[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]
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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.
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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