Airworthiness directives: Boeing,
[Federal Register: June 22, 1999 (Volume 64, Number 119)]
[Proposed Rules]
[Page 33229-33232]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr22jn99-28]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-252-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747-400 Series Airplanes
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 all Boeing Model 747-400 series airplanes, that currently requires various inspections and functional tests to detect discrepancies of the thrust reverser control and indication system, and correction of any discrepancy found. This action would reduce the repetitive interval for one certain functional test. This proposal is prompted by reports indicating that several center drive units (CDU) were returned to the manufacturer of the CDU's because of low holding torque of the CDU cone brake. The actions specified by the proposed AD 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.
DATES: Comments must be received by August 6, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-252-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays.
The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.
FOR FURTHER INFORMATION CONTACT: Holly Thorson, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1357; fax (425) 227-1181.
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 notice may be changed in light of the comments received.
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 filedin the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 98-NM-252-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. 98-NM-252-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
Discussion
On July 13, 1994, the FAA issued AD 94-15-05, amendment 39-8976 (59 FR 37655, July 25, 1994), applicable to all Boeing Model 747-400 series airplanes, to require various inspections and functional tests of the thrust reverser control and indication system, and correction of any discrepancy found. That action was prompted by an investigation to determine the controllability of Model 747 series airplanes following an in-flight thrust reverser deployment, which revealed that, in the event of thrust reverser deployment during high-speed climb or during cruise, these airplanes could experience control problems. The requirements of that AD 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
Since the issuance of that AD, the FAA has received reports indicating that several thrust reverser center drive units (CDU) were returned to the manufacturer of the CDU's because of low holding torque of the CDU cone brake. This possible failure condition was not included in any previous safety assessment of the thrust reverser by the manufacturer. The returned CDU's had accumulated between 3,400 and 3,600 total flight hours. The cause of the low holding torque is a combination of cone brake wear, overrunning clutch wear, and grease contamination of the cone brake. Such a low torque condition could result in failure of the cone brake of the CDU, which could disable one of the fail safe features of the thrust reverser system that prevent deployment of a thrust reverser during flight.
In addition, this proposed AD changes the acceptable revision levels for Boeing Service Bulletin 747-78A2113, from the original issue, dated November 11, 1993, and Revision 1, dated March 10, 1994, referenced in AD 94-15-05 as the appropriate source of service information for accomplishment of the actions, to Revision 2, dated June 8, 1993 and Revision 3, dated September 11, 1997. Revisions 2 and 3 of the service bulletin incorporate substantial technical changes. These revisions reduce the permitted resistance from 5.0 ohm to 4.0 ohm in the directional control valve hot short protection check, which ensures that the related circuit breaker will open if a hot short occurs. These revisions also add a step to
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replace the bullnose seal in the next 650 flight hours if damage of more than 1 inch, but less than 10 inches is found during the bullnose seal inspection.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Service Bulletin 747- 78A2166, Revision 1, dated October 9, 1997, which describes procedures for a repetitive functional test of the CDU cone brake on each thrust reverser, and correction of any discrepancy found. The procedures for the functional test of the cone brake are essentially the same as those described in Boeing Service Bulletin 747-78-2113, dated November 11, 1993, and Boeing Alert Service Bulletin 747-78A2113, Revision 1, dated March 10, 1994, for Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines (which were referenced as appropriate sources of service information in AD 94-15-05). However, Boeing Service Bulletin 747-78A2166, Revision 1, specifies a shorter repetitive interval for the functional test (650 flight hours) than was specified in Boeing Service Bulletin 747-78-2113 (1,000 flight hours).
In addition, the FAA has reviewed and approved Boeing Service Bulletins 747-78-2113, Revision 2, dated June 8, 1995, and Revision 3, dated September 11, 1997. The procedures for the functional test of the cone brake are essentially the same as those described in Boeing Service Bulletin 747-78-2113, dated November 11, 1993, and Boeing Alert Service Bulletin 747-78A2113, Revision 1, dated March 10, 1994, referenced previously, for Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines.
Accomplishment of the actions specified in the service bulletins is intended to adequately address the identified unsafe condition.
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 94-15-05 to continue to require various inspections and functional tests to detect discrepancies of the thrust reverser control and indication system, and correction of any discrepancy found. This proposed AD would reduce the repetitive interval for the functional test of the CDU cone brake. The actions would be required to be accomplished in accordance with the service bulletins described previously, except as discussed below.
Differences Between Latest Service Bulletin and This Proposed AD
Operators should note that Boeing Service Bulletin 747-78A2166, Revision 1, specifies that the functional test of the CDU cone brake described in that service bulletin is not necessary for Model 747-400 series airplanes that are equipped with thrust reversers modified in accordance with Boeing Service Bulletin 747-78-2151 (or production equivalent). Boeing Model 747-400 series airplanes having line numbers 1061 and higher are equipped with such modified thrust reversers; therefore, the effectivity listing of Boeing Service Bulletin 747- 78A2166, Revision 1, includes only Model 747 series airplanes equipped with General Electric Model CF6-80C2 engines having line numbers 679 through 1060 inclusive.
This proposed AD, however, would require that the cone brake functional test be performed on Model 747-400 series airplanes equipped with General Electric Model CF6-80C2 engines regardless of whether they are equipped with thrust reversers modified in accordance with Boeing Service Bulletin 747-78-2151. The FAA has determined that an inspection interval of 1,000 hours time-in-service (which was required by AD 94- 15-05) provides a sufficient level of safety for the modified thrust reversers, and that an inspection interval of 650 hours time-in-service provides a sufficient level of safety for the unmodified thrust reversers, given the low holding torque condition that has been identified for the CDU cone brake.
Interim Action
This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking.
Cost Impact
There are approximately 146 Model 747-400 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 55 airplanes of U.S. registry would be affected by this proposed AD.
The new actions proposed by this AD would not add any additional economic burden on affected operators, other than the costs that are associated with repeating the functional test of the cone brake at reduced intervals (at intervals not to exceed 650 hours time-in-service for thrust reversers that have not been modified). The current costs associated with AD 94-15-05 are reiterated in their entirety (as follows) for the convenience of affected operators.
For airplanes powered by Pratt & Whitney PW4000 series engines (39 U.S.-registered airplanes), the actions that are currently required by AD 94-15-05, and retained in this AD, take approximately 48 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 of Model 747-400 series airplanes powered by Pratt & Whitney PW4000 series engines is estimated to be $112,320, or $2,880 per airplane.
For airplanes powered by General Electric CF6-80C2 series engines (16 U.S.-registered airplanes), the actions that are currently required by AD 94-15-05, and retained in this AD, take approximately 60 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 of Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines is estimated to be $57,600, or $3,600 per airplane.
The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.
Currently, there are no Model 747-400 series airplanes powered by Rolls-Royce RB211-524G/H series engines on the U.S. Register at this time. However, should one of these airplanes be imported and placed on the U.S. Register in the future, it will require approximately 30 hours to accomplish the required actions, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this AD is estimated to be $1,800 per airplane.
Regulatory Impact
The regulations proposed herein would not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this proposed regulation (1) is not a ``significant regulatory action''
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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
-
The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
-
Section 39.13 is amended by removing amendment 39-8976 (59 FR 37655, July 25, 1994), and by adding a new airworthiness directive (AD), to read as follows:
Boeing: Docket 98-NM-252-AD. Supersedes AD 94-15-05, Amendment 39- 8976.
Applicability: All Model 747-400 series airplanes, 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 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, accomplish the following:
Restatement of Requirements of AD 94-15-05, Amendment 39-8976
Inspections and Tests
(a) For Model 747-400 series airplanes powered by Pratt & Whitney PW4000 series engines: Accomplish paragraphs (a)(1) and (a)(2) of this AD.
(1) Within 90 days after August 24, 1994 (the effective date of AD 94-15-05, amendment 39-8976), perform an inspection to detect damage to the bullnose seal on the translating sleeve of the thrust reverser, and perform a test of the lock mechanism of the center locking actuator, in accordance with paragraphs III.C. and III.E. of the Accomplishment Instructions of Boeing Service Bulletin 747-78- 2112, dated November 11, 1993; or paragraphs III.E. and III.H. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2112, Revision 1, dated March 7, 1994. Repeat this inspection and test thereafter at intervals not to exceed 1,000 hours time-in- service.
(2) Within 9 months after August 24, 1994, perform inspections and functional tests of the thrust reverser control and indication systems in accordance with paragraphs III.A., III.B., III.D., and III.F. through III.M. of the Accomplishment Instructions of Boeing Service Bulletin 747-78-2112, dated November 11, 1993; or paragraphs III.C., III.D., III.F., III.G., and III.I. through III.P. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747- 78A2112, Revision 1, dated March 7, 1994. Repeat these inspections and functional tests thereafter at intervals not to exceed 18 months.
Inspections and Tests
(b) For Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines: Accomplish paragraphs (b)(1) and (b)(2) of this AD.
(1) Within 90 days after August 24, 1994, perform an inspection to detect damage to the bullnose seal on the translating sleeve of the thrust reverser, and a continuity test of the position switch module of the center drive unit (CDU) and a cone brake test of the CDU, in accordance with paragraphs III.B. and III.C. of the Accomplishment Instructions of Boeing Service Bulletin 747-78-2113, dated November 11, 1993; or paragraphs III.E. through III.G. of Boeing Alert Service Bulletin 747-78A2113, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-78-2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997. Repeat the inspection and tests thereafter at intervals not to exceed 1,000 hours time-in-service.
(2) Within 9 months after August 24, 1994, perform inspections and functional tests of the thrust reverser control and indication systems in accordance with paragraphs III.A., III.D., III.F., III.G., III.H., and III.J. through III.M. of the Accomplishment Instructions of Boeing Service Bulletin 747-78-2113, dated November 11, 1993; or paragraphs III.D. and III.H. through III.N. of Boeing Alert Service Bulletin 747-78A2113, Revision 1, dated March 10, 1994; or Boeing Service Bulletin 747-78-2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997. Repeat these inspections and functional tests thereafter at intervals not to exceed 18 months.
Inspections and Tests
(c) For Model 747-400 series airplanes powered by Rolls-Royce RB211-524G/H series engines: Within 9 months after August 24, 1994, and thereafter at intervals not to exceed 18 months, perform inspections and functional tests of the thrust reverser control and indication systems in accordance with paragraphs III.D. through III.K. of the Accomplishment Instructions of Boeing Service Bulletin 747-78-2115, dated October 28, 1993; or paragraphs III.D. through III.L. of the Accomplishment Instructions of Boeing Alert Service Bulletin 747-78A2115, Revision 1, dated March 4, 1994.
Corrective Action
(d) If any of the inspections and/or functional tests required by this AD cannot be successfully performed, or if any discrepancy is found during those inspections and/or functional tests, accomplish either paragraph (d)(1) or (d)(2) of this AD.
(1) Prior to further flight, correct the discrepancy found, in accordance with Boeing Service Bulletin 747-78-2112, dated November 11, 1993, or Boeing Alert Service Bulletin 747-78A2112, Revision 1, dated March 7, 1994 (for Model 747-400 series airplanes powered by Pratt & Whitney PW4000 series engines); Boeing Service Bulletin 747- 78-2113, dated November 11, 1993, or Boeing Alert Service Bulletin 747-78A2113, Revision 1, dated March 10, 1994, or Boeing Service Bulletin 747-78-2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997 (for Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines); or Boeing Service Bulletin 747-78-2115, dated October 28, 1993, or Boeing Alert Service Bulletin 747-78A2115, Revision 1, dated March 4, 1994 (for Model 747-400 series airplanes powered by Rolls-Royce RB211-524G/H series engines); as applicable. Or
(2) The airplane may be operated in accordance with the provisions and limitations specified in an 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
Functional Tests
(e) For Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines: Within 1,000 hours time-in-service after the most recent test of the CDU cone brake performed in accordance with paragraph (a) of this AD, or within 650 hours time- in-service after the effective date of this AD, whichever occurs first, perform a functional test to detect discrepancies of the CDU cone brake on each thrust reverser, in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997; or the applicable section of paragraph III.A. of the Accomplishment Instructions of Boeing Service Bulletin 747-78-2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997.
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(1) For Model 747-400 series airplanes having line numbers 679 through 1060 inclusive, equipped with thrust reversers that have not been modified in accordance with Boeing Service Bulletin 747-78- 2151: Repeat the functional test of the CDU cone brake thereafter at intervals not to exceed 650 hours time-in-service.
(2) For Model 747-400 series airplanes having line numbers 1061 and higher, equipped with thrust reversers that have been modified in accordance with Boeing Service Bulletin 747-78-2151: Repeat the functional test of the CDU cone brake thereafter at intervals not to exceed 1,000 hours time-in-service.
Terminating Action
(f) Accomplishment of the functional test of the CDU cone brake, as specified in paragraphs (e)(1) and (e)(2) of this AD, as applicable, constitutes terminating action for the repetitive tests of the CDU cone brake required by paragraph (b)(1) of this AD.
Corrective Action
(g) If any functional test required by paragraph (d) of this AD cannot be successfully performed, or if any discrepancy is found during any functional test required by paragraph (d) of this AD, accomplish either paragraph (g)(1) or (g)(2) of this AD.
(1) Prior to further flight, correct the discrepancy found, in accordance with Boeing Service Bulletin 747-78A2166, Revision 1, dated October 9, 1997; or Boeing Service Bulletin 747-78-2113, Revision 2, dated June 8, 1995, or Revision 3, dated September 11, 1997. Or
(2) The airplane may be operated in accordance with the provisions and limitations specified in the operator's FAA-approved MEL, provided that no more than one thrust reverser on the airplane is inoperative.
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, Transport Airplane Directorate. 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.
(h)(2) Alternative methods of compliance for Model 747-400 series airplanes powered by General Electric CF6-80C2 series engines, approved previously in accordance with AD 94-15-05, amendment 39-8976, are not considered to be approved as alternative methods of compliance with this AD.
Note 2: 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.
Issued in Renton, Washington, on June 15, 1999. Dorenda D. Baker, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 99-15774Filed6-21-99; 8:45 am]
BILLING CODE 4910-13-P
