[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]



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

[[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.

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

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 

[[Page 117]]
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 

[[Page 118]]
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 

[[Page 119]]
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 

[[Page 120]]
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