GB2247845A - Model aircraft ground rentention devices - Google Patents

Abstract

A powered model aircraft ground retention device comprises a ground stable base structure 14 mounting a retention arm structure 6 which can be moved from a locked operative position, at which at least two arms 7, 8 of the arm structure can engage the forward lateral edges of an aircraft tail structure to retain the aircraft in position on the ground, to a released position to free the aircraft. From the operative position shown, the arm structure is spring-urged about pivot 12 when a latch is released by cranked arm 18. <IMAGE>

Description

IMPROVEMENTS RELATING TO MODEL AIRCRAFT GROUND RETENTION DEVICES This invention relates to model aircraft ground retention devices.

In the case of engine-powered (e.g. propeller driven) model aircraft it is both convenient and considerably safer to provide some arrangement effective for retaining the aircraft in a stationary position on the ground both during and after starting up of the aircraft engine. Such an arrangement is more especially important from the safety aspect in the case of higher powered model aircraft (e.g.

aircraft having internal combustion engines which may have capacities of up to 100 cc) since manually holding and restraining the aircraft during and after starting up of the engine can be hazardous to the handler and the inadvertent release of the aircraft could be extremely dangerous to the handler and/or bystanders.

Hitherto, it has often been the practice to drive pegs into the ground on each side of the fuselage of an aircraft to be retained so that they engage the forward lateral edges of the aircraft tail structure. Such an arrangement, however, not only necessitates lifting the aircraft manually over the retention pegs to free the aircraft from the retention arrangement but it does not facilitate launching of the aircraft from its restrained position on the ground.

Another known aircraft retention arrangement for model aircraft comprises interconnected releasable clamps which embrace the fuselage of the aircraft at spaced locations in front of the wings and tail of the aircraft, respectively.

This arrangement requires each of the clamps to be manually released before the aircraft can then be manually lifted from the arrangement prior to launch.

According to the present invention there is provided a powered model aircraft ground retention device comprising a ground-stable base structure having attached to it a mechanism including a retention arm structure which can be moved from a locked operative position at which at least two arms of the arm structure can engage the forward lateral edges of an aircraft tail structure to retain the aircraft in position on the ground to a released position by the displacement of the arm structure so that the arms are moved to a position to free the aircraft.

According to a preferred embodiment of ground retention device the retention arm structure is pivotally mounted for movement, preferably in the forward direction of the aircraft, from the locked operative position at which the arms are sufficiently upstanding from the ground for engaging the tail structure to the released position at which the arms are located in a lower (e.g. horizontal) position in order to free the aircraft.

In carrying out the present invention the pivotally mounted arm structure may be released from the locked operative position thereof by means of a manually-operated (e.g. foot operated) lever or other suitable actuating arrangement (e.g. cranked arm) which may actuate a latching device normally effective to hold the arm structure with the arms thereof in the upstanding position.

The pivotal movement of the arm structure to its released position may be produced by means of a biassing spring arrangement which becomes effective when the mechanism is actuated but it is also envisaged that such pivotal movement could alternatively be provided by cam means operable in response to the actuation of the mechanism or such pivotal movement could be due simply to gravity.

The base structure is preferably rendered ground stable by means of base securing spikes or stakes which may, for example, comprise separate stakes preferably adapted to be driven into the ground through holes positioned in the base structure so that enlarged head sections of the stakes bear down on the base structure in order to hold it securely in position on the ground.

The base structure is preferably contoured as by the provision of an inclined plate so that when the pivotally mounted arm structure takes up its horizontal position or thereabouts after the release thereof the base structure provides a virtually unimpeded ramp surface for the forward movement of a rear wheel or skid secured to the tail end of the aircraft.

In order to protect the tail structure of the aircraft the upstanding arms of the arm structure preferably present relatively soft outer surfaces to the lateral edge of the tail structure. This may readily be accomplished by slipping a sheath of plastics foam over the arms (e.g.

metal) of the structure.

The arm structure may comprise a U shaped structure having two arms and pivotally mounted at the junction between these arms.

The mechanism for controlling the position of the retention structure may be operated remotely as by cable, radio or infra red control means.

By way of example the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of one embodiment of a powered model aircraft ground retention device according to the invention; and, Figures 2 and 3 are fragmentary side elevational diagrams of the retention arm structure locking arrangement of the device shown in Figure 1.

Referring to the drawings, the ground retention device shown for a powered (e.g. petrol, diesel ducted fan, jet or electric) aircraft comprises a base structure 1 which may be fabricated from any suitable rigid material (e.g. plywood) and which in the present embodiment is provided with holes 2 and 3 through which metal pegs or stakes, such as the stake 4, may be driven into the ground so that the enlarged turned head sections of the stakes will bear down on the upper surface of the base structure in order to hold the structure firmly in position on the ground.

The base structure 1 has attached to it a mechanism indicated generally at 5 for controlling the position of a generally U-shaped aircraft tail retention structure 6 providing two arms 7 and 8. The structure 6 may be of tubular metal and may be provided with an outer sheath (not shown) of plastics foam material to help protect an aircraft tail structure against damage. Closure end caps 9 and 10 may also be provided.

The U-shaped retention structure 6 has an open-sided metal box structure 11 secured, as by welding, to the junction between the arms 7 and 8 of the retention structure. This box structure 11 and thus the retention structure as a whole is pivotally mounted on a pivot pin 12 which extends transversely through and is held captive to a mounting bracket 13 forming part of a metal fixing plate 14 (see Figures 2 and 3) secured, as by screws, to the underside of the base structure 1.

In Figures 1 and 2 the U-shaped retention structure 6 is held by a locking arrangement so that the arms 7 and 8 are upstanding at or near the vertical. In this position of the structure 6 which is the operative locked position for ground retention of an aircraft the upstanding arms 7 and 8 will be positioned against the leading lateral edges of the tail structure (shown in dotted outline in Figure 1) of an aircraft on either side of the main body fuselage to prevent forward movement of an aircraft when the aircraft engine is started. Locking of the structure 6 in this position is accomplished by means of a latch member 15 having a pawl 16 which engages an inside wall surface of the box structure 11. The structure 6 may have a relatively small amount of pivotal free play in the locked position thereof.

The box structure 11 has one end of a coiled tension spring 17 attached to it, the other end of the spring 17 being secured to the plate 14. The spring 17 biases the pivoted retention structure in the direction "A" in Figure 1 (i.e. towards the front end of a retained aircraft).

In order to release the retention structure 6 to allow a retained aircraft to be launched a spring-loaded cranked actuating rod 18 supported by bearing blocks 19 and 20 secured to the base structure 1 is rotated in the direction indicated by the arrow "B" against the biasing spring action of coiled loading spring 21. This rotation which is readily produced by a downward foot pressure exerted on upwardly inclined projecting rod end 22 and causes the other end 23 of the rod 18 which is received by a hole in the latch member 15 to be raised and thereby lift the latch member 15 in the direction "C" in Figure 3 away from the base structure 1.In so doing the pawl 16 (Figures 2 and 3) is lifted out of engagement with the inner wall surface of the box structure 11 so that the tension spring 17 can now pull the retention structure 16 down to a substantially horizontal position thereby releasing the ground retained aircraft from the device.

In order to restore the device to its operative locked position the retention arm structure 16 is simply raised pivotally to the substantially vertical position so that the spring biased latch 15 once again makes snap engagement with the box structure 11.

In order to allow a restrained aircraft to be launched as the retention device is released an inclined flexible metal plate 24, for example, may be provided on the base structure 1 to allow an aircraft tail wheel or skid to travel over the device unimpeded. The plate 24 may be secured at its wider end to the base structure 1 and at its tapered end to the latch member 15. The flexibility of the plate 24 adds considerably to the downward biasing force exerted on the latch member 15 and the rotational biasing force exerted on rod 18 by the coil spring 27.

As will readily be appreciated from the foregoing, modifications may be made to the device in terms of the construction of various device parts, including the locking mechanism, and materials used without departing from the spirit of the invention. For example, although in the preferred embodiment described the arm structure is pivotaly mounted for pivotal movement in the forward direction of the aircraft when the arm structure is released it will be appreciated that such pivotal movement could be in the rearward direction of the aircraft, as by raising the arms of the structure over the tail structure, or the arms could be arranged to be slidably raised (or lowered) above (or below) the lateral edges of the tail structure when the arm structure is released. Moreover, although the mechanism of the device described is operated manually it will be appreciated that the mechanism could be operated remotely as by cable release, radio control or by infra-red control signals.

Claims (16)

1. A powered model aircraft ground retention device comprising a ground stable base structure having attached to it a mechanism including a retention arm structure which can be moved from a locked operative position at which at least two arms of the arm structure can engage the forward lateral edges of an aircraft tail structure to retain the aircraft in position on the ground to a released position by the displacement of the arm structure so that the arms are moved to a position in order to free the aircraft.

2. An aircraft retention device as claimed in claim 1, in which the arm structure is pivotally mounted.

3. An aircraft retention device as claimed in claim 2, in which the arm structure is pivotally mounted for movement in the forward direction of the aircraft from the locked operative position at which the arms are sufficiently upstanding from the ground for engaging the tail structure to the released position at which the arms are located in a lower (e.g. horizontal) position in order to free the aircraft.

4. An aircraft ground retention device as claimed in claim 2 or 3, in which the pivotally mounted arm structure is releasable from the locked operative position thereof by means of a manually-operated lever or other suitable actuating arrangement which actuates a latching device normally effective in the locked position to hold the arm structure with the arms thereof in the upstanding or other position to retain the aircraft.

5. An aircraft ground retention device as claimed in claim 4, in which the pivotally mounted arm structure is releasable by means of a spring-biased rotatably mounted cranked rod one end of which is received by a latching member of the latching device and the other end of which is arranged to be manually depressed, as by foot pressure.

6. An aircraft ground retention device as claimed in claim 5, in which the latching member includes a pawl which engages with a box structure to which the arm structure is secured.

7. An aircraft ground retention device as claimed in any preceding claim in which the arm structure is generally U-shaped providing two retaining arms.

8. An aircraft ground retention device as claimed in any preceding claim, in which the movement of the arm structure to its released position is produced by means of a biasing spring arrangement which becomes effective when the mechanism is actuated.

9. An aircraft ground retention device as claimed in any of claims 1 to 7, in which the movement of the arm structure is provided by cam means operable in response to the actuation of the mechanism.

10. An aircraft ground retention device as claimed in any of claims 1 to 7, in which the movement of the arm structure to its released position is caused by gravity after actuation of the mechanism.

11. An aircraft retention device as claimed in any preceding claim, in which the base structure is rendered ground stable by means of one or more spikes or stakes which can be inserted into the ground.

12. An aircraft ground retention device as claimed in claim 11, in which the spike(s) or stake(s) are separate from the base structure and are arranged to be driven into the ground through holes in the base structure and provided with relatively large head sections which bear against the base structure to hold it securely on the ground.

13. An aircraft ground retention device as claimed in any preceding claim, in which the base structure is contoured so that when the arm structure takes up its released position the base structure provides a virtually unimpeded surface for the forward movement for a wheel or skid secured to the tail end of the aircraft.

14. An aircraft ground retention device as claimed in claim 13, in which the base structure is contoured by means of an inclined/flexible plate secured at one end to the base structure and at the other end to a latching member of the mechanism to bias the latching member to an arm structure locking position.

15. An aircraft ground retention device as claimed in any preceding claim in which the arm structure is actuated by remote control (e.g. radio, infra-red or cable).

16. An aircraft ground retention device substantially as hereinbefore described with reference to the accompanying drawings.