Source: https://www.federalregister.gov/documents/2002/08/30/02-22131/airworthiness-directives-boeing-model-777-series-airplanes
Timestamp: 2017-08-16 23:02:06
Document Index: 293481066

Matched Legal Cases: ['art 1', 'art 1', 'art 1', 'art 1', 'art 2', 'art 2', 'art 2', 'art 2', 'art 1', 'art 1', 'art 1', 'art 2']

67 FR 55737
Docket No. 2002-NM-64-AD
02-22131
Differences Between Service Information and This Proposed AD
One-Time Inspection/Review of Maintenance Records
Credit for Actions Accomplished per Previous Revisions of Service Bulletin
https://www.federalregister.gov/d/02-22131 https://www.federalregister.gov/d/02-22131
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 777 series airplanes. This proposal would require either a one-time inspection or a review of the airplane maintenance records for both stabilizer trim control modules (STCM) of the trim system of the horizontal stabilizer to determine if STCMs having certain serial numbers are installed; and follow-on corrective actions, if necessary. This proposal also would require eventual replacement of affected STCMs with new or reworked STCMs, which would terminate the follow-on actions. This action is necessary to prevent an uncommanded stabilizer trim due to simultaneous failure of two static seals on one STCM, combined with failure of the automatic shutdown function of the stabilizer trim system. Such failures could result in loss of pitch control and consequent loss of control of the airplane. This action is intended to address the identified unsafe condition.
Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-64-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 (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2002-NM-64-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.
Technical Information: Kenneth J. Fairhurst, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1118; fax (425) 227-1181.
Other Information: Sandy Carli, Airworthiness Directive Technical Editor/Writer; telephone (425) 687-4243, fax (425) 227-1232. Questions or comments may also be sent via the Internet using the following address: sandi.carli@faa.gov. Questions or comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.
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-64-AD.” The postcard will be date stamped and returned to the commenter.
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. Start Printed Page 557382002-NM-64-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
The FAA has received a report of an uncommanded stabilizer trim on a Boeing Model 777 series airplane that occurred on the ground. The leading edge of the horizontal stabilizer moved fully up, which would have resulted in a pitch command in the nose-down direction during flight. Investigation revealed that two seals on one stabilizer trim control module (STCM) of the trim system of the horizontal stabilizer had failed. An error in manufacturing the metal adjacent to the seals in the STCM caused the failures.
The STCM has a dual-valve design that requires simultaneous arm and control valve motion to create a stabilizer trim command. A single STCM seal failure can cause a single uncommanded valve motion, resulting in inoperative stabilizer trim in the airplane nose-up direction. Two STCM seal failures can cause two valves to move, resulting in an uncommanded stabilizer trim in the airplane nose-down direction. The stabilizer trim system includes a protective monitoring-and-shutdown function to detect and stop uncommanded stabilizer motion using a motor-operated shutoff valve to block hydraulic pressure supplied to the STCM. An uncommanded stabilizer trim due to simultaneous failure of two STCM seals and the automatic shutdown function of the stabilizer trim system could result in loss of pitch control and consequent loss of control of the airplane.
The FAA has reviewed and approved Boeing Service Bulletin 777-27A0047, Revision 2, dated October 11, 2001, which describes procedures for examination of both STCMs of the trim system of the horizontal stabilizer to identify affected serial numbers (S/N) and follow-on corrective actions, if necessary.
If any affected serial number is found, Part 1 of the Work Instructions describes procedures for repetitive functional tests to verify proper functioning of the stabilizer trim system of the horizontal stabilizer, including the automatic shutdown function of the stabilizer trim system. Part 1 also includes expanded instructions on how to conduct the test and interpret the results, as follows:
If the functional test results indicate a test condition of “FAILED” or if the stabilizer does not move, the service bulletin specifies correcting the fault or cause of the condition, and repeating the functional test.
Before returning the airplane to service, the functional test must have passed per Part 1.A.1. of the service bulletin, or the stabilizer trim system must be serviceable per Part 1.A.5.a. of the service bulletin.
Part 2 of the Work Instructions describes procedures for identification and removal of STCMs having S/N 6 through 549 inclusive, and replacement with new or reworked STCMs. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.
Boeing Service Bulletin 777-27A0047, Revision 2, references MOOG Aircraft Group Service Bulletin 160300-27-124, Revision 1, dated August 24, 2000, as the source of service information for changing and marking (reworking) the removed STCM units for installation on an airplane. The service bulletin also references certain chapters of the Boeing 777 Airplane Maintenance Manual for procedures for certain corrective actions.
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 require accomplishment of the actions specified in the Boeing service bulletin described previously, except as discussed below.
The effectivity of Boeing Service Bulletin 777-27A0047 identifies only Model 777-200 and 300 series airplanes having line numbers 2 through 266 and 273, excluding line numbers 256, 258, and 260 through 263 inclusive, as being subject to the service bulletin, but we have determined that the proposed AD applies to all Model 777 series airplanes. The subject STCMs are line-replaceable units and may have been installed on other airplanes not included in the effectivity in the service bulletin. This proposed AD requires that all Model 777 series airplanes be inspected for STCMs having the serial numbers specified in the service bulletin.
Although the service bulletin does not specify a records review, this proposed AD requires, as the initial action, doing a one-time general visual inspection or reviewing the airplane maintenance records to determine if STCMs having the serial numbers specified in Part 2 of the Work Instructions of the service bulletin are installed (Part 2 identifies the serial numbers of the STCMs that are to be removed) within 30 days after the effective date of this AD. The functional test and follow-on corrective actions specified in the service bulletin, would be required on airplanes with the affected STCMs installed within 150 flight hours after doing the inspection or review. Note 2 of this proposed AD defines a general visual inspection.
There are approximately 404 airplanes of the affected design in the worldwide fleet. The FAA estimates that 131 airplanes of U.S. registry would be affected by this proposed AD.
It would take approximately 1 work hour per airplane to accomplish the proposed inspection/review, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection/review proposed by this AD on U.S. operators is estimated to be $7,860, or $60 per airplane.
Should an operator be required to do the functional test, it would take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the functional test proposed by this AD on U.S. operators is estimated to be $60 per airplane, per test cycle.
Should an operator be required to do the replacement, it would take approximately 3 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would be provided by the vendor at no cost to operators. Based on these figures, the cost impact of the replacement proposed by this AD on U.S. operators is estimated to be $180 per airplane.
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 Start Printed Page 55739power and responsibilities among the various levels of government. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.
Boeing: Docket 2002-NM-64-AD.
Applicability: All Model 777 series airplanes, certificated in any category.
To prevent an uncommanded stabilizer trim due to simultaneous failure of two static seals on one stabilizer trim control module (STCM) combined with failure of the automatic shutdown function of the stabilizer trim system, which could result in loss of pitch control and consequent loss of control of the airplane, accomplish the following:
(a) Within 30 days after the effective date of this AD: Do either a one-time general visual inspection or a review of the airplane maintenance records of both STCMs of the trim system of the horizontal stabilizer to determine the serial numbers (S/N), per Part 2 of the Work Instructions of Boeing Service Bulletin 777-27A0047, Revision 2, dated October 11, 2001. If any affected S/N (6 through 556 inclusive) is found on either STCM, within 150 flight hours after doing the inspection or review, do the actions specified in either paragraph (a)(1) or (a)(2) of this AD. If no affected serial number is found, no further action is required by this AD.
(1) Do a functional test of the trim system of the horizontal stabilizer per Part 1 of the Work Instructions of the service bulletin.
(i) If a test condition of PASSED is reported per Part 1.A.1. of the service bulletin, or considered serviceable per Part 1.A.5.a. of the service bulletin, repeat the test at least every 150 flight hours until the terminating action required by paragraph (b) of this AD is done.
(ii) If a test condition of FAILED is reported, or if the stabilizer does not move, correct the condition as specified in the Boeing 777 Airplane Maintenance Manual, and repeat the functional test at least every 150 flight hours until the terminating action specified in paragraph (b) of this AD is done. If failure of either STCM is found during the test, before further flight, replace the affected STCM with a new or reworked STCM as required by paragraph (b) of this AD.
(2) Replace any affected STCM with a new or reworked STCM as required by paragraph (b) of this AD.
(b) Except as provided by paragraphs (a)(1)(ii) and (a)(2) of this AD: Within 2 years after the effective date of this AD, replace any STCM having an affected serial number identified in paragraph (a) of this AD with a new or reworked (modified and marked with an “R” suffix) STCM per Part 2 of the Work Instructions of Boeing Service Bulletin 777-27A0047, Revision 2, dated October 11, 2001. Such replacement ends the repetitive functional tests required by paragraph (a)(1) of this AD.
(c) Replacement of affected STCMs before the effective date of this AD per Boeing Service Bulletin 777-27A0047, dated September 21, 2000; or Revision 1, dated November 2, 2000; is considered acceptable for compliance with paragraph (b) of this AD.
(d) As of the effective date of this AD, no person may install on any airplane a STCM having S/N 6 through 556 inclusive.
(e) 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). 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.
(f) 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, provided there has been no known failure of any STCM during any functional test required by paragraph (a)(1) of this AD.
Issued in Renton, Washington, on August 22, 2002.
[FR Doc. 02-22131 Filed 8-29-02; 8:45 am]