[Federal Register Volume 64, Number 218 (Friday, November 12, 1999)]
[Proposed Rules]
[Pages 61547-61554]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-29474]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-233-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 727 Series Airplanes 
Modified in Accordance With Supplemental Type Certificate SA1368SO, 
SA1797SO, or SA1798SO

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-233-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-233-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-233-AD, 1601 Lind Avenue, SW, Renton, Washington 
98055-4056.

Discussion

    Supplemental Type Certificates (STC) SA1797SO and SA1368SO (held by 
Aeronautical Engineers, Inc.) specify a design for a main deck cargo 
door, associated cargo door cutout, and door systems. STC SA1798SO 
(held by Aeronautical Engineers, Inc.) specifies a design for a Class 
``E'' cargo interior with a cargo barrier. As discussed in notice of 
proposed rulemaking (NPRM), Rules Docket No. 97-NM-79-AD [the final 
rule, AD 98-26-19, amendment 39-10962, was published in the Federal 
Register on January 12, 1999 (64 FR 2016)], 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 SA1797SO and SA1798SO and has 
identified several potential unsafe conditions. [Results of this design 
review are contained in ``FAA Freighter Conversion STC Review, Report 
Number 3, dated January 27, 1997,'' 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

[[Page 61548]]

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's 
SA1797SO and SA1368SO 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 these STC's. 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.
    As discussed in the Design Review Report, an inspection of one 
Boeing Model 727 series airplane modified in accordance with STC's 
SA1797SO and SA1798SO 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, 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:

[[Page 61549]]

     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 SA1797SO and SA1798SO (held by Aeronautical Engineers, Inc.). 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.
    For airplanes modified in accordance with STC SA1797SO, SA1798SO, 
or SA1368SO, 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 SA1368SO and 
SA1797SO uses warning lights at the door operator's control panel and a 
light at the flight engineer's panel. These lights indicate the status 
of the cargo door closed, latched and locked configurations. All three 
conditions (i.e., door closed, latched, and locked) should 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. The latch and lock sensors are wired in parallel and are tied 
to a single indicator light. This design can illuminate the ``locked 
light'' on the control panel of the main deck cargo door even if the 
latches are latched but not locked. If a sequencing error causes the 
door to latch and lock without being fully closed, the subject 
indication system, as designed, may 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 ``DOOR 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 should 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.
    Based on the review of the electrical drawings of the door control 
and door monitoring/annunication systems and observations from an 
inspection of an airplane modified in accordance with the subject 
STC's, the FAA concludes that latent failures (i.e., failures of system 
components that are not monitored and would go undetected) in the 
closed, latched, and locked functions may occur and lead to the main 
deck cargo door opening during flight of the airplane.
    The FAA has determined that the main deck cargo door indication 
system of STC's SA1368SO, and SA1797SO also does not meet the 
improbable level of reliability regarding false indication 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) could, in the event of latent failures that would extinguish 
the light, result in an erroneous ``safe'' indication regardless of 
actual door status.
    STC's SA1368SO and SA1797SO lack a safety analysis of the main deck 
cargo door systems. As a result, even though the light at the door 
operator's control panel and the light at the flight engineer's panel 
annunciate the status of closed, latched, and locked, a safety analysis 
must be developed to show whether the design of the wiring of the main 
deck cargo door monitoring system meets all FAA requirements.

2. Means to Visually Inspect the Locking Mechanism

    The two view ports installed in accordance with STC's SA1797SO and 
SA1368SO are located externally on the door for the purpose of viewing 
locking pins at the No. 2 and No. 7 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 the cargo door is closed, latched, and locked. The 
view ports are used in conjunction with the door warning system and is 
intended to provide a suitable back-up in the event that the main deck 
cargo door warning system malfunctions.
    However, because of the location of these view ports on the main 
deck cargo door, a visual inspection may not result in the detection of 
certain failures (e.g., bending or shearing of locking pins), and 
consequently the airplane could be dispatched with the main deck cargo 
door unsecured. Therefore, the FAA finds that these view ports are 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 to install a cargo door in 
accordance with STC SA1797SO are configured to utilize a mechanical 
vent door 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. However, Boeing 727-100 airplanes that have been 
modified in accordance with STC SA1368SO do not have a vent door design 
to prevent pressurization as part of the STC.
    The results of an FAA inspection of the vent door linkage revealed 
that the linkage design could exhibit single failures that could cause 
the vent door to malfunction. A complete safety analysis of the vent 
door mechanical design is necessary to identify and correct all such 
malfunctions. No single failure of the mechanisms can defeat the 
intended function of the vent door system.

4. Powered Lock Systems

    The main deck cargo door control system for STC's SA1368SO and

[[Page 61550]]

SA1797SO that utilizes electrical interlock switches is designed to 
remove door control power (electrical and hydraulic) prior to flight 
and to prevent inadvertent door openings. Failure modes have been 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 FAA has 
reviewed the design data for STC's SA1368SO and SA1797SO. The FAA finds 
that the powered lock systems of the main deck cargo door do not comply 
with criteria specified in Appendix 1 of this AD and considers the 
design of these systems to be unsafe. 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 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 re-design 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 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 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 SA1798SO.
    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 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 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 consistent with estimates by affected STC 
holders and operators that necessary redesigns can by developed and 
approved by the FAA within 12 to 18 months from August 1998.

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

[[Page 61551]]

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 this 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 Aeronautical Engineers, Inc. (AEI). 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 72 U.S.-registered Boeing Model 727 series airplanes 
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-233-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. AEI estimates that this inspection would take 2 work 
hours. At a mechanic's burdened labor rate of $60 per work hour, the 
cost per airplane would be $120, or $8,640 for the 72 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 $224,400 for the entire 
affected fleet of 72 airplanes.
    Paragraph (b)(2) of the proposed AD would require installation of a 
fail-safe door hinge. The compliance time for this installation also 
would be 36 months, or 4,000 cycles after the effective date of this 
AD. AEI estimates the cost to design and certificate such a hinge is 
$25,000, that no parts for a fail-safe door hinge would be required, 
and that the modification would take 50 hours. Total compliance costs 
for this proposed provision for the affected fleet of 72 airplanes 
would be $241,000.
    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 $474,000 or $419,800 
discounted to present value at 7 percent. 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 the 
affected carriers 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 the AD.

2. Main Deck Cargo Door Systems

    Paragraph (d) of the proposed AD would require, within 60 days 
after the effective date of this AD, a revision to the Limitations 
Section of the FAA-approved AFM Supplement by inserting procedures to 
ensure that the main deck cargo door is closed, latched, and locked 
prior to dispatch of the airplane. In addition, paragraph (d) of the 
proposed AD would require the installation of any associated placards.
    The FAA assumes that Boeing Model 727 series airplanes converted 
under a AEI STC will have an acceptable pressurization vent door 
installed, which operators could use 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 would take no more than 30 minutes. Assuming each affected 
airplane flies one flight per day, 260 days per year, the estimated 
cost per inspection would be $30, or $7,800 per airplane per year until 
the door system is changed, a total of $982,800 over 36 months.
    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. The FAA estimates that the development and 
certification of the system would cost $25,000. Modification parts 
would cost $5,000 per airplane and labor costs would be $6,000 per 
airplane for 100 hours. The FAA assumes that operators would 
incorporate the redesigned main deck cargo door system during regularly 
scheduled maintenance. The total costs of installing a redesigned main 
deck cargo door system, including certification, parts, and labor would 
be $817,000 over the 36-month period.
    The total estimated cost to comply with proposed requirements for 
the main deck cargo door system is $1.8 million, or $1.7 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. Ventura Aerospace holds an STC for an 
approved 9g barrier, and the FAA estimates that operators whose 
airplanes have been modified in accordance with AEI STC's would 
purchase 9g barrier kits from Ventura Aerospace. The cost of a barrier 
kit is $67,500. The FAA estimates that labor would cost $13,500 per 
airplane and that an affected airplane would be out-of-service 3 
additional days, at a cost of $15,000 per day, while this barrier is 
installed.
    The FAA assumes that operators would install 9g barriers uniformly 
over the 36-month compliance period. The total non-discounted cost to 
comply with paragraph (g) of the proposed AD would be $9.1 million, or 
$7.8 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

[[Page 61552]]

would be $11.3 million, or $10.0 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 an RFA is not required. The 
certification must include a statement providing the factual basis for 
this determination, and the reasoning should be clear.
    The FAA estimates that 16 carriers operate airplanes that would be 
affected by this proposed AD. Four of these operators are foreign 
entities, 5 operators are large, and 7 operators are small, that is, 
they employ fewer than 1,500 persons. The estimated total cost of the 
proposed AD is $11.3 million, or approximately $157,600 for each of the 
72 affected airplanes. Therefore, the FAA has determined that the 
proposed rule would have a significant impact on a substantial number 
of small entities and a regulatory flexibility analysis is required.
    Under Section 63(b) of the RFA, the analysis must address:
    1. Reasons why the agency is promulgating the rule;
    2. The objectives and legal basis for the rule;
    3. The kind and number of small entities to which the rule will 
apply;
    4. The projected reporting, recordkeeping, and other compliance 
requirements of the rule; and
    5. All federal rules that may duplicate, overlap, or conflict with 
the rule.

These elements of the RFA are addressed below.

A. Reasons Why Agency Action Is Being Considered

    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 the main deck cargo barrier is 
not structurally adequate during a minor crash landing. The actions 
specified in 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, and consequent rapid decompression and/or 
structural damage to the airplane; and to prevent failure of the main 
deck cargo barrier during an emergency landing, which could injure 
occupants.

B. Statement of Objective and Legal Basis

    Under the United States Code (U.S.C), the FAA Administrator is 
required to consider the following matter, among others, as being in 
the public interest: assigning, maintaining, and enhancing safety and 
security as the highest priorities in air commerce. [See 49 U.S.C. 
Sec. 44101(d).] 49 U.S.C. Sec. 44701(a) provides broad rulemaking 
authority to ``promote safe flight of civil aircraft in air commerce.'' 
Accordingly, this proposed AD will amend Title 14 of the Code of 
Federal Regulations to require operators of Boeing Model 727 series 
airplanes that have been converted from a passenger- to a cargo-
carrying configuration to correct the identified unsafe condition.

C. Kind and Number of Small Entities

    The RFA requires the FAA to determine whether or not a rule 
significantly affects a substantial number of small entities. This 
determination is typically based on small entity size and cost 
thresholds that vary depending on the affected industry. The entities 
affected by the rule are those operating U.S.-registered converted 
Boeing Model 727 series airplanes. The FAA has determined that 
approximately 7 of the 16 entities are small, i.e., employ fewer than 
1,500 persons. These small entities operate between 1 and 9 affected 
airplanes. Assuming the total costs of the proposed rule are divided 
equally among the affected fleet of 62 airplanes, the costs per 
airplane would be about $157,600. Therefore, the FAA has determined 
that this proposed AD would significantly affect a substantial number 
of small entities.

D. Projected Reporting, Recordkeeping, and Other Compliance 
Requirements

    With two minor exceptions, the rule will not mandate additional 
reporting or recordkeeping. The proposed AD would require operators to 
report results of the visual inspection of the main deck cargo door 
hinge and the visual inspection of the fastener holes common to the 
main deck cargo door hinge and underlying door and fuselage structure. 
The cost of these reports is negligible.

E. Overlapping, Duplicative, or Conflicting Federal Rules

    The rule will not overlap, duplicate, or conflict with existing 
Federal rules.

F. Analysis of Alternatives

    The FAA acknowledges that the rule will impose a financial 
requirement on small entities. Therefore, the agency considered 
alternatives to the proposed rule. These alternatives are:
     Exclude small entities; and
     Extend the compliance date for small entities.
    The FAA has determined that the option to exclude small entities 
from the requirements of the rule is not justified. The unsafe 
condition that exists on an affected Boeing Model 727 series airplane 
operated by a small entity is as potentially catastrophic as that on an 
affected Model 727 series airplane operated by a large entity.
    The FAA also considered options to extend the compliance period for 
small operators. The Boeing 727 Freighter Industry Working Group, which 
includes all affected U.S. operators (including small entities), 
provided input on the incorporation of corrective actions for the door 
hinge, door systems, and 9g barrier issues. The FAA initially proposed 
a compliance time of 28 months, consistent with a related AD dealing 
with the cargo floor structure on the same airplanes. The Industry 
Working Group requested an extension to 36 months. Following review of 
the Working Group's request, the FAA finds 36 months to be an 
acceptable compliance time. Therefore, the FAA has, in fact, considered 
and accepted this alternative and has accommodated small entity 
concerns about compliance time.
    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

[[Page 61553]]

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 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-233-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) 
SA1368SO, SA1797SO, or SA1798SO; 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 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, Atlanta ACO.
    (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).

    Note 5: 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.

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

    (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

[[Page 61554]]

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 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. 99-29474 Filed 11-10-99; 8:45 am]
BILLING CODE 4910-13-U