Method and apparatus for monitoring aircraft tire air pressure

Abstract

The invention provides a method and apparatus for monitoring air pressure of a flying tire, the method comprising: collecting two or more air pressure readings from the tire at different times; calculating an estimated rate of deflation based on the air pressure readings; and calculating a time for the tire to deflate to a reference air pressure level based on the estimated rate of deflation. Each of the two or more temperature readings is associated with one of the air pressure readings, and the estimated rate of deflation is calculated by normalizing each air pressure reading based on its associated temperature reading and a universal reference temperature to obtain a temperature-normalized air pressure reading, and calculating the estimated rate of deflation based on the temperature-normalized air pressure readings. The estimated rate of deflation is compared to a threshold, and a warning is provided if the estimated rate of deflation exceeds the threshold.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201610162301.3, filed on March 21, 2016, entitled "Method and Apparatus for Monitoring Aircraft Tire Pressure", which has a priority date of March 20, 2015. TECHNICAL FIELD

[0002] The present invention relates to a method for monitoring aircraft tire pressure and an apparatus for performing such a method. BACKGROUND

[0003] An aircraft tire monitoring system is disclosed in US-A-2008 / 0055060. A sensor senses an operating parameter of the tire, such as pressure or temperature, and a signal relating to the sensed parameter is transmitted to a reader located on or in the aircraft fuselage. The reader can also send some or all of the above information to a further device, such as a display. SUMMARY

[0004] A first aspect of the present invention provides a method for monitoring aircraft tire pressure by a computer system, the method comprising: taking two or more pressure readings from a tire at different times; and calculating an estimated rate of deflation based on the pressure readings.

[0005] A second aspect of the present invention provides an apparatus for monitoring aircraft tire pressure, the apparatus comprising: a sensor system comprising a pressure sensor for taking pressure readings from a tire at different times; and a computer system configured to calculate an estimated rate of deflation based on two or more of the pressure readings, and to provide a warning based on the estimated rate of deflation.

[0006] A third aspect of the present invention provides a method for monitoring aircraft tire pressure, the method comprising: measuring tire pressure of an aircraft at each of two or more different points in time; wirelessly transmitting the measured pressure to a handheld computing device; calculating, by the handheld computing device, a rate of deflation of the tire based on the measured pressure and the point in time at which the measurement was performed, and displaying an alert on a display device associated with the handheld computing device if the rate of deflation is greater than a threshold rate of deflation.

[0007] Optionally, a time for the tire to deflate to a reference level is estimated based on the estimated rate of deflation. The estimated time can then be stored for subsequent analysis and / or displayed to a flight or maintenance crew to enable them to take appropriate action.

[0008] Optionally, the estimated rate of deflation is compared to a threshold value; and a warning is provided if the estimated rate of deflation exceeds the threshold value.

[0009] If the temperature of the tire remains constant between the different air pressure readings, then the air pressure readings can be used directly to calculate the estimated rate of air loss. More typically, the method includes acquiring an associated temperature reading for each air pressure reading, and calculating the estimated rate of air loss by normalizing each air pressure reading based on its associated temperature reading and a universal reference temperature to obtain a temperature-normalized air pressure reading, and calculating the estimated rate of air loss based on the temperature-normalized air pressure readings. The temperature readings can be acquired, for example, by a temperature sensor carried by the wheel on which the tire is mounted, or by a temperature sensor located in any other suitable location (e.g., a brake temperature sensor or an ambient temperature sensor). The temperature readings can be acquired at the same time as the air pressure readings with which they are associated, or can be acquired shortly before or after the air pressure readings with which they are associated.

[0010] All of the air pressure readings can be acquired while the aircraft is on the ground, or at least one of the air pressure readings can be an in-flight air pressure reading acquired from the tire while the aircraft is in flight.

[0011] Typically, at least one of the air pressure readings is an in-flight air pressure reading acquired from the tire while the aircraft is in flight with the tire unloaded, and the estimated rate of air loss is calculated by adjusting the in-flight air pressure reading to account for the tire being unloaded to obtain an adjusted unloaded in-flight air pressure reading, and calculating the estimated rate of air loss based on the adjusted unloaded in-flight air pressure reading.

[0012] Optionally, the in-flight air pressure reading is normalized based on its associated temperature reading and a universal reference temperature and is also adjusted to account for the tire being unloaded to obtain a temperature-normalized and adjusted unloaded in-flight air pressure reading, and the estimated rate of air loss is calculated based on the temperature-normalized and adjusted unloaded in-flight air pressure reading.

[0013] The estimated rate of air loss can be calculated based on only two air pressure readings, but more typically is calculated based on three or more air pressure readings acquired from the tire at different times. Typically, the estimated rate of air loss is calculated by fitting a curve or a straight line to the air pressure readings, for example using a least squares fitting algorithm.

[0014] Optionally, the first and second times are estimated so that the tire is deflated to a first reference air pressure level and a second reference air pressure level (e.g., 100% and 95% of a nominal reference air pressure, respectively). Optionally, the first and second times are displayed on the same display device at the same time.

[0015] Optionally, the time for the tire to deflate to the reference air pressure level is calculated by converting the selected one of the air pressure readings to a lower temperature to obtain an adjusted temperature air pressure level, and calculating the time for the tire to deflate from the adjusted temperature air pressure level to the reference air pressure level based on the estimated deflation rate. BRIEF DESCRIPTION OF DRAWINGS

[0016] Embodiments of the application will now be described, by way of example, with reference to the accompanying drawings, in which:

[0017] Figure 1 is a plan view of an aircraft;

[0018] Figure 2 shows one of the landing gear of the aircraft and its associated sensor system;

[0019] Figure 3 shows two sensor systems connected to the cockpit computer system;

[0020] Figure 4 shows some elements of the cockpit computer system;

[0021] Figure 5 is a graph showing 8 air pressure readings; and

[0022] Figure 6 is an example of a screen displayed by the cockpit computer system. DETAILED DESCRIPTION

[0023] Figure 1 is a plan view of an aircraft 10 showing the landing gear of the aircraft: the nose landing gear (NLG) 1 and 4 main landing gears (MLG) 2. Figure 2 shows the landing gear system of one of its 4 MLG, which system comprises 6 wheels, each wheel having a respective tire 3 to 8. Each wheel carries a respective sensor system 3a to 8a for taking air pressure and temperature readings from the wheel. All 22 wheels of the aircraft have identical sensor systems.

[0024] Each sensor system 3a to 8a has a wireless transmitter for transmitting data wirelessly to a receiver 12. The receiver 12 can either be mounted on a strut of the landing gear, or inside the landing gear bay into which the landing gear retracts after take-off. Alternatively, each sensor system 3a to 8a can be connected to the receiver 12 by wire.

[0025] Figure 3is a schematic diagram of a system for checking the tire air pressure of an aircraft 10. Only two sensor systems 3a and 4a are shown for clarity purposes. Each sensor system comprises: an air pressure sensor 3b, 4b for measuring the tire air pressure to generate an air pressure reading; and a temperature sensor 3c, 4c for measuring the temperature of the wheel to generate a temperature reading. A receiver 12 receives the air pressure and temperature readings via a connection which can be wired or wireless, and forwards the above readings to a cockpit computer system 13 in the cockpit of the aircraft via a connection which can also be wired or wireless.

[0026] Figure 4 is a schematic diagram of some elements of the cockpit computer system 13. The system comprises: a receiver 20 for receiving the air pressure and temperature readings from the receiver 12; a display device 21; a memory 22; a processor 23; a user interface (UI) 24, such as a touchscreen or a keyboard; and a clock 25.

[0027] When the aircraft is on the ground before a flight, each sensor system 3a to 8a is operated to record the temperature of its associated wheel and the air pressure of its associated tire at the same time. The associated ground air pressure and temperature readings are sent to the cockpit system 13 and stored in the memory 22. Each ground air pressure reading is also time-stamped based on a time reading from the clock 25.

[0028] The ground air pressure readings are taken after a flight when the temperature reading is within 5°C of the ambient temperature (as measured by an ambient temperature sensor (not shown)). The ground air pressure readings are also taken shortly before a flight. The ground air pressure readings are displayed on the display device 21, along with a warning if necessary.

[0029] Each ground air pressure reading is also normalized based on its associated temperature reading and a universal reference temperature of 15°C to obtain a temperature-normalized ground air pressure reading. This enables a direct comparison of air pressure readings taken at different temperatures. The temperature-normalized ground air pressure reading is calculated by using the fact that a temperature change of 10°C causes a tire air pressure change of approximately 3.7%. Thus, for example, if the ground air pressure reading is 250 psi, and its associated temperature reading is 30°C, the temperature-normalized ground air pressure reading is calculated as follows: 250 - [250 * (15 / 10) * 0.037] = 250 - 13.875 = 236.125 psi.

[0030] If the temperature reading has not had sufficient time to decrease to within 5°C of the ambient temperature before the next flight, the ground pressure reading is taken 30 minutes after the last flight (at this point in time the wheels will still be hot from braking). In this case, the ground pressure reading is adjusted to estimate the pressure at ambient temperature. Thus, for example, if the ground pressure reading is 240 psi, its associated temperature reading is 50°C and the ambient temperature is 20°C, the ground pressure reading at ambient temperature is calculated as follows: 240 - [240*(30 / 10)*0.037] = 240 - 26.64 = 213.36 psi.

[0031] This ground pressure reading at ambient temperature is displayed on the display device 21, along with an associated warning if required.

[0032] At a subsequent time, when the aircraft is in flight, each sensor system 3a to 8a is again operated to record the temperature of its associated wheel and the pressure of its associated tyre simultaneously. The in-flight pressure and temperature readings are sent to the cockpit system 13 and stored in the memory 22 along with their time stamps. When the aircraft is in flight, the tyre pressure is expected to decrease by approximately 4% due to the tyre being unloaded. Thus, the in-flight pressure reading is not only normalised with respect to temperature, but is also adjusted to take account of this unloading effect. Thus, for example, if the ground pressure reading immediately prior to flight is 250 psi, the in-flight pressure reading is 220 psi and the in-flight temperature reading is 10°C, the temperature normalised and unloading adjusted in-flight pressure reading is calculated as follows: 220 + [220*(5 / 10)*0.037] + [250*0.04] = 220 + 4.07 + 10 = 234.07 psi.

[0033] Finally, at a subsequent time when the aircraft has returned to the ground after flight, a further set of temperature normalised ground pressure readings is taken for each tyre, and this set of pressure readings is recorded along with their time stamps.

[0034] Figure 5 is a graph showing a set of 8 pressure readings. There are 4 temperature normalised ground pressure readings P g (1) to P g (4) and 4 temperature normalised and unloading adjusted in-flight pressure readings P f (1) to P f (4). The tyre is inflated between P g (2) and P g (3). The processor 23 fits a straight line 30 to the last 4 pressure readings P g (3), P f (3), Pf (4), P g (4) to determine the estimated air loss rate. Based on the last 4 air pressure readings P g (3), P f (3), P f (4), P g (4) to calculate the estimated air loss rate, and since the air pressure increase between P g (2) and P g (3) is greater than 5 psi, the first 4 air pressure readings P g (1), P f (1), P f (2), P g (2). Since all 4 air pressure readings P g (3), P f (3), P f (4), P g (4) have been temperature normalized to a common reference temperature of 15°C and adjusted by -4% if necessary for barometric weight, they can effectively be compared to each other to determine the air loss rate.

[0035] Any suitable method can be used to calculate the straight line 30 - for example a least squares fit. The gradient of the straight line 30 gives the estimated air loss rate R = ΔP / ΔT.

[0036] The estimated air loss rate is calculated for each tyre. The processor 23 determines the tyre with the highest air loss rate, and optionally compares the highest air loss rate to a threshold and provides a warning on the display device 21 if the estimated air loss rate exceeds the threshold. A suitable threshold can for example be an air loss rate that would result in a loss of air pressure of more than 2% in 24 hours. Thus, if the latest air pressure reading is 250 psi, an air loss rate greater than the threshold (0.02*250) / 24 = 0.208 psi / hour would result in a warning being displayed.

[0037] The following Table 1 gives an example of ground air pressure readings taken at a machine wheel temperature of 20°C of 250 psi. The memory 22 stores a reference air pressure level of 244 psi and compares the ground air pressure readings to this reference air pressure level to calculate the air pressure percentage. Thus, for a ground air pressure reading of 250 psi, the air pressure percentage is 102%. Based on a deflation rate of 0.34 psi / hour, the air pressure will decrease from 250 psi to the reference air pressure level (244 psi) in 6 hours and to 95% of the reference air pressure level in 53 hours. Note that in this case, since the machine wheel is at a relatively low temperature, the times to deflate to 100% and 95% are calculated from the initial air pressure reading of 250 psi without first adjusting the initial air pressure reading with respect to temperature. Thus, in this case, the times of 6 hours and 53 hours are estimates based on the assumption that the temperature remains constant at 20°C.

[0038]

[0039] Air pressure differential to 100% (244 psi) 6 Time to 100% (hours) 18 hours

[0040]

[0041] In the example of Table 1, the deflation rate of 0.34 psi / hour is greater than the threshold of (0.02*250) / 24 = 0.208 psi / hour, so a warning can be displayed in addition to the data presented in Table 1.

[0042] The following Table 2 gives an example of ground air pressure readings taken at a machine wheel temperature of 55°C of 300 psi. In this case, unlike Table 1 above, the time to deflate to the reference air pressure level is calculated by first converting the air pressure reading to the ambient temperature reading taken by an ambient temperature sensor (not shown) (in this case, 15°C) to obtain an adjusted temperature air pressure level, and then calculating the time for the tire to deflate from this adjusted temperature air pressure level to the reference air pressure level based on the estimated deflation rate. This gives an adjusted temperature air pressure reading of 256 psi (105%) and, based on a deflation rate of 0.34 psi / hour, the air pressure will decrease from 256 psi (105%) to the reference air pressure level (244 psi) in 34 hours and to 95% of the reference air pressure level in 69 hours. Thus, in this case, the time estimates are based on the assumption that the temperature decreases from 55°C to a lower ambient temperature of 15°C. Note that the ambient temperature in this example is 15°C, which happens to be the same as the general reference temperature used above to calculate the estimated deflation rate. However, this need not be the case, and instead the ambient temperature reading can be, for example, 10°C or 20°C.

[0043]

[0044]

[0045]

[0046]

[0047] Figure 6 is an example of a display screen that can be presented to the flight crew on the display 21. Note that this display screen is for a different aircraft having only 6 wheels rather than (as in the example of Figure 1 ) 22 wheels. For each wheel, the tire air pressure, air pressure percentage, and temperature are displayed along with the estimated time to reach 100% and 95%. Figure 6 The example of

[0048] The estimated time is based on the time stamp and actual air pressure of the most recent air pressure reading for each tire (rather than being based on the current time or the temperature-adjusted air pressure reading).

[0049] If the percentage is below 100%, a warning is displayed in the column titled "Tire Air Pressure Warning".

[0050] The ambient temperature sensor (not shown) measures the current ambient temperature, which is displayed along with the destination airport name and the destination temperature expected at the time of arrival. This destination temperature can be obtained automatically by the processor 23 by means of a weather forecast for the destination, or can be manually entered via the user interface 24.

[0051] The temperature-adjusted air pressure reading is calculated based on the current ambient temperature and is displayed in the column titled "Estimated Ambient Air Pressure". Thus, for example, if the ground pressure reading is 280 psi, its associated ground temperature reading is 50°C, and the ambient temperature is 20°C, the estimated ambient air pressure is calculated as follows: 280 - [280*(30 / 10)*0.037] = 280 - 31.08 = 248.92 psi.

[0052] The temperature-adjusted air pressure reading is also calculated based on the estimated destination temperature and is displayed in the column titled "Estimated Destination Air Pressure". Thus, for example, if the ground air pressure reading is 280 psi, its associated ground temperature reading is 50°C, and the destination temperature is 0°C, the estimated destination air pressure is calculated as follows: 280 - [280*(50 / 10)*0.037] = 280 - 51.8 = 228.2 psi.

[0053] An estimated destination air pressure that is low generates a warning to prompt the ground crew to further inflate the tires before the flight.

[0054] The reference air pressure level (by which the pressure percentage is calculated) of the wheels of the front landing gear and the main landing gear is also displayed.

[0055] The above method can be implemented by the cockpit system 13 in cooperation with the sensor system 3a to 8a, or it can be implemented by a hand-held device (not shown) which the ground crew uses to query the sensor system 3a to 8a and to calculate and display Figure 6 the information shown.

[0056] The above tire pressure monitoring method is executed to provide a tire pressure history of each wheel and to provide advanced notification of imminent problems and recommended actions: specifically, it is possible to help predict when the next tire inflation is needed; to monitor the occurrence of a malfunction by monitoring the pressure loss rate of each wheel and detecting a higher than average air loss rate; and to detect poor tire inflation practices.

[0057] In the above embodiments of the invention, wheel temperature sensors 3c and 4c are provided to generate a wheel temperature reading for each wheel. Brake temperature sensors (not shown) are also provided for capturing a brake temperature reading for each wheel of the MLG 2 (for the NLG 1, there is no brake and therefore no brake temperature sensor). If a wheel temperature reading is not available (in case the wheel temperature sensors 3c, 4c are not working or in case no wheel temperature sensors 3c, 4c are provided), the system can use a brake temperature reading or an ambient temperature reading to replace the wheel temperature reading by the following process. After a flight, when the brake temperature reading is the same as the ambient temperature reading (as read by an ambient temperature sensor) + / - 5°C, or when the brake temperature reading is equal to 5°C, or after 3 hours from the last flight and the brake temperature reading is less than 50°C, a ground air pressure reading is captured together with the associated brake temperature reading and ambient temperature reading. For the MLG 2, the ground air pressure reading is normalized based on its associated brake temperature reading and for the NLG 1, the ground air pressure reading is normalized based on its associated ambient temperature reading.

[0058] If a brake temperature reading is not available for a given tire, its tire pressure and the pressure of its wheel axle pair tire (i.e. the tire sharing the same wheel axle) can be recorded simultaneously. If the temperature of the wheel axle pair tire is also not available, the tire pressure is recorded when the last tire pressure on that landing gear was recorded.

[0059] The tire pressure reading and the ambient temperature reading of each wheel of the NLG 1 are recorded when the readings of the MLG 2 are captured. If no MLG readings are captured (due to a quick turnaround), the tire pressure reading and the ambient temperature reading of each wheel of the NLG 1 are recorded at the start of the launch.

[0060] If the aircraft has been in flight for a significant period of time, then when the processor 23 is informed that the landing gear is being deployed (indicating that the aircraft is about to land), this is used as a trigger event to take in-flight barometric pressure readings and associated brake temperature readings. As the brake temperature readings for the NLG 1 are not available, this in-flight method is only applicable to the MLG 2.

[0061] Although the application has been described above with reference to one or more preferred embodiments, it will be understood that various changes or modifications can be suggested to one skilled in the art, and it is intended that the scope of the application be limited only by the broadest interpretation of the appended claims.

Claims

1. An apparatus for monitoring the air pressure of an aircraft tire, the apparatus comprising: a sensor system comprising a barometric pressure sensor for collecting barometric pressure readings from the tire at different points in time; and a handheld computing device configured to receive the barometric pressure readings via a wireless connection; wherein the handheld computing device is configured to compute an estimated rate of deflation of the tire based on two or more of the barometric pressure readings, and to provide a warning on a display device of the handheld computing device if the estimated rate of deflation exceeds a threshold value.

2. The apparatus of claim 1, wherein, The handheld computing device is configured to estimate a time for the tire to deflate to a reference barometric pressure level based on the estimated rate of deflation.

3. The apparatus of claim 1 or 2, wherein, The handheld computing device is configured to compare the estimated rate of deflation to the threshold value to provide the warning on the display device if the estimated rate of deflation exceeds the threshold value.

4. The apparatus of claim 1 or 2, wherein, The sensor system comprises a temperature sensor for collecting temperature readings, wherein the estimated rate of deflation is computed by normalizing each barometric pressure reading based on an associated temperature reading from the temperature sensor and a general reference temperature to obtain a temperature-normalized barometric pressure reading, and the handheld computing device is configured to compute the estimated rate of deflation based on the temperature-normalized barometric pressure readings.

5. The apparatus of claim 4, wherein, The handheld computing device is configured to estimate a time for the tire to deflate to a reference barometric pressure level based on the estimated rate of deflation.

6. The apparatus of claim 4, wherein, The handheld computing device is configured to estimate a barometric pressure at a destination, and to provide a warning on the display device if the estimated barometric pressure at the destination is low.

7. The apparatus of claim 1, comprising a plurality of sensor systems such that each wheel of the aircraft has an associated sensor system.

8. A method for monitoring barometric pressure of an aircraft tire, the method comprising: measuring a tire barometric pressure of the aircraft at each of two or more different points in time; wirelessly transmitting the measured barometric pressure to a handheld computing device; computing, by the handheld computing device, a rate of deflation of the tire based on the measured barometric pressure and the point in time at which the measurement was performed; and displaying an alert on a display device of the handheld computing device if the rate of deflation is greater than a threshold rate of deflation.

9. The method of claim 8, further comprising: computing a time for the tire to deflate to a reference barometric pressure level based on the computed rate of deflation.

10. The method of claim 9, further comprising: displaying the time for the tire to deflate to the reference barometric pressure level.

11. The method of claim 9 or 10, wherein, The time for the tire to deflate to the reference barometric pressure level is computed by converting a selected one of the barometric pressure readings to a lower temperature to obtain an adjusted temperature barometric pressure level, and computing a time for the tire to deflate from the adjusted temperature barometric pressure level to the reference barometric pressure level based on the computed rate of deflation.

12. The method of claim 8, further comprising: computing a first time for the tire to deflate to a first reference barometric pressure level based on the computed rate of deflation; and computing a second time for the tire to deflate to a second reference barometric pressure level based on the computed rate of deflation.

13. The method of claim 12, further comprising: displaying the first time and the second time simultaneously on a single one of the display devices.

14. The method of any one of claims 8 to 10, further comprising taking an associated temperature reading for each barometric pressure reading, wherein, The computed air loss rate is computed by normalizing each air pressure reading based on its associated temperature reading and a universal reference temperature to obtain temperature-normalized air pressure readings, and computing the air loss rate based on the temperature-normalized air pressure readings.

15. The method of any one of claims 8 to 10, wherein, The computed air loss rate is computed based on three or more air pressure readings taken from the tire at different times.

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