US20050040286A1 - Methods and systems for controlling wheel brakes on aircraft and other vehicles - Google Patents
Methods and systems for controlling wheel brakes on aircraft and other vehicles Download PDFInfo
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- US20050040286A1 US20050040286A1 US10/641,461 US64146103A US2005040286A1 US 20050040286 A1 US20050040286 A1 US 20050040286A1 US 64146103 A US64146103 A US 64146103A US 2005040286 A1 US2005040286 A1 US 2005040286A1
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- wheel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/17—Using electrical or electronic regulation means to control braking
- B60T8/1701—Braking or traction control means specially adapted for particular types of vehicles
- B60T8/1703—Braking or traction control means specially adapted for particular types of vehicles for aircrafts
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
- B60T8/321—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration deceleration
- B60T8/325—Systems specially adapted for aircraft
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C25/00—Alighting gear
- B64C25/32—Alighting gear characterised by elements which contact the ground or similar surface
- B64C25/42—Arrangement or adaptation of brakes
- B64C25/44—Actuating mechanisms
- B64C25/46—Brake regulators for preventing skidding or aircraft somersaulting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T2210/00—Detection or estimation of road or environment conditions; Detection or estimation of road shapes
- B60T2210/10—Detection or estimation of road conditions
- B60T2210/13—Aquaplaning, hydroplaning
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T2270/00—Further aspects of brake control systems not otherwise provided for
- B60T2270/40—Failsafe aspects of brake control systems
- B60T2270/416—Wheel speed sensor failure
Abstract
Methods and systems for controlling wheel brakes on aircraft and other vehicles. In one embodiment, a method for slowing a vehicle on the ground can include applying a first brake to a first wheel and a second brake to a second wheel. The method can further include determining if a first speed sensor associated with the first wheel and a second speed sensor associated with the second wheel are operative. When the first and second speed sensors are operative, the first and second brakes can be controlled according to a first routine. Conversely, when at least one of the first and second speed sensors is inoperative, the first and second brakes can be controlled according to a second routine.
Description
- The following disclosure relates generally to wheel brake systems and, more particularly, to wheel brake systems for aircraft and other vehicles.
- Conventional jet transport aircraft typically include landing gears with anti-skid or anti-lock brake systems. One such brake system is illustrated in
FIG. 1 , which shows a schematic top view of an aircraft mainlanding gear system 100 configured in accordance with the prior art. The prior artlanding gear system 100 includes a left orfirst wheel truck 102 a and a right orsecond wheel truck 102 b. On a typical aircraft, thefirst wheel truck 102 a can extend downwardly from a left wing (not shown), and thesecond wheel truck 102 b can extend downwardly from an opposite right wing (also not shown). Thefirst wheel truck 102 a can include four landing wheels 104 (shown as afirst landing wheel 104 a, asecond landing wheel 104 b, afifth landing wheel 104 e, and asixth landing wheel 104 f). Similarly, thesecond wheel truck 102 b can also include four landing wheels 104 (shown as athird landing wheel 104 c, afourth landing wheel 104 d, aseventh landing wheel 104 g, and aneighth landing wheel 104 h). Each wheel truck 102 can further include four wheel brakes 106 (shown as brakes 106 a-h) and four wheel speed sensors 108 (shown as speed sensors 108 a-h) operatively associated with the wheels 104 in one-to-one correspondence. - The
landing gear system 100 can further include awheel brake controller 110 and four processors 112 (shown as processors 112 a-d). Thecontroller 110 can be configured to receivebrake control inputs from a pilot (not shown) and send corresponding control signals to the brakes 106. Each of the processors 112 can be associated with a pair of the wheels 104. For example, thefirst processor 112 a can be operatively connected to the speed sensors 108 of thefirst wheel 104 a and thefifth wheel 104 e. Similarly, thesecond processor 112 b can be operatively connected to thesecond wheel 104 b and thesixth wheel 104 f. While four separate processors 112 are depicted inFIG. 1 for purposes of illustration, in practice two or more of the processors 112 may be combined into a single processor that provides the same function as the two or more processors. Thelanding gear system 100 can additionally include an inertial reference unit 114 (“IRU 114”) configured to provide aircraft speed information to the processors 112. - In operation, the pilot initiates a brake control input from the cockpit of the aircraft. The
controller 110 receives this control input, and in response sends a corresponding control signal to one or more of the brakes 106. Although asingle controller 110 is shown inFIG. 1 for purposes of illustration, in some brake systems each wheel may have a dedicated controller, or conversely, the controller may be omitted and each brake may receive the control input directly from the pilot. The control input from the pilot may be an electrical signal, or it may be transmitted by actuator cable to a corresponding hydraulic valve associated with the brake 106. The brakes 106 are applied to the wheels 104 in response to the signals from thecontroller 110 to slow the aircraft in accordance with the pilot's control input. - Each of the processors 112 can perform routines configured to prevent the wheels 104 from locking up or skidding undesirably when the pilot applies the brakes 106. These routines can include an individual wheel anti-skid routine, a locked-wheel protection routine, and a hydroplane/touchdown protection routine. The individual wheel anti-skid routine can prevent a wheel from skidding due to overly rapid deceleration. As the
brake 106 a, for example, is applied to thefirst wheel 104 a, thespeed sensor 108 a measures wheel speed and transmits this information to thefirst processor 112 a. Thefirst processor 112 a monitors the deceleration of thefirst wheel 104 a, and compares this deceleration to a maximum allowable deceleration. This maximum allowable deceleration can equate to a threshold above which thefirst wheel 104 a would likely lock up and skid. If the deceleration of thefirst wheel 104 a exceeds the maximum allowable deceleration, then thefirst processor 112 a transmits a signal to thebrake 106 a causing thebrake 106 a to momentarily release. This release allows thewheel 104 a to momentarily rotate freely, thus preventing wheel skid. - The locked-wheel protection routine can prevent wheel skid by preventing gross disparity between wheel speeds in a group of wheels. Referring to the
first wheel 104 a and thefifth wheel 104 e for purposes of illustration, as the brakes 106 are being applied, the speed sensors 108 transmit wheel speed information to thefirst processor 112 a. Thefirst processor 112 a compares the speed of thefirst wheel 104 a to the speed of thefifth wheel 104 e. If one of the wheel speeds is less than the other wheel speed by a preset amount or more, then thefirst processor 112 a transmits a signal to the brake 106 of the slower wheel 104, causing that particular brake 106 to momentarily release. This momentary release allows the slower wheel 104 to come up to speed and prevents the slower wheel 104 from going into a deep skid during heavy braking. - The hydroplane/touchdown protection routine applies to the aft wheels 104 (i.e., the
fifth wheel 104 e, thesixth wheel 104 f, theseventh wheel 104 g, and theeighth wheel 104 h) to prevent sustained hydroplane-induced wheel lockups during landing. This protection is applied only to the aft wheels 104 because these wheels touch down first during a typical landing. In this routine, the IRU 114 determines a first speed based on the speed of the aircraft and transmits this information to, for example, thefirst processor 112 a. Thefirst processor 112 a determines a second speed based on the speed of thefifth wheel 104 e as measured by thespeed sensor 108 e. Thefirst processor 112 a then compares the first speed from the IRU 114 to the second speed from thespeed sensor 108 e. If the second speed is less than the first speed by a preset amount or more, then thefirst processor 112 a transmits a signal to thebrake 106 e causing thebrake 106 e to momentarily release. In this manner, the hydroplane/touchdown routine pr vents thebrake 106 e from being applied to thefifth wheel 104 e until thefifth wheel 104 e is rotating at a speed commensurate with the aircraft speed, thus preventing wheel skid. - The present invention is directed generally toward methods and systems for controlling wheel brakes on aircraft and other vehicles. A method for slowing a vehicle on the ground in accordance with one aspect of the invention can be used with a vehicle having a wheel for supporting a portion of the vehicle on the ground. The vehicle can further have a brake and a speed sensor associated with the wheel. The method can include receiving a control input to slow the vehicle, and determining if the speed sensor is operative. When the speed sensor is operative, the method can further include controlling the brake according to a first routine in response to receiving the control input. Conversely, when the speed sensor is inoperative, the method can further include controlling the brake according to a second, different routine in response to receiving the control input.
- Another method for slowing a vehicle on the ground in accordance with one aspect of the invention can be used with a vehicle having at least first and second wheels for supporting a portion of the vehicle on the ground. The vehicle can further have a first brake and a first speed sensor operatively associated with the first wheel, and a second brake and a second speed sensor operatively associated with the second wheel. The method can include receiving a first control input to slow the vehicle, and applying the first brake to the first wheel and the second brake to the second wheel in response to receiving the first control input. The method can further include determining if the first and second speed sensors are operative. When the first and second speed sensors are operative, a first speed of the first wheel can be compared to a second speed of the second wheel to determine if the speeds differ by a preset amount. If the first sp ed differs from the second speed by the preset amount, the application of at least one of the first and second brakes can be changed. Conversely, when at least one of the first and second speed sensors is inoperative, the method can include continuing to apply the first brake to the first wheel and the second brake to the second wheel while receiving the first control input.
- In another aspect of the invention, changing the application of at least one of the first and second brakes when the first and second speed sensors are operative can include releasing at least one of the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount. For example, in one embodiment, the first brake can be released if the speed of the first wheel is slower than the speed of the second wheel by the preset amount. In a further aspect of the invention, continuing to apply the first brake to the first wheel and the second brake to the second wheel when at least one of the first and second speed sensors is inoperative can include continuing to apply the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount.
- An aircraft system configured in accordance with one aspect of the invention can include a first landing wheel configured to support at least a portion of an aircraft on the ground, and at least a second landing wheel configured to support at least a portion of the aircraft on the ground. The aircraft system can further include a first brake and a first speed sensor associated with the first wheel, a second brake and a second speed sensor associated with the second wheel, and a processor operatively coupled to the first and second brakes and the first and second speed sensors. The processor can be configured to respond to a first control input by applying the first brake to the first wheel and the second brake to the second wheel to slow the aircraft. The processor can be further configured to determine if the first and second speed sensors are operative and, when the first and second speed sensors are operative, determine if a first speed of the first wheel differs from a second speed of the second wheel by a preset amount. If the first speed differs from the second speed by the preset amount, the processor can change the application of at least one of the first and second brakes. Conversely, when at least one of the first and second speed sensors is inoperative, the processor can be configured to continue applying the first brake to the first wheel and the second brake to the second wheel while receiving the first control input.
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FIG. 1 is a schematic top view of an aircraft main landing gear system configured in accordance with the prior art. -
FIG. 2 is a schematic top view of an aircraft main landing gear system configured in accordance with an embodiment of the invention. -
FIG. 3 is a flow diagram illustrating a routine for bypassing locked-wheel protection in accordance with an embodiment of the invention. -
FIG. 4 is a flow diagram illustrating a routine for bypassing hydroplane/touchdown protection in accordance with an embodiment of the invention. -
FIG. 5 is a flow diagram illustrating a routine for implementing individual wheel anti-skid protection in accordance with an embodiment of the invention. -
FIG. 6 is a schematic top view of an aircraft main landing gear system configured in accordance with another embodiment of the invention. -
FIG. 7 is a flow diagram illustrating a routine for bypassing locked-wheel protection in accordance with a further embodiment of the invention. - The following disclosure describes wheel brake systems for aircraft and other vehicles, and associated methods for using such systems to slow vehicles. Certain specific details are set forth in the following description and in
FIGS. 2-7 to provide a thorough understanding of various embodiments of the invention. Other details describing well-known structures and systems often associated with aircraft and aircraft landing gear brake systems are not set forth in the following description to avoid unnecessarily obscuring the description of the various embodiments of the invention. - Many of the details, dimensions, angles, and other specifications shown in the Figures are merely illustrative of particular embodiments of the invention. Accordingly, other embodiments can have other details, dimensions, and specifications without departing from the spirit or scope of the present invention. In addition, other embodiments of the invention may be practiced without several of the details described below.
- In the Figures, identical reference numbers identify identical or at least generally similar elements. To facilitate the discussion of any particular element, the most significant digit or digits of any reference number refer to the Figure in which that element is first introduced. For example,
element 210 is first introduced and discussed with reference toFIG. 2 . -
FIG. 2 is a schematic top view of an aircraft mainlanding gear system 200 configured in accordance with an embodiment of the invention. In one aspect of this embodiment, thelanding gear system 200 includes afirst wheel truck 202 a and asecond wheel truck 202 b. Thefirst wheel truck 202 a can include four landing wheels 204 (shown as afirst landing wheel 204 a, asecond landing wheel 204 b, afifth landing wheel 204 e, and asixth landing wheel 204 f). Similarly, thesecond wheel truck 202 b can also include four landing wheels 204 (shown as athird landing wheel 204 c, afourth landing wheel 204 d, aseventh landing wheel 204 g, and aneighth landing wheel 204 h). Each wheel truck 202 can further include four wheel brakes 206 (shown as brakes 206 a-h) and four wheel speed sensors 208 (shown as speed sensors 208 a-h) operatively associated with the wheels 204 in one-to-one correspondence. In other embodiments, thelanding gear system 200 can include more or fewer wheel trucks 202 and/or more or fewer landing wheels 204. For example, in one embodiment described in detail below, a landing gear system configured in accordance with an embodiment of the invention can include a wheel truck having six landing wheels. Accordingly, aspects of the invention are not limited to the particular landing gear configuration illustrated inFIG. 2 . Further, aspects of the invention are also not limited to aircraft. For example, in another embodiment, a brake system configured in accordance with aspects of the invention can be used with an automobile. - In another aspect of this embodiment, the
landing gear system 200 further includes awheel brake controller 210, an inertial reference unit (IRU) 214, and four processors 212 (shown as afirst processor 212 a, asecond processor 212 b, athird processor 212 c, and afourth processor 212 d). Thecontroller 210, theIRU 214, and the processors 212 can be at least generally similar in structure and function to their counterparts described above with reference toFIG. 1 . Accordingly, thecontroller 210 receives brake control inputs from a pilot (not shown) and sends corresponding control signals to one or more of the brakes 206. The brakes 206 are applied to the wheels 204 in response to the control signals. In addition, the processors 212 can implement individual anti-skid routines, locked-wheel protection routines, and hydroplane/touchdown protection routines as described above in response to the information received from the speed sensors 208 and/or theIRU 214. - In a further aspect of this embodiment, the
landing gear system 200 additionally includes four bypass components 216 (shown as afirst bypass component 216 a, asecond bypass component 216 b, athird bypass component 216 c, and afourth bypass component 216 d). Each of the bypass components 216 can operatively associated with one of the processors 212 in one-to-one correspondence. (In other embodiments, one or more of the bypass components 216 can be operatively associated with more than one of the processors 212, thus allowing one or more of the bypass components 216 to be omitted). As described in greater detail below, the bypass components 216 can be configured to cause the processors 212 to bypass one or more of the wheel anti-skid/anti-lock routines described above if one of the speed sensors 208 is determined to be inoperative. One advantage of this feature is that one of the brakes 206 will not be released on the basis of an erroneous indication (e.g., from the inoperative speed sensor 208) that the corresponding wheel 204 has stopped rotating. - The
landing gear system 200 ofFIG. 2 includes asingl controller 110 and four processors 112 for purposes of illustration only. Accordingly, in other embodiments, thecontroller 210 may be omitted, and pilot control inputs may go directly from the cockpit to the brakes 206 (or to brake actuators) as either electrical or mechanical control inputs or signals. Further, in other embodiments, the functions of two or more of the processors 212, or two or more of the bypass components 216, may be combined into a single processor or bypass component, depending on the particular situation. -
FIG. 3 is a flow diagram illustrating a routine 300 for bypassing locked-wheel protection in accordance with an embodiment of the invention. For purposes of illustration, the routine 300 is described below with reference to thelanding gear system 200 ofFIG. 2 . In other embodiments, the routine 300 can be implemented by other brake systems for other vehicles, including land-based vehicles such as automobiles and trucks. Inblock 302, the routine 300 receives a control input to apply the brakes 206 to the wheels 204. Inblock 304, the routine 300 applies the brakes 206 in response to the control input. Referring to thefirst wheel 204 a and thefifth wheel 204 e as a grouped wheel pair for purposes of illustration, indecision block 306, the routine 300 determines if thefirst speed sensor 208 a is operative. If thefirst speed sensor 208 a is inoperative, then the routine 300 bypasses locked-wheel protection for the grouped wheel pair and proceeds to decision block 308 to determine if a control input has been received to release the brakes 206. If no such control input has been received, then the routine 300 returns to block 304 and continues to apply the brakes 206. Conversely, if a control input to release the brakes 206 has been received, then inblock 309 the routine 300 releases the brakes 206 and the routine 300 is complete. - Returning to decision block 306, if the
first speed sensor 208 a is operative, then the routine 300 proceeds to decision block 310 to determine if thefifth speed sensor 208 e is also operative. If thefifth speed sensor 208 e is inoperative, then the routine 300 bypasses locked-wheel protection for the grouped wheel pair and proceeds to decision block 308 as described above. Conversely, if both thefirst speed sensor 208 a and thefifth speed sensor 208 e are operative, then the routine 300 implements locked-wheel protection for the grouped wheel pair by proceeding todecision block 312. - In
decision block 312, the routine 300 determines if the difference in speed between thefirst wheel 204 a and thefifth wheel 204 e exceeds a preset amount X. In one embodiment, the preset amount X can correspond to a difference in speed that would result in skidding of the slower wheel. For example, in one embodiment, such a difference in speed can be equivalent to about 30% of the speed of the faster wheel. In other embodiments, the difference in speed for a particular application may include other values. If the difference in speed between thefirst wheel 204 a and thefifth wheel 204 e is not greater than the preset amount X, then the routine 300 proceeds to decision block 308 and continues as described above. Conversely, if the difference in wheel speeds is greater than the preset amount X, then the routine 300 proceeds to decision block 314 and determines which of the twowheels first wheel 204 a is the slower wheel, then inblock 316 the routine 300 releases thefirst brake 206 a so that thefirst wheel 204 a can come up to speed and not skid. Conversely, if thefifth wheel 204 e is the slower wheel, then inblock 318 the routine 300 releases thefifth brake 206 e so that thefifth wheel 204 e can come up to speed. After releasing the brake 206 on the slower wheel 204, the routine 300 returns to decision block 312 to again determine if the difference in wheel speeds exceeds the preset amount X. - When the difference in wheel speeds no longer exceeds the preset amount X, the routine 300 proceeds to decision block 308 as explained above. In
decision block 308, if no control input has been received to release the brakes 206, then the routine 300 proceeds to block 304 and applies the brakes 206. Conversely, if a control input to release the brakes 206 has been received, then inblock 309 the routine 300 releases the brakes 206 and the routine is complete - One feature of aspects of the embodiment described above with reference to
FIG. 3 is that if one or both of thefirst speed sensor 208 a or thefifth speed sensor 208 e is inoperative, then thefirst processor 212 a will not erroneously release the corresponding brake 206. One advantage of this feature is that the corresponding wheel 204 will have braking capability even if the associated speed sensor 208 is inoperative. -
FIG. 4 is a flow diagram illustrating a routine 400 for bypassing hydroplane/touchdown protection in accordance with an embodiment of the invention. For purposes of illustration, the routine 400 is described below with reference to thelanding gear system 200 ofFIG. 2 . In other embodiments, the routine 400 can be implemented by other brake systems for other vehicles. Inblock 402, the routine 400 receives a control input to apply the brakes 206 to the wheels 204. Inblock 404, the routine 400 applies the brakes 206 in response to the control input. Referring to an aft landing gear wheel, such as thefifth wheel 204 e, for purposes of illustration, indecision block 406, the routine 400 determines if thefifth speed sensor 208 e is operative. If thefifth speed sensor 208 e is inoperative, then the routine 400 bypasses hydroplane/touchdown protection for thefifth wheel 204 e and proceeds to decision block 408 to determine if a control input has been received to release the brakes 206. If no such control input has been received, then the routine 400 returns to block 404 and continues to apply the brakes 206. Conversely, if a control input to release the brakes 206 has been received, then inblock 409 the routine 400 releases the brakes 206 and the routine 400 is complete. - Returning to decision block 406, if the
fifth speed sensor 208 e is operative, then the routine 400 proceeds to decision block 410 to determine if a first speed as determined by theIRU 214 exceeds a second speed as determined by thefifth speed sensor 208 e by a preset amount Y. In one embodiment, the preset amount Y can represent a difference in speed between the aircraft and thefifth wheel 204 e of such magnitude that thefifth wheel 204 e is likely to hydroplane or skid upon touchdown. For example, in one embodiment, the difference in speed can be equivalent to about 50 knots. In other embodiments, the difference in speed can have other values depending on such factors as aircraft configuration. If the first speed does not exceed the second speed by the preset amount Y, then the routine 400 proceeds to decision block 408 and continues as described above. Conversely, if the first speed does exceed the second speed by the preset amount Y or more, then the routine 400 proceeds to block 412 and releases thefifth brake 206 e allowing thefifth wheel 204 e to come up to speed at touchdown before thefifth brake 206 e is applied, thereby preventing skidding or hydroplaning of thefifth wheel 204 e at touchdown. - After releasing the
fifth brake 206 e, the routine 400 returns to decision block 410 to verify that thefifth wheel 204 e is now moving at a speed commensurate with the aircraft. If the two speeds are commensurate such that the first speed does not exceed the second speed by at least the preset amount Y, then the routine 400 returns to decision block 408 to determine if a command to release the brakes has been received. If no such command has been received, then the routine 400 returns to block 404 and applies thefifth brake 206 e to thefifth wheel 204 e. Conversely, if a control input to release the brakes 206 has been received, then inblock 409 the routine 400 releases the brakes 206 and the routine 400 is complete. - One feature of aspects of the embodiment described above with reference to
FIG. 4 is that if thefifth speed sensor 208 e is inoperative, then thefirst processor 212 a will not erroneously release thefifth brake 206 e in accordance with the hydroplane/touchdown routine. One advantage of this feature is that the correspondingaft wheel 204 e will have braking capability at touchdown even if the associatedspeed sensor 208 e is inoperative. -
FIG. 5 is a flow diagram illustrating a routine 500 for implementing individual wheel anti-skid protection in accordance with an embodiment of the invention. For purposes of illustration, the routine 500 is described below with reference to thelanding gear system 200 ofFIG. 2 . In other embodiments, the routine 500 can be implemented by other brake systems for other vehicles, including land-based vehicles such as automobiles and trucks. Inblock 502, the routine 500 receives a control input to apply the brakes 206 to the wheels 204. Inblock 504, the routine 500 applies the brakes 206 in response to the control input. Referring to thefirst wheel 204 a for purposes of illustration, indecision block 506, the routine 500 determines if thefirst speed sensor 208 a is operative. If thefirst speed sensor 208 a is operative, then the routine 500 proceeds to decision block 510 to determine if the deceleration of thefirst wheel 204 a (i.e., the change in wheel speed divided by the change in time) is greater than a preset amount Z. In one embodiment, the preset amount Z can be a deceleration that represents a maximum allowable deceleration before wheel skid for the particular aircraft configuration is likely to occur. If the deceleration of thefirst wheel 204 a exceeds the preset amount Z, then the routine 500 proceeds to block 512 and releases thefirst brake 206 a so that thefirst wheel 204 a can come up to speed before thefirst brake 206 a is applied. - After releasing the
first brake 206 a, the routine 500 returns to decision block 510 to again check the deceleration of thefirst wheel 204 a. If the deceleration of thefirst wheel 204 a does not exceed the preset amount Z, then the routine 500 proceeds to decision block 508 to determine if a command to release the brakes 206 has been received. If no such command has been received, then the routine 500 returns to block 504 and applies thefirst brake 206 a. Conversely, if a command to release the brakes 206 has been received, then the routine 500 proceeds to block 509 and releases the brakes 206 and the routine 500 is complete. - Returning to decision block 506, if the
first speed sensor 208 a is inoperative, then indecision block 507, the routine 500 determines if thefifth speed sensor 208 e is operative. If thefifth speed sensor 208 e is inoperative, then the routine 500 proceeds to decision block 508 and continues as described above. Conversely, if thefifth speed sensor 208 e is operative, then indecision block 514 the routine 500 determines if the deceleration of thefifth wheel 204 e is greater than the preset amount Z. If the deceleration of thefifth wheel 204 e exceeds the preset amount Z, then the routine 500 proceeds to block 516 and releases thefirst brake 206 a. In this manner, the routine 500 is providing anti-skid protection for thefirst wheel 204 a even though thefirst speed sensor 208 a is inoperative. This protection is provided by utilizing wheel speed information from thefifth wheel 204 e to determine whether to release thefirst brake 206 a of thefirst wheel 204 a. (Although not the focus of this particular discussion, in another aspect of this embodiment, thefifth brake 206 e can also be released if the deceleration of thefifth wheel 204 e is found to exceed the preset amount Z). Returning to decision block 514, if, conversely, the deceleration of thefifth wheel 204 e does not exceed the preset amount Z, then the routine proceeds to decision block 508 and continues as described above. - One feature of aspects of the embodiment described above with reference to
FIG. 5 is that if thefirst speed sensor 208 a is inoperative, then the routine 500 can utilize wheel speed information from thefifth speed sensor 208 e to prevent skidding of thefirst wheel 204 a. One advantage of this feature is that thefirst wheel 204 a can have braking capability even if the associatedspeed sensor 208 a is inoperative. Although the foregoing description has referred to thefirst wheel 204 a and thefifth wheel 204 e for purposes of illustration, in other embodiments, other wheel groups and/or wheel combinations can be used in accordance with the present invention to provide the secondary anti-skid protection described above. -
FIG. 6 is a schematic top view of an aircraft main landing gear system 600 configured in accordance with another embodiment of the invention. In one aspect of this embodiment, the landing gear system 600 includes afirst wheel truck 602 a and asecond wheel truck 602 b. The wheel trucks 602 can be at least generally similar in structure and function to the wheel trucks 202 described above with reference toFIG. 2 . In another aspect of this embodiment, however, each of the wheel trucks 602 includes six landing wheels (shown as landing wheels 604 a-l) having associated wheel brakes 606 (brakes 606 a-l) and associated wheel speed sensors 608 (speed sensors 608 a-l). In a further aspect of this embodiment, the landing gear system 600 also includes awheel brake controller 610, anIRU 614, and four processors 612 (shown as processors 612 a-d). Thecontroller 610, theIRU 614, and the processors 612 can be at least generally similar in structure and function to their counterparts described above with reference toFIG. 2 . - In yet another aspect of this embodiment, the landing gear system 600 additionally includes four bypass components 616 (shown as bypass components 616 a-d). Each of the bypass components 616 is operatively associated with one of the processors 612 in one-to-one correspondence. Each of the processors 612 is in turn operatively associated with a separate wheel group. For example, the first processor 612 a is operatively associated with the
first wheel 604 a, thefifth wheel 604 e, and theninth wheel 604 i. As described in greater detail below, the bypass components 616 can be configured to cause the processors 612 to bypass one or more of the wheel anti-skid/anti-lock routines described above if one of the associated speed sensors 608 is determined to be inoperative. One advantage of this feature is that one of the brakes 606 will not be released based on an erroneous indication from the inoperative speed sensor 608 that the corresponding wheel 604 has stopped rotating. -
FIG. 7 is a flow diagram illustrating a routine 700 for bypassing locked-wheel protection in accordance with a further embodiment of the invention. For purposes of illustration, the routine 700 is described below with reference to the landing gear system 600 ofFIG. 6 . In other embodiments, the routine 700 can be implemented by other brake systems for other vehicles having wheel groups with three or more wheels. Inblock 702, the routine 700 receives a control input to apply the brakes 606 to the wheels 604. Inblock 704, the routine 700 applies the brakes 606 in response to the control input. Referring to thefirst wheel 604 a, thefifth wheel 604 e, and theninth wheel 604 i for purposes of illustration, indecision block 706, the routine 700 determines if thefirst speed sensor 608 a, thefifth speed sensor 608 e, and theninth speed sensor 608 i are operative. If all of these speed sensors are operative, then indecision block 710 the routine 700 implements a locked-wheel protection routine by determining if the average speed of thefifth wheel 604 e and theninth wheel 604 i exceeds the speed of thefirst wheel 604 a by a preset amount X. - If the average speed of the
fifth wheel 604 e and theninth wheel 604 i exceeds the speed of thefirst wheel 604 a by the preset amount X, then inblock 712, the routine 700 releases thefirst brake 606 a so that thefirst wheel 604 a can come up to speed with the other two wheels in the group. Conversely, if the average speed of thefifth wheel 604 e and theninth wheel 604 i does not exceed the speed of thefirst wheel 604 a by the preset amount X, then indecision block 714 the routine 700 determines if the average speed of thefirst wheel 604 a and theninth wheel 604 i exceeds the speed of thefifth wheel 604 e by the preset amount X. If so, then inblock 716 the routine 700 releases thefifth brake 606 e. Conversely, if the average speed of thefirst wheel 604 a and theninth wheel 604 i does not exceed the speed of thefifth wheel 604 e by the preset amount X, then the routine proceeds to decision block 718 to determine if the average speed of thefirst wheel 604 a and thefifth wheel 604 e exceeds the speed of theninth wheel 604 i by the preset amount X. If so, then inblock 720 the routine 700 releases theninth brake 606 i. Conversely, if the average speed of thefirst wheel 604 a and thefifth wheel 604 e does not exceed the speed of theninth wheel 604 i by the preset amount X, then the routine 700 proceeds to thedecision block 708 to determine if a command to release the brakes 606 has been received. If no such command has been received, then the routine 700 returns to block 704 and continues to apply the brakes 606. Conversely, if such a command has been received, then inblock 709 the routine 700 releases the brakes 606 and the routine 700 is complete. - Returning to decision block 706, if at least one of the
speed sensors first speed sensor 608 a and thefifth speed sensor 608 e are operative. If these two speed sensors are operative, then the routine 700 can perform the routine 300 described above with reference toFIG. 3 for thefirst wheel 604 a and thefifth wheel 604 e. Conversely, if at least one of thefirst speed sensor 208 a and thefifth speed sensor 208 e is inoperative, then the routine 700 proceeds to decision block 724 to determine if thefirst speed sensor 208 a and the ninth speed sensor 208 i are operative. - If both the
first speed sensor 208 a and the ninth speed sensor 208 i are operative, then the routine 700 can perform the routine 300 ofFIG. 3 for thefirst wheel 604 a and theninth wheel 604 i. Conversely, if at least one of thefirst speed sensors 608 a and theninth speed sensor 608 i is inoperative, then the routine 700 proceeds to decision block 726 to determine if both thefifth speed sensor 608 e and theninth speed sensor 608 i are operative. If both of these speed sensors are operative, then the routine 700 can perform the routine 300 ofFIG. 3 for thefifth wheel 604 e and theninth wheel 604 i. Conversely, if at least one of thefifth speed sensor 608 e and theninth speed sensor 608 i is inoperative, then the routine 700 proceeds to decision block 708 to determine if a command to release the brakes 606 has been received. If no such command has been received, then the routine 700 returns to block 704 and continues applying the brakes 606. Conversely, if a command to release the brakes 606 has been received, then inblock 709 the routine 700 releases the brakes 606 and the routine 700 is complete. - From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit or scope of the invention. Accordingly, the invention is not limited, except as by the appended claims.
Claims (44)
1. A method for slowing a vehicle on the ground, the vehicle having at least first and second wheels for supporting at least a portion of the vehicle on the ground, the vehicle further having a first brake and a first speed sensor associated with the first wheel, and a second brake and a second speed sensor associated with the second wheel, the method comprising:
receiving a first control input to slow the vehicle;
in response to receiving the first control input, applying the first brake to the first wheel and the second brake to the second wheel;
determining if the first and second speed sensors are operative;
when the first and second speed sensors are operative,
determining if a first speed of the first wheel differs from a second speed of the second wheel by a preset amount; and
if the first speed differs from the second speed by the preset amount, changing the application of at least one of the first and second brakes;
when at least one of the first and second speed sensors is inoperative, continuing to apply the first brake to the first wheel and the second brake to the second wheel while receiving the first control input.
2. The method of claim 1 wherein changing the application of at least one of the first and second brakes includes releasing at least one of the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount.
3. The method of claim 1 wherein:
when the first and second speed sensors are operative, changing the application of at least one of the first and second brakes includes releasing at least one of the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount; and
when at least one of the first and second speed sensors is inoperative, continuing to apply the first brake to the first wheel and the second brake to the second wheel includes continuing to apply the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount.
4. The method of claim 1 wherein changing the application of at least one of the first and second brakes includes releasing the first brake if the speed of the first wheel is slower than the speed of the second wheel by the preset amount.
5. The method of claim 1 wherein changing the application of at least one of the first and second brakes includes:
releasing the first brake if the speed of the first wheel is slower than the speed of the second wheel by the preset amount; and
releasing the second brake if the speed of the second wheel is slower than the speed of the first wheel by the preset amount.
6. The method of claim 1 wherein the first speed sensor includes a first electrical generator driven by the first wheel, and wherein determining if the first and second speed sensors are operative includes determining if the first generator is outputting an electrical signal.
7. The method of claim 1 wherein the vehicle is an aircraft having at least a first wheel truck and a second wheel truck, and wherein applying the first brake to the first wheel and the second brake to the second wheel includes applying the first and second brakes on the first wheel truck.
8. The method of claim 1 wherein the vehicle is an aircraft having at least a first wheel truck and a second wheel truck, and wherein applying the first brake to the first wheel and the second brake to the second wheel includes applying the first and second brakes to tandem wheels on the first wheel truck.
9. The method of claim 1 wherein the vehicle is an aircraft having at least a first wheel truck and a second wheel truck, and wherein applying the first brake to the first wheel and the second brake to the second wheel includes applying the first and second brakes to side-by-side wheels on the first wheel truck.
10. The method of claim 1 , further comprising:
receiving a second control input to allow the vehicle to roll free; and
in response to receiving the second control input, releasing the first brake from the first wheel and the second brake from the second wheel.
11. A method for slowing a vehicle on the ground, the vehicle having a wheel for supporting a portion of the vehicle on the ground, the vehicle further having a brake and a speed sensor associated with the wheel, the method comprising:
receiving a control input to slow the vehicle;
in response to receiving the control input, applying the brake to the wheel;
determining if the speed sensor is operative;
when the speed sensor is operative,
determining if a first speed of the wheel differs from a second speed associated with the speed of the vehicle by a preset amount, the first speed being determined with the speed sensor; and
if the first speed differs from the second speed by the preset amount, changing the application of the brake;
when the speed sensor is inoperative, continuing to apply the brake to the wheel while receiving the control input.
12. The method of claim 11 wherein changing the application of the brake includes releasing the brake if the first speed differs from the second speed by the preset amount.
13. The method of claim 11 wherein changing the application of the brake includes releasing the brake if the first speed is slower than the second speed by the preset amount.
14. The method of claim 11 wherein:
when the speed sensor is operative, changing the application of the brake includes releasing the brake if the first speed is slower than the second speed by the preset amount; and
when the speed sensor is inoperative, continuing to apply the brake to the wheel includes continuing to apply the brake if the first speed is slower than the second speed by the preset amount.
15. The method of claim 11 wherein the vehicle further includes a speed measurement device separate from the speed sensor for measuring vehicle speed, and further comprising determining the second speed of the vehicle with the speed measurement device.
16. The method of claim 11 wherein the first speed is a first wheel speed and the second speed is a second wheel speed, and further comprising:
determining a vehicle speed with an inertial reference unit; and
converting the vehicle speed to the second wheel speed.
17. The method of claim 11 wherein the control input is a first control input, and further comprising:
receiving a second control input to allow the vehicle to roll free; and
in response to receiving the second control input, releasing the brake from the wheel.
18. A method for slowing a vehicle on the ground, the vehicle having at least first and second wheels for supporting at least a portion of the vehicle on the ground, the vehicle further having a first brake and a first speed sensor associated with the first wheel, and a second brake and a second speed sensor associated with the second wheel, the method comprising:
receiving a control input to slow the vehicle;
in response to receiving the control input, applying the first brake to the first wheel and the second brake to the second wheel;
determining if the first speed sensor is operative;
when the first speed sensor is operative,
determining if a rate-of-change of speed of the first wheel exceeds a preset rate-of-change of speed, the rate-of-change of speed of the first wheel being determined with the first speed sensor; and
if the rate-of-change of speed of the first wheel exceeds the preset rate-of-change of speed, changing the application of at least the first brake;
when the first speed sensor is inoperative, determining if the second speed sensor is operative;
when the second speed sensor is operative, determining if a rate-of-change of speed of the second wheel exceeds the preset rate-of-change of speed; and
if the rate-of-change of speed of the second wheel exceeds the preset rate-of-change of speed, changing the application of at least the first brake.
19. The method of claim 18 wherein:
when the first speed sensor is operative, changing the application of at least the first brake includes releasing the first brake if the rate-of-change of speed of the first wheel exceeds the preset rate-of-change of speed; and
when the first speed sensor is inoperative, changing the application of at least the first brake includes releasing the first brake if the rate-of-change of speed of the second wheel exceeds the preset rate-of-change of speed.
20. The method of claim 18 wherein:
when the first speed sensor is operative, changing the application of at least the first brake includes releasing the first brake if a deceleration of the first wheel exceeds the preset rate-of-change of speed; and
when the first speed sensor is inoperative, changing the application of at least the first brake includes releasing the first brake if a deceleration of the second wheel exceeds the preset rate-of-change of speed.
21. A method for slowing a vehicle on the ground, the vehicle having at least first, second, and third wheels for supporting at least a portion of the vehicle on the ground, the vehicle further having a first brake and a first speed sensor associated with the first wheel, a second brake and a second speed sensor associated with the second wheel, and a third brake and a third speed sensor associated with the third wheel, the method comprising:
receiving a control input to slow the vehicle;
in response to receiving the control input, applying the first brake to the first wheel, the second brake to the second wheel, and the third brake to the third wheel;
determining if the first, second, and third speed sensors are operative;
when the first, second, and third speed sensors are operative,
determining if a first speed of the first wheel differs from an average speed of the second and third wheels by a preset amount; and
if the first speed differs from the average speed by the preset amount, changing the application of at least the first brake;
when at least the first speed sensor is inoperative, continuing to apply the first brake to the first wheel while receiving the first control input.
22. The method of claim 21 wherein when the first, second, and third speed sensors are operative, changing the application of at least the first brake includes releasing the first brake if the first speed of the first wheel is less than the average speed of the second and third wheels by the preset amount.
23. The method of claim 21 wherein:
when the first, second, and third speed sensors are operative, changing the application of at least the first brake includes releasing the first brake if the first speed of the first wheel is less than the average speed of the second and third wheels by the preset amount; and
when at least the first speed sensor is inoperative, continuing to apply the first brake to the first wheel includes continuing to apply the first brake if the first speed of the first wheel is less than the average speed of the second and third wheels by the preset amount.
24. A method for slowing a vehicle on the ground, the vehicle having a wheel for supporting a portion of the vehicle on the ground, the vehicle further having a brake and a speed sensor associated with the wheel, the method comprising:
receiving a control input to slow the vehicle;
determining if the speed sensor is operative;
when the speed sensor is operative, controlling the brake according to a first routine in response to receiving the control input; and
when the speed sensor is inoperative, controlling the brake according to a second routine in response to receiving the control input, the second routine being different than the first routine.
25. The method of claim 24 wherein controlling the brake according to the second routine includes applying the brake to the wheel in response to the control input.
26. The method of claim 24 wherein the wheel is a first wheel, the brake is a first brake, and the speed sensor is a first speed sensor, and wherein controlling the brake according to the first routine includes:
determining if a first speed of the first wheel differs from a second speed of a second wheel by a preset amount; and
if the first speed differs from the second speed by the preset amount, changing the application of at least one of the first and second brakes.
27. The method of claim 24 wherein the wheel is a first wheel, the brake is a first brake, and the speed sensor is a first speed sensor, and wherein controlling the brake according to the first routine includes:
determining if a first speed of the first wheel differs from a second speed of a second wheel by a preset amount; and
if the first speed differs from the second speed by the preset amount, releasing at least one of the first and second brakes.
28. The method of claim 24 wherein controlling the brake according to the first routine includes:
determining if a first speed of the wheel differs from a second speed associated with the speed of the vehicle by a preset amount, the first speed being determined with the speed sensor; and
if the first speed differs from the second speed by the preset amount, changing the application of the brake.
29. The method of claim 24 wherein controlling the brake according to the first routine includes:
determining if a first speed of the wheel differs from a second speed associated with the speed of the vehicle by a preset amount, the first speed being determined with the speed sensor; and
if the first speed differs from the second speed by the preset amount, releasing the brake.
30. A system for slowing a vehicle on the ground, the vehicle having at least first and second wheels for supporting at least a portion of the vehicle on the ground, the vehicle further having a first brake and a first speed sensor associated with the first wheel, and a second brake and a second speed sensor associated with the second wheel, the system comprising:
means for receiving a first control input to slow the vehicle;
means for applying the first brake to the first wheel and the second brake to the second wheel in response to receiving the first request;
means for determining if the first and second speed sensors are operative;
means for determining if a first speed of the first wheel differs from a second speed of the second wheel by a preset amount when the first and second speed sensors are operative;
means for changing the application of at least one of the first and second brakes if the first speed differs from the second speed by the preset amount; and
means for continuing to apply the first brake to the first wheel and the second brake to the second wheel while receiving the first control input when at least one of the first and second speed sensors is inoperative.
31. The system of claim 30 wherein the means for changing the application of at least one of the first and second brakes includes means for releasing at least one of the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount.
32. The system of claim 30 wherein:
the means for changing the application of at least one of the first and second brakes when the first and second speed sensors are operative includes means for releasing at least one of the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount; and
the means for continuing to apply the first brake to the first wheel and the second brake to the second wheel when at least one of the first and second speed sensors is inoperative includes means for continuing to apply the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount.
33. The system of claim 30 wherein the means for changing the application of at least one of the first and second brakes includes means for releasing the first brake if the speed of the first wheel is slower than the speed of the second wheel by the preset amount.
34. The system of claim 30 wherein the vehicle is an aircraft having at least a first wheel truck and a second wheel truck, and wherein the means for applying the first brake to the first wheel and the second brake to the second wheel includes means for applying the first and second brakes on the first wheel truck.
35. A system for slowing a vehicle on the ground, the vehicle having a wheel for supporting a portion of the vehicle on the ground, the vehicle further having a brake and a speed sensor associated with the wheel, the system comprising:
means for receiving a control input to slow the vehicle;
means for determining if the speed sensor is operative;
means for applying the brake to the wheel according to a first routine in response to receiving the control input when the speed sensor is operative; and
means for applying the brake to the wheel according to a second routine in response to receiving the control input when the speed sensor is inoperative, the second routine being different than the first routine.
36. The system of claim 35 wherein the means for controlling the brake according to the second routine includes means for applying the brake to the wheel in response to the control input.
37. The system of claim 35 wherein the wheel is a first wheel, the brake is a first brake, and the speed sensor is a first speed sensor, and wherein the means for controlling the brake according to the first routine includes:
means for determining if a first speed of the first wheel differs from a second speed of a second wheel by a preset amount; and
means for changing the application of at least one of the first and second brakes if the first speed differs from the second speed by the preset amount.
38. The system of claim 35 wherein the means for controlling the brake according to the first routine includes:
means for determining if a first speed of the wheel differs from a second speed associated with the speed of the vehicle by a preset amount, the first speed being determined with the speed sensor; and
means for changing the application of the brake if the first speed differs from the second speed by the preset amount.
39. An aircraft system comprising:
a first landing wheel configured to support at least a portion of an aircraft on the ground;
at least a second landing wheel configured to support at least a portion of the aircraft on the ground;
a first brake and a first speed sensor associated with the first wheel;
a second brake and a second speed sensor associated with the second wheel; and
a processor operatively coupled to the first and second brakes and the first and second speed sensors, wherein the processor is configured to respond to a first control input to slow the aircraft by:
applying the first brake to the first wheel and the second brake to the second wheel;
determining if the first and second speed sensors are operative;
when the first and second speed sensors are operative,
determining if a first speed of the first wheel differs from a second speed of the second wheel by a preset amount; and
if the first speed differs from the second speed by the preset amount, changing the application of at least one of the first and second brakes;
when at least one of the first and second speed sensors is inoperative, continuing to apply the first brake to the first wheel and the second brake to the second wheel while receiving the first control input.
40. The aircraft system of claim 39 wherein the processor is further configured to release at least one of the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount when the first and second speed sensors are operative.
41. The aircraft system of claim 39 wherein:
the processor is further configured to release at least one of the first and second brakes if the first wheel speed differs from the second wheel speed by the preset amount when the first and second speed sensors are operative; and
the processor is still further configured to continue applying the first brake to the first wheel and the second brake to the second wheel if the first wheel speed differs from the second wheel speed by the preset amount when at least one of the first and second speed sensors is inoperative.
42. The aircraft system of claim 39 , further comprising:
a first wheel truck; and
a second wheel truck spaced apart from the first wheel truck, wherein the first and second landing wheels are rotatably mounted to the first wheel truck.
43. The aircraft system of claim 39 , further comprising:
a first wheel truck; and
a second wheel truck spaced apart from the first wheel truck, wherein the first and second landing wheels are rotatably mounted to the first wheel truck in alignment with each other.
44. The aircraft system of claim 39 wherein the processor includes a bypass component configured to cause the processor to continue applying the first brake to the first wheel and the second brake to the second wheel while receiving the first control input when at least one of the first and second speed sensors is inoperative.
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US10/641,461 US6851649B1 (en) | 2003-08-14 | 2003-08-14 | Methods and systems for controlling wheel brakes on aircraft and other vehicles |
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US10/641,461 US6851649B1 (en) | 2003-08-14 | 2003-08-14 | Methods and systems for controlling wheel brakes on aircraft and other vehicles |
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