Cross connection test for aircraft landing gear

Abstract

A method of testing an aircraft landing gear. The landing gear includes a first wheel and a second wheel; a first brake system and a second brake system; a first tachometer output line and a second tachometer output line; a first brake command line associated with the first tachometer output line; a second brake command line associated with the second tachometer output line. The method includes: generating a test signal with the first tachometer, wherein the first wheel does not rotate during generation of the test signal; receiving the test signal via one of the tachometer output lines; issuing a brake command in response to receiving the test signal, wherein the brake command is issued via the brake command line associated with the one of the tachometer output lines; and monitoring a response of the first brake system or the second brake system to the brake command to test for a cross-connection between the first brake system and the second brake system.

Description

Technical Field

[0001] The present invention relates to a method for testing an aircraft landing gear to test the cross-connection between braking systems; a method for generating test signals using a tachometer of the aircraft landing gear; and an aircraft landing gear system configured to perform these methods. Background Technology

[0002] When changes are made to the tachometers, servo valves, or pressure transducers on an aircraft landing gear braking system, testing may be required to ensure no cross-connections have occurred. This is typically done by activating the anti-skid system and using a pair of rigs to rotate the wheels at different speeds. The operator in the aircraft cockpit can then view which wheels the system deems need braking and which wheels are actually being braked.

[0003] Conventional methods face several problems. First, the landing gear must be raised from the ground to allow the wheels to rotate. Second, a pair of rigs are needed to rotate the wheels fast enough for the anti-skid system to detect the differential. Third, the method requires three operators: two on the ground and one in the cockpit. Summary of the Invention

[0004] A first aspect of the present invention provides a method for testing an aircraft landing gear, the aircraft landing gear comprising: a first wheel and a second wheel; a first braking system including a first tachometer and a first brake, the first tachometer being mounted to the first wheel and configured to generate a first tachometer signal indicating rotation of the first wheel, the first brake being configured to brake the first wheel; a second braking system including a second tachometer and a second brake, the second tachometer being mounted to the second wheel and configured to generate a second tachometer signal indicating rotation of the second wheel, the second brake being configured to brake the second wheel; a first tachometer output line and a second tachometer output line; a first brake command line associated with the first tachometer output line; and a second brake command line associated with the second tachometer output line. The method includes: a) generating a test signal using a first tachometer, wherein the first wheel does not rotate during the generation of the test signal; b) receiving the test signal via a tachometer output line in the tachometer output lines; c) issuing a braking command in response to the received test signal, wherein the braking command is issued via a braking command line associated with said tachometer output line in the tachometer output lines; and d) monitoring the response of a first braking system or a second braking system to the braking command to test the cross-connection between the first braking system and the second braking system.

[0005] The test signal can be generated by rotating a portion of the first tachometer.

[0006] The first tachometer may include a tachometer rotor and a tachometer sensor. The tachometer rotor is configured to rotate with a first wheel, and the tachometer sensor is configured to measure the rotation of the tachometer rotor to generate a first tachometer signal. The test signal can be generated by rotating the tachometer sensor of the first tachometer or by rotating the tachometer rotor of the first tachometer.

[0007] A portion of the tachometer can be rotated less than one full revolution.

[0008] A portion of the tachometer can be rotated back and forth less than one full revolution.

[0009] The response of the first or second braking system can be monitored by the person inspecting the first or second brake.

[0010] The response of the first or second braking system can be monitored by an automatic monitoring system.

[0011] Monitoring the response of the first or second braking system may include monitoring whether the first or second braking system responds to a braking command.

[0012] Monitoring the response of the first or second braking system may include monitoring whether one of the brakes has been engaged and not released.

[0013] A braking command can be issued on only one braking command line in the braking command line.

[0014] If the second braking system responds to a braking command, it can indicate a cross-connection.

[0015] Monitoring the response of the first or second braking system may include monitoring whether the first or second braking system responds to a braking command to test the cross-connection between the first and second tachometers.

[0016] Optionally, the first braking system includes a first servo valve; the second braking system includes a second servo valve; a braking command is issued to one of the servo valves; and monitoring the response of the first or second braking system includes monitoring whether the first or second braking system responds to the braking command to test the cross-connection between the first and second servo valves.

[0017] Optionally, the first braking system further includes a first pressure transducer; the second braking system further includes a second pressure transducer; monitoring the response of the first braking system or the second braking system includes monitoring whether the first pressure transducer or the second pressure transducer responds to a braking command.

[0018] Optionally, the first braking system further includes a first pressure transducer configured to measure hydraulic pressure in the first braking system to generate a pressure signal; the second braking system further includes a second pressure transducer configured to measure hydraulic pressure in the second braking system to generate a pressure signal; the aircraft landing gear further includes a first pressure transducer line associated with a first tachometer output line and a second pressure transducer line associated with a second tachometer output line; monitoring the response of the first braking system or the second braking system includes monitoring whether a pressure signal is received on the first pressure transducer line or the second pressure transducer line.

[0019] Optionally, the first braking system includes a first servo valve and a first pressure transducer; the second braking system includes a second servo valve and a second pressure transducer; and the response of the first braking system and the second braking system is monitored by testing the cross-connection between the first tachometer and the second tachometer, the cross-connection between the first servo valve and the second servo valve, and the cross-connection between the first pressure transducer and the second pressure transducer.

[0020] Another aspect of the present invention provides a method for generating a test signal using a tachometer of an aircraft landing gear, the aircraft landing gear including: a wheel; and a tachometer mounted to the wheel, wherein the tachometer includes a tachometer rotor and a tachometer sensor, the tachometer rotor being configured to rotate with the wheel, and the tachometer sensor being configured to measure the rotation of the tachometer rotor to generate a tachometer signal indicating the rotation of the wheel, the method comprising: generating a test signal by disconnecting the tachometer rotor from the wheel and then rotating the tachometer rotor without rotating the wheel.

[0021] Another aspect of the present invention provides an aircraft landing gear comprising: a wheel; and a tachometer including a tachometer rotor and a tachometer sensor, the tachometer rotor being configured to rotate with the wheel, and the tachometer sensor being configured to measure the rotation of the tachometer rotor to generate a tachometer signal indicating the rotation of the wheel, wherein the tachometer rotor is connected to the wheel via a floating connector configured to allow the tachometer rotor to rotate without rotating the wheel to generate a test signal.

[0022] A floating connection can be configured to allow the tachometer rotor to rotate more than 10° without rotating the wheel.

[0023] Another aspect of the present invention provides a method for testing and repairing aircraft landing gear, the method comprising: testing the aircraft landing gear according to the method of the first aspect to identify a cross-connection between a first braking system and a second braking system; and repairing the cross-connection between the first braking system and the second braking system in response to the identification of the cross-connection.

[0024] Another aspect of the present invention provides an aircraft landing gear system comprising: a first wheel and a second wheel; a first braking system including a first tachometer mounted to the first wheel and a first brake configured to brake the first wheel, wherein the first tachometer is configured to generate a first tachometer signal indicating rotation of the first wheel and is also configured to generate a first test signal, wherein the first wheel does not rotate during the generation of the first test signal; and a second braking system including a second tachometer mounted to the second wheel and a second brake configured to brake the second wheel, wherein the second tachometer is configured to generate a second tachometer signal indicating rotation of the second wheel and is also configured to generate a second test signal, wherein the second wheel does not rotate during the generation of the second test signal. The system does not rotate during generation; it includes a first tachometer output line and a second tachometer output line; a first brake command line associated with the first tachometer output line; a second brake command line associated with the second tachometer output line; and a brake control and monitoring system configured to: receive a first test signal or a second test signal via one of the tachometer output lines; issue a brake command in response to the received first test signal or second test signal, wherein the brake command is issued via a brake command line associated with one of the tachometer output lines; and monitor the response of the first brake system or the second brake system to the brake command to test the cross-connection between the first brake system and the second brake system.

[0025] The first tachometer may include a first tachometer rotor and a first tachometer sensor, the first tachometer rotor being configured to rotate with a first wheel; the first tachometer sensor being configured to measure the rotation of the first tachometer rotor to generate a first tachometer signal.

[0026] The second tachometer may include a second tachometer rotor and a second tachometer sensor, the second tachometer rotor being configured to rotate with a second wheel; the second tachometer sensor being configured to measure the rotation of the second tachometer rotor to generate a second tachometer signal.

[0027] The first tachometer rotor can be connected to the first wheel via a first floating connector, which allows the first tachometer rotor to rotate without rotating the first wheel to generate a first test signal. Alternatively, the tachometer sensor can be rotatable to generate a test signal, with both the first tachometer rotor and the first wheel remaining stationary during test signal generation.

[0028] The second tachometer rotor can be connected to the second wheel via a second floating connector, which allows the second tachometer rotor to rotate without rotating the second wheel to generate a second test signal. Alternatively, the tachometer sensor can be rotatable to generate a test signal, with both the second tachometer rotor and the second wheel remaining stationary during test signal generation. Attached Figure Description

[0029] Embodiments of the present invention will now be described with reference to the accompanying drawings, wherein:

[0030] Figure 1 The aircraft was shown;

[0031] Figure 2 The landing gear system is shown;

[0032] Figure 3 The landing gear wiring harness is shown;

[0033] Figure 4 The servo valve cross connection is shown;

[0034] Figure 5 The pressure transducer cross-connection is shown;

[0035] Figure 6 The tachometer cross-connection is shown;

[0036] Figure 7 The method for testing the first wheel of the landing gear is shown;

[0037] Figure 8 The method for testing the second wheel of the landing gear is shown;

[0038] Figure 9 The arrangement of the first tachometer is shown;

[0039] Figure 10 yes Figure 9 A side view of the wheel;

[0040] Figure 11 The image shows the tachometer rotor being rotated after it has been disconnected from the wheel;

[0041] Figure 12 The arrangement of the second tachometer is shown;

[0042] Figure 13 yes Figure 12 A side view of the wheel, in which the tachometer pin is disconnected from the wheel;

[0043] Figure 14 yes Figure 12 A side view of the wheel, in which the tachometer rotor rotates such that the tachometer pin engages with the wheel. Detailed Implementation

[0044] Figure 1 The aircraft 10 shown has a nose landing gear and a pair of main landing gears 11. Figure 2 The diagram shows in detail one of the main landing gears 11 and the associated braking control and monitoring system 29 of the landing gear.

[0045] The main landing gear 11 includes a first wheel 20a and a second wheel 20b, each of which has an associated braking system 21a, 21b.

[0046] The first braking system 21a includes a first tachometer 22a and a first brake 23a. The first tachometer 22a is mounted to the first wheel and configured to generate a first tachometer signal indicating the rotation of the first wheel. The first brake 23a is configured to brake the first wheel.

[0047] The second braking system 21b includes a second tachometer 22b and a second brake 23b. The second tachometer 22b is mounted to the second wheel and configured to generate a second tachometer signal indicating the rotation of the second wheel. The second brake 23b is configured to brake the second wheel.

[0048] The braking systems 21a and 21b also include a first servo valve 30a and a second servo valve 30b; a first fuse 40a and a second fuse 40b; and a first pressure transducer 50a and a second pressure transducer 50b.

[0049] The braking control and monitoring system 29 is configured to control and monitor the braking systems 21a and 21b by issuing braking commands to the braking systems 21a and 21b and monitoring the responses of the braking systems 21a and 21b, as described below.

[0050] Braking control and monitoring system 29 via Figure 2 The wiring harness 12 shown is connected to the braking system, wherein, Figure 3 The diagram shows two sets of wiring harness lines: a first set of wiring harness lines 24a, 31a, 51a, which are associated with each other (and with the first braking system 21a) by the braking control and monitoring system 29; and a second set of wiring harness lines 24b, 31b, 51b, which are associated with each other (and with the second braking system 21b) by the braking control and monitoring system 29.

[0051] The first tachometer 22a and the second tachometer 22b are connected to the first tachometer output line 24a and the second tachometer output line 24b; the first servo valve 30a and the second servo valve 30b are connected to the first brake command line 31a and the second brake command line 31b; and the first pressure transducer 50a and the second pressure transducer 50b are connected to the first pressure transducer output line 51a and the second pressure transducer output line 51b.

[0052] The first brake command line 31a, the first tachometer output line 24a, and the first pressure transducer output line 51a are interconnected; and similarly, the second brake command line 31b, the second tachometer output line 24b, and the second pressure transducer output line 51b are interconnected.

[0053] Hydraulic fluid is supplied to the first braking system and the second braking system through corresponding hydraulic lines 60a and 60b.

[0054] The first pressure transducer 40a is configured to measure the hydraulic pressure in the hydraulic line 60a to generate a pressure signal. Similarly, the second pressure transducer 40b is configured to measure the hydraulic pressure in the hydraulic line 60b to generate a pressure signal.

[0055] Figures 4 to 6 This illustrates various cross-connection errors that may occur between the first and second braking systems during the replacement of one or more components of the braking system.

[0056] If servo valves 30a and 30b are replaced, their corresponding brake command lines 31a and 31b will be disconnected, and as follows: Figure 4 The new servo valves 32a and 32b are installed in the location shown. Figure 4 This illustrates a servo valve cross-connection error where a new servo valve is connected to the wrong wiring harness. Specifically, the new servo valve 32a of the first braking system 21a is incorrectly connected to the brake command line 31b of the second braking system 21b; and the new servo valve 32b of the second braking system 21b is incorrectly connected to the brake command line 31a of the first braking system 21a.

[0057] If pressure transducers 50a and 50b are replaced, their corresponding wiring harnesses must be disconnected, and as follows: Figure 5 New pressure transducers 52a and 52b are installed in the location shown. Figure 5This illustrates a pressure transducer cross-connection error where a new pressure transducer is connected to the wrong wiring harness. Specifically, the new pressure transducer 52a of the first braking system 21a is incorrectly connected to the pressure transducer output line 51b of the second braking system 21b; and the new pressure transducer 52b of the second braking system 21b is incorrectly connected to the first pressure transducer output line 51a of the first braking system 21a.

[0058] If tachometers 22a and 22b are replaced, their corresponding wiring harnesses must be disconnected, and as follows: Figure 6 The new tachometers 25a and 25b are installed in the locations shown. Figure 6 This illustrates a tachometer cross-connection error where a new tachometer is connected to the wrong wiring harness. Specifically, the output port of the new tachometer 25a of the first braking system 21a is incorrectly connected to the second tachometer output line 24b of the second braking system 21b; and the output port of the new tachometer 25b of the second braking system 21b is incorrectly connected to the first tachometer output line 24a of the first braking system 21a.

[0059] Figure 7 The method for testing the aircraft landing gear 11 for this type of cross-connection is shown. It should be noted that... Figure 7 In the diagram, the first wheel 20a is referred to as wheel 1, and the second wheel 20b is referred to as wheel 2.

[0060] In step 69, a first test signal is generated by the first tachometer 22a. The first test signal can be referred to below. Figures 9 to 14 Detailed descriptions are generated in multiple ways.

[0061] Generally, the first tachometer 22a includes: a first portion (tachometer rotor) configured to rotate with the first wheel; and a second portion (tachometer sensor) configured to measure the rotation of the tachometer rotor to generate a first tachometer signal. The first test signal is generated by manually rotating a portion of the tachometer: this portion is the tachometer rotor or the tachometer sensor. The first wheel 20a does not rotate during the generation of the first test signal.

[0062] Therefore, the first tachometer 22a is configured not only to generate a first tachometer signal indicating the rotation of the first wheel 20a, but also to generate a first test signal. The first wheel 20a does not rotate during the generation of the first test signal.

[0063] A portion of the tachometer can be rotated back and forth, typically less than one full revolution. The test signal can be generated continuously for any time period. For example, a portion of the tachometer can be rotated back and forth for 1.5 seconds, 500 milliseconds, or 150 milliseconds.

[0064] This generates a first test signal, which is transmitted through the first tachometer output line 24a of the first braking system, or as in... Figure 6 In the event of a cross-connection error of the tachometer shown, the output of the second tachometer of the second braking system is fed to the braking control and monitoring system 29 via the second tachometer output line 24b.

[0065] The braking control and monitoring system 29 is configured to: receive a first test signal via a tachometer output line in the tachometer output line; issue a braking command in response to the received first test signal; and monitor the response of the first braking system or the second braking system to the braking command to test the cross-connection between the first braking system and the second braking system.

[0066] At step 70, the brake control and monitoring system 29 receives a first test signal via one of the tachometer output lines and issues a brake command via a brake command line. The brake control and monitoring system 29 associates this brake command line with one of the tachometer output lines (i.e., the tachometer output line that receives the first test signal). In other words, if the first test signal is received via the first tachometer output line 24a, a brake command is issued via the first brake command line 31a; and if the first test signal is received via the second tachometer output line 24b, a brake command is issued via the second brake command line 31b. It should be noted that the brake command is issued only on one of the brake command lines.

[0067] The braking system response is automatically monitored by the braking control and monitoring system 29 by monitoring whether a pressure signal is received on the first pressure transducer line or the second pressure transducer line. The response of the first or second braking system is also manually monitored by the operator on the ground by observing the operation of the brakes.

[0068] Figure 7 Four possible responses to the braking command are shown.

[0069] In the absence of a cross-connection error, since no tachometer cross-connection error has occurred, a first test signal is received at the brake control and monitoring system 29 from the first tachometer output line 24a of the first braking system. This causes a braking command to be sent to the first braking system 21a via a signal on the brake command line 31a associated with the first tachometer output line 24a. Since no servo valve cross-connection error has occurred, this will cause the servo valve 30a to open and operate the first brake 23a via the hydraulic line 60a.

[0070] The control and monitoring system 29 also receives a pressure signal from the first pressure transducer 50a via the first pressure transducer output line 51a, indicating that the pressure on the correct hydraulic line 60a has changed. When the first brake 23a is applied, the pressure increases, and the first pressure transducer 50a transmits an "increased pressure" signal to the control and monitoring system 29 via the first pressure transducer output line 51a. This serves as confirmation that the correct brake is being applied, as the "increased pressure" signal is received from the correct (first) pressure transducer output line 51a. After 10 seconds, the control and monitoring system 29 commands the first servo valve 30a to reset. This causes the pressure to drop and the first brake 23a to release. The first pressure transducer 50a transmits a "decreased pressure" signal to the control and monitoring system 29 via the first pressure transducer output line 51a. This serves as confirmation that the first brake has been released. At step 71, the control and monitoring system 29 responds to the reception of the pressure signal for "reduced pressure" by displaying "Wheel 1 test completed" on the cockpit display device in the cockpit 12.

[0071] An operator on the ground manually rotates a portion of the tachometer to observe the first brake 23a and the second brake 23b, and at step 72, the operator observes that the correct brake (i.e., the first brake 23a) has been applied for 10 seconds and then released.

[0072] The operator who has already manually rotated a portion of the tachometer on the ground and observed at step 72 that the correct brake (i.e., the first brake 23a) has been applied and released can then move to the cockpit and observe the "Wheel 1 test complete" message to verify that no cross-connection has occurred (since the operator on the ground knows that wheel 1 is the correct wheel). Alternatively, a second human operator in the cockpit can observe the cockpit display, communicating with the operator on the ground to determine which wheel is currently being tested (i.e., which tachometer was rotated by the operator on the ground) and confirm that no cross-connection has occurred.

[0073] In the case of cross-connection of tachometers, an operator who manually rotates a portion of the tachometer on the ground observes the first brake 23a and the second brake 23b, and at step 73, the operator observes that the incorrect brake (i.e., the second brake 23b) has been applied and released.

[0074] Due to a tachometer cross-connection error, a first test signal is received at the brake control and monitoring system 29 from the second tachometer output line 24b of the second braking system. This causes a braking command to be issued to the second braking system 21b via a signal on the second brake command line 31b, which the brake control and monitoring system 29 associates with the second tachometer output line 24b. Since no servo valve cross-connection error occurred, this causes the second servo valve 30b to open and operate the second brake 23b via the hydraulic line 60b.

[0075] The control and monitoring system 29 also receives a signal from the second pressure transducer 50b via the second pressure transducer output line 51b, indicating a change in pressure on the second hydraulic line 60b. When the second brake 23b is applied, the pressure increases, and the second pressure transducer 50b transmits an "increased pressure" signal to the control and monitoring system 29 via the second pressure transducer output line 51b. This serves as confirmation that an incorrect (second) brake is being applied, as the "increased pressure" signal is received from the second pressure transducer output line 51a. After 10 seconds, the control and monitoring system 29 commands the second servo valve 30b to reset. This causes the pressure to drop and the second brake 23b to release. The second pressure transducer 50b transmits a "decreased pressure" signal to the control and monitoring system 29 via the second pressure transducer output line 51b. This serves as confirmation that the second brake has been released. At step 74, the control and monitoring system 29 responds to the reception of the "reduced pressure" pressure signal by displaying "Wheel 2 test completed" on the cockpit display device in the cockpit 12.

[0076] The operator who has already manually rotated a portion of the tachometer on the ground and observed at step 73 that the incorrect brake (i.e., the second brake 23b) has been applied and released can then move to the cockpit and observe the "Wheel 2 test complete" message to determine that a tachometer cross-connection has occurred rather than a servo valve cross-connection (it should be noted that the operator on the ground knows that wheel 2 is the incorrect wheel). Alternatively, a second human operator can observe the cockpit display, communicating with the operator on the ground, to determine which wheel is currently being tested (i.e., which tachometer has been rotated by the operator on the ground) and indicate the presence of a tachometer cross-connection.

[0077] In step 75, once a tachometer cross-connection has been identified, the cross-connection is repaired by swapping the first tachometer output line 24a and the second tachometer output line 24b to connect to the first tachometer 25a and the second tachometer 25b, respectively. Therefore, repair is performed in response to the determination of a tachometer cross-connection.

[0078] In the case of cross-connection of pressure transducers, an operator on the ground manually rotates a portion of the tachometer to observe the first brake 23a and the second brake 23b, and at step 76, the operator observes that the correct brake (i.e., the first brake 23a) has been applied but not released.

[0079] Because no tachometer cross-connection error occurred, a first test signal was received from the first tachometer output line 24a of the first braking system at the brake control and monitoring system 29. This caused a braking command to be issued to the first braking system 21a via a signal on the first brake command line 31a, and the brake control and monitoring system 29 associated the first brake command line 31a with the first tachometer output line 24a. Since no servo valve cross-connection error occurred, this caused the servo valve 30a to open and operate the first brake 23a via the hydraulic line 60a.

[0080] The control and monitoring system 29 also receives pressure signals from the second pressure transducer output line 51b. When the first brake 23a is applied, the pressure increases, and the second pressure transducer transmits the "increased pressure" pressure signal to the control and monitoring system 29 via the second pressure transducer output line 51b.

[0081] The control and monitoring system 29 monitors whether the first pressure transducer or the second pressure transducer responds to the braking command. In this case, the control and monitoring system 29 expects a signal from the first pressure transducer output line 51a (because the control and monitoring system 29 associates the first pressure transducer output line 51a with the first tachometer output line 24a) but instead receives a signal from the second pressure transducer output line 51b. The absence of the expected signal from the first pressure transducer output line 51a means that the control and monitoring system 29 will not command the first servo valve 30a to reset. Instead, at step 77, the control and monitoring system 29 responds to the absence of a signal from the first pressure transducer output line 51a by displaying "Wheel 1 Pressure Failure" on the cockpit display device in the cockpit 12.

[0082] The operator who has already manually rotated a portion of the tachometer on the ground and observed at step 76 that the correct brake (i.e., the first brake 23a) has been applied but not released can then move to the cockpit and see the "Wheel 1 Pressure Failure" message to recheck for a pressure transducer cross-connection (since the operator on the ground knows that Wheel 1 is the correct wheel). Alternatively, a second human operator can observe the cockpit display, communicating with the operator on the ground to determine which wheel is currently being tested (i.e., which tachometer was rotated by the operator on the ground) and indicate that a pressure transducer cross-connection has occurred.

[0083] In step 78, once a cross-connection of the pressure transducers has been confirmed, the cross-connection is repaired by swapping the first pressure output line 51a and the second pressure output line 51b so that they are connected to the first pressure transducer 52a and the second pressure transducer 52b, respectively. Therefore, repair is performed in response to the determination of a cross-connection of the pressure transducers.

[0084] In the case of servo valve cross-connection, an operator who manually rotates a portion of the tachometer on the ground observes the response of the first brake 23a and the second brake 23b, and at step 79, the operator observes that the incorrect brake (i.e., the second brake 23b) has been applied and released.

[0085] Because no tachometer cross-connection error occurred, a first test signal was received at brake control and monitoring system 29 from the first tachometer output line 24a of the first braking system. This resulted in a braking command being issued on the first brake command line 31a, which is associated with the first tachometer output line 24a but incorrectly connected to the second braking system 21b. This caused the second servo valve 30b to open and the second brake 23b to operate via hydraulic line 60b.

[0086] The control and monitoring system 29 also receives signals from the output line 51b of the second pressure transducer. When the second brake 23b is applied, the pressure increases, and the second pressure transducer transmits the "increased pressure" signal to the control and monitoring system 29 via the second pressure transducer output line 51b.

[0087] The control and monitoring system 29 monitors whether the first pressure transducer or the second pressure transducer responds to the braking command. In this case, the control and monitoring system 29 expects a signal from the first pressure transducer output line 51a, but instead receives a signal from the second pressure transducer output line 51b. The absence of a signal from the first pressure transducer output line 51a means that the control and monitoring system 29 does not command the servo valve to reset. Instead, at step 80, the control and monitoring system 29 responds to the absence of a signal from the first pressure transducer output line 51a by displaying "Wheel 1 Pressure Failure" on the cockpit display device in the cockpit 12.

[0088] The operator who has already manually rotated a portion of the tachometer on the ground and observed at step 79 that the incorrect brake (i.e., the second brake 23b) has been applied and released can then move to the cockpit and view the "Wheel 1 Pressure Failure" message to determine that a servo valve cross-connection has occurred, rather than a tachometer cross-connection (it should be noted that the operator on the ground knows that wheel 2 is the incorrect wheel). Alternatively, a second human operator can observe the cockpit display, communicating with the operator on the ground to determine which wheel is currently being tested (i.e., which tachometer is being rotated by the operator on the ground) and identify that a servo valve cross-connection has occurred.

[0089] In step 81, once a servo valve cross-connection has been identified, the cross-connection is repaired by swapping the first brake command line 31a and the second brake command line 31b so that they are connected to the first servo valve 32a and the second servo valve 32b, respectively. Therefore, this repair is performed in response to the determination of a servo valve cross-connection.

[0090] The second tachometer 22b is identical to the first tachometer 22a. Therefore, the second tachometer 22b is configured not only to generate a second tachometer signal indicating the rotation of the second wheel 20b, but also to generate a second test signal. The second wheel 20b does not rotate during the generation of the second test signal.

[0091] Therefore, for the second wheel, the braking system response can be repeatedly monitored by rotating the rotor of the second tachometer. Figure 7 Methods, such as Figure 8 As shown in the image. It should be noted that in... Figure 8 In the diagram, the first wheel 20a is referred to as wheel 1, and the second wheel 20b is referred to as wheel 2.

[0092] The above method has several advantages over conventional methods for testing cross-connected landing gear. First, it eliminates the need to lift the landing gear to ensure the wheels are turning. Second, it eliminates the need for a pair of drills to turn the wheels. Third, the method requires only one or two operators: one operator operates the tachometer on the ground, and optionally another operator is located in the cockpit.

[0093] exist Figure 7 or Figure 8 In one implementation, the test signal is generated by rotating a portion of the tachometer. In an alternative implementation, the test signal can be generated electronically by the tachometer without rotating any part of it.

[0094] exist Figure 7 and Figure 8 In one implementation, a test signal is generated by rotating a portion of the tachometer back and forth in less than one full revolution. In other implementations, a portion of the tachometer may rotate in only one direction and / or may rotate more than one full revolution.

[0095] exist Figure 7 and Figure 8 In one embodiment, the response of the first or second braking system is manually monitored by a person observing the first or second brake, and the response of the first or second braking system is also automatically monitored by an automatic monitoring system (control and monitoring system 29) that monitors the response of the pressure transducer. This is preferred because it provides a check on the identification of cross-connections and / or helps to distinguish between tachometer cross-connections and servo valve cross-connections. In an alternative embodiment, the response of the first or second braking system may be monitored manually only or automatically only.

[0096] exist Figure 7 and Figure 8 In one implementation, the method includes: monitoring which braking system responds to a braking command, monitoring whether a brake in the brakes has been applied but not released, and monitoring which pressure transducer line responds to a braking command. Other methods of monitoring the response are conceivable.

[0097] exist Figure 7 and Figure 8In one implementation, the responses of the first and second braking systems are monitored to test three types of cross-connections: cross-connection between the first and second tachometers, cross-connection between the first and second servo valves, and cross-connection between the first and second pressure transducers. In other implementations, the method may be used to test only one or two types of cross-connections. For example, if only the tachometers are being repaired, it may only be necessary to test the tachometer cross-connections. In this case, observation by a ground operator of an incorrectly applied brake is sufficient to indicate a tachometer cross-connection.

[0098] Figure 9 and Figure 12 Two different tachometer arrangements are shown, configured to generate the test signal mentioned above, wherein the wheel does not rotate during the generation of the test signal.

[0099] Figure 9 The first arrangement of the first tachometer 22a and the second tachometer 22b is shown in detail. The two tachometers 22a and 22b are identical, and therefore both are shown in a single figure.

[0100] Each tachometer includes tachometer rotors 101a, 101b, 102a, 102b and tachometer sensors 100a, 100b. The tachometer rotors 101a, 101b, 102a, 102b are configured to rotate with wheels 20a, 20b. The tachometer sensors 100a, 100b are configured to measure the rotation of the tachometer rotors to generate a tachometer signal indicating the rotation of the wheels. In this case, the tachometer rotors are cylindrical shafts 101a, 101b with square locating pins 102a, 102b. Shafts 101a, 101b are housed within the tachometer sensors 100a, 100b, but other physical arrangements are possible. The tachometer sensors 100a, 100b can measure the rotation of shafts 101a, 101b by any suitable means, such as magnetic or optical measurement.

[0101] Wheels 20a and 20b include wheel bodies 110a and 110b and tires 111a and 111b. Wheel bodies 110a and 110b are mounted on axles 112a and 112b. Bearings between the axles and the wheels allow the wheels to rotate relative to the axles 112a and 112b. Tachometer sensors 100a and 100b do not rotate with the wheels and are housed within the axles 112a and 112b, which also do not rotate with the wheels.

[0102] The tachometer rotor is connected to the wheel bodies 110a and 110b via locking plates 115a and 115b. Square locating pins 102a and 102b are received in square openings in the locking plates 115a and 115b. The locking plates 115a and 115b are connected via… Figure 10 Bolts 113a and 113b shown are fastened to the wheel body.

[0103] The test signal is generated as follows: the tachometer rotors 101a, 101b; 102a, 102b are disconnected from the wheel, shafts 101a and 101b are grasped by hand, and then shafts 101a and 101b are manually rotated without rotating the wheel. Specifically, bolts 113a, 113b and locking plates 115a, 115b are removed to disconnect the tachometer rotor from the wheel body, allowing the tachometer rotor to rotate freely independent of the wheel.

[0104] Figure 11 The diagram shows the tachometer rotor being rotated clockwise, and also shows the bolt holes 114a, 114b of the receiving bolts 113a, 113b located in the wheel body. Tests have shown that a test signal can be generated by rotating the tachometer rotor for as short as 150 ms, but typically the tachometer rotor rotates back and forth for a longer period of time.

[0105] Figures 12 to 14 The arrangement of the second tachometer is shown. Many components are... Figures 9 to 11 The same reference numerals are used for these elements.

[0106] In this configuration, the tachometer rotor is connected to the wheel body via a floating connector configured to allow the tachometer rotor to rotate without rotating the wheel to generate a test signal. More specifically, the shafts 101a and 101b of the tachometer rotor carry pins 120a and 120b at their distal ends, and the wheel bodies 110a and 110b have, for example, […]. Figure 13 The pair of stops 121a and 121b shown are used. The tachometer rotor rotates freely until pins 120a and 120b are... Figure 14 The stops 121a and 121b engage as shown. During wheel rotation, the stops 121a and 121b remain in contact with pins 120a and 120b, thus forcing the tachometer rotor to rotate with the wheel. When the wheel is stationary, a ground-based operator can grasp pins 120a and 120b and manually rotate them back and forth to generate a test signal.

[0107] In this configuration, the floating connector is designed to allow the tachometer rotor to rotate approximately 90° without rotating the wheel. However, in other embodiments of the invention, the floating connector may only be able to achieve a smaller range of motion. Preferably, the floating connector is configured to allow the tachometer rotor to rotate more than 10°, 20°, or 30° without rotating the wheel.

[0108] When the word "or" appears, it will be interpreted as meaning "and / or", meaning that the things referred to are not necessarily mutually exclusive and can be used in any appropriate combination.

[0109] Although the invention has been described above with reference to one or more preferred embodiments, it should be understood that various changes or modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A method for testing aircraft landing gear, said aircraft landing gear comprising: First wheel and second wheel; A first braking system, comprising a first tachometer and a first brake, wherein the first tachometer is mounted to the first wheel and configured to generate a first tachometer signal indicating rotation of the first wheel, and the first brake is configured to brake the first wheel; A second braking system, comprising a second tachometer and a second brake, wherein the second tachometer is mounted to the second wheel and configured to generate a second tachometer signal indicating the rotation of the second wheel, and the second brake is configured to brake the second wheel; First tachometer output line and second tachometer output line; A first braking command line associated with the output line of the first tachometer; as well as The second braking command line associated with the output line of the second tachometer; The method includes: a. A test signal is generated using the first tachometer, wherein the first wheel does not rotate during the generation of the test signal; b. Receive the test signal via one of the tachometer output lines in the tachometer output circuit; c. In response to the received test signal, a braking command is issued, wherein the braking command is issued via a braking command line associated with one of the tachometer output lines; and d. Monitor the response of the first braking system or the second braking system to the braking command to test the cross-connection between the first braking system and the second braking system, and indicate cross-connection if the second braking system responds to the braking command.

2. The method according to claim 1, wherein, The test signal is generated by rotating a portion of the first tachometer.

3. The method according to claim 2, wherein, The portion of the first tachometer is rotated less than one full revolution.

4. The method according to claim 2 or 3, wherein, The portion of the first tachometer is rotated back and forth less than one full revolution.

5. The method according to any one of claims 1 to 3, wherein, The first tachometer includes a tachometer rotor and a tachometer sensor, the tachometer rotor being configured to rotate with the first wheel, and the tachometer sensor being configured to measure the rotation of the tachometer rotor to generate the first tachometer signal; and wherein the test signal is generated by rotating the tachometer sensor of the first tachometer or by rotating the tachometer rotor of the first tachometer.

6. The method according to any one of claims 1 to 3, wherein, The response of the first braking system or the second braking system is monitored by a person observing the first brake or the second brake.

7. The method according to any one of claims 1 to 3, wherein, The response of the first braking system or the second braking system is monitored by an automatic monitoring system.

8. The method according to any one of claims 1 to 3, wherein, Monitoring the response of the first braking system or the second braking system includes monitoring whether the first braking system or the second braking system responds to the braking command.

9. The method according to any one of claims 1 to 3, wherein, Monitoring the response of the first braking system or the second braking system includes monitoring whether one of the brakes has been applied and not released.

10. The method according to any one of claims 1 to 3, wherein, The braking command is issued on only one of the braking command lines.

11. The method according to any one of claims 1 to 3, wherein, Monitoring the response of the first braking system or the second braking system includes monitoring whether the first braking system or the second braking system responds to the braking command to test the cross-connection between the first tachometer and the second tachometer.

12. The method according to any one of claims 1 to 3, wherein, The first braking system includes a first servo valve; the second braking system includes a second servo valve; the braking command is issued to one of the servo valves; and monitoring the response of the first braking system or the second braking system includes monitoring whether the first braking system or the second braking system responds to the braking command to test the cross-connection between the first servo valve and the second servo valve.

13. The method according to any one of claims 1 to 3, wherein: The first braking system further includes a first pressure transducer configured to measure hydraulic pressure in the first braking system to generate a pressure signal; The second braking system further includes a second pressure transducer configured to measure hydraulic pressure in the second braking system to generate a pressure signal; The aircraft landing gear also includes a first pressure transducer line associated with the first tachometer output line and a second pressure transducer line associated with the second tachometer output line; and Monitoring the response of the first braking system or the second braking system includes monitoring whether a pressure signal is received on the first pressure transducer line or the second pressure transducer line.

14. The method according to any one of claims 1 to 3, wherein, The first braking system includes a first servo valve and a first pressure transducer; the second braking system includes a second servo valve and a second pressure transducer; and, monitoring the responses of the first braking system and the second braking system tested the cross-connection between the first tachometer and the second tachometer, the cross-connection between the first servo valve and the second servo valve, and the cross-connection between the first pressure transducer and the second pressure transducer.

15. A method for testing and repairing aircraft landing gear, the method comprising: The aircraft landing gear is tested using the method described in any one of claims 1 to 14 to identify cross-connections between the first braking system and the second braking system; And in response to the identification of the cross connection, repair the cross connection between the first braking system and the second braking system.

16. An aircraft landing gear, comprising: wheel; The tachometer includes a tachometer rotor and a tachometer sensor. The tachometer rotor is configured to rotate with the wheel, and the tachometer sensor is configured to measure the rotation of the tachometer rotor to generate a tachometer signal indicating the rotation of the wheel. The tachometer rotor is connected to the wheel via a floating connector configured to allow the tachometer rotor to rotate without rotating the wheel to generate a test signal. The shaft of the tachometer rotor carries a pin at its distal end. The wheel body has a pair of stops that remain in contact with the pin during wheel rotation to allow the tachometer rotor to rotate with the wheel. When the wheel is stationary, the pin can be manually rotated to generate the test signal.

17. The aircraft landing gear according to claim 16, wherein, The floating connector is configured to allow the tachometer rotor to rotate more than 10° without rotating the wheel.

18. An aircraft landing gear system, comprising: First wheel and second wheel; A first braking system includes a first tachometer mounted to the first wheel and a first brake configured to brake the first wheel, wherein the first tachometer is configured to generate a first tachometer signal indicating rotation of the first wheel and is also configured to generate a first test signal, wherein the first wheel does not rotate during the generation of the first test signal; A second braking system includes a second tachometer mounted to the second wheel and a second brake configured to brake the second wheel, wherein the second tachometer is configured to generate a second tachometer signal indicating rotation of the second wheel and is also configured to generate a second test signal, wherein the second wheel does not rotate during the generation of the second test signal; First tachometer output line and second tachometer output line; A first braking command line associated with the output line of the first tachometer; The second brake command line associated with the output line of the second tachometer; and A braking control and monitoring system configured to: receive a first test signal or a second test signal via a tachometer output line in a tachometer output line; issue a braking command in response to the received first test signal or second test signal, wherein the braking command is issued via a braking command line associated with the tachometer output line in the tachometer output line; and monitor the response of the first braking system or the second braking system to the braking command to test the cross-connection between the first braking system and the second braking system.

19. The aircraft landing gear system according to claim 18, wherein: The first tachometer includes a first tachometer rotor and a first tachometer sensor. The first tachometer rotor is configured to rotate with the first wheel. The first tachometer sensor is configured to measure the rotation of the first tachometer rotor to generate the first tachometer signal. The second tachometer includes a second tachometer rotor and a second tachometer sensor, the second tachometer rotor being configured to rotate with the second wheel; the second tachometer sensor being configured to measure the rotation of the second tachometer rotor to generate the second tachometer signal. The first tachometer rotor is connected to the first wheel via a first floating connector, which allows the first tachometer rotor to rotate without rotating the first wheel to generate the first test signal; and The second tachometer rotor is connected to the second wheel via a second floating connector, which enables the second tachometer rotor to rotate without rotating the second wheel to generate the second test signal.

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