Outward opening electrically powered plug-type cargo door

An outward opening plug-type cargo door for an aircraft is movable between a closed position in which the door blocks an entry opening into the aircraft and an open position in which the door is spaced from the entry opening. The door hinges are directly driven by irreversible rotary actuators. When the door is positioned adjacent the entry opening, a latch mechanism is operable to move the door between a latched and an unlatched position. In the latched position, the door is secured from outboard movement by a plurality of stop pins spaced about the periphery of the door that are located inboard of a series of stop pads mounted at spaced locations about the periphery of the door opening. When the latch mechanism is operated, the door is lifted to free the stop pins from their location behind the stop pads and permit outboard movement of the door. The movement of the door between the latched and lifted positions is programmed by a guide mechanism comprised of guide channels mounted on first and second edges of the door opening that are cooperably engaged by rollers rotatably mounted on first and second edges of the door. The guide channels have detents formed therein and the guide rollers engage the detents when the door is in the latched position and the pressure within the aircraft is greater than the pressure exterior to the aircraft. The detents resist upward vertical movement of the door to maintain the door securely in the latched position to prevent accidental blowout of the door caused by the pressure differential. A power unit is provided to operate the latch mechanism to move the door between the latched and lifted positions and a second power unit is provided to drive the door between the closed and open position. Sensor switches are positioned about the door and entry opening to sequence application of power to the two power units to open and close and latch and unlatch the door. A primary manual drive mechanism is provided coupled to the latch mechanism and the hinge mechanism to operate the latch mechanism and the hinge mechanism in the case of failure of the power unit. A secondary manual drive system is also provided coupled to the hinge mechanism to open and close the door upon failure of the power unit or the primary manual drive.

BACKGROUND OF THE INVENTION 
This invention relates generally to doors for entry to the cargo areas of 
transport vehicles, for example, aircraft, and more particularly relates 
to an electrically powered outwardly opening plug-type cargo door for an 
aircraft. 
Outward opening doors for use in cargo compartments of aircraft are 
advantageous compared to inward opening doors in that they do not occupy 
space in the cargo compartment that could otherwise be used for cargo. 
Plug-type doors for aircraft are advantageous over nonplug-type doors in 
that an adequate level of safety can be achieved with greater simplicity 
of mechanism by a plug-type door to prevent the blow-out or accidental 
opening of the door when the interior cargo compartment pressure is 
greater than the exterior ambient air pressure, for example, when the 
aircraft is in flight. 
Previous outwardly opening plug-type cargo doors have been 
spring-counterbalanced and manually operated from the ground. In many of 
these prior art doors, a strut is used to prop the door open while cargo 
is being loaded and unloaded. The strut propping the door open prevents 
the door from inadvertently closing due to wind gusts or other external 
factors that would overcome the counterbalancing of the door. 
SUMMARY OF THE INVENTION 
The present invention provides an outward opening plug-type door 
particularly for use in covering the opening into a cargo bay of an 
aircraft. In a first, closed position, the door blocks a door opening 
formed in the body of the aircraft leading into the cargo area. The door 
is movable to a second position in which the door is spaced from the door 
opening in a canopy orientation above and outboard of the cargo bay 
opening. The door is hingedly attached to the body structure by hinges 
that are directly driven by irreversible rotary actuators such that the 
weight of the door cannot backdrive the actuators. The door must, 
therefore, be powered to both the opened and closed positions, thereby 
eliminating the necessity for a strut to prop the door open when cargo is 
being loaded and unloaded. The door hinge mechanism is attached directly 
to the rotary actuators and is constructed and arranged to move the door 
linearly outboard as it swings into its open canopy orientation. 
Preferably, a primary manual backup is provided for the power-driven 
rotary actuators in case of power failure. Further, a secondary manual 
backup system is preferably provided to permit the opening of the door in 
the event of complete failure of the power unit. 
The door of the present invention is a plug-type door and is secured into 
the cutout opening so that it cannot be blown out of the opening by a 
pressure differential between the interior and exterior of the aircraft. 
Prior to being swung into its canopy orientation, the door must be 
unplugged by moving it upwardly a predetermined distance to free it from 
the plug stops and permit it to be swung into its open position. A 
mechanism for latching and unlatching the door is provided that lifts the 
door during the unlatching sequence to unplug the door and permit outboard 
swinging movement. The lifting and latching mechanism is powered and 
sensor switches are placed at spaced locations about the door and frame to 
sense the position of the door and to apply and remove power to the 
lift-latch mechanism and the hinge mechanism in the proper sequence to 
operate the door. Upon pressurization of the interior of the aircraft, the 
door is forced outboard against the door stops. Guide tracks are mounted 
on the door frame that guide the motion of the door between its latched 
and unlatched lifted position. The primary feature to latch and lock the 
door is provided by an over center latch crank system; however, the guide 
tracks of the present invention have detents formed therein that prevent 
vertical motion of the door when the door is latched and the interior of 
the aircraft is pressurized. Since the vertical motion of the door is 
restrained when the door is pressurized accidental vertical movement of 
the door that could free it from behind the doorstops is prevented. Thus, 
the plugged configuration of the door is maintained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
One embodiment of a door 10 adapted for use in connection with the entry 
opening to the cargo compartment of a commercial airliner, e.g., the 
Boeing 767, and made in accordance with the principles of the present 
invention is pictured in FIG. 1. The door 10 is shown in the open, 
position spaced from a cutout 12 in the aircraft body that serves as the 
entry to a cargo hold 14. The door 10 is held in a canopy orientation by 
hinge means 16 and 16a attached at a first end to the door and at a second 
end to the upper sill of the body cutout. 
A control panel 18 is positioned on the exterior of the plane below and 
forward of the cutout 12 and can be reached from the ground without a 
ladder. The control panel 18 contains the controls for operating the door 
mechanism to open and close the door 10 to facilitate the loading and 
unloading of cargo, such as container 20. 
In FIG. 2, the door 10 is shown in side elevational view in the closed and 
latched position within the body cutout 12. In its closed and latched 
condition, the outer skin 22 of the door 10 is flush with the exterior 
skin 24 of the aircraft surrounding the body cutout to provide smooth 
aerodynamic surfaces. In the latched condition, the door 10 is held from 
outboard movement by a plurality of stop pins 26 fixedly mounted at spaced 
locations along first and second edges 28 and 30 of the door. The stop 
pins are inboard of and coact with stop pads 32 mounted on the forward and 
aft edges of the body cutout 12. Three lower hook stops 34 are fixed to a 
bottom edge 36 of the door. The hook stops 34 are spaced along the bottom 
edge 36 and coact with lower clevises 38 affixed to the lower sill of the 
body cutout 12 in cooperative locations such that the lower hook stops 34 
engage the lower clevises 38 when the door 10 is in the latched condition 
in the body cutout. 
Three upper clevises 40 are mounted on the upper edge 42 of the door 10 at 
spaced locations. The upper clevises cooperate with three upper hook stops 
44 fixedly mounted to the upper sill of the body cutout 12 to assist in 
holding the door in the latched position. The lower hook stops 34 are 
C-shaped hooks with the open end of the C facing approximately downwardly, 
while the upper hook stops 44 are C-shaped hooks but have their openings 
directed upwardly. In order for the door to move to its open position 
spaced from the body cutout to permit entry to the cargo area, it is 
necessary to first lift the door 10 upwardly and slightly inboard to move 
the stop pins 26 from their positions behind the stop pads 32 and to 
release the upper hook stops 44 and lower hook stops 34 from engagement 
with the upper clevises 40 and lower clevises 38, thereby permitting 
swinging motion of the door outboard. The door just described is a 
plug-type door, meaning that because of the location of the stop pads and 
hooks, the door cannot be moved outboard when it is in the latched 
condition and is therefore resistant to being blown out of its closed 
position by a pressure differential between the interior of the cargo area 
14 and the exterior of the aircraft such as is encountered during flight. 
After the door is unlatched and lifted to unplug the door it is clear to 
swing to the open position. The hinge means 16 is illustrated in FIGS. 3 
and 4. The door 10 articulates about a first rotary actuator 46 that is 
mounted adjacent the upper sill of the door cutout. The door 10 is 
attached through a hinge linkage directly to the rotary actuator 46. In 
FIG. 3 the door is shown in its unlatched and lifted position and as can 
be seen, a lower lift link 48 is hingedly attached at a first end thereof 
to the door 10. A second end of the lower lift link 48 is hingedly 
attached to a first end of an inextensible hinge link 50. A second end of 
the hinge link 50 is pivotally attached to a second end of an upper lift 
link 52 and a first end of the upper lift link 52 is pivotally attached to 
the door 10 at a point spaced upwardly from the lower lift link 48. The 
upper and lower lift links 52 and 48 are maintained in substantially 
parallel relation to one another by the inextensible hinge link 50. A 
hinge arm 54 is rigidly mounted to the first rotary actuator 46 so that 
the hinge arm 54 moves in direct proportion to the rotation of the rotary 
actuator 46. The hinge arm 54 is connected to the lower lift link 48 by an 
adjustable rod 56 that is pivotally attached at a first end thereof to a 
second end of the hinge arm 54 in distal relation to the first rotary 
actuator 46. A second end of the adjustable rod 56 is attached to the 
common connection point between the lower lift link 48 and the hinge link 
50. A connection between the hinge arm 54 and the upper lift link 52 is 
made by means of a scissors arm 58 that is shown in plan view in FIG. 5. 
In FIG. 5 the door is in the open position corresponding to the door 
position shown in FIG. 4. The scissors arm 58 is substantially Y-shaped 
with the stem of the Y being pivotally attached at a first end thereof to 
the hinge link 50 and upper lift link 52 at their common point of 
attachment. The forks of the Y that form the scissors arm are affixed at 
their distal ends to the first ends of programming rods 60 and 62. The 
programming rods 60 and 62 are in turn pivotally attached at their 
respective second ends to the aircraft structure on either side of the 
first rotary actuator 46. The scissors arm 58 is pivotally connected to 
the hinge arm 54 by means of a pin 64 that passes through the prongs of 
the forked portion of the scissors arm at about the midpoint of the 
prongs. The pin 64 passes through a bushing 66 mounted in an aperture 
formed in the hinge arm. The scissors arm 58, hinge arm 54, adjustable rod 
56, and hinge link 50 form substantially a parallelogram, in side view 
with the altitude of the parallelogram varying as the door moves from its 
closed to its open position but with the parallel geometry being 
maintained throughout the door motion. The program rods 60 and 62 assist 
in developing the motion of the door as it swings from its closed to its 
open position such that the door moves laterally outboard as it swings 
upwardly to its open canopy position so that the door will clear the body 
skin of the aircraft. The second hinge means 16a is configured identically 
to the first hinge means 16 and is associated with a second rotary 
actuator 46a mounted on the door 10 spaced from the first hinge means such 
that there are symmetric points of attachment of the door to the aircraft 
structure. 
The rotary actuators 46 and 46a are preferably electrically powered and are 
of the nonreversing type, meaning that the actuator must be powered in 
both the clockwise and counterclockwise direction so that weight of the 
door in the open position will not backdrive the actuator. The actuator 
therefore must be powered in the reverse direction in order to move the 
door from its open to its closed position, thereby preventing inadvertent 
slippage of the door to the closed position with the potential of injury 
to cargo handlers and maintenance people working about the open door. As 
can be seen in FIG. 6, the first rotary actuator 46 comprises three 
separate components: a right side component 68, a left side component 70, 
and a center component 72. Typically, the rotary actuator is mounted by 
fixedly attaching the right and left members to the aircraft structure. 
The center member 72 then rotates upon the application of driving force to 
the actuator. The hinge arm 54 is fixedly attached to the center component 
72 of the rotary actuator 46 so that the hinge arm swings in direct 
proportion to rotation of the center component 72. The rotary actuator 46 
is driven by a power unit 74 mounted substantially centrally on the upper 
sill of the body cutout and drivingly coupled to the rotary actuator. The 
power unit 74 includes a bevel gear differential 75 coupled to the rotary 
actuators. The differential ensures that equal drive torque is applied to 
the two rotary actuators so that the door raises and lowers evenly. A 
first drive shaft member 76 is drivingly coupled at a first end to a drive 
coupling 80 that is in turn drivingly coupled to the center component of 
the rotary actuator 46. The second end of the first drive shaft member 76 
fits within a hollow portion of the first end of second drive shaft member 
78 and is held in place by a drive shaft bolt 82. The second end of the 
second drive shaft member 78 is coupled to a first output shaft 84 of the 
differential 75 such that the power unit 74 drives the drive shaft members 
through the differential. The second rotary actuator 46a associated with 
the second hinge means 16a and hinge arm 54a is similarly mounted to the 
aircraft structure and has a central rotating portion 72a fixedly attached 
to the second hinge arm 54a to move the hinge arm in swinging movement 
about the rotary actuator axis. The second rotary actuator 46a is coupled 
to a second output shaft 84a of the differential 75 by means of a second 
two-part drive shaft consisting of drive shaft members 76a and 78a in a 
like manner as described above. The differential 75 includes friction 
clutches 87 and 87a to provide equal torque to each rotary actuator. 
As can also be seen in FIG. 6, a ratchet wrench 84 is shown inserted into 
an opening in the left-hand member 70 of the rotary actuator 46. The 
ratchet wrench utilizes drive coupling 80 and drivingly engages a coupling 
associated with the movable center component 72 of the rotary actuator and 
is used in case of a failed power system to allow the door to be opened 
manually. The use of the ratchet wrench to open the door is a last-resort 
procedure and a primary manual drive system is also included which will be 
described in greater detail below. A second ratchet wrench 84a is 
associated with the second rotary actuator 46a. And it is necessary to use 
both ratchet wrenches in unison to open the door in the event of power 
failure, during the ratchet operation of the door each of the drive shaft 
members 76 and 76a is uncoupled from its associated drive shaft member 78 
and 78a by removal of the respective drive shaft bolts 82 and 82a. The 
rotary actuators are thus uncoupled from the power unit 74. The ratchet 
wrenches 84 and 84a are then engaged with the rotary actuators and cranked 
to drive the central portions 72 and 72a of the respective rotary 
actuators through a gear reduction, thereby moving the door to the open 
position. 
The primary auxiliary drive means is pictured somewhat schematically in 
FIG. 7. A flexible drive shaft 86 is drivingly coupled at a first end 
thereof to the power unit 74. The cable runs along the sill of the door 
and emerges at the outer skin spaced from the body cutout with the second 
end of the flexible drive shaft 86 mounted to a gearbox 88 mounted on the 
exterior of the aircraft so that with the door in the closed position it 
can be accessed by cargo handlers outside the plane. A drill motor or some 
other powered means can be coupled to the input of the gearbox 88 to drive 
the flexible drive shaft, which in turn drives the power unit 74 and turns 
the rotary actuators 46 and 46a thereby opening the door. Reversal of the 
drive motor coupled to the gearbox 88 will result in rotation of the 
flexible shaft 86 in the opposite direction which in turn will cause a 
reversal of rotation of the rotary actuators 46 and 46a causing the door 
to move from its open to its unlatched and lifted position. The gearbox 88 
and drive shaft 86 are the primary means of operating the door in the case 
of power failure. In the event of a problem with the gearbox 88 or 
flexible drive shaft 86, then the alternate manual method of opening the 
door with the ratchet wrenches 84 and 84a as described in the previous 
paragraph, can be employed. 
The movement of the door 10 from its closed and latched position to a 
lifted position at which it is clear to swing outboard to the open 
position is further illustrated in FIGS. 8 and 9. In the latched position, 
the upper edge of the door is in line with the body skin surrounding the 
door cutout. Also, the upper hook stops 44 are engaged with their 
associated clevises 40 attached to the upper edge 42 of the door 10. The 
unlatched and lifted position of the door is shown in FIG. 9. It can be 
seen that the upper edge of the door has moved upwardly so that it is now 
spaced from the body skin and the clevises 40 are released from the hook 
stops 44 so that the door is free to move laterally. 
The door of the present invention must move upwardly a sufficient distance 
to disengage the stop pins 26 mounted on the sides of the door from their 
position directly inboard of the stop pads 32 mounted on the sides of the 
body cutout. The upward movement of the door is provided by the 
interaction of a pair of rotatable latch cranks mounted on the first and 
second edges of the door with a pair of latch tracks affixed to the door 
frame. A first latch crank 90 includes a roller 92 engaged in a latch 
track 94 that is mounted on the first edge of the door frame. The latch 
crank 90 is in turn affixed to the end of a latch torque tube 96 that 
extends across the interior of the door. A second latch crank 90a is 
attached to a second end of the latch torque tube 96. The latch crank 90a 
has a roller 92a rotatably affixed to one end thereof, and with the door 
in the closed and latched position the roller engages a second latch track 
94a mounted on the second edge of the door frame. The latched position of 
the door occurs when the latch crank rollers 92 and 92a are 10 degrees 
over center. When they are in this position any upward movement of the 
door will drive the latch crank further toward the latched direction. 
Upward movement will therefore not inadvertently open the door. Stops are 
provided on the torque tube 96 to limit rotation in the latched and 
unlatched direction. In order to lift the door sufficiently for the door 
stop pins to clear the stop pads, the torque tube 96 is rotated, thereby 
rotating the latch cranks 90 and 90a causing the latch cranks to react 
against the latch tracks 94 and 94a that are affixed to body structure. 
The entire door assembly is thereby lifted. Referring now to FIG. 8, which 
shows a side view of the door in the latched position, the latch torque 
tube 96 has affixed thereto a bell crank 98, one end of which is attached 
to a control link 100, which in turn is affixed to a second bell crank 102 
attached at a first end thereof to a rod 104 extending from a linear 
actuator 106. The second end of the linear actuator 106 is affixed to the 
door structure. When it is desired to open the door, the operator 
activates the linear actuator 106, which in turn draws the rod 104 into 
the actuator thereby rotating the crank 102 and moving the link 100. This 
causes rotation of the torque tube 96, which in turn rotates the latch 
cranks 90 and 90a. The reaction of the latch cranks against the latch 
tracks lifts the door. A spring bungee 108 is mounted between the door 
structure and one end of a crank 110 affixed to the latch torque tube. The 
spring bungee provides resistance initially against movement of the door 
to provide a positive latch for the door. Once the door begins to move to 
the lifted position, the bungee assists in the movement. The bungee also 
ensures a positive latch of the door upon closing and relatching the door. 
The door of the present invention has a pressure-relief feature in that it 
has vents formed in the door 10 to allow the equalization of pressure 
within and without the aircraft. The pressure-relief vents are covered by 
vent doors that are in sealed relation over the vent openings and that are 
opened upon unlatching of the door to equalize pressure prior to opening 
of the door. Further, the vent doors are coupled to the latch torque tube 
96 such that if the pressure within the cargo compartment is greater than 
exterior pressure the vent doors cannot be opened, thereby preventing the 
doors from being unlatched and preventing possible blowout of the door by 
the pressure differential. Referring to FIGS. 10A, 10B and 10C, the 
pressure vent door-opening sequence is illustrated. In FIG. 10A the vent 
door 112 is shown in its closed position. A vent door push rod 114 is 
attached at a first end thereof to a bracket 116 at the base of the vent 
door 112. The door 112 is hingedly attached to the outer skin of the door 
by means of a vent door bracket 118. The vent door push rod 114 is 
connected to a vent door bias spring assembly 120 that biases the vent 
door into a closed position. The spring assembly is coupled by means of a 
second vent door push rod 122 to an L-shaped crank 124. The L-shaped crank 
is pivotally attached to the door at the apex of the L-shaped member. A 
cam 126 is fixedly attached to the latch torque tube 96 in such a manner 
that when the vent door 112 is in the closed position the latch torque 
tube 96 is prevented from complete rotation by the interference of a 
roller 128 mounted on the L-shaped crank 114 with a tab on the cam 126. 
As can be seen in FIG. 10B, if the internal pressure of the cargo 
compartment exceeds a predetermined amount, the vent door 112 will remain 
closed and the lift/latch linear actuator 106 will not have enough power 
to overcome the force on the vent door 112 so that the latch torque tube 
will not turn and the door 10 will be prevented from lifting to an 
unlatched position. If the internal pressure is less than a predetermined 
amount, the cam 126 will be rotated by the rotation of the latch torque 
tube and will force the L-shaped crank 124 to rotate under the force of 
the lift/latch linear actuator 106, thereby pulling the vent door push 
rods 114 and 122 to move the vent door to its open position as pictured in 
FIG. 10C. Upon latching of the door, the latch torque tube will be rotated 
to its initial position shown in FIG. 10A and the spring bias assembly 120 
will cause the push rod to move the vent door 112 to its closed position 
and at the same time the L-shaped crank will rotate to its original 
position as pictured in FIG. 10A. The vent door spring bias assembly 120 
also serves to prevent the internal body pressure from being not lower 
than a prescribed ambient pressure. Higher ambient pressure than body 
pressure, such as might occur in a rapid descent, will cause the spring 
bias assembly 120 to compress and allow the vent door to open to equalize 
pressure. 
Since it is necessary in the door opening sequence to first unlatch and 
lift the door, and then only after the door is in the lifted position, 
swing it outboard to its open canopy position, it is necessary to 
synchronize the application of power to the lift/latch linear actuator 106 
and the hinge power unit 74. A plurality of proximity sensors are placed 
at various locations on the door and frame to sense the position of the 
door and the lift/latch mechanism in order to properly sequence the door 
opening. When power is first applied to open the door, the power is 
applied to the lift/latch linear actuator 106 to move the door to its 
unlatched, lifted position. A proximity sensor 132 notes the movement of 
the door to the lifted position and another sensor 130 notes the movement 
of the lift/latch mechanism from the latched to the unlatched state. When 
the proximity sensor 130 senses that the door is in the lifted, unlatched 
position, power to the lift/latch linear actuator 106 is cut off and power 
is transferred to the hinge power unit 74 to power the rotary actuators 46 
and 46a to swing the door to its open position. Other proximity sensors 
134 are provided to sense when the door has reached the full open position 
at which time power is cut off from the hinge drive power unit 74. In like 
manner, when the door is to be closed, power is first applied to the hinge 
power unit 74 to move the door to its closed position. When proximity 
sensors 136 note that the door is in the body cutout power is shifted from 
the hinge power unit 74 to the lift/latch linear actuator 106 to operate 
the lift/latch actuator and rotate the latch torque tube, thereby rotating 
the latch cranks 90 and 90a to move the door into its latched position. 
When the proximity sensors 137 sense that the door is in its latched 
position power is cut off to the lift/latch linear actuator 106. Proximity 
sensor 139 senses that the door is in the cutout and proximity sensor 130 
senses that the door is latched. These sensors are also used to illuminate 
indicator lights in the cockpit to alert the crew as to the condition of 
the door. Typical locations of the various proximity sensors are shown in 
FIG. 7 and the proximity sensors themselves can be any suitable 
conventional proximity switch arrangement. 
In order to ensure that the door takes the proper direction upon unlatching 
and lifting, and again upon reestablishing its position within the body 
cutout, upper guide tracks 138 and 138a and lower guide tracks 140 and 
140a are provided on each side of the body cutout. Guide rollers 142 
mounted on the edge of the door 10 are fitted within the guide tracks when 
the door is in body cutout in the latched position. FIG. 11 illustrates a 
typical guide track 138 with a typical guide roller 142 lying within the 
channel formed by a rear guide member 144 and a forward guide member 146. 
As the door is unlatched, the guide roller 142 moves up the channel formed 
between the members 144 and 146 and then is enabled to move outboard along 
the uppermost portion of the guide member 146. Inboard motion is still 
prevented by the guide member 144 that extends a further distance in the 
upward direction than the forward guide member 146. 
Since the plug nature of the door is essentially dependent upon maintenance 
of the position of the stop pins 26 behind the door stop pads 32, it is 
critical that the door 10 be kept from vertical movement when in the 
closed and latched position in order to maintain the plug-type integrity 
of the door. While the lift/latch linear actuator maintains the door 10 in 
the latched position through the latching linkage, it is still preferable 
to have some additional means of preventing vertical movement of the door 
10 when the door is latched and the cargo compartment is pressurized. The 
door of the present invention includes detents formed on the forward 
members 146 of each of the guide track assemblies 140 as pictured in FIG. 
11. The roller 142 remains in approximately the center of the channel 
formed between members 144 and 146 when the door is in the latched 
position and the pressures within and without the cargo compartment are 
essentially equal. However, when the cargo compartment is pressurized, 
such as during flight, and the exterior pressure is considerably lower, 
the door 10 will be forced outboard by the pressure within the cargo 
compartment such that the roller 142 will be pressed against the forward 
member 146 at a point within the detent formed in the member 146. In order 
for the door to make vertical movement, it is necessary for the roller 142 
to overcome the resistance formed by the corner 148 of the detent whereby 
adding additional restraint against vertical movement. Each of the guide 
tracks is configured in a similar manner such that the total resistance 
offered by all four guide tracks is cumulative in providing vertical 
restraint. As shown in FIGS. 12 and 13 the outboardmost surfaces of the 
upper hook stops 44 and lower hook stops 34 are similarly detented to 
provide still more vertical restraint. 
An additional mechanism to stabilize the lift links when the door is in the 
open position, while at the same time providing additional vertical 
restraint when the door is in the latched position, is provided by the 
lockout upstop cam and lockout cam assembly. Referring to FIG. 14, the 
solid lines show the lockout system in the door latched position. A 
lockout drive crank 150 is affixed to the latch torque tube 96. A lockout 
push rod 152 is attached at a first end thereof to the lockout drive crank 
150. A second end of the lockout push rod 152 is attached to an upper 
lockout crank 154 such that rotation of the latch torque tube 96 will 
cause linear movement of the lockout push rod 152 and rotation of the 
upper crank 154. The upper lockout crank 154 is fixedly mounted on a 
lockout torque tube 156 that has affixed to a first end thereof a lockout 
cam 158 of generally hook shape. The second end of the lockout torque tube 
156 has affixed thereon a lockout up-stop cam 160 having a slot 162 formed 
therein. A clevis 164 is connected to the lower lift link 48 a and a 
roller support member 166 is also affixed to the lower lift link 48a at 
approximately the point of attachment of the lift link to the door. A 
clevis roller 168 is rotatably mounted within the clevis 164 and the 
second end of the roller support member 166 is attached to the clevis 
forming an acute angle and with the roller at the apex of the angle. The 
clevis roller 168 is captive within the slot 162 formed in the lockout 
up-stop cam 160. In the door latched position the roller 168 is located at 
the uppermost end of the slot 162. The location of the roller within the 
slot prevents vertical movement upwardly of the door with relation to the 
hinge linkage. A similar clevis and roller support assembly comprised of 
clevis 164a and roller suppport member 166a is mounted on the lower lift 
link 48 in proximity to the lockout cam 158. Upon rotation of the latch 
torque tube 96, the lockout torque tube 156 is also rotated causing 
rotation of the lockout cam 158 into engagement with the clevis roller 
168a associated with the lower lift link 48. At the same time the clevis 
roller 168 is now positioned at the lowermost end of the slot 162 formed 
in the lockout up-stop cam 160. The lockout system, comprised of the 
lockout cam 158, lockout up-stop cam 160, lockout torque tube 156, and 
lockout push rod 152, provides stability to the lift links when the door 
10 is in the open position and supports the weight of the door through 
rollers 168 and 168a when the door is out of the cutout. In the open 
position the door is constrained from moving inboard, that is, toward the 
body of the aircraft, by engagement of the lockout cam and the lockout 
up-stop cam with their associated clevis rollers. 
While a preferred embodiment of the door of the present invention has been 
discussed and illustrated, it will be clear to those of ordinary skill in 
the art and others that changes can be made to the described and 
illustrated embodiment while remaining within the scope of the present 
invention. The invention should therefore be defined solely with reference 
to the appended claims.