Abstract: A landing gear assembly is provided for use on a model helicopter. The landing gear assembly includes a landing gear strut having a leg portion and a foot portion connected to the leg portion to define an included right angle therebetween. The assembly also includes a landing gear skid formed to include a landing gear strut attachment area provided with an L-shaped slot arranged to receive and trap the foot portion of the landing gear strut therein.

Abstract: An elastomer landing gear pad assembly (20) and method of reducing loading of installation fasteners (17) including a cap (15) and an elastomer pad (21) including a crown (22) on at least one edge thereof extending between the top (26) and at least one of the peripheral sides (24). Upon tightening the fasteners (17), the crown (22) comes into progressive contact with the contact surface thereby compressing the pad (21). The crown minimizes stress buildup in the fasteners upon substantial compression of the pad.

Abstract: A main landing gear system which employs Ackermann type steering utilizing kingpins and tierods wherein a plurality of paired wheels are employed and wherein each truck axle is adapted for independent steering. Electronic control means along with hydraulic directional valve means are utilized. A main landing gear having single wheel or king pin steering. Pivot pin tilting is utilized in truck type main landing gear, e.g. where a truck axle is adapted for independent steering or where single wheel or king pin steering is utilized.

Abstract: A fixed wing aircraft that can be automatically and rapidly converted to a roadway vehicle within seconds while driving in the highway, comprising a one-piece wing rotatably mounted on top of the fuselage. The aircraft features a 3-horizontal-surface design allowing good pitch stability and damping in a very short fuselage, stall-resistant feature and reduction in induced drag at cruise speed. The aircraft's wing is enlargeable with additional wing tip segments allowing boost in aspect ratio hence improving efficiency at high loads. The vehicle has low center of gravity, four wheels with independent suspension, nose-height leveling for take-off and landing, and anti-sway mechanism in order to prevent roll-over in a tight turn. Ground propulsion is by both a ducted fan and hydraulic rear wheel drive allowing rapid accleration in the roadable mode.

Abstract: Disclosed is an apparatus for displaying state and transition state information of mechanical equipment. A sensor and display system is provided for displaying aircraft landing gear status and other mechanism status. In one embodiment, the system utilizes two light emitting diodes (LEDs) for each landing gear leg to display the current position of each gear leg. One yellow LED indicates gear UP and the second green LED shows gear DOWN position. When the control switch is moved to change the position of the gear, the indicator light which had been lit is extinguished, and the indicator for the desired position begins to flash, indicating gear movement. The indicator will continue to flash until the gear leg has reached the limit of travel, at which time the indicator stops flashing and glows steadily. Each gear leg indicator operates independently of the others, so that proper position of each gear leg can be confirmed and any malfunction can immediately be identified.

Abstract: A main landing gear system which employs Ackermann type steering utilizing kingpins and tierods wherein a plurality of paired wheels are employed and wherein each truck axle is adapted for independent steering. Electronic control means along with hydraulic directional valve means are utilized. A main landing gear having single wheel or king pin steering. Pivot pin tilting is utilized in truck type main landing gear, e.g. where a truck axle is adapted for independent steering or where single wheel or king pin steering is utilized.

Abstract: A shock absorber, optionally operable as a retractable landing gear actuator, includes a sealed cylinder divided by a cylinder head to define an upper chamber and a lower chamber, the lower chamber further divided by a piston having a piston rod passing in sealed manner through the lower cylinder end. The cylinder head includes one or more orifices, the effective opening of each orifice controlled by a valve, the valve having a stem attached to and passing through the upper cylinder end to the atmosphere, such that the pressure between the piston and the cylinder head is limited to a certain value above atmospheric pressure, regardless of the velocity or position of the piston. The valve is forced toward the closed position by a spring against a stop such that it is always at least partially open. During hard or crash landings, high fluid pressure on the piston or in the upper chamber forces the valve further open.

Abstract: A wheel-type landing gear is disclosed for helicopters with fastening measures on the helicopter which permit a receiving of the wheel-type landing gear on the craft at fittings provided for the fastening of skid-type landing gear without any additional support. The possibility of retrofitting and/or backfitting the helicopter is provided. The main wheels are fastened on rocker arms so that the wheel contact point is situated clearly behind the rearward landing gear fittings.

Abstract: The present invention is provided to overcome the difficulties of a conventional tail wheel-type airplane such as the remarkably inferior straight ground-run properties during a take-off run (particularly, low-speed taxiing), and the extremely difficult control during the take-off run. A mechanism of the present invention is structured such that left and right coaxial gears and main wheel gears (or connection gears) are engaged together when not stepping on rudder pedals in take-off and landing run. Under this operation, since the above gears themselves are engaged together, left and right main wheels rotate synchronously through a co-axis, and as a result, an airframe makes a straight ground-run. When stepping on the rudder pedals in taxiing, the coaxial gears and main wheel gears (or connection gears) are disengaged from each other, the left and right main wheels then rotate independently, and as a result, the airframe easily taxis (i.e., a case of turning the airframe right or left).

Abstract: Landing gear axle steering for an aircraft having a six wheel three axle truck. A set of wheels driven about a vertical shaft utilizes a single actuator alone without a walking beam.

Abstract: Aircraft components utilize flexible fluted extruded twin wall plastic sheet to form aileron hinges, horizontal staibilizers and elevators, vertical stabilizers and rudders, compound landing gear, struts, and control systems which are lighter in weight and lower in cost than previously available structures. The landing gear has damping characteristics superior to previous gear. The invention is particularly well suited to remotely controlled flying model aircraft.

Abstract: A shock strut assembly for an aircraft landing gear includes a trunnion fitting, a compressible oleo strut subassembly, a wheel subassembly, an energy dissipating subassembly, and a mechanical load control subassembly. The oleo strut subassembly includes a cylinder member having an upper end mounted in combination with the trunnion fitting by means of the mechanical load control subassembly and a piston member having a lower end affixed in combination with the wheel subassembly and an upper end slidably inserted in the cylinder member. The energy dissipating subassembly includes a cylindrical cutter member secured in combination with the cylinder member and the trunnion fitting and a frangible tube member mounted in concentric combination with the cylinder member so that the lip of the upper end thereof is disposed in abutting engagement with the cutter member.

Abstract: An aircraft control system for an unique-trim, model-following system includes a feedforward shaping function that provides quickening of pilot input, and an automatic trim function that accommodates return of the cockpit controller to an unique, centered position during trimmed flight. The basic control law is reconfigured in response to the changing state of landing gear contact to support transitions between ground state and fly state conditions. The state of the landing gear is monitored continually to recognize the occurrence of initial ground contact and whether the aircraft is constrained about a rotational axis due to ground contact. The control is altered progressively as the transition proceeds so that command of the control surface is consistent with the degree of constraint imposed by ground contact.

Abstract: A vertical takeoff and landing heavier-than-air aircraft that includes a gyroscopic airfoil in the airstream of a ducted fan to cause vertical lift to the aircraft. The gyroscopic foil is both rotatably and pivotally attached to the aircraft such that it can be titled to provide directional control of the aircraft and, in at least one embodiment, has an adjustable airfoil forming part of the gyroscopic device such that the lift can be varied.

Abstract: A landing pad system for absorbing horizontal and vertical impact forces upon engagement with a landing surface (15) where circumferentially arranged landing struts (12) respectively have a clevis (24) which receives a slidable rod member (13) and where the upper portion of a slidable rod member is coupled to the clevis by friction washers (30,32) which are force fit onto the rod member to provide for controlled constant force energy absorption when the rod member moves relative to the clevis. The lower end of he friction rod is pivotally attached by a ball and socket (44) to a support plate (42) where the support plate is arranged to slide in a transverse direction relative to a housing which contains an energy absorption material (50) for absorbing energy in a transverse direction.

Abstract: A way to make model/experimental planes crash proof by a shock absorbing harness mounted over the body of the plane, which does not significantly affect the flying abilities and qualities of the model/experimental.The harness protects against collision with ground or other objects by strategically placing shock absorbing structures on the body of the aircraft. These structures are protruding from the overall outer dimension of the model/experimental aircraft and are the ones to first hit external objects and the ground. These shock absorbing structures are made of material that is light and provides the resiliency and cushion against the impact to the model/experimental body. The design is such that they add very little weight and drag to the model/experimental aircraft. The structures are made of thin wires and resemble an inverted question mark in its basic configuration.

Abstract: The landing gear for an aerodyne, and especially for a helicopter (H), is of the type including lateral members (4) for contact with the ground, such as skids, skis, floats or similar members. The members (4) are linked to the fuselage of the aerodyne (H) by at least two crosspieces (2, 3) of composite material. The crosspieces are produced in a laminated material having high elastic absorption capacity. They have a sharply curved shape in the area of their central parts by which they are linked to the fuselage of the aerodyne (H), the link (5) between each of the crosspieces (2, 3) and the fuselage being a link with longitudinal embedding with respect to the aerodyne. The lateral members (4) for contact with the ground are linked to the crosspieces (2, 3) by means of articulation (17, 18) which allow large deformations of the crosspieces (2, 3) without torsion of the lateral members (4).

Abstract: A landing apparatus for use with helicopters comprises a substantially J-shaped cantilevered landing skid having a cantilevered portion and a mounting portion. The cantilevered portion is attached at one end thereof to the mounting portion and extends substantially perpendicularly away the mounting portion. The mounting portion is mountable on a rear portion of an aircraft so that the cantilevered portion can extend forwardly underneath the aircraft.

Abstract: Landing gear for aerodynes and especially helicopters comprising two lateral members (2) for contact with the ground being linked to the fuselage of the aerodyne by at least two crosspieces (3, 4). These crosspieces (3, 4) are produced as a bundle (7) of unidirectional synthetic fibers sheathed by a skin (8) of tissues of fibers which are crossed with respect to the unidirectional fibers of the bundle (7). The extremities (9) of the crosspieces are embedded in the lateral members (2) for contact with the ground. The structural links between the crosspieces (3, 4) and the fuselage of the aerodyne (H) allow the pivoting of the crosspieces (3, 4) about transverse axes of the aerodyne (H).

Abstract: The invention relates to a device for increasing the stability, especially the lateral stability, of a helicopter placed on board (1) having a tricycle landing gear (2, 6), when it is set down on a moving platform.The device comprises two lateral stabilizers (13), each equipped with a wheel (16) for support on the platform and connected to the structure of the helicopter by an essentially rigid support, comprising a leg (17), about the axis of which the wheel (16) can turn, the leg (17) itself being connected to the structure by a rigid and transverse component which may be a pivot axle if the leg can be raised, or a slidingly fitted arm if the stabilizer (13) is additional. The stabilizers may also be integrated into a towing trolley.Application to the equipment of helicopters placed on board, having a tricycle landing gear.

Abstract: The locking device of the invention comprises a locking device mounted to pivot relative to a beam and having ends associated with an axle to lock the axle in a first position of the locking device and to release the axle by the locking device pivoting towards a second position, together with a control actuator and a set of two links for controlling the position of the locking device.

Abstract: A landing gear for an aircraft has a multi-wheeled truck that is swung by a main prop from a stowed position to a lowered position below the aircraft. The truck is pivotably connected to the lower end of the main prop. When the gear is lowered, at least one rear prop extends between the upper end of the main prop and an aft region of the wheel truck. Both the main and rear props are telescoping members. However, the rear prop is releasably lockable to hold a certain fixed length when the aircraft is on the ground, so as to prevent pivoting movement of the wheel truck relative to the main prop. This impedes the ability of the aircraft to tip back when its center of gravity shifts aft during unloading.

Abstract: Airplanes which feature composite construction and have: a further aft than conventional center of gravity; a clean wing with a high aspect ratio; and all primary flight controls. These include trailing edge control segments (or elements) which extend the full span of the airplane wing. A central processor so schedules the upward and downward deployment of the control elements that: (1) downward and upward displacements of the control elements are respectively accompanied by pitch-up and pitch-down moments; (2) the inboard control elements are used primarily to change the coefficient of lift whereas roll control is effected principally by displacement of the outboard control elements; and (3) each of the control elements is individually displaced by a system which eliminates hydraulic systems and control cables. Hallmarks of these novel airplanes include simplicity, relatively low cost, lower weight, and safety.

Abstract: An aircraft securement device includes a sliding shaft, typically mounted to the aircraft landing gear. The shaft resembles a harpoon and is lowered through a wire grid when deployed. Tab-like members spring outwardly from the lower shaft end and engage the lower surface of a grid so as to retain the aircraft thereto.

Abstract: A tail sitter aircraft of a type that takes off and lands on its tail section with the fuselage pointed vertically upward has landing gears located on its rearward end. Each of the landing gears is mounted on a support axis which is offset from the fuselage axis and which intersects a wheel axle at a 90 degree angle. The landing gears are located on the tail section and spaced around the fuselage axis. Two of the landing gears which are opposite each other will be locked so that they can roll only along a single straight line. The other two landing gears, which are also spaced opposite each other, are locked so that they can roll only on a single straight line. The straight lines are perpendicular to each other.

Abstract: A quick change wheel landing gear assembly (10) is provided as a replacement for a skid landing gear system on a vertical take-off and landing aircraft. The wheel landing gear assembly (10) includes a pair of spaced-apart fore and aft longitudinal tubes (16, 18) attached to a pair of short, spaced-apart cross tubes (20, 22) that are adapted to mount on the structural saddles (12, 14) used to mount the skid landing gear on the underside of the aircraft. The longitudinal tubes (16, 18) are connected together at the forward end for mounting a fully swiveling nose gear (26) thereto. Aft main gear wheels (30, 32) are mounted on cantilever landing gear legs (34, 36) that extend laterally from the longitudinal tubes (16, 18) adjacent the aft cross tube (22). Landing loads on the landing gear may be absorbed by resilient springs (25), deflection of the gear legs (34, 36) and the aft cross tube (22), torsion of the fore and aft longitudinal tubes (16, 18), or any combination of these actions.

Abstract: A vertically mounted deflector attached to a landing gear, that prevents debris from being thrown by the tires into the engine of an aircraft. The deflector has two vertically mounted plates that have oblique stepped surfaces facing the tires.

Abstract: A vertical take-off and landing aircraft is configured so as to provide, when landing tail-first with its fuselage (1) in a generally vertical attitude, a touchdown area (21) at the tail of the aircraft at a position offset from a line extending along the length of the fuselage through the centre of gravity (23) of the aircraft such that after the touchdown area contacts a landing surface the aircraft topples under the action of gravity to bring an undercarriage (11, 13) of the aircraft into contact with the landing surface, thereby to attain a stable landed position.

Abstract: A retractable landing gear is arranged so as to provide, in use, a highly inclined shock absorber while avoiding high shearing stresses on the shock absorber. The landing gear includes a pivoting panel fixed to an aircraft structure to pivot about a raising axis; a shock absorber including a strut fixed to the pivoting panel so as to pivot relative thereto about a tilt axis, and a sliding rod mounted to slide in the strut and carrying a set of wheels at its bottom end; and a coupling member connected to the pivoting plate and to the bottom end of the sliding rod. Also included is a mechanism for raising and holding the landing gear.

Abstract: A removable spoiler is described for reducing the rotorblade or wing lift of parked aircraft. It includes an airfoil cover with an inflatable aircell installed that is temporarily mountable to project into the airflow on the top of the rotorblade or wing. It extends for the greater portion of the lift generating surface of the rotorblade or wing to which applied.

Abstract: Device for increasing the lateral stability of a helicopter having a tricycle landing gear (2, 6), when it is set down on a moving platform. The device comprises two lateral stabilizers (13), each equipped with a wheel (16) for support on the platform and connected to the structure of the helicopter by an essentially rigid support, comprising a leg (17), about whose axis the wheel (16) can turn, the leg (17) itself being connected to the structure by a rigid and transverse component which may be a pivot axle if the leg can be raised, or a slidingly fitted arm if the stabilizer (13) is additional. The stabilizers may also be integrated into a towing trolley.

Abstract: Auxiliary landing equipment for aircraft which comprises a plurality of inflatable cushions arranged in a predetermined array relative to each other and structure for securing them to the aircraft so that, in an inflated state, the cushions can contact the ground during landing or on take-off and so that, in a deflated state, the equipment can closely follow the contour of the aircraft part to which it is attached.

Abstract: This invention relates to a rolling system for aircraft, comprising telescopic landing gears which abut on the ground via wheels and which present a variable length as a function of the load applied thereto by said aircraft. According to the invention, this system comprises at least one jack assembly capable of outwardly pressing at least one rolling member with a constant force and said rolling member is placed in contact with the ground only after impact of the telescopic landing gears and when the length of said telescopic landing gears corresponds to a predetermined load threshold applied thereto, said threshold being less than the load corresponding to take-off.

Abstract: Initial retraction of telescoping cylinders (22, 72) forces hydraulic fluid through an orifice area into a low pressure chamber (116). When the cylinders (22, 72) reach a predetermined position, a stop surface (120) carried by the second cylinder (72) engages a floating member (52) carried by the first cylinder (22). Further retraction causes the floating member (52) to move relative to the first cylinder (22) and compress a high pressure chamber (44). When the shock strut (20) is pivoted into a stowed position, the cylinders (22, 72) are retracted to the predetermined position without compressing the high pressure chamber (44). In a second embodiment, a linkage mechanism (298) moves the high pressure chamber (318) relative to the first cylinder (272) to allow the shock strut (220) to be shortened beyond the predetermined position without compressing the high pressure chamber 318.

Abstract: An RPV for use on shipboard, the RPV having a lower support (for example a plurality of legs) comprising a plurality of broad pads at the lower end, a downwardly extending probe (or finger) extending from each pad, the lower end carrying wings within the probe that may be extended from the probe to extend laterally for securing below a grid through which each probe (or finger) may extend.

Abstract: Axial motion of the wheel assembly of a flat-spring undercarriage for vertical-lift aircraft is provided to permit proper deflection of the flat spring so as to effectively cushion the touchdown of such an aircraft from a hover.

Abstract: A landing gear load sensor (24) for an aircraft (10) having a skid type landing gear (14) is provided. The sensor (24) includes a shear beam (30) having a loadbearing area (40). Structure (32, 34) is provided for mounting the shear beam (30) to the aircraft (10), such that the loadbearing area (40) is disposed adjacent the landing gear (14). Structure (50) is disposed on the shear beam (30) between the mounting structure (32, 34) and the loadbearing area (40) for sensing shear load on the shear beam (30).

Abstract: A method and system for reducing stopping distance for an aircraft on a wet runway, which includes blowing away water on a wet landing surface in front of the aircraft tires so that the tires contact a relatively dry surface and simultaneously blowing air on the tires to remove water that may have collected on them. The system includes ducting from the aircraft engine to the landing gear to receive high pressure air bled from the aircraft engine and nozzles connected to the ducting for exhausting high pressure air to the runway in front of the wheels and to the rear portion of the tires. A system of valves in the ducting can be actuated by switches in the cockpit to bleed high pressure air from the engine to the ducting and nozzles during landing of the aircraft.

Abstract: A high energy absorbing aircraft tail skid assembly for protecting an aircraft fuselage lower skin portion from damage in the event of a tail strike due to over rotation on take-off of the aircraft. The high energy absorbing tail skid assembly is pivotally mounted to the aircraft bulkhead, and comprises a telescoping rod assembly including a crushable aluminum cartridge, positioned coaxially with respect to the central axis of the telescoping rods. The telescoping rod is coupled through linkage, including a fuse pin providing a predetermined failure mode for the high energy aircraft tail skid assembly, to prevent overloading critical aircraft structure.

Abstract: A flying platform, propelled by at least one ducted fan causing a vertically downwardly directed airstream in and through a cylindrical duct. A vane system in the duct has two mutually perpendicular pairs of diametrically opposite first vanes, each extending in from the duct rim toward the center of the duct. Each pair of first vanes provides a pair of generally vertical walls parallel to a diametral line across the duct, and they define duct passages between the pairs of vanes and define quadrants between adjacent pairs. Each first vane has an upper, fixed, rigid portion and a variable camber flap depending therefrom. A first servomotor with linkages vary the camber of each pair of flaps, so that the camber of the flaps of each pair is at all times the same amount but in opposite directions. Preferably, there are also four second vanes, one bisecting each quadrant, and a symmetric pair of spoilers is mounted on each second vane.

Abstract: An attachment lug is fixed to the end region of a cylindrical body, such as a power cylinder, a piston-cylinder combination or the like, to form an assembly wherein loads directed on the attachment lug are transmitted to the cylindrical member. The attachment lug comprises a fork portion of shell-type design on which a first conical surface is formed. A second conical surface is formed on an end region of the cylindrical member, the first and second conical surfaces having corresponding configurations adapted to mate with each other. The attachment lug is connected to the end region of the cylindrical member with the first and second conical surfaces mating with each other, the first and second conical surfaces being joined to each other by a bonding agent. The shell-like fork portion of the attachment lug is formed of a composite material, such as a thermosetting plastic reinforced by a continuous fiber structure.

Abstract: A jump strut landing gear apparatus for providing an aircraft with a short takeoff and landing capability, utilizes incrementally fired, pyrotechnic charges to explosively generate the required compressed fluid to drive the apparatus.

Abstract: The flexible girder made of composite materials and with high energy absorption is in the form of an elongate box of laminated structure comprising two rigid flanges (6,7) connected by two webs (9) which have aligned apertures (13). A deformable energy-absorbing block (14') is arranged between the two flanges (6,7) at the apertures and comprises a block of an elastomeric material (15). The block (14') absorbs the buckling deformation energy of the flange (6) which is subjected to compressive stress during flexion of the girder, by resting on the other flange (7) which is subjected to tensile stress. The block (14') controls the buckling of the flange (6) and only gives back part of the energy absorbed. Application to the equipment in particular of skid landing gear for helicopters and tail skids for aircraft.

Abstract: An extendable shock strut comprising a strut housing having an open end and a closed end and a piston including a piston housing and a piston head slidable in the strut housing. The piston housing and the strut housing are adapted to move a selected distance relative to one another under normal usage. A source of high pressure gas is provided coupled to the shock strut for rapidly driving the strut housing and the piston housing relative to one another to an extended position. In a particular embodiment of the invention, an expandable chamber is formed from the closed end of the strut housing and a secondary piston slidable in the strut housing and positioned between the closed end of the strut housing and the piston head. The high pressure gas rapidly expands the chamber and drives the secondary piston toward the piston head to cause the piston housing and the strut housing to move relative to one another to the extended position.

Abstract: The landing gear comprises: a rod including nested first and second tubes between which there slides a cylinder whose outer end supports a running gear; a strut surrounding the top of the rod and including a steering mechanism cooperating with a rotary tube disposed between the rod and the strut; and a fluid actuator constituted by at least one chamber between the strut and the rod and having a feed inlet only. The landing gear is particularly applicable to helicopters that are required to "kneel down" camel fashion, e.g., for storage in the hold of an aircraft carrier or a cargo plane.

Abstract: A combination landing gear door and splash guard for an aircraft landing gear which includes a linkage to control the clearance between the door/splash guard and a runway surface with respect to the extension of a shock absorbing strut of the landing gear.

Abstract: An aircraft undercarriage unit which includes an upper leg member 1 arranged for attachment to an aircraft body 4, a lower leg member 2 in axially slidable association with the upper leg member 1 to form a telescopic shock absorber, ground wheel means 6 carried by the lower leg member 2 and a sleeve member 13 through which the lower member extends and into which the upper leg member 1 may protrude. The sleeve member has anchorage means 17, 18 through which towing loads may be accepted and transmitted respectively.

Abstract: The invention concerns a landing gear. The landing gear is characterized essentially by the fact that it comprises at least one shock absorber (15), this shock absorber being mounted in the leg (1) and casing (2) assembly by means of two convex surfaces (22, 31) made on the cylinder (16) of the shock absorber (15) and cooperating with two concave surfaces (25, 32) integral respectively with the leg (1) and the casing (2). This landing gear finds an application as a nose gear of the rocker-beam type.

Abstract: A landing gear for ultralight aircraft includes a main landing gear assembly disposed in a position relative to the longitudinal axis of the aircraft to permit either tail wheel type landing or tricycle landing operations with the assembly including an arched axle wherein the arch provides a spring for the landing gear as well as provides clearance to enable foot launching of the aircraft. A nose wheel strut assembly is linked to and extends forward of the main wheel landing gear assembly and includes a resilient tension link member.

Abstract: Production of a downwardly and forwardly directed reverse thrust discharged from a reverse-thrust duct is controlled .Iadd.during landing .Iaddend.by a door in the rearward-discharge duct having its rearward portion pivotally mounted for swinging of its forward portion between a position lodged in a recess in the side of the rearward-discharge duct and a position in which the forward edge of the door is spaced from the recess and the door is inclined to deflect jet exhaust from the rearward-discharge duct into the reverse-thrust duct branching from the rearward-discharge duct. The discharge end of the reverse-thrust duct can be closed by a second door and actuating .[.means.]. .Iadd.mechanism .Iaddend.interconnecting the two doors can move them simultaneously through proportionate degrees of movement.