GB2066180A - Aircraft wing spoiler system - Google Patents

Abstract

The danger of an aircraft's landing excessively heavily after a bounce is reduced by controlling the deployment of wing spoilers on touch-down such in that outboard spoilers (14) do not become fully deployed until after a second landing. The inboard spoilers (13) are deployed rapidly on initial touch-down. <IMAGE>

Description

SPECIFICATION Aircraft aerodynamic control systems The present invention relates to the aerodynamic control systems of aircraft and to their operation during landing of the aircraft.

It is currently common practice to fit spoilers on the aerodynamic lifting surfaces, particularly the wings, of aircraft. When operated these spoilers extend into air flow over the surface creating turbulence which affects the lift produced by the surfaces. Spoilers can be used in direct lift control systems and to assist (or even replace) aerodynamic controls such as aileron and elevator.

Spoilers are usually deployed automatically on touch-down, deployment being triggered by wheel spin up, oleo compression or bogie tilt. This allows a reduction in the certificated landing field length.

However, many aircraft landings involve a bounce, and the automatic deployment of the spoilers frequently results in a second landing after a bounce being undesirably heavy. When the spoilers are deployed very rapidly (so that, effectively, they are deployed by the time the aircraft leaves the ground in a bounce) the wing fundamental frequency is excited and the aircraft roll control capability reduced. When the spoilers are deployed slowly, during the time the aircraft is clear of the ground, lift which has contributed to increasing the height of the bounce is destroyed before it can cushion the descent and reduce the heaviness of the second landing. Once the spoilers are deployed their direct lift control and aerodynamic control functions are no longer available, which results in a sudden adverse change in the aircraft handling characteristics.

According to the present invention, an aircraft aerodynamic control system of the type having spoilers on the wings which are deployed on touch-down includes means for ensuring that inboard spoilers are deployed rapidly whilst outboard spoilers are deployed so that full deployment does not occur until the aircraft has made a second landing after a bounce.

If practical the inboard spoilers should be deployed rapidly enough to ensure that they are effectively fully deployed before the aircraft leaves the ground in a bounce.

The required deployment of the outboard spoilers can be arranged by a delay in the deployment sequence, by slowing down the rate of deployment, or by a combination of these.

With spoiler deployment according to the invention direct lift and aerodynamic control functions will not be lost completely during a bounce and the lift remaining to cushion a second landing after the bounce will be increased compared to that available with conventional deployment technique. As the inboard spoilers are near a displacement node of the wing fundamental frequency this frequency will not be excited by their rapid deployment, and the outboard spoilers will deploy too slowly to generate aerodynamic forces at this frequency.

An aircraft wing having spoilers which are deployed, on landing, according to the invention is illustrated in the accompanying drawing at a stage shortly prior to a second landing after a bounce of the aircraft to which the wing is attached.

Awing 10 having conventional flaps 11 and ailerons 12 has inboard spoilers such as those shown at 13 and outboard spoilers such as those shown at 14.

On touch-down of the aircraft (not shown) to which the wing is attached deployment of the spoilers 13, 14 is initiated by, for example, wheel spin up, oleo compression or bogie tilt. Deployment is such that the inboard spoilers 13 are fully deployed, as illustrated, as soon as possible, and preferably before the aircraft leaves the ground in a bounce. Deployment of the outboard spoilers 14 is such that whilst the aircraft is airborne in a bounce (as illustrated) the spoilers 14 remain closed or open only slightly as illustrated at 14a, full deployment to the position illustrated in dotted lines at 14b being delayed until the aircraft has landed for a second time after a bounce.

Deployment of the outboard spoilers 14 may be delayed relative to that of the inboard spoilers 13, the rate of deployment reduced relative to that of the inboard spoilers 13, or both.

1. An aircraft aerodynamic control system of the type having spoilers on the wings which are deployed on touch-down including means for ensuring that inboard spoilers are deployed rapidly whilst outboard spoilers are deployed so that full deployment does not occur until the aircraft has made a second landing after a bounce.

2. A control system as claimed in Claim 1 wherein the inboard spoilers are effectively fully deployed before the aircraft leaves the ground in a bounce.

3. A control system as claimed in Claim 1 or in Claim 2 wherein the deployment of the outboard spoilers is delayed with respect to deployment of the inboard spoilers.

4. A control system as claimed in any one of Claims 1 to 3 wherein the rate of deployment of the outboard spoilers is slower than that of the inboard spoilers.

5. A control system substantially as herein described with reference to the accompanying drawing.

6. An aircraft having an aerodynamic control system as claimed in any one of Claims 1 to 5.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Aircraft aerodynamic control systems The present invention relates to the aerodynamic control systems of aircraft and to their operation during landing of the aircraft. It is currently common practice to fit spoilers on the aerodynamic lifting surfaces, particularly the wings, of aircraft. When operated these spoilers extend into air flow over the surface creating turbulence which affects the lift produced by the surfaces. Spoilers can be used in direct lift control systems and to assist (or even replace) aerodynamic controls such as aileron and elevator. Spoilers are usually deployed automatically on touch-down, deployment being triggered by wheel spin up, oleo compression or bogie tilt. This allows a reduction in the certificated landing field length. However, many aircraft landings involve a bounce, and the automatic deployment of the spoilers frequently results in a second landing after a bounce being undesirably heavy. When the spoilers are deployed very rapidly (so that, effectively, they are deployed by the time the aircraft leaves the ground in a bounce) the wing fundamental frequency is excited and the aircraft roll control capability reduced. When the spoilers are deployed slowly, during the time the aircraft is clear of the ground, lift which has contributed to increasing the height of the bounce is destroyed before it can cushion the descent and reduce the heaviness of the second landing. Once the spoilers are deployed their direct lift control and aerodynamic control functions are no longer available, which results in a sudden adverse change in the aircraft handling characteristics. According to the present invention, an aircraft aerodynamic control system of the type having spoilers on the wings which are deployed on touch-down includes means for ensuring that inboard spoilers are deployed rapidly whilst outboard spoilers are deployed so that full deployment does not occur until the aircraft has made a second landing after a bounce. If practical the inboard spoilers should be deployed rapidly enough to ensure that they are effectively fully deployed before the aircraft leaves the ground in a bounce. The required deployment of the outboard spoilers can be arranged by a delay in the deployment sequence, by slowing down the rate of deployment, or by a combination of these. With spoiler deployment according to the invention direct lift and aerodynamic control functions will not be lost completely during a bounce and the lift remaining to cushion a second landing after the bounce will be increased compared to that available with conventional deployment technique. As the inboard spoilers are near a displacement node of the wing fundamental frequency this frequency will not be excited by their rapid deployment, and the outboard spoilers will deploy too slowly to generate aerodynamic forces at this frequency. An aircraft wing having spoilers which are deployed, on landing, according to the invention is illustrated in the accompanying drawing at a stage shortly prior to a second landing after a bounce of the aircraft to which the wing is attached. Awing 10 having conventional flaps 11 and ailerons 12 has inboard spoilers such as those shown at 13 and outboard spoilers such as those shown at 14. On touch-down of the aircraft (not shown) to which the wing is attached deployment of the spoilers 13, 14 is initiated by, for example, wheel spin up, oleo compression or bogie tilt. Deployment is such that the inboard spoilers 13 are fully deployed, as illustrated, as soon as possible, and preferably before the aircraft leaves the ground in a bounce. Deployment of the outboard spoilers 14 is such that whilst the aircraft is airborne in a bounce (as illustrated) the spoilers 14 remain closed or open only slightly as illustrated at 14a, full deployment to the position illustrated in dotted lines at 14b being delayed until the aircraft has landed for a second time after a bounce. Deployment of the outboard spoilers 14 may be delayed relative to that of the inboard spoilers 13, the rate of deployment reduced relative to that of the inboard spoilers 13, or both. CLAIMS

1. An aircraft aerodynamic control system of the type having spoilers on the wings which are deployed on touch-down including means for ensuring that inboard spoilers are deployed rapidly whilst outboard spoilers are deployed so that full deployment does not occur until the aircraft has made a second landing after a bounce.

2. A control system as claimed in Claim 1 wherein the inboard spoilers are effectively fully deployed before the aircraft leaves the ground in a bounce.

3. A control system as claimed in Claim 1 or in Claim 2 wherein the deployment of the outboard spoilers is delayed with respect to deployment of the inboard spoilers.

4. A control system as claimed in any one of Claims 1 to 3 wherein the rate of deployment of the outboard spoilers is slower than that of the inboard spoilers.

5. A control system substantially as herein described with reference to the accompanying drawing.

6. An aircraft having an aerodynamic control system as claimed in any one of Claims 1 to 5.