[Federal Register Volume 61, Number 190 (Monday, September 30, 1996)]
[Rules and Regulations]
[Pages 50995-50999]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-24650]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 95-NM-203-AD; Amendment 39-9771; AD 96-20-05]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 767 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 767 series airplanes, that requires
repetitive operational tests to verify proper deployment of the ram air
turbine
[[Page 50996]]
(RAT), and replacement of the rotary actuator motor with a new or
serviceable rotary actuator motor, if necessary. This amendment is
prompted by reports of corroded rotary actuator motors of the RAT found
on in-service airplanes. The actions specified by this AD are intended
to ensure that the RAT actuator motor is not corroded to the point
where it may result in the failure of the RAT to deploy and
subsequently result in loss of emergency hydraulic power to the flight
controls in the event that power is lost in both engines.
DATES: Effective November 4, 1996.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of November 4, 1996.
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: Sheila Kirkwood, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft
Certification Office, 1601 Lind Avenue, SW., Renton, Washington;
telephone (206) 227-2675; 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 767 series
airplanes was published in the Federal Register on March 21, 1996 (61
FR 11593). That action proposed to require repetitive operational tests
to verify proper deployment of the ram air turbine (RAT) system, and
replacement of the rotary actuator motor with a new or serviceable
rotary actuator motor, if necessary.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Support for the Proposal
One commenter supports the proposed rule.
Request To Revise Unsafe Condition Finding
One commenter, Boeing Commercial Airplane Group, requests that
certain language that appeared in the preamble to the notice, which
referred to the FAA's finding of an unsafe condition, be revised.
Specifically, the commenter requests that the wording be changed to
state that the addressed unsafe condition ``could exist,'' rather than
is ``likely to exist'' [on other airplanes of this same type design].
The commenter gives no particular justification for this request;
however, the FAA infers that, by changing this wording as suggested,
the commenter seeks to minimize the adverse implication regarding the
safety of its products.
The FAA does not concur. The phrasing used in that discussion is
not accidental. Part 39.1, ``Applicability,'' of the Federal Aviation
Regulations (FAR) (14 CFR 39.1) states:
This part prescribes airworthiness directives that apply to
aircraft * * * when--
(a) An unsafe condition exists in a product; and
(b) That condition is likely to exist or develop in other
products of the same type design.''
Therefore, the finding that the condition is ``likely to exist''
(or develop) is necessary to ensure that the AD falls within the scope
of part 39; its absence would arguably subject the FAA to legal
challenge for inappropriately using the AD process to issue rules that
do not meet the criteria for AD's. While it is understandable that a
manufacturer would like to minimize any adverse implications regarding
the safety of its products, the FAA reiterates that the purpose of an
AD is to correct an identified unsafe condition in aircraft, regardless
of where it is or what it is caused by. In essence, the AD serves to
protect the flying public from the consequences of the unsafe
condition. The AD also serves to protect the manufacturer from the
liability that would be faced should the unsafe condition not be
corrected.
Request To Clarify Description of Intent of the Rule
This same commenter requests that the description of the intent of
the rule, which appeared in the preamble to the notice, be changed so
that it is more accurate. The specific statement in the preamble
relevant to this issue indicated that the AD actions are:
Intended to prevent * * * corrosion, which could result in
failure of the RAT to deploy and subsequent loss of emergency
hydraulic power to the flight controls, in the event that power is
lost in both engines.
The commenter points out that the proposed operational tests will
help to ensure that the RAT motor is not heavily corroded, but the
tests will not prevent corrosion. The commenter suggests that the
language be revised to specify more accurately that the operational
tests:
* * * Will ensure that the RAT motor is not heavily corroded and
can deploy the RAT. The RAT must be able to be deployed to provide
emergency hydraulic power to the flight controls in the event that
power is lost in both engines.
The FAA partially agrees with this commenter's request.
First, the commenter is correct in pointing out that the required
operational tests will not prevent corrosion. The FAA has revised the
wording relative to this issue in the appropriate places in this final
rule.
Second, the FAA points out that the intent of the statement that
appeared in the preamble to the notice was to specify what unsafe
condition the requirements of the AD are addressing. The commenter's
suggested rewording (i.e., ``The RAT must be able to be deployed * *
*'') highlights the fact that there are pertinent sections of part 25
of the Federal Aviation Regulations (14 CFR part 25) which require that
the RAT be able to be deployed in order to provide emergency hydraulic
power to the flight controls. However, the language that is used in the
AD is formatted to highlight the unsafe condition that is created when
the failure of associated components in a system does not permit the
RAT to deploy as required. It is this concept that the statement of the
intent of the AD is meant to convey, not merely to restate the function
of a required system.
The FAA acknowledges that the statement could be clarified further,
however, and has revised the language in the appropriate portions of
this final rule to specify that the intent of the actions of this AD
is:
``* * * To ensure that the RAT actuator motor is not corroded to
the point where it may result in the failure of the RAT to deploy
and subsequently result in loss of emergency hydraulic power to the
flight controls in the event that power is lost in both engines.
Requests To Extend Compliance Time
Several commenters request that the proposal be revised to extend
the compliance time for the repetitive operational tests from the
proposed 1,000-flight hour intervals to as much as 3,000 flight hours
or 15 months, whichever occurs later. To justify this request, the
commenters point out the following issues:
1. The airframe manufacturer, Boeing, recommends a 3,000-flight
hour interval for repetitive tests.
[[Page 50997]]
2. One of the failed rotary actuator motors of the RAT that was
found in service was on a high-cycle airplane that was operated in a
high humidity, salt water environment. That type of environment is more
conducive to the initiation of corrosion, but is not the typical
environment in which the majority of affected airplanes are operated.
Further, these commenters state that, even though Boeing has advised
that recent high humidity tests have demonstrated that the subject
motor has a propensity to corrode under high humidity conditions,
affected operators are not seeing such results under field conditions.
While the conclusions drawn from reviewing results of the Boeing tests
may justify the FAA's adoption of the rule, the commenters request that
service experience be considered in determining an appropriate
compliance interval.
3. One affected operator states that it has accomplished roughly 90
deployment tests similar to the proposed test over a 9-year period and
there have been no reports of failure.
4. The proposed 1,000-flight hour interval would pose an
``unjustified economic burden on the affected operators,'' since it
does not take into account the necessary removal and return to service
of the motor, repetitive testing, and administrative costs to monitor
and schedule accomplishment of the tests for the remaining life of the
Model 767 fleet. The repetitive interval should be extended to coincide
with normally scheduled maintenance, so that special scheduling will be
unnecessary. An interval of 3,000-flight hours would be appropriate,
and would to ensure that any detrimental effect associated with
corrosion is identified.
5. An extension of the repetitive test interval to include both a
flight cycle threshold and a calendar time will address the FAA's
concern that the addressed problem is caused by exposure to high
cycling. This would also provide an acceptable level of safety without
overburdening operators who use their aircraft on longer stage lengths.
The FAA has considered this information presented by the
commenters, and agrees that the test interval can be revised somewhat.
The FAA concurs with the point that a calendar time interval is
appropriate since corrosion of the RAT actuator motor could occur while
the airplane is on the ground. In light of this, the FAA finds that
repetitive interval of 6 months will ensure that both long-range and
short-range airplanes, as well as those that are infrequently used,
will achieve the same level of safety with respect to the RAT deploy
system.
However, corrosion that occurs as a result of high-cycle use
(condensation due to thermal cycling) is also a concern; therefore, the
FAA maintains that the repetitive test interval cannot be based solely
on calendar time, but must be related to flight hours as well. Based on
recent test data presented by the manufacturer, as well as in-service
history, the FAA has determined that a repetitive interval of 3,000
flight hours is appropriate. This interval will also coincide with
regularly scheduled maintenance visits for most affected operators.
The final rule has been revised to specify that the repetitive
tests must be performed at intervals of 3,000 flight hours or 6 months,
whichever occurs first.
Request To Revise Description of Test Result Conditions
One commenter requests that the proposed rule be revised to clarify
the conditions for which the operational testing is performed. The
commenter maintains that the tests are actually deployment tests to
determine merely if the RAT deploys or if it does not. In light of
this, the commenter requests that paragraph (a)(1) be revised to state,
``If the RAT deploys * * *''; and that paragraph (a)(2) be revised to
state, ``If the RAT does not deploy * * *'' The commenter considers
this revised wording to be clearer than that which appeared in the
notice.
The FAA does not concur with the commenter's suggested changes, but
acknowledges that some clarification is warranted.
As for paragraph (a)(1), the intent of the test is that the RAT
deploy properly. Even the Boeing service bulletin containing the test
procedures, describes a successful test as one in which the RAT
``deploys correctly.'' The FAA finds that the quality of deployment
should be considered for this test. For example, a RAT could deploy,
but have some problems in doing so; in that case, the RAT should not be
considered to have deployed correctly. In light of this, and to
maintain standard terminology between the AD and the referenced service
bulletin, the FAA has revised paragraph (a)(1) to read, ``If the RAT
deploys correctly * * *''
As for paragraph (a)(2), the FAA finds that commenter's suggested
phrase, ``does not deploy,'' is not specific enough for determining the
test result. That language would not encompass deployments where the
RAT may get stuck in transit and may only partially deploy. However,
the FAA does consider that the language should be clarified on this
point and therefore, has revised the phrasing of paragraph (a)(2) to
read, ``If the RAT does not fully deploy * * *''
Request To Permit Use of ETOPS Program in Lieu of Rule Requirements
One commenter requests that the proposal be revised to allow
operators to rely on their approved Extended Range Twin-Engine
Operations (ETOPS) programs, in lieu of the AD requirements, as a means
to ensure the reliability of the RAT on each airplane. The commenter
considers that this approach takes into account individual operators'
operating environments and service experience. This commenter also
states that it has been accomplishing deployment tests ever since its
Model 767's went into service as part of the ETOPS program and, in
approximately 90 deployment tests accomplished over a period of 9
years, has had no reports of failure.
The FAA does not concur with the commenter's request. The
deployment tests that are performed as part of this commenter's ETOPS
program apparently entail the deployment of the RAT only every 10
months. As explained previously, the FAA has determined that repetitive
deployments must be performed every 6 months or 3,000 flight cycles,
whichever occurs first, in order to ensure that corrosion is detected
and corrected before it can lead to the problems that this AD
addresses.
Request To Give Credit for Testing Prior to Delivery
One commenter requests that the proposed rule be revised to give
credit to new airplanes on which a RAT system functional test, which
includes a manual RAT deployment test, is accomplished either in the
factory or on the flight line prior to delivery of the airplane.
The FAA concurs and has added a statement to the final rule to give
credit for such testing only as the initial test required by the AD.
However, all airplanes are subject to the repetitive tests.
Request To Reference Later Revisions of Cited Service Bulletin
Boeing requests that the proposed rule be revised to reference
Revision A of Boeing Alert Service Bulletin 767-29A0080 as the
appropriate source of service information. The commenter states that
this service bulletin, as yet unreleased, will clarify some of the RAT
manual deploy test and the RAT retraction procedures. It will also
[[Page 50998]]
contain additional information concerning corrective action if the RAT
manual deploy circuit breaker trips and there is no measured RAT down-
stop gap after deploying the RAT.
The FAA does not concur. The revision of the service bulletin that
the commenter refers to has not yet been issued, nor has it been
approved by the FAA.
Request To Clarify Background Information
One commenter requests that the description of the service history
prompting this AD action, as it appeared in the preamble to the notice,
be clarified as follows:
1. In the preamble, the FAA indicated that there had been
``several'' reports of corroded rotary actuator motors of the RAT found
on in-service airplanes. However, the commenter points out that there
have been only two reports of heavily corroded RAT motors in service
that have resulted in failures to deploy.
2. The preamble contained a statement indicating that
``investigation revealed'' that the RAT motor is not sealed. The
commenter points out that by design the RAT motor is not sealed.
3. The preamble described the area where the RAT actuator motor is
located as the ``right aft fairing;'' however, this area is
specifically the ``right aft wing-to-body fairing.''
4. The preamble stated that the motor is susceptible to moisture
accumulation when exposed to ``high'' cycling; however, a more accurate
description is ``altitude'' cycling.
The FAA agrees that these points should be clarified as suggested
by the commenter. However, because this background information is not
repeated in the final rule, no specific change is necessary.
Conclusion
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.
Interim Action
This rule is considered to be interim action. The manufacturer has
advised the FAA that it is pursuing development of a redesigned RAT
rotary actuator motor that is not susceptible to corrosion. Once that
item is developed, approved, and available, the FAA may consider
further rulemaking.
Cost Impact
There are approximately 583 Boeing Model 767 series airplanes of
the affected design in the worldwide fleet. The FAA estimates that 197
airplanes of U.S. registry will be affected by this AD, that it will
take approximately 1 work hour per airplane to accomplish the required
actions, and that the average labor rate is $60 per work hour. Based on
these figures, the cost impact of the AD on U.S. operators is estimated
to be $11,820, or $60 per airplane, per operational test.
The 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.
Regulatory Impact
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. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
96-20-05 Boeing: Amendment 39-9771. Docket 95-NM-203-AD.
Applicability: All Model 767 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
otherwise 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 (b) 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.
To ensure that the RAT actuator motor is not corroded to the
point where it may result in the failure of the RAT to deploy and
subsequently result in loss of emergency hydraulic power to the
flight controls in the event that power is lost in both engines,
accomplish the following:
(a) Within 6 months after the effective date of this AD; unless
previously accomplished within the last 6 months or 3,000 flight
hours prior to the effective date of this AD, whichever is later;
perform an operational test to verify proper deployment of the ram
air turbine (RAT) in accordance with Boeing Alert Service Bulletin
767-29A0080, dated October 12, 1995.
(1) If the RAT deploys correctly, repeat the operational test
thereafter at intervals not to exceed 6 months or 3,000 flight
hours, whichever occurs first.
(2) If the RAT does not fully deploy, prior to further flight,
replace the rotary actuator motor with a new or serviceable rotary
actuator motor, in accordance with the service bulletin. Thereafter,
repeat the operational test at intervals not to exceed 6 months or
3,000 flight hours, whichever occurs first.
(b) 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.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
[[Page 50999]]
(c) 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.
(d) The actions shall be done in accordance with Boeing Alert
Service Bulletin 767-29A0080, dated October 12, 1995. 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.
(e) This amendment becomes effective on November 4, 1996.
Issued in Renton, Washington, on September 19, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-24650 Filed 9-27-96; 8:45 am]
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