[Federal Register Volume 65, Number 188 (Wednesday, September 27, 2000)]
[Proposed Rules]
[Pages 58197-58203]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-24747]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-282-AD]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model DC-8 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain McDonnell Douglas Model 
DC-8 series airplanes that have been converted from a passenger- to a 
cargo-carrying (``freighter'') configuration. This proposal would 
require, among other actions, modification of the main deck cargo door 
structure and fuselage structure; modification of a main deck cargo 
door hinge; modification of the main deck cargo floor; and installation 
of a main deck cargo 9g crash barrier. These actions are necessary to 
prevent opening of the cargo door while the airplane is in flight or 
collapse of the main deck cargo floor, and consequent rapid 
decompression of the airplane including possible loss of flight control 
or severe structural damage. These actions are intended to address the 
identified unsafe condition.

DATES: Comments must be received by November 13, 2000.

[[Page 58198]]


ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-282-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-282-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    Information pertaining to this NPRM may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; or at the FAA, Los Angeles Aircraft Certification Office, 
3960 Paramount Boulevard, Lakewood, California.

FOR FURTHER INFORMATION CONTACT: Michael E. O'Neil, Aerospace Engineer, 
Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification 
Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; 
telephone (562) 627-5320; fax (562) 627-5210.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-282-AD.'' The postcard will be date stamped 
and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this notice of proposed rulemaking 
(NPRM) by submitting a request to the FAA, Transport Airplane 
Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-282-AD, 1601 
Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

    Supplemental Type Certificate (STC) SA1832SO (originally issued to 
Monarch, Inc. and currently held by National Aircraft Services, Inc. 
(NASI)) specifies a design for installation of a main deck cargo door, 
associated door cutout in the fuselage, door hydraulic and indication 
systems, Class E compartment with a 9g crash barrier, and cargo 
handling system on McDonnell Douglas Model DC-8 series airplanes. The 
FAA has conducted a design review of Model DC-8 series airplanes 
modified in accordance with STC SA1832SO and has conducted discussions 
regarding the design with the STC holder. From the design review and 
these discussions, the FAA has identified several potential unsafe 
conditions. (Results of this design review are contained in ``DC-8 
Cargo Modification Review Team Review of Monarch (ATAZ) Supplemental 
Type Certificate SA1832SO--Installation of a Cargo Door and Interior, 
Final Report, dated August 3, 1999,'' hereinafter referred to as ``the 
Design Review Report,'' which is included in the Rules Docket for this 
NPRM.)
    On April 24, 2000, the FAA issued airworthiness directive (AD) 
2000-09-02, amendment 39-11710 (65 FR 25437, May 2, 2000), which 
identifies corrective action for the unsafe conditions that relate to 
the hydraulic and indication systems of the main deck cargo door and 
provides for a means to prevent pressurization to an unsafe level if 
the main deck cargo door is not closed, latched, and locked.
    In the preamble of the NPRM for AD 2000-09-02, the FAA indicated 
that further rulemaking action was being considered to address the 
potential unsafe conditions on Model DC-8 series airplanes modified in 
accordance with STC SA1832SO that relate to the unreinforced main deck 
floor, main deck cargo door hinge, fuselage structure in the area 
modified by installation of a main deck cargo door, 9g crash barrier, 
and fire/smoke detection system. The FAA now has determined that 
further rulemaking action is indeed necessary, and this NPRM follows 
from that determination.

Other Related Rulemaking

    The FAA is considering further rulemaking to address the remaining 
potential unsafe condition that relates to the fire/smoke detection 
system.

Cargo Modification Concerns

    In early 1989, two transport airplane accidents were attributed to 
cargo doors coming open during flight. The first accident involved a 
Boeing Model 747 series airplane in which the cargo door separated from 
the airplane, and damaged the fuselage structure, engines, and 
passenger cabin. The second accident involved a McDonnell Douglas Model 
DC-9 series airplane in which the cargo door opened but did not 
separate from its hinge. The open door disturbed the airflow over the 
empennage, which resulted in loss of flight control and consequent loss 
of the airplane. Although cargo doors have opened occasionally without 
mishap shortly after the airplane was in flight, these two accidents 
served to highlight the extreme potential dangers associated with the 
opening of a cargo door while the airplane is in flight.
    As a result of these cargo door opening accidents, the Air 
Transport Association (ATA) of America formed a task force, including 
representatives of the FAA, to review the design, manufacture, 
maintenance, and operation of airplanes fitted with outward opening 
cargo doors, and to make recommendations to prevent inadvertent cargo 
door openings while the airplane is in flight. A design working group 
was tasked with reviewing 14 Code of Federal Regulations (CFR) part 
25.783 [and its accompanying Advisory Circular (AC) 25.783-1, dated 
December 10, 1986] with the intent of clarifying its contents and 
recommending revisions to enhance future cargo door designs. This 
design group also was tasked with providing specific recommendations 
regarding

[[Page 58199]]

design criteria to be applied to existing outward opening cargo doors 
to ensure that inadvertent openings would not occur in the current 
transport category fleet of airplanes.
    The ATA task force made its recommendations in the ``ATA Cargo Door 
Task Force Final Report,'' dated May 15, 1991 (hereinafter referred to 
as ``the ATA Final Report''). On March 20, 1992, the FAA acknowledged 
the ATA's recommendations and issued an FAA memorandum (hereinafter 
referred to as ``the FAA Memorandum'') providing additional guidance 
for purposes of assessing the continuing airworthiness of existing 
designs of outward opening doors. The FAA Memorandum was not intended 
to upgrade the certification basis of the various airplanes, but rather 
to identify criteria to evaluate potential unsafe conditions identified 
on in-service airplanes.
    Utilizing the applicable requirements of Civil Air Regulations 
(CAR) part 4b and the design criteria provided by the FAA Memorandum, 
the FAA has reviewed the original type design of major transport 
airplanes, including McDonnell Douglas Model DC-8 series airplanes 
equipped with outward opening doors, for any design deficiency or 
service difficulty. Based on that review, the FAA identified unsafe 
conditions and issued, among others, the following AD's:
     For certain McDonnell Douglas Model DC-9 series airplanes: 
AD 89-11-02, amendment 39-6216 (54 FR 21416, May 18, 1989);
     For all Boeing Model 747 series airplanes: AD 90-09-06, 
amendment 39-6581 (55 FR 15217, April 23, 1990);
     For certain McDonnell Douglas Model DC-8 series airplanes: 
AD 89-17-01 R1, amendment 39-6521 (55 FR 8446, March 8, 1990);
     For certain Boeing Model 747-100 and -200 series 
airplanes: AD 96-01-51, amendment 39-9492 (61 FR 1703, January 23, 
1996);
     For certain Boeing Model 727-100 and -200 series 
airplanes: AD 96-16-08, amendment 39-9708 (61 FR 41733, August 12, 
1996); and
     For certain McDonnell Douglas Model DC-8 series airplanes: 
AD 2000-09-02, amendment 39-11710 (65 FR 25437, May 2, 2000).

FAA/Industry Collaborative Effort

    In late 1997, the FAA informed the STC holders and operators of 
Model DC-8 series airplanes that it was embarking on a review of Model 
DC-8 series airplanes that have been converted from a passenger- to a 
cargo-carrying (``freighter'') configuration by STC. The FAA proposed 
at a subsequent industry sponsored meeting in early 1998, that DC-8 
operators and STC holders work together to identify and address 
potential safety concerns. This suggestion to the affected industry 
resulted in the creation of the DC-8 Cargo Conversion Joint Task Force 
(JTF) (hereinafter referred to as ``the JTF'').
    The current composition of the JTF includes holders of each of the 
six STC's that address the installation of a main deck cargo door in 
Model DC-8 series airplanes and operators and lessors of those modified 
airplanes. At the JTF's request, the FAA participates in its meetings 
to offer counsel and guidance with respect to the FAA's regulatory 
processes. The JTF is a clearinghouse for the gathering and sharing of 
information among the parties affected by the FAA review of STC cargo 
conversions of Model DC-8 series airplanes. The JTF also is a liaison 
between the FAA, operators, and STC holders.
    The JTF has been working with the FAA to provide data relating to 
the number of STC-modified Model DC-8 series airplanes and operators of 
those airplanes, and identified which airplanes are modified by each 
STC. It also was instrumental in polling the operators and providing 
maintenance schedules and locations to the FAA, which helped the FAA 
arrange visits to operators of airplanes modified by each of the STC's. 
These visits allowed the FAA to review both the available data 
supporting each STC and modified airplanes and to identify potential 
safety concerns with each of the STC modifications. Additionally, the 
JTF has coordinated funding of the industry review of the data 
supporting the STC's and ongoing efforts to resolve safety issues 
identified by the FAA.

Identification of Unsafe Conditions

    Using the certification basis of the airplane (i.e., CAR part 4b), 
the FAA, in collaboration with the JTF, conducted an engineering design 
review, inspected an airplane modified in accordance with STC SA1832SO, 
and identified a number of design features of this STC that are unsafe. 
The FAA considers the following four specific design deficiencies to be 
unsafe:

1. Main Deck Cargo Door and Associated Fuselage Structure

    The FAA, in collaboration with structural engineering 
representatives of the JTF, has identified several areas of the main 
deck cargo door and door jamb structure of STC SA1832SO that require 
modification to meet type design requirements. These areas include the 
addition of structural elements to augment and, in some places, to add 
the structural capability necessary to safely support design loads. 
When taken individually, these areas do not necessarily represent an 
unsafe condition. However, the critical load condition for each of the 
elements is the same, so that all of the elements could fail at the 
same time. Therefore, the FAA has determined that the potential of 
concurrent failure of several structural elements presents an unsafe 
condition for the airplane, and that these elements require 
modification to ensure the safety of the airplane. The modifications 
include:
     Reinforcement of the fuselage door jamb element at the 
main deck cargo door sill;
     Reinforcement of the inner cap of the frame at fuselage 
station (FS) 1700;
     Reinforcement of the lower frame inner cap below the 
strut;
     Replacement of the strut to frame fasteners in the door 
region;
     Reinforcement of the floor beam to frame attachment;
     Replacement of some of the latch mechanism bolts with 
increased strength bolts;
     Replacement of the existing bolts that attach the latches 
to the door with increased strength bolts; and
     Reinforcement of the main deck cargo door frames that 
support the two latches at either end of the main deck cargo door.
    As part of its continuing work to maintain the structural integrity 
of older transport category airplanes, in the early 1980's, the FAA 
concluded that the incidence of fatigue cracking may increase as these 
airplanes continue in service. In light of this, and as a result of 
increased utilization, longer operational lives, and the levels of 
safety expected of the currently operated transport category airplanes, 
the FAA has determined that a damage tolerance assessment of the 
structural modifications associated with STC SA1832SO is necessary to 
ensure the structural integrity for all airplanes in the affected 
fleet. This damage tolerance assessment is to identify any principal 
structural elements (PSE), including the associated inspection 
threshold, inspection method, and repetitive inspection interval, to 
ensure continued operational safety of the airplane. The PSE 
information must be identified in any method of compliance presented to 
address the requirements of the proposed AD.

2. Main Deck Cargo Door Hinge

    In order to avoid catastrophic structural failure of outward 
opening cargo doors, a typical industry approach has been to design 
them and their

[[Page 58200]]

attaching structure to be fail safe (i.e., designed so that if a single 
structural element fails, other structural elements are able to carry 
the redistributed load).
    Structural elements, such as the main deck cargo door hinge, are 
subject to severe in-service operating conditions that could result in 
corrosion, binding, or seizure of the hinge. These conditions, in 
addition to the normal operational loads, can lead to early and 
unpredictable fatigue cracking. If a main deck cargo door hinge is not 
a fail-safe design, a fatigue crack could initiate and propagate 
undetected longitudinally along the length of the hinge, which could 
lead to a complete hinge failure. A possible consequence of this 
undetected failure is the opening of the main deck cargo door while the 
airplane is in flight. Service experience indicates that the opening of 
a cargo door while the airplane is in flight can be extremely hazardous 
in a variety of ways including possible loss of flight control, severe 
structural damage, or rapid decompression, any of which could lead to 
loss of the airplane.
    The design of the main deck cargo door hinge for STC SA1832SO must 
be in compliance with CAR part 4b, including CAR part 4b.270, which 
requires, in part, that catastrophic failure or excessive structural 
deformation, which could adversely affect the flight characteristics of 
the airplane, is not probable after fatigue failure or obvious partial 
failure of a single critical structural element. One common feature of 
a fail-safe hinge design is a division of the hinge into multiple 
segments such that, following failure of any one segment, the remaining 
segments would support the redistributed load.
    The main deck cargo door installed in accordance with STC SA1832SO 
is supported by latches along the bottom of the door and a two-segment 
hinge along the top. This two-segment hinge is considered a critical 
structural element for this STC. A crack that initiates and propagates 
longitudinally along either segment of the hinge will eventually result 
in failure of the entire hinge, because the remaining segment of the 
hinge is unable to support the redistributed loads. Failure of the 
entire hinge can result in the opening of the main deck cargo door 
while the airplane is in flight.
    Therefore, the FAA has determined that detailed visual inspections 
to detect cracks or other discrepancies of the exposed surfaces of the 
main deck cargo door hinge is necessary to ensure that the affected 
airplanes are not in immediate risk of hinge failure and to ensure the 
integrity of the door and fuselage structure to which the hinge is 
attached. Also, the end of the existing aluminum hinge elements of the 
main deck cargo door must be replaced with steel hinge elements on both 
the fuselage and door sides of the hinge, and the hinge must comply 
with the applicable requirements of CAR part 4b, including fail-safe 
requirements.

3. Capability of the Unmodified Floor

    Based on the results of the FAA's and JTF's structural evaluation 
of the main deck cargo floor, the FAA has determined that the 
unmodified main deck cargo floor is not capable of safely supporting 
the main deck zone loading (cargo weight) currently allowed by STC 
SA1832SO. There are several methods to address the unsafe condition. 
The floor beams and their attachment to the fuselage frames and struts, 
which support the floor beams on either side of the fuselage, could be 
modified to support the currently acceptable main deck zone loading. It 
is also possible to limit the main deck zone loading to a level that 
the main deck cargo floor can be supported safely without modification. 
A further possibility is to modify the main deck cargo floor beams to a 
configuration compatible with the desired level of zone loading.
    In assessing the load carrying capability of the main deck cargo 
floor for STC SA1832SO, the manner in which the load is applied to the 
floor, as well as the magnitude of that load, must be considered. For 
example, it is possible to directly place the cargo onto the floor and 
secure it to the floor in a safe manner. However, most operators 
utilize a cargo handling system installed in the airplane that allows 
the use of unit load devices (ULD), such as pallets and containers. 
Together, the cargo handling system and ULD's expedite loading and 
unloading of the airplanes. Technical Standard Order (TSO) TSO-C90c, 
dated April 3, 1992, identifies both the ultimate loads that the ULD's 
produced under the TSO must support, and the number and location of 
restraints necessary to carry those loads. The TSO requires 
identification of the type and size of the ULD's. Although this TSO is 
the most common method of approval for ULD's, it is not the only means 
of approving ULD's. ULD designs also may be approved as part of a type 
certificate or STC. Therefore, the total cargo weight, distribution of 
cargo weight in the airplane, and restraint requirements for ULD's must 
be identified in any method of compliance presented to address the 
requirements of the proposed AD.
    During evaluations of Model 727 and DC-8 series airplanes converted 
to a freighter configuration by STC, the FAA found instances where the 
existing venting capability of certain airplanes had been compromised 
by installation of the Class E compartment. In some cases, the vent 
area was decreased or restricted during modification. The FAA also 
found that the available design data for the main deck cargo floor for 
STC SA1832SO do not demonstrate the adequacy of the venting system of 
the modified DC-8 airplanes. The FAA is concerned about the venting 
between the main cabin floor and the baggage compartments below the 
main deck cargo floor in the event of a rapid decompression. If the 
vent area of the original type design has been decreased or restricted 
during modification, the loads on the main deck cargo floor may be 
increased to an unsafe level during a rapid decompression event. The 
increased loads on the main deck cargo floor could lead to collapse of 
the floor beams. Collapse of the main deck cargo floor could restrict 
the motion of the flight and engine control cables routed through the 
floor beams or could cause the failure of those cables, which could 
result in reduced controllability of the airplane or loss of control. 
Rapid decompression of the airplane could result from a sufficiently 
large failure in the fuselage pressure boundary either above or below 
the main deck cargo floor, such as inadvertent opening of the cargo 
door.
    Therefore, the FAA has determined that an inspection and evaluation 
of the affected floor structure must be accomplished to ensure that the 
venting capability of the passenger configuration has not been 
compromised by installation of the Class E compartment. If the current 
venting capability of the affected floor is less than that of the 
passenger configuration, it must be modified to limit decompression 
loads to a level that can be supported successfully by the existing 
floor structure.

4. 9g Crash Barrier

    In order to ensure the safety of occupants during emergency landing 
conditions, the FAA first established in 1934 a set of inertia load 
factors used to design the structure for restraining items of mass in 
the fuselage. Because the airplane landing speeds have increased over 
the years as the fleet has transitioned from propeller to jet design, 
inertia load factors were changed as specified in CAR part 4b.260. 
Experience has shown that an airplane designed to this regulation has a 
reasonable probability of protecting its occupants from serious injury 
in an emergency landing. The DC-8 passenger

[[Page 58201]]

airplane was designed to these criteria that specified an ultimate 
inertia load requirement of 9g in the forward direction. These criteria 
were applied to the seats and structure restraining the occupants, 
including the flight crew, as well as other items of mass in the 
fuselage.
    When a Model DC-8 series airplane is converted from a passenger- to 
a cargo-carrying (``freighter'') configuration, a 9g crash barrier is 
required, since most cargo containers and container-to-floor attaching 
devices are not designed to withstand emergency landing loads. In fact, 
the FAA estimates that the container-to-floor attaching devices will 
only support approximately 1.5g's to 3g's in the forward direction. 
Without a 9g crash barrier, it is probable that the loads associated 
with an emergency landing would cause the cargo to become unrestrained 
and impact the occupants of the airplane, which could result in serious 
injury to the occupants.
    The structural inadequacy of the 9g crash barrier was evident to 
the FAA during its review in October 1998 of a McDonnell Douglas Model 
DC-8 modified in accordance with STC SA1832SO. The observations 
revealed that the design of the crash barrier floor attachment and 
circumferential supporting structure neither provide adequate strength 
to withstand the 9g forward inertia load generated by the main deck 
cargo mass, nor provide a load path to effectively transfer the loads 
from the crash barrier to the fuselage structure of the airplane.
    Therefore, the FAA has determined that installation of a 9g crash 
barrier that complies with the applicable requirements of CAR part 4b 
is necessary to prevent serious injury to occupants of the airplane.

Development of Engineering Data

    The FAA is aware that the JTF is currently sponsoring an effort to 
develop engineering data to address the identified unsafe conditions of 
this NPRM. The FAA is anticipating that this effort will result in an 
STC that addresses the proposed requirements of this NPRM, and that 
this STC will be made available to all operators.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require the following nine actions:
    1. Incorporation of inspections into the operator's FAA-approved 
maintenance or inspection program that ensures the continued 
operational safety of the airplane. These inspections should be based 
on a damage tolerance assessment that identifies any PSE associated 
with the STC modification and should include associated inspection 
thresholds, inspection methods, and repetitive inspection intervals.
    2. Modification of the main deck cargo door structure and fuselage 
structure immediately surrounding the main deck cargo door to comply 
with the applicable requirements of CAR part 4b.
    3. A detailed visual inspection to detect cracks of the exposed 
surfaces of the main deck cargo door hinge (both fuselage and door side 
hinge elements); and repair or replacement of the hinge element with a 
new, like part, if necessary.
    4. A detailed visual inspection to detect cracks or other 
discrepancies (i.e., double or closely drilled holes, corrosion, chips, 
scratches, or gouges) of the mating surfaces of the main deck cargo 
door hinge, skin of the main deck cargo door, and external fuselage 
doubler underlying the hinge; and repair, if necessary.
    5. Installation of a main deck cargo door hinge that complies with 
the applicable requirements of CAR part 4b, including fail-safe 
requirements.
    6. An inspection and evaluation of the cargo handling system to 
determine if the side restraints provide the support required by the 
ULD; and modification of the vertical side restraint to provide the 
support appropriate to the ULD's compatible with the cargo handling 
system, if necessary.
    7. Modification of the main deck cargo floor to safely carry the 
applicable FAA-approved payload limits for above and below the main 
deck cargo floor. The modification must comply with the applicable 
requirements of CAR part 4b for the FAA-approved payload distribution.
    8. An inspection and evaluation of the venting system of the main 
deck cargo floor to determine if the system limits decompression loads 
to a level that can be carried by the floor structure without failure; 
and modification of the venting system, as necessary, to limit the 
decompression loads to a level that can be supported successfully by 
the existing floor structure, if necessary.
    9. Installation of a main deck cargo 9g crash barrier that complies 
with the applicable requirements of CAR part 4b.
    The actions described above would be required to be accomplished in 
accordance with a method approved by the FAA.

Differences Between 727 and DC-8 NPRM Format

    The format and content of this NPRM differs from the following 
rulemaking actions that address similar concerns for Boeing Model 727 
series airplanes that have been modified to freighters by STC:
     AD 98-26-18, amendment 39-10961 (64 FR 1994, January 12, 
1999);
     AD 98-26-19, amendment 39-10962 (64 FR 2016, January 12, 
1999);
     AD 98-26-20, amendment 39-10963 (64 FR 2038, January 12, 
1999);
     AD 98-26-21, amendment 39-10964 (64 FR 2061, January 12, 
1999); and
     NPRM Rules Dockets 97-NM-232-AD, 97-NM-233-AD, 97-NM-234-
AD, and 97-NM-235-AD.
    However, the FAA used the same criteria (i.e., CAR part 4b) for 
evaluation of the subject Model 727 series airplanes and Model DC-8 
series airplanes affected by this NPRM. The differences in the subject 
rulemaking actions are accounted for by the variance in the design 
philosophies embraced by Douglas (now Boeing) and Boeing.
    The original floor beams for the DC-8 passenger airplanes have a 
deeper cross section, which reduces internal stresses for the same 
applied bending moment, than those for Model 727 series airplanes. 
Additionally, DC-8 passenger airplanes utilize intermediate ``struts'' 
between the main deck cargo floor beams and fuselage frames below the 
floor to help support the floor beams, which decreases the unsupported 
span. A shorter unsupported span helps reduce the bending moment for a 
given applied load. The amount of design data available to the FAA for 
review of each of the DC-8 STC's (i.e., SA1063SO, SA10377SO, SA1802SO, 
SA1832SO, SA1862SO, and SA00309AT) was greater than that available when 
the FAA issued the subject Model 727 NPRM's and AD's. Additionally, the 
JTF has assisted the FAA in engineering review of this greater volume 
of data and in the creation of additional data necessary for 
substantiation of the existing designs. Based on the data available for 
review, the margins of safety of the DC-8 floor beams indicate a lower 
level of immediate concern than those margins indicated for the 727 
floor beams when the 727 AD's and NPRM's were proposed. Therefore, the 
FAA has determined that the type of restrictions and interim floor 
loading and side vertical restraint that were applied to the 727 are 
not required for the subject DC-8 STC.
    To address the safety concerns of Boeing Model 727 series airplanes 
that

[[Page 58202]]

have been modified to freighters by STC, the FAA issued AD's 98-26-19, 
98-26-20, 98-26-21, and 98-26-22 to address the capability of the main 
deck cargo floor and then issued NPRM Rules Dockets 97-NM-232-AD, 97-
NM-233-AD, 97-NM-234-AD, and 97-NM-235-AD to address the door 
indicating system and related systems issues; means to prevent 
pressurization to an unsafe level if the door is not closed, latched, 
and locked; door hinge; and 9g crash barrier. Because there have been 
events involving the cargo door opening in flight on the modified DC-8 
series airplanes, the FAA has issued the following AD's to address the 
door indication system and other related systems issues for those 
airplanes:
     AD 2000-09-01 R1, amendment 39-11809 (65 FR 41869, July 7, 
2000);
     AD 2000-09-02, amendment 39-11710 (65 FR 25437, May 2, 
2000);
     AD 2000-13-03 R1, amendment 39-11865 (65 FR 49735, August 
15, 2000); and
     AD 2000-15-11, amendment 39-11843 (65 FR 47660, August 3, 
2000).
    This DC-8 NPRM, and NPRM Rules Dockets 2000-NM-280-AD, 2000-NM-281-
AD, and 2000-NM-283-AD would address the structures issues, including 
the main deck cargo floor, as discussed previously.

Cost Impact

    There are approximately 6 Model DC-8 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 6 
airplanes of U.S. registry would be affected by this proposed AD. The 
following table shows the estimated cost impact for airplanes affected 
by this AD. The average labor rate is $60 per work hour. The estimated 
maximum total cost for all airplanes affected by this proposed AD is 
$1,175,820, or $196,420 per airplane.

----------------------------------------------------------------------------------------------------------------
                                         Work hours      Parts cost
                Action                   (estimated)     (estimated)            Total cost  (estimated)
----------------------------------------------------------------------------------------------------------------
Incorporation of inspections into                   8             N/A  $2,880 or $480 per airplane.
 maintenance or inspection program.
Modification of main deck cargo door              225             700  $85,200, or $14,200 per airplane.
 structure and fuselage structure.
Inspection of exposed surfaces of                  16             N/A  $5,760, or $960 per airplane.
 main deck cargo door hinge.
Inspection of mating surfaces of main              16             N/A  $5,760, or $960 per airplane.
 deck cargo door hinge.
Installation of a main deck cargo                  60            $200  $22,800, or $3,800 per airplane.
 door hinge.
Inspection and evaluation of the                   16             N/A  $5,760, or $960 per airplane.
 cargo handling system.
Modification of main deck cargo floor              60            $500  $24,600 or $4,100 per airplane.
Inspection and evaluation of the                   16             N/A  $5,760, or $960 per airplane.
 venting system.
Installation of main deck cargo 9g              2,000         $50,000  $1,020,000, or $170,000 per airplane.
 crash barrier.
----------------------------------------------------------------------------------------------------------------

    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed requirements 
of this AD action, and that no operator would accomplish those actions 
in the future if this proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.

Regulatory Impact

    The regulations proposed herein would not have a substantial direct 
effect 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, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

McDonnell Douglas: Docket 2000-NM-282-AD.

    Applicability: Model DC-8 series airplanes that have been 
converted from a passenger-to a cargo-carrying (``freighter'') 
configuration in accordance with Supplemental Type Certificate (STC) 
SA1832SO; 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 request approval for an

[[Page 58203]]

alternative method of compliance in accordance with paragraph (i) 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 prevent opening of the cargo door while the airplane is in 
flight or collapse of the main deck cargo floor, and consequent 
rapid decompression of the airplane including possible loss of 
flight control or severe structural damage, accomplish the 
following:

Actions Addressing the Main Deck Cargo Door and Associated Fuselage 
Structure

    (a) Accomplish the actions specified in paragraphs (a)(1) and 
(a)(2) of this AD in accordance with a method approved by the 
Manager, Los Angeles Aircraft Certification Office (ACO), FAA.
    (1) Within 1 year or 1,200 flight cycles after the effective 
date of this AD, whichever occurs first, incorporate inspections 
into the operator's FAA-approved maintenance or inspection program 
that ensure the continued operational safety of the airplane. These 
inspections should be based on a damage tolerance assessment that 
identifies any principal structural element (PSE) associated with 
the STC modification and should include associated inspection 
thresholds, inspection methods, and repetitive inspection intervals.
    (2) Within 3 years or 4,000 flight cycles after the effective 
date of this AD, whichever occurs first, accomplish the actions 
specified in paragraphs (a)(2)(i) and (a)(2)(ii) of this AD.
    (i) Modify the main deck cargo door structure and fuselage 
structure immediately surrounding the main deck cargo door to comply 
with the applicable requirements of Civil Air Regulations (CAR) part 
4b.
    (ii) Incorporate inspections into the operator's FAA-approved 
maintenance or inspection program that ensure the continued 
operational safety of the airplane. These inspections should be 
based on a damage tolerance assessment that identifies any PSE 
associated with the STC modification required by paragraph (a)(2)(i) 
of this AD and should include associated inspection thresholds, 
inspection methods, and repetitive inspection intervals.

Actions Addressing the Main Deck Cargo Floor

    (b) Within 2 years or 2,000 flight cycles after the effective 
date of this AD, whichever occurs first, perform an inspection and 
evaluation of the cargo handling system to determine if the side 
restraints provide the support required by the unit load device 
(ULD), in accordance with a method approved by the Manager, Los 
Angeles ACO. If any vertical side restraint does not provide the 
required support, within 2 years or 2,000 flight cycles after the 
effective date of this AD, whichever occurs first, modify the 
vertical side restraint to provide the support appropriate to the 
ULD's compatible with the cargo handling system, in accordance with 
a method approved by the Manager, Los Angeles ACO.
    (c) Within 3 years or 4,000 flight cycles after the effective 
date of this AD, whichever occurs first, modify the main deck cargo 
floor to safely carry the applicable FAA-approved payload limits for 
above and below the main deck cargo floor. The modification and 
payload distribution shall be accomplished in accordance with a 
method approved by the Manager, Los Angeles ACO. The modification 
must comply with the applicable requirements of CAR part 4b for the 
FAA-approved payload distribution.
    (d) Except for those airplanes that have been modified in 
accordance with paragraph (c) of this AD, within 1 year or 1,000 
flight cycles after the effective date of this AD, whichever occurs 
first, perform an inspection and evaluation of the venting system of 
the main deck cargo floor to determine if the system limits 
decompression loads to a level that can be carried by the floor 
structure without failure, in accordance with a method approved by 
the Manager, Los Angeles ACO.
    (e) If, based on the evaluation required by paragraph (d) of 
this AD, the venting system does not limit decompression loads to a 
level that can be carried by the floor structure without failure, 
within 2 years after the effective date of this AD, modify the 
venting system, as necessary, to limit the decompression loads to a 
level that can be supported successfully by the existing floor 
structure, in accordance with a method approved by the Manager, Los 
Angeles ACO.

Actions Addressing Main Deck Cargo Door Hinge

    (f) Within 250 flight cycles after the effective date of this 
AD, perform a detailed visual inspection to detect cracks of the 
exposed surfaces of the main deck cargo door hinge (both fuselage 
and door side hinge elements), in accordance with a method approved 
by the Manager, Los Angeles ACO. If any crack is detected, prior to 
further flight, repair in accordance with a method approved by the 
Manager, Los Angeles ACO, or replace the cracked hinge element with 
a new, like part.

    Note 2: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

    (g) Within 3 years or 4,000 flight cycles after the effective 
date of this AD, whichever occurs first, accomplish the actions 
specified in paragraphs (g)(1) and (g)(2) of this AD in accordance 
with a method approved by the Manager, Los Angeles ACO.
    (1) Perform a detailed visual inspection to detect cracks or 
other discrepancies (i.e., double or closely drilled holes, 
corrosion, chips, scratches, or gouges) of the mating surfaces of 
the main deck cargo door hinge, skin of the main deck cargo door, 
and external fuselage doubler underlying the hinge. If any 
discrepancy is detected, prior to further flight, repair the 
discrepant part.
    (2) Install a main deck cargo door hinge that complies with the 
applicable requirements of CAR part 4b, including fail-safe 
requirements.

Actions Addressing Main Deck Cargo 9g Crash Barrier

    (h) Within 3 years or 4,000 flight cycles after the effective 
date of this AD, whichever occurs first, install a main deck cargo 
9g crash barrier that complies with the applicable requirements of 
CAR part 4b, in accordance with a method approved by the Manager, 
Los Angeles ACO.

Alternative Methods of Compliance

    (i) 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, Los Angeles ACO, FAA. Operators 
shall submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Los Angeles ACO.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles ACO.

Special Flight Permit

    (j) 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.

    Issued in Renton, Washington, on September 21, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-24747 Filed 9-26-00; 8:45 am]
BILLING CODE 4910-13-U