[Federal Register Volume 61, Number 65 (Wednesday, April 3, 1996)]
[Rules and Regulations]
[Pages 14608-14615]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-7959]



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


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