[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