fail-safe features of the thrust reverser system by preventing possible failure modes in the thrust reverser control system that can result in inadvertent deployment of a thrust reverser during flight.

Actions Since Issuance of Previous Rule

In the preamble to AD 2000-02-33, the FAA specified that the actions required by that AD were considered “interim action” and that the manufacturer was developing a modification to positively address the unsafe condition. We indicated that we might consider further rulemaking action once the modification was developed, approved, and available. The manufacturer now has developed such a modification, and we have determined that further rulemaking action is indeed necessary; this proposed AD follows from that determination.

While the service information for installation of the modification has been available for some time, we have prioritized the issuance of ADs for corrective actions for the thrust reverser system on Boeing airplane models. Based on service experience, analyses, and flight simulator studies, it was determined that an in-flight deployment of a thrust reverser has more effect on controllability of twin-engine airplane models than of Model 747 series airplanes, which have four engines. For this reason, the highest priority was given to rulemaking that required corrective actions for the twin-engine airplane models. ADs that correct the same type of unsafe condition as would be addressed by this proposed AD have been issued previously for specific airplanes within the Boeing Model 737, 757, and 767 series.

After the issuance of the service information related to the modification, we received a report from the airplane manufacturer indicating that there have been several incidents of failure of a connection shaft for the thrust reverser actuation system (TRAS) brake, which is installed as part of the modification. Such failure of the connection shaft would result in the TRAS lock being ineffective.

Based on data on the connection shaft failures that have been collected by the airplane manufacturer to date, we have determined that we can best ensure the continued safety of the affected fleet of airplanes by proceeding with rulemaking at this time to propose to require installation of a TRAS lock on the thrust reversers on Model 747-400 series airplanes. The airplane manufacturer is continuing to investigate the failures of the connection shaft. If the investigation reveals that corrective actions are necessary to prevent failure of the connection shaft, we may consider further rulemaking to mandate such corrective actions.

Explanation of Relevant Service Information

We have reviewed and approved Boeing Service Bulletin 747-78-2151, Revision 1, dated August 21, 1997, as revised by Notice of Status Change (NSC) 747-78-2151 NSC 04, dated November 26, 1997, and NSC 747-78-2151 NSC 05, dated December 18, 1997; and Boeing Service Bulletin 747-78-2151, Revision 2, dated January 13, 2000. Those service bulletins describe procedures for completing the installation of and activating a TRAS lock on each thrust reverser. These procedures include replacing a certain microswitch pack with a new one; adding new wires; routing certain new wire bundles; changing certain wiring, circuit breakers, and components; installing thrust-reverser relay panels; and performing repetitive functional tests to ensure that the thrust reverser actuation system operates properly. In addition, those service bulletins refer to several other service bulletins that describe actions that must be accomplished prior to or concurrently with Boeing Service Bulletin 747-78-2151. These service bulletins, which describe various modifications and installations associated with the TRAS locks, are as follows:

• Lockheed Martin Service Bulletin 78-1007, Revision 1, dated March 18, 1997, which describes procedures for installation of a bracket and fastening hardware for the TRAS lock on each thrust reverser.
• Boeing Service Bulletin 747-78-2132, Revision 2, dated December 11, 1997, which describes procedures for installing wiring provisions for the TRAS lock in various areas of the airplane.
• Lockheed Martin Service Bulletin 78-1020, Revision 2, dated March 20, 1997, which describes procedures for installing the TRAS lock (also called an electromechanical lock or brake) and a flexible drive cable on each thrust reverser.
• Boeing Service Bulletin 747-31-2242, dated April 18, 1996, which describes procedures for installing new integrated display system software in six integrated display units and three electronic flight information/engine indication and crew alerting system (EICAS) interface units.
• Boeing Service Bulletin 747-45-2016, Revision 1, dated May 2, 1996, which describes procedures for replacing two central maintenance computers (CMCs) with new, improved CMCs, and installing new software for the CMCs.

Accomplishment of the actions specified in these service bulletins is intended to adequately address the identified unsafe condition.

We also have reviewed and approved Boeing Alert Service Bulletin 747-78A2166, Revision 2, dated March 15, 2001. (AD 2000-09-03 refers to Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997, as an appropriate source of service information for the functional test of the CDU cone brake and corrective actions on certain airplanes.) Among other things, Revision 2 of the service bulletin includes revised procedures for the functional test of the CDU cone brake that are appropriate for airplanes on which a TRAS lock has been installed, and procedures for a functional test of the TRAS lock. That service bulletin also specifies corrective action (e.g., replacement of a flexshaft and/or electromechanical gearbox with new or serviceable parts, and/or replacement of the TRAS lock (electromechanical brake) or CDU with new or serviceable parts) if any discrepancy is found during the functional test of the CDU cone brake or TRAS lock. We have revised paragraphs (a) and (c) under the heading “Requirements of AD 2000-09-03” in this proposed AD to include Boeing Alert Service Bulletin 747-78A2166, Revision 2, as an acceptable source of service information for actions in those paragraphs.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would supersede AD 2000-09-03 to continue to require repetitive tests of the CDU cone brake of the thrust reversers, and corrective actions if necessary. The proposed AD would add requirements for installation of a TRAS lock, and various related modifications and installations. The actions would be required to be accomplished in accordance with the service bulletins described previously, except as discussed below.

Explanation of Differences Between Service Bulletins and Proposed AD

The new actions in this proposed AD would apply to Boeing Model 747-400 series airplanes as listed in Boeing Service Bulletin 747-78-2151, Revision 2. However, the effectivity listings of Boeing Service Bulletins 747-78-2132, Revision 2, 747-31-2242, and 747-45-2016, Revision 1, identify airplanes with line numbers other than those identified in Boeing Service Bulletin 747-78-2151, Revision 2, as being subject to the actions therein. We have coordinated with the airplane manufacturer on this issue, and the manufacturer agrees with our determination that, to be correct and complete, the new actions in paragraph (d) of this proposed AD should apply to Model 747-400 series airplanes as listed in Boeing Service Bulletin 747-78-2151, Revision 2.

Cost Impact

There are approximately 145 airplanes of the affected design in the worldwide fleet. The FAA estimates that 8 airplanes of U.S. registry would be affected by this proposed AD.

The functional test that is currently required by AD 2000-09-03 takes approximately 12 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $5,760, or $720 per airplane, per test cycle.

The installations in Boeing Service Bulletin 747-78-2151, Revision 2, would take approximately 410 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would be provided at no charge. Based on these figures, the cost impact of this proposed requirement on U.S. operators is estimated to be $196,800, or $24,600 per airplane.

The installation specified in Lockheed Martin Service Bulletin 78-1007, Revision 1, would take approximately 60 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would be provided at no charge. Based on these figures, the cost impact of this proposed requirement on U.S. operators is estimated to be $28,800, or $3,600 per airplane.

The installation specified in Boeing Service Bulletin 747-78-2132, Revision 2, would take approximately 223 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost between $32,219 and $36,562 per airplane. Based on these figures, the cost impact of this proposed requirement is estimated to be between $45,599 and $49,942 per airplane. The manufacturer may cover the cost of replacement parts associated with this service bulletin, subject to warranty conditions. As a result, the costs attributable to this proposed action may be less than stated above.

The installation specified in Lockheed Martin Service Bulletin 78-1020, Revision 2, would take approximately 16 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would be provided at no charge. Based on these figures, the cost impact of this proposed requirement on U.S. operators is estimated to be $7,680, or $960 per airplane.

The installation specified in Boeing Service Bulletin 747-31-2242 would take approximately 2 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. The cost of required parts would be negligible. Based on these figures, the cost impact of this proposed requirement is estimated to be $960, or $120 per airplane. The manufacturer may cover the cost of replacement parts and labor costs associated with accomplishment of this service bulletin, subject to warranty conditions. As a result, the costs attributable to this proposed action may be less than stated.

The installation specified in Boeing Service Bulletin 747-45-2016, Revision 1, would take approximately 3 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. The cost of required parts would be negligible. Based on these figures, the cost impact of this proposed requirement is estimated to be $1,440, or $180 per airplane. The manufacturer may cover the labor costs associated with accomplishment of this service bulletin, subject to warranty conditions. As a result, the costs attributable to this proposed action may be less than stated above.

The functional test that would be required following installation of the TRAS lock would take approximately 12 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this proposed requirement is estimated to be $5,760, or $720 per airplane, per test cycle.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by removing amendment 39-11711 ( 65 FR 25829, May 4, 2000), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2002-NM-128-AD. Supersedes AD 2000-09-03, Amendment 39-11711.

Applicability: Model 747-400 series airplanes equipped with General Electric (GE) Model CF6-80C2 series engines, certificated in any category.

Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (h)(1) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent an inadvertent deployment of a thrust reverser during flight, which could result in loss of control of the airplane, accomplish the following:

Requirements of AD 2000-09-03

Repetitive Functional Tests

(a) Within 1,000 hours time-in-service after the most recent test of the center drive unit (CDU) cone brake as specified in paragraph (b)(1) of AD 94-15-05, amendment 39-8976; or within 650 hours time-in-service after May 19, 2000 (the effective date of AD 2000-09-03, amendment 39-11711); whichever occurs later: Perform a functional test to detect discrepancies of the CDU cone brake on each thrust reverser as specified in paragraph (a)(1) or (a)(2) of this AD, as applicable.

(1) For Model 747-400 series airplanes equipped with thrust reversers that have not been modified in accordance with Boeing Service Bulletin 747-78-2151 or a production equivalent: Perform the test in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997; or paragraph 3.C. of Boeing Alert Service Bulletin 747-78A2166, Revision 2, excluding Evaluation Form, dated March 15, 2001; or the applicable section of paragraph III.A. of the Accomplishment Instructions of Boeing Service Bulletin 747-78A2113, Revision 2, dated June 8, 1995; or Revision 3, dated September 11, 1997. Repeat the test thereafter at intervals not to exceed 650 hours time-in-service.

(2) For Model 747-400 series airplanes equipped with thrust reversers that have been modified in accordance with Boeing Service Bulletin 747-78-2151 or a production equivalent: Perform the test in accordance with Appendix 1 (including Figure 1) of this AD, or paragraph 3.C. of Boeing Alert Service Bulletin 747-78A2166, Revision 2, excluding Evaluation Form, dated March 15, 2001. After the effective date of this AD, only Boeing Alert Service Bulletin 747-78A2166, Revision 2, may be used. Repeat the test thereafter at intervals not to exceed 1,000 hours time-in-service.

Note 2:

Accomplishment of the CDU cone brake test during production in accordance with Production Revision Record (PRR) 80452-102 prior to May 19, 2000, is considered acceptable for compliance with the initial test required by paragraph (a) of this AD.

Note 3:

Model 747-400 series airplanes, line numbers 1061 and subsequent, equipped with GE CF6-80C2 engines, had a third locking system installed during production in accordance with Production Revision Record (PRR) 80452-102, and were not modified in accordance with Boeing Service Bulletin 747-78-2151 (which is a retrofit action for airplanes having line numbers 700 through 1060 inclusive).

Terminating Action

(b) Accomplishment of the functional test of the CDU cone brake, as specified in paragraph (a) of this AD, constitutes terminating action for the repetitive tests of the CDU cone brake required by paragraph (b)(1) of AD 94-15-05.

Corrective Action

(c) If any functional test required by paragraph (a) of this AD cannot be successfully performed as specified in the referenced service bulletin, or if any discrepancy is detected during any functional test required by paragraph (a) of this AD, accomplish either paragraph (c)(1) or (c)(2) of this AD.

(1) Prior to further flight, repair in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997; Boeing Alert Service Bulletin 747-78A2166, Revision 2, excluding Evaluation Form, dated March 15, 2001; Boeing Service Bulletin 747-78A2113, Revision 2, dated June 8, 1995; or Revision 3, dated September 11, 1997. After the effective date of this AD, only Boeing Alert Service Bulletin 747-78A2166, Revision 2; or Boeing Service Bulletin 747-78A2113, Revision 2 or Revision 3; may be used.

(2) The airplane may be operated in accordance with the provisions and limitations specified in the operator's FAA-approved Minimum Equipment List (MEL), provided that no more than one thrust reverser on the airplane is inoperative.

New Requirements of This AD

Installation of Thrust Reverser Actuator System Lock and Associated Actions

(d) For airplanes listed in Boeing Service Bulletin 747-78-2151, Revision 2, dated January 13, 2000: Within 36 months after the effective date of this AD, do paragraphs (d)(1) and (d)(2) of this AD.

(1) Install and activate a thrust reverser actuator system (TRAS) lock on each thrust reverser per the Accomplishment Instructions of Boeing Service Bulletin 747-78-2151, Revision 1, excluding Evaluation Form, dated August 21, 1997; as revised by Notice of Status Change (NSC) 747-78-2151 NSC 04, dated November 26, 1997; and NSC 747-78-2151 NSC 05, dated December 18, 1997; or Boeing Service Bulletin 747-78-2151, Revision 2, excluding Evaluation Form. The procedures for completing the installation and activating the TRAS lock include replacing a certain microswitch pack with a new one; adding new wires; routing certain new wire bundles; changing certain wiring, circuit breakers, and components; installing thrust-reverser relay panels; and performing a functional test to ensure that the thrust reverser actuation system operates properly.

(2) Prior to or concurrently with the installation required by paragraph (d)(1) of this AD, do the requirements of paragraphs (d)(2)(i), (d)(2)(ii), (d)(2)(iii), (d)(2)(iv), and (d)(2)(v) of this AD.

(i) Install a bracket and fastening hardware for the third locking system on each thrust reverser, per Lockheed Martin Service Bulletin 78-1007, Revision 1, dated March 18, 1997.

(ii) Install wiring provisions in various areas of the airplane, per the Accomplishment Instructions of Boeing Service Bulletin 747-78-2132, Revision 2, excluding Evaluation Form, dated December 11, 1997.

(iii) Install a TRAS lock (also called an electromechanical lock or brake) and a flexible drive cable on each thrust reverser, per Lockheed Martin Service Bulletin 78-1020, Revision 2, dated March 20, 1997.

(iv) Install new integrated display system software in six integrated display units and three electronic flight information/engine indication and crew alerting system (EICAS) interface units, per the Accomplishment Instructions of Boeing Service Bulletin 747-31-2242, dated April 18, 1996.

(v) Replace two central maintenance computers (CMCs), part number 622-8592-103, with new, improved CMCs, part number 622-8592-105, and install new software for the CMCs, per the Accomplishment Instructions of Boeing Service Bulletin 747-45-2016, Revision 1, dated May 2, 1996.

Repetitive Tests

(e) For airplanes on which a TRAS lock is installed on the thrust reversers: Within 1,000 flight hours after the installation of the TRAS lock, or within 90 flight hours after the effective date of this AD, whichever is later, do a functional test of the TRAS lock (also called an electromechanical lock or brake) per the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2166, Revision 2, excluding Evaluation Form, dated March 15, 2001. Then, repeat this test at least every 1,000 flight hours. If the functional test cannot be successfully performed, before further flight, repair per the Accomplishment Instructions of the service bulletin, and repeat the test until it is successful.

Dispatch Limitations

(f) If, prior to accomplishment of Boeing Service Bulletin 747-78-2151 on any airplane, it becomes necessary to install a thrust reverser with the TRAS lock installed, dispatch of the airplane is allowed per the provisions and limitations specified in the 747-400 Master Minimum Equipment List (MMEL), provided that the thrust reverser assembly that has the TRAS lock installed is deactivated per the 747-400 Dispatch Deviation Guide, Boeing Document D6U10151, dated June 28, 2002. Installation of a thrust reverser without a TRAS lock installed and reactivation of the thrust reverser must be accomplished within the time constraints specified in the MMEL.

(g) If, after accomplishment of Boeing Service Bulletin 747-78-2151 on any airplane, it becomes necessary to install a thrust reverser assembly that does not have the TRAS lock installed, dispatch of the airplane is allowed per the provisions and limitations specified in the Boeing Model 747-400 MMEL, provided that the thrust reverser assembly that does not have the TRAS lock installed is deactivated per the 747-400 Dispatch Deviation Guide, Boeing Document D6U10151, dated June 28, 2002. Installation of a thrust reverser with the TRAS lock installed and reactivation of the thrust reverser must be accomplished within the time constraints specified in the MMEL.

Alternative Methods of Compliance

(h)(1) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

(2) Alternative methods of compliance, approved previously in accordance with AD 2000-09-03, amendment 39-11711, are not considered to be approved as alternative methods of compliance with this AD.

Note 4:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permits

(i) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Appendix 1.—Thrust Reverser CDU Cone Brake Test

1. This procedure contains steps to do a check of the holding torque of the CDU cone brake.

2. CDU cone brake check (Figure 1):

A. Prepare to do the check:

(1) Open the fan cowl panels.

(2) Pull up on the manual release handle to unlock the electro-mechanical brake.

(3) Pull the manual brake release lever on the CDU to release the cone brake.

Note:

This will release the pre-load tension that may occur during a stow cycle.

(4) Return the manual brake release lever to the locked position to engage the cone brake.

(5) Remove the two bolts that hold the lockout plate to the CDU and remove the lockout plate.

(6) Install a 1/4-inch drive and a dial-type torque wrench into the CDU drive pad.

Caution: Do not use more than 100 pound-inches of torque when you do this check. Excessive torque will damage the CDU.

(7) Turn the torque wrench to try to manually extend the translating cowl until you get at least 15 pound-inches.

Note:

The cone brake prevents movement in the extend direction only. If you try to measure the holding torque in the retract direction, you will get a false reading.

(8) If the torque is less than 15 pound-inches, you must replace the CDU.

(9) Reinstall the lockout plate.

B. Return the airplane to its usual condition:

(1) Fully retract the thrust reverser (unless already accomplished).

(2) Pull down on the manual release handle on the electro-mechanical brake until the handle fully engages the retaining clip (unless already accomplished).

Note:

This will lock the electro-mechanical brake.

(3) Close the fan cowl panels.

Issued in Renton, Washington, on January 23, 2003.

Vi L. Lipski,

Manager, Transport Airplane Directorate, Aircraft Certification Service.