[Federal Register Volume 59, Number 141 (Monday, July 25, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-17593]
[[Page Unknown]]
[Federal Register: July 25, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-07-AD; Amendment 39-8976; AD 94-15-05]
Airworthiness Directives; Boeing Model 747-400 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment adopts a new airworthiness directive (AD),
applicable to all Boeing Model 747-400 series airplanes, that requires
various inspections and functional tests of the thrust reverser control
and indication system, and correction of any discrepancy found. This
amendment is prompted by an investigation to determine the
controllability of Model 747 series airplanes following an in-flight
thrust reverser deployment, which has revealed that, in the event of
thrust reverser deployment during high-speed climb or during cruise,
these airplanes could experience control problems. The actions
specified by this 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: Effective August 24, 1994.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of August 24, 1994.
ADDRESSES: The service information referenced in this AD may be
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,
Washington 98124-2207. This information may be examined at the Federal
Aviation Administration (FAA), Transport Airplane Directorate, Rules
Docket, 1601 Lind Avenue SW., Renton, Washington; or at the Office of
the Federal Register, 800 North Capitol Street NW., suite 700,
Washington, DC.
FOR FURTHER INFORMATION CONTACT: Jon Regimbal, Aerospace Engineer,
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate,
Seattle Aircraft Certification Office, 1601 Lind Avenue SW., Renton,
Washington 98055-4056; telephone (206) 227-2687; fax (206) 227-1181.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) to include an airworthiness
directive (AD) that is applicable to all Boeing Model 747-400 series
airplanes was published in the Federal Register on March 4, 1994 (59 FR
10336). That action proposed to require various inspections and
functional tests of the thrust reverser control and indication system,
and correction of any discrepancy found. -
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received. -
One commenter supports the proposed rule. -
The Air Transport Association (ATA) of America, on behalf of one of
its members, requests that the proposed repetitive inspections and
tests be withdrawn since those actions will be added to the revised
Maintenance Planning Document. The ATA acknowledges that the proposed
repetitive actions may not be incorporated uniformly into every
operator's maintenance program unless an AD is issued. Therefore, the
ATA asks that another provision be added to the proposal as follows:
Within 3 months after the effective date of the AD, revise the FAA-
approved maintenance inspection program to include a functional test of
the thrust reverser control and indication system at an initial 15-
month interval. Inspections for damage to the bullnose seal would be
conducted at an initial 1,500 flight hour interval. The AD would no
longer be applicable for operators that have acceptably revised the
maintenance program. Operators complying with this paragraph could use
an alternative recordkeeping method in lieu of that required by section
91.417 or 121.380 of the Federal Aviation Regulations (14 CFR 91.417 or
121.380). The FAA would be defined as the cognizant Principal
Maintenance Inspector (PMI) for operators electing this alternative.
The ATA believes that its suggestion should be adopted because the
proposed repetitive actions will likely continue for as long as Model
747-400 series airplanes are operated. The ATA acknowledges that, while
numerous AD's that require repetitive inspections continue for the life
of the aircraft, it has either been shown that a satisfactory
terminating action has not been developed or that service experience
has shown that control of the inspections cannot be administered safely
through an operator's maintenance program. The ATA states that its
proposal is intended to minimize the impact of the AD process on an
operator's maintenance program and cites other AD's that contain
provisions similar to its proposal.
The FAA recognizes the ATA's concerns regarding the requirement for
repetitive inspections and tests of the thrust reverser control and
indication systems. However, the FAA finds that this requirement is
necessary in order to provide an adequate level of safety by addressing
the specified unsafe condition. Further, the FAA determined the
required repetitive intervals based on the service history of similar
components and on an analysis of the system design to predict the
reliability of the system during the service life of the aircraft.
Lengthening these intervals would only be appropriate when a sufficient
sample of systems is allowed to operate through an entire system
overhaul cycle; adjustments made prior to that time may not account for
the effects of age and wear.
The FAA finds that addressing inspections and tests of the thrust
reverser control and indication systems in a document that is not FAA-
approved, such as a Maintenance Planning Document, will not ensure an
acceptable level of safety with regard to the thrust reverser system.
The ATA's suggested provision for accomplishment of the inspections and
tests would permit each operator to determine whether and how often
these actions should be conducted. In light of the severity of the
unsafe condition, however, the FAA has determined that allowing this
degree of operator discretion is not appropriate at this time.
Therefore, this AD is necessary to ensure that operators accomplish the
repetitive actions in a common manner and at common intervals.
One commenter requests that the proposed compliance time for the
initial inspections and functional tests of the thrust reverser control
and indication systems be extended from 6 to 12 months. This commenter
offers no justification for the request. A second commenter indicates a
false impression that a 12-month compliance time was proposed for these
inspections and functional tests, and requests that the compliance time
be expressed in terms of maintenance checks (specifically, ``C''
checks) or 15 months to coincide with regularly scheduled maintenance.
(The FAA notes that no 12-month compliance time is specified for any
requirement contained in the proposal.) Another commenter requests that
the compliance times be specified in terms of maintenance check
intervals (``A'' checks, ``C'' checks, etc.). The commenter provides no
justification for this request.
The FAA concurs partially. Since only two comments were received in
response to the proposed 6-month compliance time, the FAA assumes that
most operators are able to accommodate that proposed compliance time.
In light of safety considerations, the FAA finds that a short initial
compliance time for the inspections and functional tests is warranted.
However, upon reconsideration, the FAA considers that extending the
proposed compliance time by 3 additional months will not adversely
affect safety, and will allow the required actions to be performed at a
base during regularly scheduled maintenance where special equipment and
trained maintenance personnel will be available, if necessary.
Paragraphs (a)(2), (b)(2), and (c) of the final rule have been revised
to specify a compliance time of 9 months for the initial inspections
and functional tests of the thrust reverser control and indication
systems.
The FAA does not agree that the compliance times specified in the
final rule should be expressed in terms of maintenance check intervals.
Since maintenance schedules vary from operator to operator, there would
be no assurance that the actions will be accomplished during those
maximum intervals. The FAA has determined that the compliance times, as
specified in the final rule, represent the maximum intervals of time
allowable for the affected airplanes to continue to operate prior to
accomplishing the required actions without compromising safety.
Several commenters request that the proposed compliance time for
repetitive inspections and functional tests of the thrust reverser
control and indication systems [specified in paragraphs (a)(2), (b)(2),
and (c) of the proposal] be extended from the proposed 15-month
intervals to accommodate current or future scheduled ``C'' check
maintenance intervals. Two commenters propose extension of the
compliance time to 18-month intervals. One commenter indicates that
Boeing Alert Service Bulletin 747-78A2115, Revision 1, dated March 10,
1994, recommends inspection intervals of 15 months or 5,000 flight
hours.
The FAA concurs partially. As discussed previously, the FAA does
not agree that these compliance times should be expressed in terms of
maintenance check intervals. However, the FAA does concur with the
commenters' requests to extend the proposed compliance time to 18
months. Extending the compliance time by 3 additional months will not
adversely affect safety, and will allow the inspections and tests to be
performed at a base during regularly scheduled maintenance where
special equipment and trained maintenance personnel will be available,
if necessary. Paragraphs (a)(2), (b)(2), and (c) of the final rule have
been revised to specify a compliance time of 18 months for repetitive
inspections and functional tests of the thrust reverser control and
indication systems.
Several commenters request that paragraph (d) of the proposed rule
be revised to allow dispatch with a thrust reverser inoperative in
accordance with the FAA-approved Master Minimum Equipment List (MMEL)
if any discrepancy is found during the required inspections and tests.
Several commenters point out that allowing dispatch with a thrust
reverser inoperative will provide operators time to obtain parts and
perform any necessary corrective action. One commenter explains that,
without this change, the dispatch capability of the airplane would be
downgraded for problems such as proximity sensor adjustments or auto
restow chafing, which are not related to the integrity of the stow lock
feature. One commenter requests 14-day dispatch relief.
The FAA concurs partially. The FAA agrees that an option for
dispatch relief may be allowed in accordance with an operator's FAA-
approved Minimum Equipment List (MEL). However, the FAA does not concur
with the commenter's request for 14-day dispatch relief, since the MMEL
specifies 10-day dispatch relief. The FAA has revised paragraph (d) of
the final rule to provide an alternative for an airplane to be operated
in accordance with existing provisions and limitations specified in the
MEL, provided that no more than one thrust reverser on the airplane is
inoperative. -Three commenters request that the proposed interval of
1,000 hours time-in-service for repetitive inspections of the bullnose
seal and tests of the lock mechanism and of the position switch module
and cone brake be extended to coincide with operators' scheduled
maintenance intervals and to reduce the economic impact of the proposed
actions. One commenter suggests a repetitive interval of 1,300 hours
time-in-service. The second commenter proposes that the interval be
extended to 1,500 hours time-in-service. The third commenter recommends
that these actions be required every 15 months or during ``C'' checks.
The FAA does not concur. The FAA based the repetitive inspection
interval on data obtained from a reliability analysis submitted by
Boeing prior to the issuance of the proposed rule. The FAA based the
proposed interval of 1,000 hours time-in-service on that analysis and
on the fact that affected operators conduct ``A'' checks at intervals
of approximately 450 hours time-in-service. The FAA's intent was that
the proposed inspections and tests be conducted during every other
regularly scheduled ``A'' check, when the airplanes would be located at
a base where special equipment and trained personnel would be readily
available, if necessary. Further, the FAA has received no supporting
technical analysis to supplement or refute the manufacturer's original
reliability analysis. The FAA has determined that the compliance time,
as proposed, represents the maximum interval of time allowable for the
affected airplanes to accomplish the required repetitive actions
without compromising safety.
One commenter requests that a statement be added to the proposed
rule to indicate that the AD is considered to be interim action. The
FAA acknowledges that this AD is interim action, as specified in the
preamble to the proposed rule. The manufacturer has advised that it
currently is developing a modification that will positively address the
unsafe condition addressed by this AD, and that the modification should
be available within approximately 24 months. Once this modification is
developed, approved, and available, the FAA may consider additional
rulemaking.
One commenter requests that the proposal be revised to require that
operators report results from all inspections and tests, rather than
only initial inspections and tests, and that these results be used to
justify adjustments of inspection intervals or cancellation of
inspections. The commenter offers no justification for this request.
The FAA does not concur. The FAA is interested in the initial
inspection results for the purpose of determining the present state of
thrust reverser systems throughout the fleet. Since the actions
required by this AD are considered to be interim action and terminating
action is imminent, the FAA finds that gathering information for the
purpose of adjusting inspection intervals and cancelling inspections is
not needed and would pose an unnecessary burden on operators.
One commenter requests that the FAA review the probability
calculations made by Boeing in determining that an unsafe condition
exists. The commenter states that if the probability of inadvertent
thrust reverser deployment is lower than 1 in 109 flight hours, an
AD would not be required. The commenter points out two factors that
would reduce controllability: deployment of an outboard thrust
reverser, and deployment of that reverser during climb. Neither of
these factors was accounted for in the probability study that Boeing
presented to the operators. In addition, for Model 747-400 series
airplanes equipped with General Electric CF6-80C2 engines, deployment
of a single thrust reverser sleeve half is possible, and deployment of
a single sleeve half was assumed to have the same effect on airplane
controllability as full (both halves) deployment of a thrust reverser.
The FAA does not concur. The analysis presented by Boeing to the
FAA states clearly that the effect of deployment of an inboard thrust
reverser, or the effect of deployment of a single outboard thrust
reverser sleeve, had not yet been quantified. At that time, Boeing and
the FAA recognized the need for further study. However, in light of the
experience gained during investigation of the accident discussed in the
preamble to the proposed rule, Boeing had identified design
deficiencies that needed to be addressed as soon as practicable to
ensure the safety of the Model 747 fleet. The FAA did not determine
that an AD was warranted solely on the basis that a particular
probability threshold of 1 in 109 flight hours had been exceeded.
Rather, the FAA based its determination on the fact that design
deficiencies exist that could lead to an unsafe condition (reduction in
or loss of controllability of the airplane), which can be compensated
for by periodic inspections and tests until a design change becomes
available.
Since the issuance of the proposal, Boeing has issued Revision 1 of
Boeing Alert Service Bulletins 747-78A2112, dated March 7, 1994; 747-
78A2113, dated March 10, 1994; and 747-78A2115, dated March 4, 1994.
(The original issues of these service bulletins were cited in the
proposal as the appropriate sources of service information.) These
alert service bulletin revisions reclassify the service bulletin type
from standard to alert, recommend certain revised compliance times to
coincide with operators' maintenance schedules, and revise certain test
procedures. The FAA has reviewed and approved these alert service
bulletins and has revised the final rule to reflect these latest
revisions as additional sources of service information. In addition,
the FAA has revised the final rule to specify the appropriate
paragraphs of the Accomplishment Instructions of these alert service
bulletins for performing the actions required by this AD.
After careful review of the available data, including the comments
noted above, the FAA has determined that air safety and the public
interest require the adoption of the rule with the changes previously
described. The FAA has determined that these changes will neither
increase the economic burden on any operator nor increase the scope of
the AD.
This is considered to be interim action until final action is
identified for these airplanes, at which time the FAA may consider
further rulemaking.
There are approximately 286 Model 747-400 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 39 Model
747-400 series airplanes powered by Pratt & Whitney PW4000 series
engines of U.S. registry will be affected by this AD, that it will take
approximately 48 work hours per airplane to accomplish the required
actions, and that the average labor rate is $55 per work hour. Based on
these figures, the total cost impact of the AD on U.S. operators of
Model 747-400 series airplanes powered by Pratt & Whitney PW4000 series
engines is estimated to be $102,960, or $2,640 per airplane.
The total cost impact figure discussed above is based on
assumptions that no operator has yet accomplished any of the
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
General Electric CF6-80C2 series engines on the U.S. Register. However,
should one of these airplanes be imported and placed on the U.S.
Register in the future, it will require approximately 60 work hours to
accomplish the required actions, at an average labor charge of $55 per
work hour. Based on these figures, the total cost impact of this AD is
estimated to be $3,300 per airplane.
Additionally, 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 charge of $55
per work hour. Based on these figures, the total cost impact of this AD
is estimated to be $1,650 per airplane.
The regulations adopted herein will 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 final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (1) is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is not a ``significant rule'' under 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. A final evaluation has been prepared for this action
and it is contained in the Rules Docket. A copy of it may be obtained
from the Rules Docket at the location provided under the caption
ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends 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. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
94-15-05 Boeing: Amendment 39-8976. Docket 94-NM-07-AD.
Applicability: All Model 747-400 series airplanes, certificated
in any category.
Compliance: Required as indicated, unless accomplished
previously.
To ensure the integrity of the fail safe features of the thrust
reverser system, accomplish the following:
(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 the effective date of this AD, 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 the effective date of this AD, 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.
(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 the effective date of this AD, 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. Repeat the inspection and tests thereafter at
intervals not to exceed 1,000 hours time-in-service.
(2) Within 9 months after the effective date of this AD, 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. Repeat these inspections and functional tests
thereafter at intervals not to exceed 18 months.
(c) For Model 747-400 series airplanes powered by Rolls-Royce
RB211-524G/H series engines: Within 9 months after the effective
date of this AD, 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.
(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 (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.
(e) Within 10 days after performing each initial inspection and
test required by this AD, submit a report of the inspection and/or
test results, both positive and negative, to the FAA, Seattle
Aircraft Certification Office (ACO), ANM-100S, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056; fax (206) 227-1181. Information
collection requirements contained in this regulation have been
approved by the Office of Management and Budget (OMB) under the
provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et
seq.) and have been assigned OMB Control Number 2120-0056.
(f) 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 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.
Note: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(g) 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.
(h) The actions shall be done in accordance with Boeing Service
Bulletin 747-78-2112, dated November 11, 1993; Boeing Alert Service
Bulletin 747-78A2112, Revision 1, dated March 7, 1994; Boeing
Service Bulletin 747-78-2113, dated November 11, 1993; Boeing Alert
Service Bulletin 747-78A2113, Revision 1, dated March 10, 1994;
Boeing Service Bulletin 747-78-2115, dated October 28, 1993; or
Boeing Alert Service Bulletin 747-78A2115, Revision 1, dated March
4, 1994; as applicable. This incorporation by reference was approved
by the Director of the Federal Register in accordance with 5 U.S.C.
552(a) and 1 CFR part 51. Copies may be obtained from Boeing
Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-
2207. Copies may be inspected at the FAA, Transport Airplane
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the
Office of the Federal Register, 800 North Capitol Street, NW., suite
700, Washington, DC.
(i) This amendment becomes effective on August 24, 1994.
Issued in Renton, Washington, on July 13, 1994.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-17593 Filed 7-22-94; 8:45 am]
BILLING CODE 4910-13-U