96-7959. Airworthiness Directives; Boeing Model 747-400, 757, and 767 Series Airplanes  

  • [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
    
    

Document Information

Effective Date:
5/3/1996
Published:
04/03/1996
Department:
Transportation Department
Entry Type:
Rule
Action:
Final rule.
Document Number:
96-7959
Dates:
May 3, 1996.
Pages:
14608-14615 (8 pages)
Docket Numbers:
Docket No. 94-NM-140-AD, Amendment 39-9558, AD 96-07-09
PDF File:
96-7959.pdf
CFR: (1)
14 CFR 39.13