Method for providing information to an operator for managing at least one cumulative ageing process

Abstract

The invention relates to a method capable of providing information to an operator, for example a pilot, or to an automated system, for example an autopilot, to assist in managing, flight after flight, at least one cumulative ageing process, for example creep, affecting at least part of a gas turbine of an aircraft of versatile use, for example a helicopter, in order to make the best use of such a turbine over the long term.

Description

[0001] DESCRIPTION

[0002] TITLE: Method capable of providing information to an operator for the management of at least one cumulative aging

[0003] Technical field of the invention

[0004] The invention relates to a method capable of providing information to an operator, for example a pilot, or to an automated system, for example an Autopilot, making it possible to help manage flight after flight, at least cumulative aging, for example creep, of at least one part of a gas turbine of a versatile aircraft, for example a helicopter, in order to get the best out of it in the long term.

[0005] State of the prior art

[0006] An aircraft pilot generally has access to piloting indications relating to propulsion systems, displayed in the cockpit. These indications refer in particular to certified limits (maximum limits not to be exceeded, limits required in the flight manual), these limits being managed by the pilot or managed by the computer.

[0007] Such limits are, for example, N1 (gas generator rotation speed at the high-pressure shaft), the T45H conformal temperature of the high-pressure turbine, the torque of the power shaft, or an indicator combining this information. These limits constitute, for example, thresholds not to be exceeded in stabilized flight, and for which maximum continuous operating times may be defined by regulation.

[0008] These indications do not take into account objectives per mission, such as a quota, or the notion of acceptable cumulative aging. They are purely instantaneous and are not intended to prevent cumulative aging modes from leading to a need for premature repair of the turbomachine, for example before its scheduled general overhaul.

[0009] In the context of relatively unpredictable and variable uses, such as airliner missions, there are predictive methods that set binary throttle position indices that correspond correctly to maintenance costs. These predictive methods also most often include maintenance costs and fuel consumption costs.

[0010] For versatile uses, for example for the varied missions of helicopters, the correspondence of a binary setpoint (whether it is a torque, a gas generator speed or a temperature) with the costs is not reliable. Today, in this context, only ground monitoring of the meters exists, in particular with regard to creep, carried out manually or with tools.

[0011] However, in this context, concerning these complex cumulative aging events, such a posteriori monitoring does not provide any useful prospective indication for subsequent flights and is not in the current state of being able to help the pilot to respect a cumulative objective during the flight, for example an objective given by a fleet manager.

[0012] Such monitoring or indications also do not provide information that would enable the pilot to understand and develop an intuition of the actions to be taken to manage aging modes. Indeed, these aging phenomena are multi-factorial and non-linear. Consequently, a pilot cannot develop a reliable intuition of the conditions under which these aging modes accelerate or slow down, without additional indication.

[0013] Cumulative aging is a form of damage that increases over time. Such aging is perfectly consistent with the phenomenon of turbine blade creep, in the context of the intended application, but can also be oxidation, corrosion, or mechanical wear of parts (friction wear or bearing wear, for example).

[0014] Other types of aging may also occur, such as predominantly "cyclic" aging modes, relating to a number of times stress thresholds are crossed, both upwards and downwards (oligocyclic fatigue (LOF), thermal cycling, number of starts / stops, etc.). However, it is difficult to act on such cyclic aging, so they are not covered by this document.

[0015] Presentation of the invention

[0016] This document aims to address the above-mentioned drawbacks.

[0017] To this end, the present document proposes a method capable of providing information to an operator, for example a pilot, or to an automated system, concerning at least one cumulative aging, for example creep, of at least one part of a gas turbine of an aircraft during a mission of said aircraft, said method comprising a step of determining an aging progression score defined as follows: CCORF = f 0, siA(t) < Sl

[0018] (otherwise, = TERM1 + TERM2 + TERM3 + TERM4 + TERM 5 for the calculation of which we define: the quota of the mission, Q = QFactor * — where

[0019] • QFactor is a factor between 0.1 and 10, for example, to be made modifiable by the operator if possible,

[0020] • SD is a major maintenance trigger threshold for a CV aging counter, in hours,

[0021] • DQ is the flight time between two overhauls of said part of the gas turbine or the target life of said part of the gas turbine, in hours.

[0022] SD the default quota of the mission, Q 0FF = — the cumulative aging counter CV which is a value proportional to the cumulative aging, - the forecast flight duration of the mission entered in hours, M, for example between 0.2 and 3 hours, the default forecast flight duration of the mission in hours, M 0FF , for example of the order of 1 hour,

[0023] Y a parameter to adapt to the application context, chosen between M DFF / 2 and M 0FFthe cumulative flight duration of the mission, in hours, at a time t of the mission, T(t) a first threshold S1, for example between 0.3 and 0.8, for example equal to 0.5, a second threshold S2, for example between 3 and 10, for example equal to 5, the start of the mission is defined by the time t= tO of start of flight a time t = t1 of end of a phase called start of mission is also defined so that: t1 - tO greater than a duration between 1 and 15 minutes, and / or t1 is the first time t greater than tO for which the flight speed of the aircraft is greater than a predetermined speed, for example 40 Ktas for a helicopter, and / or t1 is the first time t greater than tO for which the altitude of the aircraft relative to the ground, also called ground clearance, is greater than a determined value, for example 500 feet, a sliding duration X in seconds, for example between 10 and 30 seconds, for example of the order of 20 seconds, I . ■ .I- XVA z \ CV (t) - CV(tX) the average sliding gradient over X seconds, A(t) = - — - *(,36OOJ the cumulative total per flight hour since the start of the mission (tO), at a time t of the mission without information on the forecast flight duration of mission M,. the cumulative flight time per hour since the start of the mission, at a time t of the mission, anticipating a flight duration of the “usual short missions” of Y, in hours, the cumulative total per flight hour since the start of the mission, at a time t of the mission anticipating the forecast mission flight duration entered M, 2, if t > tl and M = MDEF and Q = QDEF and D(t) > (T(t) / M),

[0024] TERM2 = otherwise 1, if t > tl and if trend of B(t) over X seconds monotonically increasing, said method comprising a step of providing said information to the operator or to the automated system, dependent on said aging score.

[0025] The step of providing said information to an operator can be carried out by display.

[0026] As previously stated, cumulative aging of a gas turbine part is the damage to the affected part that increases over time. Such aging is mainly the creep phenomenon, but can also be oxidation, corrosion, or mechanical wear of the parts of the affected part.

[0027] The cumulative aging counter CV is a value generally provided by the gas turbine computer, and proportional to the cumulative aging, measured or determined by calculation, from values ​​from sensors (gas generator rotation speed, temperature within the gas turbine, torque, outside temperature, deformations, etc.). The higher the CV value, the greater the cumulative aging of the parts of the concerned part or module of the gas turbine.

[0028] An aircraft mission is defined by a succession of flight phases between a start and an end of the mission. Typically, such a mission may include one or more takeoff and landing phases, and flight phases at varying speeds.

[0029] The major maintenance trigger threshold is a threshold predetermined by the gas turbine manufacturer, beyond which a major maintenance operation, known as major maintenance, is necessary to ensure the proper functioning of the gas turbine or prevent premature damage to it. Such an operation generally requires the removal of the gas turbine.

[0030] The flight time between two general overhauls is known by the abbreviation TBO for "Time Between Overhaul".

[0031] The target DQ life can be a flight duration greater than the time between two overhauls, for example equal to twice the time between two overhauls.

[0032] The predicted flight duration of the mission entered M is a value determined before the start of the mission and entered into an aircraft computer, for example via an interface. This duration can be entered by an operator, for example a pilot.

[0033] The expected flight duration, by default or not, of the mission entered M or MDEF is for example between 0.2 and 3 hours. MDEF is for example around 1.5 hours.

[0034] M will be filled in with the collection value of MDEF if M is not filled in by the operator.

[0035] The flight duration of usual short missions Y will either be defined in a fixed way for a given application, for example of the order of 0.8 hours if MDEF = 1 -5h, or determined by the application and calculated as an average of the flight durations of previous missions of the aircraft less than MDEF in the interval, of M DBF / 2 to M 0£

[0036] The Y parameter can be adapted for example in this interval depending on whether we have more or less mission frequencies much shorter than MDEF.

[0037] The cumulative flight duration of the mission at time t, T(t) is the time elapsed between the start of the mission tO and time t.

[0038] The sliding CV value over X seconds at time t is equal to the difference between the CV values ​​at time t and CV at time tX.

[0039] The calculation of all or part of said terms can be carried out in real time, at time periods of less than 1 second for example, of the order of 500ms for example.

[0040] By inhibiting the calculations of terms 2, 3, 4 and 5, i.e. by setting these terms to 0, during the start phase of the mission (T(t) < t1), the operator, for example the pilot, is not bothered by the appearance of indications during the most delicate flight phases (takeoff, etc.).

[0041] Each term serves a different purpose and therefore allows them to be combined.

[0042] When the engine load level at time t leads to minor aging (S1 to be defined by the engine manufacturer), the score is set to zero regardless of the value of the different terms. There is in fact no point in providing information, for example by display, if the engine load no longer significantly changes the final total, there is no need to continue to encourage reducing the load. This is an important element of the invention to avoid unnecessarily limiting solutions operationally since exceeding the quota does not involve any risk and the following missions always offer possibilities for compensation.

[0043] The first term TERM 1 is used to signal to the operator a very high demand, without any obvious relationship to the indications of acceptable speed limits. This is a first sign for the operator that the current flight conditions may lead to significant cumulative aging, and it can be displayed from the very first moments of the flight. It is also regular information that enriches the operator's intuitive perception of the situation.

[0044] The second term TERM 2 allows the score to be reinforced if the level of stress at time t leads to an increase in aging not compensated by the increase in mission flight duration, versus the quota Q, or greater than a linear progression (if the values ​​M and Q are not defined by the operator). This indication reinforces the score when, at the start of the mission in particular, the stress is carried out at a high rate. It is an intermediate variant between the gradient and the cumulative aging which integrates any previous debits and credits and allows a signal in the first part of the mission. It gradually loses relevance with the lengthening of the mission and then no longer contributes to the score, unless the stress remains truly excessive.

[0045] Instead of giving a weight of 2 to TERM 2 (“option 1”) in the case where no effort to customize the objective of future missions is provided, (i.e. when neither the quota Q nor the mission flight duration M have been defined, for example by the operator), the weight can remain at 1, which leads to a maximum score lower than 5 (“option 2”).

[0046] The fourth term TERM 3 makes it possible to increase the score if the quota is exceeded by considering that the mission will last Y hours and to lower the score if, the flight duration Y being exceeded, the cumulative total has converged again below the quota. This term allows a first level of progression of the score in absolute value of the cumulative hourly total, avoiding an untimely increase in the score at the start of the mission if the minimum duration of Y hours was not used (reason why B(t) is not used in absolute value). Such a process can also allow piloting assistance and / or training for the operator of the critical conditions leading to an aggravation of said cumulative aging.

[0047] Instead of giving a weight of 2 to TERM 3 (“option 1”), in the case where no effort to customize the objective of future missions is provided, (i.e. when neither the quota Q nor the mission flight duration M have been defined, for example by the operator) the weight can remain at 1, which leads to a maximum score lower than 5 (“option 2”).

[0048] The terms TERM 4 and TERM 5 are inhibited (equal to 0) when no effort to customize the objective of future missions is provided (i.e. when neither the quota Q nor the mission flight duration M have been defined, for example by the operator). These terms can also be inhibited for other reasons (desire for discreet displays and low use, for example in a context of too much variability of missions).

[0049] The fifth term TERM 4 allows the score to be increased if the cumulative score follows a progression greater than a linear cumulative score towards the quota Q entered, for the mission flight duration M entered. As the start of the mission is generally more demanding, this allows vigilance to be increased fairly early and fairly precisely, and indicates that moderation or pilot action is desirable.

[0050] The sixth term TERM 5 allows the score to be reinforced by comparing the cumulative total to the Q quota, particularly in a case where it is not possible to remain within the quota during the mission but it is still possible to limit the excess.

[0051] It is also possible to freeze the score display during transient flight phases when the pilot is otherwise occupied. Such a phase can be determined by a significant variation in the running average (for example over a given period) of the engine torque, outside a reduced range (for example +-5%) around the running average. This allows the display to be frozen during such maneuvers.

[0052] It is also possible to display a warning light, for example a green one, if A(t) < S1 (or other value) in the aircraft engine speed limits display area (first limit indicator, N1 margin, T45H - defined above), this area being a priority attention area for the pilot.

[0053] Three states of vigilance can be permitted in the “option 2” case: no vigilance: no indication of the score moderate vigilance: M = Mdef, Q = Qdef, the maximum score then being equal to 3, in the “option 2” case. strong vigilance: invitation to provide information M Mdef and M Mdef, the maximum score then being equal to 5. Conversely, in the “option 1” case, the scale of 5 is preferred and it is the fineness of indication which is degraded with scores which evolve by 2 points at a time for both TERM2 and TERM3.

[0054] It is also possible to manage the case of several cumulative agings (both creep and corrosion for example, which are two different cumulative agings).

[0055] The calculated terms are relatively stable, but instabilities may exist. To compensate for such instabilities, it is possible to add hysteresis to the score display. Some terms may have a specific hysteresis, for example, a greater one than other terms.

[0056] Cumulative aging can be creep, oxidation and / or corrosion.

[0057] Said method may be capable of providing information concerning at least two different cumulative agings, the individual score of each aging being determined and a general score is calculated on the basis of said individual scores, for example in the form of an average or a weighted average, the information provided to the user being dependent on said general score.

[0058] Whether or not t is outside the mission start phase can be determined using elapsed flight time since the start of the mission, the aircraft's flight speed, and / or the aircraft's altitude above the ground.

[0059] The level or amount of information provided to the operator may vary depending on the aging score, the value of A(t) and / or the phase of flight concerned.

[0060] The level of information may vary progressively in increments, for example by displaying a value between 0 and 5 or by displaying a progress bar, or by not displaying such a value.

[0061] The amount of information can also be varied by adding or removing information, so as to have more or less detailed information depending on the situation.

[0062] In particular, it is possible that no information is provided (e.g. no display), in certain critical flight phases, for example during the mission start phase, or if the aging is low (low score or A(t)). Increasingly complex information (different levels of information) may be provided or displayed depending on the flight phases, the aging, or at the operator's request.

[0063] In general, the invention proposes to determine or calculate laws in real time and real-time tests on these laws, leading to indications (displayable or not in the cockpit, at different degrees of detail or according to the flight phases), whatever the aircraft and the installation (single or multi-engine).

[0064] These indications are preferably not unnecessarily disruptive, particularly in flight phases that require particular attention from the pilot. (For example, they will be displayed so as to be visible during long phases - cruising or climbing flight (discreet flashing for example) - and in a constant, non-distracting, or even inhibited display (no flashing, etc.) during phases with significant power variations),

[0065] These indications encourage and guide pilots to act on long and stable phases of flight, for the management, flight after flight, of cumulative aging of major components of the propulsion system. As previously indicated, these indications can be adjusted according to the score or previous cumulative aging, according to the types and business objectives of the missions, and the operating context.

[0066] These indications must be progressive (several alert levels rather than a binary alert), such progressiveness being particularly useful when aging is difficult to predict, the short-term consequences are minor, the use of the aircraft is versatile, and to provide the pilot with a perception of flight conditions that produce cumulative aging (non-intuitive without indication or with a binary indication).

[0067] Such indications, which make it possible to identify the phases which cause more or less pronounced cumulative aging, can also contribute to more ecological management decisions (CO2 emissions, etc.).

[0068] Unlike existing applications in a non-versatile usage context, this score does not derive from an invariable cost calculation.

[0069] Here, the fleet manager, keen to get the most out of his gas turbines, will be able, by following the trend a posteriori, to modify the quota and the score instructions to be respected by the pilot to enable the pilot to manage a globally controlled cumulative aging trajectory. He will be able to do this by considering all the versatility of his priorities, the geographical context of operation, seasonality, the age of the engines, the needs for protection of the air intakes, and all the other influential factors, by a pragmatic method of learning and instructions using the graduation of the invention.

[0070] On the other hand, a combination with fuel-efficient condition indicators is a logical association with this indicator, for example the addition of a fuel economy score of 0 to 2 depending on the deviation from the most economical stable flight conditions.

[0071] The aircraft may be a rotary-wing aircraft, particularly a helicopter.

[0072] Brief description of the figures

[0073] [Fig. 1] is a diagram illustrating the evolution over time of the score during an aircraft mission, without pilot action, this diagram also representing the evolution of the power, the cumulative damage CV, the temperature of the hot parts of the gas turbine and the altitude, [Fig. 2] is a diagram representing the evolution of the terms A(t), B(t), C(t), D(t), TERM 1, TERM 2, TERM 3, TERM 4, TERM 5, during the mission,

[0074] [Fig. 3] is a diagram corresponding to Figure 1 in which a pilot action limits the score to 3,

[0075] [Fig. 4] is a diagram corresponding to Figure 1 in which a pilot action limits the score to 2,

[0076] [Fig. 5] is a diagram corresponding to Figure 1 in which a pilot action limits the score to 1,

[0077] Detailed description of the invention

[0078] In the diagrams of Figures 1 to 5, the Score, Pw, Cumul, T45H and Z curves illustrate the evolution over time of the aging progression score, output shaft power, cumulative damage, gas turbine hot section temperature and altitude respectively.

[0079] We recall that the aging progression score can be defined as follows:;CORF = { 0, if A(t) < Sl

[0080] (otherwise, = TERM1 + TERM2 + TERM3 + TERM4 + TERM 5 for the calculation of which we define:

[0081] SD the mission quota, Q = QFactor * — Or

[0082] • QFactor is a factor between 0.1 and 10, for example, to be made modifiable by the operator if possible,

[0083] • SD is a major maintenance trigger threshold for a CV aging counter, in hours,

[0084] • DQ is the flight time between two overhauls of said part of the gas turbine or the target life of said part of the gas turbine, in hours.

[0085] SD the default quota of the mission, Q DEF = — the cumulative aging counter CV, which is a value proportional to the cumulative aging the forecast flight duration of the mission entered in hours, M, for example between 0.2 and 3 hours, to be made modifiable by the operator if possible, the default forecast flight duration of the mission in hours, M 0FF , for example of the order of 1 hour,

[0086] Y a parameter to adapt to the application context, chosen between M DFF / 2 and M 0FFthe cumulative flight duration of the mission, in hours, at a time t of the mission, T(t) a first threshold 81, for example between 0.3 and 0.8, for example equal to 0.5, a second threshold S2, for example between 3 and 10, for example equal to 5, the start of the mission is defined by the time t= tO of start of flight a time t = t1 of end of a phase called start of mission is also defined so that: t1 - tO greater than a duration between 1 and 15 minutes, and / or t1 is the first time t greater than tO for which the flight speed of the aircraft is greater than a predetermined speed, for example 40 Ktas for a helicopter, and / or

[0087] - t1 is the first instant t greater than t0 for which the altitude of the aircraft relative to the ground, also called ground clearance, is greater than a determined value, for example 500 feet, a sliding duration X in seconds, for example between 10 and 30 seconds, for example of the order of 20 seconds, the average sliding gradient over X seconds, A(t) = the cumulative flight time per hour since the start of the mission (tO), at a time t of the mission without information on the forecast flight duration of mission M, the cumulative flight time per hour since the start of the mission, at a time t of the mission, anticipating a flight duration of the “usual short missions” of Y, in hours, the cumulative total per flight hour since the start of the mission, at a time t of the mission anticipating the forecast mission flight duration entered M,

[0088] TERM 1 = ,

[0089] (otherwise, 0 r 2, if t > tl and M = MDEF and Q = QDEF and D(t) > (T(t) / M),

[0090] TERM2 = \otherwise l, if t > tl and if trend of B(t) over X seconds monotonically increasing,

[0091] The mission illustrated in Figures 1 to 5 is the case of a helicopter mission: taking off at point A (time = 0), moving to point B and landing at point B;

[0092] - taking off from point B, moving to point C and landing at point C;

[0093] - taking off from point C, moving back to point A and landing at point A.

[0094] We can see from the diagram in Figure 1 that the score (here the creep score, calculated using the formula described previously summing the terms TERM 1 to TERM 6, the evolution of which is presented in Figure 2) reaches a maximum of 4. In such a case, the quota Q at the end of the mission reaches twice a desired quota and therefore largely exceeds this desired quota.

[0095] The diagram in Figure 3 illustrates the case where, during the same mission, the pilot takes actions to limit the score to 3. In the case illustrated in Figure 3, an action is taken by the pilot each time the score reaches the value 4. Thus, the pilot reduces the horizontal movement speed by 1 ktas a first time, and then again a second time later. In such a case, the quota Q at the end of the mission reaches 1.8 times the desired quota. The mission has also been extended by 30 seconds compared to the case illustrated in Figure 1.

[0096] The diagram in Figure 4 illustrates the case where, during the same mission, the pilot takes actions to limit the score to 2. In the case illustrated in Figure 4, an action is taken by the pilot each time the score reaches the value 3. Thus, the pilot reduces the horizontal speed by 4 ktas a first time, reduces this speed again by 6 ktas later and then further lowers the vertical speed by 100 feet per minute at the end of the climb. In such a case, the Q quota at the end of the mission reaches 1.2 times the desired quota. The mission has also been extended by 2 minutes compared to the case illustrated in Figure 1.

[0097] The diagram in Figure 5 illustrates the case where, during the same mission, the pilot takes actions to limit the score to 1. In the case illustrated in Figure 5, an action is taken by the pilot each time the score reaches the value 2. Thus, the pilot first reduces the vertical speed by 100 feet per minute, then reduces the horizontal speed by 4 ktas, reduces this speed again by 2 ktas later, and then lowers this speed again by 5 ktas later. In such a case, the quota Q at the end of the mission reaches 0.7 times the desired quota. The mission has also been extended by 4.6 minutes compared to the case illustrated in Figure 1. It can be seen that this extension is relatively small compared to the total flight duration of the mission.

[0098] Depending on the constraints concerning the duration of the mission, and according to the instructions of a fleet manager, the pilot (directly or via an autopilot) will be able to choose the score 4, 3 or 2 or 1 that he wishes to aim for, with the assurance of only applying the strict limitations on his flight which allow him to get closer or closer to the quota.

Claims

CLAIMS 1. Method capable of providing information to an operator, for example a pilot, or to an automated system, concerning at least one cumulative aging, for example creep, of at least one part of a gas turbine of an aircraft during a mission of said aircraft, said method comprising a step of determining an aging progression score defined as follows: CORF = (0, if A(t) < Sl (otherwise, = TERM1 + TERM2 + TERM3 + TERM4 + TERM 5 for the calculation of which we define: SD the mission quota, Q = QFactor * — Or • QFactor is a factor between 0.1 and 10, for example, to be made modifiable by the operator if possible, • SD is a major maintenance trigger threshold for a CV aging counter, in hours, • DQ is the flight time between two overhauls of said part of the gas turbine or the target life of said part of the gas turbine, in hours. SD the default quota of the mission, Q DEF = — the cumulative aging counter CV which is a value proportional to the cumulative aging, the forecast flight duration of the mission entered in hours, M, for example between 0.2 and 3 hours, the default forecast flight duration of the mission in hours, M DEE , for example of the order of 1 hour, Y a parameter to adapt to the application context, chosen between M DEE / 2 and M DEEthe cumulative flight duration of the mission, in hours, at a time t of the mission, T(t) a first threshold S1, for example between 0.3 and 0.8, for example equal to 0.5, a second threshold S2, for example between 3 and 10, for example equal to 5, the start of the mission is defined by the time t= tO of start of flight a time t = t1 of end of a phase called start of mission is also defined so that: t1 - tO greater than a duration between 1 and 15 minutes, and / or t1 is the first time t greater than tO for which the flight speed of the aircraft is greater than a predetermined speed, for example 40 Ktas for a helicopter, and / or t1 is the first instant t greater than t0 for which the altitude of the aircraft relative to the ground, also called ground clearance, is greater than a determined value, for example 500 feet, a sliding duration X in seconds, for example between 10 and 30 seconds, for example of the order of 20 seconds, I .■ . CV (t) - CV(tX) the average gradient sliding over X seconds, A(t) = - — - the cumulative flight time per hour since the start of the mission (tO), at a time t of the mission without information on the forecast flight duration of mission M, the cumulative flight time per hour since the start of the mission, at a time t of the mission, anticipating a flight duration of the “usual short missions” of Y, in hours, the cumulative total per flight hour since the start of the mission, at a time t of the mission anticipating the forecast mission flight duration entered M, said method comprising a step of providing said information to the operator or to the automated system, dependent on said aging progression score.

2. Method according to one of the preceding claims, in which the cumulative aging is creep, oxidation and / or corrosion.

3. Method according to one of the preceding claims in which said method is capable of providing information concerning at least two different cumulative agings, the individual score of each aging being determined and a general score is calculated on the basis of said individual scores, for example in the form of an average or a weighted average, the information provided to the user being dependent on said general score.

4. Method according to one of the preceding claims, in which it is determined whether or not t is outside the start phase of the mission using a flight time elapsed since the start of the mission, the flight speed of the aircraft and / or the altitude of the aircraft relative to the ground.

5. Method according to one of the preceding claims, in which the level or quantity of information provided to the operator varies according to the aging score, the value of A(t) and / or the flight phase concerned.

6. Method according to one of the preceding claims, in which the aircraft is a rotary wing aircraft.

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