Hydraulic thrust reverser actuation system

Abstract

A hydraulic thrust reverser system (TRAS) including a first return line having a first check valve therein, and a second return line having a second check valve therein, wherein the first return line and the second return line are in fluid communication with each other via a fluid restrictor located upstream of the first and second check valves, wherein the first return line extends from a piston system of the TRAS, the piston system being for moving at least one thrust reverser door, and wherein the second return line extends from a lock system of the TRAS, the lock system being for controlling locks to selectively prevent the movement of the at least one thrust reverser door.

Claims

1. A hydraulic thrust reverser system (TRAS) including: a first return line having a first check valve therein; and a second return line having a second check valve therein; wherein the first return line and the second return line are in fluid communication with each other via a fluid restrictor located upstream of the first and second check valves; wherein the first return line extends from a piston system of the TRAS, the piston system being for moving at least one thrust reverser door; and wherein the second return line extends from a lock system of the TRAS, the lock system being for controlling locks to selectively prevent the movement of the at least one thrust reverser door.

2. The TRAS of claim 1, wherein the fluid restrictor is a fluid line having a bore therethrough for transmitting fluid between the first and second return lines, wherein at least a portion of a length of said bore has a smaller diameter than: a minimum diameter of a bore through the first return line; and/or a minimum diameter of a bore through the second return line.

3. The TRAS of claim 1, wherein the first return line and the second return line are additionally in fluid communication downstream of the first and second return line check valves.

4. The TRAS of claim 3, wherein the first return line and the second return line converge to an outlet.

5. The TRAS of claim 1, configured so that, in use, the first return line is at a first return line pressure and the second return line is at a second return line pressure, and the first and second return line pressures are greater than ambient pressure.

6. The TRAS of claim 1, wherein the TRAS includes a supply of hydraulic fluid at a supply pressure, and an isolation control valve, wherein the isolation control valve is configured to selectively isolate the supply pressure from both the piston system and the lock system of the TRAS.

7. The TRAS of claim 1, further comprising: a restrictor line for allowing fluid to flow between the first and second return lines, wherein a first end of the restrictor line is interconnected with the first return line at a location between ends of the first return line, and a second end of the restrictor line is interconnected with the second return line at a location between ends of the second return line, and wherein the restrictor is located in the restrictor line.

8. The TRAS of claim 1, wherein said at least one thrust reverser door controlled by the piston system, and wherein said one lock system is configured to control a lock to selectively prevent the movement of the at least one thrust reverser door.

9. An aircraft including the TRAS of claim 8, wherein the aircraft further comprises: an engine and a nacelle, wherein the at least one thrust reverser door forms a section of the nacelle.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Various embodiments will now be described, by way of example only, and with reference to the accompanying drawings in which:

(2) FIG. 1 shows a prior art thrust reverser actuation system; and

(3) FIG. 2 shows an embodiment of a thrust reverser actuation system in accordance with the present invention.

DETAILED DESCRIPTION

(4) A hydraulic thrust reverser actuator system (TRAS) reverses airflow across the nacelle of an aircraft to aid braking. It is utilised when an aircraft has landed, i.e. on the ground. As a safety feature, such systems lock whilst the aircraft is in flight, i.e. such that they cannot accidentally be deployed.

(5) FIG. 1 shows a prior art TRAS 100.

(6) Inlet 102 supplies pressurised hydraulic fluid to the TRAS. Outlet 104 allows hydraulic fluid to exit the TRAS.

(7) The TRAS 100 may include an Isolation Control Valve (ICV) 108, which may be controlled by an ICV enable solenoid 106, for isolating at least a portion of the TRAS from the pressurised hydraulic fluid supplied by the inlet 102. The TRAS 100 may also include a direction control valve (DCV) 120, which may be controlled by a DCV enable solenoid 118, for controlling whether or not the thrust is reversed.

(8) The ICV 108 may be biased in one direction by an actuator 110a and in the opposing direction by a biasing spring 110b. The actuator 110a may be in selective communication with the inlet 102 via the ICV enable solenoid 106. The actuator and the biasing spring may be configured such that when the actuator 110a is in fluid communication with the inlet 102, the actuator 110a overpowers the biasing spring 110b, enabling the ICV to move as described below.

(9) The ICV enable solenoid 106 can be in a first position or a second position. The position of the ICV enable solenoid 106 may be controlled by a current through the solenoid being switched on or switched off. The ICV enable solenoid 106 may be in the first position when the current is switched on and the second position when the current is switched off, or vice versa. In the first position, as shown in FIG. 1, the ICV enable solenoid 106 prevents the pressurised fluid from being in fluid communication with the actuator 110a of the ICV 108. This results in the ICV 108 being in a closed position. In the second position, the ICV enable solenoid 106 allows the pressurised fluid to be in fluid communication with the actuator 110a of the ICV 108, resulting in the ICV being moved to an open position (not shown). Alternatively, the solenoid may be configured in the opposite direction, i.e. such that when the ICV enable solenoid is in the first position, the ICV 108 is in the open position. In either arrangement, the solenoid may be biased in one direction, such as by a spring 116, to ensure it returns to the opposite position when the current is turned off. As the actuator 110a retracts, fluid drains to the outlet 104.

(10) A manual inhibit switch 114 is a safety measure to allow a user to manually close the ICV, preventing the TRAS from operating. The manual inhibit switch may send a signal to an engine controller (not shown) that the TRAS cannot be used.

(11) During quiescent periods (i.e. periods of inactivity or dormancy), the ICV Enable solenoid 106 may be in the first position, controlling the ICV 108 to be in a closed position, as shown in FIG. 1. However, leakage may occur across the ICV 108. This may be natural leakage through the valve, or due to clearances, as the valve may not be a zero leak valve. Any such leakage through the ICV 108 will flow to the outlet 104.

(12) During periods of operation, the ICV enable solenoid 106 may be in the second position, which controls the ICV 108 to be in an open position (not shown). In this position of the ICV 108, the pressurised hydraulic fluid from the inlet is in fluid communication with the rest of the TRAS.

(13) A pressure transducer 112 may monitor the pressure of the hydraulic fluid from the inlet 102 when the ICV 108 is in an open position.

(14) The direction control valve (DCV) enable solenoid 118 may control the direction control valve (DCV) 120 in the same manner as the ICV enable solenoid 106 controls the ICV 108, and be biased in one direction by a spring. The DCV enable solenoid 118 may be controlled by the engine controller.

(15) In the embodiment of FIG. 1, the engine thrust airflow is reversed by the rotation of two doors, upper door 122a and lower door 122b. The upper and lower doors 122a and 122b are rotated by the actuation of upper and lower door actuators 126a, 126b.

(16) Primary locks 128a, 128b prevent the doors from inadvertently deploying, such as due to numerous failures in the system. The primary locks 128a,b are controlled by a primary lock controller 132, which controls primary lock actuators 130a,b. The primary lock controller 132 responds to electrical commands from the engine controller. The primary lock actuators 130a,b may biased towards locked positions by biasing springs 136a,b. This ensures that, in the event of loss of hydraulic pressure, the primary locks 128a,b close. Primary lock controller 132 may comprise a valve 134. When the valve 134 is open (and the ICV 108 is open), the hydraulic pressure (from the inlet 102) may overcome biasing springs 136a, 136b in the primary lock actuators 130a,b to release the primary locks 128a,b. The positions of the primary locks 128a,b may be monitored by proximity switches, which may send electrical signals to an engine controller.

(17) As a further safety precaution, the upper and lower door actuators 126a, 126b each comprise an actuator lock 138a, 138b to prevent inadvertent deployment of the upper and lower doors in the event of loss of functionality of the primary locks 128a, 128b. The upper and lower actuator locks 138a, 138b may comprise pistons 140a,b biased towards a locked position by a biasing spring. When hydraulic pressure is applied to the head sides of the pistons 140a,b of the door actuators 126a,b, as will be discussed below, this may also provide hydraulic pressure to overcome the biasing springs of the actuator locks 138a,b to release the actuator locks. The positions of the actuator locks 138a,b may be monitored by proximity switches, which may send electrical signals to an engine controller.

(18) When the DCV 120 is in a door closed position, pressurised hydraulic fluid from the inlet 102 is provided to the piston side of the pistons 140a,b.

(19) When the DCV 120 is in a door open position, pressurised hydraulic fluid from the inlet 102 is provided to both the head side and the piston side of the pistons 140a,b. However, the pistons 140a,b are biased such that the pistons 140a,b will move to deploy the doors 122a,122b.

(20) In operation, when the system is not in use (i.e. during quiescent times), the ICV 108 may be de-energised, such that the ICV 108 is in a closed position. The DCV 120 may also be de-energised, such that the DCV 120 is in a door closed position. In the door closed position, the thrust is not reversed. The primary lock controller 132 may also be de-energised, such that the primary lock valve 134 is in a closed position (i.e. the primary locks are on).

(21) Energisation of the ICV (i.e. the ICV is moved to the open position) pressurises the upper and lower door actuators 126a,126b to be fully retracted (i.e. the pistons 140a,b are moved to the position where the upper and lower doors are fully closed). In this position, the upper and lower doors 122a,b may not be loading on the primary locks 128a,b, in preparation for the release thereof. The primary lock controller 132 is also pressurised. Thus, when the primary lock controller 132 is energised, and primary lock valve 134 is opened, the primary lock actuators 130a,b cause the primary locks 128a,b to unlock. Once the proximity switches monitoring the primary locks 128a,b signal that they are unlocked, the engine controller energises the DCV 120. Both sides of the pistons 140a,b are pressurised, causing the actuator locks 138a,b to release, and the pistons 140a,b to move, opening the upper and lower doors 122a,b to the thrust reverse position.

(22) On completion of the engine reverse thrust operation, the engine controller de-energises the DCV 120, causing the pistons 126a,b to retract, and the upper and lower doors 122a,b to close. The actuator locks 138a,b lock. Once the proximity switches monitoring the actuator locks 138a,b signal that they are locked, the engine controller de-energises the primary lock controller 132, resulting in the primary locks 130a,b locking (as the hydraulic pressure is overcome by the biasing springs 136a,b). Once the proximity switches monitoring the primary locks 128a,b signal that they are locked, the engine controller de-energises the ICV 108. The pressure of the entire system can reduce to nominally zero (or ambient pressure) via the outlet 104. The upper and lower door actuators 126a,b can “relax”, as the upper and lower doors 122a,b load the primary locks 128a,b and, in case of failure, the actuator locks 138a,b.

(23) The system includes two return flow lines 144a, 144b. These flow lines allow for hydraulic fluid from the various components to return to the outlet 104. The outlet 104 includes a check valve 142, to ensure fluid only flows out of the outlet 104. The check valve 142 may be position directly at the outlet 104, or on a single flow line extending upstream thereof. If this check valve 142 fails during operation (for example by becoming blocked), this can cause problems, but can be detected by the system not functioning as expected. However, if the check valve fails during quiescent times, the leakage through the ICV 108 could cause the pressure in the TRAS to increase to the hydraulic pressure supplied by the inlet 102. This can damage the system, and cause accidental deployment of the thrust reversers, i.e. accidental movement of the upper and lower doors 122a,b.

(24) FIG. 2 shows an embodiment of the present invention that is substantially the same as the system shown in FIG. 1, except that the outlet return lines 144a, 144b each include a check valve 142a,b. Downstream from the check valves 142a, 142b, the return lines 144a,144b both extend to the outlet 104. Upstream from the check valves 142a,b (i.e. on the opposite side to the outlet 104), the return lines 144a,144b are in fluid communication via a flow restrictor 146. The flow restrictor 140 is located on a restrictor line 148, which interconnects with both the first and second return lines 144a, 144b at T junctions in an intermediate portion of each respective return line 144a, 144b (i.e. the interconnections are between first and second ends of the respective return lines). The flow restrictor 146 may be any suitable flow restrictor 146. For example, the flow restrictor may be a cartridge restrictor, an orifice plate restrictor, a calibrated restrictor, a high flow restrictor, or a low flow restrictor. The restrictor may comprise a narrower passage than that of each of the flow lines 144a,b. In use, when both check valves 142a,b, are fully functioning, there will be little fluid flow through the restrictor because most of the flow will flow along the non-restricted flow path through the respective check valve 142a,b to the outlet 104. However, if either check valve 142a,b fails, fluid in the respective return line 144a,b can flow to the outlet 104 via the flow restrictor 146 and the opposite check valve 142a,b. During operation of the TRAS 100, this will prevent a catastrophic build-up of pressure in the return line having the failed check valve. However, due to the restriction on the flow, the respective system will function more slowly, as the fluid will only be able to flow from the system to the outlet at a reduced rate, due to the restriction on the flow by the flow restrictor. For example, if the fluid in question is flowing from one side of a piston, the flow will occur more slowly, thus causing the piston to move at a slower rate than usual. Therefore, this is a detectable failure, i.e. a user or operator would be aware of the failure of the check valve. A control system and/or an operator may monitor the time taken for the at least one thrust reverser door to stow, i.e. to return to its position prior to its being deployed to divert the air from the engine. When the at least one thrust reverser door returns to a stowed or undeployed position, a sensor may send a signal to the operator to signal this. The total time taken may be the time from a command being sent to stow the at least one thrust reverser door to the time the signal is received by the control system/operator. The time taken may then be compared to the expected time for such an operation to take place (i.e. from command to signal). Should the time taken be significantly greater than the expected time, this is indicative of the first check valve having failed. A similar system may be in place for the lock system, the second check valve, and the second return line.

(25) During quiescent times, this will ensure that the system does not over pressurise if a check valve fails.