[Federal Register Volume 65, Number 188 (Wednesday, September 27, 2000)]
[Proposed Rules]
[Pages 58203-58209]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-24746]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-283-AD]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model DC-8 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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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

[[Page 58204]]

other actions, modification of the main deck cargo door structure and 
fuselage structure; replacement of fasteners in the two door-side hinge 
elements; 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, 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.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-283-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-283-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-283-AD.'' The postcard will be date stamped 
and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 2000-NM-283-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has conducted a design review of McDonnell Douglas Model 
DC-8 series airplanes modified in accordance with STC SA1802SO 
(originally issued to Rosembalm and currently held by National Aircraft 
Services, Inc. (NASI)) and has identified several potential unsafe 
conditions. [Results of this design review are contained in ``DC-8 
Cargo Modification Review Team Review of Rosenbalm Supplemental Type 
Certificate SA1802SO--Installation of a Cargo Door and Interior, Final 
Report, Revision A, dated November 29, 1999,'' hereinafter referred to 
as ``the Design Review Report,'' which is included in the Rules Docket 
for this notice of proposed rulemaking (NPRM).) The modification 
defined by STC SA421NW (also held by NASI) is nearly identical to that 
defined by STC SA1802SO; therefore, STC SA421NW has the same potential 
unsafe conditions. STC's SA1802SO and SA421NW specify a design for 
installation of a main deck cargo door, associated door cutout in the 
fuselage, door system hydraulics, door indication system, Class E 
compartment with a 9g crash barrier, and cargo handling system on 
McDonnell Douglas Model DC-8 series airplanes.
    On June 28, 2000, the FAA issued airworthiness directive (AD) 2000-
09-01 R1, amendment 39-11809 (65 FR 41869, June 7, 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 2000-09-01 R1, 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's SA1802SO and SA421NW 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

[[Page 58205]]

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 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 2000-09-01 R1, amendment 39-11809 (65 FR 41869, June 7, 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 SA1802SO, 
and identified a number of design features of this STC that are unsafe, 
which are applicable to STC SA421NW, as well. 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's SA1802SO and SA421NW 
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 elements across 
the main deck cargo door sill;
     Reinforcement of the shear transfer capability between the 
door jamb frames and the fuselage skin and doubler;
     Reinforcement of the inner cap of the frame at fuselage 
station (FS) 1700;
     Replacement of existing fasteners in the door side end 
segments of the hinge with increased strength bolts;
     Reinforcement of the existing shear transfer capability of 
the frames below the main deck cargo door, as well as in the door 
itself; and
      Reinforcement of the frames that support the two latches 
at both ends 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 SA1802SO is necessary to 
ensure the structural integrity for all airplanes in the affected 
fleet. This damage tolerance

[[Page 58206]]

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 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). The hinge installed by STC's 
SA1802SO and SA421NW is no exception. However, based on the results of 
the FAA's and JTF's structural evaluation of the hinge of the subject 
STC's, the FAA has determined that the existing fasteners attaching the 
two hinge elements to the cargo door at both the forward and aft ends 
of the hinge are inadequate to carry the design loads. Therefore, these 
fasteners must be replaced with fasteners of sufficient strength.
    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. A possible consequence of the 
undetected failure of hinge elements 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. 
Therefore, 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) is also necessary to ensure that the affected airplanes 
are not in immediate risk of hinge failure.

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's 
SA1802SO and SA421NW. 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's SA1802SO and SA421NW, 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's SA1802SO and SA421NW 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 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

[[Page 58207]]

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 January 1999 of a McDonnell Douglas Model 
DC-8 modified in accordance with STC SA1802SO. 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 eight 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. Replacement of the existing fasteners in the two door-side hinge 
elements at the forward and aft ends of the hinge with fasteners of 
acceptable strength.
    5. 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.
    6. 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.
    7. 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.
    8. 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's.
    To address the safety concerns of Boeing Model 727 series airplanes 
that 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

[[Page 58208]]

     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-282-AD would address the structures issues, including 
the main deck cargo floor, as discussed previously.

Cost Impact

    There are approximately 32 Model DC-8 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 29 
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 
$6,718,140, or $231,660 per airplane.

----------------------------------------------------------------------------------------------------------------
                                         Work hours      Parts cost
                Action                   (estimated)     (estimated)            Total cost  (estimated)
----------------------------------------------------------------------------------------------------------------
Incorporation of inspections into                   8             N/A  $13,920, or $480 per airplane.
 maintenance or inspection program.
Modification of main deck cargo door            1,420          $6,500  $2,659,300, or $91,700 per airplane.
 structure and fuselage structure.
Inspection of exposed surfaces of                  16             N/A  $27,840, or $960 per airplane.
 main deck cargo door hinge.
Replacement of the existing fasteners              60             100  $107,300, or $3,700 per airplane
 in the two door-side hinge elements.
Inspection and evaluation of the                   16             N/A  $27,840, or $960 per airplane.
 cargo handling system.
Modification of main deck cargo floor              40            $500  $84,100, or $2,900 per airplane.
Inspection and evaluation of the                   16             N/A  $27,840, or $960 per airplane.
 venting system.
Installation of main deck cargo 9g              1,500          40,000  $3,770,000, or $130,000 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 Doublas: Docket 2000-NM-283-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) 
SA1802SO or SA421NW; 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 
alternative method of compliance in accordance with paragraph (h) 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

[[Page 58209]]

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) Accomplish the actions specified in paragraphs (f)(1) and 
(f)(2) of this AD in accordance with a method approved by the 
Manager, Los Angeles ACO.
    (1) Within 250 flight hours 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). 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.''

    (2) Within 2 years or 2,000 flight hours after the effective 
date of this AD, whichever occurs first, replace the existing 
fasteners in the two door-side hinge elements at the forward and aft 
ends of the hinge with fasteners of acceptable strength.

Actions Addressing Main Deck Cargo 9g Crash Barrier

    (g) 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

    (h) 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

    (i) 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. 00-24746 Filed 9-26-00; 8:45 am]
BILLING CODE 4910-13-U