[Federal Register Volume 62, Number 227 (Tuesday, November 25, 1997)]
[Proposed Rules]
[Pages 62708-62721]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-30855]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-111-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, 
and -500 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 all Boeing Model 737-100, -200, -300, -
400, and -500 series airplanes, which would have superseded an existing 
AD that currently requires either leak tests of the forward lavatory 
service system, and repair, as necessary; or draining the system and 
placarding the lavatory inoperative. That proposed AD would have 
provided an option for accomplishing terminating action for certain 
leak tests. It would have required leak tests of other lavatory drain 
systems; installation of a cap or vacuum break on the flush/fill line; 
and either periodic replacement of the seal for the cap and tank anti-
siphon valve or periodic maintenance of the vacuum break in the flush/
fill line. This action revises the proposed AD by removing the 
terminating action; requiring periodic changing of the seals of certain 
lavatory drain systems; replacing ``donut valves'' with other FAA-
approved valves; revising certain leak test intervals; and revising the 
pressurization and fluid level requirements for testing. The actions 
specified by this proposed AD are intended to prevent damage to 
engines, airframes, and property on the ground that is associated with 
the problems of ``blue ice'' that forms from leaking lavatory drain 
systems on transport category airplanes and subsequently dislodges from 
the airplane fuselage.

DATES: Comments must be received by January 5, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-111-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Don Eiford, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington; 
telephone (425) 227-2788; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be 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 95-NM-111-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this supplemental NPRM by 
submitting a request to the FAA, Transport Airplane Directorate, ANM-
103, Attention: Rules Docket No. 95-NM-111-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to all 
Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, was 
published as a notice of proposed rulemaking (NPRM) in the Federal 
Register on November 2, 1995 (60 FR 55673). That NPRM proposed to 
supersede AD 89-11-03, amendment 39-6223 (54 FR 21933, May 22, 1989), 
applicable to certain Boeing Model 737-300 and -400 series airplanes. 
That proposal would have continued to require either repetitive leak 
tests on the forward lavatory service system, and repair, as necessary; 
or draining of the system and placarding the lavatory inoperative. It 
would have also added a requirement to

[[Page 62709]]

perform leak tests of other lavatory drain systems; provided for the 
option of revising the FAA-approved maintenance program to include a 
schedule of leak tests; required the installation of a cap or vacuum 
break on the flush/fill line; and required either a periodic 
replacement of the seal for the cap and tank anti-siphon valve or 
periodic maintenance of the vacuum break in the flush/fill line. That 
proposal also would have expanded the applicability of the rule to 
include all Model 737 series airplanes.
    That NPRM was prompted by continuing reports of damage to engines 
and airframes, separation of engines from airplanes, and damage to 
property on the ground, caused by ``blue ice'' that forms from leaking 
lavatory drain systems on transport category airplanes and subsequently 
dislodges from the airplane fuselage. Such formation and dislodging of 
``blue ice,'' if not corrected, could result in damage to the engine 
and potential separation of the engine from the airplane.

Actions Since the Issuance of Previous NPRM

    Since the issuance of that previous NPRM, the FAA has received 
reports indicating that leakage of certain in-line valves of the 
lavatory waste drain systems has been detected. In consideration of 
this and other factors (a more detailed discussion of the other factors 
is presented later in this supplemental NPRM), the FAA has determined 
that the terminating action provided by the previous NPRM must be 
removed from this supplemental NPRM. In addition, the FAA has 
determined that certain additional changes to the previous NPRM are 
necessary.

Related AD's

    On November 9, 1994, the FAA issued AD 94-23-10, amendment 39-9073 
(59 FR 59124, November 16, 1994), which is applicable to Boeing Model 
727 series airplanes. That AD contains numerous requirements that are 
similar to those proposed in this action, which is applicable to Model 
737 series airplanes. In fact, several of the proposed requirements of 
this action are based on alternative methods of compliance that the FAA 
had approved previously for compliance with AD 94-23-10.
    The FAA is currently considering additional rulemaking to address 
the problems associated with ``blue ice'' on other transport category 
airplanes.

General Changes to the Proposal: Revision of Optional Maintenance 
Program

    As discussed previously, the FAA has received recent reports of 
leakage in certain in-line drain (ball) valves. In order to ensure that 
leak check results are uniformly reviewed before any extension of leak 
check intervals, the FAA has determined that the previously proposed 
optional terminating action provided for in paragraph (b) of the 
previous NPRM must be removed from this supplemental NPRM in order to 
maintain an adequate level of safety. The 5,000-hour leak test interval 
remains unchanged.

General Changes to the Proposal: Revised Leak Test Intervals for 
Certain Valves

    Based on recently received new data submitted by various operators, 
the supplemental NPRM would revise the previously proposed leak test 
intervals for certain valves. These changes have been added to 
paragraphs (a) and (b) of this supplemental NPRM. (A more detailed 
discussion of those proposed changes in the leak test intervals is 
presented later in the preamble.)

General Changes to the Proposal: Requirement To Change Seals

    One comment submitted to the Rules Docket in response to the 
previously issued NPRM, requests that a requirement to change the valve 
seals be added to paragraph (a) of the proposal. The commenter points 
out that if the seals are not changed periodically, they could fail and 
leak in between leak testing. The FAA concurs with the request, and has 
added a requirement to paragraph (a) of this supplemental NPRM to 
change the seals of valves at intervals similar to the proposed 
requirements of the valve seal changes in paragraph (b) of this 
supplemental NPRM.

General Changes to the Proposal: Requirement To Remove ``Donut'' 
Valves

    Another comment submitted to the Rules Docket in response to the 
previously issued NPRM, requests that the FAA mandate the removal of 
``donut'' style valves from the airplane and require replacement with 
one of the three service panel valves, as specified in the proposed 
rule. The commenter states that the ``donut'' valves have a long 
history of poor performance.
    The FAA concurs that the ``donut'' style valves should be removed. 
``Donut'' style valves have been involved in more cases of leakage and 
consequent formation of ``blue ice'' than any other valve design. In 
addition, cases of leakage of ``donut'' style valves that have been 
leak tested (as required by previous AD's) are still being reported. 
Therefore, the FAA has determined that the ``donut'' style valves 
should be removed.
    However, the FAA finds that, rather than require replacement of the 
``donut'' style valves with one of the three service panel valves 
listed in the previous NPRM, a requirement to replace the ``donut'' 
valves with ``an FAA-approved valve'' is more appropriate. This leaves 
an opportunity for operators to choose valves that may be ``FAA-
approved,'' but that may not be specified in the rule. Paragraphs 
(a)(6)(iii) and (b)(2)(iv)(C) of this supplemental NPRM have been 
revised to reflect this change.

General Changes to the Proposal: Revised Pressurization 
Requirements

    Several comments submitted to the Rules Docket in response to the 
previously issued NPRM included requests to revise the requirement to 
pressurize the airplane while performing leak tests to verify the 
integrity of in-line drain valves or service panel drain valves. The 
commenters state that applying a minimum pressure of 3 pounds per 
square inch differential pressure (PSID) across the line by using a 
leak test tool, such as a hand-held vacuum pump, would be just as 
effective as pressurizing the airplane, yet would provide a more 
economical method of accomplishing the leak test. Additionally, the 
commenters point out that using a 3 PSID differential pressure is 
consistent with the ``blue ice'' AD requirements for Boeing Model 727 
series airplanes.
    The FAA concurs. Paragraphs (a) and (b) of this supplemental NPRM 
have been revised to require the tests while applying a minimum 3 PSID 
differential pressure in the same direction as would occur during 
flight.

General Changes to the Proposal: Revised Requirement of Fluid Level

    Several comments submitted to the Rules Docket in response to the 
previously issued NPRM included requests that the FAA revise the 
proposed leak test procedure to empty and refill the lavatory to within 
two inches of overflowing. The commenters state that the difference 
between that specified level of fluid and actual overflowing of the 
fluid is approximately only one gallon. Since overflow of the lavatory 
could cause damage to the airplane, the commenters consider that any 
fluid above normal level (10 gallons) is unnecessary.

[[Page 62710]]

Therefore, the commenters request that the required fluid level be 
reduced.
    The FAA concurs that a lower fluid level is acceptable, except in 
the case of testing the anti-siphon valve. The FAA finds that fluid at 
the 10-gallon level is too low to result in fluid contacting the seals 
during the test of the anti-siphon valve; the lack of contact of the 
fluid with the seals would invalidate the test. Therefore, this 
supplemental NPRM has been revised to require that the lavatory be 
filled with a minimum of 10 gallons of fluid, except when testing the 
anti-siphon valve. However, operators should take precautions to ensure 
that the tank is not overfilled; a statement to this effect has been 
added to this supplemental NPRM.

Conclusion

    Since the changes described above expand the scope of the 
previously issued proposed rule, the FAA has determined that it is 
necessary to reopen the comment period to provide additional 
opportunity for public comment.

Comments Received

    Due consideration has been given to the comments received in 
response to the NPRM issued previously.

Support for the Proposal

    One commenter supports the proposed rule.

Request To Withdraw the Proposal: Risk of Injury From ``Blue Ice'' 
Is Extremely Remote

    The Air Transport Association (ATA) of America, on behalf of its 
members, requests that the proposed rule be withdrawn. The commenter 
considers that, from a statistical standpoint, the risk of injury to 
persons on the ground from falling ``blue ice'' is extremely remote.
    The FAA does not concur that the proposed rule should be withdrawn. 
The FAA has responded to the commenter on this issue during previous 
rulemaking concerning ``blue ice'' on Boeing Model 727 series 
airplanes. As stated in the preamble of that final rule, the FAA 
pointed out that demographic studies have shown that population density 
has increased around airports, and probably will continue to increase. 
These are populations that are at greatest risk of damage and injury 
due to ``blue ice'' dislodging from an airplane during descent. Without 
actions to ensure that leaks from the aft lavatory drain systems are 
detected and corrected in a timely manner, ``blue ice'' incidents would 
go untested and eventually someone would be struck, perhaps fatally, by 
falling ``blue ice.'' To discount the unsafe condition to persons on 
the ground presented by falling ``blue ice'' would be a gross breach of 
the FAA's safety obligations and commitment to the public.

Request To Withdraw the Proposal: Issue an Advisory Circular in 
Lieu of an AD

    This same commenter suggests that, if some type of action must be 
taken, a more manageable alternative to issuing an AD should be 
considered. The commenter suggests that such an alternative could be 
the development of an Advisory Circular (AC).
    The FAA does not concur that issuance of an AC would provide a 
``more manageable'' method of addressing the ``blue ice'' safety issue. 
In certain cases, the issuance of an AC is an appropriate first step to 
address a concern at a more informal level than an AD. In line with 
this approach, Advisory Circular 120-39, ``Hazards of Waste Water Ice 
Accumulation Separating from Aircraft in Flight,'' was issued on 
October 31, 1980. Paragraph 3. of that AC states, ``Each operator 
should initiate and accomplish inspections and maintenance of waste 
drain valves, caps, and heater systems to the extent necessary to 
ensure that these systems remain airworthy and function as designed, to 
prevent ice build-up from leaking waste water, and the resultant 
separation from the aircraft.'' The FAA concludes that the time elapsed 
since the issuance of that AC has given industry sufficient opportunity 
to make this approach work. The continuing problems with ``blue ice,'' 
however, demonstrate the need for a more definitive solution; this 
proposed rule is an appropriate approach.

Request To Revise Rulemaking Criteria To Ensure Level of Safety Is 
Cost Beneficial

    The ATA requests that the FAA redefine the criteria used to 
determine an ``unsafe condition'' so that the cost of rulemaking 
(airworthiness directives) is commensurate with the risks associated 
with not correcting the identified safety concern. Additionally, the 
commenter states that in meetings between the ATA and FAA management, 
participants agreed to a definition of ``airworthiness.'' The ATA would 
like to see that definition adopted for use in determining the need for 
an airworthiness directive. ATA states that without specific criteria 
and definitions of these terms, the FAA's determination of an unsafe 
condition and compliance period for adoption of the proposed rule must 
be viewed as subjective and, therefore, deficient as rulemaking.
    The FAA does not concur with the commenter's assertion that 
``without further guidance, the FAA's determination of an unsafe 
condition must be viewed as subjective and, therefore, deficient as 
rulemaking.'' The legal question is whether the FAA has identified an 
unsafe condition that may exist or develop in other products of the 
same type design. The FAA's determination on this issue is legally 
appropriate (and the rulemaking is not ``deficient'') as long as the 
FAA has a reasonable basis for that determination. In this supplemental 
proposed rule, the FAA finds that there is an unsafe condition based on 
reports of damage to engines, airframes, and property on the ground 
that is associated with the problems of ``blue ice'' that forms from 
leaking lavatory drain systems on transport category airplanes and 
subsequently dislodges from the airplane fuselage. Although these 
reasons may be characterized as ``subjective'' because they are 
qualitative rather than quantitative, the FAA considers them to be 
appropriate and sufficient to establish the reasonableness of this 
proposed action.

Request To Consider the Cost Impact to Airline Operators

    One commenter states that in order to standardize leak testing 
intervals at 1,000 and 4,500 flight hours, it will have to install a 
part in the aft drain system on its entire fleet, and in the forward 
drain system on airplanes that do not have Kaiser in-line ball valves 
installed in the forward drain system. The commenter requests that, 
since the annual cost for this will be $8,064, the FAA should 
reconsider that requirement.
    Another commenter asserts that compliance with the proposed rule 
will force airlines with good maintenance programs and high levels of 
``blue ice'' awareness to spend money accomplishing repetitive leak 
tests that will not add any additional levels of safety to the aircraft 
or to people on the ground. The commenter further states that the 
additional ground time required to perform these tests will also 
complicate scheduling and hamper efforts to increase aircraft 
utilization. The FAA infers that the commenter is requesting that the 
FAA reconsider the cost impact of the proposed action.
    The FAA acknowledges that the obligation to maintain aircraft in an 
airworthy condition is vital, but sometimes expensive. ``Blue ice''

[[Page 62711]]

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 reduction of the number of incidents of 
leakage by encouraging the use of more reliable equipment, and 
requiring that, if an incident of leakage does occur, it is detected 
and corrected in a timely manner.
    In addition, 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 proposal is unrealistic because, in the interest of 
maintaining safe aircraft, prudent operators would accomplish the 
proposed actions even if they were not required to do so.

Request To Distinguish Risks Associated With Forward and Aft 
Lavatories Drain Systems

    Two commenters note that the compliance times of the NPRM do not 
reflect a difference between risks associated with leakage from the 
forward lavatory drain system and the risks associated with leakage 
from the aft drain. One of the commenters asserts that operators who 
upgraded their forward lavatory systems to address the more significant 
safety concern over ice ingestion in engines would still be subject to 
the more stringent leak test intervals of the aft lavatory drain 
systems because of difficulties in redesigning and implementing 
retrofit of the aft lavatory drain systems. The commenters assert that 
the differences between the risks of leakage from the forward lavatory 
should be reflected by an adjustment to the proposed compliance times.
    The FAA does not concur that the risks associated with either the 
forward or aft lavatories should be distinguished by an adjustment to 
the proposed compliance times of the NPRM. As discussed previously, 
``blue ice'' detaching from the forward lavatory could cause damage to 
the engine and airframe, as well as present a hazard to persons on the 
ground; ``blue ice'' detaching from the aft lavatory presents a hazard 
to persons on the ground. Regardless of whether the formation of ``blue 
ice'' occurs on the forward or aft lavatory drain system, the resultant 
unsafe condition would exist. Even if the formation of ``blue ice'' on 
the aft lavatory drain systems may appear to be a less ``significant'' 
safety concern than the forward systems, a safety concern for those 
persons on the ground, nevertheless, still exists.

Request To Involve Principal Maintenance Inspectors (PMI)

    This same commenter, in reference to paragraph (b) of the previous 
NPRM, contends that it is more appropriate for the PMI, rather than the 
Seattle Aircraft Certification Office (ACO) engineering staff, to 
approve subsequent changes to the maintenance program once the program 
has been approved. The commenter considers that the PMI is more 
qualified than the ACO staff to approve tasks on training, reporting, 
and adjustment to the leak test intervals based upon reliability 
program recommendations. The commenter points out that the subject 
matter of the rule is clearly maintenance-related, and the ACO staff is 
not equipped to effectively respond to requests for maintenance 
interval changes that may occur. The commenter states that paragraph 
(b) of the proposal should be revised to include a statement that the 
AD is no longer applicable once a revision to the FAA-approved 
maintenance program is implemented.
    The FAA does not concur. Although the FAA agrees that the PMI 
should have oversight of most of the requirements of the proposed 
alternative maintenance program provision of the rule, the FAA does not 
agree that the PMI should be tasked with approving certain adjustments 
of the program. Failure threshold criteria and definitive leak/failure 
rate data do not exist for the majority of the subject valves; 
therefore, a PMI would have no data on which to base the approval of an 
extension of a leak test interval for many valves with the assurance 
that the valve would not fail within the adjusted interval. In light of 
this, 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 the PMI 
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 leak test intervals will maintain an 
acceptable level of safety.
    Further, the FAA considers it essential that any adjustment of the 
required leak test intervals, seal change intervals, and data reporting 
procedures should be approved in a uniform manner to ensure that the 
program is administered uniformly (and appropriately) fleetwide. The 
staff of the Seattle ACO is in the best position to ensure that this is 
accomplished. 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. In any case, the 
ACO staff will work closely with the cognizant PMI to ensure that any 
approved revisions to this aspect of the maintenance program are 
appropriate and workable for the applicable airline.

Request To Increase Leak Test Intervals for Pneudraulics Drain 
Valves

    Several commenters request that the leak test interval for 
Pneudraulics drain valve having part number (P/N) 9527-1 be increased 
from the proposed 1,000 flight hours. Two of the commenters requested 
the interval be increased to 2,000 flight hours; and one of the 
commenters, the valve manufacturer, requests that the interval be 
increased to 4,500 flight hours.
    The FAA concurs partially. Since the issuance of the NPRM, the FAA 
has received new data regarding the in-service performance of the 
Pneudraulics 9527 series drain valve. The data was obtained in 
accordance with procedures similar to those of paragraphs (b) and (c) 
of this supplemental NPRM. This data revealed that, only two leak tests 
failures were detected during a total time of 847,927 hours on 412 
Pneudraulics valves. In consideration of this data, the FAA finds that, 
for those operators who choose to comply with the requirements of 
paragraph (a) of the AD, this information justifies an increase of the 
leak test interval of Pneudraulics valves having P/N 9527 series from 
1,000 hours to 2,000 hours. Additionally, the FAA finds that, for 
operators who choose to comply with the maintenance option of paragraph 
(b) of the AD, this information justifies an increase of the leak test 
interval of the Pneudraulics valves P/N 9527 series from 1,000 hours to 
4,000 hours. Paragraphs (a) and (b) of this supplemental NPRM have been 
revised accordingly. However, if following the requirements of 
paragraphs (b) and (c) of this supplemental NPRM, similar data is 
gathered by a number of operators and are submitted to the FAA in 
support of an extension of the leak check interval for another type of 
valve, the FAA will consider extension of the leak check intervals for 
that valve for all operators using the valve.

[[Page 62712]]

Request To Increase Leak Test Intervals of Certain Other Shaw 
Valves

    One commenter states that its fleet has a mixture of valves that 
have been modified in accordance with Shaw Service Bulletin SB 
10101000B-38-1, and valves that have not been modified in accordance 
with that service bulletin. The operator requests that the currently 
proposed leak test interval of 600 flight hours (for the valves that 
have not been modified in accordance with the service bulletin) be 
increased to equal the 1,000 flight hour leak test interval of the 
valves modified in accordance with that service bulletin. Because of 
the operator's high level of awareness, it sees no safety compromise in 
requiring the unmodified valves to be leak tested at 1,000 flight 
hours.
    The FAA does not concur. The modifications described by the subject 
service bulletin were designed to make the valves less likely to leak. 
Therefore, the leak test interval is permitted to be increased only for 
those valves that have been modified in accordance with Shaw Service 
Bulletin SB 1010000B-38-1.

Request To Increase Leak Test Interval for Other Shaw Valves

    One commenter, a valve manufacturer, requests that the leak test 
interval for certain Shaw valves be extended from 1,000 flight hours to 
2,000 flight hours when the maintenance procedures have been revised 
and data have been submitted to substantiate the increased interval.
    The FAA concurs that when maintenance procedures have been revised 
and data have been submitted to substantiate the increased interval, 
approval may be granted to increase the leak test intervals. Under the 
provisions of this supplemental NPRM, an operator has the option of 
proposing a change to its maintenance program, gathering data, and 
making a request for extension of the leak test interval. Operators 
interested in this option should contact the Seattle Aircraft 
Certification Office to discuss implementation of this option before 
submitting the request to extend the leak test intervals. If a number 
of operators successfully follow this procedure and provide data 
similar to that provided for the Pneudraulics P/N 9527 series valve, 
the FAA will consider an ``across the board'' increase for extension of 
the leak check interval for the valve that they are using. This 
procedure is applicable to valve manufacturers as well.

Request To Increase Interval of Replacement of Pneudraulics Valve 
Seals

    One commenter, an operator, requests that the replacements of the 
seals of the Pneudraulics valves be extended from the proposed ``prior 
to 5,000 flight hours after the effective date of the AD, and 
thereafter at intervals not to exceed 18 months,'' to replacement of 
the seal ``every third leak test of the drain system, or every 6,000 
flight hours.'' The commenter states that implementation of the revised 
compliance times would provide a scheduling convenience, and would 
still maintain an acceptable level of safety.
    The FAA concurs that the intervals for the repetitive replacements 
can be extended somewhat. Since the Pneudraulics valve seals are 
similar to those used in the in-line drain valves and replacement of 
those seals are approved for longer replacement intervals, the FAA has 
revised paragraphs (a)(1)(ii) and (b)(1)(ii) of this supplemental NPRM 
to require accomplishment of repetitive seal replacements at intervals 
not to exceed 18 months or 6,000 flight hours, whichever occurs later.

Request To Revise Compliance Times for Certain Seal Changes

    One commenter, the airplane manufacturer, requests that the 
proposed rule be revised to provide for an alternative repetitive 
interval for accomplishment of the seal changes. Specifically, the 
commenter requests that, ``or within 48 months after the last 
documented seal change'' be added after the proposed repetitive 
interval of ``5,000 flight hours'' in paragraph (b)(1)(i) of the 
proposed rule. The commenter states that this alternative repetitive 
interval would prevent unnecessary seal changes for operators that have 
recently performed the seal change.
    The FAA concurs that the requested alternative repetitive interval 
would prevent unnecessary seal changes for operators that have recently 
performed the seal change. The FAA considers that those alternative 
repetitive intervals provide an equivalent level of safety. Therefore, 
the FAA has revised paragraph (b)(3) of this supplemental NPRM (which 
appeared as paragraph (b)(1) of the previous proposal). The FAA also 
has made a corresponding change to paragraph (a)(8) of this 
supplemental NPRM since it is similar to the requirements of paragraph 
(b)(3) of the supplemental NPRM.

Request To Delete Certain Seal Part Numbers

    One commenter, the airplane manufacturer, requests that valve seal 
part numbers 2651-329, 2651-334, 10101000C-G, 10101000C-M, and 
1010000C-R be deleted from the proposal. The commenter considers that 
part numbers that have not been installed, either in production or 
retrofit, on Boeing Model 737 series airplanes should not be cited in 
the NPRM. The FAA concurs with the commenter's remarks, and has removed 
all references to those parts numbers from this supplemental NPRM.

Request To Mandate Leak Testing of All Seals in the Lavatory System

    One commenter notes that, while the previous NPRM proposes leak 
testing of the dump valve seal and the inner seal of the drain valve of 
the service panel, no testing of the outer cap/door seal is required. 
The commenter states that since the outer cap/door seal is the ``last 
resort'' in preventing leakage of ``blue ice,'' leak testing should be 
required of the outer cap/door.
    The FAA does not concur. Some valve designs are such that the valve 
must be partially disassembled (removing the inner seal, interlocking 
inner plugs, etc.) to allow the outer door to be tested, which would 
invalidate the test of the inner seal. Additionally, different valve 
designs may require valve disassembly and reassembly as part of the 
test procedure with different test procedures for different valve 
designs. These factors complicate the specification of a usable test of 
both inner and outer doors for all existing valve designs. Therefore, 
the FAA finds that the requirement to apply 3 PSID across the valve 
inner door and to visually inspect the outer door seal for damage that 
could cause leakage on all service panel valves to be adequate and 
appropriate. However, if an operator prefers to test the outer door and 
inspect the inner door, the FAA will consider requests for an 
alternative method of compliance as provided in paragraph (f) of this 
proposed AD.

Request To Require a Lever Lock Cap and a Vacuum Breaker Check 
Valve

    One commenter states that, instead of permitting a vacuum breaker 
check valve to be used as an alternative to the installation of a lever 
lock cap, the FAA should require both of them. The commenter states 
that a long history of poor performance of check valves and lever lock 
caps indicates that a redundant system requiring both the valve and cap 
would have greater reliability.

[[Page 62713]]

    The FAA does not concur in this case. The FAA acknowledges that 
redundant systems generally provide a higher level of safety; however, 
in this case, redundancy to the check valve function is provided by the 
vacuum breaker. In the case of a check valve alone, the lever lock cap 
provides redundancy to the check valve. There are insufficient data to 
show which combination is more reliable.
    However, service history information indicates that vacuum breaker 
check valves with poppet check valves (rather than mushroom check 
valves) have a greater reliability record. Therefore, the FAA has 
removed reference to Monogram Part Number 3765-175 (mushroom type) from 
paragraphs (a) and (b) of this supplemental NPRM. By requiring repair 
of leaking components when ``blue streaks'' are observed, the FAA 
intends that operators, through their own experience, will determine 
which combination of valves works the best to avoid leakage. However, 
if the FAA receives data indicating service problems or unreliability 
with vacuum breaker check valves using poppet checks, the FAA may 
consider further rulemaking action.

Request To Revise Approvals of Certain Vacuum Breakers

    Two commenters request that the approval of vacuum breakers, as 
referenced in the proposed rule, be revised. One commenter requests 
that reference to all Monogram part number series 3765-175 or 3765-190 
series be deleted, and replaced with ``* * * an FAA-approved check 
valve with a vacuum breaker * * *,'' or replaced with a specific 
reference to valves having Shaw part number 301-0009-01. This commenter 
states that the vacuum breaker check valves leaked, and should not be 
provided as an alternative to installation of a lever lock cap on the 
flush/fill line. The other commenter requests that instead of 
specifying particular part numbers, the approval reference should be to 
``* * * an FAA-approved vacuum break in the * * *.'' This commenter 
considers that this would cover all vacuum breaker manufacturers.
    The FAA concurs partially. The FAA has reviewed available service 
history data and concluded that vacuum breaker check valves of the 
poppet type (such as Monogram part number series 3765-190) have fewer 
reports of leakage than the vacuum breaker test valves of the mushroom 
type (such as Monogram part number 3765-175). Therefore, as stated 
previously, the FAA has removed reference to Monogram part number 3765-
175 as an approved valve from this supplemental NPRM.
    The FAA also has reviewed the design of Shaw part number 301-0009-
01, which is a vacuum breaker check valve of the poppet type, and has 
added it as an acceptable part number in paragraphs (a)(8)(ii) and 
(b)(3)(ii) of this supplemental NPRM.
    Additionally, since the issuance of the previous NPRM, another 
acceptable valve for the flush/fill line has been certified. The 
installation of Kaiser Electroprecision flush/fill ball valve part 
number series 0062-0009 has been added to paragraphs (a)(8)(iii), 
(b)(3)(iii), and (d)(3) of this supplemental NPRM as an alternative 
method of preventing leakage from the flush/fill line.

Request To Shorten Leak Test Intervals of Flush/Fill Caps

    The commenter states that there is no discussion in the proposal of 
what would prompt an airline to ensure flush/fill caps are installed in 
all positions prior to each flight. The commenter contends that it is 
common practice for caps to be removed from airplanes due to their 
nuisance value. The commenter also states that the flush/fill caps, as 
well as the lever lock caps, are difficult to operate and commonly have 
the seals removed, which render them inoperable on the airplane. The 
commenter considers the ease with which the seal is removed is a design 
flaw of the valve itself. Therefore, the commenter requests that 
another device be considered instead of the flush/fill caps that is not 
on the exterior of the aircraft and cannot be tampered with by ground 
maintenance personnel. The commenter notes that a device incorporated 
further upstream with positive shut-off and anti-siphon features would 
eliminate the ``blue ice'' that occurs at the flush/fill port. 
Therefore, the commenter requests that, until such a device can be 
developed and FAA-approved, the leak tests and inspections of this area 
should be performed more frequently.
    The FAA does not concur with the commenter's request. The FAA does 
not consider it necessary to require an additional inspection to ensure 
installation of the flush/fill caps when they are installed in 
accordance with an AD. If, as the commenter asserts, cases of 
uninstalled flush/fill caps commonly occur, the FAA does not find that 
reason to assume that operators would continue that practice in the 
future if operation without the flush/fill caps would be a violation of 
an AD. Further, lever lock caps are specified by this supplemental NPRM 
precisely because they must be in the closed position to allow the 
service panel door to be closed. In addition, this supplemental NPRM 
specifies that if there is evidence of leakage, the leaking device must 
be corrected, or the lavatory drained and placarded inoperative. 
Therefore, if seals or caps are removed and result in leakage, this 
provision will ensure that the system is repaired before the lavatory 
is returned to service.
    Additionally, the FAA notes that the vacuum break poppet type check 
valves specified in the previous NPRM can be used as an alternative to 
using lever lock caps. The FAA is not aware of any data, presently, 
that supports an increase or decrease in the leak test intervals of the 
devices on the flush/fill line. Consequently, this supplemental NPRM 
contains neither an increase nor a decrease in the leak test intervals 
of these devices. However, if such data becomes available that supports 
a decrease in the leak test intervals, the FAA may consider additional 
rulemaking.

Request To Revise the Leak Test of the Inner Door of the Service 
Panel Drain Valve

    Several commenters request that the leak test of the inner door of 
the service panel drain be revised to require the test to be run with 
the outer door open when using a vacuum box so that the 3 PSID 
differential is applied across the inner door. One of these commenters, 
the airplane manufacturer, points out that if the outer door seal is 
good, the inner door seal will not reflect a pressure differential. For 
this reason, the FAA concurs. The FAA has revised the supplemental NPRM 
to specify that the test be run with the outer door open when using a 
vacuum box.

Request To Revise Testing of Drain Panel Valves

    One commenter requests that testing of the drain valves cover both 
the inner door of the valve and the outer door/cap of the valve. The 
commenter also notes that some valves have their primary seals on the 
outer doors, not the inner doors, so that omitting the test of the 
outer door, as proposed in the NPRM, results in the primary seal of the 
valve being untested.
    The FAA does not concur. As discussed previously in the request to 
mandate leak testing of all seals in the lavatory system, the FAA has 
revised the requirements of the leak testing of the drain valves of 
service panels to require applying 3 PSID across the valve inner door 
and visually inspecting the outer door seal for damage. This approach 
should adequately test valves with inner and outer doors. However, if

[[Page 62714]]

an operator elects to test the outer door and visually inspect the 
inner door, that operator should apply for approval of an alternative 
method of compliance under the provisions of paragraph (f) of this 
supplemental NPRM.

Request To Require Visual Inspection of the Outer Cap/Door

    Two commenters request that paragraphs (a)(4) and (b)(2)(iii) of 
the proposal be revised to delete the requirement to perform a leak 
test of the outer door of ``donut'' type valves, and add a visual 
inspection of the outer doors instead. The commenters state that the 
``donut'' valves are similar to other valves in that they provide two 
sealing surfaces. The commenters note that for those other valves, the 
proposal would require only a test of the inner door or the sealing 
surface.
    The FAA concurs and has revised paragraphs (a)(4) and (b)(2)(iii) 
of this supplemental NPRM accordingly. In light of the fact that this 
supplemental NPRM would require eventually removing all ``donut'' 
valves and replacing them with FAA-approved valves, the FAA finds that, 
in the interim, a visual inspection of the outer doors, rather than a 
leak test, will ensure an acceptable level of safety.

Request To Require a Leak Test of the Outer Door of the Service 
Panel Drain

    Another commenter states that since the FAA required it to perform 
the leak test of the outer door, the rules for testing the service 
panel drain should not be changed at this time. The commenter states 
that by requiring leak tests only of the inner door, the proposal 
provides an unfair competitive advantage in favor of its competitors 
because some valves have their primary seals on the outer doors instead 
of the inner doors. In addition, by not requiring a leak test of the 
outer door, the actual primary seal of the valve would not be tested.
    The FAA does not concur with the request to require leak tests of 
the outer door seal. The FAA finds that performing a leak test of the 
inner door and visual inspections of the outer door provide an 
acceptable level of safety. However, if an operator chooses to test the 
outer door and visually inspect the inner door, under the provisions of 
paragraph (f) of this supplemental NPRM, that operator may request 
approval of an adjustment of this requirement if data are submitted to 
substantiate that such an adjustment would provide an acceptable level 
of safety.

Request To Extend Leak Test Intervals in Paragraph (b) of the 
Proposal

    Several commenters state that the leak test intervals specified in 
paragraph (b) of the proposal should be relaxed so that operators would 
be encouraged to select it as an alternative to the accomplishment of 
the requirements of paragraph (a) of the proposal. One of the 
commenters states that this same request was made in response to the 
proposed rule concerning ``blue ice'' for Boeing Model 727 series 
airplanes, and that the FAA did not respond to that request. Several 
commenters assert that paragraph (b) of the proposal should 
additionally provide terminating action once an operator's FAA-approved 
maintenance plan has been incorporated.
    The FAA does not concur with the commenters' request to increase 
the leak test intervals specified in paragraph (b) simply in order to 
encourage operators to choose that option. For the reasons specified 
previously under the ``General Changes to the Proposal: Revision of 
Optional Maintenance Program'' section of this supplemental NPRM, the 
FAA finds that the previously proposed terminating action must be 
deleted. Further, the expansion of leak test intervals that are 
included in paragraph (b) of this supplemental NPRM is primarily 
related to the reliability of the waste drain valves involved. The 
additional requirements of paragraph (b) provide assurance that 
expansion of the intervals will not result in significant leakage 
events in the time between the leak tests. The FAA included paragraph 
(b) of this supplemental NPRM not only because it does contain certain 
``attractive'' features, but also to provide a format for verifiable 
empirical data to serve as a reliability indicator for the waste drain 
valves. To date, three operators have opted to follow requirements 
similar to those provided in paragraph (b) of this supplemental NPRM. 
The FAA concludes, therefore, that compliance with the optional 
provisions of paragraph (b) of this supplemental NPRM is of value to 
some operators.
    Additionally, in reviewing the preamble of AD 94-23-10 (applicable 
to Boeing Model 727 series airplanes), the FAA finds that the 
commenter's request regarding the leak test intervals of paragraph (b) 
of that AD was specifically addressed in the final rule. The FAA's 
response noted the revision of several requirements of paragraph (b) of 
that final rule to make it more ``attractive'' to operators; certain of 
those revised requirements included extended leak test intervals for 
some valves.

Request To Revise Leak Test Intervals for Service Panel Drain 
Valves

    The airplane manufacturer requests that paragraph (b)(2)(ii) of the 
proposal be revised to increase the replacement interval of the service 
panel drain valves from 1,000 flight hours to 2,000 flight hours. The 
commenter states that increasing this interval would not decrease the 
level of safety because of other requirements of paragraph (b) of the 
proposal. Further, the commenter notes that two alternative methods of 
compliance have been granted to increase the interval to 2,000 flight 
hours.
    The FAA does not concur with the commenter's request to increase 
the leak test interval ``across the board'' for service panel drain 
valves at this time. However, if data are submitted for specific 
service panel drain valves in accordance with the data gathering 
requirements of paragraph (b) of this supplemental NPRM, the FAA will 
review the data and may consider extending the leak test intervals 
accordingly. If a number of operators have successfully accomplished 
such programs, the FAA will evaluate all the data submitted for a 
particular valve and consider an ``across the board'' extension of the 
leak test interval.

Request for Clarification of Compliance Times

    The airplane manufacturer requests that compliance times in 
paragraph (b)(4) of the proposal be revised. That proposed compliance 
time is currently specified as ``* * * at intervals not to exceed 4 
calendar days or 45 flight hours, whichever occurs later.'' The 
commenter requests that the phrase ``not to exceed'' be deleted and 
replaced with the word ``of.'' The manufacturer states that the phrase 
``not to exceed'' appears to be in conflict with the phrase ``* * *  
whichever occurs later.'' Therefore, the manufacturer suggests revising 
the compliance time to read ``at intervals of 4 calendar days or 45 
flight hours, whichever occurs later.''
    The FAA does not concur that the phrases are in conflict with each 
other. The phrases ``at intervals not to exceed 4 calendar days or 45 
flight hours, whichever occurs later'' are standard phrasing the FAA 
uses routinely in providing certain compliance times. The phrase, ``not 
to exceed,'' allows accomplishment of the required action at 
frequencies less than the specified intervals. The phrase, ``whichever 
occurs later,'' allows an operator to select the means of measuring the

[[Page 62715]]

interval that results in less frequent accomplishment of the required 
actions, depending upon the operator's individual utilization rates. 
Therefore, no change of compliance time is required to paragraph (b)(4) 
of the supplemental NPRM.

Request To Incorporate Paragraph (b) Into Paragraph (f) of the 
Proposal

    One commenter considers that the provisions in paragraph (b) of the 
NPRM are merely guidelines for submitting alternative methods of 
compliance. Therefore, the commenter requests that paragraph (b) of the 
proposal be incorporated into the paragraph that specifically addresses 
alternative methods of compliance [paragraph (f) of the proposal].
    The FAA does not concur. The maintenance option provided by 
paragraph (b) of this supplemental NPRM provides for the acquisition of 
data that are required to justify extending leak test intervals. 
Compliance with paragraph (b) of the supplemental NPRM is an approved 
method of establishing empirical data on valve reliability. The FAA 
sees no added value in changing the paragraph numbering of the 
proposal. Moreover, the FAA considers that a change in the numbering of 
the paragraphs would have the potential for added confusion since an 
existing AD for the Boeing Model 727 series airplanes concerning ``blue 
ice'' also has paragraph (b) designated as the maintenance option.

Request To Revise Test Requirements for Flush/Fill Line Anti-Siphon 
Valves

    The airplane manufacturer requests that paragraph (b)(3) of the 
proposal be revised from ``Thereafter, repeat the requirements at 
intervals not to exceed 5,000 flight hours'' to ``Thereafter, repeat 
the requirements at intervals not to exceed 5,000 flight hours or 24 
months.'' The commenter notes that the paragraph would then be 
consistent with the test requirements of the in-line drain valve in 
paragraph (b)(2)(i) of the proposal.
    The FAA does not concur. The compliance times for testing the in-
line drain valves specified in paragraph (b)(2)(i) of the supplemental 
NPRM were based on supportive data to justify those times. The FAA has 
not received data justifying a similar compliance time for the flush/
fill line anti-siphon valve.

Request To Clarify Table 1 of the Proposal

    One commenter, a valve manufacturer, requests that specific Shaw 
Aero valves approved for a leak test interval of 1,000 flight hours be 
clarified. The FAA has revised Table 1 of this supplemental NPRM to 
clarify specifically which Shaw valves have been approved for use on 
Boeing Model 737 series airplanes.

Request To Base Leak Test Intervals for Valves on Valve Quality

    One commenter states that it is more important to use a quality 
valve than a ``maintenance program'' to ensure reliability. The 
commenter asserts that maintenance programs should be required of all 
airlines, so that leak test intervals would be based on the quality and 
performance of the hardware.
    The FAA does not concur that claims of valve quality should be the 
only basis for determining leak test intervals, or that all operators 
should be required to follow the requirements of the optional 
maintenance program [paragraph (b) of the supplemental NPRM]. Extension 
of the leak test interval is based primarily upon hardware reliability, 
as stated elsewhere in this supplemental NPRM. However, verification of 
the actual reliability of the hardware is difficult to determine. 
Review of maintenance data that is obtained through the maintenance 
program and verified by FAA Flight Standards plays a major role in 
determining the extension of leak test intervals. Although valve 
manufacturers and some operators claim that the hardware and systems 
currently in service are providing adequate levels of safety, incidents 
of ``blue ice'' continue to occur.
    Since leakage from the waste system is not a reportable event 
according to part 21 of the Federal Aviation Regulations (14 CFR part 
21), the FAA included the provisions of paragraph (b) of the proposal 
to make leakage from the waste system a reportable event. Those 
operators who choose to compile that data will have documented 
information to submit to the FAA as a basis for increasing leak test 
intervals. As stated earlier, the FAA has already used this program to 
extend the leak test interval for a certain valve.
    With regard to the commenter's statement that all operators should 
be required to follow a maintenance program, the FAA has incorporated 
requirements to periodically change valve seals and correct any leakage 
found in accordance with paragraph (a) of this supplemental NPRM. The 
more extensive requirements of the maintenance program specified in 
paragraph (b) of the supplemental NPRM provide assurance that 
significant leakage will not occur during the expanded leak test 
intervals.

Request To Increase Certain Leak Test Intervals

    The ATA asserts that leak test intervals of every 200 flight hours 
for certain drain system valves cannot be justified based on safety 
concerns with ``blue ice.'' The ATA requests that those leak test 
intervals be extended.
    The FAA does not concur. The current leak test interval for certain 
drain system valves is every 200 flight hours, as required by AD 89-11-
03. Nevertheless, the FAA has continued to receive reports of damage to 
airplanes. The FAA intends to increase the leak test interval only for 
those valves documented to be reliable, in accordance with the proposed 
requirements of this supplemental NPRM.

Request for Definition of ``Vent Line''

    Another operator requests that the term ``vent line'' be defined 
specifically. The commenter questions if ``vent line'' as cited in the 
proposed AD refers only to the portion of the line shown on the 
Monogram check valve.
    The FAA acknowledges that clarification is necessary. The vent line 
vacuum breaker is that portion of the valve and vent line that 
functions as a vacuum breaker, as opposed to the part of the valve 
performing a ``check valve'' function. The intent of the previous NPRM 
was to perform maintenance on the vacuum breaker check valve and ensure 
that the vacuum break feature operates correctly. For clarification 
purposes, reference to the term ``vent line'' has been removed from 
this supplemental NPRM, and the applicable paragraphs have been revised 
to reference a ``vent line vacuum breaker.''

Request To Revise Reference to Service Information

    The airplane manufacturer advised that the correct service 
bulletins that should be cited in paragraph (f)(2) of the proposal are 
Boeing Service Bulletins 737-38-1026 (lavatory A), and 737-38-1031 
(lavatory F). Those service bulletins describe alternative methods of 
compliance with the requirements of only paragraph (a)(2) of the 
supplemental NPRM. The FAA inadvertently cited an incorrect service 
bulletin in the previous NPRM; the supplemental NPRM has been revised 
to cite the correct service bulletins.

Request To Change Reference to Certain Drain System Valves

    One commenter requests that the description of the ``donut'' valves 
in paragraphs (a)(4) and (b)(2)(iii) of the NPRM be expanded to read, 
``For each lavatory drain system that incorporates

[[Page 62716]]

``donut'' plugs (Kaiser Electroprecision, part number 4259-20 or 4259-
31), or FAA-approved equivalent, or incorporates Kaiser 
Electroprecision cap/flange, part numbers * * *.'' The FAA concurs, and 
has revised paragraphs (a)(6) and (b)(2)(iv) of this supplemental NPRM 
[which appeared as paragraphs (a)(4) and (b)(2)(iii), respectively, of 
the previous NPRM] to provide clarification concerning the specific 
``donut'' valves, as suggested by the commenter.

Request To Revise Notes 3 and 5 of the Proposal

    The airplane manufacturer requests that Notes 3 and 5 of the NPRM 
be corrected to reference Boeing Maintenance Manual Section 38-32-00/
501 instead of the currently referenced Boeing service letter.
    The FAA acknowledges that Boeing Maintenance Manual Section 38-32-
00/501 is the appropriate guidance for the testing, and has revised 
Note 3 of this supplemental NPRM accordingly. However, since reference 
to guidance for performing leak tests specifically addressed in Note 5 
of the previous NPRM is no longer necessary or applicable, it has been 
removed from this supplemental NPRM. (Note 5 of this supplemental NPRM 
now contains information unrelated to NOTE 5 of the previous NPRM.)

Request To Delete Reference to Development of Future In-Line Drain 
Valves

    One commenter, a valve manufacturer, requests that reference to the 
development of future in-line drain valves that would provide for 
possible terminating action be deleted from the proposal since that 
statement may mislead airlines and other interested parties to think 
that development and approval of those valves is currently in progress. 
The commenter states that the NPRM is a place for facts, not 
supposition of what might be. The commenter further states that it 
believes it has been ``damaged'' by mention of a future valve, 
specifically when the FAA has not considered existing in-service data 
concerning the reliability of this manufacturer's valves.
    The FAA acknowledges the commenter's request. The FAA has removed 
reference to current in-line drain valves, as well as possible future 
development of those valves, from consideration as terminating action 
for certain requirements of this supplemental NPRM. As discussed 
previously in the preamble of this supplemental NPRM, the FAA has 
determined that terminating action for the leak testing of the in-line 
valves under an approved maintenance program is no longer appropriate, 
based on recent reports of leakage of drain systems with in-line drain 
valves installed.
    In addition, it is common practice for the FAA to provide 
information in NPRM's concerning possible development and approval of 
various corrective actions. For example, in certain cases, compliance 
times for corrective actions are based on a time frame that is 
determined to be adequate in order to develop, approve, and install 
such corrective actions, e.g., repair, parts, or modifications. 
Establishment of a reasonable compliance time enables the manufacturer 
to plan its schedules and resources so that the corrective action is 
made available to the airlines well within the compliance time 
established by an AD. For these reasons, the FAA finds that the 
development and approval of future parts, repair, or modifications are 
not only relevant to discussions in proposed rules, they are, in 
certain cases, inherent to the discussion itself.

Economic Impact

    There are approximately 2,410 Model 737 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 1,031 
airplanes of U.S. registry and 110 U.S. operators would be affected by 
this proposed AD.
    The proposed waste drain system leak test and outer cap inspection 
would take approximately 6 work hours per airplane to accomplish, at an 
average labor rate of $60 per work hour. Based on these figures, the 
cost impact on U.S. operators of these proposed requirements of this AD 
is estimated to be $371,160, or $360 per airplane, per test/inspection.
    Certain airplanes (i.e., those that have ``donut'' type drain 
valves installed) may be required to be leak tested as many as 15 times 
each year. Certain other airplanes having other valve configurations 
would be required to be leak tested as few as 3 times each year. Some 
airplanes that have various combinations drain valves installed would 
require approximately 2 leak tests of one drain valve and 3 leak tests 
of the other drain valve each year. Based on these figures, the annual 
(recurring) cost impact of the required repetitive leak tests on U.S. 
operators is estimated to be between $1,080 and $5,400 per airplane per 
year.
    With regard to replacement of ``donut'' type drain valves, the cost 
of a new valve is approximately $1,200. However, the number of leak 
tests for an airplane that is flown an average of 3,000 flight hours a 
year is thereby reduced from 15 tests to 3 tests. The cost reduction 
because of the number of tests required is approximately equal to the 
cost of the replacement valve. Therefore, no additional cost is 
incurred because of this change.
    The FAA estimates that it would take approximately 1 work hour per 
airplane lavatory drain to accomplish a visual inspection of the 
service panel drain valve cap/door seal and seal mating surfaces, at an 
average labor cost of $60 per work hour. As with leak tests, certain 
airplanes would be required to be visually inspected as many as 15 
times or as few as 3 times each year. Based on these figures, the 
annual (recurring) cost impact of the required repetitive visual 
inspections on U.S. operators is estimated to be between $180 and $900 
per airplane per year.
    The proposed installation of the flush/fill line cap would take 
approximately 1 work hour per cap to accomplish, at an average labor 
rate of $60 per work hour. The cost of required parts would be $275 per 
cap. There are an average of 2.5 caps per airplane. Based on these 
figures, the cost impact on U.S. operators of these proposed 
requirements of this AD is estimated to be $863,463, or $838 per 
airplane.
    The addition of the seal change requirement to paragraph (a) will 
require approximately 2 work hours to accomplish, at an average labor 
cost of $60 per hour. The cost of required parts would be $200 per each 
seal change. Based on these figures, the cost impact on U.S. operators 
of these proposed requirements of this AD is estimated to be $329,920, 
or approximately $320 per airplane per year.
    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 could 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 should be minimal.
    In addition to the costs discussed above, for those operators who 
elect to comply with proposed paragraph (b) of this proposed AD action, 
the FAA estimates that it would take approximately 40 work hours per 
operator to incorporate the lavatory drain system leak test procedures 
into the maintenance programs, at an average

[[Page 62717]]

labor cost of $60 per work hour. Based on these figures, the cost 
impact of the proposed maintenance revision requirement of this AD 
action on the 110 U.S. operators is estimated to be $264,000, or $2,400 
per operator.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    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, 
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 the original 
cost-beneficial level of safety is no longer being achieved and that 
the required 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 
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 removing amendment 39-6223 (54 FR 
21933, May 22, 1989), and by adding a new airworthiness directive (AD), 
to read as follows:

Boeing: Docket 95-NM-111-AD. Supersedes AD 89-11-03, Amendment 39-
6223.

    Applicability: All Boeing Model 737 series 100, 200, 300, 400 
and 500 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 (f) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent engine damage, 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 or flush/fill 
systems and dislodged from the airplane, accomplish the following:
    (a) Except as provided by paragraph (b) of this AD, accomplish 
the applicable requirements of paragraphs (a)(1) through (a)(9) of 
this AD at the time specified in each paragraph. If the waste drain 
system incorporates more than one type of valve, only one of the 
waste drain system leak test procedures (the one that applies to the 
equipment with the longest leak test interval) must be conducted at 
each service panel location. The waste drain system valve leak tests 
specified in this AD shall be performed in accordance with the 
following requirements: fluid shall completely cover the upstream 
end of the valve being tested; the direction of the 3 pounds per 
square inch differential pressure (PSID) shall be applied across the 
valve in the same direction as occurs in flight; the other waste 
drain system valves shall be open; and the minimum time to maintain 
the differential pressure shall be 5 minutes. Any revision of the 
seal change intervals or leak test intervals must be approved by the 
Manager, Seattle Aircraft Certification Office (SACO), FAA, 
Transport Airplane Directorate.
    (1) Replace the valve seals in accordance with the applicable 
schedule specified in paragraphs (a)(1)(i), (a)(1)(ii), and 
(a)(1)(iii) of this AD.
    (i) For each lavatory drain system that has an in-line drain 
valve installed, Kaiser Electroprecision part number series 2651-
278: Replace the seals within 5,000 flight hours after the effective 
date of this AD, or within 48 months after the last documented seal 
change, whichever occurs later. Thereafter, repeat the replacement 
of the seals at intervals not to exceed 48 months.
    (ii) For each lavatory drain system that has a Pneudraulics part 
number series 9527 valve: Replace the seals within 5,000 flight 
hours after the effective date of this AD, or within 18 months of 
the last documented seal change, whichever occurs later. Thereafter, 
repeat the replacement of the seals at intervals not to exceed 18 
months or 6,000 flight hours, whichever occurs later.
    (iii) For each lavatory drain system that has any other type of 
drain valve: Replace the seals within 5,000 flight hours after the 
effective date of this AD, or within 18 months after the last 
documented seal change, whichever occurs later. Thereafter, repeat 
the replacement of the seals at intervals not to exceed 18 months.
    (2) For each lavatory drain system that has an in-line drain 
valve installed, Kaiser Electroprecision part number series 2651-
278: Within 4,500 flight hours after the effective date of this AD, 
and thereafter at intervals not to exceed 4,500 flight hours, 
accomplish the procedures specified in paragraphs (a)(2)(i) and 
(a)(2)(ii) of this AD:
    (i) Conduct a leak test of the toilet tank dump valve (in-tank 
valve that is spring loaded closed and operable by a T-handle at the 
service panel) and the in-line drain valve. The toilet tank dump 
valve leak test must be performed by filling the toilet tank with a 
minimum of 10 gallons of water/rinsing fluid and testing for leakage 
after a period of 5 minutes. Take precautions to avoid

[[Page 62718]]

overfilling the tank and spilling fluid into the airplane. The in-
line drain valve leak test must be performed with a minimum of 3 
PSID applied across the valve.
    (ii) If a service panel valve or cap is installed, perform a 
visual inspection of the service panel drain valve outer cap/door 
seal and the inner seal (if the valve has an inner door with a 
second positive seal), and the seal mating surfaces for wear or 
damage that may allow leakage.
    (3) For each lavatory drain system that has a service panel 
drain valve installed, Pneudraulics part number series 9527: Within 
2,000 flight hours after the effective date of this AD, accomplish 
the requirements of paragraphs (a)(3)(i) and (a)(3)(ii) of this AD. 
Thereafter, repeat the leak tests at intervals not to exceed 2,000 
flight hours.
    (i) Conduct leak tests of the toilet tank dump valve and service 
panel drain valve. The toilet tank dump valve leak test must be 
performed by filling the toilet tank with a minimum of 10 gallons of 
water/rinsing fluid and testing for leakage after a period of 5 
minutes. Take precautions to avoid overfilling the tank and spilling 
fluid into the airplane. The leak test of the service panel drain 
valve must be performed with a minimum of 3 PSID applied across the 
valve inner door/closure device.
    (ii) Perform a visual inspection of the outer cap/door and seal 
mating surface for wear or damage that may cause leakage.
    (4) For each lavatory drain system that has a service panel 
drain valve installed, Kaiser Electroprecision part number series 
0218-0032 or Shaw Aero part number/serial number as listed in Table 
1 of this AD: Within 1,000 flight hours after the effective date of 
this AD, and thereafter at intervals not to exceed 1,000 flight 
hours, accomplish the requirements of paragraphs (a)(4)(i) and 
(a)(4)(ii) of this AD:

   Table 1.--Shaw Aero Valves Approved for 1,000 Flight Hour Leak Test  
                                Interval                                
------------------------------------------------------------------------
                                            Serial Nos. of part number  
    Shaw waste drain valve part no.       valve approved for 1,000-hour 
                                                leak test interval      
------------------------------------------------------------------------
331 Series, 332 Series.................  All.                           
10101000B-A............................  None.                          
10101000B-A-1..........................  0207-0212, 0219, 0226 and      
                                          higher.                       
10101000BA2............................  0130 and higher.               
10101000C-A-1..........................  0277 and higher.               
10101000C-J............................  None.                          
10101000C-J-2..........................  None.                          
10101000CN OR C-N......................  3649 and higher.               
Certain 10101000B valves...............  Any of these ``B'' series      
                                          valves that incorporate the   
                                          improvements of Shaw Service  
                                          Bulletin 10101000B-38-1, dated
                                          October 7, 1994, and are      
                                          marked ``SBB38-1-58''.        
Certain 10101000C valves...............  Any of these ``C'' series      
                                          valves that incorporate the   
                                          improvements of Shaw Service  
                                          Bulletin 10101000C-38-2 dated 
                                          October 7, 1994, and are      
                                          marked ``SBC38-2-58''.        
------------------------------------------------------------------------

    Note 2: Table 1 is a comprehensive list of all approved Shaw 
Valves, including those valves approved by Parts Manufacturer 
Approval (PMA) or Supplemental Type Certificate (STC) for 
installation on Boeing Model 737 series airplanes.

    (i) Conduct a leak test of the toilet tank dump valve and 
service panel drain valve. The toilet tank dump valve leak test must 
be performed by filling the toilet tank with a minimum of 10 gallons 
of water/rinsing fluid and testing for leakage after a period of 5 
minutes. Take precautions to avoid overfilling the tank and spilling 
fluid into the airplane. The service panel drain valve leak test 
must be performed with a minimum of 3 PSID applied across the valve 
inner door/closure device.
    (ii) Perform a visual inspection of the outer cap/door and seal 
mating surface for wear or damage that may cause leakage.
    (5) For each lavatory drain system that has a service panel 
drain valve installed, Kaiser Electroprecision part number series 
0218-0026; or Shaw Aero Devices part number series 10101000B or 
10101000C [except as specified in paragraph (a)(4) of this AD]: 
Within 600 flight hours after the effective date of this AD, and 
thereafter at intervals not to exceed 600 flight hours, accomplish 
the requirements of paragraphs (a)(5)(i) and (a)(5)(ii) of this AD:
    (i) Conduct a leak test of the dump valve and the service panel 
drain valve. The leak test of the dump valve must be performed by 
filling the toilet tank with a minimum of 10 gallons of water/
rinsing fluid and testing for leakage after a period of 5 minutes.
    Take precautions to avoid overfilling the tank and spilling 
fluid on the airplane. The service panel drain valve leak test must 
be performed with a minimum 3 PSID applied across the valve inner 
door/closure device.
    (ii) Perform a visual inspection of the outer cap/door and seal 
mating surface for wear or damage that may cause leakage.
    (6) For each lavatory drain system with a lavatory drain system 
valve that incorporates either ``donut'' plug, Kaiser 
Electroprecision part number 4259-20 or 4259-31; Kaiser Roylyn/
Kaiser Electroprecision cap/flange part numbers 2651-194C, 2651-
197C, 2651-216, 2651-219, 2651-235, 2651-256, 2651-258, 2651-259, 
2651-260, 2651-275, 2651-282, 2651-286; or other FAA-approved 
equivalent parts; accomplish the requirements at the specified times 
of paragraphs (a)(6)(i), (a)(6)(ii), and (a)(6)(iii) of this AD. For 
the purposes of this paragraph [(a)(6)], ``equivalent part'' means 
either a ``donut'' plug that mates with the cap/flange having part 
numbers listed in this paragraph, or a cap/flange that mates with 
the ``donut'' plug having part numbers listed in this paragraph, 
such that the cap/flange and ``donut'' plug are used together as an 
assembled valve.
    (i) Within 200 flight hours after the effective date of this AD, 
and thereafter at intervals not to exceed 200 flight hours, conduct 
leak tests of the toilet tank dump valve and the service panel drain 
valve. The leak test of the toilet tank dump valve must be performed 
by filling the toilet tank with a minimum of 10 gallons of water/
rinsing fluid and testing for leakage after a period of 5 minutes. 
Take precautions to avoid overfilling the tank and spilling fluid on 
the airplane. The service panel drain valve leak test must be 
performed with a minimum 3 PSID applied across the valve.
    (ii) Perform a visual inspection of the outer door/cap and seal 
mating surface for wear or damage that may cause leakage. This 
inspection shall be accomplished in conjunction with the leak tests 
of paragraph (a)(6)(i).
    (iii) Within 5,000 flight hours after the effective date of this 
AD, replace the donut valve (part numbers per paragraph (a)(6) of 
this AD) with another type of FAA-approved valve. Following 
installation of the replacement valve, perform the appropriate leak 
tests and seal replacements at the intervals specified for that 
replacement valve, as applicable.
    (7) For each lavatory drain system not addressed in paragraph 
(a)(2), (a)(3), (a)(4), (a)(5), and (a)(6) of this AD: Within 200 
flight hours after the effective date of this AD, and thereafter at 
intervals not to exceed 200 flight hours, accomplish the 
requirements of paragraphs (a)(7)(i) and (a)(7)(ii) of this AD:
    (i) Conduct a leak test of the toilet tank dump valve and the 
service panel drain valve. The toilet tank dump valve leak test must 
be performed by filling the toilet tank with a minimum of 10 gallons 
of water/rinsing fluid and testing for leakage after a period of 5 
minutes. Take precautions to avoid overfilling the tank and spilling 
fluid on the airplane. The service panel drain valve leak test must 
be performed with a minimum 3 PSID applied across the valve inner 
door/closure device.

[[Page 62719]]

    (ii) Perform a visual inspection of the outer cap/door and seal 
mating surface for wear or damage that may cause leakage.
    (8) For flush/fill lines: Within 5,000 flight hours after the 
effective date of this AD, perform the requirements of paragraph 
(a)(8)(i), (a)(8)(ii), or (a)(8)(iii) of this AD, as applicable. 
Thereafter, repeat the requirements at intervals not to exceed 5,000 
flight hours, or 48 months after the last documented seal change, 
whichever occurs later.
    (i) If a lever lock cap is installed on the flush/fill line of 
the subject lavatory, replace the seals on the toilet tank anti-
siphon (check) valve and the flush/fill line cap. Perform a leak 
test of the toilet tank anti-siphon (check) valve with a minimum of 
3 PSID across the valve, in accordance with paragraph (a)(8)(ii)(A) 
of this AD, as applicable.

    Note 3: The leak test procedure described in Boeing Maintenance 
Manual, 38-32-00/501, may be referred to as guidance for this test 
if the toilet tank is filled to the level specified in paragraph 
(a)(8)(ii)(A) of this AD.

    (ii) If a vacuum breaker check valve, Monogram part number 
series 3765-190, or Shaw Aero Devises part number series 301-0009-01 
is installed on the subject lavatory, replace the seals/o-rings in 
the valve. Perform a leak test of the vacuum breaker check valve and 
verify proper operation of the vent line vacuum breaker in 
accordance with paragraphs (a)(8)(ii)(A) and (a)(8)(ii)(B) of this 
AD.
    (A) Leak test the toilet tank anti-siphon valve or the vacuum 
breaker check valve by filling the toilet tank with water/rinsing 
fluid to a level such that the bowl is approximately half full (at 
least 2 inches above the flapper in the bowl.) Apply 3 PSID across 
the valve in the same direction as occurs in flight. The vent line 
vacuum breaker on vacuum breaker check valves must be pinched closed 
or plugged for this leak test. If there is a cap/valve at the flush/
fill line port, the cap/valve must be removed/open during the test. 
Check for leakage at the flush/fill line port for a period of 5 
minutes.
    (B) Verify proper operation of the vent line vacuum breaker by 
filling the tank and testing at the fill line port for back drainage 
after disconnecting the fluid source from the flush/fill line port. 
If back drainage does not occur, replace the vent line vacuum 
breaker or repair the vacuum breaker check valve in accordance with 
the component maintenance manual to obtain proper back drainage. As 
an alternative to the above test technique, verify proper operation 
of the vent line vacuum breaker in accordance with the procedures of 
the applicable component maintenance manual.
    (iii) If a flush/fill ball valve, Kaiser Electroprecision part 
number series 0062-0009 is installed on the flush/fill line of the 
subject lavatory, replace the seals in the flush/fill ball valve and 
the toilet tank anti-siphon valve. Perform a leak test of the toilet 
tank anti-siphon valve with a minimum of 3 PSID across the valve, in 
accordance with paragraph (a)(8)(ii)(A) of this AD.
    (9) As a result of the leak tests and inspections required by 
paragraph (a) of this AD, or if evidence of leakage is found at any 
other time, accomplish the requirements of paragraph (a)(9)(i), 
(a)(9)(ii), or (a)(9)(iii), as applicable.
    (i) If a leak is discovered, prior to further flight, repair the 
leak. Prior to further flight after repair, perform the appropriate 
leak test, as applicable. Additionally, prior to returning the 
airplane to service, clean the surfaces adjacent to where the 
leakage occurred to clear them of any horizontal fluid residue 
streaks; such cleaning must be to the extent that any future 
appearance of a horizontal fluid residue streak will be taken to 
mean that the system is leaking again.

    Note 4: For purposes of this AD, ``leakage'' is defined as any 
visible leakage, if observed during a leak test. At any other time 
(than during a leak test), ``leakage'' is defined as the presence of 
ice in the service panel, or horizontal fluid residue streaks/ice 
trails originating at the service panel. The fluid residue is 
usually, but not necessarily, blue in color.

    (ii) If any worn or damaged seal is found, or if any damaged 
seal mating surface is found, prior to further flight, repair or 
replace it in accordance with the valve manufacturer's maintenance 
manual.
    (iii) In lieu of performing the requirements of paragraph 
(a)(9)(i) or (a)(9)(ii): Prior to further flight, 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, operators may revise the FAA-approved maintenance program 
to include the requirements specified in paragraphs (b)(1) through 
(b)(7) of this AD. However, until the FAA-approved maintenance 
program is so revised, operators must accomplish the requirements of 
paragraph (a) of this AD. The waste drain system valve leak tests 
specified in this AD shall be performed in accordance with the 
following requirements: fluid shall completely cover the upstream 
end of the valve being tested; the direction of the 3 pounds per 
square inch differential pressure (PSID) shall be applied across the 
valve in the same direction as occurs in flight; the other waste 
drain system valves shall be open; and the minimum time to maintain 
the differential pressure shall be 5 minutes. Any revision of the 
seal change intervals or leak test intervals must be approved by the 
Manager, Seattle ACO.
    (1) Replace the valve seals in accordance with the applicable 
schedule specified in paragraphs (b)(1)(i), (b)(1)(ii), or 
(b)(1)(iii) of this AD.
    (i) For each lavatory drain system that has an in-line drain 
valve installed, Kaiser Electroprecision part number series 2651-
278: Replace the seals within 5,000 flight hours after the effective 
date of this AD, or within 48 months of the last documented seal 
change, whichever occurs later. Thereafter, repeat the replacement 
of the seals at intervals not to exceed 48 months.
    (ii) For each lavatory drain system that has a Pneudraulics part 
number series 9527 valve: Replace the seals within 5,000 flight 
hours after the effective date of this AD, or within 18 months of 
the last documented seal change, whichever occurs later. Thereafter, 
repeat the replacement of the seals at intervals not to exceed 18 
months or 6,000 flight hours, whichever occurs later.
    (iii) For each lavatory drain system that has any other type of 
drain valve: Replace the seals within 5,000 flight hours after the 
effective date of this AD, or within 18 months of the last 
documented seal change, whichever occurs later. Thereafter, repeat 
the replacement of the seals at intervals not to exceed 18 months.
    (2) Conduct periodic leak tests of the lavatory drain systems in 
accordance with the applicable schedule specified in paragraphs 
(b)(2)(i), (b)(2)(ii), (b)(2)(iii), (b)(2)(iv), and (b)(2)(v) of 
this AD. Only one of the waste drain system leak test procedures 
(the one that applies to the equipment with the longest leak test 
interval) must be conducted at each service panel location.
    (i) For each lavatory drain system, that has an in-line drain 
valve installed, Kaiser Electroprecision part number series 2651-
278: Within 5,000 flight hours after the effective date of this AD, 
or within 5,000 hours of the last documented leak test, whichever 
occurs later, accomplish the procedures specified in paragraphs 
(b)(2)(i)(A) and (b)(2)(i)(B) of this AD. Thereafter repeat the 
procedures at intervals not to exceed 24 months or 5,000 flight 
hours, whichever occurs later.
    (A) Conduct a leak test of the dump valve (in-tank valve that is 
spring loaded closed and operable by a T-handle at the service 
panel) and the in-line drain valve. The leak test of the toilet tank 
dump valve must be performed by filling the toilet tank with a 
minimum of 10 gallons of water/rinsing fluid and testing for leakage 
after a period of 5 minutes. Take precautions to avoid overfilling 
the tank and spilling fluid on the airplane. The in-line drain valve 
leak test must be performed with a minimum of 3 PSID applied across 
the valve.
    (B) If a service panel valve or cap is installed, perform a 
visual inspection of the service panel drain valve outer cap/door 
seal and the inner seal (if the valve has an inner door with a 
second positive seal), and the seal mating surfaces, for wear or 
damage that may allow leakage.
    (ii) For each lavatory drain system that has a service panel 
drain valve installed, Pneudraulics part number series 9527: Within 
4,000 flight hours after the effective date of this AD, or within 
4,000 flight hours of the last documented leak test, whichever 
occurs later, accomplish the requirements of paragraph (b)(2)(ii)(A) 
and (b)(2)(ii)(B) of this AD. Thereafter, repeat the requirements at 
intervals not to exceed 4,000 flight hours.
    (A) Conduct leak tests of the toilet tank dump valve and service 
panel drain valve. The toilet tank dump valve leak test must be 
performed by filling the toilet tank with a minimum of 10 gallons of 
water/rinsing fluid and testing for leakage after a period of 5 
minutes. Take precautions to avoid overfilling the tank and spilling 
fluid on the airplane. The service panel drain valve leak test must 
be performed with a minimum of 3 PSID applied across the valve inner 
door/closure device.
    (B) Perform a visual inspection of the outer cap/door and seal 
mating surface for wear or damage that may cause leakage.

[[Page 62720]]

    (iii) For each lavatory drain system that has a service panel 
drain valve installed, Kaiser Electroprecision part number series 
0218-0032, or Kaiser Electroprecision part number series 0218-0026, 
or Shaw Aero Devices part number series 10101000B, 10101000C, 331-
series, 332-series: Within 1,000 flight hours after the effective 
date of this AD, or within 1,000 flight hours of the last documented 
leak test, whichever occurs later, accomplish the requirements of 
paragraphs (b)(2)(iii)(A) and (b)(2)(iii)(B) of this AD. Thereafter, 
repeat the requirements at intervals not to exceed 1,000 flight 
hours.
    (A) Conduct leak tests of the toilet tank dump valve and service 
panel drain valve. The toilet tank dump valve leak test must be 
performed by filling the toilet tank with a minimum of 10 gallons of 
water/rinsing fluid and testing for leakage after a period of 5 
minutes. Take precautions to avoid overfilling the tank and spilling 
fluid on the airplane. The service panel drain valve leak test must 
be performed with a minimum of 3 PSID applied across the valve inner 
door/closure device.
    (B) Perform a visual inspection of the outer cap/door and seal 
mating surface for wear or damage that may cause leakage.
    (iv) For each lavatory drain system with a lavatory drain system 
valve that incorporates either ``donut'' plugs Kaiser 
Electroprecision part number 4259-20 or 4259-31; Kaiser Roylyn/
Kaiser Electroprecision cap/flange part number 2651-194C, 2651-197C, 
2651-216, 2651-219, 2651-235, 2651-256, 2651-258, 2651-259, 2651-
260, 2651-275, 2651-282, 2651-286; or other FAA-approved equivalent 
part; accomplish the requirements at the times specified in 
paragraphs (b)(2)(iv)(A), (b)(2)(iv)(B), and (b)(2)(iv)(C) of this 
AD. For the purposes of this paragraph [(b)(2)(iv)], ``FAA-approved 
equivalent part'' means either a ``donut'' plug that mates with the 
cap/flange having part numbers listed in this paragraph, or a cap/
flange that mates with the ``donut'' plug having part numbers listed 
in this paragraph, such that the cap/flange and ``donut'' plug are 
used together as an assembled valve.
    (A) Within 200 flight hours after the effective date of this AD, 
or within 200 flight hours after the last documented leak test, 
whichever occurs later, conduct leak tests of the dump valve and the 
service panel drain valve. Thereafter, repeat the tests at intervals 
not to exceed 200 flight hours. The dump valve leak test must be 
performed by filling the toilet tank with a minimum of 10 gallons of 
water/rinsing fluid and testing for leakage after a period of 5 
minutes. Take precautions to avoid overfilling the tank and spilling 
fluid on the airplane. The service panel drain valve leak test must 
be performed with a minimum 3 PSID applied across the valve.
    (B) Perform a visual inspection of the outer door/cap and seal 
mating surface for wear or damage that may cause leakage. Perform 
this inspection in conjunction with the leak tests specified in 
paragraph (b)(2)(iv)(A).
    (C) Within 5,000 flight hours after the effective date of this 
AD, replace the donut valve with another type of FAA-approved valve. 
Following replacement of the valve, perform the subsequent leak 
tests and seal replacements at the intervals specified for the new 
valve.
    (v) For each lavatory drain system that incorporates any other 
type of approved valves: Within 400 flight hours after the effective 
date of this AD, or within 400 flight hours of the last documented 
leak test, whichever occurs later, accomplish the requirements of 
paragraph (b)(2)(v)(A) and (b)(2)(v)(B) of this AD. Thereafter, 
repeat the requirements at intervals not to exceed 400 flight hours.
    (A) Conduct leak tests of the toilet tank dump valve and the 
service panel drain valve. The toilet tank dump valve leak test must 
be performed by filling the toilet tank with a minimum of 10 gallons 
of water/rinsing fluid and testing for leakage after a period of 5 
minutes. Take precautions to avoid overfilling the tank and spilling 
fluid on the airplane. The service panel drain valve leak test must 
be performed with a minimum 3 PSID applied across the valve. If the 
service panel drain valve has an inner door with a second positive 
seal, only the inner door must be tested.
    (B) Perform a visual inspection of the outer cap/door and seal 
mating surface for wear or damage that may cause leakage.
    (3) For flush/fill lines: Within 5,000 flight hours after the 
effective date of this AD, perform the requirements of paragraph 
(b)(3)(i), (b)(3)(ii), or (b)(3)(iii), as applicable. Thereafter, 
repeat the requirements at intervals not to exceed 5,000 flight 
hours, or 48 months after the last documented seal change, whichever 
occurs later.
    (i) If a lever lock cap is installed on the flush/fill line of 
the subject lavatory, replace the seals on the toilet tank anti-
siphon (check) valve and the flush/fill line cap. Perform a leak 
test of the toilet tank anti-siphon (check) valve with a minimum of 
3 PSID across the valve as specified in paragraph (b)(3)(ii)(A) of 
this AD.
    (ii) If a vacuum breaker check valve, Monogram part number 
series 3765-190 or Shaw Aero Devises part number series 301-0009-01, 
is installed on the subject lavatory; replace the seals/o-rings in 
the valve. Prior to further flight, leak test the vacuum breaker 
check valve, and test for proper operation of the vent line vacuum 
breaker as specified in paragraphs (b)(3)(ii)(A) and (b)(3)(ii)(B) 
of this AD.
    (A) Leak test the toilet tank anti-siphon valve or the vacuum 
breaker check valve by filling the toilet tank with water/rinsing 
fluid to a level such that the bowl is approximately half full (at 
least 2 inches above the flapper in the bowl). Pressurize the 
airplane to 3 PSID. The vent line vacuum breaker on vacuum breaker 
check valves must be pinched closed or plugged for this leak test. 
If there is a cap/valve at the flush/fill line port, the cap/valve 
must be removed/opened during the test. Test for leakage at the 
flush/fill line port for a period of 5 minutes.

    Note 5: The leak test procedure in the appropriate section of 
Boeing Maintenance Manual 38-32-00 may be used as guidance for this 
test if the toilet tank is filled approximately half full (at least 
2 inches above the flapper in the bowl).

    (B) Verify proper operation of the vent line vacuum breaker by 
filling the tank and testing at the fill line port for back drainage 
after disconnecting the fluid source from the flush/fill line port. 
If back drainage does not occur, replace the vent line vacuum 
breaker or repair the vacuum breaker check valve in accordance with 
the component maintenance manual as required to obtain proper back 
drainage.
    (iii) If a flush/fill ball valve, Kaiser Electroprecision part 
number series 0062-009 installed on the flush/fill line of the 
subject lavatory, replace the seals in the flush/fill ball valve and 
the toilet tank anti-siphon valve. Perform a leak test of the toilet 
tank anti-siphon valve in accordance with paragraph (b)(3)(ii))(A) 
of this AD.
    (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 ``horizontal 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 placard 
inoperative.
    (6) Provide training programs for maintenance and servicing 
personnel that include information on ``Blue Ice Awareness'' and the 
hazards of ``blue ice''.
    (7) If a leak is discovered during a leak test required by 
paragraph (b) of this AD; or if evidence of leakage is found at any 
other time; or if repair/replacement of a valve (or valve parts) is 
required as a result of a visual inspection required in accordance 
with this AD; prior to further flight, accomplish the requirements 
of paragraph (b)(7)(i), (b)(7)(ii), or (b)(7)(iii), as applicable.

    Note 6: For purposes of this AD, ``leakage'' is defined as any 
visible leakage, if observed during a leak test. At any other time 
(than during a leak test), ``leakage'' is defined as the presence of 
ice in the service panel, or horizontal fluid residue streaks/ice 
trails originating at the service panel. The fluid residue is 
usually, but not necessarily, blue in color.

    (i) Repair the leak and, prior to further flight after repair, 
perform a leak test. Additionally, prior to returning the airplane 
to service, clean the surfaces adjacent to where the leakage 
occurred to clear them of any horizontal fluid residue streaks; such 
cleaning must be to the extent that any future appearance of a 
horizontal fluid residue streak will be taken to mean that the 
system is leaking again.
    (ii) Repair or replace the valve or valve parts.
    (iii) In lieu of either paragraph (b)(7)(i) or (b)(7)(ii), drain 
the affected lavatory system and placard the lavatory inoperative 
until repairs can be accomplished.
    (c) For operators who elect to comply with paragraph (b) of this 
AD: Any revision to (i.e., extension of) the leak test 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;

[[Page 62721]]

    (2) A statement verifying that all known cases/indications 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 test interval;
    (6) Whether or not seals have been replaced between the seal 
replacement intervals required by this AD;
    (7) Whether or not a service panel drain valve is installed 
downstream of an in-line drain valve, Kaiser Electroprecision part 
number series 2651-278: Data on a service panel valve installed 
downstream of an in-line drain valve will not be considered as an 
indicator of the reliability of the service panel drain valve 
because the in-line valve prevents potential leakage from reaching 
the service panel drain valve.
    (8) Whether or not leakage has been detected between leak test 
intervals required by this AD, and the reason for leakage (i.e., 
worn seals, foreign materials on sealing surface, scratched or 
damaged sealing surface on valve, etc.);
    (9) Whether or not any cleaning, repairs, or seal changes were 
performed on the valve prior to conducting the leak test. [If such 
activities have been accomplished prior to conducting the periodic 
leak test, that leak test 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 test will not cause that leak 
test to be recorded as a failure. Debris removal of major blockages 
done as part of normal maintenance for previous flights is also 
allowable and will not cause a leak test to be recorded as a 
failure. Minor debris removal that is not commonly removed during 
the normal ground maintenance test should not be removed prior to 
the leak test.]

    Note 7: Requests for approval of revised leak test intervals may 
be submitted in any format, provided the data give the same level of 
assurance specified in paragraph (c) above. Results of an 
Environmental Quality Analysis (EQA) examination and leak test on a 
randomly selected high-flight-hour valve, with seals that have not 
been replaced during a period of use at least as long as the desired 
interval, may be considered a valuable supplement to the service 
history data, reducing the amount of service data that would 
otherwise be required.
    Note 8: For the purposes of expediting resolution of requests 
for revisions to the leak test intervals, the FAA suggests that the 
requester 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 test interval.
    Note 9: In cases where changes are made to a valve design 
approved for an extended leak test interval such that a new valve 
dash number or part number is established for the valve, the FAA may 
not require extensive service history data to approve the new valve 
to the same leak test interval as the previous valve design. 
Similarity of design, the nature of the design changes, the nature 
and amount of testing, and like factors will be considered by the 
FAA to determine the appropriate data requirements and leak test 
interval for a new or revised valve based upon an existing design.

    (d) For all airplanes: Unless already accomplished, within 5,000 
flight hours after the effective date of this AD, perform the 
actions specified in paragraph (d)(1), (d)(2), or (d)(3) of this AD:
    (1) Install an FAA-approved lever/lock cap on the flush/fill 
lines for all lavatories. Or
    (2) Install a vacuum break, Monogram part number series 3765-
190, or Shaw Aero Devises part number series 301-0009-01, in the 
flush/fill lines for all lavatories. Or
    (3) Install a flush/fill ball valve Kaiser Electroprecision part 
number series 0062-0009 on the flush/fill lines for all lavatories.
    (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 tests 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 test has been performed 
once, each subsequent leak test 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 test 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 test.
    (2) For airplanes that have not been previously maintained in 
accordance with this AD, the first leak test 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) Alternative method(s) of compliance with this AD:
    (1) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle 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.
    (2) Alternative methods of compliance previously approved for AD 
89-11-03, which permit a 4,500-flight hour interval between leak 
tests of the forward waste drain system for those operators 
installing the modifications specified in Boeing Service Bulletin 
737-38-1026, Revision 2, dated May 4, 1995, or Boeing Service 
Bulletin 737-38-1031, Revision 1, dated April 20, 1995, and later 
FAA-approved revisions, are considered acceptable alternative 
methods of compliance with the requirements of only paragraph (a)(2) 
of this AD. For those operators, the other requirements of this AD 
are still required to be accomplished. All other alternative methods 
of compliance approved for AD 89-11-03 are terminated and are no 
longer in effect.

    Note 10: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.
    Note 11: For any valve that is not eligible for the extended 
leak test intervals of this AD: To be eligible for the extended leak 
test intervals specified in paragraph (b) of this AD, 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. The request should include an 
analysis of known failure modes for the valve, if it is an existing 
design, and known failure modes of similar valves, with an 
explanation of how design features will preclude these failure 
modes, results of qualification tests, and approximately 25,000 
flight hours or 25,000 flight cycles of service history data which 
include a winter season, collected in accordance with the 
requirements of paragraph (c) above, or a similar program. 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. However, meeting the Boeing specification is 
not a prerequisite for approval of alternative valve designs.

    (g) Special flight permits may be issued in accordance with 
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
21.197 and 21.199) to operate the airplane to a location where the 
requirements of this AD can be accomplished.

    Issued in Renton, Washington, on November 18, 1997.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-30855 Filed 11-24-97; 8:45 am]
BILLING CODE 4910-13-U