GB2344325A

GB2344325A - Aircraft undercarriage deployment with an airbag

Info

Publication number: GB2344325A
Application number: GB9826320A
Authority: GB
Inventors: Paul Buckland
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-12-02
Filing date: 1998-12-02
Publication date: 2000-06-07
Also published as: GB9826320D0

Abstract

An aircraft has an undercarriage assembly 16,18,20 movable between a retracted position (dashed lines) in a bay 12 in the body 10 of the aircraft and an operative position (solid lines) in which the undercarriage assembly 16,18,20 projects from the body 10 of the aircraft. In order to deal with the problem of the undercarriage assembly 16,18,20 not moving properly to its locked-down position when the aircraft is about to land, an airbag 24 is mounted in the bay 12 and is arranged so that, upon inflation, the airbag 24 bears on the undercarriage assembly 16,18,20 to urge it towards its operative position. The gas for inflation may be stored in a gas bottle, released by an electrically operated valve, and may be nitrogen. The undercarriage may pivot about a longitudinal axis (fig 2).

Description

Retractable Aircraft Undercarriage Assemblies and Methods of Operation thereof DESCRIPTION This invention relates to aircraft undercarriage assemblies and to methods of operation thereof.

It is common to provide aircraft with retractable undercarriage assemblies, that is assemblies which are movable between a retracted position in a bay in the body of the aircraft and an operative position in which the undercarriage assembly projects from the body of the aircraft. (In this specification,"body"includes the fuselage, wing or other part of the aircraft.) In normal flight, the undercarriage assembly is retracted into the bay so as to reduce the drag coefficient of the aircraft and to protect the undercarriage assembly from the elements. Commonly, one or more doors are provided which at least partly close the bay when the undercarriage assembly is retracted so as to provide further drag coefficient reduction and further protection from the elements.

Typically, the undercarriage assembly is retracted hydraulically, under control from the aircraft's cockpit, after a down-lock mechanism has been released, and is locked in its"up"position by an up-lock mechanism. In order to lower the undercarriage assembly, the doors of the undercarriage bay, if not attached to the undercarriage assembly, are opened. Then, the up-lock mechanism is released, under control from the cockpit (with both electrical and mechanical release mechanisms often being provided), and the undercarriage assembly is lowered by gravity, with hydraulic dampers damping its movement, until it reaches its operative position and the down-lock mechanism engages. Conventionally, indicators are provided in the aircraft's cockpit and are connected to sensors on the undercarriage assembly so as to indicate whether the undercarriage assembly is locked up, locked down, or neither.

If the undercarriage assembly does not move to and lock in its operative position, the aircrew typically have no option other than to repeat the actuation of the up-lock mechanism or to"shake"the aircraft. If that fails to lower the undercarriage assembly, then a"crash landing"must be made, which can have disastrous consequences, including loss of life and impact and stress damage to the aircraft. Such failures are very rare, but can be caused, for example, by (a) a fault in the uplock mechanism, (b) a hydraulic lock in the retraction mechanism, (c) a door being fouled or jammed in its aperture in the undercarriage bay, (d) the undercarriage assembly or door having become entangled with something in the bay during retraction, or (e) sealant, paint, glue or ice preventing the door from opening.

The present invention is concerned with these problems.

In accordance with a first aspect of the present invention, an airbag is mounted in the undercarriage bay, for example mounted to the roof of the bay, and is arranged so that, upon inflation, the airbag bears on the undercarriage assembly to urge it towards its operative position. Accordingly, if the undercarriage assembly fails to reach its locked-down position, the airbag can be deployed so as to try to force the undercarriage assembly down. The use of an airbag, rather than mechanisms, linkages, hydraulic rams or the like for a similar purpose, provides the advantages of simple construction, simple installation (whether as original equipment or as a retrofit), relatively low cost, no requirement to modify existing tried, tested and certified equipment, and the possibility of using identical designs for different models of aircraft.

(In this specification, the term"airbag"is intended to encompass airbags whether they are filled with air or some other gas when deployed. Indeed, a preferred gas is nitrogen.) Preferably, the airbag is arranged to bear upon a tyre and/or wheel of the undercarriage assembly, and/or a portion of a leg of the undercarriage assembly adjacent the tyre or wheel. In most cases, this will provide the maximum mechanical advantage to free the jamming of the undercarriage assembly. Also, by applying the airbag against the tyre, the risk of the airbag being pierced during deployment is likely to be reduced.

A gas bottle is preferably provided which is connected to the airbag via a valve which may be remotely-operable from the cockpit and/or automatically-operable, for example if a predetermined time has elapsed after an attempt has been made to lower the undercarriage assembly without the locked-down indication being given.

The invention is preferably applied to each undercarriage assembly of the aircraft.

In accordance with a second aspect of the present invention, there is provided an airbag and a mounting means therefor for use in an aircraft according to the first aspect of the invention.

In accordance with a third aspect of the present invention, there is provided a method of operation of an aircraft undercarriage assembly which is movable between a retracted position in a bay in the body of the aircraft and an operative position in which the undercarriage assembly projects from the body of the aircraft, the method comprising the step, in the case where the undercarriage assembly does not move normally between its retracted and operative positions, of inflating an airbag in the bay so that the airbag bears on the undercarriage assembly to urge it towards its operative position.

Two specific embodiments of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a transversely-pivotal undercarriage assembly: and Figure 2 is a schematic front view of a longitudinally-pivotal undercarriage assembly.

Referring to both of the figures, an aircraft body 10 is formed with an undercarriage bay 12 having doors 14. A main leg 16 of an undercarriage assembly is mounted at one end to the body 10 about a pivot 18 for movement between an operative position (shown in continuous line) and a retracted position (as shown by dashed line).

At least one tyred wheel 20 is mounted on the other end of the main leg 16. The undercarriage assembly further includes a retraction mechanism, down-lock mechanism and up-lock mechanism designated generally by reference numeral 22. In the case of Figure 1, the pivot 18 has an axis extending transversely of the aircraft, and the main leg 16 pivots upwardly and forwardly from its operative position to its retracted position.

By contrast, in the case of Figure 2, the pivot 18 has an axis extending longitudinally of the aircraft, and the main leg 16 pivots upwardly and transversely inwardly from its operative position to its retracted position. The arrangements as described so far with reference to the drawings are conventional.

An airbag 24 is mounted to the roof of the undercarriage bay 12 and is shown in its deflated condition as a solid black area, and in its deployed condition as a hatched area. In the case of Figure 1, the airbag 24 is situated, in its deflated condition, immediately above the uppermost peripheral portion of the tyre on the wheel 20 when in its retracted position. In the case of Figure 2, the airbag 24 is situated, in its deflated condition, immediately above the uppermost face of the tyre and the wheel 20 when in its retracted position. When the airbag 24 is deployed, it pushes the undercarriage assembly downwardly to its operative position in which the down-lock mechanism can engage.

The airbag 24 is positioned so that it will not be pierced by split pins, wire locking and other sharp objects when it is deployed. The airbag 24 is preferably inflated by a small compressed nitrogen bottle, similar to those used for inflating aircraft escape slides, via an electrically-operated valve controlled from the cockpit; however, other existing pressure sources on the aircraft could alternatively be used. The inflated size of the airbag 24 and the inflation pressure are chosen in dependence on the size and weight of the undercarriage assembly and the amount of space in the bay 12 to be filled. The airbag 24 is made from material having high tensile strength, low weight, and which is fireproof, waterproof, rotproof and able to be folded into a compact package.

The reader is directed to the existing art concerning collision airbags in the automotive field.

It should be noted that the description with reference to the drawings has been given purely by way of example and that many modifications and developments may be made to the embodiments of the invention.

Claims

1. An aircraft having an undercarriage assembly movable between a retracted position in a bay in the body of the aircraft and an operative position in which the undercarriage assembly projects from the body of the aircraft, an airbag being mounted in the bay and being arranged so that, upon inflation, the airbag bears on the undercarriage assembly to urge it towards its operative position.

2. An aircraft as claimed in claim 1, wherein the airbag is mounted to a roof of the bay.

3. An aircraft as claimed in claim 1 or 2, wherein the airbag is arranged to bear upon a tyre and/or wheel of the undercarriage assembly, and/or a portion of a leg of the undercarriage assembly adjacent the tyre or wheel.

4. An aircraft as claimed in any preceding claim, further including a gas bottle connected via a remotely-operable, or automatically-operable, valve to the airbag.

5. An aircraft as claimed in any preceding claim and having a plurality of such undercarriage assemblies, bays and airbags.

6. An aircraft substantially as described with reference to the drawings.

7. An airbag and a mounting means therefor for use in an aircraft as claimed in any preceding claim.

8. An airbag and a mounting means therefor, substantially as described with reference to the drawings.

9. A method of operation of an aircraft undercarriage assembly which is movable between a retracted position in a bay in the body of the aircraft and an operative position in which the undercarriage assembly projects from the body of the aircraft, the method comprising the step, in the case where the undercarriage assembly does not move normally between its retracted and operative positions, of inflating an airbag in the bay so that the airbag bears on the undercarriage assembly to urge it towards its operative position.

10. A method of operation of an aircraft undercarriage assembly, substantially as described with reference to the drawings.