Patent Description:
One type of aircraft arresting system that is used to decelerate an aircraft functions by extending a cable across the runway. These systems are often installed on runways (commercial or military) where aircraft equipped with a tailhook may need to land. In use, the tailhook of the aircraft can engage the cable in order to bring the aircraft to a safe stop in the event of an emergency condition.

A typical aircraft arresting system consists of an energy absorber (braking system) with a reel of tape and a runway edge sheave to align the tape vertically with respect to the runway surface. This is illustrated by <FIG>. These components are located on opposite sides of the runway, with one set of components on each side. As shown by <FIG>, the tape, originating from tape reels on the braking system, is fed through the runway edge sheaves. The tapes on either side are connected to a cross-runway cable via a tape connector interface. During an arrestment event, the tape pays out from the reels and travels across the runway.

The current runway edge sheave configuration provides the runway edge sheave/fairlead beam mounted to a concrete foundation along sides of the runway. This installation configuration also typically consists of permanently-installed concrete ramping on either side of the sheaves. This ramping is provided to accommodate accidental or occasional rollover of the runway edge sheave by aircraft. This runway edge sheave and ramping configuration is installed permanently above ground. According to International Civil Aviation Organization (ICAO) recommendations, this permanent above ground configuration is considered an airfield obstruction.

In other systems that remain above ground, the cable is typically supported slightly above the runway (approximately <NUM> inches), making it more accessible to the aircraft tailhook. Positioning the cable above the runway can help prevent a "hook skip," where the aircraft's tail-hook fails to catch the cable. In some systems, this cable support is provided by rubber "donuts" that are spaced along the length of the cable. The donuts lay directly on the runway surface, which exposes the cable to continual run-over by aircraft. This can cause damage to both the cable and to the runway surface. Due to the fact that it creates an obstruction, the donut-supported cable is another type of airfield obstruction.

Some designers have attempted to provide below ground sheave systems. One attempted solution has included a Retractable Hook Cable Support System (RHCSS). Portions of the system are described by materials from Marshall of Cambridge Engineering Ltd. This system can be used to protect the cable and the runway surface by housing the cable in a cross runway trough during standard flight operations. Support boxes are spaced across the width of the runway. Prior to an arrestment event, the boxes raise the cable into position above the runway to allow tail hook engagement. When the cable is not in use, it lies within the cross runway trough. In this lowered position, the retractable hook cable support system is ICAO compliant.

An even earlier example of a below ground system is illustrated by <CIT>. In this patent, the inventors provided a below ground sheave system that retracted into a pit prior to activation. The cover was locked in a closed position with the payout element (connected to a cross runway cable) tensioned therebeneath. When an aircraft touched down and engaged the cable, the pre-tensioned payout element was further tensioned sufficiently during the initial phase of arrestment to exceed the predetermined upward force, which released a latch lock that allowed the cover assembly to rise from the pit in response to the tensioning. Release of the latch elevated the sheave above ground during arrestment. However, the sheave system was not activated until the time that the aircraft touched ground. Raising of the sheave was due to tension alone, not a raising and lowering system. <CIT> describes a retractable support that incorporates an inclined plane <NUM> on which rests a cable support <NUM> that pivots about an axis <NUM>, into a channel <NUM> that extends across the runway. D1 provides the cable raising features along the runway itself, not the runway edge. <CIT> describes a hook cable support assembly that is mounted beneath the landing surface, not at the runway edge. A circular opening <NUM> in each support block <NUM> receives the arresting cable. The support arm is rotatable downward in response to an aircraft wheel contacting the support block <NUM>.

Even in light of these attempts, there are currently no available runway edge sheave solutions that conform to ICAO guidelines. Earlier attempts at below ground systems have been unsuccessful. Existing runway edge sheave installations are all thus mounted above ground, causing an obstruction and are not compliant with ICAO guidelines. Improvements are desirable.

According to certain embodiments of this disclosure, there may be provided a retractable sheave system according to claim <NUM>. In other examples, the hinge associated with the elongated beam may be a side hinge. In other examples, the elongated beam may receive tape in a generally horizontal position. The at least one vertical sheave is configured to rotate the tape moving through the elongated beam about <NUM>°, such that the tape enters the elongated beam in the generally horizontal position and exits the elongated beam in a generally vertical direction.

The beam may comprise a lifting plate. The foundation may comprise one or more restraint plates for securing the beam in position.

In some examples, there are also provided side ramp portions operatively secured to the beam. Raising of the beam also results is raising of the side ramp portions, and lowering of the beam results is lowering of the side ramp portions. For example, side ramp portions are hinged to sides of the beam, such that raising of the beam results in corresponding raising of the ramp portions. The side ramp portions may be hinged to the beam and are slidable with respect to the foundation. There may be provided guards to cover open spaces between the foundation and ramp portion edges when the beam is raised.

The lifting/lowering mechanism comprises a pneumatic system, hydraulic system, electrical actuation, or mechanical actuation, or actuation via an airbag system.

There may be a tape connection positioned at a forward portion of the beam.

The described embodiments provide a retractable runway edge sheave system. The disclosed system may be used in conjunction with a retractable hook cable support system (RHCSS). The retractable runway edge sheave system is capable of raising the runway edge sheave above ground and placing it into battery (arrestment ready) position. It can then be retracted (lowered) below grade or flush with the runway in order to meet various regulations or guidelines when not in use. The RHCSS may also raise and lower to match the positioning of the retractable runway edge sheave. These systems work in cooperation with one another. Having a condition where the cable is raised but the sheave is lowered would be considered hazardous to an aircraft with its tailhook lowered for an arrestment. There may be a slight synchronization delay between both systems finding their fully raised or lowered positions, but they are both generally either fully raised or retracted for safe operation.

The disclosed retractable runway edge sheave is designed to raise the runway edge sheave into the battery position while maintaining the alignment of the tape path to a designed location above the center of the runway. It is necessary to maintain a degree of tension on the cable while in the raised, arrestment ready position, such that it does not sag to the degree that it lays on the runway surface. Typically, runway edge sheaves are aligned to a designed height above the crown or center of the runway surface in the case of a single slope runway. They must also be designed to ensure that they can support sufficient tension maintained on the cable to prevent the cable from sagging onto the runway surface. The tensile force is typically applied by a tape rewind system of the energy absorber and is transmitted through the tape and out to the cross runway cable. The tape should be positioned centrally on the sheaves and not biased toward the edges where rubbing and binding can occur. Such interferences can cause wear to the edges of the tape and a degradation of its strength.

The disclosed retractable runway edge sheave may also feature an optional ramping device that follows the runway edge sheave into the raised and lowered positions. The ramping device may help protect aircraft that have veered off the runway from damage incurred by striking the raised runway edge sheave directly.

<FIG> illustrates one example of an elongated beam <NUM> that may be used in accordance with this disclosure. As shown, the beam is a fairlead beam that receives the tape from an energy absorber at a rear sheave that is generally horizontal. A forward set of vertical sheaves may be provided such that the tape is rotated about <NUM>° within the sheave. This can help with alignment of the tape so that the tape connector interface to the cable is positioned as desired.

Referring now to <FIG>, there is shown a retractable runway edge sheave system <NUM>. The system is configured to be installed within a stable foundation <NUM>. Foundation <NUM> will typically be a concrete foundation, similar to the type of foundations onto which runway edge sheaves are currently mounted above ground. The foundation <NUM>, however, defines an internal cavity area into which the retractable runway edge sheave system components are mounted. <FIG> illustrate the retractable runway edge sheave system <NUM> in its raised position. <FIG> illustrate the retractable runway edge sheave system <NUM> in its retracted/lowered position.

Referring now to <FIG> and <FIG>, the retractable runway edge sheave system <NUM> has an elongated beam <NUM> that functions as the sheave. In specific examples, a fairlead beam may be housed within the elongated beam <NUM>. The elongated beam <NUM> is raised and lowered within the cavity via a mechanism <NUM>. The mechanism <NUM> may be a lifting and lowering mechanism that functions via hydraulic operation, pneumatic operation, electrical operation, mechanical operation such as airbag inflation or gear and pulley system, or any other appropriate lifting and lowering system. Although two lifting mechanisms <NUM> are illustrated by <FIG>, it should be understood that there may be a single mechanism or multiple mechanisms, depending upon the weight of the system and the design of the raising linkages. Additionally, although mechanisms <NUM> are illustrated as positioned below elongated beam <NUM>, it is possible that the mechanisms may function from the side or an upper area of the beam. The elongated beam <NUM> is mounted within the cavity along a rear portion <NUM> via a hinge <NUM>. When the mechanism <NUM> is activated, the elongated beam <NUM> pivots up with respect to the hinge <NUM>. This can be viewed by the side view of <FIG>. The tape that enters the beam <NUM> may travel underground in a tube as it is directed to the foundation <NUM>.

A forward portion <NUM> of the elongated beam <NUM> has a tape connector <NUM> onto which the cable <NUM> is secured. Forward portion <NUM> of the elongated beam <NUM> also defines a lifting plate <NUM>. Lifting plate <NUM> moves along with elongated beam <NUM>. A forward portion of the lifting plate has a lip area <NUM>, which provides a shelf for the tape connector when the system is raised. The lifting plate <NUM> and lip <NUM> may fit into a recessed area of the foundation <NUM>.

The figures also illustrate left and right ramp portions 32a, 32b. Ramp portions 32a, 32b may be hinged to sides of the elongated beam <NUM>. <FIG> shows a side view of a ramp hinge <NUM> that secures one of the ramp portions <NUM> to the elongated beam <NUM>. As shown, the hinge <NUM> may extend along a substantial length of the beam <NUM>. It is also possible for a series of smaller hinges to be used instead. When the elongated beam <NUM> is in the raised position, the ramp portions 32a, 32b create an upward slope between the foundation <NUM> and the beam <NUM>, as illustrated by <FIG>. This feature can help protect the system <NUM> in the event that an overrun aircraft rolls over the system <NUM> (as well as protecting the aircraft and its occupants). As shown, the ramp portions 32a, 32b may have a truncated triangular shape. This shape can help the ramp portions 32a, 32b fit within the footprint of foundation <NUM>, whether the elongated beam <NUM> is raised or lowered. If provided, the ramps <NUM> are designed to be raised and lowered along with the system. As illustrated by <FIG>, as the elongated beam <NUM> is raised, the outer edges <NUM> of the ramps are pulled in, toward the elongated beam. This may occur via use of one or more cylindrical rollers that function to track along the base of the foundation <NUM> and roll inwardly as the ramps are raised.

Upward movement of the elongated beam <NUM> moves the ramp portions from a flat position illustrated by <FIG> to a raised position illustrated by <FIG>. The triangular shape of the outer edges of the ramp portions are designed to prevent them from lifting off of the foundation surface. One or more guards may be provided along ramp edges <NUM> to prevent debris from entering the space left between ramp edges <NUM> and the foundation edge <NUM>.

Upward movement of the elongated beam <NUM> moves the cable <NUM> and its tape connection <NUM> upward and causes the optional ramp portions <NUM> to track inwardly and raise as well. Raising of the elongated beam <NUM> and the retractable hook cable system positions the cable <NUM> properly across the runway. When the elongated beam <NUM> is lowered, the upper surface of the beam is flush with the runway surface. This moves the cable <NUM> to also be either flush or below with the runway surface.

Referring now to <FIG>, there is shown a view of the elongated beam <NUM> a lowered position. Lowering of the elongated beam <NUM> may be accomplished via lowering of the lifting/lowering mechanism <NUM>. When lowered, the ramp portions <NUM> are also flush with the runway surface.

<FIG> show one example of a relationship between elongated beam <NUM> and side restraint plates <NUM>. Side restraint plates <NUM> may be used to help secure the elongated beam <NUM> when in the raised position so that when an aircraft engages the cable, all of the loading is properly managed. <FIG> shows the elongated beam without the ramp portions <NUM> for ease of review. Side restraint plates <NUM> remain stationary with respect to the foundation <NUM>. In the examples shown, side restraint plates <NUM> have beam-facing securement portions <NUM>. The securement portions <NUM> shown may be one or more openings configured to receive one or more corresponding securement portions <NUM> associated with the elongated beam. As illustrated, the corresponding securement portions <NUM> may be a series of keys or protrusion <NUM> associated with the elongated beam <NUM>. It should be understood, however, that this configuration may be reversed, such that the securement portions <NUM> on the restraint baseplate may be teeth or protrusions that are received by corresponding securement portions that form openings associated with the elongated beam. It should also be understood that a single elongated opening may be provided that receives a single elongated protrusion. The side restraint plates may be vertically located inside of the cavity. In this configuration, the side restraint plates may be located along the side wall of the lower portion of the elongated beam <NUM>. This contact between the lower portion of the elongated beam side wall and the vertical restraint plates can resist the lateral forces.

The general goal is that the portions <NUM>, <NUM> mate or nest with respect to one another in order to secure the elongated beam <NUM> in a stable configuration. As shown, the corresponding securement portions <NUM> are formed as teeth/protrusions <NUM>. These teeth/protrusions may be associated with the elongated beam or otherwise positioned along the beam.

<FIG> illustrates the elongated beam <NUM> of <FIG> in a raised position (again, without the ramp portions <NUM> for ease of review). In use, as the elongated beam <NUM> is raised, the securement portions <NUM>, <NUM> nest or interlock with respect to one another. In a specific example shown, the openings of the side restraint plates <NUM> receive protrusions of the enclosure baseplate. In a specific example, the teeth/protrusions may be beveled along their top edge so that they may find their way into the openings even if the alignment is not exact. Once the elongated beam is raised, the cooperation between the securement portions <NUM>, <NUM> secures and anchors and the bolts the elongated beam <NUM> in place. This configuration takes the place of anchor bolts which are typically used to secure the elongated beam to a concrete foundation. <FIG> illustrate the lowered and raised configuration of the elongated beam <NUM> and how the securement portions <NUM>, <NUM> may cooperate with one another.

Other embodiments for supporting the elongated beam in place may be providing one or more weldments underneath the elongated beam that use the side of the foundation for resisting lateral loads. For example, as shown by <FIG>, it is possible to provide a baseplate <NUM> that can be welded or otherwise attached to the underside of the elongated beam <NUM>. Supporting framework <NUM> may also be provided to help guide the elongated beam <NUM> into the raised position while supporting the arrestment loads. The supporting framework <NUM> may be contained within the cavity of the concrete foundation. A side plate <NUM> may be secured within the supporting framework <NUM>. The side plate <NUM> may be steel and covered on its outside surfaces with a low friction material in order to provide a low friction material that allows the beam <NUM> to slide within the supporting frame work <NUM>.

As illustrated further by <FIG>, restraint plates may be side plates <NUM> that are vertically located inside the cavity. A frame weldment <NUM> may be secured within the concrete foundation. The supporting framework (not shown in this image) may then be positioned within the frame weldment <NUM>. In this example, the side restraint plates <NUM> may be located along the side wall of the lower portion of the elongated beam <NUM>. Contact between the lower portion of the elongated beam side wall and the vertical side plates <NUM> can help resist the lateral forces applied during an aircraft arrestment.

<FIG> shows an end view of <FIG> with the frame weldment <NUM> positioned within the foundation. Supporting framework <NUM> is then positioned within the frame weldment <NUM> Side plates <NUM> may be attached to both sides of the supporting framework <NUM>. The side plates <NUM> may have a low friction material <NUM> applied thereto. The elongated beam <NUM> then has a baseplate <NUM> secured thereto and is positioned within the supporting framework <NUM>. Other securement and movement options are possible and considered within the scope of this disclosure.

After the arrestment has taken place, there may be a manual reset of the cable if necessary. Alternatively, the control tower may issue a signal to lower the elongated beam <NUM> to the ground.

Although certain embodiments have been shown and described, it should also be understood that alternate options are possible and considered within the scope of this disclosure. For example, a further embodiment is illustrated by <FIG>. Rather than hinging the elongated beam <NUM> at the rear portion as shown, the beam may work along a side hinge <NUM>. For example, an actuator <NUM> (similar to the lifting and lowering mechanism <NUM>) may be used to provide a side force to move the elongated beam <NUM> from a lowered position within the cavity of the foundation <NUM> (as illustrated by <FIG>) to a raised battery position (as illustrated by <FIG>). A separate side securement may be implemented in order to maintain the elongated beam in the raised position. A cover <NUM> may be provided over the top of the elongated beam to protect from debris infiltration an aircraft rollover to the unit while it is retracted.

A further alternate example, which is not covered by the appended claims, raises and lowers the entire elongated beam <NUM>, so that the entire beam remains parallel to the runway surface, whether raised into a battery position or lowered into the foundation cavity. It is possible to provide an elongated beam that can be raised as a whole, rather than hinged the back. In this embodiment, the elongated beam would remain parallel to the ground. This embodiment does not have a hinge <NUM> at the rear portion, but may use any type of lifting and lowering mechanism as described herein. One example is illustrated by <FIG>. In this example, the system may be guided by a series of rods <NUM> mounted to the foundation <NUM> that ride in bearings contained on the beam plate. This embodiment can be revised to use the securement portions <NUM>, <NUM> described above. A lifting and lowering mechanism or actuator may be provided. This may be a hydraulic cylinder or any other type of actuation mechanism. Alternatively, the actuation force may be supplied by airbags <NUM> located under the elongated beam.

A further example, which is not covered by the appended claims, provides a pop-up sheave as illustrated by <FIG>. In this example, the beam may be provided within an enclosure and raised vertically on roller bearings. The intent is to raise and lower the beam within the enclosure box. This embodiment may provide vertically-oriented sheaves contained within an assembly that are separate from horizontal sheaves. During an arrestment event, the vertical sheaves would travel up into the desired position by a force supplied from below (which may either be the lifting and lowering mechanism/actuator, or airbags, or any other appropriate actuation mechanism). The sheave assembly would have guides, such as linear bearings, and/or be confined within the enclosure to ensure that it raises and lowers predictably and to provide the proper tape alignment with respect to the runway target. A top cover may also be provided to ride up and down with the sheave beam.

Claim 1:
A retractable sheave system for positioning a cable across an aircraft runway surface, comprising:
a foundation (<NUM>) positionable along sides of the aircraft runway surface, the foundation comprising a cavity therein,
a tape configured to be connected to the cable,
an elongated beam (<NUM>) that functions as a runway edge sheave configured to be positioned within the cavity, wherein the elongated beam (<NUM>) comprises at least one horizontal roller sheave and at least one vertical sheave in order to orient the tape moving through the elongated beam;
a hinge (<NUM>) associated with the elongated beam;
a lifting/lowering mechanism (<NUM>) associated with the elongated beam,
wherein when the lifting/lowering mechanism configures the elongated beam in a lowered position, the elongated beam rests within the cavity and is flush with the aircraft runway surface, and wherein when the lifting/lowering mechanism configures the elongated beam in a raised position, the elongated beam hinges with respect to the hinge such that at least a forward portion of the elongated beam raises above the runway surface,
wherein the retractable sheave system is mountable at a runway edge.