Airworthiness Directives; Boeing Model 727 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 90-NM-265-AD]

Airworthiness Directives; Boeing Model 727 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of

comment period.

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SUMMARY: This document revises an earlier proposed airworthiness

directive (AD), applicable to Boeing Model 727 series airplanes, which

would have superseded an existing AD that currently requires periodic

leak checks of the forward lavatory drain system and provides for the

installation of a new drain valve as terminating action. The proposed

action would have deleted the existing provision for terminating

action, required repetitive leak checks of both the forward and aft

lavatory drain systems, and added an optional procedure for complying

with the rule. That proposal was prompted by reports of engine and

airframe damage, engine separation, and damage to property on the

ground, caused by ``blue ice'' that had formed from leaking forward

lavatory drain systems and subsequently had dislodged from the

airplane. This action revises the proposal by changing the optional

procedure, adding a requirement for installation of a cap on the flush/

fill line, and requiring periodic leak checks of the flush/fill system.

DATES: Comments must be received by May 2, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 90-NM-265-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056. Comments may be inspected at this

location between 9 a.m. and 3 p.m., Monday through Friday, except

Federal holidays.

FOR FURTHER INFORMATION CONTACT: Don Eiford, Aerospace Engineer,

Seattle Aircraft Certification Office, Systems and Equipment Branch,

ANM-130S, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056; telephone (206) 227-2788; fax (206) 227-

1811.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed rule by submitting such written data, views, or arguments as

they may desire. Communications shall identify the Rules Docket number

and be submitted in triplicate to the address specified above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals contained in this notice may be changed in

light of the comments received.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the proposed rule. All

comments submitted will be available, both before and after the closing

date for comments, in the Rules Docket for examination by interested

persons. A report summarizing each FAA-public contact concerned with

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket Number 90-NM-265-AD.'' The postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules

Docket No. 90-NM-265-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations to

add an airworthiness directive (AD), applicable to Boeing Model 727

series airplanes, was published as a supplemental notice of proposed

rulemaking (NPRM) in the Federal Register on March 22, 1993 (58 FR

15305). That supplemental NPRM proposed to revise a previously issued

NPRM that proposed the supersedure of AD 86-05-07, Amendment 39-5250

(51 FR 7767, March 6, 1986). AD 86-05-07 currently requires periodic

leak checks of the forward lavatory drain system and provides for the

installation of a new drain valve as terminating action. The previously

issued supplemental NPRM proposed to:

1. Delete the existing provision for terminating action;

2. Require repetitive leak checks of both the forward and the aft

lavatory drain systems, and

3. Provide an optional procedure for complying with the rule, which

would entail revising the FAA-approved maintenance program to

incorporate a schedule and procedure to conduct leak checks of the

lavatory drain systems.

The proposed action was prompted by reports of engine and airframe

damage, and one report of engine separation on a Boeing Model 727

series airplane that occurred subsequent to the issuance of AD 86-05-

07. These incidents were caused by ``blue ice'' that had formed from

leaking forward lavatory drain systems and subsequently had broken

loose from the airplane and struck the fuselage or had been ingested

into the engine. The proposed action also was prompted by reports of

leakage from lavatory drain valves that have a configuration similar to

that specified in AD 86-05-07 as terminating action. Such leakage can

result in the formation of blue ice, which can dislodge from the

airplane and result in engine damage or separation, airframe damage,

and/or a hazard to persons or property on the ground.

Since the issuance of that supplemental NPRM, the FAA has

determined that certain additional changes to the proposed rule are

necessary.

General Changes to the Proposal: ``The Comprehensive Approach''

The FAA has reviewed its position on the option that was provided

in the previous supplemental NPRM, which would have permitted operators

to revise the FAA-approved maintenance program to include procedures to

address the problems associated with blue ice. The FAA now considers

that an even more comprehensive approach should be taken to address the

subject unsafe condition via the FAA-approved maintenance program. This

approach should be based upon regular maintenance, training of

personnel, use of hardware with proven reliability, and fixed, but less

frequent, leak checks incorporated into the FAA-approved maintenance

program. Paragraph (b) of this supplemental NPRM has been revised to

specify the requirements for the maintenance program revision that the

FAA has determined are necessary in order to implement this

``comprehensive approach.'' (A more detailed discussion of these

proposed requirements is presented later in this preamble.)

In lieu of the revising the maintenance program, however, this

supplemental NPRM will continue to provide operators with the option of

accomplishing the specific leak check procedures on the drain systems.

General Changes to the Notice: Extension of Leak Check Intervals

The proposed AD would extend the previously-proposed leak check

intervals for certain specific valves, provided that a suitable program

of maintenance and training of personnel is also implemented. These

intervals have been extended based upon data gathered to date regarding

the service history of the valve types.

The proposed AD would also require that any revisions to (i.e.,

extension of) the mandated leak check intervals must be approved by the

FAA, specifically, by the Manager of the Seattle Aircraft Certification

Office (ACO). Requests for such revisions must be accompanied by

certain data when submitted to the ACO [through the appropriate FAA

Principal Maintenance Inspector (PMI)] for approval. In this

supplemental NPRM, the FAA proposes a ``data collection format'' for

these requests. Data submitted in accordance with the proposed format,

if favorable to an increase of leak check intervals, will allow the FAA

to justify increasing the leak check intervals with assurance that the

valves involved have the required reliability. The data provided will

also be important in assisting the FAA in making future determinations

of appropriate leak check intervals for new valves that have shown

promising, but not conclusive, service data.

General Changes to the Notice: Flush/Fill Line Problems

Certain comments submitted to the Rules Docket in response to the

previously issued supplemental NPRM included reference to three

incidents of foreign object damage from the forward toilet drain valve

and flush/fill line on certain airplanes.

The FAA also has received a report of a dent on the right

horizontal stabilizer leading edge on a Boeing Model 737 series

airplane that was caused by blue ice that had formed from leakage

through a flush/fill line. In this case, the flush/fill cap was missing

from the line at the forward service panel. The flush/fill line on the

Model 737 is similar in design to that on the Model 727; therefore, the

potential exists for the same type of incident occurring on the Model

727.

Further, in their comments to the Rules Docket, numerous operators

stated that leakage from the flush/fill line is a significant source of

the type of blue ice problems addressed by this AD action.

While there are not many documented cases of blue ice coming from

the flush/fill line causing damage to engines, such blue ice is still a

hazard to persons and property on the ground and, therefore,

constitutes an unsafe condition. In light of this, the FAA has

reconsidered its previous statement that flush/fill line leakage would

be ``addressed by a separate rulemaking action,'' and is proposing

requirements in this supplemental NPRM to install a cap on the flush/

fill line and to perform periodic leak checks of the flush/fill line.

The FAA has reviewed and approved Boeing Service Bulletin 727-38-

0021, dated July 30, 1992, that provides instructions for modifying the

forward, aft, and executive lavatory drain systems by installing a cap

on the flush/fill lines. This modification will prevent blue fluid

leakage and subsequent ice accumulation in the executive and aft

lavatory service panels, and in the forward lavatory waste system.

This supplemental NPRM proposes to require the installation of the

flush/fill line cap in accordance with the Boeing service bulletin

within 5,000 flight hours.

General Changes to the Notice: New Owners' Schedules

A new paragraph (e) has been added to this supplemental NPRM to

require that, before an operator places an airplane subject to the AD

into service, the operator must establish a schedule for accomplishment

of the leak checks. This provision is intended to ensure that

transferred airplanes are inspected in accordance with the AD on the

same basis as if there were continuity in ownership, and that

scheduling of the leak checks for each airplane is not delayed or

postponed due to a transfer of ownership. Airplanes that have

previously been subject to the AD would have to be checked in

accordance with either the previous operator's or the new operator's

schedule, whichever would result in the earlier accomplishment date for

that leak check. Other airplanes would have to be inspected before an

operator could begin operating them or in accordance with a schedule

approved by the FAA PMI, but within a period not exceeding 200 flight

hours.

Since the changes described above expand the scope of the

previously proposed rule, the FAA has determined that it is necessary

to reopen the comment period to provide additional opportunity for

public comment.

Due consideration has been given to the following comments that

were submitted in response to the previously issued supplemental NPRM:

Hardware Nomenclature

Several commenters suggest that the proposal be revised to include

terms that would more specifically describe the valves that are

affected by the rule. Certain commenters suggest that generic

references to ``ball valves'' in proposed paragraph (a) should be

replaced with references to ``Boeing Specification S417T105,'' which

more clearly defines the configuration of the specific ball valve that

must be inspected. These commenters also suggest that references in

proposed paragraph (a) to the ``Shaw Aero Devices, Inc., drain valve

that incorporates an integral inner door with a second positive seal,''

be replaced with references to the ``service panel valve per Boeing

Specification 10-62213.'' On the other hand, one commenter requests

that the terms used in the proposal to describe the Shaw Aero valve be

retained, so that earlier models of the Shaw Aero valve (not configured

per Boeing Specification 10-62213) would ``benefit'' from the proposed

extended leak check intervals. Another commenter states that the

earlier models of those Shaw Aero valves were upgraded because they

leaked and, therefore, those valves should not be included with the

valves specified by ``Boeing Specification 10-62213'' for purposes of

receiving the extended leak check periods.

The FAA has reviewed the data submitted with these comments and

finds that certain of the requested changes are appropriate. The FAA

concurs with the request to specifically identify those valves approved

for the longer leak check intervals. The FAA has reviewed the

referenced Boeing specifications, as well as the part numbers of valves

that have been determined to meet these specifications and that have

service history data approved by the FAA. The FAA has determined that

the qualifying valves are as follows:

1. Valves meeting Boeing Specification S417T105: Kaiser

Electroprecision valves having part number 2651-329-5 (or higher ``dash

number'');

2. Valves meeting Boeing Specification 10-62213: Kaiser

Electroprecision valves having part number 0218-0032-8 (or higher

``dash number''); and Shaw Aero Devices valves having part number

10101000C-N (or higher ``dash numbers'').

Therefore, this supplemental NPRM has been revised to refer to

certain of the affected valves as those having the part numbers

indicated above. Valves having Kaiser Electroprecision part number

2651-329-5 (or higher ``dash number'') would be required to be leak

checked at intervals of either 1,500 flight hours [per proposed

paragraph (a)] or 5,000 flight hours [per proposed paragraph (b)].

Valves having Kaiser Electroprecision part number 0218-0032-8 (or

higher ``dash number'') or Shaw Aero Devices part number 10101000C-N

(or higher ``dash numbers'') would be required to be leak checked at

intervals of 1,000 flight hours. To ensure that any valves developed at

a later date are also reviewed first by the FAA for adequate service

history, new paragraph (f) of the proposed rule makes a provision for

the service history data of such additional valves to be approved by

means of an alternative method of compliance with the rule.

Ball Valves, General

Several commenters suggest that, because of the history of the

general reliability of ball valves, the proposed rule should be revised

to permit installation of a ball valve in a drain system as terminating

action for the leak checks of that particular drain system. Other

commenters request that, based on this history of reliability, the

proposed 1,500-flight hour leak checks intervals for drain systems

incorporating ball valves, as proposed in paragraph (a)(1), be extended

to 4,000 or 6,000 flight hours.

The FAA does not concur. While a ball valve may be reliable if

properly maintained, it may still leak eventually due to seal wear or

the entrapment of foreign material on the sealing surfaces. Damage to

the sealing surfaces in a ball valve due to foreign materials, while

uncommon, may also cause leakage at any time. If there are no

maintenance actions aimed at detecting such leakage, the leakage could

continue until the next leak check. An extremely long interval between

leak checks, as suggested by the commenters, would allow leakage to go

undetected for a long time and, thus, create conditions favorable for

the eventual formation of blue ice. The FAA has determined that, by

limiting the leak check interval to 1,500 flight hours, the risk of

long term leakage is reduced.

Ball Valve Leak Checks, Plus Maintenance and Training Programs

Several commenters request that the proposed leak check intervals

for drain systems incorporating a ball valve be extended to 4,000 or

6,000 flight hours, if those leak checks are coupled with a specific

maintenance program as well as a program to train personnel to perform

certain actions. Some of these commenters consider that incorporation

of the 1,500-flight hour leak checks into the operators' FAA-approved

maintenance program, as proposed in paragraph (b) of the previous NPRM,

does not provide sufficient motivation for operators to incorporate

ball valves into the fleet (even though the ball valves are more

reliable than other types).

The FAA concurs with these commenters' request. The FAA has

determined that installation of a design package that includes a ball

valve installed in accordance with Boeing Service Bulletin 727-38-0021,

dated July 30, 1992, combined with certain maintenance actions and

trained personnel (discussed in detail later) will provide adequate

assurance that long term leakage will not occur. Therefore, the FAA has

revised paragraph (b) of the supplemental NPRM to provide for leak

check intervals up to 5,000 flight hours for applicable ball valve

installations that are coupled with maintenance procedures and training

of personnel. This change is specifically intended to encourage

operators to use valve designs having proven reliability; the

incorporation of sufficient maintenance practices and trained personnel

will ensure that the inherent reliability of the design is not

degraded.

Shaw Aero Valves

One commenter requests that the leak check intervals for drain

systems with Shaw Aero valves that incorporate the inner door with

second positive seal be increased from 1,000 flight hours, as proposed

in paragraph (a)(2), to 1,500 or 4,000 flight hours. This commenter

considers that this request is justified based on the lack of adverse

service history on the subject valves.

On the other hand, another commenter objects to the proposed 1,000-

flight hour leak check interval for these valves, and suggests that it

should be shortened. This commenter states that there are certain

considerations that are critical in establishing leak check intervals

based on component failure rates derived from evaluations of in-service

history. Such considerations are:

1. If the ball valve is installed internally so that service

personnel cannot damage it;

2. If the seals are composed of the correct material, and are not

directly in the effluent path so that they cannot be damaged by items

within the effluent that can normally cause seal damage;

3. If, because of the location of the ball valve, it is impractical

to perform a seal replacement;

4. If the valve is leak checked on board the airplane without a

seal change prior to the check;

This commenter states that, when these items are taken into

consideration, service data gathered on this ball valve are

``unambiguous,'' because if the valve passes a leak check, it means

that the valve did not leak before the check was conducted. However,

the subject Shaw Aero valve is located in the service panel and is

accessible to maintenance personnel; moreover, it is common practice

for those personnel to change the seals in the panel valve prior to

leak check intervals. Therefore, the leak check service data that have

been presented relative to this Shaw Aero valve are ``questionable,''

due to the lack of reporting and the fact that seals can be changed out

during servicing and prior to the leak checks.

The FAA does not concur with either commenter's request. The FAA

has reviewed the design improvements and service history data of the

Shaw Aero valves having part number 10101000C-N (or higher dash number)

and has determined that a leak check interval of 1,000 flight hours is

justifiable, based upon the best available data to date. The FAA does

agree with the latter commenter to the extent that justification for

any further extension of this leak check interval beyond 1,000 flight

hours must be based on unambiguous data.

Kaiser Expander Valves

Several commenters submitted service history data on the Kaiser

Expander valve, part number 0218-0032-8, and request that the proposed

rule provide for a leak check interval of 4,000 or 4,500 flight hours

for this valve. As currently written, the proposed rule would place the

Kaiser Expander valve in the category of valves requiring leak checks

every 200 flight hours. These commenters state that the Kaiser Expander

valve has the same positive bore sealing inner flap as the Shaw Aero

valve, and has a service history to prove it is as safe, rugged, and

reliable as the Shaw Aero valve. Some of these commenters consider this

Kaiser valve to be the ``best that is currently available,'' and note

that it had been approved previously as terminating action for AD 86-

05-07.

The FAA concurs that the leak check interval for the Kaiser

Expander valve, part number 0218-0032-8 (or higher dash number), may be

increased from the proposed 200 flight hours. The FAA has reviewed the

service history data for the Kaiser Expander valve and finds that it is

sufficient to justify a 1,000-flight hour leak check interval proposed

in paragraphs (a)(2) and (b)(2)(ii) of this supplemental NPRM.

Other Brands of Valves

Other commenters suggest that the proposal be revised to increase

the leak test intervals to 400 flight hours for the ``other valves''

referred to in proposed paragraph (a)(3) of the previous supplemental

NPRM; and to allow that interval to be increased up to 5,000 flight

hours (an average ``C'' check). These commenters consider that a 200-

flight hour interval is too frequent and would create an undue economic

burden on affected operators.

For many of the same reasons previously discussed, the FAA does not

concur. The FAA does not consider that valves without demonstrated high

reliability should be used without frequent leak checking. Frequent

leak checking provides assurance that the valves will be returned to a

non-leaking condition. The FAA has recognized that some valves in the

``other'' category (such as the earlier Shaw Aero valve models) do have

better service history than others regarding failure and leakage;

therefore, as described previously, the FAA has singled out these

valves and has extended their leak check interval. However, for valves

that are known to be more likely to leak, specifically the ``donut''

and ``taco'' valves, a 200-flight hour leak check interval is

essential.

Certain commenters request that the proposed rule be revised to

grant other brand name valves extended leak check intervals. However,

these commenters did not furnish sufficient service history or leak

check data to substantiate their requests. The FAA cannot determine if

extensions of leak check intervals are warranted without being able to

review significant service history data.

Operators With No Record of Leakage

One commenter suggests that the proposed rule include a provision

for an extended leak check interval for operators that have had no

record of waste water leakage, regardless of what hardware

configuration is used. The commenter considers that the proposal

penalizes operators who have had an excellent service history due to

proper maintenance and servicing. While the installation of additional

hardware will improve the waste system and reduce the likelihood of

leaking, it should be used as an incentive for those operators that

have had a history of leaking waste systems and blue ice foreign object

damage.

The FAA does not agree that an extended interval is warranted for

the reasons suggested by the commenter. Blue ice frequently is not

traceable to the particular airplane, operator, and waste system that

produced it. Incidents of leakage usually are not reported; only the

relatively serious leakage incidents become known to the FAA. Previous

attempts to rely solely upon increased maintenance while using lower

reliability hardware have not proven to be successful. Therefore, a

system to prevent incidents of blue ice in the fleet must be based upon

assurance. The FAA considers that such assurance is provided by

frequent leak checks to ensure that the drain systems do not leak; more

reliable valves may be subject to less frequent leak checks, while less

reliable valves must be subject to more frequent leak checks. As

discussed previously, the FAA considers that maintenance and training

are also important factors in determining appropriate leak check

intervals, and has provided in this supplemental NPRM an option for

either increased leak test intervals, or obtaining approval for less

frequent intervals when hardware is demonstrated to be reliable.

Requests for No Leak Tests for Some Valves

One commenter requests that, in cases where a ball valve is

installed with a service panel valve that has no inner flapper, the

proposed rule not require a leak check to be done on the service panel

valve. The commenter also requests that the proposed rule be revised to

require that, when a service panel valve with an inner door having a

second positive seal is installed with a ball valve, only the inner

seal be tested, and the outer cap seal be visually inspected and

replaced as necessary. The commenter notes that the proposed rule would

call for a pressure differential to be applied across both the ball

valve and the service panel cap valve. However, on many ball valve

installations, the service panel cap has no inner flapper. Applying a

pressure differential across this cap would require spilling a

substantial quantity of fluid on the ramp in order to service the

system after completion of the leak check. The commenter recommends

that the service panel cap valve only be leak checked if it

incorporates a dual seal design, and that the outer cap be visually

inspected for wear or damage, and replaced only as necessary or at

predetermined intervals.

The FAA does not agree with the commenter's request to delete the

leak check requirement for service panel valves that have no inner

flapper. This would be disadvantageous to operators who had a superior

hardware configuration (the dual seal), since it would require that

they perform a test that is not required of installations with only a

single cap. However, the FAA does agree with the suggestion to require

a leak check of only the inner flapper for service panel valves with a

dual seal design, and the performance of visual inspections/seal

changes of only the outer cap. This will ensure that one seal

downstream of the ball valve is returned to a ``no-leak'' condition.

This supplemental NPRM has been revised accordingly.

Development of New Equipment

Several commenters request that the proposed rule provide for a

method to encourage the development of new, more reliable equipment,

and extend the leak check intervals for that equipment.

The FAA agrees that the industry should be encouraged to develop

improved hardware that will better address the unsafe condition

presented by problems associated with blue ice. As one method to

achieve this goal, and to provide assurance of a high degree of

reliability of the hardware involved, the FAA has proposed in paragraph

(c) of this supplemental NPRM, a method of data collection relative to

the reliability of valves. This approach is not intended to supersede

existing methods for equipment qualification and certification.

However, this method of data collection is intended to ensure the

collection of unambiguous data, which will provide the FAA with

adequate resources and information to determine appropriate leak check

intervals for new and existing designs. The FAA intends to use the data

that are eventually collected to determine if extensions to the

currently proposed leak check intervals are justified, specifically for

those operators who choose to incorporate certain maintenance and

training requirements into their FAA maintenance programs in accordance

with paragraph (b) of this supplemental NPRM. The FAA specifically

requests additional suggestions as to methods that will further ensure

the validity of the data gathered.

Implementation of a New Maintenance and Training Program

Numerous commenters request that the proposed rule be revised to

provide for an alternative to the fixed leak check intervals by

permitting the implementation of a program in which operators could

incorporate a schedule of maintenance actions, training, and periodic

leak checks into their FAA-approved maintenance program. These

commenters state that merely performing more leak checks at greater

frequencies will not, by itself, address the blue ice problem. Instead,

other maintenance tasks, such as replacing seals at regular intervals

and establishing effective communication procedures between maintenance

personnel and the flight crew, play more significant roles in

addressing blue ice safety concerns. The commenters request that

compliance periods for leak checks be adjusted in accordance with

existing FAA-approved reliability programs, or be increased to ``C''

check intervals, provided that certain maintenance and training

programs were initially included in the maintenance program.

The FAA concurs that these commenters' suggestions have merit. The

FAA has determined that an increase in the leak check intervals could

be justified if the equipment is demonstrated to be highly reliable,

and a program of regular maintenance and training is implemented. The

FAA has revised proposed paragraph (b) of the supplemental AD to

include specific procedures considered to be essential in such a

program. These procedures include: (1) Repetitive replacement of seals,

(2) leak checks at various intervals depending upon the valve

configuration, (3) leak checks of flush/fill line caps, (4) visual

checks conducted by maintenance personnel at regular intervals to

detect leakage, (5) procedures for reporting discrepancies, and (6)

training programs for maintenance and service personnel that include

information on ``Blue Ice Awareness'' and the hazards of blue ice. The

proposal specifically would extend the leak check interval for certain

valves to 5,000 flight hours (which is equivalent to a ``C'' check for

the majority of affected operators), provided the specified program of

maintenance and training is implemented.

Recordkeeping

Some commenters request that proposed paragraph (b) of the NPRM be

revised to specify that, once operators have acceptably revised their

maintenance program to include the specified actions, the AD is no

longer ``applicable'' to those operators. In effect, the maintenance

program revision should be considered ``terminating action'' for the

AD. These commenters would prefer to accomplish all of their AD-

required leak check tasks within the parameters of their FAA-approved

maintenance program, since ``operators have more flexibility in

adjusting leak check intervals in accordance with their FAA-approved

reliability programs and recordkeeping requirements are less

cumbersome.'' The commenters point out that paragraph (b) of the

previous NPRM denies operators the opportunity to integrate their leak

check tasks into their maintenance program, since ``the NPRM fails to

indicate that AD recording procedures are not in effect, and disallows

the opportunity to ever adjust the leak check intervals without seeking

approval under the alternative method of compliance provision.'' The

commenters request that, for these operators, the proposed rule provide

for the use of an alternative method of recordkeeping to that otherwise

required by Federal Aviation Regulations (FAR) 91.417 (``Maintenance

records'') and 121.380 (``Maintenance recording requirements'').

The FAA does not concur with the commenters' request to revise the

proposal to indicate in any way that it is ``no longer applicable''

once the revision to the FAA-approved maintenance program is

implemented and the appropriate logbook entry made. The FAA considers

that, even though this proposed AD would affect the maintenance

program, it is of such importance that it warrants other than

``normal'' procedures to be followed in certain aspects. Specifically,

under ``normal'' maintenance program procedures, the PMI is authorized

to approve any revisions of the maintenance program, including

adjustments of the leak check intervals. However, for reasons detailed

below, the FAA has determined that the PMI is not the appropriate FAA

official for adjusting the compliance intervals for leak checks

specified by the terms of this AD.

Likewise, the FAA does not concur with the commenters' request to

revise the proposal to provide specifically for the use of an

alternative method of recordkeeping. Although the FAA has included such

a provision in other rulemaking actions [reference, for example, AD 92-

22-08 R1, amendment 39-8591 (58 FR 32281, June 9, 1993); and AD 92-22-

09 R1, amendment 39-8590 (58 FR 32278, June 9,1993); both of which

require the implementation of a corrosion prevention and control

program on certain transport category airplanes], the FAA has been

unable to confirm that there has been any case in which an operator has

found it necessary to use such alternative recordkeeping methods.

Therefore, the FAA concludes that the recordkeeping methods currently

required by FAR 91.417 and 121.380 are sufficient, and there is no need

to include a specific provision in this proposed rule for alternatives.

Principal Maintenance Inspector (PMI) Involvement

Some commenters recommend that the FAA recognize the merit in

delegating complete program oversight responsibility to the cognizant

PMI, once an operator has an approved program in accordance with the

alternative provision of proposed paragraph (b). These commenters point

out that justification for issuing the proposed AD is based on the

premise that certain operators may not have a sufficiently

comprehensive maintenance program currently in place to address the

blue ice safety concern. However, once a proper maintenance program for

handling the blue ice safety concerns has been approved by the FAA and

adopted, there is no longer a safety concern to warrant oversight by

the Seattle ACO. The administration of handling this program should be

subject to oversight by the PMI and, as is normal for the regular

maintenance program as a whole, the PMI should be the FAA official with

the authority to approve any future adjustments to the leak check

intervals.

Although the FAA agrees that the PMI may be permitted certain

oversight of the proposed alternative maintenance program provision of

the rule (discussed above with regard to recordkeeping), the FAA does

not agree that the PMI should be tasked with approving adjustments to

the leak check intervals. In order for the PMI to have some basis for

changing the intervals, he/she would need to know (1) when to expect

the valve to start leaking, and (2) how to ensure that the leak check

interval does not allow the valve to reach that point. These two

important items are related to the concept of ``failure threshold

criteria.'' The FAA has reviewed available service history data (as

well as comments submitted to this and previous NPRM's) to evaluate

which valves, if any, appear to have ``failure threshold criteria,''

and what those criteria are. While certain failure modes for valves

have been identified, the failure threshold criteria are difficult to

define in many cases. For example:

1. ``Normal'' seal wear will eventually cause a valve to leak. Such

seal wear should be a relatively predictable cause of failure for any

given operator.

2. Developmental problems related to valve or installation design

problems (i.e., use of incorrect seal materials) may cause leakage

after the initial installation, but after the design ``fix'' is made

and installed, leakage from this type of problem should stop.

3. Entrapment of waste materials on valve sealing surfaces can

cause leakage; but this does not appear to be related to the valve's

time-in-service, in that such entrapment is as likely to occur on the

first cycle as on a later cycle. Entrapment of waste matter on the

sealing surfaces has been known to cause an increase in operating

torque of the valve handle; this would be a failure threshold criterion

for ball valves [which the FAA has incorporated as part of the

maintenance requirements for the in-line drain valves, as specified in

proposed paragraph (b) of this supplemental NPRM]. For certain other

types of valves, however, entrapment of foreign matter does not yield

such an indicator.

4. The valve may be damaged during service on any particular cycle,

assuming it is in a position where it is accessible during normal

servicing. Such damage during servicing, or even incorrect servicing

(i.e., failure to install the plug in a donut valve), may be failure

modes especially for service panel-mounted valves, which are

accessible. However, they are not failure modes for in-line drain

valves because these valves are not accessible during normal servicing.

As one can readily recognize, different valves may or may not be

susceptible to these modes of failure, depending upon the valve design,

installation location, maturity of design (all fixes incorporated), and

other factors. The data available to the FAA simply do not indicate

which failure modes are most likely to cause leakage for any particular

valve.

Based on the most recent analysis and data available, however, the

FAA has determined that only the in-line drain ball valve, as installed

in accordance with Boeing Service Bulletin 727-38-0021, dated July 30,

1992, may have specific failure threshold criteria. A PMI could use

these criteria as a basis for adjusting leak check intervals with some

degree of confidence that the valve would not be allowed to reach the

point when it would be expected to start leaking. Given the high

reliability of these valves (which have a very low total number of

leaks from any cause), and the element of relative predictability of

failure modes (change seals regularly to avoid seal wear problems, fix

the valve if high operating torque is evident, etc.), the FAA has

determined that it is appropriate to allow these valves to be leak

checked at intervals of 5,000 flight hours (equivalent to a ``C''

check). The FAA considers it impractical, however, to allow the PMI to

extend the leak check interval only for these in-line drain ball valve

installations. In any case, a leak test at ``C'' check intervals

provides assurance that operators are following correct maintenance

procedures.

The current data do not convince the FAA that service panel-mounted

valves have been demonstrated (unambiguously) to be as reliable as the

ball valve. The ratio of failures from ``unpredictable'' failure modes

to failures from ``predictable'' failure modes is not known for these

valves. In light of this, a PMI would have no data on which to base an

extension of a leak check interval for panel-mounted valves with the

assurance that the valve would not fail within the adjusted interval.

Further, PMI's who work with smaller operators would not see

sufficient data to give them the assurance that an expanded leak check

interval for any valve is justified.

Since failure threshold criteria and definitive leak/failure rate

data do not exist for the majority of the subject valves, it is

essential that the FAA, at the ACO level, have feedback as to the leak

and failure rates experienced in the field. Although the PMI's serve as

the FAA's critical link with the operators (and their oversight

responsibilities will not be minimized by this AD action), it is the

staff of the ACO that provides the engineering support necessary to

evaluate whether increases in repeat leak check intervals will maintain

an acceptable level of safety. Additionally, given that possible new

relevant issues might be revealed during the approval process, it is

imperative that the engineering staff at the ACO have such feedback.

Relationship of Leak Checks to Certification Maintenance Requirements

(CMR)

Several commenters state that, because this proposal is considered

to be a model for future AD actions applicable to other airplanes

(presumably including newly-delivered aircraft that will be configured

with similar in-line drain valves), the adoption of proposed paragraph

(a) will require repetitive leak checks on all newly delivered

aircraft. The commenters view this as ``tantamount to issuing a

certification maintenance requirement (CMR)'' via the AD process.

The FAA does not concur. CMR items are intended to be repetitive

inspections or component replacements for equipment, systems, and

installations. Accomplishment of CMR items would ensure that the

statistical probability of certain failures that could occur during

operation of the airplane does not exceed the limitations specified in

Sec. 25.1309 (``Equipment, systems, and installations'') of the FAR,

which is applicable to the design and approval of transport category

airplanes. Further, CMR items are based on statistical safety analyses

of airplane electrical, electronic, hydraulic, pressurization, and

propulsion systems. These analyses must be completed by the

manufacturer and approved by the FAA prior to the issuance of an

airplane Type Certificate (TC). Following issuance of the TC, those

inspections, component replacements, or overhaul interval requirements

for airplane systems that are based on in-service experience with the

airplane, but that do not result in re-evaluation of the basic

statistical analysis on which approval of the system is based, do not

qualify as CMR items.

The leak check schedule proposed in this notice is not related to

compliance of the airplane design with the statistical evaluation

requirements of FAR Sec. 25.1309 for equipment, systems, and

installations. For this reason, the proposed leak checks do not qualify

as a CMR item. The intent of the proposed leak checks is to address the

unsafe condition presented by the problems associated with blue ice;

the appropriate vehicle for mandating actions to address an unsafe

condition is the airworthiness directive.

Compliance Time for Proposed Maintenance Program Change

Several commenters request that the proposed 30-day compliance time

for revising the operators' FAA-approved maintenance programs be

extended to 180 days. The commenters consider that the proposed time is

too short, since implementing such a revision will require addition

work hours, personnel, and material.

The FAA concurs. In view of the increased scope of the proposed

changes to the maintenance program, the FAA has revised paragraph (b)

to require compliance within 180 days. This will allow operators

adequate time to implement the required revisions to the maintenance

program, both logistically and administratively. It will also provide

time for the development of the necessary training programs and the

training of personnel in the new procedures.

Cost Impact

There are approximately 1,752 Boeing Model 727 series airplanes of

the affected design in the worldwide fleet, operated by 153 operators.

It is estimated that 1,277 airplanes of U.S. registry and 54 U.S.

operators would be affected by this AD. The FAA estimates that it would

take approximately 4 work hours per airplane lavatory drain (2 drains

per airplane) to accomplish a leak check, and the average labor cost

would be $55 per work hour.

For the 1,077 airplanes that have donut/cap type or other approved

drain valves (excluding Shaw Aero drain valves) installed in both drain

systems, approximately 15 leak checks per airplane would be required

each year. For the 36 airplanes that have Shaw Aero drain valves

installed in both drain systems, approximately 3 leak checks per

airplane would be required each year. For the 164 airplanes that have a

ball valve installed in the forward lavatory drain and a Shaw Aero

drain valve installed in the aft lavatory drain, approximately 2 leak

checks of the forward drain and 3 leak checks of the aft drain would be

required per year. Based on these figures, the total annual (recurring)

cost impact of the repetitive leak checks on U.S. operators is

estimated to be $7,336,120.

The 1,277 airplanes of U.S. registry have, on an average, 3 flush/

fill lines per airplane. The FAA estimates that the installation cost

of a level lock cap assembly would require approximately 2 work hours

to accomplish, at an average labor cost of $55 per work hour. Required

parts are estimated to be $275 per drain installation. Based on these

figures, the total cost impact of the requirement to install a cap on

the flush/fill lines is estimated to be $1,474,935, or an average of

$1,155 per airplane.

The number of required work hours, as indicated above, is presented

as if the accomplishment of the actions proposed in this AD were to be

conducted as ``stand alone'' actions. However, in actual practice,

these actions would be accomplished coincidentally or in combination

with normally scheduled airplane inspections and other maintenance

program tasks. Therefore, the actual number of necessary ``additional''

work hours would be minimal in many instances. Additionally, any costs

associated with special airplane scheduling would be minimal.

In addition to the costs discussed above, for those operators who

elect to comply with proposed paragraph (b) of this AD action, the FAA

estimates that it would take approximately 40 work hours per operator

to incorporate the lavatory drain system leak check procedures into the

maintenance programs, at an average labor cost of $55 per work hour.

Based on these figures, the total cost impact of the proposed

maintenance revision requirement of this AD action on the 54 U.S.

operators is estimated to be $118,800, or $2,200 per operator.

The ``total cost impact'' figures described above are based on

assumptions that no operator has yet accomplished any of the proposed

requirements of this AD action, and no operator would accomplish those

actions in the future if this AD were not adopted.

The FAA recognizes that the obligation to maintain aircraft in an

airworthy condition is vital, but sometimes expensive. Because AD's

require specific actions to address specific unsafe conditions, they

appear to impose costs that would not otherwise be borne by operators.

However, because of the general obligation of operators to maintain

aircraft in an airworthy condition, this appearance is deceptive.

Attributing those costs solely to the issuance of this AD is

unrealistic because, in the interest of maintaining safe aircraft, most

prudent operators would accomplish the required actions even if they

were not required to do so by the AD.

A full cost-benefit analysis has not been accomplished for this

proposed AD. As a matter of law, in order to be airworthy, an aircraft

must conform to its type design and be in a condition for safe

operation. The type design is approved only after the FAA makes a

determination that it complies with all applicable airworthiness

requirements. In adopting and maintaining those requirements, the FAA

has already made the determination that they establish a level of

safety that is cost-beneficial. When the FAA, as in this proposed AD,

makes a finding of an unsafe condition, this means that this cost-

beneficial level of safety is no longer being achieved and that the

proposed actions are necessary to restore that level of safety. Because

this level of safety has already been determined to be cost-beneficial,

a full cost-benefit analysis for this proposed AD would be redundant

and unnecessary.

Regulatory Impact

The regulations proposed herein would not have substantial direct

effects on the States, on the relationship between the national

government and the States, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

regulation (1) is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, will not have a significant economic impact,

positive or negative, on a substantial number of small entities under

the criteria of the Regulatory Flexibility Act. A copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting the Rules

Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend 14

CFR part 39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing amendment 39-5250 (51 FR

7767, March 6, 1986), and by adding a new airworthiness directive (AD),

to read as follows:

Boeing: Docket No. 90-NM-265-AD. Supersedes AD 86-05-07,

Amendment 39-5250.

Applicability: All Model 727 series airplanes, certificated in

any category.

Compliance: Required as indicated, unless previously

accomplished.

To prevent engine damage or separation, airframe damage, and/or

hazard to persons or property on the ground as a result of ``blue

ice'' that has formed from leakage of the lavatory drain system and

dislodged from the airplane, accomplish the following:

(a) Except as provided in paragraph (b) of this AD, accomplish

the applicable procedures specified in paragraphs (a)(1), (a)(2),

(a)(3), (a)(4), and (a)(5) of this AD:

(1) For each lavatory drain system, forward or aft, that has an

in-line drain valve installed, Kaiser Electroprecision part number

2651-329-5 (or higher dash number): Within 1,500 flight hours after

the effective date of this AD, and thereafter at intervals not to

exceed 1,500 flight hours, accomplish the following:

(i) Conduct a leak check of the dump valve (in-tank valve that

is spring loaded closed and operable by a T-handle at the service

panel), ball valve, and cap valve. The ball valve and cap valve leak

checks must be performed with a minimum of 3 pounds per square inch

differential pressure (PSID) applied across each valve. If the cap

valve has an inner door with a second positive seal, only the inner

door must be tested.

(ii) Visually inspect the seal on the outer door for wear or

damage that may cause leakage. Any worn or damaged seal must be

replaced, prior to further flight, in accordance with the valve

manufacturer's maintenance manual.

(2) For each lavatory drain system, forward or aft, that has a

service panel drain valve installed, Kaiser Electroprecision part

number 0218-0032-8 (or higher dash number) or Shaw Aero Devices part

number 10101000C-N (or higher dash number): Within 1,000 flight

hours after the effective date of this AD, and thereafter at

intervals not to exceed 1,000 flight hours, conduct a leak check of

the dump valve and drain valve. The drain valve leak check must be

performed with a minimum of 3 PSID applied across the valve.

(3) For other forward or aft lavatory drain systems not

addressed in paragraph (a)(1) or (a)(2) of this AD: Within 200

flight hours after the effective date of this AD, and thereafter at

intervals not to exceed 200 flight hours, conduct a leak check of

the dump valve and the drain valve at the service panel. The drain

valve leak check must be performed with a minimum 3 PSID applied

across the valve.

(4) For flush/fill lines: Within 5,000 flight hours after the

effective date of this AD, and thereafter at intervals not to exceed

5,000 flight hours, conduct a leak check of the cap on the flush/

fill line. This leak check must be made with a minimum of 3 PSID

applied across the cap.

(5) If a leak is discovered during any leak check required by

paragraph (a) of this AD, prior to further flight, accomplish one of

the following procedures:

(i) Repair the leak; or

(ii) Drain the affected lavatory system and placard the lavatory

inoperative until repairs can be accomplished.

(b) As an alternative to the requirements of paragraph (a) of

this AD: Within 180 days after the effective date of this AD, revise

the FAA-approved maintenance program to include the requirements

specified in paragraphs (b)(1), (b)(2), (b)(3), (b)(4), (b)(5),

(b)(6), and (b)(7) of this AD.

(1) Replace the valve seals in accordance with the applicable

schedule specified in paragraphs (b)(1)(i) and (b)(1)(ii) of this

AD. Any revision to this replacement schedule must be approved by

the Manager, Seattle Aircraft Certification Office (ACO), FAA,

Transport Airplane Directorate.

(i) For each lavatory drain system, forward or aft, that has an

in-line drain valve installed, Kaiser Electroprecision part number

2651-329-5 (or higher dash number): Replace the seals within 5,000

flight hours after revision of the maintenance program in accordance

with paragraph (b) of this AD, and thereafter at intervals not to

exceed 52 months.

(ii) For each lavatory drain system, forward or aft, that has

any other type of drain valve: Replace the seals within 5,000 flight

hours after revision of the maintenance program in accordance with

paragraph (b) of this AD, and thereafter at intervals not to exceed

18 months.

(2) Conduct periodic leak checks of the lavatory drain systems

in accordance with the applicable schedule specified in paragraphs

(b)(2)(i), (b)(2)(ii), (b)(2)(iii), and (b)(2)(iv) of this AD. Any

revision to the leak check schedule must be approved by the Manager,

Seattle ACO, FAA, Transport Airplane Directorate.

(i) For forward lavatory drain systems modified in accordance

with Boeing Service Bulletin 727-38-0021, dated July 30, 1992

[installing an in-line drain valve, Kaiser Electroprecision part

number 2651-329-5 (or higher dash number)]: Within 5,000 flight

hours after revision of the maintenance program in accordance with

paragraph (b) of this AD, and thereafter at intervals not to exceed

5,000 flight hours, conduct leak checks. The ball valve and cap

valve leak checks must be performed with a minimum of 3 pounds per

square inch differential pressure (PSID) applied across each valve.

If the cap valve has an inner door with a second positive seal, only

the inner door must be tested. Additionally, visually inspect the

seal on the outer door for wear or damage that may cause leakage;

any worn or damaged seal must be replaced, prior to further flight,

in accordance with the valve manufacturer's maintenance manual.

(ii) For each lavatory drain system, forward or aft, that has a

service panel drain valve installed, Kaiser Electroprecision part

number 0218-0032-8 (or higher dash number) or Shaw Aero Devices part

number 10101000C-N (or higher dash number): Within 1,000 flight

hours after revising the maintenance program in accordance with

paragraph (b) of this AD, and thereafter at intervals not to exceed

1,000 flight hours, conduct leak checks of the dump valve and drain

valve . The drain valve leak check must be performed with a minimum

of 3 PSID applied across the valve.

(iii) For each lavatory drain system, forward or aft, that

incorporates either ``donut'' valves, Kaiser Electroprecision part

number 4259-20 or 4259-31; or that incorporates ``taco'' valves,

Kaiser Electroprecision part number 2651-311-1, -2, -3, -4, -5, -6,

or -7: Within 200 flight hours after revising the maintenance

program in accordance with paragraph (b) of this AD, and thereafter

at intervals not to exceed 200 flight hours, conduct leak checks of

the dump valve and the drain valve. The drain valve leak check must

be performed with a minimum 3 PSID applied across the valve.

(iv) For each lavatory drain system, forward or aft, that

incorporates any other type of approved valves: Within 400 flight

hours after revising the maintenance program in accordance with

paragraph (b) of this AD, and thereafter at intervals not to exceed

400 flight hours, conduct leak checks of the dump valve and the

drain valve. The drain valve leak check must be performed with a

minimum 3 PSID applied across the valve.

(3) For flush/fill lines: Within 5,000 flight hours after

revising the maintenance program in accordance with paragraph (b) of

this AD, and thereafter at intervals not to exceed 5,000 flight

hours, conduct a leak check of the cap on the flush/fill line. This

leak check must be made with a minimum of 3 PSID applied across the

cap.

(4) Provide procedures for accomplishing visual inspections to

detect leakage, to be conducted by maintenance personnel at

intervals not to exceed 4 calendar days or 45 flight hours, which

ever occurs later.

(5) Provide procedures for reporting leakage. These procedures

shall provide that any ``blue streak'' findings must be reported to

maintenance and that, prior to further flight, the leaking system

shall either be repaired, or be drained and placarded inoperative.

(i) For systems incorporating an in-line drain valve, Kaiser

Electroprecision part number 2651-329-5 (or higher dash number): The

reporting procedures must include provisions for reporting to

maintenance any instances of abnormal operating torque of the valve

handle for the in-line drain valve, as observed by service personnel

during normal servicing.

(A) Additionally, these provisions must include procedures for

either: prior to further flight, following the in-line drain valve

manufacturer's recommended troubleshooting procedures and correction

of the discrepancy; or prior to further flight, draining the

lavatory system and placarding it inoperative until the correction

of the discrepancy can be accomplished.

(B) If the drain system also includes an additional service

panel drain valve, Kaiser Electroprecision part number 0218-0032-8

(or higher dash number) or Shaw Aero Devices part number 10101000C-N

(or higher dash number), indications of abnormal operating torque of

the valve handle for the in-line drain valve need not be addressed

immediately if a leak check of the additional valve indicates no

leakage or other discrepancy. In these cases, repair of the in-line

drain valve must be accomplished within 1,000 flight hours after the

leak check of the additional service panel drain valve.

(6) Provide training programs for maintenance and servicing

personnel that include information on ``Blue Ice Awareness'' and the

hazards of blue ice.

(c) For operators who elect to comply with paragraph (b) of this

AD: Any revision to (i.e., extension of) the leak check intervals

required by paragraph (b) of this AD must be approved by the

Manager, Seattle ACO, FAA, Transport Airplane Directorate. Requests

for such revisions must be submitted to the Manager of the Seattle

ACO through the FAA Principal Maintenance Inspector (PMI), and must

include the following information:

(1) The operator's name;

(2) A statement verifying that all known cases/indicates of

leakage or failed leak tests are included in the submitted material;

(3) The type of valve (make, model, manufacturer, vendor part

number, and serial number);

(4) The period of time covered by the data;

(5) The current FAA leak check interval;

(6) Whether or not seals have been replaced between the seal

replacement intervals required by this AD;

(7) Whether or not leakage has been detected between leak check

intervals required by this AD, and the reason for leakage (i.e.,

worn seals, foreign materials on sealing surface, scratched or

damaged sealing surface or valve, etc.);

(8) Whether or not any leak check was conducted without first

inspecting or cleaning the sealing surfaces, changing the seals, or

repairing the valve. [If such activities have been accomplished

prior to conducting the periodic leak check, that leak check shall

be recorded as a ``failure'' for purposes of the data required for

this request submission. The exception to this is the normally

scheduled seal change in accordance with paragraph (b)(1) of this

AD. Performing this scheduled seal change prior to a leak check will

not cause that leak check to be recorded as a failure.]

Note 1: Requests for approval of revised leak check intervals

may be submitted in any format, provided the data give the same

level of assurance specified in this paragraph.

Note 2: For the purposes of expediting resolution of requests

for revisions to the leak check intervals, the FAA suggests that the

requestor summarize the raw data; group the data gathered from

different airplanes (of the same model) and drain systems with the

same kind of valve; and provide a recommendation from pertinent

industry group(s) and/or the manufacturer specifying an appropriate

revised leak check interval.

(d) For all airplanes: Within 5,000 flight hours after the

effective date of this AD, install a cap on the flush/fill lines for

forward, aft, and executive lavatories in accordance with Boeing

Service Bulletin 727-38-0021, dated July 30, 1992.

(e) For any affected airplane acquired after the effective date

of this AD: Before any operator places into service any airplane

subject to the requirements of this AD, a schedule for the

accomplishment of the leak checks required by this AD shall be

established in accordance with either paragraph (e)(1) or (e)(2) of

this AD, as applicable. After each leak check has been performed

once, each subsequent leak check must be performed in accordance

with the new operator's schedule, in accordance with either

paragraph (a) or (b) of this AD as applicable.

(1) For airplanes previously maintained in accordance with this

AD, the first leak check to be performed by the new operator must be

accomplished in accordance with the previous operator's schedule or

with the new operator's schedule, whichever would result in the

earlier accomplishment date for that leak check.

(2) For airplanes that have not been previously maintained in

accordance with this AD, the first leak check to be performed by the

new operator must be accomplished prior to further flight, or in

accordance with a schedule approved by the FAA PMI, but within a

period not to exceed 200 flight hours.

(f) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, Seattle ACO, FAA, Transport

Airplane Directorate. Operators shall submit their requests through

an appropriate FAA PMI, who may add comments and then send it to the

Manager, Seattle ACO.

Note 3: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Seattle ACO.

Note 4: For any valve that is not eligible for the extended leak

check intervals of this AD: To be eligible for the leak check

interval specified in paragraphs (a)(1), (a)(2), (b)(2)(i), and

(b)(2)(ii), the service history data of the valve must be submitted

to the Manager, Seattle ACO, FAA, Transport Airplane Directorate,

with a request for an alternative method of compliance. One of the

factors that the FAA will consider in approving alternative valve

designs is whether the valve meets Boeing Specification S417T105 or

10-62213.

(g) Special flight permits may be issued in accordance with

Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the

airplane to a location where the requirements of this AD can be

accomplished.

Issued in Renton, Washington, on March 14, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-6340 Filed 3-17-94; 8:45 am]

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