[Federal Register Volume 59, Number 53 (Friday, March 18, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-6340]
[[Page Unknown]]
[Federal Register: March 18, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 90-NM-265-AD]
Airworthiness Directives; Boeing Model 727 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Supplemental notice of proposed rulemaking; reopening of
comment period.
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SUMMARY: This document revises an earlier proposed airworthiness
directive (AD), applicable to Boeing Model 727 series airplanes, which
would have superseded an existing AD that currently requires periodic
leak checks of the forward lavatory drain system and provides for the
installation of a new drain valve as terminating action. The proposed
action would have deleted the existing provision for terminating
action, required repetitive leak checks of both the forward and aft
lavatory drain systems, and added an optional procedure for complying
with the rule. That proposal was prompted by reports of engine and
airframe damage, engine separation, and damage to property on the
ground, caused by ``blue ice'' that had formed from leaking forward
lavatory drain systems and subsequently had dislodged from the
airplane. This action revises the proposal by changing the optional
procedure, adding a requirement for installation of a cap on the flush/
fill line, and requiring periodic leak checks of the flush/fill system.
DATES: Comments must be received by May 2, 1994.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 90-NM-265-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.
FOR FURTHER INFORMATION CONTACT: Don Eiford, Aerospace Engineer,
Seattle Aircraft Certification Office, Systems and Equipment Branch,
ANM-130S, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056; telephone (206) 227-2788; fax (206) 227-
1811.
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 filed in 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 90-NM-265-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-103, Attention: Rules
Docket No. 90-NM-265-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
A proposal to amend part 39 of the Federal Aviation Regulations to
add an airworthiness directive (AD), applicable to Boeing Model 727
series airplanes, was published as a supplemental notice of proposed
rulemaking (NPRM) in the Federal Register on March 22, 1993 (58 FR
15305). That supplemental NPRM proposed to revise a previously issued
NPRM that proposed the supersedure of AD 86-05-07, Amendment 39-5250
(51 FR 7767, March 6, 1986). AD 86-05-07 currently requires periodic
leak checks of the forward lavatory drain system and provides for the
installation of a new drain valve as terminating action. The previously
issued supplemental NPRM proposed to:
1. Delete the existing provision for terminating action;
2. Require repetitive leak checks of both the forward and the aft
lavatory drain systems, and
3. Provide an optional procedure for complying with the rule, which
would entail revising the FAA-approved maintenance program to
incorporate a schedule and procedure to conduct leak checks of the
lavatory drain systems.
The proposed action was prompted by reports of engine and airframe
damage, and one report of engine separation on a Boeing Model 727
series airplane that occurred subsequent to the issuance of AD 86-05-
07. These incidents were caused by ``blue ice'' that had formed from
leaking forward lavatory drain systems and subsequently had broken
loose from the airplane and struck the fuselage or had been ingested
into the engine. The proposed action also was prompted by reports of
leakage from lavatory drain valves that have a configuration similar to
that specified in AD 86-05-07 as terminating action. Such leakage can
result in the formation of blue ice, which can dislodge from the
airplane and result in engine damage or separation, airframe damage,
and/or a hazard to persons or property on the ground.
Since the issuance of that supplemental NPRM, the FAA has
determined that certain additional changes to the proposed rule are
necessary.
General Changes to the Proposal: ``The Comprehensive Approach''
The FAA has reviewed its position on the option that was provided
in the previous supplemental NPRM, which would have permitted operators
to revise the FAA-approved maintenance program to include procedures to
address the problems associated with blue ice. The FAA now considers
that an even more comprehensive approach should be taken to address the
subject unsafe condition via the FAA-approved maintenance program. This
approach should be based upon regular maintenance, training of
personnel, use of hardware with proven reliability, and fixed, but less
frequent, leak checks incorporated into the FAA-approved maintenance
program. Paragraph (b) of this supplemental NPRM has been revised to
specify the requirements for the maintenance program revision that the
FAA has determined are necessary in order to implement this
``comprehensive approach.'' (A more detailed discussion of these
proposed requirements is presented later in this preamble.)
In lieu of the revising the maintenance program, however, this
supplemental NPRM will continue to provide operators with the option of
accomplishing the specific leak check procedures on the drain systems.
General Changes to the Notice: Extension of Leak Check Intervals
The proposed AD would extend the previously-proposed leak check
intervals for certain specific valves, provided that a suitable program
of maintenance and training of personnel is also implemented. These
intervals have been extended based upon data gathered to date regarding
the service history of the valve types.
The proposed AD would also require that any revisions to (i.e.,
extension of) the mandated leak check intervals must be approved by the
FAA, specifically, by the Manager of the Seattle Aircraft Certification
Office (ACO). Requests for such revisions must be accompanied by
certain data when submitted to the ACO [through the appropriate FAA
Principal Maintenance Inspector (PMI)] for approval. In this
supplemental NPRM, the FAA proposes a ``data collection format'' for
these requests. Data submitted in accordance with the proposed format,
if favorable to an increase of leak check intervals, will allow the FAA
to justify increasing the leak check intervals with assurance that the
valves involved have the required reliability. The data provided will
also be important in assisting the FAA in making future determinations
of appropriate leak check intervals for new valves that have shown
promising, but not conclusive, service data.
General Changes to the Notice: Flush/Fill Line Problems
Certain comments submitted to the Rules Docket in response to the
previously issued supplemental NPRM included reference to three
incidents of foreign object damage from the forward toilet drain valve
and flush/fill line on certain airplanes.
The FAA also has received a report of a dent on the right
horizontal stabilizer leading edge on a Boeing Model 737 series
airplane that was caused by blue ice that had formed from leakage
through a flush/fill line. In this case, the flush/fill cap was missing
from the line at the forward service panel. The flush/fill line on the
Model 737 is similar in design to that on the Model 727; therefore, the
potential exists for the same type of incident occurring on the Model
727.
Further, in their comments to the Rules Docket, numerous operators
stated that leakage from the flush/fill line is a significant source of
the type of blue ice problems addressed by this AD action.
While there are not many documented cases of blue ice coming from
the flush/fill line causing damage to engines, such blue ice is still a
hazard to persons and property on the ground and, therefore,
constitutes an unsafe condition. In light of this, the FAA has
reconsidered its previous statement that flush/fill line leakage would
be ``addressed by a separate rulemaking action,'' and is proposing
requirements in this supplemental NPRM to install a cap on the flush/
fill line and to perform periodic leak checks of the flush/fill line.
The FAA has reviewed and approved Boeing Service Bulletin 727-38-
0021, dated July 30, 1992, that provides instructions for modifying the
forward, aft, and executive lavatory drain systems by installing a cap
on the flush/fill lines. This modification will prevent blue fluid
leakage and subsequent ice accumulation in the executive and aft
lavatory service panels, and in the forward lavatory waste system.
This supplemental NPRM proposes to require the installation of the
flush/fill line cap in accordance with the Boeing service bulletin
within 5,000 flight hours.
General Changes to the Notice: New Owners' Schedules
A new paragraph (e) has been added to this supplemental NPRM to
require that, before an operator places an airplane subject to the AD
into service, the operator must establish a schedule for accomplishment
of the leak checks. This provision is intended to ensure that
transferred airplanes are inspected in accordance with the AD on the
same basis as if there were continuity in ownership, and that
scheduling of the leak checks for each airplane is not delayed or
postponed due to a transfer of ownership. Airplanes that have
previously been subject to the AD would have to be checked in
accordance with either the previous operator's or the new operator's
schedule, whichever would result in the earlier accomplishment date for
that leak check. Other airplanes would have to be inspected before an
operator could begin operating them or in accordance with a schedule
approved by the FAA PMI, but within a period not exceeding 200 flight
hours.
Since the changes described above expand the scope of the
previously proposed rule, the FAA has determined that it is necessary
to reopen the comment period to provide additional opportunity for
public comment.
Due consideration has been given to the following comments that
were submitted in response to the previously issued supplemental NPRM:
Hardware Nomenclature
Several commenters suggest that the proposal be revised to include
terms that would more specifically describe the valves that are
affected by the rule. Certain commenters suggest that generic
references to ``ball valves'' in proposed paragraph (a) should be
replaced with references to ``Boeing Specification S417T105,'' which
more clearly defines the configuration of the specific ball valve that
must be inspected. These commenters also suggest that references in
proposed paragraph (a) to the ``Shaw Aero Devices, Inc., drain valve
that incorporates an integral inner door with a second positive seal,''
be replaced with references to the ``service panel valve per Boeing
Specification 10-62213.'' On the other hand, one commenter requests
that the terms used in the proposal to describe the Shaw Aero valve be
retained, so that earlier models of the Shaw Aero valve (not configured
per Boeing Specification 10-62213) would ``benefit'' from the proposed
extended leak check intervals. Another commenter states that the
earlier models of those Shaw Aero valves were upgraded because they
leaked and, therefore, those valves should not be included with the
valves specified by ``Boeing Specification 10-62213'' for purposes of
receiving the extended leak check periods.
The FAA has reviewed the data submitted with these comments and
finds that certain of the requested changes are appropriate. The FAA
concurs with the request to specifically identify those valves approved
for the longer leak check intervals. The FAA has reviewed the
referenced Boeing specifications, as well as the part numbers of valves
that have been determined to meet these specifications and that have
service history data approved by the FAA. The FAA has determined that
the qualifying valves are as follows:
1. Valves meeting Boeing Specification S417T105: Kaiser
Electroprecision valves having part number 2651-329-5 (or higher ``dash
number'');
2. Valves meeting Boeing Specification 10-62213: Kaiser
Electroprecision valves having part number 0218-0032-8 (or higher
``dash number''); and Shaw Aero Devices valves having part number
10101000C-N (or higher ``dash numbers'').
Therefore, this supplemental NPRM has been revised to refer to
certain of the affected valves as those having the part numbers
indicated above. Valves having Kaiser Electroprecision part number
2651-329-5 (or higher ``dash number'') would be required to be leak
checked at intervals of either 1,500 flight hours [per proposed
paragraph (a)] or 5,000 flight hours [per proposed paragraph (b)].
Valves having Kaiser Electroprecision part number 0218-0032-8 (or
higher ``dash number'') or Shaw Aero Devices part number 10101000C-N
(or higher ``dash numbers'') would be required to be leak checked at
intervals of 1,000 flight hours. To ensure that any valves developed at
a later date are also reviewed first by the FAA for adequate service
history, new paragraph (f) of the proposed rule makes a provision for
the service history data of such additional valves to be approved by
means of an alternative method of compliance with the rule.
Ball Valves, General
Several commenters suggest that, because of the history of the
general reliability of ball valves, the proposed rule should be revised
to permit installation of a ball valve in a drain system as terminating
action for the leak checks of that particular drain system. Other
commenters request that, based on this history of reliability, the
proposed 1,500-flight hour leak checks intervals for drain systems
incorporating ball valves, as proposed in paragraph (a)(1), be extended
to 4,000 or 6,000 flight hours.
The FAA does not concur. While a ball valve may be reliable if
properly maintained, it may still leak eventually due to seal wear or
the entrapment of foreign material on the sealing surfaces. Damage to
the sealing surfaces in a ball valve due to foreign materials, while
uncommon, may also cause leakage at any time. If there are no
maintenance actions aimed at detecting such leakage, the leakage could
continue until the next leak check. An extremely long interval between
leak checks, as suggested by the commenters, would allow leakage to go
undetected for a long time and, thus, create conditions favorable for
the eventual formation of blue ice. The FAA has determined that, by
limiting the leak check interval to 1,500 flight hours, the risk of
long term leakage is reduced.
Ball Valve Leak Checks, Plus Maintenance and Training Programs
Several commenters request that the proposed leak check intervals
for drain systems incorporating a ball valve be extended to 4,000 or
6,000 flight hours, if those leak checks are coupled with a specific
maintenance program as well as a program to train personnel to perform
certain actions. Some of these commenters consider that incorporation
of the 1,500-flight hour leak checks into the operators' FAA-approved
maintenance program, as proposed in paragraph (b) of the previous NPRM,
does not provide sufficient motivation for operators to incorporate
ball valves into the fleet (even though the ball valves are more
reliable than other types).
The FAA concurs with these commenters' request. The FAA has
determined that installation of a design package that includes a ball
valve installed in accordance with Boeing Service Bulletin 727-38-0021,
dated July 30, 1992, combined with certain maintenance actions and
trained personnel (discussed in detail later) will provide adequate
assurance that long term leakage will not occur. Therefore, the FAA has
revised paragraph (b) of the supplemental NPRM to provide for leak
check intervals up to 5,000 flight hours for applicable ball valve
installations that are coupled with maintenance procedures and training
of personnel. This change is specifically intended to encourage
operators to use valve designs having proven reliability; the
incorporation of sufficient maintenance practices and trained personnel
will ensure that the inherent reliability of the design is not
degraded.
Shaw Aero Valves
One commenter requests that the leak check intervals for drain
systems with Shaw Aero valves that incorporate the inner door with
second positive seal be increased from 1,000 flight hours, as proposed
in paragraph (a)(2), to 1,500 or 4,000 flight hours. This commenter
considers that this request is justified based on the lack of adverse
service history on the subject valves.
On the other hand, another commenter objects to the proposed 1,000-
flight hour leak check interval for these valves, and suggests that it
should be shortened. This commenter states that there are certain
considerations that are critical in establishing leak check intervals
based on component failure rates derived from evaluations of in-service
history. Such considerations are:
1. If the ball valve is installed internally so that service
personnel cannot damage it;
2. If the seals are composed of the correct material, and are not
directly in the effluent path so that they cannot be damaged by items
within the effluent that can normally cause seal damage;
3. If, because of the location of the ball valve, it is impractical
to perform a seal replacement;
4. If the valve is leak checked on board the airplane without a
seal change prior to the check;
This commenter states that, when these items are taken into
consideration, service data gathered on this ball valve are
``unambiguous,'' because if the valve passes a leak check, it means
that the valve did not leak before the check was conducted. However,
the subject Shaw Aero valve is located in the service panel and is
accessible to maintenance personnel; moreover, it is common practice
for those personnel to change the seals in the panel valve prior to
leak check intervals. Therefore, the leak check service data that have
been presented relative to this Shaw Aero valve are ``questionable,''
due to the lack of reporting and the fact that seals can be changed out
during servicing and prior to the leak checks.
The FAA does not concur with either commenter's request. The FAA
has reviewed the design improvements and service history data of the
Shaw Aero valves having part number 10101000C-N (or higher dash number)
and has determined that a leak check interval of 1,000 flight hours is
justifiable, based upon the best available data to date. The FAA does
agree with the latter commenter to the extent that justification for
any further extension of this leak check interval beyond 1,000 flight
hours must be based on unambiguous data.
Kaiser Expander Valves
Several commenters submitted service history data on the Kaiser
Expander valve, part number 0218-0032-8, and request that the proposed
rule provide for a leak check interval of 4,000 or 4,500 flight hours
for this valve. As currently written, the proposed rule would place the
Kaiser Expander valve in the category of valves requiring leak checks
every 200 flight hours. These commenters state that the Kaiser Expander
valve has the same positive bore sealing inner flap as the Shaw Aero
valve, and has a service history to prove it is as safe, rugged, and
reliable as the Shaw Aero valve. Some of these commenters consider this
Kaiser valve to be the ``best that is currently available,'' and note
that it had been approved previously as terminating action for AD 86-
05-07.
The FAA concurs that the leak check interval for the Kaiser
Expander valve, part number 0218-0032-8 (or higher dash number), may be
increased from the proposed 200 flight hours. The FAA has reviewed the
service history data for the Kaiser Expander valve and finds that it is
sufficient to justify a 1,000-flight hour leak check interval proposed
in paragraphs (a)(2) and (b)(2)(ii) of this supplemental NPRM.
Other Brands of Valves
Other commenters suggest that the proposal be revised to increase
the leak test intervals to 400 flight hours for the ``other valves''
referred to in proposed paragraph (a)(3) of the previous supplemental
NPRM; and to allow that interval to be increased up to 5,000 flight
hours (an average ``C'' check). These commenters consider that a 200-
flight hour interval is too frequent and would create an undue economic
burden on affected operators.
For many of the same reasons previously discussed, the FAA does not
concur. The FAA does not consider that valves without demonstrated high
reliability should be used without frequent leak checking. Frequent
leak checking provides assurance that the valves will be returned to a
non-leaking condition. The FAA has recognized that some valves in the
``other'' category (such as the earlier Shaw Aero valve models) do have
better service history than others regarding failure and leakage;
therefore, as described previously, the FAA has singled out these
valves and has extended their leak check interval. However, for valves
that are known to be more likely to leak, specifically the ``donut''
and ``taco'' valves, a 200-flight hour leak check interval is
essential.
Certain commenters request that the proposed rule be revised to
grant other brand name valves extended leak check intervals. However,
these commenters did not furnish sufficient service history or leak
check data to substantiate their requests. The FAA cannot determine if
extensions of leak check intervals are warranted without being able to
review significant service history data.
Operators With No Record of Leakage
One commenter suggests that the proposed rule include a provision
for an extended leak check interval for operators that have had no
record of waste water leakage, regardless of what hardware
configuration is used. The commenter considers that the proposal
penalizes operators who have had an excellent service history due to
proper maintenance and servicing. While the installation of additional
hardware will improve the waste system and reduce the likelihood of
leaking, it should be used as an incentive for those operators that
have had a history of leaking waste systems and blue ice foreign object
damage.
The FAA does not agree that an extended interval is warranted for
the reasons suggested by the commenter. Blue ice frequently is not
traceable to the particular airplane, operator, and waste system that
produced it. Incidents of leakage usually are not reported; only the
relatively serious leakage incidents become known to the FAA. Previous
attempts to rely solely upon increased maintenance while using lower
reliability hardware have not proven to be successful. Therefore, a
system to prevent incidents of blue ice in the fleet must be based upon
assurance. The FAA considers that such assurance is provided by
frequent leak checks to ensure that the drain systems do not leak; more
reliable valves may be subject to less frequent leak checks, while less
reliable valves must be subject to more frequent leak checks. As
discussed previously, the FAA considers that maintenance and training
are also important factors in determining appropriate leak check
intervals, and has provided in this supplemental NPRM an option for
either increased leak test intervals, or obtaining approval for less
frequent intervals when hardware is demonstrated to be reliable.
Requests for No Leak Tests for Some Valves
One commenter requests that, in cases where a ball valve is
installed with a service panel valve that has no inner flapper, the
proposed rule not require a leak check to be done on the service panel
valve. The commenter also requests that the proposed rule be revised to
require that, when a service panel valve with an inner door having a
second positive seal is installed with a ball valve, only the inner
seal be tested, and the outer cap seal be visually inspected and
replaced as necessary. The commenter notes that the proposed rule would
call for a pressure differential to be applied across both the ball
valve and the service panel cap valve. However, on many ball valve
installations, the service panel cap has no inner flapper. Applying a
pressure differential across this cap would require spilling a
substantial quantity of fluid on the ramp in order to service the
system after completion of the leak check. The commenter recommends
that the service panel cap valve only be leak checked if it
incorporates a dual seal design, and that the outer cap be visually
inspected for wear or damage, and replaced only as necessary or at
predetermined intervals.
The FAA does not agree with the commenter's request to delete the
leak check requirement for service panel valves that have no inner
flapper. This would be disadvantageous to operators who had a superior
hardware configuration (the dual seal), since it would require that
they perform a test that is not required of installations with only a
single cap. However, the FAA does agree with the suggestion to require
a leak check of only the inner flapper for service panel valves with a
dual seal design, and the performance of visual inspections/seal
changes of only the outer cap. This will ensure that one seal
downstream of the ball valve is returned to a ``no-leak'' condition.
This supplemental NPRM has been revised accordingly.
Development of New Equipment
Several commenters request that the proposed rule provide for a
method to encourage the development of new, more reliable equipment,
and extend the leak check intervals for that equipment.
The FAA agrees that the industry should be encouraged to develop
improved hardware that will better address the unsafe condition
presented by problems associated with blue ice. As one method to
achieve this goal, and to provide assurance of a high degree of
reliability of the hardware involved, the FAA has proposed in paragraph
(c) of this supplemental NPRM, a method of data collection relative to
the reliability of valves. This approach is not intended to supersede
existing methods for equipment qualification and certification.
However, this method of data collection is intended to ensure the
collection of unambiguous data, which will provide the FAA with
adequate resources and information to determine appropriate leak check
intervals for new and existing designs. The FAA intends to use the data
that are eventually collected to determine if extensions to the
currently proposed leak check intervals are justified, specifically for
those operators who choose to incorporate certain maintenance and
training requirements into their FAA maintenance programs in accordance
with paragraph (b) of this supplemental NPRM. The FAA specifically
requests additional suggestions as to methods that will further ensure
the validity of the data gathered.
Implementation of a New Maintenance and Training Program
Numerous commenters request that the proposed rule be revised to
provide for an alternative to the fixed leak check intervals by
permitting the implementation of a program in which operators could
incorporate a schedule of maintenance actions, training, and periodic
leak checks into their FAA-approved maintenance program. These
commenters state that merely performing more leak checks at greater
frequencies will not, by itself, address the blue ice problem. Instead,
other maintenance tasks, such as replacing seals at regular intervals
and establishing effective communication procedures between maintenance
personnel and the flight crew, play more significant roles in
addressing blue ice safety concerns. The commenters request that
compliance periods for leak checks be adjusted in accordance with
existing FAA-approved reliability programs, or be increased to ``C''
check intervals, provided that certain maintenance and training
programs were initially included in the maintenance program.
The FAA concurs that these commenters' suggestions have merit. The
FAA has determined that an increase in the leak check intervals could
be justified if the equipment is demonstrated to be highly reliable,
and a program of regular maintenance and training is implemented. The
FAA has revised proposed paragraph (b) of the supplemental AD to
include specific procedures considered to be essential in such a
program. These procedures include: (1) Repetitive replacement of seals,
(2) leak checks at various intervals depending upon the valve
configuration, (3) leak checks of flush/fill line caps, (4) visual
checks conducted by maintenance personnel at regular intervals to
detect leakage, (5) procedures for reporting discrepancies, and (6)
training programs for maintenance and service personnel that include
information on ``Blue Ice Awareness'' and the hazards of blue ice. The
proposal specifically would extend the leak check interval for certain
valves to 5,000 flight hours (which is equivalent to a ``C'' check for
the majority of affected operators), provided the specified program of
maintenance and training is implemented.
Recordkeeping
Some commenters request that proposed paragraph (b) of the NPRM be
revised to specify that, once operators have acceptably revised their
maintenance program to include the specified actions, the AD is no
longer ``applicable'' to those operators. In effect, the maintenance
program revision should be considered ``terminating action'' for the
AD. These commenters would prefer to accomplish all of their AD-
required leak check tasks within the parameters of their FAA-approved
maintenance program, since ``operators have more flexibility in
adjusting leak check intervals in accordance with their FAA-approved
reliability programs and recordkeeping requirements are less
cumbersome.'' The commenters point out that paragraph (b) of the
previous NPRM denies operators the opportunity to integrate their leak
check tasks into their maintenance program, since ``the NPRM fails to
indicate that AD recording procedures are not in effect, and disallows
the opportunity to ever adjust the leak check intervals without seeking
approval under the alternative method of compliance provision.'' The
commenters request that, for these operators, the proposed rule provide
for the use of an alternative method of recordkeeping to that otherwise
required by Federal Aviation Regulations (FAR) 91.417 (``Maintenance
records'') and 121.380 (``Maintenance recording requirements'').
The FAA does not concur with the commenters' request to revise the
proposal to indicate in any way that it is ``no longer applicable''
once the revision to the FAA-approved maintenance program is
implemented and the appropriate logbook entry made. The FAA considers
that, even though this proposed AD would affect the maintenance
program, it is of such importance that it warrants other than
``normal'' procedures to be followed in certain aspects. Specifically,
under ``normal'' maintenance program procedures, the PMI is authorized
to approve any revisions of the maintenance program, including
adjustments of the leak check intervals. However, for reasons detailed
below, the FAA has determined that the PMI is not the appropriate FAA
official for adjusting the compliance intervals for leak checks
specified by the terms of this AD.
Likewise, the FAA does not concur with the commenters' request to
revise the proposal to provide specifically for the use of an
alternative method of recordkeeping. Although the FAA has included such
a provision in other rulemaking actions [reference, for example, AD 92-
22-08 R1, amendment 39-8591 (58 FR 32281, June 9, 1993); and AD 92-22-
09 R1, amendment 39-8590 (58 FR 32278, June 9,1993); both of which
require the implementation of a corrosion prevention and control
program on certain transport category airplanes], the FAA has been
unable to confirm that there has been any case in which an operator has
found it necessary to use such alternative recordkeeping methods.
Therefore, the FAA concludes that the recordkeeping methods currently
required by FAR 91.417 and 121.380 are sufficient, and there is no need
to include a specific provision in this proposed rule for alternatives.
Principal Maintenance Inspector (PMI) Involvement
Some commenters recommend that the FAA recognize the merit in
delegating complete program oversight responsibility to the cognizant
PMI, once an operator has an approved program in accordance with the
alternative provision of proposed paragraph (b). These commenters point
out that justification for issuing the proposed AD is based on the
premise that certain operators may not have a sufficiently
comprehensive maintenance program currently in place to address the
blue ice safety concern. However, once a proper maintenance program for
handling the blue ice safety concerns has been approved by the FAA and
adopted, there is no longer a safety concern to warrant oversight by
the Seattle ACO. The administration of handling this program should be
subject to oversight by the PMI and, as is normal for the regular
maintenance program as a whole, the PMI should be the FAA official with
the authority to approve any future adjustments to the leak check
intervals.
Although the FAA agrees that the PMI may be permitted certain
oversight of the proposed alternative maintenance program provision of
the rule (discussed above with regard to recordkeeping), the FAA does
not agree that the PMI should be tasked with approving adjustments to
the leak check intervals. In order for the PMI to have some basis for
changing the intervals, he/she would need to know (1) when to expect
the valve to start leaking, and (2) how to ensure that the leak check
interval does not allow the valve to reach that point. These two
important items are related to the concept of ``failure threshold
criteria.'' The FAA has reviewed available service history data (as
well as comments submitted to this and previous NPRM's) to evaluate
which valves, if any, appear to have ``failure threshold criteria,''
and what those criteria are. While certain failure modes for valves
have been identified, the failure threshold criteria are difficult to
define in many cases. For example:
1. ``Normal'' seal wear will eventually cause a valve to leak. Such
seal wear should be a relatively predictable cause of failure for any
given operator.
2. Developmental problems related to valve or installation design
problems (i.e., use of incorrect seal materials) may cause leakage
after the initial installation, but after the design ``fix'' is made
and installed, leakage from this type of problem should stop.
3. Entrapment of waste materials on valve sealing surfaces can
cause leakage; but this does not appear to be related to the valve's
time-in-service, in that such entrapment is as likely to occur on the
first cycle as on a later cycle. Entrapment of waste matter on the
sealing surfaces has been known to cause an increase in operating
torque of the valve handle; this would be a failure threshold criterion
for ball valves [which the FAA has incorporated as part of the
maintenance requirements for the in-line drain valves, as specified in
proposed paragraph (b) of this supplemental NPRM]. For certain other
types of valves, however, entrapment of foreign matter does not yield
such an indicator.
4. The valve may be damaged during service on any particular cycle,
assuming it is in a position where it is accessible during normal
servicing. Such damage during servicing, or even incorrect servicing
(i.e., failure to install the plug in a donut valve), may be failure
modes especially for service panel-mounted valves, which are
accessible. However, they are not failure modes for in-line drain
valves because these valves are not accessible during normal servicing.
As one can readily recognize, different valves may or may not be
susceptible to these modes of failure, depending upon the valve design,
installation location, maturity of design (all fixes incorporated), and
other factors. The data available to the FAA simply do not indicate
which failure modes are most likely to cause leakage for any particular
valve.
Based on the most recent analysis and data available, however, the
FAA has determined that only the in-line drain ball valve, as installed
in accordance with Boeing Service Bulletin 727-38-0021, dated July 30,
1992, may have specific failure threshold criteria. A PMI could use
these criteria as a basis for adjusting leak check intervals with some
degree of confidence that the valve would not be allowed to reach the
point when it would be expected to start leaking. Given the high
reliability of these valves (which have a very low total number of
leaks from any cause), and the element of relative predictability of
failure modes (change seals regularly to avoid seal wear problems, fix
the valve if high operating torque is evident, etc.), the FAA has
determined that it is appropriate to allow these valves to be leak
checked at intervals of 5,000 flight hours (equivalent to a ``C''
check). The FAA considers it impractical, however, to allow the PMI to
extend the leak check interval only for these in-line drain ball valve
installations. In any case, a leak test at ``C'' check intervals
provides assurance that operators are following correct maintenance
procedures.
The current data do not convince the FAA that service panel-mounted
valves have been demonstrated (unambiguously) to be as reliable as the
ball valve. The ratio of failures from ``unpredictable'' failure modes
to failures from ``predictable'' failure modes is not known for these
valves. In light of this, a PMI would have no data on which to base an
extension of a leak check interval for panel-mounted valves with the
assurance that the valve would not fail within the adjusted interval.
Further, PMI's who work with smaller operators would not see
sufficient data to give them the assurance that an expanded leak check
interval for any valve is justified.
Since failure threshold criteria and definitive leak/failure rate
data do not exist for the majority of the subject valves, it is
essential that the FAA, at the ACO level, have feedback as to the leak
and failure rates experienced in the field. Although the PMI's serve as
the FAA's critical link with the operators (and their oversight
responsibilities will not be minimized by this AD action), it is the
staff of the ACO that provides the engineering support necessary to
evaluate whether increases in repeat leak check intervals will maintain
an acceptable level of safety. Additionally, given that possible new
relevant issues might be revealed during the approval process, it is
imperative that the engineering staff at the ACO have such feedback.
Relationship of Leak Checks to Certification Maintenance Requirements
(CMR)
Several commenters state that, because this proposal is considered
to be a model for future AD actions applicable to other airplanes
(presumably including newly-delivered aircraft that will be configured
with similar in-line drain valves), the adoption of proposed paragraph
(a) will require repetitive leak checks on all newly delivered
aircraft. The commenters view this as ``tantamount to issuing a
certification maintenance requirement (CMR)'' via the AD process.
The FAA does not concur. CMR items are intended to be repetitive
inspections or component replacements for equipment, systems, and
installations. Accomplishment of CMR items would ensure that the
statistical probability of certain failures that could occur during
operation of the airplane does not exceed the limitations specified in
Sec. 25.1309 (``Equipment, systems, and installations'') of the FAR,
which is applicable to the design and approval of transport category
airplanes. Further, CMR items are based on statistical safety analyses
of airplane electrical, electronic, hydraulic, pressurization, and
propulsion systems. These analyses must be completed by the
manufacturer and approved by the FAA prior to the issuance of an
airplane Type Certificate (TC). Following issuance of the TC, those
inspections, component replacements, or overhaul interval requirements
for airplane systems that are based on in-service experience with the
airplane, but that do not result in re-evaluation of the basic
statistical analysis on which approval of the system is based, do not
qualify as CMR items.
The leak check schedule proposed in this notice is not related to
compliance of the airplane design with the statistical evaluation
requirements of FAR Sec. 25.1309 for equipment, systems, and
installations. For this reason, the proposed leak checks do not qualify
as a CMR item. The intent of the proposed leak checks is to address the
unsafe condition presented by the problems associated with blue ice;
the appropriate vehicle for mandating actions to address an unsafe
condition is the airworthiness directive.
Compliance Time for Proposed Maintenance Program Change
Several commenters request that the proposed 30-day compliance time
for revising the operators' FAA-approved maintenance programs be
extended to 180 days. The commenters consider that the proposed time is
too short, since implementing such a revision will require addition
work hours, personnel, and material.
The FAA concurs. In view of the increased scope of the proposed
changes to the maintenance program, the FAA has revised paragraph (b)
to require compliance within 180 days. This will allow operators
adequate time to implement the required revisions to the maintenance
program, both logistically and administratively. It will also provide
time for the development of the necessary training programs and the
training of personnel in the new procedures.
Cost Impact
There are approximately 1,752 Boeing Model 727 series airplanes of
the affected design in the worldwide fleet, operated by 153 operators.
It is estimated that 1,277 airplanes of U.S. registry and 54 U.S.
operators would be affected by this AD. The FAA estimates that it would
take approximately 4 work hours per airplane lavatory drain (2 drains
per airplane) to accomplish a leak check, and the average labor cost
would be $55 per work hour.
For the 1,077 airplanes that have donut/cap type or other approved
drain valves (excluding Shaw Aero drain valves) installed in both drain
systems, approximately 15 leak checks per airplane would be required
each year. For the 36 airplanes that have Shaw Aero drain valves
installed in both drain systems, approximately 3 leak checks per
airplane would be required each year. For the 164 airplanes that have a
ball valve installed in the forward lavatory drain and a Shaw Aero
drain valve installed in the aft lavatory drain, approximately 2 leak
checks of the forward drain and 3 leak checks of the aft drain would be
required per year. Based on these figures, the total annual (recurring)
cost impact of the repetitive leak checks on U.S. operators is
estimated to be $7,336,120.
The 1,277 airplanes of U.S. registry have, on an average, 3 flush/
fill lines per airplane. The FAA estimates that the installation cost
of a level lock cap assembly would require approximately 2 work hours
to accomplish, at an average labor cost of $55 per work hour. Required
parts are estimated to be $275 per drain installation. Based on these
figures, the total cost impact of the requirement to install a cap on
the flush/fill lines is estimated to be $1,474,935, or an average of
$1,155 per airplane.
The number of required work hours, as indicated above, is presented
as if the accomplishment of the actions proposed in this AD were to be
conducted as ``stand alone'' actions. However, in actual practice,
these actions would be accomplished coincidentally or in combination
with normally scheduled airplane inspections and other maintenance
program tasks. Therefore, the actual number of necessary ``additional''
work hours would be minimal in many instances. Additionally, any costs
associated with special airplane scheduling would be minimal.
In addition to the costs discussed above, for those operators who
elect to comply with proposed paragraph (b) of this AD action, the FAA
estimates that it would take approximately 40 work hours per operator
to incorporate the lavatory drain system leak check procedures into the
maintenance programs, at an average labor cost of $55 per work hour.
Based on these figures, the total cost impact of the proposed
maintenance revision requirement of this AD action on the 54 U.S.
operators is estimated to be $118,800, or $2,200 per operator.
The ``total cost impact'' figures described above are based on
assumptions that no operator has yet accomplished any of the proposed
requirements of this AD action, and no operator would accomplish those
actions in the future if this AD were not adopted.
The FAA recognizes that the obligation to maintain aircraft in an
airworthy condition is vital, but sometimes expensive. Because AD's
require specific actions to address specific unsafe conditions, they
appear to impose costs that would not otherwise be borne by operators.
However, because of the general obligation of operators to maintain
aircraft in an airworthy condition, this appearance is deceptive.
Attributing those costs solely to the issuance of this AD is
unrealistic because, in the interest of maintaining safe aircraft, most
prudent operators would accomplish the required actions even if they
were not required to do so by the AD.
A full cost-benefit analysis has not been accomplished for this
proposed AD. As a matter of law, in order to be airworthy, an aircraft
must conform to its type design and be in a condition for safe
operation. The type design is approved only after the FAA makes a
determination that it complies with all applicable airworthiness
requirements. In adopting and maintaining those requirements, the FAA
has already made the determination that they establish a level of
safety that is cost-beneficial. When the FAA, as in this proposed AD,
makes a finding of an unsafe condition, this means that this cost-
beneficial level of safety is no longer being achieved and that the
proposed actions are necessary to restore that level of safety. Because
this level of safety has already been determined to be cost-beneficial,
a full cost-benefit analysis for this proposed AD would be redundant
and unnecessary.
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'' 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 14
CFR part 39 of the Federal Aviation Regulations 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 removing amendment 39-5250 (51 FR
7767, March 6, 1986), and by adding a new airworthiness directive (AD),
to read as follows:
Boeing: Docket No. 90-NM-265-AD. Supersedes AD 86-05-07,
Amendment 39-5250.
Applicability: All Model 727 series airplanes, certificated in
any category.
Compliance: Required as indicated, unless previously
accomplished.
To prevent engine damage or separation, airframe damage, and/or
hazard to persons or property on the ground as a result of ``blue
ice'' that has formed from leakage of the lavatory drain system and
dislodged from the airplane, accomplish the following:
(a) Except as provided in paragraph (b) of this AD, accomplish
the applicable procedures specified in paragraphs (a)(1), (a)(2),
(a)(3), (a)(4), and (a)(5) of this AD:
(1) For each lavatory drain system, forward or aft, that has an
in-line drain valve installed, Kaiser Electroprecision part number
2651-329-5 (or higher dash number): Within 1,500 flight hours after
the effective date of this AD, and thereafter at intervals not to
exceed 1,500 flight hours, accomplish the following:
(i) Conduct a leak check of the dump valve (in-tank valve that
is spring loaded closed and operable by a T-handle at the service
panel), ball valve, and cap valve. The ball valve and cap valve leak
checks must be performed with a minimum of 3 pounds per square inch
differential pressure (PSID) applied across each valve. If the cap
valve has an inner door with a second positive seal, only the inner
door must be tested.
(ii) Visually inspect the seal on the outer door for wear or
damage that may cause leakage. Any worn or damaged seal must be
replaced, prior to further flight, in accordance with the valve
manufacturer's maintenance manual.
(2) For each lavatory drain system, forward or aft, that has a
service panel drain valve installed, Kaiser Electroprecision part
number 0218-0032-8 (or higher dash number) or Shaw Aero Devices part
number 10101000C-N (or higher dash number): Within 1,000 flight
hours after the effective date of this AD, and thereafter at
intervals not to exceed 1,000 flight hours, conduct a leak check of
the dump valve and drain valve. The drain valve leak check must be
performed with a minimum of 3 PSID applied across the valve.
(3) For other forward or aft lavatory drain systems not
addressed in paragraph (a)(1) or (a)(2) of this AD: Within 200
flight hours after the effective date of this AD, and thereafter at
intervals not to exceed 200 flight hours, conduct a leak check of
the dump valve and the drain valve at the service panel. The drain
valve leak check must be performed with a minimum 3 PSID applied
across the valve.
(4) For flush/fill lines: Within 5,000 flight hours after the
effective date of this AD, and thereafter at intervals not to exceed
5,000 flight hours, conduct a leak check of the cap on the flush/
fill line. This leak check must be made with a minimum of 3 PSID
applied across the cap.
(5) If a leak is discovered during any leak check required by
paragraph (a) of this AD, prior to further flight, accomplish one of
the following procedures:
(i) Repair the leak; or
(ii) Drain the affected lavatory system and placard the lavatory
inoperative until repairs can be accomplished.
(b) As an alternative to the requirements of paragraph (a) of
this AD: Within 180 days after the effective date of this AD, revise
the FAA-approved maintenance program to include the requirements
specified in paragraphs (b)(1), (b)(2), (b)(3), (b)(4), (b)(5),
(b)(6), and (b)(7) of this AD.
(1) Replace the valve seals in accordance with the applicable
schedule specified in paragraphs (b)(1)(i) and (b)(1)(ii) of this
AD. Any revision to this replacement schedule must be approved by
the Manager, Seattle Aircraft Certification Office (ACO), FAA,
Transport Airplane Directorate.
(i) For each lavatory drain system, forward or aft, that has an
in-line drain valve installed, Kaiser Electroprecision part number
2651-329-5 (or higher dash number): Replace the seals within 5,000
flight hours after revision of the maintenance program in accordance
with paragraph (b) of this AD, and thereafter at intervals not to
exceed 52 months.
(ii) For each lavatory drain system, forward or aft, that has
any other type of drain valve: Replace the seals within 5,000 flight
hours after revision of the maintenance program in accordance with
paragraph (b) of this AD, and thereafter at intervals not to exceed
18 months.
(2) Conduct periodic leak checks of the lavatory drain systems
in accordance with the applicable schedule specified in paragraphs
(b)(2)(i), (b)(2)(ii), (b)(2)(iii), and (b)(2)(iv) of this AD. Any
revision to the leak check schedule must be approved by the Manager,
Seattle ACO, FAA, Transport Airplane Directorate.
(i) For forward lavatory drain systems modified in accordance
with Boeing Service Bulletin 727-38-0021, dated July 30, 1992
[installing an in-line drain valve, Kaiser Electroprecision part
number 2651-329-5 (or higher dash number)]: Within 5,000 flight
hours after revision of the maintenance program in accordance with
paragraph (b) of this AD, and thereafter at intervals not to exceed
5,000 flight hours, conduct leak checks. The ball valve and cap
valve leak checks must be performed with a minimum of 3 pounds per
square inch differential pressure (PSID) applied across each valve.
If the cap valve has an inner door with a second positive seal, only
the inner door must be tested. Additionally, visually inspect the
seal on the outer door for wear or damage that may cause leakage;
any worn or damaged seal must be replaced, prior to further flight,
in accordance with the valve manufacturer's maintenance manual.
(ii) For each lavatory drain system, forward or aft, that has a
service panel drain valve installed, Kaiser Electroprecision part
number 0218-0032-8 (or higher dash number) or Shaw Aero Devices part
number 10101000C-N (or higher dash number): Within 1,000 flight
hours after revising the maintenance program in accordance with
paragraph (b) of this AD, and thereafter at intervals not to exceed
1,000 flight hours, conduct leak checks of the dump valve and drain
valve . The drain valve leak check must be performed with a minimum
of 3 PSID applied across the valve.
(iii) For each lavatory drain system, forward or aft, that
incorporates either ``donut'' valves, Kaiser Electroprecision part
number 4259-20 or 4259-31; or that incorporates ``taco'' valves,
Kaiser Electroprecision part number 2651-311-1, -2, -3, -4, -5, -6,
or -7: Within 200 flight hours after revising the maintenance
program in accordance with paragraph (b) of this AD, and thereafter
at intervals not to exceed 200 flight hours, conduct leak checks of
the dump valve and the drain valve. The drain valve leak check must
be performed with a minimum 3 PSID applied across the valve.
(iv) For each lavatory drain system, forward or aft, that
incorporates any other type of approved valves: Within 400 flight
hours after revising the maintenance program in accordance with
paragraph (b) of this AD, and thereafter at intervals not to exceed
400 flight hours, conduct leak checks of the dump valve and the
drain valve. The drain valve leak check must be performed with a
minimum 3 PSID applied across the valve.
(3) For flush/fill lines: Within 5,000 flight hours after
revising the maintenance program in accordance with paragraph (b) of
this AD, and thereafter at intervals not to exceed 5,000 flight
hours, conduct a leak check of the cap on the flush/fill line. This
leak check must be made with a minimum of 3 PSID applied across the
cap.
(4) Provide procedures for accomplishing visual inspections to
detect leakage, to be conducted by maintenance personnel at
intervals not to exceed 4 calendar days or 45 flight hours, which
ever occurs later.
(5) Provide procedures for reporting leakage. These procedures
shall provide that any ``blue streak'' findings must be reported to
maintenance and that, prior to further flight, the leaking system
shall either be repaired, or be drained and placarded inoperative.
(i) For systems incorporating an in-line drain valve, Kaiser
Electroprecision part number 2651-329-5 (or higher dash number): The
reporting procedures must include provisions for reporting to
maintenance any instances of abnormal operating torque of the valve
handle for the in-line drain valve, as observed by service personnel
during normal servicing.
(A) Additionally, these provisions must include procedures for
either: prior to further flight, following the in-line drain valve
manufacturer's recommended troubleshooting procedures and correction
of the discrepancy; or prior to further flight, draining the
lavatory system and placarding it inoperative until the correction
of the discrepancy can be accomplished.
(B) If the drain system also includes an additional service
panel drain valve, Kaiser Electroprecision part number 0218-0032-8
(or higher dash number) or Shaw Aero Devices part number 10101000C-N
(or higher dash number), indications of abnormal operating torque of
the valve handle for the in-line drain valve need not be addressed
immediately if a leak check of the additional valve indicates no
leakage or other discrepancy. In these cases, repair of the in-line
drain valve must be accomplished within 1,000 flight hours after the
leak check of the additional service panel drain valve.
(6) Provide training programs for maintenance and servicing
personnel that include information on ``Blue Ice Awareness'' and the
hazards of blue ice.
(c) For operators who elect to comply with paragraph (b) of this
AD: Any revision to (i.e., extension of) the leak check intervals
required by paragraph (b) of this AD must be approved by the
Manager, Seattle ACO, FAA, Transport Airplane Directorate. Requests
for such revisions must be submitted to the Manager of the Seattle
ACO through the FAA Principal Maintenance Inspector (PMI), and must
include the following information:
(1) The operator's name;
(2) A statement verifying that all known cases/indicates of
leakage or failed leak tests are included in the submitted material;
(3) The type of valve (make, model, manufacturer, vendor part
number, and serial number);
(4) The period of time covered by the data;
(5) The current FAA leak check interval;
(6) Whether or not seals have been replaced between the seal
replacement intervals required by this AD;
(7) Whether or not leakage has been detected between leak check
intervals required by this AD, and the reason for leakage (i.e.,
worn seals, foreign materials on sealing surface, scratched or
damaged sealing surface or valve, etc.);
(8) Whether or not any leak check was conducted without first
inspecting or cleaning the sealing surfaces, changing the seals, or
repairing the valve. [If such activities have been accomplished
prior to conducting the periodic leak check, that leak check shall
be recorded as a ``failure'' for purposes of the data required for
this request submission. The exception to this is the normally
scheduled seal change in accordance with paragraph (b)(1) of this
AD. Performing this scheduled seal change prior to a leak check will
not cause that leak check to be recorded as a failure.]
Note 1: Requests for approval of revised leak check intervals
may be submitted in any format, provided the data give the same
level of assurance specified in this paragraph.
Note 2: For the purposes of expediting resolution of requests
for revisions to the leak check intervals, the FAA suggests that the
requestor summarize the raw data; group the data gathered from
different airplanes (of the same model) and drain systems with the
same kind of valve; and provide a recommendation from pertinent
industry group(s) and/or the manufacturer specifying an appropriate
revised leak check interval.
(d) For all airplanes: Within 5,000 flight hours after the
effective date of this AD, install a cap on the flush/fill lines for
forward, aft, and executive lavatories in accordance with Boeing
Service Bulletin 727-38-0021, dated July 30, 1992.
(e) For any affected airplane acquired after the effective date
of this AD: Before any operator places into service any airplane
subject to the requirements of this AD, a schedule for the
accomplishment of the leak checks required by this AD shall be
established in accordance with either paragraph (e)(1) or (e)(2) of
this AD, as applicable. After each leak check has been performed
once, each subsequent leak check must be performed in accordance
with the new operator's schedule, in accordance with either
paragraph (a) or (b) of this AD as applicable.
(1) For airplanes previously maintained in accordance with this
AD, the first leak check to be performed by the new operator must be
accomplished in accordance with the previous operator's schedule or
with the new operator's schedule, whichever would result in the
earlier accomplishment date for that leak check.
(2) For airplanes that have not been previously maintained in
accordance with this AD, the first leak check to be performed by the
new operator must be accomplished prior to further flight, or in
accordance with a schedule approved by the FAA PMI, but within a
period not to exceed 200 flight hours.
(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 PMI, who may add comments and then send it to the
Manager, Seattle ACO.
Note 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
Note 4: For any valve that is not eligible for the extended leak
check intervals of this AD: To be eligible for the leak check
interval specified in paragraphs (a)(1), (a)(2), (b)(2)(i), and
(b)(2)(ii), the service history data of the valve must be submitted
to the Manager, Seattle ACO, FAA, Transport Airplane Directorate,
with a request for an alternative method of compliance. One of the
factors that the FAA will consider in approving alternative valve
designs is whether the valve meets Boeing Specification S417T105 or
10-62213.
(g) Special flight permits may be issued in accordance with
Federal Aviation Regulations (FAR) 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 March 14, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-6340 Filed 3-17-94; 8:45 am]
BILLING CODE 4910-13-U
