Airworthiness Directives; Boeing Model 747-400, 757, and 767 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-140-AD; Amendment 39-9558; AD 96-07-09]

Airworthiness Directives; Boeing Model 747-400, 757, and 767

Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to Boeing Model 747-400, 757, and 767 series airplanes, that

requires a revision to the Airplane Flight Manual that advises flight

crews to monitor the engine indication and crew alerting system (EICAS)

for ``status'' level messages pertaining to impending engine fuel

filter bypass. This amendment also requires the installation of

upgraded EICAS computers that provide ``advisory'' level messages to

indicate such bypass conditions. This amendment is prompted by a

finding that EICAS computers currently installed on these airplanes do

not provide an appropriate indication to the flight crew of an

impending engine fuel filter bypass condition. The actions specified by

this AD are intended to ensure that the flight crew is appropriately

aware of conditions involving a severely contaminated airplane fuel

system and the associated increased potential for engine power loss.

EFFECTIVE DATE: May 3, 1996.

ADDRESSES: Information related to this action may be examined at the

Federal Aviation Administration (FAA), Transport Airplane Directorate,

Rules Docket No. 94-NM-140-AD, 1601 Lind Avenue, SW., Renton,

Washington.

FOR FURTHER INFORMATION CONTACT: G. Michael Collins, Aerospace

Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft

Certification Office, 1601 Lind Avenue, SW., Renton, Washington;

telephone (206) 227-2689; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to Boeing Model 747-400, 757, and 767

series airplanes was published in the Federal Register on May 24, 1995

(60 FR 27446). That action proposed to require a revision to the FAA-

approved Airplane Flight Manual (AFM) that would advise flight crews to

monitor the engine indication and crew alerting system (EICAS) for

``status'' level messages pertaining to impending engine fuel filter

bypass. That action also proposed to require the installation of

upgraded EICAS computers that provide ``advisory'' level messages to

indicate such bypass conditions.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

Support for the Proposal

One commenter supports the proposed rule.

Request To Withdraw the Proposal: Addressed Unsafe Condition Is

Extremely Remote

One commenter requests that the FAA define ``unsafe condition'' as

required by part 39 (``Airworthiness directives'') of the Federal

Aviation Regulations (FAR) (14 CFR 39), and discern whether a condition

is unsafe if its occurrence is ``extremely remote.'' This commenter

points out that data previously presented to the FAA demonstrate that

the risk of solid particulate contaminated fuel in excess of that

already addressed during engine certification is ``less than 1 x

108 [sic],'' making such contamination an ``extremely remote

[sic]'' event. This

[[Page 14609]]

commenter asserts that, if the risk of gross fuel contamination is

considered extremely remote, then it does not matter that the flight

crew be made aware of such contamination, since the possibility that

gross contamination will occur does not warrant that a status level

message on the EICAS system be active. Since part 25.1305(c)(6)

(``Powerplant instruments'') of the FAR requires only that a fuel

filter bypass warning be installed, the present indication system

satisfies the certification standards.

This commenter states that if the occurrence of an event is

``extremely remote'' or less, then the demonstration of an unsafe

condition required by part 39 has not been achieved for this AD action.

Any FAA determination on what is unsafe should not extend beyond the

type certification requirements. This commenter considers that the

FAA's adoption of risk assessment methodology is critical to place the

relative risks addressed in the proposed AD to proper perspective.

The FAA does not concur with the commenter. According to section

39.1 of the FAR (14 CFR 39.1), the issuance of an AD is based on the

finding that an unsafe condition exists or is likely to develop in

aircraft of a particular type design. That section of the FAR does not

specify that an unsafe condition is considered unsafe, or a condition

is ``likely to develop,'' only if it meets a specific reliability

standard, such as suggested by the commenter. Further, the criteria of

the probability of an occurrence being ``extremely remote

(improbable),'' as described in section 25.1309 (``Equipment, systems,

and installations'') of the FAR (14 CFR 25.1309), is on the order of 1

x 10-9. Thus, it is a condition that is not expected to result in

any occurrences during the life of the affected fleet. The FAA points

out, however, that there have been several recent incidents of fuel

contamination on transport category airplanes that caused the blockage

of one or more engine fuel filters. Because of the awareness provided

to the flight crew by the cockpit indication of the impending filter

bypass, the flight crew was able to land the airplanes safely at the

nearest airport. These recent events demonstrate that (1) the risk of

the addressed unsafe condition is much greater than ``extremely

remote;'' and (2) the impending fuel filter bypass message will provide

the flight crew with timely indication and awareness before any

engine's fuel filter is clogged to the point that the contaminated fuel

bypasses the filter and causes operational problems with the engine(s).

Further, as explained in detail in the preamble to the proposal,

relevant service data has led the FAA to determine that the current use

of a ``status'' level message to indicate an impending engine fuel

filter bypass creates an unsafe condition, since such messages do not

provide information to the flight crew at an appropriate level of

awareness to enable them to take immediate action to correct the

condition. Using a ``status'' level message to indicate an impending

engine fuel filter bypass condition could result in the flight crew

being unaware of a severely contaminated airplane fuel system and the

associated increased potential for engine power loss. It is this

condition that the FAA considers to be unsafe for, if it is not

corrected, it could result in the airplane landing with reduced engine

power, or the total loss of engine power before the airplane is able to

reach a suitable landing site.

Request To Withdraw the Proposal: No Documented Occurrences of the

Unsafe Condition

Several commenters contend that there have been no documented in-

service events to justify the proposed AD. These commenters state that

historical jet transport safety records disclose that no accident has

occurred that was related to solid particulate contaminated fuel from

the period of 1959 through 1993, which involved over 230 million

aircraft flights. These commenters point out that, although there have

been numerous occurrences of annunciation to the flight crew of

impending fuel filter bypass, none of the affected fleet has ever

experienced loss of thrust or interruption of power subsequent to a

fuel filter bypass indication. In fact, the opposite situation has

occurred several times: engine power was lost due to contaminated fuel,

but there was no indication of an impending fuel filter bypass

annunciated to the crew. The manufacturer also describes 7 events that

occurred on the affected fleet where permanent loss of thrust greater

than one propulsion system occurred; although 5 of these events were a

result of water contamination and the other 2 were associated with

contamination of the engine vane and bleed control system on a specific

engine type, none of the 7 events were annunciated to the flight crew

by an impending fuel filter bypass indication. These commenters assert

that lack of substantiation for the FAA's position that an unsafe

condition exists is reason to withdraw the proposal.

The FAA does not concur. Although there have been no reported cases

of loss of thrust or interruption of power subsequent to a fuel filter

bypass indication, the potential for this unsafe condition exists as

long as the potential for contaminated fuel exists. This AD action

addresses that potential unsafe condition.

As stated earlier, there have been several recent incidents of fuel

contamination on transport category airplanes that caused the blockage

of one or more engine fuel filters. The flight crews of the incident

airplanes were made aware of this condition by the cockpit indication

of the impending filter bypass and, in each case, were able to land the

airplanes safely. These recent events demonstrate that the impending

fuel filter bypass message should provide the flight crew with timely

indication and awareness before any engine's fuel filter is clogged to

the point that the contaminated fuel bypasses the filter and causes

operational problems with the engine(s). The FAA maintains that early

recognition of an impending fuel filter bypass will reduce the

potential hazards associated with subsequent power loss and engine

shutdowns.

Request To Withdraw the Proposal: Maintenance Practices Should Be

Followed Properly

Several commenters indicate that the unsafe condition could be

better addressed by improving maintenance practices relevant to the

fuel system, rather than by requiring the proposed EICAS upgrade. These

commenters state that ``gross contamination'' of the fuel to the levels

discussed in the notice can only result from long-term negligence and

disregard of standard servicing and maintenance practices. These

commenters contend that appropriate maintenance programs relative to

airplane fuel systems are required by the FAR: namely, parts

121.135(b)(18) (``Maintenance manual requirements--contents'') and

121.1369(b) (``Manual requirements'') [14 CFR 121.135(b)(18) and

21.1369(b)]. To meet the requirements of these regulations, maintenance

programs must entail controls and refueling procedures, including

sampling prior to fueling, to ensure that fueling processes will be

safe and clean. Therefore, if maintenance programs are followed

correctly, there is ample assurance that the possibility of

contamination of the fuel system will be prevented. Finally, these

commenters point out that ensuring that proper aircraft fuel servicing

and storage methods are followed would be far more economical to

operators than installing the proposed EICAS modification.

[[Page 14610]]

The FAA does not concur. Service experience has demonstrated that,

despite regulations that mandate the proper maintenance of fuel

systems, fuel contamination in airplane fuel systems continues to

occur. In fact, subsequent to the issuance of the notice, the FAA was

advised of three recent incidents of fuel system contamination on

transport category airplanes. In these incidents, the engine fuel

filter bypass indication system alerted the flight crew that impending

fuel filter bypass conditions were present on one or more engines:

1. The first of these incidents occurred during the climb phase of

flight. At that time, the crew elected to return to the departure

airport. During the approach to that airport, the other engine's fuel

filter bypass annunciation light illuminated.

2. The second incident occurred three hours after the airplane had

departed the airport. At that time, the fuel filter bypass annunciation

light illuminated on one engine. Following this indication, and during

the airplane's descent to the destination airport, the other engine's

fuel filter bypass annunciation light illuminated.

3. In the third incident, at approximately four hours into the

flight, a fuel filter bypass alert occurred on each of the airplane's

three engines.

Investigation into all three of these events revealed that

apparently the contamination of the airplanes' fuel systems was the

result of malfunctions of the fuel hydrant system installed at a

particular airport where these airplanes took on fuel.

By citing these recent incidents, which demonstrate the need for

flight crew awareness of impending engine fuel filter bypass, the FAA

emphasizes that it is likely events of fuel system contamination will

occur in the future, despite the industry's efforts to maintain a

``clean'' fuel supply.

Fuel contamination can affect the operation of all engines on an

airplane. Section 25.1305(c)(6) of the FAR [14 CFR 25.1305(c)(6)]

requires an indication to alert the flight crew that an engine's fuel

filter is contaminated before the filter is clogged to the point that

the fuel bypasses the filter(s) and allows the contamination to pass to

the engine(s). A separate indication is required for each engine's fuel

filter. The purpose of these requirements is to provide the flight crew

with an indication that the fuel is contaminated before the

contamination causes flameout or operational anomalies of one engine or

multiple engines. This indication of impending engine fuel filter

bypass provides the flight crew with important information when they

still have an opportunity to consider action such as diverting to an

alternative airport.

Request To Withdraw the Proposal: Distraction of Flight Crew by

Alert Messages

Several commenters contend that the proposed ``interim'' action

requiring the flight crew to check the EICAS status page, and the

proposed final action of modifying the EICAS computer to display the

fuel filter bypass message as an ``advisory'' level message, will

result in the confusion and distraction of the flight crew. These

commenters point out that flight crews are trained to check the

``status'' message display before engine start; therefore, checking the

``status'' message display during flight contradicts their basic

operational practices and likely will cause them confusion.

Additionally, the flight crew could be distracted by other ``status''

level messages that may occur during a flight.

Another commenter indicates that the reliability of the sensor

switch for the fuel filter bypass indication is rated at 1 x 10-4.

From this reliability standpoint, it is obvious that ``nuisance

warnings'' (that is, indications of a fuel filter bypass condition when

one does not actually exist) will occur more frequently than will an

actual gross fuel contamination event (which has a 1 x 10-8

probability). In light of this, the commenter considers that the

proposed rule should address the safety concerns that will be created

by the flight crew's response to what may amount to ``nuisance''

messages. This commenter and several others believe that safety will be

reduced when flight crews are tasked to respond to such false

indications by (1) making unnecessary flight diversions, (2) landing at

airports that they are not familiar with; and (3) shutting down engines

needlessly.

The FAA does not concur with the commenters' suggestion that the

requirements of this AD will result in unnecessary distractions or

confusion of the flight crew.

``Status'' level messages do not provide immediate crew awareness;

the only sign given to the crew regarding ``status'' level information

is the appearance of the word ``STATUS'' on the EICAS screen. Under

ordinary circumstances, in order to find out the nature of a ``status''

level message, the flight crew has to take action to review the status.

Such a review normally is done when practical, based on the activity

level in the flight deck; in general, it is not done during flight.

``Advisory'' level messages, on the other hand, are brought to the

flight crew's attention by the appearance of the complete message on

the EICAS screen (e.g., the message ``R ENG FUEL FILT'' appears on the

existing EICAS screen of Model 767 series airplanes that are powered by

Pratt & Whitney JT9D engines). No additional action must be taken by

the flight crew in order to find out the nature of ``advisory'' alerts.

For the reasons discussed in detail in the proposal, the FAA finds

that an ``advisory'' level message is the appropriate level for

alerting the flight crew to an impending fuel filter bypass condition.

The requirement of this AD for the flight crew to respond to EICAS

``status'' level indications relative to an engine fuel filter bypass

message (by first checking the status page) is consistent with the

level of response required for an ``advisory'' level message. In

support of the FAA's position on this issue, two operators commented

that their crews are already trained to check the status page whenever

the status cue appears.

The FAA also does not concur with the commenters' suggestion that

the display of the fuel filter bypass message as an ``advisory'' level

message will cause a reduction in safety. On the contrary, an

``advisory'' level message appears on the upper EICAS display,

providing the flight crew with an immediate awareness of the impending

bypass condition, without the need to look up any status page to obtain

the relevant information necessary for reaction.

With regard to the possibility that flight crews would divert to an

alternative airport because of false indications of impending fuel

filter bypass, the FAA considers that, if false indications are

occurring frequently, then the reliability of the indication system

should be improved. However, other than the reliability level presented

by the commenter, no other data has been presented to the FAA to

indicate that the indication system is not reliable. In fact, one

operator commented that, because the fuel filter bypass system on its

fleet has a good reliability record, the proposed rule would not have

an operational impact on the affected fleet.

The FAA does acknowledge the commenters' concern, however, that

flight crews could divert to alternate airports because of an increased

awareness of other status level messages that may be displayed. To

address this, the FAA has revised paragraphs (a) and (b) of the final

rule to include the following sentence in the text that is to be added

to the Airplane Flight Manual (as interim action):

[[Page 14611]]

``If other status level messages are displayed, the flight crew

may deal with them in accordance with the appropriate operator

procedure.''

Request To Withdraw the Proposal: Current Level of Message

Indication Is Adequate

Several commenters assert that the proposed rule is not necessary

because the current flight crew indication system is adequate. The

flight crew is made aware of fuel filter problems via the ``status''

message system of the EICAS, which they must check prior to dispatch of

the airplane. The current ``status'' level message gives adequate

indication to the flight crew of an impending fuel filter bypass; from

this message, the flight crew can determine what action is required

prior to dispatch. Further, these commenters point out that the Master

Minimum Equipment List (MMEL) does not permit dispatch with an ``engine

fuel filter'' message indicated.

The FAA does not concur with these commenters. The original design

and operational philosophy of the EICAS on the affected airplanes is

that ``status'' level messages are to be reviewed by the flight crew

only prior to dispatch of the airplane. The FAA now considers that this

is not adequate for two reasons:

1. It does not meet the need for immediate crew awareness of an

impending fuel filter bypass during flight. The crew would not be

alerted to the fact that an engine fuel filter had became blocked

during a flight until the operation of one or more engines was

affected. This could result in the flameout of one or all engines.

2. The operational requirements under part 121 of the FAR permit

more than one flight under one ``airplane dispatch.'' This could result

in operating an airplane for several flights without checking for

``status'' level messages. In such cases, a message indicating an

impending fuel filter bypass could go unnoticed by the fight crew for

several flights.

Request To Withdraw the Proposal: Unsafe Condition Is Actually

Water in the Fuel

Two commenters state that the principal source of fuel

contamination in the affected airplanes is from water in the fuel and

the consequent formation of ice particles across the fuel filter due to

the sub-zero temperatures that occur during flight. These commenters

contend that there are either procedures or systems already in place

that effectively control this and thereby eliminate any associated

unsafe condition.

These commenters believe that the original reason for providing

flight crews with immediate indication of an impending engine fuel

filter bypass was to prompt them to activate the fuel heating system.

Some of the aircraft that would be affected by the proposed AD

incorporate a manual fuel heat system designed to increase the

temperature of the fuel upstream of the fuel filter to avoid blockage

of the filter due to ice accumulation. The fuel heat system servo valve

is activated by an electrical switch; and the fuel filter system

contains a differential pressure switch that sends a signal to lights

on the flight deck that indicate an impending fuel filter bypass

condition. The flight crew procedure for responding to this

illumination of the light is to activate the fuel heat system. These

procedures are to ensure that fuel heat is applied to the engine fuel

system to eliminate any blockage due to icing. Other aircraft affected

by the proposed AD have continuous fuel heating, which requires no

flight crew action or immediate indication. In light of this, the

commenters consider that no AD action is necessary.

The FAA does not concur. The original intent of indicating an

impending fuel filter bypass condition was to indicate clogging of the

fuel filter due to fuel contamination, not merely ice formation. While

it is true that the FAA has accepted the inclusion of a procedure in

the AFM for certain airplanes to prompt the flight crew to activate the

fuel heating system when the fuel filter bypass indication is

annunciated, this was not the original, nor only, intent for the

indication. [This has been confirmed by a review of the docket file for

the amendment to part 25 that established FAR 25.1305(c).]

Request To Withdraw the Proposal: ``Gross Contamination'' Is an

Undefined Concern

Several commenters request that the FAA define ``gross

contamination'' of fuel and determine its physical and chemical

properties. These commenters state that gross contamination has not

been defined and documentation of it has not been provided to

substantiate its existence. They consider it unrealistic and

inappropriate for the FAA to mandate protection against a condition

that has not been technically defined. One of these commenters points

to the description offered by the FAA in the preamble to the proposal

and states that fuel system contamination of the particulate size and

concentration described by the FAA would likely cause damage and/or

blockage to other fuel system components and reduce fuel flow without

ever causing an impending fuel filter bypass indication.

Other commenters argue that section 33.67 (``Airworthiness

standards--Fuel system'') of the FAR (14 CFR 33.67) allows for

continued operation of the aircraft with the maximum contamination rate

(specified in the FAR) for a period of time that exceeds the typical

maximum flight leg of the aircraft before the fuel filter bypass valve

opens. Based on this current certification design standard, the

commenters consider that the capacity of the filters currently

installed on the affected airplane is sufficient to allow the airplane

to continue to the destination airport following an impending bypass

indication.

The FAA responds to these comments by pointing out that part 25.997

(``Fuel filter or strainer'') specifies that fuel filters must:

``* * * Have the capacity (with respect to operating limitations

established for the engine) to ensure that engine fuel system

functioning is not impaired, with the fuel contaminated to a degree

(with respect to particle size and density) that is greater than

that established for the engine in part 33 [of the FAR].

``Gross contamination'' is defined in the context of this AD action

to include levels of fuel contamination that are greater than those

established for the engine in part 33 of the FAR. Examples of such

contamination that actually have been found in service include

microbial growth, sealant, lint, metal particles, fuel tank cleaning

chemicals, paper towels, rags, and liquid fertilizer. There also have

been data indicating the existence of other contaminants in the fuel

system that, although unidentified, were severe enough to cause engine

power loss. The numerous reports of in-service incidents associated

with gross fuel contamination demonstrate that, despite the many

industry standards intended to maintain cleanliness of the airplane

fuel supply, contamination of airplane fuel systems will likely occur

in the future. In anticipation of this likelihood, the FAA considers

that an immediate indication of impending engine fuel filter bypass

will provide the flight crew with the appropriate information required

to take action before contamination of the fuel system becomes a source

of engine operational problems.

Requests To Change the AFM Revision Requirement

One commenter requests that the proposed AFM revision be changed to

allow the flight crew the option of continuing the flight to the

original destination, without diverting, if the

[[Page 14612]]

``ENG FUEL FILT'' message illuminates during flight and no other engine

parameter fluctuations (i.e., low fuel flow, low fuel pressure, rotor

speed deterioration, etc.) are evident. The commenter considers this

change in the wording to be necessary in order to decrease the

possibility of confusion on the part of the flight crew should a

nuisance message occur (that is, the message actually is false) and the

flight crew risks diverting to an unfamiliar airport.

The FAA does not agree that a change to the AFM revision is

necessary. As worded in the AD, the text of the AFM revision does not

instruct the flight crew to land at the nearest airport. The AFM

revision provides information to the flight crew to indicate that, if

more than one engine's fuel filter message is displayed, the airplane

fuel system may be contaminated and erratic engine operation or engine

flame out may occur. This addresses the possibility of a false

indication on one engine fuel filter. The wording of the AFM revision

addresses only the situation where there are engine fuel filter

messages for more than one engine's fuel filter, and it leaves the

decision on any flight crew action, including diverting to an

alternative airport, up to the flight crew.

One operator requests that paragraphs (a) and (b) of the proposal

be revised to include the AFM revision regarding ``advisory'' level

messages that is currently contained in proposed paragraph (d)(2); and

that proposed paragraph (d)(2) subsequently be deleted. Proposed

paragraphs (a) and (b) would require an AFM revision relative to status

level messages. Paragraph (d)(2) then would require that, concurrent

with the installation of the upgraded EICAS, operators are to remove

the AFM revision required by paragraphs (a) and (b), and to insert a

new AFM revision pertaining to advisory level messages. This operator

has an AFM assigned to each aircraft in its fleet, and believes that it

would be nearly impossible to ensure that the [(paragraph (d)(2)] AFM

revision gets incorporated concurrently with the installation of the

upgraded EICAS computer, since the upgrade could occur at any time on

the flight line. This operator requests that the proposed AD be revised

so that only one AFM revision would be necessary.

The FAA does not concur. The FAA considers that incorporating both

of the proposed AFM revisions at the same time in the same location in

the AFM could cause undue confusion for the flight crew. For example,

on an airplane having the upgraded EICAS computer, if an ``advisory''

level ENG FUEL FILT message appeared on the EICAS display during

flight, and then later the status cue appeared, the flight crew would

look for a ``status'' level ENG FUEL FILT message on the EICAS status

page. No ``status'' level message would be displayed because the EICAS

computer had been updated to display that message only as an

``advisory'' level message. This could lead the flight crew to distrust

the ``advisory'' level message because of the absence of a ``status''

level message. However, if the upgrade of the EICAS computer were

eventually developed so that it can be accomplished using a method that

incorporates both the ``status'' level message and the ``advisory''

level message in the modified computer, and if either level message can

be selected after the computer is installed (i.e., pin selectable),

then operators could modify their entire fleet and change the message

level and AFM wording across their fleet at the same time. This

capability depends on the method that is finally developed by the

manufacturer to incorporate the upgrade of the EICAS computers. The FAA

acknowledges that there may be other situations and other methods that

could be used to achieve the intent of this portion of the AD. For

these cases, paragraph (e) of the final rule provides operators the

opportunity to request the use of alternative methods of compliance.

Requests To Extend the Compliance Time for Modification

Several commenters request that paragraph (d) of the proposed rule

be revised to extend the compliance time for the modification from the

proposed 4 years to as much as 6 years. These commenters state that it

will take approximately 2 years for Boeing and the EICAS computer

manufacturer to define, develop, and release the modified software

necessary to accomplish the change in message level. Some commenters

point out that certain older model EICAS computers will also require

additional hardware modifications before the required modification can

be installed. One operator is concerned that the modification for the

Model 757 will not be available until after the modifications for the

Model 747-400 and 767 are released.

These commenters state that, once the modification is available,

they will require a minimum of an additional 18 months to modify all of

the affected airplanes in their fleets. Further, the proposed

compliance time will likely require that the modification be installed

during special shop visits, instead of during regularly scheduled

maintenance. This would impose an undue financial burden on operators,

and disproportionate manpower constraints on maintenance facilities.

The FAA does not concur with the commenters' request. In developing

an appropriate compliance time, the FAA considered not only the safety

implications, but the time necessary for design of an acceptable

modification, and normal maintenance schedules for timely

accomplishment of the modification. In light of all of these items, as

well as discussions with the manufacturer, the FAA finds that 4 years

provides an acceptable level of safety, and provides sufficient time to

produce the modification as well as install it on the affected fleet

during regular maintenance intervals. However, paragraph (e) of the

final rule does provide affected operators the opportunity to apply for

an adjustment of the compliance time if data are presented to justify

such an adjustment.

Request To Delete the Requirement for Modification

One commenter concurs with the proposed ``interim'' requirement to

revise the AFM to advise the flight crew to respond to the ``status''

level messages. However, this commenter requests that the proposed

requirement for the modification (upgrade) of the EICAS computer be

deleted because an acceptable modification has not yet been designed

and made available. The commenter suggests that the FAA postpone action

on that specific requirement until the modification is developed and an

adequate cost analysis of it can be made.

The FAA does not concur that delaying this AD is warranted. The FAA

maintains that sufficient technology and data exist to enable the

manufacturer(s) to devise, and operators to install, the EICAS upgrade

within the compliance time provided by the AD. Further, the FAA has

determined that an EICAS upgrade (and accompanying AFM revision) to

provide ``advisory'' level messages of an impending engine fuel filter

bypass condition is the most effective way to positively address the

unsafe condition that is the subject of this AD. The FAA considers that

long-term continued operational safety will be better assured by this

design change rather than by only implementing the ``interim'' action

of revising the AFM to advise the flight crew to respond to the

``status'' level messages.

Request To Allow Dispatch With an Inoperative EICAS

Several commenters request that the proposed AD be revised to

include a

[[Page 14613]]

provision to allow dispatch of the airplane with an inoperative EICAS

computer. These commenters point out that the MMEL for the affected

airplanes currently allows dispatch with one EICAS computer removed or

inoperative for one calendar day. An inoperative or removed EICAS

computer would preclude the display of status messages during that

time, which would be contrary to the requirements of the proposed AD.

These commenters are concerned that dispatch capability under the MMEL

will be reduced or restricted as a result of the proposed AD, and this

would have an extensive operational impact on affected operators. The

commenters believe that the risk of a gross fuel contamination event is

so low that the current MMEL dispatch relief should be continued even

though an ``ENG FUEL FILT'' status message is not available.

The FAA does not concur with the commenters' request. The use of

the status message as a method of providing the flight crew with

indication of an impending fuel filter bypass precludes dispatch with

an inoperative EICAS computer. Dispatching an airplane configured so

that the flight crew does not have the ability to check the ``ENG FUEL

FILT'' status display messages only exacerbates the unsafe condition

addressed by this AD. In order to ensure and maintain the ability of

the flight crew to check these messages during flight, the status

display must be operational. After the EICAS computers have been

modified to provide ``advisory'' level messages to the flight crew to

indicate an impending fuel filter bypass condition, dispatch with an

inoperative EICAS computer will again be permitted under the existing

MMEL.

Request for Additional Cost Impact Information

Several commenters consider that the cost impact information

provided by the FAA in the preamble to the notice is inadequate:

1. Certain of these commenters state that preliminary estimates

from industry indicate that the cost to upgrade the EICAS computers

could be between $18 and $25 million for the affected fleet. One of

these commenters requests that the adoption of the final rule be

postponed to permit operators to obtain additional costs data from the

manufacturer.

2. Another commenter states that the cost analysis presented in the

proposal assumes that all operators will upgrade the EICAS computers to

provide for global positioning system (GPS) navigation, and this will

reduce the cost to accomplish the modification to change the ``engine

fuel filter'' message to an advisory level. The commenter contends that

all operators may not incorporate GPS or other EICAS upgrades within

the compliance time proposed, and the cost to an operator who elects

only to change the level of the engine fuel filter message could be as

much as $100,000 per airplane.

3. One commenter states that the proposed requirement to upgrade

the EICAS computer could include additional incidental costs, such as

rewiring and the installation of cockpit annunciator lights. All of

this could cost $10,000 per airplane, in addition to the EICAS upgrade.

4. Another commenter states that, if the upgraded EICAS computers

are not interchangeable with the non-upgraded computers, the increased

cost to maintain a supply of spare EICAS computers of both

configurations should be included in the cost impact of the AD.

5. One commenter requests that, prior to issuing a final rule, the

FAA perform a full cost-benefit analysis of it in accordance with

Executive Order 12866, and that the results of the analysis be

presented in a supplemental notice of this proposed rulemaking.

The FAA acknowledges these commenters' concerns about the cost

impact of this AD action.

As for the cost of the upgraded EICAS computers, the FAA has

attempted to obtain definitive data to verify what the actual cost of

the ultimate modification will be, but it has been unable to do so. The

FAA invited commenters to provide such information, but received what

can only be called ``best guesses'' and no verifiable cost estimates.

Comments are more likely to be persuasive to the extent that they

provide specific and detailed information regarding actual costs. When

commenters submit simple generalizations about the costs, there is

little that the FAA can consider.

The FAA did attempt to estimate the cost of the EICAS upgrade

required by this AD by reviewing the average costs of similar types of

previous modifications of EICAS computers (and other avionics

components) installed on transport category airplanes. The labor and

parts costs for other individual EICAS modifications have proven to be

quite variable, ranging from 1 to 20 work hours for labor and as much

as $46,000 for parts. Because of these variables and because the

manufacturers have not completed development of the EICAS upgrade, the

FAA's attempt to determine a realistic cost estimate has been somewhat

futile. The FAA is continuing to work with the appropriate

manufacturers to establish verifiable costs of labor and parts

associated with the upgrade specifically required by this AD.

Despite the costs associated with the individual EICAS upgrade

required by this AD, the FAA does expect most operators to accomplish

this upgrade at the same time that they accomplish other upgrades to

the EICAS systems on the affected airplanes. The FAA bases this

expectation on discussions it has held with the pertinent manufacturers

and a review of the history of EICAS upgrades. These have led the FAA

to be confident that the cost of modifying the EICAS computers in

accordance with the requirements of this AD will be shared with other

upgrades to the EICAS computers that are planned to be developed and

made available during the 4-year compliance time of this AD. For

example, as indicated in the proposal, the addition of GPS navigation

capability is one modification that is known to require modification of

the EICAS computers, and this modification likely will be introduced

into the entire fleet of airplanes affected by the this AD within the

4-year compliance time.

In fact, the 4-year compliance time was established specifically in

consideration of allowing sufficient time for operators to incorporate

the EICAS upgrade required by this AD at the same time they incorporate

other upgrades to EICAS that will be available. The intent of this was

to enable operators to reduce the costs of fleet downtime, labor, and

parts. This is not to imply that the EICAS upgrade required by this AD

must be incorporated together with any other change to the EICAS.

Rather, it means that cost-conscious operators have the opportunity of

accomplishing several other modifications of the EICAS concurrently

with the upgrade required by this AD, and thereby reduce their affected

fleet's downtime, labor costs, and parts costs.

As for additional incidental costs that would be associated with

the requirements of this AD, the FAA recognizes that, in accomplishing

the requirements of any AD, operators may incur ``incidental'' costs in

addition to the ``direct'' costs of the specific action required by the

AD. However, the cost analysis in AD rulemaking actions typically does

not include incidental costs. Because incidental costs may vary

significantly from operator to operator, they are almost impossible to

calculate.

As for the interchangeability of the upgraded EICAS computer with

the existing computers, the FAA notes that incorporation of previous

modifications of this type into the EICAS system has always provided

for interchangeability with earlier upgrades. The FAA expects

[[Page 14614]]

that the manufacturer of the EICAS computer will design the

modification for the message level change to maintain

interchangeability of units.

As for the request that the FAA conduct a ``full cost-benefit

analysis'' of the proposed AD in accordance with Executive Order 12866,

the FAA points out that it is not required to do a such an analysis for

each AD. In fact, AD's were explicitly exempted from the Office of

Management and Budget (OMB) coordination process described in Section 6

of that Executive Order. Looking at the reasoning behind this, it is

important first to realize that, 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.'' Second, it is

important to understand that, when the FAA later makes a finding of an

unsafe condition in an aircraft and issues an AD, it means that the

original cost-beneficial level of safety established for that aircraft

is no longer being achieved, and that the required AD actions are

necessary in order to restore that level of safety. Because the

original level of safety has already been determined to be cost-

beneficial, and because the AD does not add an additional regulatory

requirement that increases the level of safety beyond what has been

established by the type design, a full cost-benefit analysis for each

AD would be considered redundant and would be unnecessary.

In general, 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 and operate 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 and operating safe aircraft, prudent operators

would accomplish the required actions even if they were not required to

do so by the AD. In any case, the FAA has determined that direct and

incidental costs are still outweighed by the safety benefits of the AD.

Conclusion

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the change previously

described. The FAA has determined that this change will neither

increase the economic burden on any operator nor increase the scope of

the AD.

Cost Impact

There are approximately 1,378 Model 747-400, 757, and 767 series

airplanes of the affected design in the worldwide fleet. The FAA

estimates that 588 airplanes of U.S. registry will be affected by this

proposed AD.

The initial revision to the AFM will take approximately 1 work hour

per airplane to accomplish, at an average labor rate of $60 per work

hour. Based on these figures, the cost impact of this action on U.S.

operators is estimated to be $35,280, or $60 per airplane.

The FAA currently has no specific cost estimates associated with

the installation of upgraded EICAS computers, since the upgrade has not

been developed yet. The FAA has been advised, however, that the

manufacturer is planning other changes to these EICAS computers that

are necessary to provide for GPS navigation capability and other

enhanced features. The compliance time of four years for the EICAS

installation requirements of this AD will allow a portion of the EICAS

computers installed on airplanes affected by this AD to have the

required EICAS message upgrade made concurrently with those other

planned EICAS changes, thereby reducing the costs and scheduling impact

of such changes on operators.

The revision to the AFM that will be required subsequent to the

installation of the upgraded EICAS computers will take approximately 1

work hour per airplane to accomplish, at an average labor rate of $60

per work hour. Based on these figures, the cost impact of this action

on U.S. operators is estimated to be $35,280, or $60 per airplane.

The cost impact figure discussed above is based on assumptions that

no operator has yet accomplished any of the requirements of this AD

action, and that no operator would accomplish those actions in the

future if this AD were not adopted.

Regulatory Impact

The regulations adopted herein will not have substantial direct

effects on the States, on the relationship between the national

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

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) will not have a

significant economic impact, positive or negative, on a substantial

number of small entities under the criteria of the Regulatory

Flexibility Act. A final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from the Rules Docket at the location provided under the caption

``ADDRESSES.''

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends part 39 of

the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

96-07-09 Boeing: Amendment 39-9558. Docket 94-NM-140-AD.

Applicability: All Model 747-400, 757, and 767 series airplanes;

certificated in any category.

Note 1: This AD applies to each airplane identified in the

preceding applicability provision, regardless of whether it has been

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 (e) 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 ensure that the flight crew is appropriately aware of

conditions involving

[[Page 14615]]

a severely contaminated airplane fuel system and the associated

increased potential for engine power loss, accomplish the following:

(a) For all Model 747-400 series airplanes: Within 60 days after

the effective date of this AD, revise the Limitations Section of the

FAA-approved Airplane Flight Manual (AFM) to include the following

statement. This may be accomplished by inserting a copy of this AD

in the AFM.

``Respond to the EICAS STATUS CUE by checking for the following

status level messages(s):

ENG 1 FUEL FILT

ENG 2 FUEL FILT

ENG 3 FUEL FILT

ENG 4 FUEL FILT

If more than one of these impending fuel filter bypass messages

is displayed, airplane fuel system contamination may be present,

which can result in erratic engine operation and engine flameout.

If other status level messages are displayed, the flight crew

may deal with them in accordance with the appropriate operator

procedure.''

(b) For all Model 757 series airplanes, and Model 767 series

airplanes powered by General Electric CF6-80A and CF6-80C2 engines,

Pratt & Whitney PW 4000 engines, and Rolls-Royce RB211-524 engines:

Within 60 days after the effective date of this AD, revise the

Limitations Section of the FAA-approved Airplane Flight Manual (AFM)

to include the following statement. This may be accomplished by

inserting a copy of this AD in the AFM.

``Respond to the EICAS STATUS CUE by checking for the following

status level messages(s):

--R ENG FUEL FILT --

L ENG FUEL FILT

If more than one of these impending fuel filter bypass messages

is displayed, airplane fuel system contamination may be present,

which can result in erratic engine operation and engine flameout.

If other status level messages are displayed, the flight crew

may deal with them in accordance with the appropriate operator

procedure.'' -

(c) For Model 767 series airplanes powered by Pratt & Whitney

JT9D engines: Within 60 days after the effective date of this AD,

revise the Limitations Section of the FAA-approved Airplane Flight

Manual (AFM) to include the following statement. This may be

accomplished by inserting a copy of this AD in the AFM.

``If both of the following EICAS advisory level messages for

impending fuel filter bypass are displayed, and engine fuel icing is

not suspected (based on the fuel temperature being too high or

because engine fuel heat has been selected ``on''), airplane fuel

system contamination may be present, which can result in erratic

engine operation and engine flameout:

--R ENG FUEL FILT --

L ENG FUEL FILT''

-(d) For all Model 747-400 series airplanes; all Model 757

series airplanes; and Model 767 series airplanes powered by General

Electric CF6-80A and CF6-80C2 engines, Pratt & Whitney PW 4000

engines, and Rolls-Royce RB211-524 engines: Accomplish the

requirements of paragraph (d)(1) and (d)(2) of this AD: -

(1) Within 4 years after the effective date of this AD, install

an upgraded engine indication and crew alerting system (EICAS)

computer that will provide ``advisory'' level messages to the flight

crew to indicate an impending engine fuel filter bypass condition

for each engine. The installation shall be accomplished in

accordance with a method approved by the Manager, Seattle Aircraft

Certification Office (ACO), FAA, Transport Airplane Directorate. -

(2) Concurrent with the installation required by paragraph

(d)(1) of this AD, remove the AFM revisions required by paragraphs

(a) and (b) of this AD, and revise the Limitations Section of the

AFM to advise the flight crew that impending engine fuel filter

bypass advisory level messages for multiple engines may indicate

contamination of the airplane fuel system, which can result in

erratic engine operation and engine flameout. The revision to the

Limitations Section must be approved by the Manager, Seattle ACO,

FAA, Transport Airplane Directorate. -

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

compliance time that provides an acceptable level of safety may be

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

Airplane Directorate. Operators shall submit their requests through

an appropriate FAA Principal Operations Inspector, who may add

comments and then send it to the Manager, Seattle ACO.

-Note 2: Information concerning the existence of approved

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

obtained from the Seattle ACO.

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

sections 21.197 and 21.199 of the Federal Aviation Regulations (14

CFR 21.197 and 21.199) to operate the airplane to a location where

the requirements of this AD can be accomplished. -

(g) This amendment becomes effective on May 3, 1996.

Issued in Renton, Washington, on March 27, 1996.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 96-7959 Filed 4-2-96; 8:45 am]

BILLING CODE 4910-13-P