AD 2002-16-21

[Federal Register Volume 67, Number 158 (Thursday, August 15, 2002)]
[Rules and Regulations]
[Pages 53422-53434]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 02-20508]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-234-AD; Amendment 39-12860; AD 2002-16-21]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 727 Series Airplanes 
Modified in Accordance with Supplemental Type Certificate ST00015AT

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 727 series airplanes that have been 
converted from a passenger- to a cargo-carrying (``freighter'') 
configuration, that requires, among other actions, installation of a 
fail-safe hinge, redesigned main deck cargo door warning and power 
control systems, and 9g crash barrier. This amendment is prompted by 
the FAA's determination that the main deck cargo door hinge is not 
fail-safe; that certain main deck cargo door control systems do not 
provide an adequate level of safety; and that the main deck cargo 
barrier is not structurally adequate during an emergency landing. The 
actions specified by this AD are intended to prevent structural failure 
of the main deck cargo door hinge or failure of the cargo door system, 
which could result in the loss or 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; and to prevent failure of the main deck cargo 
barrier during an emergency landing, which could injure occupants.

DATES: Effective September 19, 2002.

ADDRESSES: Information pertaining to this amendment may be examined at 
the Federal Aviation Administration (FAA), Transport Airplane 
Directorate, Rules Docket, 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 O'Neil, Aerospace Engineer, 
Airframe Branch, ANM-120L, FAA, Transport Airplane Directorate, Los 
Angeles Aircraft Certification Office, 3960 Paramount Boulevard, 
Lakewood, California 90712; telephone (562) 627-5320; fax (562) 627-
5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 727 series 
airplanes that have been converted from a passenger to a cargo-carrying 
(``freighter'') configuration was published in the Federal Register on 
November 12, 1999 (64 FR 61540). That action proposed to require, among 
other actions, installation of a fail-safe hinge, redesigned main deck 
cargo door warning and power control systems, and 9g crash barrier.

[[Page 53423]]

Background

    For the convenience of the reader, certain excerpts and 
information, below, from the following sections of the preamble of the 
notice of proposed rulemaking (NPRM) are provided in this final rule: 
Discussion, Main Deck Cargo Door Hinge, Main Deck Cargo Door Systems, 
and Cargo Restraint Barrier.
    Supplemental Type Certificate (STC) ST00015AT (held by Stambaugh 
Aviation Services) specifies a design for a main deck cargo door, 
associated cargo door cutout, door systems, and Class ``E'' cargo 
interior with a cargo barrier. As discussed in NPRM, Rules Docket No. 
97-NM-80-AD (the final rule, AD 98-26-20, amendment 39-10963, was 
published in the Federal Register on January 12, 1999 (64 FR 2038)), 
which is applicable to certain Boeing Model 727 series airplanes that 
have been converted from a passenger to a cargo-carrying 
(``freighter'') configuration, the FAA has conducted a design review of 
Boeing Model 727 series airplanes modified in accordance with STC 
ST00015AT and has identified several potential unsafe conditions. 
(Results of this design review are contained in ``FAA Freighter 
Conversion STC Review, Report Number 4, dated February 6, 1997,'' 
hereinafter referred to as ``the Design Review Report,'' which is 
included in the Rules Docket 97-NM-234-AD.) This NPRM proposes 
corrective action for three of those potential unsafe conditions that 
relate to the following three areas: main deck cargo door hinge, main 
deck cargo door systems, and main deck cargo barrier.

Main Deck Cargo Door Hinge

    In order to avoid catastrophic structural failure, it has been a 
typical industry approach to design outward opening cargo doors 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). Another potential design approach is 
safe-life, where the critical structure is shown by analyses and/or 
tests to be capable of withstanding the repeated loads of variable 
magnitude expected in service for a specific service life. Safe-life is 
usually not used on critical structure because it is difficult to 
account for manufacturing or in-service accidental damage. For this 
reason, plus the fact that none of the STC holders have provided data 
in support of this approach, the safe-life approach will not be 
discussed further regarding the design and construction of the main 
deck cargo door hinge.
    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 
longitudinally undetected, 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 must be in compliance 
with Civil Air Regulations (CAR) part 4b, including CAR section 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 principal 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 ST00015AT 
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.
    On other Boeing Model 727 series airplanes modified in accordance 
with similar STCs, inspections revealed a number of fasteners with both 
short edge margins and short spacing in the cargo door cutout external 
doublers. Some edge margins were as small as one fastener diameter. 
Fasteners that are placed too close to the edge of a structural member 
or spaced too close to an adjacent fastener can result in inadequate 
joint strength and stress concentrations, which may result in fatigue 
cracking of the skin. If such defects were to exist in the structure of 
the door or the fuselage to which the main deck cargo door hinge is 
attached, the attachment of the hinge could fail, and consequently 
cause the door to open while the airplane is in flight.

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 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 during 
takeoff, these two accidents serve 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

[[Page 53424]]

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 contains the specific paragraphs from 
the FAA Memorandum that set forth the criteria to which the outward 
opening doors should be shown to comply.
    Applying the applicable requirements of CAR part 4b and design 
criteria provided by the FAA Memorandum, the FAA has reviewed the 
original type design of major transport airplanes, including Boeing 727 
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 
ADs:
    <bullet> For certain McDonnell Douglas Model DC-9 series airplanes: 
AD 89-11-02, amendment 39-6216 (54 FR 21416, May 18, 1989);
    <bullet> For all Boeing Model 747 series airplanes: AD 90-09-06, 
amendment 39-6581 (55 FR 15217, April 23, 1990);
    <bullet> For certain McDonnell Douglas Model DC-8 series airplanes: 
AD 93-20-02, amendment 39-8709 (58 FR 471545, October 18, 1993);
    <bullet> For certain Boeing Model 747-100 and -200 series 
airplanes: AD 96-01-51, amendment 39-9492 (61 FR 1703, January 23, 
1996); and
    <bullet> For certain Boeing Model 727-100 and -200 series 
airplanes: AD 96-16-08, amendment 39-9708 (61 FR 41733, August 12, 
1996).
    Using the criteria specified in the ATA Final Report and the FAA 
Memorandum as evaluation guides, the FAA conducted an engineering 
design review and inspection of an airplane modified in accordance with 
STC ST00015AT (held by Stambaugh Aviation Services). 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. The FAA design review team 
determined that the design data of this STC did not include an adequate 
safety analysis of the main deck cargo door systems.
    For airplanes modified in accordance with STC ST00015AT, the FAA 
considers the following three specific design deficiencies of the main 
deck cargo door systems to be unsafe:
1. Means To Visually Inspect the Locking Mechanism
    The three view ports installed in accordance with STC ST00015AT are 
located for viewing locking pins at the No. 2, No. 4, and No. 6 latch 
positions of the main deck cargo door. These view ports are intended to 
allow the flight crew to conduct a visual inspection of the cargo door 
locking mechanism to determine whether or not the cargo door is closed, 
latched, and locked. The view ports are used in conjunction with the 
door warning system and should provide a suitable back-up for 
confirming that the door is closed, latched and locked in the event 
that the main deck cargo door warning system malfunctions.
    However, during the FAA design review, it was determined that these 
view ports are installed at an angle; therefore, a visual inspection of 
the locking pins is not possible. Therefore, the FAA finds that these 
view ports cannot be used to confirm that the door is closed, latched, 
and locked when the cargo door warning system malfunctions.
    As discussed in the ATA Final Report and the FAA Memorandum, there 
must be a means of directly inspecting each lock or, at a minimum, the 
locks at each end of the lock shaft of certain designs, such that a 
failure condition in the lock shaft would be detectable.
2. Means To Prevent Pressurization to an Unsafe Level
    Boeing 727-200 airplanes modified in accordance with STC ST00015AT 
are configured to utilize two outward opening vent doors for the 
purpose of preventing pressurization of the airplane to an unsafe level 
in the event the main deck cargo door is not closed, latched, and 
locked. Because the vent door openings are approximately six inches in 
diameter, the opening area may be insufficient to prevent 
pressurization of the airplane to an unsafe level in the event the main 
deck cargo door is not closed, latched, and locked. Paragraph (1)(d) of 
Appendix 1 describes the requirement that a warning indication be 
provided to the door operators station to monitor the door condition. 
Another function of the vent doors, if properly designed, would be to 
provide such a visual warning indication. If the vent door is open, the 
door operator will know the door is not closed, locked, and latched. 
The vent doors in this design are not spring loaded to the fully open 
position. As a result, they may appear to be closed when in fact they 
are not. Rather than provide a positive indication of a safe door, they 
can create a false indication of the door status. Therefore, the 
position of these vent doors cannot be used to indicate that the main 
cargo door is closed, latched, and locked, nor that there is a 
malfunction in the vent door system.
    <bullet> ``Failure Mode and Effects Analysis (FMEA) for B727-200 
Cargo Door Modifications,'' dated November 20, 1991, was prepared by 
the STC holder as a qualitative safety analysis for the vent door 
system of this STC. The FMEA indicates that the system has single point 
failures of the vent door systems that can result in a false indication 
that the door is safe. The presence of single point failures reflects 
that the system does not meet the standard established in the ATA Final 
Report and FAA memorandum that a false indication of a closed, latched, 
and locked condition is improbable.
3. Powered Lock Systems
    The main deck cargo door actuation control system for STC ST00015AT 
utilizes a powered lock system. The main deck cargo door control system 
for STC ST00015AT that utilizes electrical interlock switches is 
designed to remove door control power (electrical and hydraulic) prior 
to flight and to prevent inadvertent door openings. The design shows 
the likelihood that latent and/or single point failures can restore or 
continue to allow power to the door controls and cause inadvertent door 
openings. The failure modes may be found in the electrical portion of 
the door control panel, which, in turn, activates the door control 
hydraulics. The potential for the occurrence of these failure 
conditions is increased by the harsh operating environment of freighter 
airplanes. Door system components are routinely exposed to 
precipitation, dirt, grease, and foreign object intrusion, all of which 
increase the likelihood of damage. As a result, wires, switches, and 
relays have a greater potential to fail or short circuit in such a way 
as to allow the cargo door to be powered open without an operator's 
command and regardless of electrical interlock positions.
    A systems safety analysis would normally evaluate and resolve the 
potential for these types of unsafe conditions. However, the design 
data for STC ST00015AT includes a systems safety analysis that is 
insufficient to show that an inadvertent opening of the main deck cargo 
door after it is fully closed, latched, and locked is extremely 
improbable. The need for a system safety analysis is identified in the 
ATA Final Report and the FAA Memorandum.

Cargo Barrier

    In order to ensure the safety of occupants during emergency landing 
conditions, the FAA first established in

[[Page 53425]]

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 727 
passenger airplane was designed to these criteria which specified an 
ultimate inertia load requirement of 9g in the forward direction. This 
criteria was applied to the seats and structure restraining the 
occupants, including the flight crew, as well as other items of mass in 
the fuselage.
    When the 727 passenger airplane is converted to carry cargo on the 
main deck, a cargo barrier is required, since most cargo containers and 
the 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 cargo 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 or death.
    The structural inadequacy of the cargo barrier was evident to the 
FAA during its review in October 1996 of a Boeing 727 modified in 
accordance with STC ST00015AT. The observations revealed that the 
design of the cargo barrier floor attachment and circumferential 
supporting structure does not provide adequate strength to withstand 
the 9g forward inertia load generated by the main deck cargo mass, nor 
does it provide a load path to effectively transfer the loads from the 
cargo barrier to the fuselage structure of the airplane. These 
observations are supported by data contained in ``ER 2785, Structural 
Substantiation of the 50k 9g Bulkhead Restraint System in Support of 
STC SA1543SO PN 53-1292-401 for the 9g Bulkhead 53-1980-300 Assembly 
with Upper Attachment Structure, Lower Attachment Structure, Floor 
Shear Web Structure, Seat Track Splice Fittings, Seat Tracks, and Seat 
Track Splices,'' dated September 29, 1996, by M.F. Daniel. Although 
this report was specific to STC SA1543SO, the FAA has determined that 
the data are applicable to airplane modified in accordance with STC 
ST00015AT because the design principles for attachment of the barriers 
in both STCs are the same. The report reveals that structural 
deficiencies were found in the net attach plates and floor attachment 
structure of the cargo barrier. The data show large negative margins of 
safety, which indicate that the inertia load capability of the cargo 
barrier is closer to 2g than the required 9g in the forward direction. 
From these analyses, it is evident that the cargo barrier would not be 
capable of preventing serious injury to the occupants during an 
emergency landing event with the full allowable cargo load.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    The FAA has received comments in response to the four NPRM actions 
(i.e., Rules Dockets 97-NM-232-AD, 97-NM-233-AD, 97-NM-234-AD, and 97-
NM-235-AD) that address the same subjects described above for four 
different sets of cargo modification STCs. Some of these comments 
addressed only one NPRM, while others addressed all four. Because in 
most cases the issues raised by the commenters are generally relevant 
to all four NPRMs, each final rule includes a discussion of all 
comments received.

Definition of Detailed Visual Inspection

    One commenter provided Boeing's definition of a detailed visual 
inspection. The commenter requests that the FAA approve Boeing's 
definition as meeting the ``detailed visual inspection'' definition 
specified in Note 2 of the NPRM. The commenter states that it has 
incorporated Boeing's definition into its General Maintenance Manual 
(GMM), and that it is performing the detailed visual inspection of the 
main deck cargo door hinge in accordance with the GMM. The commenter 
also states that acceptance of the existing Boeing's definition will 
allow for work standardization and consistency.
    The FAA partially concurs. The FAA concurs that, for the purpose of 
this AD, the definition provided by the commenter satisfies the intent 
of the definition contained in Note 2 of this AD. The detailed 
inspection definition specified in Note 2 of this AD is a standard 
definition that is used in all ADs that require a detailed inspection. 
Therefore, the FAA finds that no change to Note 2 of the final rule is 
necessary. However, for clarification purposes, the FAA has revised all 
references to a ``detailed visual inspection'' in the NPRM to 
``detailed inspection'' in the final rule.

Main Deck Cargo Door Hinge

    Two commenters request that the compliance time for accomplishing 
the detailed visual inspection required by paragraph (a) of the NPRM be 
revised. One commenter states that the compliance time should include a 
threshold of ``prior to the accumulation of five years since 
accomplishment of the original conversion.'' The commenter states that 
operators of newly modified airplanes should not have to accomplish the 
detailed visual inspection required by paragraph (a) of the NPRM 
because it would be unlikely that brand new hinges would develop cracks 
within 250 flight cycles after being installed. The other commenter 
states that the compliance time should be revised to ``at the next 
scheduled `B' check, or 350 cycles after the effective date of the 
NPRM, whichever occurs first.'' The commenter states that such an 
extension would allow the inspection to be accomplished during a 
regularly scheduled ``B'' check and would not be disruptive of normal 
maintenance inspection scheduling.
    The FAA partially concurs. The FAA does not concur that the 
compliance time should be extended from 250 flight cycles to 350 flight 
cycles. In developing an appropriate compliance time for the detailed 
inspection required by paragraph (a) of this AD, the FAA considered the 
degree of urgency associated with addressing the subject unsafe 
condition; the results from an FAA report, ``Damage Tolerance Analysis 
of 727 Cargo Door Hinge,'' dated October 10, 1997; and the practical 
aspect of accomplishing the required inspection within an interval of 
time that parallels the typical ``A'' check scheduled maintenance 
interval for the majority of affected operators.
    However, the FAA concurs with the commenter about the unlikelihood 
of a newly modified airplane developing cracks within 250 flight cycles 
since installation. Based on the referenced FAA damage tolerance 
report, the FAA finds that it is unlikely that a significant crack 
would occur in the hinge within 4,000 flight cycles since installation. 
Therefore, the FAA finds that operators must accomplish the detailed 
inspection ``prior to accumulation of 4,000 flight cycles since 
accomplishment of the installation of the main deck cargo door, or 
within 250 flight cycles after the effective date of this AD, whichever 
occurs later.'' The FAA has revised paragraph (a) of the final rule 
accordingly.

[[Page 53426]]

    One commenter requests that a high frequency eddy current (HFEC) 
inspection be required in paragraph (a) of the NPRM in lieu of the 
detailed visual inspection. The commenter states that an HFEC 
inspection should be used because there are no proposed repetitive 
inspections and a detailed visual inspection can only detect limited 
crack size.
    The FAA does not concur. The FAA finds that accomplishment of the 
detailed inspection required by paragraph (a) of this AD, in 
conjunction with the detailed inspection required by paragraph (b)(1) 
of this AD and the modification required by paragraph (b)(2) of this 
AD, will ensure the integrity of the door and fuselage structure to 
which the hinge is attached. Therefore, no change to the final rule is 
necessary in this regard.
    Two commenters request that the FAA revise paragraph (a) of the 
NPRM to specify that operators will be given ``credit'' for having 
previously accomplished the proposed detailed visual inspection of the 
main deck cargo door hinge in accordance with a method approved by the 
appropriate Aircraft Certification Office (ACO) prior to the effective 
date of the final rule. One commenter states that operators who 
accomplished the subject inspection before the effective date of this 
AD should not be penalized by being forced to reinspect after the 
effective date of this AD.
    The FAA does not consider that a change to the final rule is 
necessary to give operators such credit. Operators are given credit for 
work previously performed by means of the phrase in the ``Compliance'' 
section of the AD that states, ``Required as indicated, unless 
accomplished previously.'' Therefore, in the case of this AD, if the 
required detailed inspection has been accomplished prior to the 
effective date of this AD in accordance with a method approved by the 
FAA, this AD does not require that it be repeated.
    One commenter requests that the detailed visual inspection required 
by paragraph (b)(1) of the NPRM be accomplished at the next ``C'' check 
after five years have elapsed since the airplane was converted from a 
passenger-to a cargo-carrying (``freighter'') configuration. The 
commenter also states that a ``C'' check would allow operators to 
accomplish the inspection during a heavy maintenance visit.
    The FAA does not concur. The FAA finds that accomplishment of the 
detailed inspection required by paragraph (b)(1) of this AD prior to or 
concurrently with requirements of paragraph (b)(2) of this AD (i.e., 
installation of a main deck cargo door hinge) will ensure the 
structural integrity of mating surfaces of the hinge. However, 
paragraph (g) of this AD does provide affected operators the 
opportunity to apply for an adjustment of the compliance time if data 
are presented to justify such an adjustment.
    One commenter requests that the detailed visual inspection required 
by paragraph (b)(1) of the NPRM apply only to airplanes that have been 
in service for five or more years since installation of the cargo door, 
because the likelihood of damage increases with time in service. The 
commenter states that the compliance time specified in paragraph (b) of 
the NPRM should start from the date that the modification was installed 
on the airplane.
    The FAA does not concur. The FAA finds that the potential for 
cracks in the hinge is primarily related to flight cycles (i.e., number 
of fuselage pressure cycles) and, to a lesser extent, calendar time. 
Therefore, the FAA has determined that the compliance time specified in 
paragraph (b) of this AD should be related to flight cycles, not 
calendar time. No change to the final rule is necessary in this regard.
    One commenter requests that the NPRM, Rules Docket 97-NM-234-AD, be 
revised to reference Kitty Hawk Service Bulletin KHA 727-004, Revision 
A, as an appropriate source of service information for accomplishing 
the detailed visual inspection required by paragraphs (a) and (b)(1) of 
the NPRM and the modification required by paragraph (b)(2) of that 
NPRM. The commenter states that this service bulletin has been 
submitted to the FAA for approval and should be approved by the FAA 
prior to the issuance of the NPRM.
    Another commenter states that it has developed and submitted to the 
FAA for approval a modification that segments the hinge on existing 
cargo converted airplanes and installs a segmented hinge on the new 
conversion. From this comment, the FAA infers that the commenter is 
requesting that the NPRM, Rules Docket 97-NM-233-AD, be revised to 
reference this modification as a terminating action for the 
requirements of paragraphs (b) and (c) of that NPRM.
    The FAA concurs with the commenters' requests to reference service 
bulletins that constitute compliance with the requirements of 
paragraphs (b) and (c) of ADs, Rules Dockets 97-NM-233-AD and 97-NM-
234-AD. The FAA has reviewed and approved Kitty Hawk Service Bulletin 
KHA 727-004, Revision B, dated March 3, 1999, as opposed to the 
Revision A mentioned by one of the commenters. The FAA also has 
reviewed and approved Aeronautical Engineers Incorporated (AEI) Service 
Bulletin AEI01-01, Revision B, dated October 26, 2001. These service 
bulletins describe the following procedures:
    1. Visual inspection of all areas of the hinge for cracks or other 
signs of damage;
    2. Inspection of the mating surfaces of the main deck cargo door 
hinge and the external doubler for discrepancies (i.e., scratches, 
gouges, or corrosion);
    3. Repair of any crack, damage, or discrepancy, if necessary; and
    4. Installation of a main deck cargo door hinge that complies with 
the applicable requirements of CAR part 4b, including fail-safe 
requirements.
    In addition, the FAA has reviewed and approved Federal Express E.O. 
Revision Record 7-5230-7-5000, Revision B, release date December 18, 
2001, and Pemco Service Bulletin 727-53-0006, Revision 1, dated 
December 4, 2001. The procedures in these service bulletins are similar 
to those described in AEI Service Bulletin AEI01-01, Revision B, and 
Kitty Hawk Service Bulletin KHA 727-004, Revision B.
    The FAA finds that accomplishment of the actions specified in the 
four service bulletins described previously constitutes compliance with 
the requirements of paragraphs (b) and (c) of final rules, Rules 
Dockets 97-NM-232-AD, 97-NM-233-AD, 97-NM-234-AD, and 97-NM-235-AD; as 
applicable. Therefore, the FAA has revised those final rules to include 
a new note that references the subject service bulletins as a source of 
service information for accomplishing the actions required by 
paragraphs (b) and (c) of those final rules; as applicable.
    One commenter requests that a subparagraph be added to paragraph 
(b) of the NPRM to require that the detailed visual inspection required 
by paragraph (b)(1) of the NPRM be accomplished just prior to final 
hinge installation during the process of converting an airplane from a 
passenger- to cargo-carrying (``freighter'') configuration. The 
commenter states that this revision would eliminate its concerns about 
the installation defects that could cause future problems.
    The FAA does not concur. The FAA finds that any FAA-approved 
corrective action that satisfies the requirements of paragraph (b)(2) 
of this AD will also address the installation of a hinge during the 
process of converting a Boeing Model 727 series airplane from a 
passenger- to a cargo-carrying (``freighter'') configuration. Normally,

[[Page 53427]]

good manufacturing procedures during production should preclude the 
necessity for the inspection. No change to the final rule is necessary 
in this regard.
    One commenter notes that paragraph (b)(2) of the NPRM references 
CAR part 4b. The commenter asks, ``If the FAA, as evidenced by the 
awarding of an STC, certified the cargo door hinge, how can the current 
hinge not meet CAR requirements?'' The commenter also asks, ``Wasn't 
the original STC determined to be in compliance with those 
requirements? If so, what specifically needs to be done to eliminate 
the FAA safety concerns about hinges that do not appear to have a 
problem?'' The commenter suggests that paragraph (b)(2) of the NPRM be 
revised to require STC holders to design and make available an 
acceptable replacement hinge. The commenter states that this suggestion 
should be a condition for STC holders to continue to hold their STC 
approval.
    From the commenter's questions, the FAA infers that the commenter 
believes a main deck cargo door hinge with an approved STC is compliant 
with the requirements of CAR part 4b. The FAA finds that clarification 
is necessary. Generally, there is a presumption by operators that 
demonstrations of compliance with the requirements of CAR part 4b is a 
prerequisite for granting an STC. However, the applicant for any design 
approval is responsible for compliance with all applicable FAA 
regulations. The FAA has the discretion to review or otherwise evaluate 
the applicant's compliance to the degree the FAA considers appropriate 
in the interest of safety. The normal certification process allows for 
the review and approval of data by FAA designees. Consequently, the FAA 
office responsible for the certification of an airplane or modification 
to an airplane or an aeronautical appliance may not review all details 
regarding compliance with the appropriate regulations. As explained in 
the NPRM, the FAA has conducted design reviews and airplane inspections 
and has identified a potential unsafe condition that relates to the 
main deck cargo door hinge.
    In addition, the FAA does not concur with the commenter's request 
to revise paragraph (b)(2) of the AD to require STC holders to design 
and make available an acceptable replacement hinge. The FAA finds that 
such a requirement is unnecessary, because as previously discussed, the 
FAA has revised this final rule to include a new note that references 
the applicable STC holder's service bulletin as a source of service 
information for accomplishing the actions required by paragraphs (b) 
and (c) of this final rule.

Main Deck Cargo Door Systems

    One commenter requests that the compliance time for accomplishing 
the Airplane Flight Manual (AFM) revisions required by paragraph (d) of 
the NPRM be revised from ``within 60 days after the effective date of 
this AD'' to ``within 60 days after submission of the procedures to the 
FAA.'' The commenter states that operators should be able to design 
revisions to the AFM within the proposed 60 days. However, the 
commenter believes that the Atlanta ACO will not be able to approve 
every one of those AFM Supplements within that time period.
    The FAA does not concur. Since the release of the NPRM, some of the 
affected STC holders and operators have already developed AFM 
procedures acceptable to the FAA. The FAA finds that a 60-day 
compliance time is sufficient to allow the remaining operators and STC 
holders to develop revisions to the applicable AFMs and their 
supplements and for the Atlanta ACO to review and approve those AFM 
revisions.
    One commenter submitted procedures for accomplishing the 
requirements of paragraph (d) of NPRM, Rules Docket 97-NM-232-AD. The 
commenter requests that the FAA approve those procedures prior to 
issuance of the final rule and include those procedures in the final 
rule. The commenter states that it has completed a Safety Assessment 
Report for each of the door configurations currently operating in its 
fleet. The commenter believes the results of the report demonstrate 
that it is ``extremely improbable'' that the door will inadvertently 
open in flight for any reason. Although the analysis does not 
demonstrate compliance with the ``extremely improbable'' standard, the 
commenter states that for a limited time of 36 months the door system, 
as installed, provides a sufficient level of safety to be considered 
acceptable with no modification or change in operational procedures.
    The FAA partially concurs. In order to gain a better understanding 
of the referenced Safety Assessment Report, the FAA had a telecon with 
the commenter on February 19, 2000, to discuss a series of questions, 
which were provided to the commenter prior to the telecon, about the 
report. (The minutes of this telecon are included in Rules Docket 97-
NM-232-AD.) In addition to the information that it provided at the 
telecon, the commenter also provided an analysis of the Safety 
Assessment Report in a letter, dated February 16, 2000, and a revised 
table of the Safety Assessment Report in a letter, dated March 6, 2000. 
The analysis in these letters provided, for a variety of failure modes, 
the probability of the main deck cargo door not being in the closed, 
latched, and locked condition prior to dispatch. The analysis showed 
that the warning systems of the main deck cargo door and the means to 
prevent pressurization if the door is not closed, latched, and locked, 
only meet some of the requirements of CAR Sec. 4b.606 and criteria 
specified in FAA memorandum, dated March 20, 1992 (referenced in the 
preamble of the NPRM). The commenter also provided Revision 16 of its 
Boeing B-727 Flight Manual, which further clarifies a change in the 
procedures for verifying that the main deck cargo door is closed, 
latched, and locked.
    In light of the clarification provided by the commenter, the FAA 
concurs that the procedures submitted by the commenter provide an 
adequate level of safety until the requirements of paragraph (e) of 
this AD have been accomplished, considering the level of probability of 
occurrence of certain failures of the warning systems of the main deck 
cargo door and strict adherence to the door checking procedures and 
associated training requirements. Since issuance of the NPRM, the FAA 
has reviewed and approved Federal Express Service Bulletin FX727-2001-
5230-01, dated July 30, 2001, which describes procedures for ensuring 
that the main deck cargo door is closed, latched, and locked prior to 
dispatch. Accomplishment of these actions constitutes compliance with 
the requirements of paragraph (d) of final rule, Rules Docket 97-NM-
232-AD. Therefore, the FAA has revised the final rule, Rules Docket 97-
NM-232-AD, to include a new note that references the subject service 
bulletin as a source of service information for accomplishing the 
actions required by paragraph (d) of that final rule.
    One commenter provided procedures for accomplishing the 
requirements of paragraph (d) of NPRM, Rules Docket 97-NM-233-AD, on 
airplanes modified in accordance with STC SA1368SO, on which a vent 
door has not been installed, and on airplanes modified in accordance 
with STC SA1797SO, on which a vent door has been installed. The 
commenter states that its procedures will ensure that the main deck 
cargo door is properly closed, latched, and locked prior to flight.
    From this comment, the FAA infers that the commenter is requesting 
that the FAA approve its procedures as an

[[Page 53428]]

acceptable means of compliance to the requirements of paragraph (d) of 
the final rule, Rules Docket 97-NM-233-AD. The FAA does not concur. The 
FAA finds that any proposed operating procedure must have sufficient 
validation and verification that the procedures are realistic and 
designed to minimize possible human error. The procedure also must 
provide for adequate checks and balances in the event the procedure is 
not strictly followed. In addition, the commenter did not provide any 
validation of the operating procedure or results of a safety analysis. 
However, the FAA may approve requests for an alternative method of 
compliance (AMOC) under the provisions of paragraph (g) of AD, Rules 
Docket 97-NM-233-AD, if sufficient data are submitted to substantiate 
that such a operating procedure would provide an acceptable level of 
safety.
    One commenter provided procedures for accomplishing the 
requirements of paragraph (d) of NPRM, Rules Docket 97-NM-234-AD. In 
support of its procedures, the commenter states, among other items, 
that an internal direct visual inspection of the latching and locking 
system is not possible on Model 727 series airplanes affected by that 
NPRM because the latching and locking systems are covered by a 
protective guard/cover that prevents direct viewing of these systems. 
Removing these covers would expose the latching and locking systems to 
possible foreign object damage (FOD) or damage from shifting freight. 
The commenter states that this condition is far more dangerous than a 
failure of the latching and locking systems. The commenter also states 
that most of the affected airplanes are equipped with flip up sill 
protectors, which further block the visibility of the bottom of the 
cargo door area (latch and lock area). The commenter concludes that a 
visual inspection of the latching and locking mechanisms is not 
appropriate for the airplane type and would create severe operational 
disruption with no benefit.
    The FAA concurs with the commenter's conclusion that a visual 
inspection of the latching and locking mechanisms is not appropriate 
for accomplishing the requirements of paragraph (d) of final rule, 
Rules Docket 97-NM-234-AD. The FAA notes that paragraph (d) of that 
final rule does not specifically require a visual inspection of the 
locking mechanisms of the main deck cargo door after the door is 
closed, as suggested by the commenter. Since issuance of the NPRM, the 
FAA has reviewed and approved Kitty Hawk Service Bulletin KHA 727-008, 
dated January 7, 2000, which describes procedures for ensuring that the 
main deck cargo door is closed, latched, and locked prior to dispatch. 
These procedures are identical to those procedures provided by the 
commenter. Accomplishment of these actions constitutes compliance with 
the requirements of paragraph (d) of final rule, Rules Docket 97-NM-
234-AD. Therefore, the FAA has revised final rule, Rules Docket 97-NM-
234-AD, to include a new note to reference the subject service bulletin 
as a source of service information for accomplishing the actions 
required by paragraph (d) of that final rule.
    One commenter states that the requirements for ``a means to prevent 
pressurization to an unsafe level'' and ``direct visual examination of 
all locks'' are not included in the certification basis of Model 727 
series airplanes and should not be required for the interim action.
    From this comment, the FAA infers that the commenter is referring 
to the interim actions required by paragraph (d) of the NPRM and to 
extracts from Appendix 1 of this AD, which sets forth the industry-
accepted criteria to which the outward opening doors must be shown to 
comply per paragraph (e) of the NPRM. The FAA does not concur. The 
commenter has misinterpreted the requirements of paragraph (d) of this 
AD. Paragraph (d) of this AD requires procedures to ensure that all 
power is removed from the main deck cargo door prior to dispatch and to 
ensure that the main deck cargo door is closed, latched, and locked 
prior to dispatch of the airplane. This paragraph does not specify or 
limit what means or actions would be acceptable to the FAA. Operators 
could submit a means to prevent pressurization to an unsafe level and 
direct visual inspection of the locks as possible ways to ensure that 
the main deck cargo door is secure, in accordance with paragraph (d) of 
this AD. In addition, to comply with paragraph (e) of this AD, the 
criteria specified in Appendix 1 of this AD must be applied, 
irrespective of the certification basis of the airplane. Therefore, no 
change to the final rule is necessary in this regard.
    One commenter requests that the proposed compliance time specified 
in paragraph (e) of the NPRM be revised from ``within 36 months after 
the effective date of this AD'' to ``at the next `C' check after the 
modifications are approved by the Manager, Atlanta ACO.'' The commenter 
states that such a compliance time would make everybody (i.e., 
designer, operator, and FAA) share responsibility for time delays 
encountered during the modification design and approval process.
    The FAA does not concur. Since issuance of the NPRM, the FAA has 
reviewed and approved two modifications (i.e., National Aircraft 
Services, Inc., (NASI) STC ST01438CH and Pemco STC ST01270CH) as 
acceptable means for compliance with the requirements of paragraph (e) 
of final rules, Rules Dockets 97-NM-232-AD and 97-NM-235-AD; as 
applicable. Therefore, the FAA has revised the final rules, Rules 
Dockets 97-NM-232-AD and 97-NM-235-AD, to include a new note to 
reference the applicable STC as a source of service information for 
accomplishing the requirements of paragraph (e) of those final rules. 
The FAA finds that a 36-month compliance time for accomplishing the 
action specified in paragraph (e) of those final rules is not only 
sufficient for the design of the corrective actions, but also provides 
adequate time for operators to schedule the installation within an 
interval of time that parallels a heavy maintenance visit. However, 
under the provisions of paragraph (g) of final rules, Rules Dockets 97-
NM-232-AD and 97-NM-235-AD, the FAA may approve requests for an 
adjustment of compliance times if data are submitted to substantiate 
that such an adjustment would provide an acceptable level of safety.

Main Deck Cargo Barrier

    One commenter requests that, before issuance of the final rule, 
industry and the FAA form a review team to find a way of lowering the 
costs associated with accomplishing the proposed installation of a 9g 
crash barrier. The commenter suggests that lower costs could be 
achieved by fixing the existing barrier (e.g., the loads could be 
spread by the addition of structural reinforcement attachment angles) 
or designing a new barrier. The commenter states that the Ventura 
Aerospace, Inc., cargo barrier STC ST00848LA, which is an approved 
means of compliance with the requirements of paragraph (f) of NPRMs, 
Rules Dockets 97-NM-233-AD, 97-NM-234-AD, and 97-NM-235-AD, is an 
adequate barrier; however, the parts and installation cost estimates 
for the installation in those NPRMs are too low. The commenter gave 
examples of various actions and associated work hours that would be 
necessary to accomplish the proposed installation of the Ventura 9g 
crash barrier.
    The FAA does not concur with the commenter that a review team is 
necessary, and that the cost estimates of NPRMs, Rules Dockets 97-NM-
233-AD, 97-NM-234-AD, and 97-NM-235-AD,

[[Page 53429]]

for accomplishing the installation of a main deck cargo barrier are too 
low. The FAA acknowledges that installation of a Ventura Aerospace, 
Inc., cargo barrier STC ST00848LA is an approved means of compliance 
with the requirements of paragraph (f) of final rules, Rules Dockets 
97-NM-233-AD, 97-NM-234-AD, and 97-NM-235-AD. However, the cost 
estimates in the subject NPRMs were not specifically for installation 
of the subject Ventura 9g crash barrier, but were for installation of a 
9g crash barrier that complies with the applicable requirements of CAR 
part 4b. The installation cost estimate of the NPRMs was provided to 
the FAA by Pemco based on the best data available to date.
    The FAA recognizes that, in accomplishing the requirements of any 
AD, operators may incur ``incidental'' costs in addition to the 
``direct'' costs. The cost analysis in AD rulemaking actions, however, 
typically does not include incidental costs, such as the time required 
to gain access and close up; planning time; or time necessitated by 
other administrative actions. Because incidental costs may vary 
significantly from operator to operator, they are almost impossible to 
calculate. Furthermore, because the FAA generally attempts to impose 
compliance times that coincide with operators' scheduled maintenance, 
the FAA considers it inappropriate to attribute the costs associated 
with aircraft ``downtime'' to the cost of the AD, because, normally, 
compliance with the AD will not necessitate any additional downtime 
beyond that of a regularly scheduled maintenance visit.

Public Meeting

    Several commenters request that the FAA hold a public meeting prior 
to the issuance of the final rule in the event that the FAA does not 
find their procedures acceptable for compliance with the requirements 
of paragraph (d) of the NPRM. The commenters state that such a meeting 
would provide a forum for productive face-to-face discussions similar 
to the process used by industry's B-727 Working Group.
    The FAA does not concur. As discussed previously, the FAA has 
accepted some of the procedures submitted by the commenters. Also, in 
consideration of the differing configurations of the main deck cargo 
door systems between the various affected STCs, a public meeting to 
discuss the AD may be significantly restricted in some cases because of 
the proprietary design and data issues. However, the FAA is available 
to discuss any particular proposal for procedures specific to the 
airplane configuration with each of the affected STC holders or 
operators. Further, the FAA may approve requests for an AMOC under the 
provisions of paragraph (g) of this AD if sufficient data are submitted 
to substantiate that such a procedure would provide an acceptable level 
of safety. Therefore, the FAA finds that no public meeting is 
necessary.

Issue Separate ADs

    One commenter requests that the NPRM be split into separate ADs for 
each issue--main deck cargo door hinge, main deck cargo door systems, 
and 9g crash barrier. The commenter states that multiple actions 
addressed by a single AD make managing the actions very unwieldy and 
complicated.
    The FAA does not concur. The FAA is not convinced that separate ADs 
for each issue would resolve the complexity of this AD. The FAA has 
determined that a less burdensome approach is to issue only one AD for 
each STC holder that addresses the potential unsafe conditions that 
relate to the main deck cargo door hinge, main deck cargo door systems, 
and main deck cargo barrier. In addition, operators have already 
initiated actions to accomplish the requirements of this AD without 
apparent complications.

ACO Approval

    One commenter requests that the actions required by the NPRM that 
must be accomplished in accordance with a method approved by the 
Manager, Atlanta ACO, be approved by the Manager, Transport Airplane 
Directorate. The commenter states that the affected Boeing Model 727 
series airplanes are not small airplanes, and that the approving 
authority should be someone in an ACO from the Transport Airplane 
Directorate who understands structural repairs of transport category 
airplanes.
    The FAA does not concur. Since the subject STCs were issued by the 
Atlanta ACO, that office has certificate responsibility for the 
airplanes affected by this AD. The Atlanta ACO is most cognizant of the 
design details of the subject STCs, and therefore, more able to address 
each operator's specific issues for complying with paragraph (d) of 
this AD. The Manager of the Atlanta ACO will coordinate the review of 
the submittals with the Transport Airplane Directorate, which has 
established a team consisting of members from several ACOs to review 
all requests in accordance with paragraphs (b)(1), (b)(2), (c), (d), 
(e), and (f) of this AD.

Principal Maintenance Inspector (PMI) or Principal Operations 
Inspector (POI) Approval

    One commenter requests that the FAA allow the individual operator's 
local PMI or POI to approve the AFM procedures for ensuring that the 
main deck cargo door is closed, latched, and locked required by the 
NPRM, or provide an option in the NPRM that allows the procedures to be 
added to the airplane operator manual (AOM), if applicable. The 
commenter states that such approval would ensure that the approval 
process is accomplished quickly.
    The FAA does not concur. Paragraph (d) of this AD requires 
comprehensive engineering evaluation in consideration of the applicable 
requirements of CAR part 4b and the criteria specified in Appendix 1 of 
this AD. Consequently, the evaluation must be conducted by the Manager, 
Atlanta ACO, to determine an acceptable level of safety. The PMI or POI 
for the air carrier is normally not familiar with all the design 
considerations provided by the requirements of CAR part 4b and Appendix 
1 of this AD.

Cost

    One commenter requests that an industry/FAA team determine a less 
costly method to fix the existing barriers to satisfy the FAA's 
concerns. For example, the loads could be spread by the addition of 
structural reinforcement attachment angles. The commenter states that 
replacing the barrier is an extreme measure, and that there must be 
some kind of structural additions that could be made to the existing 
barrier to make it acceptable at a much lower cost.
    The FAA partially concurs. The STC holders and operators are 
certainly free to form an industry team to find common solutions. 
However, the FAA's reason for participation would not be for the 
purpose of developing a less costly design, but rather to ensure that 
the final design is compliant with the applicable regulations.
    One commenter requests that the FAA require STC holders to design 
the correction for the NPRM as a warranty issue. The commenter states 
that small operators, who do not have in-house engineering capability, 
will be at a great disadvantage when attempting to design remedies for 
this NPRM. The commenter also states that this NPRM places a 
substantial financial and operational burden on ``small entities'' just 
from the standpoint of not having a remedy already designed and 
approved.
    The FAA does not concur. Any warranty agreements between the

[[Page 53430]]

operator and an STC holder are not the responsibility of the FAA. The 
burden on small entities is addressed in the Regulatory Flexibility 
Analysis and Summary and Regulatory Sections of this AD.

Descriptive Language of Preamble

    One commenter states that it found the following four factual 
inaccuracies in the NPRM, Rules Docket 97-NM-232-AD, and requests that 
the FAA correct them.
    1. The commenter notes that paragraph six under the heading ``Main 
Deck Cargo Door System'' reads, ``* * * However, the FAA is aware of 
two events in which the main deck cargo door opened during flight. 
These events occurred on FedEx passenger/freighter conversion STC's in 
October 1996, and March 1995.'' The commenter states that it does not 
have any information or records indicating that the main deck cargo 
door opened in flight in October 1996 or March 1995. In the March 1995 
incident, the commenter contends that the door, upon landing, was found 
to be closed and locked, and that the lock bar was found to be in the 
unlocked position. The commenter states that it found a control valve 
electrical connection of the main deck cargo door to be disconnected, 
and that the door operated normally once it was reconnected.
    2. The commenter disagrees with the sentence under the heading ``1. 
Indication System'' in the preamble of the NPRM that reads, ``Both of 
these lights indicate the status of the cargo door latch and lock 
positions, but do not indicate either the door open or closed status.'' 
The commenter states that its system does monitor and indicate the door 
closed status. If the door closed switch is not depressed, the light 
will stay illuminated, even if the door lock latches have rolled and 
the lock bar has moved into place.
    3. The commenter notes that paragraph two under the heading ``2. 
Means to Visually Inspect the Locking Mechanism'' reads, ``* * * 
Although an indicator flag attached to the lock shaft can be seen 
through the view port when the shaft is in the ``locked'' position, a 
failure between the shaft and the pins could go undetected, because 
this flag is attached to the lock shaft and not the actual lock pins.''
    The commenter states that the flag is attached to the lock bar on 
Model 727-100 series airplanes. The lock plates are also bolted 
directly to the lock bar (no linkages). Therefore, the commenter 
contends that both the flag and lock plates become integrated parts of 
the lock bar.
    In addition, the commenter states that the flag is attached to a 
lock pin on Model 727-200 series airplanes, and that the lock pin 
linkage does not have springs or an actuator attached to it. The 
commenter also contends that movement would have to be transmitted 
through the lock bar. The commenter further states that the stress 
analysis for Model 727-200 series airplanes shows high margins of 
safety in yield, bending, and shear for the locking hinges and 
fasteners.
    4. The commenter notes that paragraph three under the heading ``3. 
Means to Prevent Pressurization to an Unsafe Level'' in the preamble of 
the NPRM reads, ``Boeing 727-100 airplanes modified in accordance with 
the subject STC's have no means of preventing pressurization in the 
event that the main deck cargo door is not closed, latched, and locked, 
and therefore, have a higher risk of a cargo door opening while the 
airplane is in flight and possible loss of the airplane.'' The 
commenter states that the system used on Model 727-100 series airplanes 
has a relay that drives the ground venturi system, which in turns opens 
the outflow valve when the main deck cargo door is not closed and 
locked, hence pressurization is not possible.
    For item 1 above, the FAA partially agrees with the commenter. In 
the preamble of the NPRM, Rules Docket 97-NM-232-AD, the FAA 
incorrectly referenced October 1996 as a date of a door opening event. 
The correct date is December 9, 1994. The pilots' report (which is 
included in Rules Docket 97-NM-232-AD) on this event states that 
shortly after takeoff the warning light for the main deck cargo door 
illuminated. Following the open in-flight procedures for the main deck 
cargo door, the flight crew safely returned the airplane to the 
departure airport. The post-flight inspection revealed that the main 
deck cargo door opened approximately two feet. Also, in reference to 
the March event where the commenter states that the door did not open 
in flight, a verbal report (i.e., ``FAA Freighter Conversion STC Review 
Report Number 2, dated October 16-18, 1996,'' which is included in 
Rules Docket 97-NM-232-AD) from the maintenance organization of the 
commenter's company states that the main deck cargo door was unlocked, 
and that the door was flush with the exterior of the airplane. The 
report on this latter event states that, following departure and at 
17,000 feet, the warning light of the main deck cargo door came on 
followed by cabin altitude climbing. While it is not clear to the FAA 
whether or not the main deck cargo door opened while the airplane was 
in flight, the condition for possible door opening (i.e., rotation of 
the lock bar to the unlocked position in flight) did occur, which could 
have led to a door opening while the airplane is in flight. Therefore, 
the FAA has revised the ``Background'' Section (``Main Deck Cargo Door 
Systems'' subsection) in the preamble of final rule, Rules Docket 97-
NM-232-AD, to correct the date of the subject event.
    For items 2. and 4. above, the FAA agrees with the commenter's 
correction to items 2. and 4. above and has revised the ``Background'' 
Section (``Indication Systems'' and ``Means to Prevent Pressurization 
to an Unsafe Level'' subsections) in the preamble of final rule, Rules 
Docket 97-NM-232-AD, accordingly. However, we find that the correction 
to item 2. does not alleviate the unsafe design features that were 
single point failures in the door control/outflow valve interface, 
which could result in the valve not sensing and responding to an unsafe 
door condition. With the current design, it is possible that the 
outflow valve or associated controllers may not perform their intended 
function when utilized for the purpose of preventing pressurization of 
the airplane in the event of an unsecured door. This condition could 
result in cabin pressurization forcing an unsecured door open while the 
airplane is in flight and possible loss of the airplane.
    Further, we find that the correction to item 4. does not alleviate 
the safety concern regarding the design feature where ALL three 
conditions (i.e., door closed, latched, and locked) are not directly 
monitored. If a sequencing error caused the door to latch and lock 
without being fully closed, the subject indication system, as designed, 
would not directly alert the door operator or the flight engineer of 
this condition. As a result, the airplane could be dispatched with an 
unsecured main deck cargo door, which could lead to the cargo door 
opening while the airplane is in flight and possible loss of the 
airplane.
    For item 3. above, the FAA does not concur that the attachment of 
the ``flag'' to the lock bar on Model 727-100 series airplanes is 
sufficient to indicate the position of the lock pins, even though the 
lock pins are bolted to the lock bar. The FAA has determined that any 
failure condition of a lock pin would not be detected when observing 
the position of the flag through the view port.

[[Page 53431]]

Explanation of Change to Unsafe Condition

    To more accurately reflect the identified unsafe condition of this 
AD, the FAA has revised the final rule where applicable to read, ``to 
prevent structural failure of the main deck cargo door hinge or failure 
of the cargo door system, which could result in the loss or 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; and to prevent failure of the main 
deck cargo barrier during an emergency landing, which could injure 
occupants.''

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Regulatory Evaluation Summary

    This analysis estimates the costs of AD, Rules Docket 97-NM-234-AD, 
that requires installation of a fail-safe hinge; redesigned warning and 
power control systems of the main deck cargo door; and a 9g crash 
barrier on Boeing Model 727 series airplanes that have been modified in 
accordance with certain STCs held by Kitty Hawk Air Cargo. Since the 
publication of the NPRM, Kitty Hawk has been purchased by Stambaugh 
Aviation Services. As discussed above, the FAA has determined that:
    1. The main deck cargo door hinge is not fail-safe;
    2. Certain control systems of the main deck cargo door do not 
provide an adequate level of safety; and
    3. The 9g crash barrier is not structurally adequate during a minor 
crash landing.
    It is estimated that four U.S.-registered Boeing Model 727 series 
airplanes will be affected by this AD. The four airplanes are all 
operated by one entity, American International Airways. The following 
discussion addresses, in sequence, the actions in the Rules Docket 97-
NM-234-AD and the estimated cost associated with each of these actions. 
An analysis of the estimated cost is also available in the Rules Docket 
97-NM-234-AD.

1. Main Deck Cargo Door Hinge

    Since unsafe conditions have been identified that are likely to 
exist or develop on other modified Boeing Model 727 series airplanes, 
paragraph (a) of this AD requires, prior to the accumulation of 4,000 
flight cycles since accomplishment of the installation of the main deck 
cargo door, or within 250 flight cycles after the effective date of 
this AD, whichever occurs later, a detailed inspection of the external 
surface of the main deck cargo door hinge to detect cracks. Based on 
data provided by other STC holders, the FAA estimates that this 
inspection will take 2 hours. At an hourly wage rate of $60, the cost 
of per airplane is $120 and the estimated cost for the fleet of 4 
airplanes is $480.
    Paragraph (b)(1) of the AD requires, within 36 months or 4,000 
cycles after the effective date of this AD, whichever occurs first, a 
detailed inspection of the mating surfaces of both the hinge and the 
door skin, and the hinge and external fuselage doubler underlying the 
hinge. The FAA estimates that compliance with this inspection will take 
200 work hours, at a cost of $12,000 per airplane, or $48,000 for the 
affected fleet.
    Paragraph (b)(2) of the AD requires installation of a fail-safe 
door hinge. The compliance time for this installation is also 36 months 
or 4,000 cycles after the effective date of this AD, whichever occurs 
first. Kitty Hawk estimated that the cost to design and certificate 
such a hinge will be $50,000; no parts for a fail-safe door hinge will 
be required; and the (labor) cost of the modification will be $15,000. 
Total compliance cost for this provision for the affected fleet of 4 
airplanes is estimated to be $110,000, undiscounted.
    Paragraph (c) of the AD requires that, if any crack or discrepancy 
is detected during the inspection required by paragraph (a) or (b)(1) 
of the AD, a repair must be made prior to further flight. The cost of 
this repair is not attributable to this AD.
    The FAA assumes that installation of the main deck cargo door hinge 
(paragraph (b)(2) of this AD) will be accomplished at the same time as 
the detailed inspection of fastener holes (paragraph (b)(1) of this 
AD). It is also assumed that the affected operator will perform these 
two activities uniformly throughout the 36-month compliance time. 
Finally, it is assumed that the certification cost for the main deck 
cargo door hinge will be incurred within the first 6 months after the 
effective date of this AD. Consequently, the cost to comply with 
paragraphs (a) through (c) of this AD, over the 36-month compliance 
time, is estimated at $158,000, undiscounted, or $145,000 discounted to 
present value.

2. Main Deck Cargo Door Systems

    Work on the door systems relates to paragraphs (d) and (e) of the 
AD. Paragraph (d) of the AD requires, within 60 days after the 
effective date of this AD, the revising of the Limitations Section of 
the FAA-approved AFM Supplement to provide the flight crew with 
procedures for ensuring that all power is removed from the main deck 
cargo door prior to dispatch of the airplane, and that the main deck 
cargo door is closed, latched, and locked prior to dispatch of the 
airplane. In addition, paragraph (d) of the AD requires the 
installation of any associated placards.
    The FAA assumes that Boeing Model 727 series airplanes, converted 
under a Kitty Hawk STC, will have an acceptable pressurization vent 
door installed, which could be used by operators to visually determine 
whether the vent is in the proper position prior to dispatch, 
indicating that the door is closed, latched, and locked. The FAA 
estimates that this activity will take no more than 30 minutes. 
Assuming that each affected airplane flies one flight per day, 260 days 
per year, the estimated cost per inspection is $30, or $7,800 per 
airplane, per year, until the door system is changed. This results in 
an estimated total cost of $94,000 for the affected airplanes, over the 
36-month compliance time.
    Paragraph (e) of this AD requires, within 36 months after the 
effective date of the AD, incorporation of redesigned main deck cargo 
door systems. Kitty Hawk estimates that the development and 
certification of the system will cost $175,000. Modification parts are 
estimated to cost $38,000 per airplane, and labor costs are estimated 
to be $23,500 per airplane. The FAA assumes that operators will 
incorporate redesigned main deck cargo door systems during regularly 
scheduled maintenance. (Kitty Hawk indicated that any lost revenue due 
to additional down time should be attributed to the installation of the 
9g crash barrier, discussed below.) The total cost of incorporating 
redesigned main deck cargo door systems, including certification, 
parts, and labor is estimated to be $421,000 over the 36-month 
compliance time.
    The total estimated cost to comply with the requirements for the 
main deck cargo door systems is estimated to be $514,600 undiscounted, 
or $472,000, discounted to present value.

3. 9g Crash Barrier

    Paragraph (f) of this AD requires, within 36 months or 4,000 flight 
cycles after the effective date of the AD,

[[Page 53432]]

whichever occurs first, installation of a main deck cargo barrier that 
complies with the applicable requirements of CAR part 4b. Ventura 
Aerospace holds a STC for an approved 9g crash barrier, and the FAA 
expects that operators whose airplanes have been modified in accordance 
with the KittyHawk STC will purchase 9g crash barrier kits from Ventura 
Aerospace. In response to the one public comment on the economic 
analysis of the NPRM, and based on new data, there was an increase in 
the cost estimate for the Ventura 9g crash barrier in this final 
regulatory evaluation from that provided in the NPRM. The cost of a 
Ventura barrier kit is $67,000, while labor costs (to install the 
barrier) are estimated at $33,000 per airplane (for 550 hours of work). 
Also, while the barrier is installed, an affected airplane is expected 
to be out of service for 7 additional days, at an estimated (out-of-
service) cost of $15,000 per day. The commenter estimated the cost per 
airplane, for the Ventura 9g barrier, at $193,500. With the new data, 
the FAA estimates the cost per airplane, for the Ventura barrier, at 
$205,000.
    The FAA assumes that operators will install 9g crash barriers 
uniformly over the 36-month compliance time. The total undiscounted 
cost of this requirement is estimated to be $820,000, or $716,000 
discounted to present value.

4. AMOC and Special Flight Permits

    Paragraph (g) of the AD allows an AMOC or adjustment of compliance 
time that provides an acceptable level of safety if approved by the 
Manager of the Atlanta ACO. The FAA is unable to determine the cost of 
an AMOC, but assumes that it will be less than the cost of complying 
with the provisions in paragraphs (a) through (f) of the AD.
    Paragraph (h) of the AD allows special flight permits in accordance 
with the regulations to operate an affected airplane to a location 
where the requirements of the AD could be accomplished.

5. Total Cost of the AD

    The FAA estimates the total compliance cost of this AD to be $1.5 
million, undiscounted, or $1.3 million discounted to present value.

Regulatory Flexibility Analysis

    The Regulatory Flexibility Act (RFA) of 1980 establishes ``as a 
principle of regulatory issuance that agencies shall endeavor, 
consistent with the objective of the rule and of applicable statutes, 
to fit regulatory and informational requirements to the scale of the 
business, organizations, and governmental jurisdictions subject to 
regulation.'' To achieve that principle, the RFA of 1980 requires 
agencies to solicit and consider flexible regulatory proposals and to 
explain the rationale for their actions. The RFA of 1980 covers a wide-
range of small entities, including small businesses, not-for-profit 
organizations, and small governmental jurisdictions.
    Agencies must perform a review to determine whether a proposed or 
final rule will have a significant economic impact on a substantial 
number of small entities. If the determination is that the rule will 
have such an impact, the agency must prepare a regulatory flexibility 
analysis as described in the RFA in 1980. However, if an agency 
determines that a proposed or final rule is not expected to have a 
significant economic impact on a substantial number of small entities, 
Section 605(b) of the RFA of 1980 provides that the head of the agency 
may so certify. The certification must include a statement providing 
the factual basis for this determination, and the reasoning should be 
clear.
    The FAA conducted the relevant assessment of this AD, and 
determined that it will not have a significant impact on a substantial 
number of small entities. Only one operator, American International 
Airways, will be affected by this AD; and that operator is not a small 
entity (it employees more than 1,500 people). Consequently, the FAA 
certifies that this AD will not have a significant economic impact on a 
substantial number of small entities.

Unfunded Mandates Analysis

    The Unfunded Mandates Reform Act of 1995 (the Act), enacted as 
Public Law 104-4 on March 22, 1995, is intended, among other things, to 
curb the practice of imposing unfunded Federal mandates on State, 
local, and tribal governments.
    Title II of the Act requires each Federal agency to prepare a 
written statement assessing the effects of any Federal mandate in a 
proposed or final agency rule that may result in an expenditure of $100 
million or more (adjusted annually for inflation) in any one year by 
State, local, and tribal governments, in the aggregate, or by the 
private sector. Such a mandate is deemed to be a ``significant 
regulatory action.''
    This AD does not contain such a mandate. Therefore, the 
requirements of Title II of the Act do not apply.

Federalism Implications

    The regulations of this AD will 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, in 
accordance with Executive Order 13132, it is determined that this AD 
will not have sufficient federalism implications to warrant the 
preparation of a federalism assessment.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:


    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

2002-16-21  Boeing: Amendment 39-12860. Docket 97-NM-234-AD.

    Applicability: Model 727 series airplanes that have been 
converted from a passenger-to a cargo-carrying (``freighter'') 
configuration in accordance with Supplemental Type Certificate (STC) 
ST00015AT; 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 structural failure of the main deck cargo door hinge 
or failure of the cargo door system, which could result in the loss 
or 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; and to prevent 
failure of the main deck cargo barrier during an emergency landing, 
which could injure occupants; accomplish the following:

[[Page 53433]]

Actions Addressing the Main Deck Cargo Door Hinge

    (a) Prior to accumulation of 4,000 flight cycles since 
accomplishment of the installation of the main deck cargo door, or 
within 250 flight cycles after the effective date of this AD, 
whichever occurs later, perform a detailed inspection of the 
external surface of the main deck cargo door hinge (both fuselage 
and door side hinge elements) to detect cracks.

    Note 2: For the purposes of this AD, a detailed 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.''

    (b) Within 36 months or 4,000 flight cycles after the effective 
date of this AD, whichever occurs first, accomplish paragraphs 
(b)(1) and (b)(2) of this AD.
    (1) Perform a detailed inspection of the mating surfaces of both 
the hinge and the door skin and external fuselage doubler underlying 
the hinge to detect cracks or other discrepancies (e.g., double or 
closely drilled holes, corrosion, chips, scratches, or gouges). The 
detailed inspection shall be accomplished in accordance with a 
method approved by the Manager, Los Angeles Aircraft Certification 
Office (ACO), FAA. The requirements of this paragraph may be 
accomplished prior to or concurrently with the requirements of 
paragraph (b)(2) of this AD.
    (2) Install a main deck cargo door hinge that complies with the 
applicable requirements of Civil Air Regulations (CAR) part 4b, 
including fail-safe requirements, in accordance with a method 
approved by the Manager, Los Angeles ACO.
    (c) If any crack or discrepancy is detected during the detailed 
inspection required by either paragraph (a) or (b)(1) of this AD, 
prior to further flight, repair in accordance with a method approved 
by the Manager, Los Angeles ACO.

    Note 3: Accomplishment of the actions in accordance with Kitty 
Hawk Service Bulletin KHA 727-004, Revision B, dated March 3, 1999, 
constitutes compliance with the requirements of paragraphs (b) and 
(c) of this AD.

Actions Addressing the Main Deck Cargo Door Systems

    (d) Within 60 days after the effective date of this AD, revise 
the Limitations Section of the FAA-approved Airplane Flight Manual 
(AFM) Supplement by inserting therein procedures to ensure that the 
main deck cargo door is closed, latched, and locked prior to 
dispatch of the airplane, and install any associated placards. The 
AFM revision procedures and installation of any associated placards 
shall be accomplished in accordance with a method approved by the 
Manager, Los Angeles ACO.

    Note 4: Accomplishment of the actions in accordance with Kitty 
Hawk Service Bulletin 727-008, dated January 7, 2000, constitutes 
compliance with the requirements of paragraph (d) of this AD.

    (e) Within 36 months after the effective date of this AD, 
incorporate redesigned main deck cargo door systems (e.g., power 
control, view ports, and means to prevent pressurization to an 
unsafe level if the main deck cargo door is not closed, latched, and 
locked), including any associated procedures and placards, that 
comply with the applicable requirements of CAR part 4b and criteria 
specified in Appendix 1 of this AD; in accordance with a method 
approved by the Manager, Los Angeles ACO.

    Note 5: The design data submitted for approval should include a 
Systems Safety Analysis and Instructions for Continued Airworthiness 
that are acceptable to the Manager, Los Angeles ACO.

Actions Addressing the Main Deck Cargo Barrier

    (f) Within 36 months or 4,000 flight cycles after the effective 
date of this AD, whichever occurs first, install a main deck cargo 
barrier that complies with the applicable requirements of CAR part 
4b, in accordance with a method approved by the Manager, Los Angeles 
ACO.

    Note 6: The maximum main deck total payload that can be carried 
is limited to the lesser of the approved cargo barrier weight limit, 
weight permitted by the approved maximum zero fuel weight, weight 
permitted by the approved main deck position weights, weight 
permitted by the approved main deck running load or distributed load 
limitations, or approved cumulative zone or fuselage monocoque 
structural loading limitations (including lower hold cargo).


    Note 7: Installation of a Ventura Aerospace Inc. cargo barrier 
STC ST00848LA is an approved means of compliance with the 
requirements of paragraph (f) 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 Angeles Aircraft Certification 
Office (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 8: 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 
Secs. 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.

Effective Date

    (i) This amendment becomes effective on September 19, 2002.

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.''


[[Page 53434]]


    Issued in Renton, Washington, on August 6, 2002.
Vi Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.

[FR Doc. 02-20508 Filed 8-14-02; 8:45 am]
BILLING CODE 4910-13-P