[Federal Register Volume 64, Number 245 (Wednesday, December 22, 1999)]
[Proposed Rules]
[Pages 71689-71694]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-33171]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-338-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 supersedure of an existing 
airworthiness directive (AD), applicable to certain McDonnell Douglas 
Model DC-8 series airplanes, that currently requires a revision to the 
Airplane Flight Manual Supplement to ensure that the main deck cargo 
door is closed, latched, and locked; repetitive inspections of the wire 
bundle and door latch rollers to detect damage; and repair or 
replacement of damaged components. This action would require, among 
other actions, modification of the indication and hydraulic systems of 
the main deck cargo door, and installation of a means to prevent 
pressurization to an unsafe level if the main deck cargo door is not 
closed, latched, and locked. This proposal is prompted by the FAA's 
determination that certain main deck cargo door systems do not provide 
an adequate level of safety; the latching and locking mechanisms are 
not of adequate design to prevent structural deformation in the event 
of component jamming; and that there is an absence of a means to 
prevent pressurization to an unsafe level if the main deck cargo door 
is not closed, latched, and locked. The actions specified by the 
proposed AD are intended to prevent opening of the cargo door while the 
airplane is in flight, and consequent rapid decompression of the 
airplane including possible loss of the door, flight control, or severe 
structural damage.

DATES: Comments must be received by February 7, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-338-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.
    The service information referenced in the proposed rule may be 
obtained from National Aircraft Service, Inc. (NASI), 9133 Tecumseh-
Clinton Road, Tecumseh, MI 49286. This information may be examined at 
the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; or at the FAA, Transport Airplane Directorate, 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, Transport Airplane Directorate, Los 
Angeles Aircraft Certification Office, 3960 Paramount Boulevard, 
Lakewood,

[[Page 71690]]

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.
    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 99-NM-338-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. 99-NM-338-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On October 8, 1993, the FAA issued AD 93-20-02, amendment 39-8709 
(58 FR 53635, October 18, 1993), applicable to certain McDonnell 
Douglas Model DC-8 series airplanes equipped with a cargo conversion 
modification installed in accordance with Supplemental Type Certificate 
(STC) SA1802SO or SA421NW. That AD requires a revision to the FAA-
approved Airplane Flight Manual Supplement (AFMS) to include detailed 
procedures for use of the cargo door warning light system; repetitive 
inspections of the cargo door warning system wiring and door latching 
roller mechanism to detect damage; and repair or replacement of damaged 
components. That action was prompted by the FAA's review of data 
indicating that disabling of certain circuit breakers may deprive the 
flight crew of necessary information. The requirements of that AD are 
intended to prevent loss of the cargo door, damage to flight control 
surfaces, and reduced controllability of the airplane.

Actions Since Issuance of Previous Rule

    Since issuance of that AD, 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 NPRM.] The modification defined 
by STC SA421NW (held by NASI) is nearly identical to that defined by 
SA1802SO; therefore, SA421NW has the same potential unsafe conditions. 
STC 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, and Class ``E'' cargo interior with 
a cargo barrier on McDonnell Douglas Model DC-8 series airplanes.
    This NPRM proposes corrective action for those potential 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. These conditions, if not corrected, could result in opening 
of the cargo door while the airplane is in flight, and consequent rapid 
decompression of the airplane including possible loss of the door, 
flight control, or severe structural damage.

Other Related Rulemaking

    The FAA is considering further rulemaking to address the remaining 
potential unsafe conditions relating to the unreinforced main deck 
floor, main deck cargo door hinge, and fuselage structure in the area 
modified by installation of a main deck cargo door, 9g crash barrier, 
and fire/smoke detection system.

Main Deck Cargo Door Systems

    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 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 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 issued a 
memorandum to the Director-Airworthiness and Technical Standards of ATA 
(hereinafter referred to as ``the FAA Memorandum''), acknowledging 
ATA's recommendations and 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. Appendix 1 of this AD

[[Page 71691]]

contains the specific paragraphs from the FAA Memorandum that set forth 
the criteria to which the outward opening doors should be shown to 
comply.
    Using 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 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 R1, amendment 39-6415 (54 FR 50489, December 7, 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); and
     For certain Boeing Model 727-100 and -200 series 
airplanes: AD 96-16-08, amendment 39-9708 (61 FR 41733, August 12, 
1996).
    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 an 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 
five STC's that addresses 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 to identify which airplanes are modified by each 
STC. It also has been 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 been coordinating the funding of the industry 
review of the data supporting the STC's and ongoing efforts to resolve 
safety issues identified by the FAA.
    Using the criteria specified in the ATA Final Report and the FAA 
Memorandum as evaluation guides, the FAA, in collaboration with the 
JTF, conducted an engineering design review and inspection of an 
airplane modified in accordance with STC SA1802SO. The FAA identified a 
number of design features of the main deck cargo door systems of this 
STC that are unsafe and do not meet the criteria specified in the ATA 
Final Report and the FAA Memorandum. These systems include the door 
indication and hydraulic systems, and the lack of a means to prevent 
pressurization of the airplane to an unsafe level if the door is not 
fully closed, latched, and locked. The FAA design review team also 
determined that the design data of this STC did not include an adequate 
safety analysis of the main deck cargo door systems.
    The FAA has received reports of a recent event in which a main deck 
cargo door came open during take-off. This event was attributed, in 
part, to improper indication to the flight crew that the main deck 
cargo door was closed, latched, and locked. Service experience 
indicates that 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 of the airplane.
    For airplanes modified in accordance with STC's SA1802SO or 
SA421NW, the FAA considers the following five specific design features 
of the main deck cargo door systems to be unsafe:

1. Indication System

    The main deck cargo door indication system for STC's SA1802SO and 
SA421NW uses a warning light at the flight engineer's panel. This light 
indicates the door open or closed status but does not provide the 
status of the cargo door latch and lock positions. All three conditions 
(i.e., door closed, latched, and locked) must be monitored directly so 
that the door indication system cannot display either ``latched'' 
before the door is closed or ``locked'' before the door is latched. If 
a sequencing error caused the door to latch and lock without being 
fully closed, the subject indication system, as designed, would not 
alert the door operator or the flight engineer of this condition. As a 
result, the airplane could be dispatched with the main deck cargo door 
unsecured, which could lead to the cargo door opening while the 
airplane is in flight.
    The light on the flight engineer's panel is labeled ``CARGO DOOR 
WARNING'' and is displayed in red since it indicates an event that 
requires immediate pilot action.
    However, if the flight engineer is temporarily away from his 
station, a door unsafe warning indication could be missed by the 
pilots. Therefore, an indicator light must be located in front of and 
in plain view of both pilots since one of the pilot's stations is 
always occupied during flight operations.

2. Means To Visually Inspect the Locking Mechanism

    The single view port of the main deck cargo door, installed in 
accordance with STC's SA1802SO and SA421NW monitors only one of the 12 
locks of the main deck cargo door. Therefore, the single view port does 
not provide confirmation that all of the locks of the main deck cargo 
door are engaged properly in the latches.

3. Means To Prevent Pressurization to an Unsafe Level

    McDonnell Douglas DC-8 series airplanes modified in accordance with 
STC SA1820SO or SA421NW have no means of preventing pressurization to 
an unsafe level in the event that the main deck cargo door is not 
closed, latched, and locked, which could precipitate a cargo door 
opening while the airplane is in flight.

4. Powered Lock Systems

    Evaluation of the powered lock systems of the main deck cargo door 
for STC's SA1802SO and SA421NW indicates the potential for latent and/
or single point failures that could restore or continue power to the 
door controls, which could result in inadvertent door openings while 
the airplane is in flight. STC's SA1802SO and SA421NW utilize a nose 
gear squat switch to remove door control power (i.e., electrical and 
hydraulic). Latent failure of the squat

[[Page 71692]]

switch together with other latent and/or single point failures could 
precipitate inadvertent door openings.
    AD 93-20-02 requires, prior to takeoff, pulling the circuit 
breakers of the main deck cargo door labeled ``pump'' and ``valve'' to 
ensure power is removed from the main deck cargo door. This requirement 
is considered to be interim action. To minimize the potential for 
latent failure of a circuit breaker in conjunction with the squat 
switch, the FAA finds that, for the purposes of this proposed AD, these 
circuit breakers must be replaced with new parts.
    The design data for STC's SA1802SO and SA421NW do not include a 
systems safety analysis to show that an inadvertent opening of a cargo 
door is extremely improbable. The need for a system safety analysis is 
identified in the ATA Final Report and the FAA Memorandum.

5. Lock Strength

    Analysis of the existing latching and locking mechanism of the main 
deck cargo door indicates that, because of the existing latching and 
locking hydraulic cylinders, the translating beam, lever, swivel arm 
brackets, lock pins, and swivel arms have inadequate strength to 
prevent structural deformation of these parts in the event of 
components jamming. Structural deformation of the locking mechanism 
could result in the door latches not being locked and erroneous 
indication to the flightcrew that the latches are locked properly.

Explanation of Relevant Service Information

    The FAA has reviewed and approved NASI Service Bulletin SB-99-01, 
Revision A, dated October 15, 1999. The service bulletin describes 
procedures for modification of the mechanical and hydraulic systems of 
the main deck cargo door installed in accordance with STC SA1802SO or 
SA421NW. The modification provides new parts of adequate strength to 
prevent structural deformation of the latching and locking mechanism by 
reducing the force of the latching and locking hydraulic cylinders and 
increasing the structural strength of the locking components. The 
modification involves installing a new translating beam, lever, swivel 
arm brackets, lock pins, swivel arms, hydraulic cylinders, and 
hydraulic lines.
    Accomplishment of the actions specified in the service bulletin and 
the actions described below is intended to adequately address the 
identified unsafe conditions.

Explanation of Requirements of Proposed Rule

    Since unsafe conditions have been identified that are likely to 
exist or develop on other products of this same type design, the 
proposed AD would supersede AD 93-20-02 to continue to require a 
revision to the FAA-approved AFMS to include detailed procedures for 
use of the cargo door warning light system; repetitive inspections of 
the cargo door warning system wiring and door latching roller mechanism 
to detect damage; and repair or replacement of damaged components.
    The proposed AD also would require, within 30 days after the 
effective date of this AD, unless previously accomplished within the 
last 18 months prior to the effective date of this AD, replacement of 
the circuit breakers of the main deck cargo door labeled ``pump'' and 
``valve'' with new circuit breakers.
    The proposed AD also would require, within 18 months after the 
effective date of this AD, accomplishment of the actions specified in 
the service bulletin described previously.
    In addition, the proposed AD would require, within 18 months after 
the effective date of this AD, modification of the indication system of 
the main deck cargo door to indicate to the pilots whether the main 
deck cargo door is closed, latched, and locked; installation of a means 
to visually inspect the locking mechanism of the main deck cargo door; 
installation of a means to remove power to the door while the airplane 
is in flight; and installation of a means to prevent pressurization to 
an unsafe level if the main deck cargo door is not closed, latched, and 
locked. These actions would be required to be accomplished in 
accordance with a method approved by the Manager, Los AngelesAircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate. 
Installation of STC ST01116CH (held by NASI) is an approved means of 
compliance with the modification requirements described previously. 
Accomplishment of these actions and the procedures described in NASI 
Service Bulletin SB-99-01 would constitute terminating action for the 
requirements of AD 93-20-02 [paragraphs (a) and (b) of this proposed 
AD].

Differences Between the AD and Relevant Service Information

    The referenced service bulletin recommends accomplishing the 
modification of the hydraulic systems of the main deck cargo door 
within 180 days from July 1, 1999, not to exceed 270 calendar days from 
July 1, 1999. However, the FAA finds that accomplishing the following 
actions provides an acceptable level of safety until accomplishment of 
the modification:
     Replacement of the circuit breakers of the main deck cargo 
door labeled``pump'' and ``valve'' with new circuit breakers;
     An FAA-approved AFMS revision to include detailed 
procedures for use of the cargo door warning light system as specified 
in paragraph (b) of the proposed AD; and
     Repetitive inspections of the cargo door warning system 
wiring and door latching roller mechanism to detect damage as specified 
in paragraph (a) of the proposed AD.
    Therefore, the FAA finds an 18-month compliance time for initiating 
the required modification to be warranted, in that it represents an 
appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.

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 actions that are currently required by AD 93-20-02, and 
retained in this proposed AD, take approximately 1 work hour per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of the currently required 
actions on U.S. operators is estimated to be $1,740, or $60 per 
airplane, per inspection cycle.
    It would take 1 work hour per airplane to accomplish the new 
replacement of circuit breakers, at an average labor rate of $60 per 
work hour. Required parts would cost approximately $265 per airplane. 
Based on these figures, the cost impact of this new replacement 
proposed by this AD on U.S. operators is estimated to be $9,425, or 
$325 per airplane.
    It would take 80 work hours per airplane to accomplish the new 
modification of the hydraulic systems, at an average labor rate of $60 
per work hour. Required parts would cost approximately $20,000 per 
airplane. Based on these figures, the cost impact of this new 
modification proposed by this AD on U.S. operators is estimated to be 
$719,200, or $24,800 per airplane.
    The FAA estimates that it would take approximately 130 work hours 
per airplane to accomplish the modification required by paragraph (d) 
of the

[[Page 71693]]

proposed AD, at an average labor rate of $60 per work hour. The FAA 
also estimates that required parts would cost approximately $25,000 per 
airplane. Based on these figures, the cost impact of this modification 
proposed by this AD on U.S. operators is estimated to be $951,200, or 
$32,800 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.

Regulatory Impact

    The regulations 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 removing amendment 39-8709 (58 FR 
53635, October 18, 1993), and by adding a new airworthiness directive 
(AD), to read as follows:

McDonnell Douglas: Docket 99-NM-338-AD. Supersedes AD 93-20-02, 
Amendment 39-8709.

    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 (g) 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, and consequent rapid decompression of the airplane including 
possible loss of the door, flight control, or severe structural 
damage, accomplish the following:

Restatement of Requirements of AD 93-20-02

Actions Addressing the Main Deck Cargo Door

    (a) Within 7 days after January 21, 1992 (the effective date of 
AD 92-02-05, amendment 39-8141), and thereafter at intervals not to 
exceed 100 hours time-in-service, perform the following inspections:
    (1) Inspect the cargo door wire bundle between the exit point of 
the cargo liner and the attachment point on the cargo door to detect 
crimped, frayed, or chafed wires; and inspect for damaged, loose, or 
missing hardware mounting components. Prior to further flight, 
repair any damaged wiring or hardware mounting components in 
accordance with FAA-approved maintenance procedures.
    (2) Inspect the cargo door latch rollers in the lower sill of 
the cargo door opening of the airplane to ensure that all twelve 
rollers can be freely rotated by hand. Prior to further flight, 
replace any discrepant roller components found, and repair any 
rollers that cannot be rotated freely by hand, in accordance with 
FAA-approved maintenance procedures.
    (b) Within 7 days after November 17, 1993 (the effective date of 
AD 93-20-02, amendment 39-8709), revise the Limitations Section of 
the appropriate FAA-approved Airplane Flight Manual Supplement 
(AFMS) by replacing item 5 in the AFMS for SA1802SO, and item 6 in 
the AFMS for SA421NW, with the following. (This may be accomplished 
by inserting a copy of this AD into the AFMS.)
    ``Prior to initiating the cargo door closing sequence, a flight 
crew member must verify that the cargo door warning light is 
illuminated. After the door closing sequence is complete, and visual 
verification has been made that the latches are closed and the 
lockpins are properly engaged, a flight crew member must verify that 
the cargo door warning light is extinguished, and then conduct a 
PRESS-TO-TEST of the warning light to ensure that the light is 
operational. Pull the cargo door circuit breakers labeled ``pump'' 
and ``valve'' prior to takeoff. Methods for documentation of 
compliance with the preceding procedures must be approved by the FAA 
Principal Maintenance Inspector (PMI).''

New Requirements of This AD

Actions Addressing the Main Deck Cargo Door Powered Lock Systems

    (c) Except as provided by paragraph (f) of this AD, within 30 
days after the effective date of this AD, unless previously 
accomplished within the last 18 months prior to the effective date 
of this AD, replace the circuit breakers of the main deck cargo door 
labeled ``pump'' and ``valve'' with new circuit breakers.

Actions Addressing the Main Deck Cargo Door Hydraulic Systems

    (d) Within 18 months after the effective date of this AD, modify 
the mechanical and hydraulic systems of the main deck cargo door, in 
accordance with National Aircraft Services, Inc. (NASI) Service 
Bulletin SB-99-01, Revision A, dated October 15, 1999.

Actions Addressing the Main Deck Cargo Door Indication System

    (e) Within 18 months after the effective date of this AD, modify 
the indication system of the main deck cargo door to indicate to the 
pilots whether the main deck cargo door is closed, latched, and 
locked; install a means to visually inspect the locking mechanism of 
the main deck cargo door; install a means to remove power to the 
door while the airplane is in flight; and install a means to prevent 
pressurization to an unsafe level if the main deck cargo door is not 
closed, latched, and locked; in accordance with a method approved by 
the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, 
Transport Airplane Directorate.

    Note 2: Installation of NASI Vent Door System STC ST01116CH, is 
an approved means of compliance with the requirements of paragraph 
(e) of this AD.

    (f) Compliance with both paragraphs (d) and (e) of this AD 
constitutes terminating action for the requirements of both 
paragraphs (a) and (b) of this AD, and the AFMS revision required by 
paragraph (b) of this AD may be removed. Compliance with paragraph 
(e) of this AD within 30 days after the effective date of this AD 
eliminates the requirement to comply with paragraph (c) of this AD.

Alternative Methods of Compliance

    (g) 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

[[Page 71694]]

Angeles ACO. Operators shall submit their requests through an 
appropriate FAA PMI, 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 Permits

    (h) 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.

Appendix 1

Excerpt from an FAA Memorandum to Director-Airworthiness and 
Technical Standards of ATA, dated March 20, 1992

    ``(1) Indication System:
    (a) The indication system must monitor the closed, latched, and 
locked positions, directly.
    (b) The indicator should be amber unless it concerns an outward 
opening door whose opening during takeoff could present an immediate 
hazard to the airplane. In that case the indicator must be red and 
located in plain view in front of the pilots. An aural warning is 
also advisable. A display on the master caution/warning system is 
also acceptable as an indicator. For the purpose of complying with 
this paragraph, an immediate hazard is defined as significant 
reduction in controllability, structural damage, or impact with 
other structures, engines, or controls.
    (c) Loss of indication or a false indication of a closed, 
latched, and locked condition must be improbable.
    (d) A warning indication must be provided at the door operators 
station that monitors the door latched and locked conditions 
directly, unless the operator has a visual indication that the door 
is fully closed and locked. For example, a vent door that monitors 
the door locks and can be seen from the operators station would meet 
this requirement.
    (2) Means to Visually Inspect the Locking Mechanism: There must 
be a visual means of directly inspecting the locks. Where all locks 
are tied to a common lock shaft, a means of inspecting the locks at 
each end may be sufficient to meet this requirement provided no 
failure condition in the lock shaft would go undetected when viewing 
the end locks. Viewing latches may be used as an alternate to 
viewing locks on some installations where there are other 
compensating features.
    (3) Means to Prevent Pressurization:
    All doors must have provisions to prevent initiation of 
pressurization of the airplane to an unsafe level, if the door is 
not fully closed, latched and locked.
    (4) Lock Strength:
    Locks must be designed to withstand the maximum output power of 
the actuators and maximum expected manual operating forces treated 
as a limit load. Under these conditions, the door must remain 
closed, latched and locked.
    (5) Power Availability:
    All power to the door must be removed in flight and it must not 
be possible for the flight crew to restore power to the door while 
in flight.
    (6) Powered Lock Systems:
    For doors that have powered lock systems, it must be shown by 
safety analysis that inadvertent opening of the door after it is 
fully closed, latched and locked, is extremely improbable.''

    Issued in Renton, Washington, on December 16, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-33171 Filed 12-21-99; 8:45 am]
BILLING CODE 4910-13-U