96-62. Airworthiness Directives; Boeing Model 747-100 and -200 Series Airplanes  

  • [Federal Register Volume 61, Number 2 (Wednesday, January 3, 1996)]
    [Rules and Regulations]
    [Pages 115-120]
    From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
    [FR Doc No: 96-62]
    
    
    
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    [[Page 116]]
    
    
    
    DEPARTMENT OF TRANSPORTATION
    14 CFR Part 39
    
    [Docket No. 95-NM-193-AD; Amendment 39-9479; AD 96-01-03]
    
    
    Airworthiness Directives; Boeing Model 747-100 and -200 Series 
    Airplanes
    
    AGENCY: Federal Aviation Administration, DOT.
    
    ACTION: Final rule; request for comments.
    
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    SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
    is applicable to certain Boeing Model 747-100 and -200 series 
    airplanes. This action requires a revision of the Airplane Flight 
    Manual (AFM) and of the Airplane Weight and Balance Supplement to 
    restrict the running load and maximum total payload to a suitable 
    level. This amendment is prompted by a determination that these 
    airplanes are incapable of carrying the currently certified payload 
    limits due to the missing external structural doublers located forward 
    of the surround structure of the main deck side cargo door, and 
    deficiencies in the main deck floors. The actions specified in this AD 
    are intended to prevent collapse of the aft fuselage due to inadequate 
    strength in the airplane structure, and subsequent separation of the 
    aft fuselage from the airplane.
    
    DATES: Effective January 30, 1996.
        Comments for inclusion in the Rules Docket must be received on or 
    before March 4, 1996.
    
    ADDRESSES: Submit comments in triplicate to the Federal Aviation 
    Administration (FAA), Transport Airplane Directorate, ANM-103, 
    Attention: Rules Docket No. 95-NM-193-AD, 1601 Lind Avenue, SW., 
    Renton, Washington 98055-4056.
        Information concerning this AD may be examined at the FAA, 
    Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
    Washington.
    
    FOR FURTHER INFORMATION CONTACT: Steven Fox, Aerospace Engineer, 
    Airframe Branch, ANM-120S, Seattle Aircraft Certification Office, FAA, 
    Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
    Washington 98055-4056; telephone (206) 227-2777; fax (206) 227-1181.
    
    SUPPLEMENTARY INFORMATION:
    
    History of Relevant Supplemental Type Certificates (STC)
    
        In 1988, the FAA approved two STC's. The first STC, SA2322SO, 
    modified a Boeing Model 747-100 series airplane from a passenger 
    configuration to a special freighter configuration by adding a main 
    deck side cargo door. In order to install the main deck side cargo 
    door, this modification entailed cutting a 324 square foot hole in the 
    side of the fuselage from body stations 1740 to 1960; however, the STC 
    did not provide for reinforcement of the fuselage skin, forward of the 
    main deck side cargo door. The second STC, SA2323SO, further modified 
    this airplane by adding a cargo floor and changing the associated 
    systems. These modifications were accomplished by the Pemco 
    Corporation. The FAA-approval of these two STC's by the Atlanta 
    Aircraft Certification Office was based on an incorrect finding that 
    the design was identical to the previously FAA-approved modification of 
    the Model 747 special freighter airplanes. Subsequently, these STC's 
    were sold to GATX-Airlog Company, which converted nine more Model 747-
    100 series airplanes from a passenger configuration to a special 
    freighter configuration in accordance with these two STC's.
        In 1994, the GATX-Airlog Company applied for approval of a new STC, 
    SA4227NM-D, to modify a Model 747-200 series airplane from a passenger 
    configuration to a special freighter configuration. The approval of 
    this STC was based on the data that were submitted for the two previous 
    STC's.
        Subsequently, the weight and balance limitations for all three of 
    these STC's were modified by STC SA5199NM (for Model 747-100 series 
    airplanes) and STC SA5759NM (for Model 747-200 series airplanes). These 
    new weight and balance limitations increased the cargo payload for 
    airplanes modified to a special freighter configuration in accordance 
    with the three earlier STC's. The GATX-Airlog Company received approval 
    of these latter two STC's based on the assumption that the data 
    submitted for the three earlier STC's were structurally satisfactory 
    and complied with the applicable regulations.
    
    History of Relevant AD's
    
        On December 27, 1994, the FAA issued AD 95-01-04, amendment 39-9115 
    (60 FR 2005, January 6, 1995), applicable to Model 747-100 series 
    airplanes modified in accordance with STC SA2322SO. That AD requires a 
    one-time detailed visual inspection of the lap joint of stringer 4L 
    from fuselage stations 1660 to 2040 to detect discrepancies (such as 
    corrosion, cracking, open holes, misdrilled holes, and any freeze plugs 
    in the fuselage skin and internal stringer or longerons). That AD also 
    requires that operators submit a report of their findings to the FAA. 
    That AD was prompted by reports of ``hidden'' open fasteners holes in 
    the middle row of the lap joint, as well as misdrilled holes, elongated 
    holes, and ``figure eight'' holes, and short edge margins in the 
    fastener holes of the fuselage skin. These reports were received from 
    operators of Model 747-100 series airplanes that had been modified in 
    accordance with STC SA2322SO. The actions required by AD 95-01-04 are 
    intended to prevent reduced fatigue life of the fuselage in the area in 
    which holes are found.
        In response to the reporting requirement of that AD, the FAA 
    received reports of 216 misdrilled, open, or short-edged margin holes 
    that were filled with random fasteners on a single airplane. The FAA 
    has also learned from these reports that the skin lap splice at 
    stringer 4L has had to be replaced on all of the inspected airplanes 
    because of the severity of the discrepancies found during the 
    inspections required by that AD. Further, another operator reported 
    finding five body frames that did not have inner chord attachments 
    installed above the main deck side cargo door. The FAA has received 
    reports of multiple misdrilled fasteners where the main deck floor 
    beams attach to the existing frame of the airplane, which cause the 
    frames to be extremely susceptible to early fatigue failure. The FAA 
    finds that failure of a single frame would not significantly affect the 
    airplane's fail-safe design; however, misdrilled fasteners were found 
    on both sides of most of the fuselage frames. Because the frames on 
    airplanes that have been converted in accordance with the subject STC's 
    have reduced strength due to numerous misdrilled holes, the FAA has 
    determined that failure of any single frame on these airplanes will 
    result in structurally significant higher loads in the adjacent frames.
        These manufacturing deficiencies have further reduced the 
    structural capability of these airplanes. Because of the variability of 
    the manufacturing defects and the missing structural components, it is 
    impossible for the FAA to determine the extent of the reduction in the 
    structural capability of these airplanes without re-examining each 
    airplane that was reconfigured in accordance with the subject STC's. 
    Since all of the affected airplanes have not yet been inspected in 
    accordance with the requirements of AD 95-01-04, the FAA has not 
    completed a comprehensive review to determine final corrective action. 
    -
        On August 3, 1995, the FAA issued AD 95-15-52, amendment 39-9335 
    (60 FR 40748, August 10, 1995), applicable to Model 747-100 series 
    airplanes 
    
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    modified in accordance with STC SA2322SO, SA2323SO, or SA5199NM; and 
    Model 747-200 series airplanes modified in accordance with STC 
    SA4227NM-D or SA5759NM. That AD requires a revision of the Limitations 
    Section of the FAA-approved Airplane Flight Manual (AFM) and of the 
    Limitations Section of the Airplane Weight and Balance Supplement to 
    restrict cargo loading from fuselage stations 1265 to 1480 
    (approximately 200 inches of the center section of the fuselage). That 
    AD provides for the removal of the restrictions following 
    accomplishment of a modification of the longitudinal floor beams of the 
    affected fuselage stations in accordance with a method approved by the 
    FAA. That action was prompted by a determination that the strength in 
    the floor beams was inadequate between fuselage stations 1265 to 1480. 
    The actions specified in that AD are intended to prevent failure of the 
    longitudinal floor beams in the center section of the fuselage, which 
    may cause the keel beam to fail and result in rupture of the fuselage. 
    (This AD did not address any section of the fuselage other than the 
    center section of the fuselage.) -
        Since the issuance of AD 95-15-52, an operator of Model 747-100 and 
    -200 series airplanes applied for approval of an alternative method of 
    compliance (AMOC) to AD 90-06-06, amendment 39-6490 (55 FR 8374, March 
    7, 1990). AD 90-06-06, which is applicable to certain Boeing Model 747 
    airplanes, requires structural modifications of older airplanes, 
    including a requirement to modify the lower lap joints of the fuselage 
    skin. This operator's airplanes were converted from a passenger 
    configuration to a special freighter configuration in accordance with 
    STC's SA2322SO and SA2323SO (for Model 747-100 series airplanes) and 
    SA4227NM-D (for Model 747-200 series airplanes).
    
    The FAA's Findings -
    
        An FAA review of the data submitted to approve this AMOC, and an 
    FAA evaluation of the health of the affected airplanes based upon the 
    in-service history of the fleet, have led the FAA to make the following 
    findings: Airplanes modified in accordance with all of the STC's 
    discussed above are unsafe, and the FAA approved these STC's in error. 
    Specifically, the FAA has determined that the ultimate strength of the 
    main deck floor and the ultimate strength of the surround structure of 
    the main deck side cargo door are inadequate. -
        The floor system lacks stabilization straps that attach to the main 
    deck floor beam lower chord. These stabilization straps would prevent 
    the floor beam lower chord from buckling under ultimate design load 
    conditions. The floor is structurally inadequate without these straps. 
    The main deck floor beams are capable of sustaining approximately 
    three-fourths of the ultimate gust conditions, and have only a small 
    margin for limit gust conditions. Since the failure mode for these 
    floor beams is column buckling instability, there would be no warning 
    prior to collapse of the main deck floor. Consequently, inspections 
    would be ineffective to detect this failure mode prior to collapse of 
    the floor. Therefore, the only immediate option to prevent collapse of 
    the main deck floor during a gust load condition would be to reduce the 
    weight of the cargo on the main deck of the airplane. -
        Further, the FAA finds that the STC's did not provide needed 
    reinforcement of the fuselage skin, forward of the main deck side cargo 
    door. Such lack of reinforcement results in an unacceptably high 
    concentration of shear and bending stress and the inability to react to 
    various flight maneuver loads. -
        The FAA finds that the non-reinforced fuselage skin is not 
    structurally capable of sustaining flight maneuvers with a 1.5 ultimate 
    safety factor. For example, the 1.5 ultimate safety factor applied to 
    the 2.5g dive maneuver load condition, requires that the airplane be 
    capable of sustaining, without failure, 3.75g ultimate load. These 
    airplanes, when loaded with full cargo (and with a forward center of 
    gravity), can sustain only 55 percent of this 3.75g ultimate flight 
    condition. Analysis of the non-reinforced structure for three other 
    critical load conditions [identified in part 25, ``Airworthiness 
    Standards: Transport Category Airplanes,'' of the Federal Aviation 
    Regulations (14 CFR 25) as abrupt-up elevator, dynamic landing and 
    dynamic lateral gust] yields a similarly low structural capability. -
        The non-reinforced fuselage skin may result in an instability 
    failure that provides no indication of impending failure until the skin 
    and stringers buckle. In the worst case, the aft fuselage may collapse 
    and separate from the airplane. There are no structural inspections 
    that can detect or prevent this type of failure.
    
    In-Service History
    
        In 1991, a Model 747-100 series airplane that had been modified in 
    accordance with these STC's was involved in an incident in which the 
    pilot successfully recovered the airplane from a 3.0g dive maneuver. 
    This airplane had a total payload of 163,800 pounds, which was much 
    less than the maximum allowable payload of 214,300 pounds. The center 
    of gravity (18 percent) was well within the allowable flight manual 
    range of 12 percent (forward limit) to 21 percent (aft limit) for 
    takeoff. The FAA estimates that during this 3.0g maneuver, the airplane 
    loads were only 10 percent less than those that would have caused the 
    fuselage to collapse. The FAA has recently determined by analysis that, 
    if only 6,700 pounds of additional cargo had been loaded in the front 
    portion of the fuselage, the airplane's center of gravity would have 
    shifted forward three percent. The resulting stress levels would exceed 
    the airplane's structural capability, which could lead to separation of 
    the aft fuselage from the airplane. In light of the weight of a Model 
    747 series airplane (738,000 pounds), 6,700 pounds is insignificant and 
    is just 3.1 percent of the the maximum allowable payload (214,300 
    pounds).
        The operators of the 10 affected airplanes have reported four in-
    flight events that have resulted in substantial structural damage to 
    these airplanes, which are among the oldest Model 747 series airplanes 
    in operation (the youngest of which is over 24 years old). In addition 
    to the 3.0g maneuver, discussed above, the FAA has received the 
    following reports:
        1. A report of total engine separation due to intentional departure 
    into known severe turbulence;
        2. A report of uncontained engine failure (more than 180 degrees) 
    that resulted in deformation of the pylon and subsequent damage to the 
    wing and fuselage due to projectile penetrations (survivability of such 
    in-flight damage is dependent upon the integrity of the fuselage 
    structure); and
        3. A report of a severe landing that resulted in a 40-foot by 3-
    foot hole in the aft fuselage.
    
    The FAA's Consideration of All Relevant Factors
    
        Based upon National Aeronautics and Space Administration (NASA) 
    Contractor Report 181909, DOT/FAA-CT-89/36-IV, ``The NASA Digital VGH 
    Program,'' Volume IV, ``B747 Data 1978-1980,'' dated December 1989, the 
    FAA finds that, typically, a Boeing Model 747 series airplane will 
    encounter turbulence or a flight maneuver above 2.0g every 15,000 
    flight hours, which would exceed the structural capability of the 
    affected airplanes if cargo were critically loaded. Therefore, the FAA 
    has determined that another major incident on these affected 
    
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    airplanes is likely to occur in the near future. If the airplane is 
    critically loaded, analysis indicates that the airplane will be unable 
    to sustain ultimate load, and in certain cases limit load.
        The FAA has considered the possibility of requiring modifications 
    to reinforce the subject structure, but finds that they are not 
    feasible at this time because internal loads data were not generated to 
    substantiate the original STC. The lack of internal loads data makes 
    the determination of adequate reinforcement impossible. Therefore, 
    until such data are generated, structural modifications are not a 
    viable option to restore safety to these airplanes.
        The FAA has considered imposing altitude, airspeed, center of 
    gravity, and payload limitations on these airplanes. The FAA finds that 
    a reduction in altitude would have little effect on any of the critical 
    flight conditions since three critical flight conditions (i.e., 2.5g 
    dive maneuver, abrupt-up elevator, and dynamic lateral gust) can occur 
    at any altitude. (The remaining critical flight condition is a landing 
    condition.)
        The FAA finds that a reduction in allowable airspeed would have the 
    greatest effect on the structural loads that result from abrupt-up 
    elevator and lateral gust conditions. However, to provide full 
    structural capability, the airspeed would have to be reduced below the 
    airplane's design maneuver speed (278 knots) to an airspeed close to 
    the flaps-up, stall speed and stick shaker activation speed (215 knots) 
    for these airplanes. Additionally, the critical shear loads resulting 
    from the dynamic landing condition are at approach speeds that cannot 
    be reduced. Therefore, reducing airspeeds would not be a safe option.
        Since the horizontal stabilizer balances loads during flight 
    maneuvers, a limitation of the airplane's center of gravity would have 
    a significant effect in reducing the shear and bending loads on the 
    fuselage that result from the required 3.75g dive maneuvers (which is 
    2.5g multiplied by the required 1.5 safety factor). For example, a 20 
    percent forward center of gravity limitation would yield full 
    structural capability for these airplanes during a 2.5g dive maneuver 
    with a 1.5 ultimate safety factor. This limitation would not require 
    any new payload restrictions for the dive maneuver requirements, but 
    does not solve the negative margins of safety for the other cases.
        The FAA finds that a reduction in payload is the only operational 
    limitation that would have an effect on structural loads that result 
    from dynamic landing, abrupt-up elevator, and gust conditions. Removal 
    of payload aft of the main deck side cargo door (fuselage station 1720) 
    would provide a suffcient reduction in the critical shear and bending 
    loads on the fuselage during these conditions.
    
    Substantiation of the FAA's Findings
    
        The FAA has reviewed data from the following sources to verify its 
    findings of large negative margins of safety.
        1. The FAA has reviewed Hayes International Corporation Engineering 
    Report 8813, ``Structural Substantiation for Main Deck Side Cargo Door 
    Modification Installation and `E' Class Cargo Compartment for the 
    Boeing 747-100 Aircraft,'' dated March 22, 1988. This report documents 
    over 100 findings of negative margins of safety on numerous pages. One 
    such example can be found on page 7.2.127 of this report, which 
    documents many negative margins of safety, one as large as -0.44 at 
    fuselage station 1680 of the floor beam. The report recommends the 
    installation of a reinforcement strap to ensure the structural 
    integrity of the fuselage in this area of the airplane. However, the 
    report does not contain any engineering analysis to determine whether 
    the installation of a reinforcement strap would resolve the negative 
    margins of safety. The FAA inspected one airplane and determined that 
    some of the reinforcement straps were not installed on the fuselage 
    foward of the main deck floor. The FAA used the Hayes International 
    Report 8813 internal loads data for the main deck floor and conducted 
    an analysis that verified the negative margins of safety documented in 
    the report. The report contains no analysis or internal loads data for 
    the missing structural doublers forward of the main deck side cargo 
    door cutout.-
        2. The FAA has reviewed data submitted by Elsinore Aerospace 
    Services, on behalf of the GATX-Airlog Company, to the FAA for approval 
    of a modification that converts Model 747 combi airplanes to a special 
    freighter configuration. The design and data submitted for the forward 
    fuselage were identical to the design and data submitted for the 
    subject STC's. The Elsinore data confirmed the FAA's findings of 
    negative margins of safety in the existing main deck floor. Elsinore 
    Aerospace Services, together with the FAA, identified design 
    deficiencies of the main deck floor and developed corrective measures 
    for combi airplanes to meet the minimum level of safety required by 
    part 25 of the Federal Aviation Regulation (14 CFR 25). However, 
    similar corrective measures have not yet been developed for the Model 
    747-100 and -200 series airplanes. -
        3. The FAA has reviewed Boeing Commercial Airplane Group data that 
    were used to convert Model 747 series airplanes from a passenger 
    configuration to a special freighter configuration in accordance with a 
    design developed by Boeing. The FAA Designated Engineering 
    Representatives (DER) at the Boeing Commercial Airplane Group verified 
    that large negative margins of safety would exist on airplanes modified 
    in accordance with its design if the external skin doublers at the 
    cargo door were not installed. The FAA reviewed and concurred with this 
    analysis, and concluded that because of the similarity of the Boeing 
    design (having the doublers removed) with the GATX design, the GATX 
    design would have similar negative margins of safety of approximately 
    -0.45 for the non-reinforced fuselage forward of the main deck side 
    cargo door. -
        4. The FAA has conferred with the FAA DER's at the GATX-Airlog 
    Company working on location at the Israel Aircraft Industries (IAI). 
    These DER's are currently analyzing the design of the GATX-Airlog 
    Company modification of the forward main deck side cargo door. Although 
    the IAI report has not yet been submitted in final form to GATX, 
    preliminary data reviewed by the DER's, on behalf of the FAA, indicate 
    that large negative margins of safety exist forward of the main deck 
    side cargo door, similar to those obtained in the Boeing and FAA 
    analysis. -
        5. On December 20, 1995, the FAA held a meeting/telecon with 
    operators and interested parties to gather more data. However, no data 
    were presented to refute the FAA's findings of multiple unsafe 
    conditions that were substantiated by all of the sources of data, 
    discussed above. At this meeting, a consultant for the GATX-Airlog 
    Company presented data (derived from the 3.0g dive maneuver incident) 
    to demonstrate that the affected airplanes are capable of withstanding 
    structural loads in the cargo door surround structure in excess of the 
    payload restriction required by this AD. The FAA finds that this data 
    for applied vertical loads (by far the largest component in determining 
    margins of safety) are essentially the same as those determined by the 
    FAA analysis, and confirms the FAA's findings of unsafe conditions. -
        This consultant's data did raise one issue that had not been 
    considered by the FAA prior to the December 20, 1995, meeting. The 
    consultant suggested that the data showed the possibility of 
    
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    additional small lateral compression stresses resulting from minor 
    lateral loads having occurred during the 3.0g dive maneuver, thereby 
    indicating that the cargo door surround structure might be slightly 
    stronger than that previously determined by the FAA. The data to 
    support this conclusion had not been fully evaluated by either the 
    consultant or the FAA and estimates of increments of strength cannot be 
    definitively verified. The estimates for the loads in the analysis were 
    extrapolated from the airplane's flight data recorder and the actual 
    fuselage loads of the airplane during the 3.0g dive maneuver and the 
    resulting stresses on the cargo door surround structure have not been 
    demonstrated by instrumentation and tests. Without such tests, any 
    conclusion regarding the strength of the structure would be 
    speculative. The FAA's determinations of the unsafe conditions and 
    proposed operational limitations are based on reliable analysis 
    techniques and extensive instrumented testing of the Model 747 series 
    airplane by the Boeing Commercial Airplane Group. -
        At the meeting, GATX-Airlog Company requested that the FAA delay 
    issuance of this rulemaking action until all data have been finalized 
    and a corrective modification has been designed, developed, and 
    approved. The FAA has determined that delaying this AD action would be 
    inappropriate since multiple unsafe conditions exist and the large 
    negative margins of safety present an unacceptable risk. Therefore, the 
    FAA has concluded that the level of risk associated with these unsafe 
    conditions, including the potential for total loss of the aircraft, is 
    so great that a delay cannot be justified. Furthermore, a delay in 
    issuance of this AD action would be contrary to the interest of public 
    safety, since the nature of the unsafe conditions is such that failure 
    cannot be predicted. Failure under the currently authorized operating 
    conditions is predicated upon the occurrence of uncontrollable factors 
    such as wind gusts, maneuver loads, and hard landings.
    
    Requirements of This AD
    
        Consequently, the FAA has determined that a combination of 
    operational payload limitations must be imposed to reduce the shear and 
    bending loads forward of the main deck side cargo door. A 20 percent 
    forward center of gravity limitation, together with the removal of all 
    payload aft of fuselage station 1720 will reduce both the shear and 
    bending loads on the fuselage during all critical flight conditions. 
    These limitations still allow operation of the airplane with a center 
    of gravity between 20 percent and 33 percent (with full flight range 
    capability).
        Since an unsafe condition has been identified that is likely to 
    exist or develop on other airplanes having these STC's as part of their 
    type design, this AD is being issued to prevent structural collapse and 
    subsequent separation of the aft fuselage from the airplane. This AD 
    requires a revision to the Limitations Section of the FAA-approved AFM 
    and the Limitations Section of the Airplane Weight and Balance 
    Supplement to restrict the running load (which is the maximum allowable 
    linear load per inch), maximum total payload, and center of gravity 
    limits.
        This AD also provides for the removal of these restrictions 
    following accomplishment of a modification of the airplane structure 
    that corrects all structural deficiencies that restores the airplane to 
    meet or exceed the requirements of part 25 of the Federal Aviation 
    Regulations (14 CFR 25) in accordance with a method that is approved by 
    the Manager of the Seattle Aircraft Certification Office.
        This AD's restrictions are in addition to, not in lieu of, the 
    restriction imposed by AD 95-15-52. Therefore, the revision to the 
    Limitations Section of the AFM and the Airplane Weight and Balance 
    Supplement required by this AD, does not supersede the revision 
    required by AD 95-15-52. Further, modifications approved as terminating 
    action for the restriction required by AD 95-15-52, amendment 39-9335, 
    are not considered to be approved as terminating action for the 
    restrictions required by this AD.
        The load level established by this AD is based upon an FAA 
    evaluation of the maximum payload that these airplanes are capable of 
    carrying without external structural doublers installed and without 
    correction of inadequacies in the main deck floor. The FAA has 
    determined that the restrictions imposed by this AD will provide a 
    sufficient level of safety for airplanes on which the external doublers 
    are missing and structural inadequacies of the main deck floor and 
    manufacturing deficiencies exist.
    
    Impact of the Limitations Imposed by the AD
    
        The FAA is aware that the operational limitations imposed by this 
    AD may severely impact the economic viability of the operators of these 
    modified airplanes. In effect, the AD would limit total payload to 
    120,000 pounds from a maximum of 220,000 pounds. This may result in the 
    operators' inability to operate economically because operators may be 
    unable to obtain contracts that guarantee payload capabilities of 
    200,000 pounds. The average payload per flight is approximately 150,000 
    pounds, and operators may be unable to complete heavy-loaded segments 
    of multiple-stop flights. These limits occur because the AD specifies 
    that nothing is to be carried between body stations 1720 and 2360 for 
    both the main deck and lower deck cargo areas and operation is 
    prohibited forward of 20 percent center of gravity. Nonetheless, the 
    FAA must impose these restrictions to ensure continued operational 
    safety of these airplanes.
        The FAA further acknowledges that these restrictions may be 
    conservative. However, an alternative solution to this complex matter--
    one which will ensure the safety of these airplanes and the 
    flightcrews--has not yet been developed. Operators should note that 
    other operational limitations data may be submitted to the FAA for 
    approval under the alternative methods of compliance provision of 
    paragraph (c) of the AD.
        In a meeting on December 27, 1995, the operators asked that the 
    effective date of the AD be delayed until corrective measures can be 
    developed. The operators also indicated that they would be removing the 
    10 affected airplanes from service no later than January 31, 1996. The 
    effective date of this AD is January 30, 1996, with a compliance time 
    of 48 hours for implementing the AD. As a result of the operators' 
    commitment, the aircraft will be out of service pending repairs before 
    the expiration of the compliance time.
        The FAA intends to investigate other types of loading conditions to 
    determine whether additional operational limitations must be imposed to 
    address the structural inadequacies of the main deck floor and other 
    areas that have not yet been identified. If, after review of such data, 
    the FAA determines that the data indicate that further restrictions are 
    necessary, the FAA may consider further rulemaking to implement 
    appropriate corrective action.
        Since a situation exists that requires the immediate adoption of 
    this regulation, it is found that notice and opportunity for prior 
    public comment hereon are impracticable, and that good cause exists for 
    making this amendment effective in less than 30 days.
    
    Comments Invited
    
        Although this action is in the form of a final rule that involves 
    requirements affecting flight safety and, thus, was not preceded by 
    notice and an opportunity for public comment, comments are invited on 
    this rule. Interested persons 
    
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    are invited to comment on this rule by submitting such written data, 
    views, or arguments as they may desire. Communications shall identify 
    the Rules Docket number and be submitted in triplicate to the address 
    specified under the caption ADDRESSES. All communications received on 
    or before the closing date for comments will be considered, and this 
    rule may be amended in light of the comments received. Factual 
    information that supports the commenter's ideas and suggestions is 
    extremely helpful in evaluating the effectiveness of the AD action and 
    determining whether additional rulemaking action would be needed.
        Comments are specifically invited on the overall regulatory, 
    economic, environmental, and energy aspects of the rule that might 
    suggest a need to modify the rule. All comments submitted will be 
    available, both before and after the closing date for comments, in the 
    Rules Docket for examination by interested persons. A report that 
    summarizes each FAA-public contact concerned with the substance of this 
    AD will be filed in the Rules Docket.
        Commenters wishing the FAA to acknowledge receipt of their comments 
    submitted in response to this rule must submit a self-addressed, 
    stamped postcard on which the following statement is made: ``Comments 
    to Docket Number 95-NM-193-AD.'' The postcard will be date stamped and 
    returned to the commenter.
    
    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.
        The FAA has determined that this regulation is an emergency 
    regulation that must be issued immediately to correct an unsafe 
    condition in aircraft, and that it is not a ``significant regulatory 
    action'' under Executive Order 12866. It has been determined further 
    that this action involves an emergency regulation under DOT Regulatory 
    Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
    determined that this emergency regulation otherwise would be 
    significant under DOT Regulatory Policies and Procedures, a final 
    regulatory evaluation will be prepared and placed in the Rules Docket. 
    A copy of it, if filed, 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 USC 106(g), 40101, 40113, 44701.
    
    
    Sec. 39.13  [Amended]
    
        2. Section 39.13 is amended by adding the following new 
    airworthiness directive:
    
    96-01-03  Boeing: Amendment 39-9479. Docket 95-NM-193-AD.
    
        Applicability: Model 747-100 series airplanes modified in 
    accordance with Supplemental Type Certificate (STC) SA2322SO, 
    SA2323SO, or SA5199NM; and Model 747-200 series airplanes modified 
    in accordance with STC SA4227NM-D or SA5759NM; certificated in any 
    category.
    
        Note 1: This AD applies to each airplane identified in the 
    preceding applicability provision, regardless of whether it has been 
    otherwise 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 use the authority 
    provided in paragraph (c) of this AD to request approval from the 
    FAA. This approval may address either no action, if the current 
    configuration eliminates the unsafe condition; or different actions 
    necessary to address the unsafe condition described in this AD. Such 
    a request should include an assessment of the effect of the changed 
    configuration on the unsafe condition addressed by this AD. In no 
    case does the presence of any modification, alteration, or repair 
    remove any airplane from the applicability of this AD.
    
        Compliance: Required as indicated, unless accomplished 
    previously.
        To prevent structural collapse and subsequent separation of the 
    aft fuselage from the airplane, accomplish the following:
        (a) Within 48 clock hours (not flight hours) after this AD 
    becomes effective, revise the Limitations Section of the FAA-
    approved Airplane Flight Manual (AFM) and the Limitations Section of 
    the Airplane Weight and Balance Supplement to include the following 
    information. This may be accomplished by inserting a copy of this AD 
    in the AFM and the Airplane Weight and Balance Supplement.
        ``PAYLOAD LIMITATIONS:
        Do not exceed 0.00 pounds/inch running load between body 
    stations 1720 and 2360. The maximum total payload between body 
    stations 1720 and 2360 shall not exceed 0.00 pounds for both main 
    deck and lower deck cargo.
        The currently certified center of gravity limitations defined in 
    STC's SA2322SO, SA2323SO, and SA5199NM (for Model 747-100 series 
    airplanes) and STC's SA4227NM-D and SA5759NM (for Model 747-200 
    series airplanes) shall be limited to prohibit operation forward of 
    20 percent center of gravity.''
        (b) Accomplishment of a modification of the airplane structure 
    in accordance with a method approved by the Manager, Seattle 
    Aircraft Certification Office (ACO), FAA, Transport Airplane 
    Directorate, constitutes terminating action for the limitation 
    requirements of paragraph (a) of this AD. The AFM limitation and the 
    Weight and Balance Supplement limitation may be removed following 
    accomplishment of such a modification.
        (c) 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. Operators shall submit 
    their requests through an appropriate FAA Principal Maintenance 
    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.
    
        (e) 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.
        (f) This amendment becomes effective on January 30, 1996.
    
        Issued in Renton, Washington, on December 27, 1995.
    Darrell M. Pederson,
    Acting Manager, Transport Airplane Directorate, Aircraft Certification 
    Service.
    [FR Doc. 96-62 Filed 1-2-96; 8:45 am]
    BILLING CODE 4910-13-U
    
    

Document Information

Effective Date:
1/30/1996
Published:
01/03/1996
Department:
Transportation Department
Entry Type:
Rule
Action:
Final rule; request for comments.
Document Number:
96-62
Dates:
Effective January 30, 1996.
Pages:
115-120 (6 pages)
Docket Numbers:
Docket No. 95-NM-193-AD, Amendment 39-9479, AD 96-01-03
PDF File:
96-62.pdf
CFR: (1)
14 CFR 39.13