Airworthiness Directives; Boeing Model 727 Series Airplanes Modified in Accordance With Supplemental Type Certificate SA1444SO, SA1509SO, SA1543SO, or SA1896SO

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-235-AD]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 727 Series Airplanes

Modified in Accordance With Supplemental Type Certificate SA1444SO,

SA1509SO, SA1543SO, or SA1896SO

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-235-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-235-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-235-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

Supplemental Type Certificate (STC) SA1509SO specifies a design for

a cargo door, associated cargo door cutout, and door systems. STC

SA1543SO specifies a design for a Class ``E'' cargo interior with a

cargo restraint barrier net. STC's SA1444SO and SA1896SO specify a

design for both of these subject areas. (All of these STC's are held by

Pemco.) As discussed in notice of proposed rulemaking (NPRM), Rules

Docket No. 97-NM-81-AD [the final rule, AD 98-26-21, amendment 39-

10964, was published in the Federal Register on January 12, 1999 (64 FR

2061)], 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

SA1590SO and SA1543SO and has identified several potential unsafe

conditions. [Results of this design review are contained in ``FAA

Freighter Conversion STC Review, Report Number 1, dated September 23-

26, 1996,'' (hereinafter referred to as ``the Design Review Report''),

which is included in the Rules Docket for this NPRM.] This NPRM

proposes corrective action for three of those potential unsafe

conditions that relate to the following three areas: main deck cargo

door hinge, main deck cargo door systems, and main deck cargo barrier.

Main Deck Cargo Door Hinge

In order to avoid catastrophic structural failure, it has been a

typical industry approach to design outward opening cargo doors and

their attaching structure to be fail-safe (i.e., designed so that if a

single structural element fails, other structural elements are able to

carry resulting loads). Another potential design approach is safe-life,

where the critical structure is shown by analyses and/or tests to be

capable of withstanding the repeated loads of variable magnitude

expected in service for a specific service life. Safe-life is usually

not used on critical structure because it is difficult to account for

manufacturing or in-service accidental damage. For this reason, plus

the fact

[[Page 61534]]

that none of the STC holders have provided data in support of this

approach, the safe-life approach will not be discussed further

regarding the design and construction of the main deck cargo door

hinge.

Structural elements such as the main deck cargo door hinge are

subject to severe in-service operating conditions that could result in

corrosion, binding, or seizure of the hinge. These conditions, in

addition to the normal operational loads, can lead to early and

unpredictable fatigue cracking. If a main deck cargo door hinge is not

a fail-safe design, a fatigue crack could initiate and propagate

longitudinally undetected, which could lead to a complete hinge

failure. A possible consequence of this undetected failure is the

opening of the main deck cargo door while the airplane is in flight.

Service experience indicates that the opening of a cargo door while the

airplane is in flight can be extremely hazardous in a variety of ways

including possible loss of flight control, severe structural damage, or

rapid decompression, any of which, could lead to loss of the airplane.

The design of the main deck cargo door hinge must be in compliance

with Civil Air Regulations (CAR) part 4b, including CAR part 4b.270,

which requires, in part, that catastrophic failure or excessive

structural deformation, which could adversely affect the flight

characteristics of the airplane, is not probable after fatigue failure

or obvious partial failure of a single principal structural element.

One common feature of a fail-safe hinge design is a division of the

hinge into multiple segments such that, following failure of any one

segment, the remaining segments would support the redistributed load.

The main deck cargo door installed in accordance with STC SA1509SO,

SA1444SO, or SA1896SO is supported by latches along the bottom of the

door and one continuous hinge along the top. This single-piece hinge is

considered a critical structural element for this STC. A crack that

initiates and propagates longitudinally along the hinge line of the

continuous hinge will eventually result in failure of the entire hinge,

because there is no segmenting of the hinge to interrupt the crack

propagation and support the redistributed loads. Failure of the entire

hinge can result in the opening of the main deck cargo door while the

airplane is in flight.

As discussed in the Design Review Report, an inspection of one

Boeing Model 727 series airplane modified in accordance with STC's

SA1509SO and SA1543SO 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

[[Page 61535]]

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

condition and issued, among others, the following AD's:

For certain McDonnell Douglas Model DC-9 series airplanes:

AD 89-11-02, amendment 39-6216 (54 FR 21416, May 18, 1989);

For all Boeing Model 747 series airplanes: AD 90-09-06,

amendment 39-6581 (55 FR 15217, April 23, 1990);

For certain McDonnell Douglas Model DC-8 series airplanes:

AD 93-20-02, amendment 39-8709 (58 FR 471545, October 18, 1993);

For certain Boeing Model 747-100 and -200 series

airplanes: AD 96-01-51, amendment 39-9492 (61 FR 1703, January 23,

1996); and

For certain Boeing Model 727-100 and -200 series

airplanes: AD 96-16-08, amendment 39-9708 (61 FR 41733, August 12,

1996).

Using the criteria specified in the ATA Final Report and the FAA

Memorandum as evaluation guides, the FAA conducted an engineering

design review and inspection of an airplane modified in accordance with

STC's SA1509SO and SA1543SO (held by Pemco). 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 design data did not include a safety analysis of the

main deck cargo door systems.

As specified in the criteria contained in Appendix 1 of this AD,

for powered lock systems on the main deck cargo door, it must be shown

by safety analysis that inadvertent opening of the door after it is

fully closed, latched, and locked is extremely improbable.

However, the FAA is aware of two events in which the main deck

cargo door open during flight. These events occurred on FedEx

passenger/freighter conversion STC's in October 1996, and March 1995.

These events are referenced in the Design Review Report.

The FAA has reviewed the design drawings of the main deck cargo

door systems installed on Boeing Model 727 series airplanes modified in

accordance with STC's SA1444SO, SA1509SO, and SA1896SO, and has

determined that the design of the door systems is nearly identical to

that installed on the subject FedEx passenger/freighter conversion

STC's. Therefore, the door opening events disclosed by FedEx are likely

to occur on airplanes modified in accordance with STC SA1444SO,

SA1509SO, or SA1896SO.

For airplanes modified in accordance with STC SA1444SO, SA1509SO,

SA1543SO, or SA1896SO, 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 the STC's SA1509SO,

SA1444SO, and SA1896SO uses a warning light at the door operator's

control panel and a light at the flight engineer's panel. Both of these

lights indicate the status of the cargo door latch and lock positions,

but do not indicate either the door open or closed status. All three

conditions (i.e., door closed, latched, and locked) must be monitored

directly so that the door indication system cannot display either

``latched'' before the door is closed or ``locked'' before the door is

latched. If a sequencing error caused the door to latch and lock

without being fully closed, the subject indication system, as designed,

would not alert the door operator or the flight engineer of this

condition. As a result, the airplane could be dispatched with the main

deck cargo door unsecured, which could lead to the cargo door opening

while the airplane is in flight and possible loss of the airplane.

The light on the flight engineer's panel is labeled ``MAIN CARGO''

and is displayed in red since it indicates an event that requires

immediate pilot action. However, if the flight engineer is temporarily

away from his station, a door unsafe warning indication could be missed

by the pilots. In addition, the flight engineer could miss such an

indication by not scanning the panel. As a result, the pilots and

flight engineer could be unaware of, or misinterpret, an unsafe

condition and could fail to respond in the correct manner. Therefore,

an indicator light must be located in front of and in plain view of

both pilots since one of the pilot's stations is always occupied during

flight operations.

The main deck cargo door indication system of STC's SA1509SO,

SA1444SO, and SA1896SO does not have a level of reliability that is

considered adequate for safe operation. Many components are exposed to

the environment during cargo loading operations and may be contaminated

by precipitation, dirt, and grease, or damaged by foreign objects or

cargo loading equipment. As a result, wires, switches, and relays can

fail, jam, or short circuit and cause a loss of indication or a false

indication to the door operator and flight crew. The design logic of

the indication system (i.e., lights which extinguish when the door is

locked) will, in the event of a single point failure that would

extinguish the light, result in an erroneous ``safe'' indication

regardless of actual door status.

The design of STC's SA1509SO, SA1444S0, and SA1896S0 has a ``Press-

to-Test'' red warning light on the main deck cargo door control panel

located near the L-1 door. The design of the monitoring system of the

main deck cargo door does not include separate lights to provide the

door operator with door close, latch, and lock status. The electrical

wiring design of the close, latch, and lock sensors of the door

monitoring system are wired in parallel instead of in series. In

parallel, two sensors could be sensing ``unsafe'' and the third sensor

could be sensing ``safe.'' If this situation were to occur, the sensors

would not illuminate the red warning light on the door control panel or

at the flight engineer's panel. Therefore, the ``Press-to-Test''

feature is adequate to check the light bulb functionality, but is not

adequate to check the cargo door close, latch, and lock functions and

status without annunciator lights for those three functions.

2. Means to Visually Inspect the Locking Mechanism

The single view port of the main deck cargo door installed in

accordance with STC's SA1444SO, SA1509SO, and SA1896SO is included to

allow the flight crew to conduct a visual inspection of the door

locking mechanism. This view port is used in conjunction with the door

warning system and should provide a suitable ``back-up'' in the event

that the main deck cargo door warning system malfunctions.

The door locking mechanism is an assembly comprised of multiple

lock pins (one for each of the door latches) connected by linkages to a

common lock shaft. Although an indicator flag attached to the lock

shaft can be seen through the view port when the shaft is in the

``locked'' position, a failure between the shaft and the pins could go

undetected, because this flag is attached to the lock shaft and not the

actual lock pins. If such a failure goes undetected, the airplane may

be dispatched with the main deck cargo door warning system inoperative

and the door not fully closed, latched, and locked, which could lead to

a main deck cargo door opening while the airplane is in flight and

possible loss of the airplane. Therefore, the FAA finds that the

[[Page 61536]]

subject view port is not a suitable back-up when the cargo door warning

system malfunctions.

As discussed in the ATA Final Report and the FAA Memorandum, there

must be a means of directly inspecting each lock or, at a minimum, the

locks at each end of the lock shaft of certain designs, such that a

failure condition in the lock shaft would be detectable.

3. Means to Prevent Pressurization to an Unsafe Level

Boeing 727-100 and -200 airplanes modified in accordance with STC

SA1444SO, SA1509SO, or SA1896SO are configured to utilize the existing

pressurization outflow valve for the purpose of preventing fuselage

pressurization of the airplane to an unsafe level in the event that the

main deck cargo door is not closed, latched, and locked. The FAA design

review of these modified Boeing 727-200 airplanes (documented in the

Design Review Report) identified single point failures in the door

control/outflow valve interface that could result in the valve not

sensing and responding to an unsafe door condition. In addition, the

FAA found no data to substantiate that the outflow valve location and

size could prevent pressurization to an unsafe level. With the current

design, it is possible that the outflow valve may not perform its

intended function when utilized for the purpose of preventing

pressurization of the airplane in the event of an unsecured door. This

condition could result in cabin pressurization forcing an unsecured

door open while the airplane is in flight and possible loss of the

airplane.

In some cases, neither Boeing 727-100 airplanes nor Boeing 727-200

airplanes modified in accordance with the STC SA1444SO or SA1509SO have

any means of preventing pressurization in the event that the main deck

cargo door is not closed, latched, and locked, and therefore, have a

higher risk of a cargo door opening while the airplane is in flight and

possible loss of the airplane.

4. Powered Lock Systems

The main deck cargo door control system for STC's SA1444SO,

SA1509SO, and SA1896SO that utilizes electrical interlock switches is

designed to remove door control power (electrical and hydraulic) prior

to flight and to prevent inadvertent door openings. As discussed

previously, the door system design of the subject STC's is nearly

identical to the FedEx design. The FedEx door opening events, discussed

previously, indicate the likelihood that there may be latent and/or

single point failures that can restore or continue to allow power to

the door controls and cause inadvertent door openings. The failure

modes may be found in the electrical portion of the door control panel,

which, in turn, activates the door control hydraulics. The potential

for the occurrence of these failure conditions is increased by the

harsh operating environment of freighter airplanes. Door system

components are routinely exposed to precipitation, dirt, grease, and

foreign object intrusion, all of which increase the likelihood of

damage. As a result, wires, switches, and relays have a greater

potential to fail or short circuit in such a way as to allow the cargo

door to be powered open without an operator's command and regardless of

electrical interlock positions.

A systems safety analysis would normally evaluate and resolve the

potential for these types of unsafe conditions. However, the design

data for STC's SA1444SO, SA1509SO, and SA1896SO do not include a

systems safety analysis to specifically identify these failure modes

and do not show that an inadvertent opening is extremely improbable.

The need for a system safety analysis is identified in the ATA Final

Report and the FAA Memorandum.

Since unsafe conditions have been identified that are likely to

exist or develop on other products of this same type design, this

proposed AD would require, within 60 days after the effective date,

revising the Limitations Section of the FAA-approved Airplane Flight

Manual (AFM) Supplement to provide the flight crew with procedures for

ensuring that all power is removed from the main deck cargo door prior

to dispatch of the airplane, and that the main deck cargo door is

closed, latched, and locked prior to dispatch of the airplane; and

installing any associated placards.

In addition, the proposed AD would require, within 36 months after

the effective date of the AD, incorporation of redesigned main deck

cargo door systems (e.g., warning/monitoring, power control, view

ports, and means to prevent pressurization to an unsafe level if the

main deck cargo door is not closed, latched, and locked), including any

associated procedures and placards that comply with the applicable

requirements of CAR part 4b and design criteria of the ATA Final Report

and the FAA Memorandum. Design data provided in support of the door

systems 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 Restraint Barrier

In order to ensure the safety of occupants during emergency landing

conditions, the FAA first established in 1934, a set of inertia load

factors used to design the structure for restraining items of mass in

the fuselage. Because the airplane landing speeds have increased over

the years as the fleet has transitioned from propeller to jet design,

inertia load factors were changed as specified in CAR part 4b.260.

Experience has shown that an airplane designed to this regulation has a

reasonable probability of protecting its occupants from serious injury

in an emergency landing. The 727 passenger airplane was designed to

these criteria which specified an ultimate inertia load requirement of

9g in the forward direction. These criteria were applied to the seats

and structure restraining the occupants, including the flight crew, as

well as other items of mass in the fuselage.

When the 727 passenger airplane is converted to carry cargo on the

main 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 1996 of a Boeing 727 modified in

accordance with STC SA1543SO. The observations revealed that the design

of the net restraint barrier floor attachment and circumferential

supporting structure

[[Page 61537]]

does not provide adequate strength to withstand the 9g forward inertia

load generated by the main deck cargo mass, nor does it provide a load

path to effectively transfer the loads from the restraint barrier to

the fuselage structure of the airplane. These observations are

supported by data contained in ``ER 2785, Structural Substantiation of

the 50k 9g Bulkhead Restraint System in Support of STC SA1543SO PN 53-

1292-401 for the 9g Bulkhead 53-1980-300 Assembly with Upper Attachment

Structure, Lower Attachment Structure, Floor Shear Web Structure, Seat

Track Splice Fittings, Seat Tracks, and Seat Track Splices,'' dated

September 29, 1996, by M. F. Daniel. Although this report was specific

to STC SA1543SO, the FAA has determined that the data are applicable to

airplane modified in accordance with STC ST00015AT because the design

principles for attachment of the barriers in both STC's are the same.

The report reveals that the structural deficiencies were found in the

net attach plates and floor attachment structure of the cargo barrier.

The data show large negative margins of safety, which indicate that the

inertia load capability of the cargo barrier is closer to 2g than the

required 9g in the forward direction. From these analyses, it is

evident that the cargo restraint barrier would not be capable of

preventing serious injury to the occupants during an emergency landing

event with the full allowable cargo load.

Since unsafe conditions have been identified that are likely to

exist or develop on other products of this same type design, this

proposed AD would require installation of a main deck cargo barrier

that complies with the applicable requirements of CAR part 4b.

Accomplishment of the installation will prevent serious injury to the

occupants in the event of an emergency landing. The proposed compliance

time for the installation is within 36 months or 4,000 flight cycles

after the effective date of the AD, whichever occurs first. This

compliance time is based on the FAA's assessment of the reasonable

amount of time to redesign, manufacture, and install the cargo barrier.

This time is 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 power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

This analysis examines the cost of a proposed AD that would require

the installation of a fail-safe hinge, redesigned main deck cargo door

warning and power control systems, and a 9g cargo barrier on Boeing

Model 727 series airplanes that have been modified in accordance with

STC's held by Pemco. 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 62 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 AD and the

estimated cost associated with each of these actions. An analysis of

the costs is also available in Rules Docket No. 97-NM-235-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. Pemco estimates that this inspection would take 1.5

work hours. At a mechanic's burdened labor rate of $60 per work hour,

the cost per airplane would be $90, or $5,580 for the fleet of 62

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 a cost of

$12,000 per airplane, or $744,000 for the affected fleet.

Paragraph (b)(2) of the proposed AD would require installation of a

fail-safe door hinge. The compliance time for this installation also

would be 36 months or 4,000 cycles after the effective date of this AD.

Pemco estimates the cost to design and certificate such a hinge is

$20,000, that the parts for a fail-safe door hinge would cost $8,000,

and installation would take 300 hours. Total compliance costs for this

proposed provision for the affected fleet of 62 airplanes would be $1.6

million.

Paragraph (c) of the proposed AD would require that, if any crack

or discrepancy is 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 $2.4 million, or $2.0

million 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 operators of airplanes modified under Pemco AD's would perform

these two activities uniformly throughout the 36-month period. Finally,

the certification cost for the main deck cargo door hinge would be

incurred within the first 6 months after the effective date of this AD.

2. Main Deck Cargo Door Systems

Paragraph (d) of the proposed AD would require, within 60 days

after the effective date, revising the Limitations Section of the FAA-

approved Airplane Flight Manual (AFM) Supplement to provide the flight

crew with procedures for ensuring that all power is removed from the

main deck cargo door prior to dispatch of the airplane, and that the

main deck cargo door is closed, latched, and locked prior to dispatch

of the airplane. In addition, paragraph (d) of the proposed AD would

require the installation of any associated placards.

The Pemco door system design as provided by STC's SA1444SO,

SA1896SO, and SA1509SO is nearly identical to that of FedEx. Therefore

it is likely that the cost associated with the inspection of the door

are the same based on FedEx's assumptions. FedEx assumes that an

external inspection of the flushness of the cargo door, combined with

an ``enhanced B-check'' would be an acceptable means to the FAA to

ensure that the cargo door is secured prior to dispatch. Based on this

assumption, FedEx estimates, before a redesigned door system is

installed [see proposed paragraph (f) below], that it would take a

mechanic 30 minutes to inspect for flushness of the main deck cargo

door prior to dispatch. Using these

[[Page 61538]]

estimates for compliance for airplanes with Pemco STC's, and, assuming

each affected airplane flies 1 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 $865,800 over 36

months.

B-checks on these Boeing Model 727 series airplanes occur

approximately twice a year. FedEx estimates the incremental cost for

maintenance during this ``enhanced B-check'' is $11,700 per year until

the door system is changed. Assuming incorporation of the redesigned

door system occurs uniformly over the 36-month period, the total cost

to operators of Pemco-modified Boeing Model 727 series airplanes would

be $1.3 million. In addition, Pemco estimates the setup costs for the

daily inspection (i.e., procedure materials for the mechanics to

perform the inspection and training requirements) would be $50,000.

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. Pemco estimates that the development and

certification of the system would cost $138,800. Modification parts

would cost $10,000 per airplane and labor costs would be $18,000 per

airplane. The FAA assumes that operators would incorporate the

redesigned main deck cargo door system during regularly scheduled

maintenance but that, on average, each airplane in the affected fleet

would be out of service for 3 additional days at a cost of $18,300. The

total costs of installing a redesigned main deck cargo door system,

including certification, parts, labor, and down time would be $3.0

million over the 36-month period.

The total estimated cost to comply with proposed requirements for

the main deck cargo door system is $5.2 million or $4.6 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. Pemco estimates that development and

certification of a 9g barrier would cost $126,500, while parts would

cost $25,000 and labor would cost $18,000 per airplane for 300 hours of

labor at $60 per hour burdened rate.

The FAA assumes that operators would install 9g barriers in their

affected fleets uniformly over the 36-month compliance period. The

total non-discounted cost would be $2.8 million, or $2.4 million

discounted to present value.

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

Paragraph (g) of the proposed AD would allow an AMOC or adjustment

of compliance time that provides an acceptable level of safety if

approved by the Manager of the Atlanta ACO. The FAA is unable to

determine the cost of an AMOC, but assumes it would be less than the

cost of complying with the proposed provisions in paragraphs (a)

through (f) of the proposed AD.

Paragraph (h) of the proposed AD would allow special flight permits

in accordance with the regulations to operate an affected airplane to a

location where the requirements of the proposed AD could be

accomplished.

5. Total Cost of the Proposed AD

The FAA estimates that the total compliance cost of the proposed AD

would be $10.4 million, or $9.0 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.

Six of the 11 operators that would be affected by this proposed AD

are small, that is, they employ fewer than 1,500 persons. The estimated

total cost of the proposed AD is $10.4 million, or approximately

$167,700 for each of the 62 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 conditions.

[[Page 61539]]

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 6 of the 11 entities are small, i.e., employ fewer than

1,500 persons. Two small entities operate 1 affected airplane each, 1

small entity operates 2 affected airplanes, 1 small entity operates 7

affected airplanes, and 2 small entities operate 9 affected airplanes

each. 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 $167,700. 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 Boeing 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 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-235-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)

SA1444SO, SA1509SO, SA1543SO, or SA1896SO; 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,

[[Page 61540]]

magnifying lenses, etc., may be used. Surface cleaning and elaborate

access procedures may be required.''

(b) Within 36 months or 4,000 flight cycles after the effective

date of this AD, whichever occurs first, accomplish paragraphs

(b)(1) and (b)(2) of this AD.

(1) Perform a detailed visual inspection of the mating surfaces

of both the hinge and the door skin and external fuselage doubler

underlying the hinge to detect cracks or other discrepancies (e.g.,

double or closely drilled holes, corrosion, chips, scratches, or

gouges). The detailed visual inspection shall be accomplished in

accordance with a method approved by the Manager, Atlanta Aircraft

Certification Office (ACO), FAA, Small Airplane Directorate. The

requirements of this paragraph may be accomplished prior to or

concurrently with the requirements of paragraph (b)(2) of this AD.

(2) Install a main deck cargo door hinge that complies with the

applicable requirements of Civil Air Regulations (CAR) part 4b,

including fail-safe requirements, in accordance with a method

approved by the Manager, Atlanta ACO.

(c) If any crack or discrepancy is detected during the detailed

visual inspection required by either paragraph (a) or (b)(1) of this

AD, prior to further flight, repair in accordance with a method

approved by the Manager, Atlanta ACO.

Actions Addressing the Main Deck Cargo Door Systems

(d) Within 60 days after the effective date of this AD, revise

the Limitations Section of the FAA-approved Airplane Flight Manual

(AFM) Supplement by inserting therein the procedures specified in

paragraphs (d)(1) and (d)(2) of this AD, and install any associated

placards. The AFM revision procedures and installation of any

associated placards shall be accomplished in accordance with a

method approved by the Manager, Atlanta ACO.

(1) Procedures to ensure that all power is removed from the main

deck cargo door prior to dispatch of the airplane. And

(2) Procedures to ensure that the main deck cargo door is

closed, latched, and locked prior to dispatch of the airplane.

(e) Within 36 months after the effective date of this AD,

incorporate redesigned main deck cargo door systems (e.g., warning/

monitoring, power control, view ports, and means to prevent

pressurization to an unsafe level if the main deck cargo door is not

closed, latched, and locked), including any associated procedures

and placards, that comply with the applicable requirements of CAR

part 4b and criteria specified in Appendix 1 of this AD; in

accordance with a method approved by the Manager, Atlanta ACO.

Note 3: The design data submitted for approval should include a

Systems Safety Analysis and Instructions for Continued Airworthiness

that are acceptable to the Manager, Atlanta ACO.

Actions Addressing the Main Deck Cargo Barrier

(f) Within 36 months or 4,000 flight cycles after the effective

date of this AD, whichever occurs first, install a main deck cargo

barrier that complies with the applicable requirements of CAR part

4.b, in accordance with a method approved by the Manager, Atlanta

ACO.

Note 4: The maximum main deck total payload that can be carried

is limited to the lesser of the approved cargo barrier weight limit,

weight permitted by the approved maximum zero fuel weight, weight

permitted by the approved main deck position weights, weight

permitted by the approved main deck running load or distributed load

limitations, or approved cumulative zone or fuselage monocoque

structural loading limitations (including lower hold cargo).

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 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. 99-29476 Filed 11-10-99; 8:45 am]

BILLING CODE 4910-13-U