[Federal Register Volume 64, Number 218 (Friday, November 12, 1999)]
[Proposed Rules]
[Pages 61554-61561]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-29473]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-232-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 727 Series Airplanes 
Modified in Accordance With Supplemental Type Certificate SA1767SO or 
SA1768SO

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 727 series 
airplanes that have been converted from a passenger to a cargo-carrying 
(``freighter'') configuration. This proposal would require, among other 
actions, installation of a fail-safe hinge, redesigned main deck cargo 
door warning and power control systems, and 9g cargo barrier. This 
proposal 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 the proposed 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, 
rapid decompression, and structural damage to the airplane; and to 
prevent failure of the main deck cargo barrier during an emergency 
landing, which could injure occupants.

DATES: Comments must be received by December 27, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-232-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location by appointment only between the hours of 9 a.m. and 3 p.m., 
Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Paul Sconyers, Associate Manager, 
Airframe and Propulsion Branch, ACE-117A, FAA, Small Airplane 
Directorate, Atlanta Aircraft Certification Office, One Crown Center, 
1895 Phoenix Boulevard, Suite 450, Atlanta, Georgia 30349; telephone 
(770) 703-6076; fax (770) 703-6097.

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 97-NM-232-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. 97-NM-232-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    Supplemental Type Certificate (STC) SA1767SO (held by FedEx) 
specifies a design for a main deck cargo door, associated cargo door 
cutout, and door systems. STC SA1768SO (held by FedEx) specifies a 
design for a Class ``E'' cargo interior with a cargo restraint barrier 
net. As discussed in notice of proposed rulemaking (NPRM), Rules

[[Page 61555]]

Docket No. 97-NM-09-AD [the final rule, AD 98-26-18, amendment 39-
10961, was published in the Federal Register on January 12, 1999 (64 FR 
1994)], 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's 
SA1767SO and SA1768SO and has identified several potential unsafe 
conditions. [Results of this design review are contained in ``FAA 
Freighter Conversion STC Review, Report Number 2, dated October 16-18, 
1996,'' hereinafter referred to as ``the Design Review Report,'' which 
is included in the Rules Docket for this NPRM.] 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 resulting loads). 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 part 4b.270, 
which requires, in part, that catastrophic failure or excessive 
structural deformation, which could adversely affect the flight 
characteristics of the airplane, is not probable after fatigue failure 
or obvious partial failure of a single 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 SA1767SO 
is supported by latches along the bottom of the door and one continuous 
hinge along the top. This single-piece hinge is considered a critical 
structural element for this STC. A crack that initiates and propagates 
longitudinally along the hinge line of the continuous hinge will 
eventually result in failure of the entire hinge, because there is no 
segmenting of the hinge to interrupt the crack propagation and 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.
    As discussed in the Design Review Report, an inspection of one 
Boeing Model 727 series airplane modified in accordance with STC's 
SA1767SO and SA1768SO 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.
    Since unsafe conditions have been identified that are likely to 
exist or develop on other products of this same type design, this 
proposed AD would require, within 250 flight cycles after the effective 
date of the AD, a one-time detailed visual inspection of the external 
surface of the main deck cargo door hinge (both fuselage and door side 
hinge elements) to detect cracks, and repair, if necessary. 
Accomplishment of this inspection will ensure that the subject 
airplanes are not in immediate risk of hinge failure.
    In addition, the proposed AD would require a detailed visual 
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 proposed AD also would require 
installation of a main deck cargo door hinge that complies with the 
applicable requirements of CAR part 4b, including fail-safe 
requirements. Accomplishment of this detailed visual inspection will 
ensure the integrity of the door and fuselage structure to which the 
hinge is attached. The proposed compliance time for this inspection and 
installation is within 36 months or 4,000 flight cycles after the 
effective date of this AD, whichever occurs first. The compliance time 
is based on the FAA's assessment of the reasonable amount of time to 
redesign, manufacture, and install a fail-safe hinge. This time is in 
consideration of the 18-month time period estimated by the Boeing 727 
industry working group, which includes operators, affected STC holders, 
and engineering organizations, to develop FAA-approved redesigns. These 
actions would be required to be accomplished in accordance with a 
method approved by the FAA.

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,

[[Page 61556]]

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 demonstrated 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 
AD's:
     For certain McDonnell Douglas Model DC-9 series airplanes: 
AD 89-11-02, amendment 39-6216 (54 FR 21416, May 18, 1989);
     For all Boeing Model 747 series airplanes: AD 90-09-06, 
amendment 39-6581 (55 FR 15217, April 23, 1990);
     For certain McDonnell Douglas Model DC-8 series airplanes: 
AD 93-20-02, amendment 39-8709 (58 FR 471545, October 18, 1993);
     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).
    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's SA1767SO and SA1768SO held by FedEx. The FAA identified a number 
of unsafe conditions with the main deck cargo door systems of these 
STC's. The FAA design review team determined that the design data of 
these STC's did not include a safety analysis of the main deck cargo 
door systems.
    As specified in the criteria contained in Appendix 1 of this AD, 
for powered lock systems on the main deck cargo door, it must be shown 
by safety analysis that inadvertent opening of the door after it is 
fully closed, latch, and locked is extremely improbable. 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. These events are 
referenced in the Design Review Report.
    For airplanes modified in accordance with STC's SA1767SO or 
SA1768SO, the FAA considers the following four specific design 
deficiencies of the main deck cargo door systems to be unsafe:

1. Indication System

    The main deck cargo door indication system for STC's SA1767SO and 
SA1768SO uses a warning light at the door operator's control panel and 
a light at the flight engineer's panel. 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. 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 and possible loss of the airplane.
    The light on the flight engineer's panel is labeled ``MAIN CARGO'' 
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. In addition, the flight engineer could miss such an 
indication by not scanning the panel. As a result, the pilots and 
flight engineer could be unaware of, or misinterpret, an unsafe 
condition and could fail to respond in the correct manner. 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.
    The main deck cargo door indication system of STC's SA1767SO and 
SA1768SO does not have a level of reliability that is considered 
adequate for safe operation. Many components are exposed to the 
environment during cargo loading operations and may be contaminated by 
precipitation, dirt, and grease, or damaged by foreign objects or cargo 
loading equipment. As a result, wires, switches, and relays can fail, 
jam, or short circuit and cause a loss of indication or a false 
indication to the door operator and flight crew. The design logic of 
the indication system (i.e., lights which extinguish when the door is 
locked) will, in the event of a single point failure that would 
extinguish the light, result in an erroneous ``safe'' indication 
regardless of actual door status.
    The design of STC's SA1767SO and SA1768S0 has a ``Press-to-Test'' 
red warning light on the control panel of the main deck cargo door 
located near the L-1 door. The design of the monitoring system of the 
main deck cargo door does not include separate lights to provide the 
door operator with door close, latch, and lock status. The electrical 
wiring design of the close, latch, and lock sensors of the door 
monitoring system are wired in parallel instead of in series. In 
parallel, two sensors could be sensing ``unsafe'' and the third sensor 
could be sensing ``safe.'' If this situation were to occur, the sensors 
would not illuminate the red warning light on the door control panel or 
at the flight engineer's panel. Therefore, the ``Press-to-Test'' 
feature is adequate to check the light bulb functionality, but is not 
adequate to check the cargo door closed, latched, and locked functions 
and status without annunciator lights for those three functions.

2. Means to Visually Inspect the Locking Mechanism

    The single view port of the main deck cargo door installed in 
accordance with STC SA1767SO is intended to allow the flight crew to 
conduct a visual

[[Page 61557]]

inspection of the door locking mechanism. This view port is used in 
conjunction with the door warning system and should provide a suitable 
``back-up'' in the event that the main deck cargo door warning system 
malfunctions.
    The door locking mechanism is an assembly comprised of multiple 
lock pins (one for each of the door latches) connected by linkages to a 
common lock shaft. 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. If such a failure goes undetected, the airplane may 
be dispatched with the main deck cargo door warning system inoperative 
and the door not fully closed, latched, and locked, which could lead to 
a main deck cargo door opening while the airplane is in flight and 
possible loss of the airplane. Therefore, the FAA finds that the 
subject view port is not a suitable back-up 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.

3. Means to Prevent Pressurization to an Unsafe Level

    Boeing 727-200 airplanes modified in accordance with STC SA1767SO 
are configured to utilize the existing fuselage pressurization outflow 
valve for the purpose of preventing pressurization of the airplane to 
an unsafe level in the event that the main deck cargo door is not 
closed, latched, and locked. The FAA design review of these modified 
Boeing 727-200 airplanes (documented in the Design Review Report) 
identified single point failures in the door control/outflow valve 
interface that could result in the valve not sensing and responding to 
an unsafe door condition. In addition, the FAA found no data to 
substantiate that the outflow valve location and size could prevent 
pressurization to an unsafe level.
    With the current design, it is possible that the outflow valve may 
not perform its 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.
    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.

4. Powered Lock Systems

    The main deck cargo door control system for STC SA1767SO 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 occurrence of an in-flight door opening 
event on airplanes modified in accordance with STC SA1767SO, as 
identified in the Design Review Report, indicates the likelihood that 
there may be latent and/or single point failures that 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 SA1767SO do not include a systems safety analysis to 
specifically identify these failure modes and do not show that an 
inadvertent opening is extremely improbable. The need for a system 
safety analysis is identified in the ATA Final Report and the FAA 
Memorandum.
    Since unsafe conditions have been identified that are likely to 
exist or develop on other products of this same type design, this 
proposed AD would require, within 60 days after the effective date, 
revising the Limitations Section of the FAA-approved Airplane Flight 
Manual (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; and 
installing any associated placards.
    In addition, the proposed AD would require, within 36 months after 
the effective date of the AD, incorporation of redesigned main deck 
cargo door systems (e.g., warning/monitoring, 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 design criteria of the ATA Final Report 
and the FAA Memorandum. Design data provided in support of the door 
systems redesign should include a Systems Safety Analysis and 
Instructions for Continued Airworthiness that are acceptable to the 
FAA. Accomplishment of the incorporation of redesigned main deck cargo 
door systems will prevent rapid decompression and/or structural damage 
to the airplane as a result of loss or opening of the cargo door while 
the airplane is in flight. The compliance time is based on the FAA's 
assessment of the reasonable amount of time to incorporate redesigned 
main deck cargo door systems. This time is in consideration of the 18-
month time period estimated by the Boeing 727 industry working group, 
which includes operators, affected STC holders, and engineering 
organizations, to develop FAA-approved redesigns.
    These actions would be required to be accomplished in accordance 
with a method approved by the FAA.

Cargo Restraint Barrier

    In order to ensure the safety of occupants during emergency landing 
conditions, the FAA first established in 1934, a set of inertia load 
factors used to design the structure for restraining items of mass in 
the fuselage. Because the airplane landing speeds have increased over 
the years as the fleet has transitioned from propeller to jet design, 
inertia load factors were changed as specified in CAR part 4b.260. 
Experience has shown that an airplane designed to this regulation has a 
reasonable probability of protecting its occupants from serious injury 
in an emergency landing. The 727 passenger airplane was designed to 
these criteria which specified an ultimate inertia load requirement of 
9g in the forward direction. These criteria were applied to the seats 
and structure restraining the occupants, including the flight crew, as 
well as other items of mass in the fuselage.
    When the 727 passenger airplane is converted to carry cargo on the 
main

[[Page 61558]]

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 be 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 1997 of a Boeing 727 modified in 
accordance with STC SA1767SO. The observations revealed that the design 
of the net restraint 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 
restraint 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 STC's 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 restraint barrier 
would not be capable of preventing serious injury to the occupants 
during an emergency landing event with the full allowable cargo load.
    Since unsafe conditions have been identified that are likely to 
exist or develop on other products of this same type design, this 
proposed AD would require installation of a main deck cargo barrier 
that complies with the applicable requirements of CAR part 4b. 
Accomplishment of the installation will prevent serious injury to the 
occupants in the event of an emergency landing. The proposed compliance 
time for the installation is within 36 months or 4,000 flight cycles 
after the effective date of the AD, whichever occurs first. This 
compliance time is based on the FAA's assessment of the reasonable 
amount of time to redesign, manufacture, and install the cargo barrier. 
This time is in consideration of the 18-month time period estimated by 
the Boeing 727 industry working group, which includes operators, 
affected STC holders, and engineering organizations, to develop and get 
FAA-approved redesigns.

Regulatory Evaluation Summary

    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    This analysis examines the cost of a proposed AD that would require 
the installation of a fail-safe hinge, redesigned main deck cargo door 
warning and power control systems, and a 9g cargo barrier on Boeing 
Model 727 series airplanes that have been modified in accordance with 
STC's held by FedEx. As discussed above, the FAA has determined 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 a minor crash landing.
    Approximately 117 U.S.-registered Boeing Model 727 series airplanes 
operated by FedEx would be affected by the proposed AD. The following 
discussion addresses, in sequence, the actions in this proposed 
rulemaking and the estimated cost associated with each of these 
actions. An analysis of the cost is also available in Rules Docket No. 
97-NM-232-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 the proposed AD would require, within 250 flight 
cycles after the effective date of this AD, a one-time detailed visual 
inspection to detect cracks of the external surface of the main deck 
cargo door hinge. FedEx estimates that this inspection would take 14 
work hours. At a mechanic's burdened labor rate of $60 per work hour, 
the cost per airplane would be $840, or $98,280 for FedEx's fleet of 
117 affected Boeing Model 727 series airplanes.
    Paragraph (b)(1) of the proposed AD would require, within 36 months 
or 4,000 cycles after the effective date of this AD, a detailed visual 
inspection of the mating surfaces of both the hinge and the door skin 
and external fuselage doubler underlying the hinge. The FAA estimates 
that compliance with this inspection would take 200 hours at an 
estimated cost of $12,000 per airplane, or $1.4 million for the 
affected fleet.
    Paragraph (b)(2) of the proposed AD would require installation of a 
fail-safe door hinge. The compliance time for this installation would 
also be 36 months or 4,000 cycles after the effective date of this AD. 
The estimated cost to design and certificate such a hinge is $45,000. 
FedEx estimates that parts for a fail-safe door hinge would cost 
$2,600, while installation would cost $11,520 per airplane for 192 
hours of labor. Parts and labor for 117 affected airplanes would be 
$1.7 million.
    Paragraph (c) of the proposed AD would require that, if any cracks 
or discrepancies are detected during the inspections required by 
paragraph (a) or (b)(1) of the proposed AD, repairs must be made prior 
to further flight. The cost of these repairs is not attributable to 
this proposed AD.
    For purposes of this analysis, the FAA assumes an effective date of 
July 1, 2000. The cost to comply with proposed paragraphs (a) through 
(c) over the 36-month compliance period is $3.2 million, or $2.8 
million discounted to present value. The FAA assumes that the 
installation of the main deck cargo door hinge [paragraph (b)(1)] would 
be accomplished at the same time as the detailed visual inspection of 
fastener holes [paragraph (b)(2)]. The FAA also assumes that FedEx 
would perform these two activities uniformly throughout the 36-month 
period. Finally, the certification cost for the main deck cargo door 
hinge would be incurred within the first 6 months after the effective 
date of this AD.

2. Main Deck Cargo Door Systems

    Paragraph (d) of the proposed AD would require, within 60 days 
after the effective date, revising 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

[[Page 61559]]

to dispatch of the airplane. In addition, paragraph (d) of the proposed 
AD would require the installation of any associated placards.
    FedEx assumes that an external inspection of the flushness of the 
cargo door, combined with an ``enhanced B-check'' would be an 
acceptable means to the FAA to ensure that the cargo door is secured 
prior to dispatch. Based on this assumption, FedEx estimates, before a 
redesigned door system is installed [see proposed paragraph (f) below], 
that it would take a mechanic 30 minutes to inspect for flushness of 
the main deck cargo door prior to dispatch. FedEx also estimates that 
there are 62 flights per day among the 117 affected airplanes and that 
these airplanes fly 260 days per year. The estimated cost per 
inspection would be $30, or $4,133 per airplane per year until the door 
system is changed. In addition, FedEx estimates that the setup costs 
for the daily inspection (i.e., procedure materials for the cadre of 
mechanics to perform the inspection and training requirements) would be 
$50,000.
    B-checks on FedEx Boeing Model 727 series airplanes occur 
approximately twice a year. FedEx estimates the incremental cost for 
maintenance during this ``enhanced B-check'' is $11,700 per year until 
the door system is changed.
    Paragraph (e) of the proposed AD would require, within 36 months 
after the effective date of this AD, incorporation of a redesigned main 
deck cargo door system. FedEx estimates that the development and 
certification of the system would cost $212,000. Modification parts 
would cost $110,000 per airplane and labor costs would be $34,560 per 
airplane. FedEx also estimates that 40 percent of the fleet would be 
modified during a scheduled maintenance visit. The remainder of the 
fleet would be out-of-service for an additional 4 days. Based on a 
lease rate of $6,100 per day, FedEx estimates that the cost of down 
time for the fleet would be $1.7 million over the 36-month period.
    Based on FedEx's assumption that a combination of an external 
inspection of cargo door flushness prior to dispatch and an 
``enhanced'' B-check every 6 months, the total cost would be $3.2 
million over 36 months. These activities would occur until 
incorporation of a redesigned door system. Again, the FAA assumes that 
the accomplishment of this incorporation would occur uniformly over the 
36-month period.
    The estimated cost for redesigned door systems for the fleet of 117 
affected airplanes would be $18.8 million, including $212,000 for 
design and certification costs and $1.7 million for additional down 
time. The total cost to comply with proposed requirements for the main 
deck cargo door system is $22.0 million, or $19.1 million, discounted 
to present value.

3. Main Deck Cargo Barrier

    Paragraph (f) of the proposed AD would require, within 36 months or 
4,000 flight cycles after the effective date of this AD, installation 
of a main deck cargo barrier that complies with the applicable 
requirements of CAR part 4b. FedEx estimates that development and 
certification of a 9g barrier would cost $94,500, while parts would 
cost $30,000 and labor would cost $23,040 per airplane.
    The FAA assumes that FedEx would install 9g barriers in their 
affected fleet uniformly over the 36-month compliance period. The total 
non-discounted cost would be $6.3 million, or $5.4 million discounted 
to present value.

4. Alternative Methods of Compliance (AMOC) and Special Flight Permits

    Paragraph (g) of the proposed AD would allow 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 it would be less than the 
cost of complying with the proposed provisions in paragraphs (a) 
through (f) of the proposed AD.
    Paragraph (h) of the proposed AD would allow special flight permits 
in accordance with the regulations to operate an affected airplane to a 
location where the requirements of the proposed AD could be 
accomplished.

5. Total Cost of the Proposed AD

    The FAA estimates that the total compliance cost of the proposed AD 
would be $31.6 million, or $27.3 million discounted to present value.
    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 requires agencies to 
solicit and consider flexible regulatory proposals and to explain the 
rationale for their actions. The RFA 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 it will, the 
Agency must prepare a regulatory flexibility analysis as described in 
the RFA. 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 provides that the 
head of the agency may so certify and a regulatory flexibility analysis 
is not required. The certification must include a statement providing 
the factual basis for this determination, and the reasoning should be 
clear.
    Only one operator, FedEx, is affected by this proposed AD. FedEx is 
not a small entity. Pursuant to the Regulatory Flexibility Act, 5 U.S. 
C. 605(b), the FAA certifies that this proposed AD would not have a 
significant economic impact on a substantial number of small entities.
    Title II of the Unfunded Mandates Reform Act of 1995 (the Act), 
enacted as Pub. L. 104-4 on March 22, 1995, requires each Federal 
agency, to the extent permitted by law, to prepare a written assessment 
of the effects of any Federal mandate in a proposed or final agency 
rule that may result in the expenditure by State, local, and tribal 
governments, in the aggregate, or by the private sector, of $100 
million or more (adjusted annually for inflation) in any one year. 
Section 204(a) of the Act, 2 U.S.C. 1534(a), requires the Federal 
agency to develop an effective process to permit timely input by 
elected officers (or their designees) of State, local, and tribal 
governments on a proposed ``significant intergovernmental mandate.'' A 
``significant intergovernmental mandate'' under the Act is any 
provision in a Federal agency regulation that would impose an 
enforceable duty upon State, local, and tribal governments, in the 
aggregate, of $100 million (adjusted annually for inflation) in any one 
year. Section 203 of the Act, 2 U.S.C. 1533, which supplements section 
204(a), provides that before establishing any regulatory requirements 
that might significantly or uniquely affect small governments, the 
agency shall have developed a plan that, among other things, provides 
for notice to potentially affected small governments, if any, and for a 
meaningful and timely opportunity to provide input in the development 
of regulatory proposals.
    This proposed AD does not contain any Federal intergovernmental or 
private sector mandate. Therefore, the requirements of Title II of the 
Unfunded

[[Page 61560]]

Mandates Reform Act of 1995 do not apply.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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

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


Sec. 39.13  [Amended]

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

Boeing: Docket 97-NM-232-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) 
SA1767SO or SA1768SO; 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, rapid 
decompression, and structural damage to the airplane; and to prevent 
failure of the main deck cargo barrier during an emergency landing, 
which could injure occupants; accomplish the following:

Actions Addressing the Main Deck Cargo Door Hinge

    (a) Within 250 flight cycles after the effective date of this 
AD, perform a detailed visual 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 visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

    (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 visual 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 visual inspection shall be accomplished in 
accordance with a method approved by the Manager, Atlanta Aircraft 
Certification Office (ACO), FAA, Small Airplane Directorate. 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, Atlanta ACO.
    (c) If any crack or discrepancy is detected during the detailed 
visual 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, Atlanta ACO.

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 the procedures specified in 
paragraphs (d)(1) and (d)(2) of this AD, 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, Atlanta ACO.
    (1) Procedures to ensure that all power is removed from the main 
deck cargo door prior to dispatch of the airplane. And
    (2) Procedures to ensure that the main deck cargo door is 
closed, latched, and locked prior to dispatch of the airplane.
    (e) Within 36 months after the effective date of this AD, 
incorporate redesigned main deck cargo door systems (e.g., warning/
monitoring, 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, Atlanta ACO.

    Note 3: The design data submitted for approval should include a 
Systems Safety Analysis and Instructions for Continued Airworthiness 
that are acceptable to the Manager, Atlanta 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 
4.b, in accordance with a method approved by the Manager, Atlanta 
ACO.

    Note 4: 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).

Alternative Methods of Compliance

    (g) An alternative method of compliance or adjustment of the 
compliance time contained in this proposal that provides an 
acceptable level of safety may be used if approved by the Manager, 
Atlanta ACO. Operators shall submit their requests through an 
appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Atlanta ACO.

    Note 5: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Atlanta ACO.

Special Flight Permit

    (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 the 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

[[Page 61561]]

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 November 4, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-29473 Filed 11-10-99; 8:45 am]
BILLING CODE 4910-13-U