Method for determining a recommended inflation pressure for an aircraft tire, and associated maintenance methods

Abstract

A method determines an inflation pressure expected in an aircraft tire provided with a pressure and temperature sensor. Also disclosed is a method for assistance in the maintenance for an aircraft tire and also a portable electronic device intended for assistance in the maintenance.

Claims

1. A method for determining an inflation pressure expected in an aircraft tire provided with a pressure and temperature sensor, the method comprising: in a preliminary stage, recording a pressure P.sub.0 and a temperature T.sub.0 of the tire, measured at a time t.sub.0, in a memory of the pressure and temperature sensor; at a moment t, measuring and comparing an internal air temperature T.sub.m of the tire and an ambient air temperature T.sub.amb; and if the two temperatures are equal or substantially equal, determining a pressure expected at the moment t, P.sub.expected_hom, using P.sub.expected_hom=P.sub.0*T.sub.m/T.sub.0; or if the two temperatures are different, determining a pressure expected at the moment t, P.sub.expected_het, using P.sub.expected_het=F(T.sub.m, P.sub.0, T.sub.0 and θ), where θ depends on a position of the pressure and temperature sensor in the tire at the moment t, wherein F is a linear function where P.sub.expected_het(t)=A(θ)*(T.sub.m(t)−T.sub.0)+P.sub.0, A(θ)=p.sub.1*θ+p.sub.2, and p.sub.1 and p.sub.2 are predetermined constants, or F is a polynomial function where P.sub.expected_het=A(θ)*(T.sub.m(t)−T.sub.0).sup.2+B(θ)*(T.sub.m−T.sub.0)+P.sub.0 and A(θ) and B(θ) are predetermined polynomial functions.

2. A method for the detection of loss of pressure in an aircraft tire provided with a pressure and temperature sensor, the method comprising: determining an expected pressure P.sub.exp of the tire using the method according to claim 1; measuring an internal air pressure P.sub.m of the tire at the moment t is measured; and comparing values P.sub.exp and P.sub.m such that if P.sub.exp=P.sub.m, then no loss of pressure is detected, and if P.sub.exp>P.sub.m, a rate of loss of pressure V.sub.p is determined, where, if V.sub.p is less than a predetermined threshold, an acceptable loss of pressure is detected, and, if V.sub.p is greater than the predetermined threshold, an unacceptable loss of pressure is detected.

3. The method according to claim 2, wherein the predetermined threshold is expressed as percentage and is between 4 and 10% per 24 h.

4. The method according to claim 2, wherein a rate of loss of pressure is calculated as follows: V.sub.p=(P.sub.0−P.sub.0,eq)/P.sub.c*(t−t.sub.0), where P.sub.0,eq is a pressure which would be necessary to have at the moment to in order for the pressure expected at the moment t to be equal to P.sub.m.

5. A method for assistance in maintenance for an aircraft tire provided with a pressure and temperature sensor, comprising: determining an expected pressure P.sub.exp of the tire using the method according to claim 1; determining a takeoff pressure P.sub.tak in the absence of maintenance; calculating a ratio of the takeoff pressure P.sub.tak to a set pressure P.sub.s and, depending on a value of the ratio, carrying out a maintenance operation.

6. The method according to claim 5, wherein the takeoff pressure P.sub.tak in the absence of maintenance is determined as follows: calculating a temperature of the tire at takeoff T.sub.tak; and calculating P.sub.tak=P.sub.0*T.sub.tak/T.sub.0.

7. The method according to claim 5, wherein the maintenance operation, knowing a set pressure P.sub.s of the tire, is selected from the group consisting of: doing nothing if the P.sub.tak/P.sub.s ratio is between 100% and 105%, inflating the tire if the ratio is between 95% and 100%, deflating the tire if the ratio is greater than 105%, and inspecting a fitted assembly if the ratio is less than 95%.

Description

DETAILED DESCRIPTION

(1) Other objectives and advantages of the invention will become clearly apparent in the description which will follow of a preferred but nonlimiting embodiment, illustrated by FIG. 1, which graphically represents the various stages employed in a method for maintenance of tyres according to the invention.

DESCRIPTION OF THE BEST EMBODIMENT OF THE INVENTION

(2) A description will now be given of an exemplary embodiment of a method according to the invention on an aircraft, provided with tyres provided with pressure and temperature sensors, taking off from an airport 1 and landing in an airport 2. It is specified here that the example will not describe the implementation of the method for just one tyre but that implementation on the other tyres is carried out similarly.

(3) At a moment t.sub.0, before takeoff from the airport 1, a note is taken of the pressure and of the internal temperature of the tyre. These values, P.sub.0=13.8 bar and T.sub.0=15° C., are then recorded in a memory of the sensor.

(4) When the aircraft lands on the airport 2 at a moment T=t.sub.0+18 hours, the following measurements are carried out: P.sub.m, T.sub.m and T.sub.amb. In this example, P.sub.m=15.1 bar, T.sub.m=70° C. and T.sub.amb=25° C. The pressure and temperature sensor is positioned with an angle of 45° with respect to the vertical.

(5) The various stages shown in the graph will subsequently be applied: The thermal state of the tyre is determined by comparing Tm and Tamb.fwdarw.in the example Tm being greater than Tamb (“yes” branch), the heterogeneity law has to be used. In stage 2, the expected pressure is then calculated by applying this heterogeneity law, and P.sub.exp_het=15.41 bar is obtained. The expected pressure is then compared with the measured pressure P.sub.m; there exists P.sub.exp_het>P.sub.m. As the pressure expected is greater than the measured pressure (“yes” branch), the rate of loss of pressure in the tyre is calculated V.sub.p=2.74%/24 h. As the rate of loss of pressure is within the limits of tolerance, in the case in point less than 5%/24 h, a maintenance operation can be ordered. In order to do this, the takeoff pressure P.sub.tak is evaluated calculated and a P.sub.tak/P.sub.s ratio is calculated according to a method as described previously. The takeoff will take place in 3 hours, at a takeoff temperature T.sub.tak=26.4° C. It is thus determined that the takeoff pressure will be P.sub.tak=13 bar. A P.sub.tak/P.sub.s=104% ratio then exists and thus no action is required.