WO2010092080A1

WO2010092080A1 - Method for monitoring the health status of devices that affect the starting capability of a jet engine

Info

Publication number: WO2010092080A1
Application number: PCT/EP2010/051645
Authority: WO
Inventors: Christian Aurousseau; Alexandre Ausloos; Xavier Flandrois; Jean-Rémi Masse; Pierre Charles Mouton
Original assignee: Snecma
Priority date: 2009-02-11
Filing date: 2010-02-10
Publication date: 2010-08-19
Also published as: FR2942001B1; FR2942001A1

Abstract

The invention relates to a method for monitoring the health status of the modules of the engine and the devices that affect the starting capability of an aircraft engine, including: acquiring engine and aircraft parameter measurements, said parameters affecting the starting capability of the engine, based on measurements acquired; extracting specific indicators selected because they represent the health status of the starting capability; normalising said indicators, which are set according to standard conditions, in other words, indicators in which the influence of context variables has been removed such as only to keep the influence of damage to the aircraft, the engine and the devices thereof; detecting anomalies and positioning said anomalies by means of statistical analysis tools and the knowledge of experts regarding the operation of the aircraft engine.

Description

MONITORING THE HEALTH STATUS OF EQUIPMENT INVOLVED IN THE STARTING CAPACITY OF A

TURBOJET

DESCRIPTION

TECHNICAL AREA

The invention relates to the monitoring of the state of health of the engine modules or the equipment involved in the starting capacity of a turbojet engine.

STATE OF THE PRIOR ART The starting of an aircraft engine is an operation which requires the participation of many parts of the engine and its equipment. There are two types of startup: the automatic mode and the manual mode. The boot sequence is however the same in both cases:

- Supply of the air ducts: by an auxiliary turbine or APU (for "Auxiliary Power Unit"), by intercommunication of the supply (or "cross bleed" in English) or by an independent source,

- Opening of the valve SAV (for "Starter Air Valve" in English), observation of the winding of the high pressure compressor or CoHP, by the starter via a gearbox or AGB (for "Auxiliary Gear Box" in English),

- feeding and breakdown of the candles, - opening of the HPSOV valve (for "high-pressure shut-off valve") and fuel injection, detection of ignition and monitoring of the exhaust gas temperature of the engine or EGT, closing the service valve at self-training (called "cut-out"),

- idle confirmation,

- Stop the breakdown of the candles. Many devices come into operation during this phase of engine startup and means are implemented for the detection of possible failures.

The start is already monitored to check its smooth running but also to preserve the other organs of the engine in case of problems (for example in case of overheating). The pilot must control the return of the sensors during start-up in addition to the automated protection and alarms of the automatic controller with full redundant authority or FADEC (for "FuIl Authority Digital Engine Control"). This information is the starting point of the monitoring system of start-up or monitoring. The measurement of the following parameters is sent to the pilot in the cockpit: the speed of the HP compressor or CoHP (high pressure): N2, the compressor speed BP or CoBP (low pressure): Nl,

- the fuel flow: FF, the exhaust gas temperature: EGT,

- the oil pressure,

- the position of the service valve, - the position of the HPSOV valve.

Alerts indicate whether the oil pressure is low and the EGT temperature is high.

Some recommendations are made to the pilot. Stopping the ignition prematurely in the start sequence (ie if N2 is not high enough) can cause a "warm" start. If the switch that controls the service valve moves to the closed position before the motor has reached the auto-drive speed (between 50% and 55% of N2 depending on the engine), there is a risk of starting "hot". Do not order the re-opening of the service valve until the N2 speed is below 20% otherwise there is a risk of breaking the starter clutch, called "crash engagement".

The start interrupt conditions are:

- the absence of rotation of the Nl at the time of the ignition, - the absence of indication of oil pressure before the engine is idling, the absence of increase of the EGT 10 seconds after the ignition fuel injection,

the absence or the very slight increase of Nl or N2 with respect to the EGT, the EGT quickly approaching the allowable limit at startup.

To this, it must be added that it is forbidden to operate with an unsealed service valve and that the battery available for the supply of the spark plugs must be connected to a functioning ignition chain.

The FADEC calculator allows a number of protections. The so-called "Hot Start Alerting" alarm is used to detect overheating during start-up. The alert threshold is defined according to the N2 regime and the residual value of the EGT. This bound is always less than the "Starting EGT limit". If the value is abnormally high, the ECU flashes the EGT indication to alert the driver and sets the Hot_start_detected variable to "True". This value returns to "False" if the engine reaches idle or if the start command changes to the "off" position (that is, if the driver orders the engine to stop).

The "EGT Start Overtemperature Annunciation" protection occurs when the value of the EGT at startup (ie under the idle speed) exceeds the value of the EGT "Start Maintenance Limit". The corresponding variable then takes the value "True".

The detection of the "Starting Overtemperature" event is based on the definition of a threshold value of the EGT during the start-up phase. If this limit is exceeded, then the ECU turns off the ignition, closes the fuel dispenser or FMV and maintains this configuration until the start command is set to "off".

Detection of the "Rollback Overtemperature" event occurs when the engine is on the ground and has reached idle speed, but falls below 50% of the N2 and the EGT exceeds its threshold. The ECU reacts in the same way as for the "Starting Overtemperature" event.

The protection called "Wet Start Protection" intervenes if the ignition does not take place after a time considered reasonable following the injection of fuel. The ECU then cuts the spark plugs and closes the FMV valve. Non-ignition is detected if, on the ground, the voltage supplying the spark plugs being available, the EGT did not increase several seconds after controlling the ignition.

Modifications have been made to improve engine protection. First, to prevent overheating, it is now impossible for the pilot on the ground to order ignition before reaching a minimum value of N2. If the EGT threshold, which is a function of the N2, is exceeded, the ECU is no longer content to warn the pilot but, still on the ground, interrupts the starting. Second, the previous software does not have logic for "Stall Start". From now on, if the pressure PS3 (combustion chamber inlet pressure) drops and the acceleration of the N2 falls below a threshold, the ECU interrupts the start. Third, the detection of Rollback is now more sensitive. It is active if the N2 diet drops below 54% instead of 50%. We can see that the starting of an airplane engine is complex. Airlines are particularly interested in preventing operational problems when starting their aircraft engines. Indeed, starting problems cause delays and cancellations of flights at a very critical moment since the plane is grounded while it was ready to leave with all the passengers on board. In case of startup problem, it is then necessary to undertake troubleshooting actions (known as "troubleshooting" in English). For this, tests are performed to locate the faulty element that prevents startup. Given the large number of possible causes, the identification of the failure is often delicate and is to be repeated at each incident at startup.

SUMMARY OF THE INVENTION

To overcome the drawbacks listed above, the present invention relates to a method of monitoring the health status of LRU equipment (for "Line Replaceable Unit") involved in the starting capacity of a turbojet engine. This process has two missions: - detect and locate anomalies

(diagnostic) to minimize delays by immediately targeting maintenance actions on failed systems, without wasting time in finding the source of the failure, Anticipate breakdowns (prognosis) in order to avoid delays and cancellations of flights for non-starting or abnormal starting.

The proposed process has a real advantage for airlines because, in addition to increasing the availability of the aircraft, it contributes to the satisfaction of their customers by limiting delays and cancellation of flights.

The subject of the invention is therefore a method for monitoring the state of health of the engine modules and the equipment involved in the starting capacity of an aircraft engine, comprising:

the measurement acquisition of the parameters of the engine and the aircraft, said parameters affecting the starting capacity of the engine, from the measurements acquired, the extraction of specific indicators chosen for their representativity of the state of health start-up capacity, - the standardization of these indicators to put them in standard conditions, ie indicators in which the influence of context variables has been removed to keep only the influence of damage to the aircraft, the engine and its equipment, the detection of anomalies and the location of these anomalies thanks to statistical analysis tools and to the experts' knowledge of the operation of the aircraft engine, in which the indicators, thanks to the expertise of the users, can be chosen in particular from the following indicators: starter air supply pressure, opening time of the starter valve, value of the maximum acceleration of the compressor high pressure, - time to reach the maximum acceleration of the high-pressure compressor,

- time of the first startup phase,

- ignition time of the engine,

- time of the second starting phase, - closing time of the starter valve,

- time of the third phase of startup,

- maximum gradient of the temperature of the exhaust gas, - average gradient of the temperature of the exhaust gas,

- maximum speed before deceleration,

- engine stopping time.

The method may further include storing, after flight, standard indicator trends to provide an estimate of the lifetime of at least one of said engine and equipment modules.

The location of the anomalies can notably be detected from the failures chosen from the following breakdowns: - no flow of the hydromechanical regulator or HMU, little flow of the hydro-mechanical regulator, - too much flow of the hydromechanical regulator, too much flow of the hydromechanical regulator,

- the "backdriving" state of the starter, - the starter shaft break during the starting of the engine,

an oil leakage from the starter,

- a definite degree of wear on the bearings, blades or sprockets, - no spark at the candles when

1 'ignition,

- a breakdown of the candle relay,

- refusal to open the service valve,

- refusal to close the service valve, - slow opening of the service valve,

- slow closing of the SAV valve, poor position of a variable geometry element,

- slight cockroaching of the injectors, - clogging of the injectors, insufficient flow on ignition of the HP fuel pump,

a degree of internal wear of the gearbox; an absence of pressure to the auxiliary turbine; a low pressure to the auxiliary turbine,

a mechanical obstacle in the low-pressure compressor; insufficient performance of the high-pressure compressor; a decrease in the efficiency of the main fuel pump;

a too strong resisting torque in the chain of the gearbox / radial shaft of the high pressure rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other advantages and particularities will appear on reading the following description, given by way of non-limiting example, accompanied by the appended drawings among which:

FIG. 1 is a diagram illustrating the process implemented by the monitoring method according to the invention,

FIG. 2 is a graph showing the amplitude of a signal from a sensor, as a function of time, before and after filtering, FIG. 3 is a diagram illustrating the construction of indicators useful for the present invention. DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

The monitoring system according to the invention receives as input the measurements taken by the detectors as well as the parameters of the engine (or engines). It follows, according to the data entered, the state of deterioration of all the equipment and the engine involved in the start-up phase for the purposes of maintenance assistance. The system outputs an estimate of the state of health of the equipment and the engine, a prognosis of their remaining life if a degradation is detected and a degree of confidence in the decision taken.

Figure 1 is a diagram illustrating the process implemented by the monitoring system according to the invention.

In what follows, we will present the functional architecture of the algorithm.

1- Measurement Acquisitions The first step of the algorithm is the acquisition of information that will allow the estimation of the health of the engine modules and its equipment involved in the ability to start. The input data of this phase can be the sensor signals (such as temperatures, pressures, regimes, ...) or the discrete ones giving the threshold crossing information (such as the switch (or switch) of a valve, confirmation of ignition, obtaining the Cut Out regime) or information on the Startup configuration (such as activation of automatic mode, position of candle control). In general, all measurable information can serve as input data.

Table 1 gives an example of the measures to be acquired:

Table 1

1.1- Measurement acquisition tools

Regarding the validity of the input database, only the entry database is currently checked, the errors occurring during the calculations being considered non-existent. An oversampling operation provides a time base (and an index base) common to all data, allowing for more reliable processing.

In the context of this algorithm, it is considered that all the data present in the box will be acquired at the sampling frequency maximum of the FADEC, ie all HTRs, with 1 HTR = 15 milliseconds.

A data filtering step is necessary to reduce the acquisition noise of some data and thus limit the detection errors and increase the accuracy as shown in Figure 2. This figure represents the amplitude A of a signal from a sensor, as a function of time t, before filtering (curve 1) and after filtering (curve 2). The data that requires this operation are: HP Engine Speed, EGT Temperature, and HP PS3 Compressor Output Pressure. The filter used is a generic tool. The settings of the filter order and cutoff frequency are customized for each data. They were defined in the study of the smoothing tool according to the need.

The use of the derivative of certain signals is necessary for the detection of evolution in the signals. The data requiring this operation are as follows: HP Engine Speed, HP Compressor Output Pressure, EGT Temperature. The derived vector must be equivalent in size to the original vector. In addition, the processing must take into account the offset produced by the derivation operation, by copying the first value of the derived vector into the first position.

1.2- Recording of measurements

The raw database as well as the extraction and estimation results are saved. Non-determinable measures (by example: the time t2 in the case of an aborted start before closing the valve) are noted "NaN" for "Not a Number".

The output data are signals, filtered or not, derived or not, which will allow the extraction of the indicators. 2- Extraction of the indicators

The input data specified here is the output data of the "Acquisition of Measurements" part.

The output data are indicators that will be used to evaluate the health status of the engine. These indicators have been defined with the experts of the engine behavior so as to be able to detect the different degradations that can prevent starting. Each indicator is significant of the state of health of one or more modules of the engine and its equipment.

Table 2 below gives a non-exhaustive list of indicators as output data.

Table 2

Indicators provide the following information (proposed thresholds for defining indicators are given as an example):

• II - The air supply pressure:

It gives the power to the starter. The starter's torque is therefore linked to this value. It is used to detect APU problems but also to prevent starter shaft breaks. Indeed, pressure oscillations cause jolts at the level of the tree, which then gets tired more quickly.

• 12 - The time to overcome the margin of effort when opening the service valve:

It can be defined between the opening order and the moment when the position sensor changes to True. It detects air supply pressure problems or opening start valve. • 13 and 14 - The coordinate point of the maximum motor acceleration: This moment occurs at the start of the start and is used to detect air supply pressure or valve opening problems.

• 15 - The time "tl" of the start phase: Defined for example from 0 to 20% of the maximum speed of Co HP, this time is significant of the phase before ignition. It is therefore used to detect air pressure, starter valve, starter and HP compressor problems. • 16 - The ignition time:

It can be defined between the injection of fuel and the detection of the elevation of pressure in the chamber or between the injection and the rupture of the slope of the Co HP regime. This time monitors the state of health of the candles and injectors.

• 17 - The time "t2" of the start phase:

Defined for example by 30% of the HP speed and the Cut Out, this time corresponds to the phase where the starter and the combustion participate in the acceleration of the engine. It thus detects air supply, starter, HP compressor, variable geometry and fuel system problems such as the hydromechanical regulator or HMU (for "HydroMechanical Unit").

• 18 - The closing time of the service valve: Defined between the moment when the N2 reaches the Cut Out speed and the "closed" indication of the service valve. It detects problems of valve closing.

• 19 - The time "t3" of the start phase: Defined from the Cut Out at an idle speed (for example 98% of the minimum idle), this phase corresponds to the end of the start. At the Cut Out, the starter disconnects and no longer participates in the motor drive. It is used to detect fuel system and HP compressor problems. • IIP and 111 - Temperature gradients:

The temperature of the exhaust gas depends on the fuel / air ratio. At a given speed, the airflow is constant. Therefore, if we decrease the fuel flow the EGT will be lower and conversely if we increase the flow the EGT will be higher. If the fuel flow is really too high, the engine will not work properly and the airflow will be lower. The temperature then flies.

• 112 - Maximum speed before deceleration: This indicator shows which engine speed has had a problem that caused it to stagnate or decelerate.

• 113 - The engine stopping time:

Defined between the moment when the driver gives the order to shut down the engine and a low threshold on the HP speed (example: 5% or 2%), this time is used to estimate the resistance torque of the HP compressor.

Other indicators, defined for the monitoring of other functions than the ability to start can nevertheless be used for locating and predicting incidents at startup. Here is an example of new indicators:

• The HPSOV opening HP regime: Allows you to monitor the performance of the main fuel pump. This indicator is especially useful to guarantee the restart in flight but a degraded pump can also prevent the ground start. Reference may be made to this subject in the French patent application filed under the registration number 07 08099 and entitled "Monitoring of a high-pressure pump in a fuel supply circuit of a turbomachine".

• Starter vibration via the AGB sensor The accelerometer will give indications on the power transmission (AGB, TGB) but also on the vibrations of the starter. They make it possible to detect internal deteriorations (loss of blade, bearing wear, damaged gears, clutch wear). • Oil consumption

In shared lubrication, starter oil leakage results in engine oil leakage. The monitoring of the engine oil consumption thus makes it possible to detect a starter sealing problem, in addition to the engine oil problems.

• The position of variable geometries

Detects variable geometry problems by monitoring them throughout the flight. For example, a bad VSV position at startup can cause a warm start.

• The temperatures of the EGT probes

Used to detect injector problems. In case of coking, the temperature distribution will no longer be homogeneous on the four probes. The probe in front of the coked injector will be colder than usual and the other three a little warmer.

The majority of Ii indicators are sensitive to surrounding parameters such as outdoor temperature, oil temperature or external pressure. For better detection, it is therefore useful to standardize these indicators, that is to say, put them in standard conditions.

Normalizations are made using models that can be physical in nature. A physical model of forecast used is based on the relative supply pressure. There is also an abacus, established for the turbojet engine CFM56-5C, giving depending on the pressure and the ambient temperature and the degree of wear, the absolute pressures and temperatures expected at the APU output. The other models are of a statistical nature. They are obtained by regression of the indicators according to other indicators and environmental parameters:

M_PAStarD: starter supply pressure, m_Pamb: ambient pressure, m Tamb: OAT ambient temperature

(for "Outside Air Temperature"), m_dToil_dem: oil temperature at startup.

2.1 Standardization of indicators: Standardization is used to compare flight after flight indicators under the same conditions.

A standardized indicator is defined as a difference, called a residual, between the actual measurements of these indicators and their estimates using a model. The standardized indicator Ii will subsequently be noted.

The method of determining the indicators includes the following particularities: the indicators Motor deceleration rate and Maximum speed before deceleration do not undergo any modification with respect to the input data. All output data is saved.

3- Detection of anomalies and localization

The input data specified here are the output data of the "Extraction of Indicators" section. This input data is the information to judge the state of health of the engine and its equipment.

The output data are: • the detection state,

• the confidence of the detection,

• The probability of failure of each device (location).

The characteristics of the output data are given by the generic FDI tool for "Failure Detection and Identification ". One can refer to this subject to the French patent application filed under the registration number 08 58609 and entitled "Identification of failure in an aircraft engine". Table 3 below shows the main failures monitored by the monitoring algorithm. These degradations are the most frequent incidents that impact the starting capacity of a turbojet engine.

Table 3 Failure detection / localization uses the generic FDI tool. The location of the failures is based on the matrix below, defined with experts of the motor behavior. This matrix makes it possible to make the link between the indicators and the possible impairments. It gives the signatures of each monitored failure. As an example we could obtain the following matrix on the first 10 indicators and the first 15 failures:

Table 4

The signs in Table 4 represent an estimate of the normalized indicator i in case of failure j. 0 means that the indicator is not affected by this degradation. The sign "+" (respectively "-") means that the degradation makes the indicator Nominalized is greater (respectively lower) than its expected value.

The result produced by the "Motor deceleration rate" indicator is used to confirm cases of starter starter failure or starter failure.

All data is saved.

4- Decision and Prognosis The input data specified here are the output data of the "Anomaly Detection and Localization" section.

The output data are the specified data: • the rate of change of this probability,

• the prognosis of the estimated remaining life time,

• the accuracy of the prognosis (99% confidence interval).

The decision tool used must return the specified data as output data. The failure is confirmed when one or more decision thresholds are reached.

5-Example Application of the Invention to a Turbojet In this application example, we will consider URLs (Replaceable Units Online called "Line Replaceable Units" or LRU in English) likely to contribute to the new start of a turbojet engine. Table 5, below, contains a number of URLs. Other URLs or engine modules could contribute to non-startup, but they are not included in this table. This is the case for the main fuel pump, local loops and the AGB-Core HP kinematics (question: how can you translate HP core into French?). However, the causes of non-start-up shown in Table 5 against the selected URLs represent approximately 80% of non-start-up occurrences observed in service.

Table 5

Some of these failures can be anticipated by warning signs or firstfruits. These are shown in Table 6. As for the others it is not possible to detect them before the occurrence of non-starting.

* Very little effect on the performance and indicators envisaged below.

Table 6

Indicators make it possible to detect the beginnings of non-start-up or, if there are no first steps detectable by these indicators, to locate the causes of non-actual start-up.

• II - Air supply pressure:

It gives the power to the starter. The starter's torque is therefore linked to this value. She is used to detect APU problems but also to prevent starter shaft breaks. Indeed, pressure oscillations cause jolts at the level of the tree, which then gets tired more quickly.

• 12 - Time to overcome the margin of effort when opening the SAV valve:

It can be defined between the opening order and the moment when the position sensor changes to True. It detects problems of air supply pressure or opening of the starter valve.

• 13 and 14 - Coordinate point of maximum motor acceleration:

This moment occurs at the start of the start and is used to detect air supply pressure or valve opening problems.

• 15 - Duration of the "tl" start phase, called the autorotation time:

Defined for example from 0 to 20% of the maximum speed of Co HP, this duration is significant of the phase before ignition. It is therefore used to detect air pressure, starter valve, starter and torque problems in the starter motor - AGB - HP compressor. However, the only significant resisting torque is that of AGB. The variation of the autorotation time "tl" does not make it possible to estimate the torque or the performance of the compressor, but that of the AGB. of the Compressor operating variations are not discernible before ignition. The temperature "flies" but also a CHP pump (high pressure pump) can occur.

• 16 - Ignition time:

It can be defined as the time between the injection of fuel and the detection of the elevation of pressure in the chamber or between the injection and the rupture of the slope of the Co HP regime. This time monitors the state of health of the candles and injectors. However, this time may be disrupted by the presence of air in the fuel system, which is encountered in particular at the first engine bench, the first aircraft, after the exchange of a fuel URL, or even after a stop very prolonged engine (destocking).

• 17 - Duration of the "t2" start phase: Defined for example by 30% of the HP speed and the "Cut Out" (starter release), this duration corresponds to the phase in which the starter and combustion participate in the engine acceleration. It thus makes it possible to detect air supply, starter, HP compressor, variable geometry and fuel system problems such as the HMU (hydromechanical regulator).

• 18 - Close time of the service valve: Defined by the time between the moment when the valve

N2 reached the "Cut Out" regime and the indication "closed" of the service valve. It allows to detect problems of closing of valve SAV.

• 19 - Duration of the "t3" start phase: Defined by the time between the "Cut Out" and the attainment of an under-idle speed (for example 98% of the minimum idle speed), this phase corresponds to the end of the start. At the "Cut Out", the starter disconnects and no longer participates in the motor drive. 19 is used to detect fuel system and HP compressor problems.

• IIP and 111 - Maximum and average temperature gradients: The exhaust gas temperature depends on the fuel / air ratio. At a given speed, the airflow is constant. Therefore, if we reduce the fuel flow the EGT will be lower and, conversely, if we increase the flow the EGT will be higher. If the fuel flow is really too high, the engine will not work properly and the airflow will be lower. The temperature "flies away" then.

• 112 - Engine stop time: Defined by the time between the moment when the pilot gives the order to shut down the engine and a low threshold on the HP speed (example: 5% or 2%), this time is used to estimate the resistance torque of the HP compressor.

The indicators are summarized in Table 7 below: Reference Indicators Meaning indicators

Starter air supply pressure

12 "Opening" time of the starter valve

13 Value of the maximum acceleration of the HP Co

14 Time to achieve HP Co's max acceleration

15 Duration ^1st start phase

16 Engine ignition time

17 Duration 2 ^nd start-up phase

18 Closing time of the start valve

19 Duration 3 ^rd startup phase

110 Maximum gradient of exhaust gas temperature

111 Average gradient of exhaust gas temperature

112 Engine stop time

Table 7

Figure 3 is a diagram illustrating the construction of the indicators. The x-axis represents the time T in seconds. Curve 11 shows the evolution of the speed N2 of the HP compressor. Curve 12 shows the evolution of the temperature of the exhaust gas (or EGT). The curve shows the evolution of the fuel flow sent to the injectors and controlled by the Fuel Metering Valve (FMV). Curve 14 shows the evolution of pressure PS3 (inlet pressure of the combustion chamber).

The phases t1, t2 and t3 defined above are shown in the diagram of FIG. 3. The ignition time tA is also indicated.

The following two tables relate to two uses of indicators. Table 8 relates to causes of non-starting with first fruits. Table 9 relates to causes of non-starting without first-fruits. A normalized indicator (called I'I, I '2, ... I' 12) is defined as a deviation, called a residual, between the actual measurements (II, 12, ... 112) of these indicators and their prediction using a model.

* at iso-temperature Table 8

Table 9

The signs in Tables 8 and 9 represent an evolution of the indicator I compared to the expected value in case of degradation. 0 means that the indicator is not affected by this degradation. The sign "+" (respectively "-") means that the degradation makes the indicator is superior

10 (respectively lower) than its predicted value.

Non-determinable measures (for example: time t2 in the case of an aborted start before closing the valve) are marked "NaN" for "Not a Number".

Claims

A method for monitoring the health status of engine modules and equipment involved in the starting capacity of an aircraft engine, comprising:

the acquisition of measurements of the parameters of the engine and of the aircraft, said parameters affecting the starting capacity of the engine; from the measurements acquired, the extraction of specific indicators chosen for their representativity of the state of health of start-up capacity,

- the standardization of these indicators to put them in standard conditions, that is to say indicators where the influence of the context variables has been removed in order to keep only the influence of the damage of the aircraft, the engine and its equipment, - the detection of anomalies and the location of these anomalies using statistical analysis tools and to the experts' knowledge of the operation of the aircraft engine, in which the said indicators are chosen from the following indicators: starter air supply pressure, start valve opening time, - value of the maximum acceleration of the high pressure compressor, time to reach the maximum acceleration of the high pressure compressor,

- time of the first startup phase,

- ignition time of the engine, - time of the second starting phase, closing time of the starter valve,

- time of the third phase of startup,

- maximum gradient of exhaust gas temperature,

- average gradient of the temperature of the exhaust gases,

- maximum speed before deceleration,

- engine stopping time.

The method of claim 1, further comprising storing, on a flight-by-flight basis, trends of the standard indicators to provide an estimate of the lifetime of at least one of said engine and equipment modules.

3. Method according to one of claims 1 or 2, wherein the location of the anomalies is detected from failures that may have an impact on the ability to start and selected from the following failures:

no flow of the hydromechanical regulator or HMU, little flow of the hydromechanical regulator, too much flow of the hydromechanical regulator, too much flow of the hydromechanical regulator, - the "backdriving" state of the starter,

- starter shaft breakage during engine start,

an oil leakage from the starter,

- a definite degree of wear on bearings, vanes or sprockets, no spark at spark plugs during ignition

- a breakdown of the candle relay,

- a refusal to open the service valve, - a refusal to close the service valve,

- slow opening of the service valve,

- slow closing of the SAV valve, bad position of an element with variable geometry, - slight cockdefaction of the injectors,

- clogging of the injectors, insufficient flow on ignition of the HP fuel pump,

a degree of internal wear of the gearbox, a lack of pressure at the auxiliary turbine, a low pressure at the auxiliary turbine, a mechanical obstacle in the low pressure compressor, insufficient performance of the high pressure compressor,