HK1202348B - Method and apparatus for detecting performance of an apu fuel assembly - Google Patents

Abstract

The present invention relates to a method for detecting performance of an APU fuel assembly, comprising: obtaining APU messages at multiple time points within a time period; obtaining running parameters of the APU fuel assembly according to the APU messages, the running parameters at least comprising starting time STA; calculating average value AVG and deviation index δ of the starting time STA within said time period; determining whether performance of the APU fuel assembly is in the stable phase, decline phase, or failure phase according to the deviation index δ.

Description

Method and device for detecting performance of fuel assembly of auxiliary power unit of airplane

Technical Field

The invention relates to a method for detecting performance of an aircraft component, in particular to a method for detecting performance of a fuel assembly of an aircraft auxiliary power unit.

Background

An Airborne Auxiliary Power Unit (AIrborne Autoliary Power Unit), called Auxiliary Power Unit APU for short, is a small turbine engine installed at the tail of an airplane. The main function of the APU is to provide power and air, and there are also a small number of APUs that can provide additional thrust to the aircraft. Specifically, the APU provides power to start the main engine before the aircraft takes off from the ground, so that ground electric and air source vehicles are not needed to start the aircraft. On the ground, the APU also provides power and compressed air to ensure lighting and air conditioning in the passenger cabin and the cockpit. When the airplane takes off, the APU can be used as a standby power supply. After the aircraft lands, the APU still supplies power for illumination and air conditioning. The function of the APU determines the stability of its operation directly related to the flight cost and quality of service of the aircraft.

The fuel assembly of the APU is an important part of the APU, and once the fuel assembly fails, the fuel assembly can directly cause the APU to stop, so that the airplane can not take off. In the prior art, an effective maintenance method is not provided for the fuel assembly of the APU, and only the maintenance can be carried out afterwards. This inevitably results in delays and increased maintenance costs for the aircraft.

Disclosure of Invention

In view of the above technical problems in the prior art, according to an aspect of the present invention, a method for detecting a fuel assembly of an APU of an aircraft auxiliary power unit is provided, including: acquiring APU messages on a plurality of time points in a time period; acquiring the operating parameters of the APU fuel assembly according to the APU message, wherein the operating parameters at least comprise starting time STA; calculating the standard deviation delta of the starting time STA in the time period; and determining that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period according to the standard deviation delta.

The method as described above, wherein the step of determining that the performance of the APU fuel assembly is in a stable period, a decline period, or a failure period comprises: determining that the performance of the APU fuel assembly is in a stable period in response to the standard deviation δ being less than a decay threshold; in response to the standard deviation δ being greater than the degradation threshold and less than a fault threshold, determining that the performance of the APU fuel assembly is in a degradation period; and determining that the performance of the APU fuel assembly is in a failure period in response to the standard deviation δ being greater than the failure threshold.

The method as described above, further comprising: determining the standard deviation of the APU fuel assembly during a stabilization period; wherein the fade threshold is about 2 times the standard deviation of the stationary phase and the fault threshold is about 3-4 times the stationary standard deviation.

The method as described above, wherein the period of time is 2-4 days.

The method as described above, wherein 5-10 APU messages are acquired within the time period.

The method as described above, further comprising: determining the starting time STA obtained from the next APU message_next(ii) a In response to STA_nextGreater than AVG + n delta or less than AVG-n delta, determining STA obtained according to next and APU message_next+1Whether greater than AVG + n δ or less than AVG-n δ; responding to the fact that the starting time STA obtained according to the APU message is continuously larger than AVG + n delta or continuously smaller than AVG-n delta and exceeds the preset alarm times Z, and sending out an alarm; wherein n is 2, 3, 4 or 5; z is 3, 4 or 5.

In the method, the average value AVG and the standard deviation delta of the starting time STA are recalculated in response to that the starting time STA obtained according to the APU message is smaller than AVG + n delta and larger than AVG-n delta.

According to the method, the average value AVG and the standard deviation delta of the STA are recalculated in response to that the starting time STA obtained according to the APU message is continuously larger than AVG + n delta or smaller than AVG-n delta and exceeds the preset alarm times Z.

The method as described above, wherein n is 2 or 3 and Z is 3.

The method as described above, further comprising: and determining that the starter of the APU works normally.

The method as described above, further comprising: determining that other parameters of the APU remain normal, including but not limited to: APU exhaust temperature EGT, induced pressure PT, air scoop blade angle IGV, and APU turbine efficiency NPA.

According to another aspect of the invention, a device for detecting the performance of a fuel assembly of an aircraft auxiliary power unit APU is provided, comprising: the message acquisition unit is used for acquiring APU messages at a plurality of time points in a time period; the parameter acquisition unit is used for acquiring the operating parameters of the APU fuel assembly according to the APU message, and the operating parameters at least comprise starting time STA; a calculating unit, configured to calculate a standard deviation δ of the start time STA in the time period; (ii) a And the performance detection unit is used for determining that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period according to the standard deviation delta.

According to another aspect of the invention, a device for detecting the performance of a fuel assembly of an aircraft auxiliary power unit APU is provided, comprising: a processor; and a memory coupled to the processor, storing computer readable code; the computer readable code running on the processor to perform the steps of: acquiring APU messages on a plurality of time points in a time period; acquiring the operating parameters of the APU fuel assembly according to the APU message, wherein the operating parameters at least comprise starting time STA; calculating the standard deviation delta of the starting time STA in the time period; and determining that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period according to the standard deviation delta.

Drawings

Preferred embodiments of the present invention will now be described in further detail with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic structural diagram of an aircraft APU according to one embodiment of the present invention;

FIG. 2 is a graph illustrating the statistical trends in APU startup time data changes caused by changes in the performance of the APU fuel assemblies;

FIG. 3 shows an example of an A13 message for airbus;

FIG. 4 illustrates a flow diagram of a method for detecting the performance of an APU fuel assembly, in accordance with one embodiment of the present invention;

FIG. 5 illustrates a flow chart of a method of detecting APU fuel assembly performance in accordance with another embodiment of the present invention;

FIG. 6 illustrates an example of APU fuel assembly performance variation, in accordance with one embodiment of the present invention; and

FIG. 7 is a schematic structural diagram of a detection device for detecting the performance of the fuel assembly of the APU according to one embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the following detailed description, reference is made to the accompanying drawings that form a part hereof and in which is shown by way of illustration specific embodiments of the application. In the drawings, like numerals describe substantially similar components throughout the different views. Various specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to practice the teachings of the present application. It is to be understood that other embodiments may be utilized and structural, logical or electrical changes may be made to the embodiments of the present application.

FIG. 1 shows a schematic structural diagram of an aircraft APU in accordance with one embodiment of the present invention. As shown, fig. 1 is a schematic structural diagram of an aircraft APU in accordance with one embodiment of the present invention. As shown, the aircraft APU generally includes a power section 100, a load section 200, and an accessory section 300. The power section 100 mainly includes a power compressor 110, a turbine assembly 120, an exhaust assembly 130, and the like. The load part 200 mainly includes a load compressor 210; the accessory portion 300 generally includes an accessory gearbox 310, a starter 320, and a generator 330, among other things. The power compressor 110 is used for providing high-pressure gas to the combustion chamber for combustion in the combustion chamber. The fuel train components of the APU provide fuel to the combustion chamber. The combustor generates high-temperature and high-pressure gas by burning fuel to push the turbine assembly 120, so that the turbine assembly 120 rotates. The air flow entering from the air inlet is divided into two flows, one flow enters the power compressor 110 and the turbine assembly 120 and is mainly used for driving the APU to rotate, and then the air flow is discharged through the exhaust assembly 130; and the other stream enters the load compressor 210, which is pressurized by the load compressor and is used exclusively to produce compressed air for use by the aircraft. The inlet of the air flow is provided with a flow regulating valve (inlet guide vane), and the opening of the valve (vane) is regulated in real time according to the requirement of the airplane on compressed air so as to control the amount of air entering the load compressor.

At the start of the APU, the starting system derives its power from the direct current system of the aircraft, supplying a 28V direct voltage to the battery BUS (BAT BUS) and, through the contactors, to the starter. The starter rotates and accelerates the rotor of the APU to reach the rotating speed at which the fuel oil and the ignition system can work, then the fuel oil is ignited and combusted, and the APU further accelerates. And when the rotating speed reaches 35% to 60% of the normal rotating speed of the APU, the starter is closed, and meanwhile, the APU continues accelerating to the normal working rotating speed. For example, for APS3200 type APU, when the rotating speed reaches 55% of the normal rotating speed of the APU, the starter is turned off; and for the GTCP131-9A type APU, when the rotating speed reaches 50% of the normal rotating speed of the APU, the starter is closed.

The inventors of the present application have discovered that the performance of the fuel assembly of the APU directly affects the start-up time of the APU. When the performance of the fuel assembly of the APU is reduced and the fuel supply of the combustion chamber is insufficient, the APU needs more time to accelerate to the normal working speed. As the operating time of the fuel assembly increases, its efficiency decreases gradually, and the fuel supply efficiency also decreases. When the fuel supply efficiency of the fuel assembly is reduced to a certain degree, the fuel assembly cannot accelerate the APU to the rotating speed of normal operation, namely, the fuel assembly fails.

The performance change of the APU fuel assembly follows a certain rule: the performance of the fuel assembly is stable in the early stage and the middle stage of use, and the performance is degraded in the later stage until the failure occurs. With the increase of the service time, the degradation index gradually increases due to the gradual degradation of the fuel assembly performance of the aircraft APU. When the decline index of the performance of the fuel assembly of the APU is stable, the performance of the fuel assembly of the APU is in a stable period; when the performance degradation of the fuel assembly of the APU is accelerated gradually, the performance of the fuel assembly of the APU enters a degradation period; when a certain threshold value is exceeded, the performance of the system enters a failure period, and a failure can occur at any time. When the fuel assembly of the APU enters the fault period, the use of the APU is influenced, and adverse consequences are generated on the service quality and the flight safety; and is easy to cause non-planned maintenance, resulting in flight delay and flight stop.

The performance of the fuel assemblies FCUs of the aircraft APUs can be characterized by the start time of the APUs. FIG. 2 is a graph of the statistical trends in the change in APU fuel assembly performance resulting in a change in the APU startup time data. As shown in FIG. 2, the variation range of the APU start time is small when the fuel assembly is in the stationary phase, and the APU start time is transitioned and dispersed when the fuel assembly of the APU is in the decline phase until the APU fails to start due to the fault. Also, as can be seen from fig. 2, the time from entering the decline period to the failure is short. Therefore, the detection of the degradation period of the fuel assembly is more important.

There is no means in the prior art to detect whether the performance of the APU fuel assembly enters the decline period. And certain embodiments of the present invention may implement such detection. The following benefits are achieved for the detection of the decline period: the probability of failure is still very low when the APU fuel assembly is in the decline period. If the airplane is selected to be overhauled at the moment, the flight safety and the service quality can be guaranteed. At the moment, the airline company can timely arrange the maintenance of the aircraft, so that the unscheduled maintenance is avoided, and the delay of the aircraft is reduced. And meanwhile, the waste of maintenance cost caused by maintenance according to a fixed time limit is avoided.

Various methods may be used to obtain the operating parameter of the start time STA. This data can be obtained, for example, by data stored in the aircraft black box FDR or the quick access recorder QAR.

The data can be conveniently acquired through a data system provided by an aircraft manufacturer, and ground real-time detection is realized. For example, both an Aircraft Condition Monitoring System (ACMS) System of an airbus and an Aircraft Health Monitor (AHM) System of boeing corporation can Monitor the operation data of an Aircraft in real time, and when a certain trigger Condition is met, a message containing a series of data information is automatically generated.

According to an embodiment of the present invention, the relevant operating data of the APU may be acquired by an aircraft data system (e.g., ACMS or AHM system) and embodied in the generated relevant message. Such message information can be transmitted to the ground through an Aircraft communication Addressing and Reporting System (ACARS air Communications Addressing and Reporting System) System, and further distributed to servers of different airlines. According to an embodiment of the present invention, the APU message may also be transmitted through a communication device or system of an aeronautical telecommunications Network (ATN Aviation telecommunications Network).

In fact, for the existing air data system, performance monitoring of the APU is an existing project, so that a corresponding APU message can be automatically generated and transmitted to the ground through ACARS or ATN. However, these monitored data are not used for the decay period detection of the APU performance. For example, the A13 message from airbus, or (APU MES/IDLE REPORT), or the APU message from Boeing is an example of such an APU message. In the following embodiments, a message a13 of airbus is taken as an example for explanation. The Boeing APU messages are processed similarly.

Fig. 3 shows an example of a13 message for airbus. As shown in the figure, the a13 message mainly includes 4 pieces of information, which are: the system comprises a header, APU resume information, operating parameters for starting an aircraft engine and APU starting parameters.

The header consists of CC and C1 sections and mainly comprises flight information of the airplane, a message generation section stage, a bleed valve state, total temperature (namely outside temperature) and other information. The APU resume information is composed of section E1 and includes APU serial number, running time, cycle and other information. The operation parameters for starting the aircraft engine consist of sections N1 to S3; wherein, N1 and S1 represent the operation condition when the first aircraft engine is started, N2 and S2 represent the operation condition when the second aircraft engine is started, and N3 and S3 represent the condition when the APU is slowed down after the APU finishes starting the engine. Wherein the data related to the fuel assembly performance is the start time STA.

As can be seen from fig. 3, the APU operating parameter, i.e., the start time STA, is contained in the existing message No. a 13. Therefore, the performance detection of the APU fuel assembly can be realized by using the data acquired by the message.

FIG. 4 is a flow diagram of a method for detecting the performance of an APU fuel assembly, in accordance with one embodiment of the present invention. As shown, in the detection method 400 for the performance of the APU fuel assembly, in step 410, the starting time STA of the aircraft APU fuel assembly at a certain time point is obtained.

According to one embodiment of the invention, the information required in step 410 may be obtained from an APU message, such as the A13 message. For example, an A13 message of the operation of the aircraft APU can be remotely acquired in real time from an international aviation telecommunication group SITA network control center and an ADCC network control center of a national aviation data communication company, and the A13 message of the operation state of the aircraft APU is decoded by a message decoder to acquire the required operation information of the fuel assembly of the aircraft APU.

In step 420, the previous M start times STA are obtained, and the mean AVG and the standard deviation δ are obtained. According to one embodiment of the present invention, M may take a value of 5 to 10.

In step 430, it is determined whether the standard deviation δ found in step 420 exceeds a fault threshold. And if the fault threshold value is exceeded, outputting a fault alarm.

If the determination in step 430 is negative, the process proceeds to step 440, and it is determined whether the standard deviation δ obtained in step 420 exceeds the degradation threshold. If the threshold value exceeds the decline threshold value, outputting a decline alarm; otherwise, returning to step 410, continuously acquiring the APU starting time STA of the next time point.

According to one embodiment of the invention, the fluctuation rate of the fuel assemblies of the APUs of the models in the stable period is firstly analyzed through empirical data, and then other threshold values are further determined by taking the fluctuation rate of the fuel assemblies in the stable period as a reference. For example, according to one embodiment of the present invention, the decline threshold is about 2 times the stationary phase trend and the failure phase threshold is 3-4 times the stationary phase trend.

This method of using the trend of data that is continuously updated over a period of time may be referred to as a moving window method. The size of the moving window, i.e. the number of points M that are included in the calculation range, is chosen depending on various factors, such as the interval of the measurement time, and the control strategy, etc. If the moving window is smaller, the fluctuation rate of the data is more easily influenced by normal fluctuation, so that excessive false alarm occurs, and the effect of the invention is influenced. If the moving window is too large, although the change trend is reflected more accurately, the timeliness of the invention is reduced, and the warning information cannot be sent out accurately in time. Therefore, the size of the moving window has an important influence on the present invention. According to one embodiment of the present invention, M is approximately 5 on the premise that 2-3 points are measured per day. According to another embodiment of the invention, M is about 10 on the premise that the measurement is less than or equal to 2 points per day.

According to one embodiment of the invention, in order to reduce false alarms and improve accuracy, if 2 recession alarms continuously occur, the performance of the fuel assembly of the APU is confirmed to enter a recession period; and when more than 2 fault alarms continuously occur, confirming that the performance of the fuel assembly of the APU enters a fault period.

FIG. 5 is a flow chart of a method of detecting the performance of an APU fuel assembly in accordance with another embodiment of the present invention. As shown, in the method 500 for detecting the performance of the fuel assembly of the APU, similar to the embodiment shown in FIG. 4, in step 410, the starting time STA of the fuel assembly of the aircraft APU at a certain operating time point is obtained.

In step 520, M start times STA before the time point of the sum of the high value counter and the low value counter are taken, and the mean AVG and the standard deviation δ are obtained. The mean and standard deviation of a certain number of points are obtained to set a variation range for determining the next point, but it is necessary to eliminate a value that may be a noise point. As will be described below, the high value counter is used to record deviation points that vary beyond a preset range, and these deviation points are not counted in the sample range of the mean and standard deviation calculations when the number of consecutive occurrences of deviation points does not reach the alarm number. According to one embodiment of the present invention, M may take a value of 5 to 10.

In step 530, a comparison is made as to whether the standard deviation δ determined in step 520 exceeds a fault threshold. And if the fault threshold value is exceeded, outputting a fault alarm.

If the determination in step 530 is no, the process proceeds to step 540, and it is compared whether the standard deviation δ obtained in step 520 exceeds the degradation threshold. And if the decline threshold value is exceeded, outputting a decline alarm.

When the determination in step 540 is no, the process proceeds to step 550, where the counter is reset to zero. This is because the deviation point is already disconnected by the previous determination, and to count the number of successive deviation points, the counter needs to be reset to zero and recounted. Such counters can be implemented in a variety of ways, both software and hardware.

In step 560, it is determined whether the APU start time STA at the next time point is greater than AVG + n δ or less than AVG-n δ. The value of n is determined by a control strategy, and when the value of n is higher, the control on the mutation point is looser, so that the false alarm can be reduced, but the risk of missing the alarm is caused; and when the value of n is lower, the control on the catastrophe point is stricter, thus preventing the report missing, but possibly facing the alarm with higher frequency. Generally, n is between 2 and 5. According to one embodiment of the invention, n has a value of 3.

When the determination of step 560 is yes, the counter value is + 1. In step 570, it is determined whether the counter value equals the predetermined number of alarms. When the judgment is no, return to step 550. And if so, indicating that the starting time STA of the APU continuously reaching the preset alarm number exceeds a preset normal fluctuation range, and sending out a jump alarm. Since a single transition may be caused by a variety of reasons, it is necessary to continue to alarm more than a certain number to eliminate false alarms. The value of the preset alarm number is related to the control strategy, and is generally 3-5.

At step 580, the counter is zeroed. This is because when the number of consecutive deviation points reaches the preset alarm number, the occurrence of the deviation points is not a contingency phenomenon and should not be excluded as noise. The counter is now zeroed and the next time the loop goes to step 520, the deviation points are retained and taken into account in the reference sample. After this step is completed, the process returns to step 510.

According to one embodiment of the invention, the information required in step 510 may be obtained in a manner similar to step 4100.

FIG. 6 is an example of APU fuel assembly performance variation, in accordance with one embodiment of the present invention. Wherein the fuel assembly of the APU is replaced in the solid line position of the figure. As shown in fig. 6, prior to changing the APU fuel assembly, the start time STA rises and the standard deviation of STA also rises (i.e., STA dispersion occurs). If the method is adopted, the increase of the STA deviation index such as the standard deviation can quickly trigger the alarm that the performance of the fuel assemblies of the APU is deteriorated and enters the decline period.

It is also noted that other parameters of the APU, other than the start time STA, including but not limited to: APU exhaust temperature EGT, induced pressure PT, air scoop blade angle IGV, and APU turbine efficiency. This is an important feature of APU fuel assembly failure.

It is also noted that APU starter failure behaves very similarly. Therefore, a distinction needs to be made from APU starter failure: although the standard deviation of the starting time STA is increased due to the faults of the starter of the APU, namely the STA is discrete, when the performance of the fuel assembly of the APU is deteriorated, the starting time STA is deteriorated more slowly, the standard deviation of the STA is increased and maintained at a certain level, and the duration of the phenomenon can reach more than 100 hours/50 starting times. The failure of the starter can only be started for 30-40 hours/10-15 times at most.

Moreover, while the performance of the APU fuel assembly deteriorates, other parameters besides STA remain good; however, because of the unstable supply, NPA and EGTP also gradually deteriorate, approaching their red line values. This feature may also assist in determining a failure of the APU fuel assembly.

FIG. 7 is a schematic structural diagram of a device for detecting the performance of the fuel assembly of the APU of the auxiliary power unit of the aircraft according to one embodiment of the invention. As shown in fig. 7, the apparatus for detecting the performance of the fuel assembly of the APU comprises: a message acquiring unit 701, configured to acquire an APU message in a time period; the message analysis unit 702 is used for analyzing the required APU fuel assembly operation data; and a performance detection unit 703, which determines that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period according to the fuel assembly operation data.

According to one embodiment of the invention, the device for detecting the performance of the fuel assembly of the auxiliary power unit APU of the airplane comprises the following components: a processor; and a memory coupled to the processor, storing computer readable code; the computer readable code running on the processor to perform the steps of: acquiring an APU message in a time period; analyzing the operation parameters of the APU fuel assembly according to the message, wherein the operation parameters comprise starting time STA; and determining that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period.

The degradation of the fuel assembly performance is not rapid, typically over 100 hours. According to the conventional fault elimination rules and sequences, the damage of the fuel assembly is difficult to find, the fault phenomenon is difficult to capture, and other parts are required to be replaced for many times to determine the fault of the fuel assembly FCU. The method and the device can ensure that maintenance personnel can accurately position the decline phenomenon of the performance of the fuel assembly of the APU of the airplane, avoid replacing other parts for many times, reduce the overstock of the aeronautical materials and reserve sufficient time for preparing spare parts. This is important to ensure that the aircraft is operating at its correct point, while also allowing more accurate control of inventory, and even achieving zero inventory.

The above embodiments are provided only for illustrating the present invention and not for limiting the present invention, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention, and therefore, all equivalent technical solutions should fall within the scope of the present invention.

Claims (13)

1. A method for detecting the performance of an APU fuel assembly of an auxiliary power unit of an airplane comprises the following steps:

acquiring APU messages on a plurality of time points in a time period;

acquiring the operating parameters of the APU fuel assembly according to the APU message, wherein the operating parameters at least comprise starting time STA;

calculating the standard deviation delta of the starting time STA in the time period; and

and determining that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period according to the standard deviation delta.

2. The method of claim 1 wherein the step of determining that the performance of the APU fuel assembly is in a stable period, a declining period, or a failure period comprises:

determining that the performance of the APU fuel assembly is in a stable period in response to the standard deviation δ being less than a decay threshold;

in response to the standard deviation δ being greater than the degradation threshold and less than a fault threshold, determining that the performance of the APU fuel assembly is in a degradation period; and

and determining that the performance of the APU fuel assembly is in a failure period in response to the standard deviation delta being greater than the failure threshold.

3. The method of claim 2, further comprising:

determining the standard deviation of the APU fuel assembly during a stabilization period;

wherein the fade threshold is about 2 times the standard deviation of the stationary phase and the fault threshold is about 3-4 times the stationary standard deviation.

4. The method of claim 1, wherein the period of time is 2-4 days.

5. The method of claim 1 wherein 5-10 APU messages are acquired during the time period.

6. The method of claim 1, further comprising:

determining the starting time STA obtained from the next APU message_next；

In response to STA_nextGreater than AVG + n delta or less than AVG-n delta, determining STA obtained according to next and APU message_next+1Whether greater than AVG + n δ or less than AVG-n δ; and

responding to the fact that the starting time STA obtained according to the APU message is continuously larger than AVG + n delta or continuously smaller than AVG-n delta and exceeds the preset alarm times Z, and sending out an alarm;

wherein n is 2, 3, 4 or 5; z is 3, 4 or 5.

7. The method of claim 6 wherein, in response to the start time STA derived from the APU message being less than AVG + n δ and greater than AVG-n δ, recalculating the mean AVG and standard deviation δ of the start time STA.

8. The method of claim 6 wherein the average AVG and standard deviation δ of the start time STA are recalculated in response to the start time STA derived from the APU message being continuously greater than AVG + n δ or less than AVG-n δ for more than a preset number of alarms Z.

9. The method of any one of claims 6-8, wherein n is 2 or 3 and Z is 3.

10. The method of claim 1, further comprising: and determining that the starter of the APU works normally.

11. The method of claim 1, further comprising: determining that other parameters of the APU remain normal, including but not limited to: APU exhaust temperature EGT, induced pressure PT, air scoop blade angle IGV, and APU turbine efficiency NPA.

12. An apparatus for detecting the performance of the fuel assembly of an aircraft Auxiliary Power Unit (APU), comprising:

the message acquisition unit is used for acquiring APU messages at a plurality of time points in a time period;

the parameter acquisition unit is used for acquiring the operating parameters of the APU fuel assembly according to the APU message, and the operating parameters at least comprise starting time STA;

a calculating unit, configured to calculate a standard deviation δ of the start time STA in the time period; and

and the performance detection unit is used for determining that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period according to the standard deviation delta.

13. An apparatus for detecting the performance of the fuel assembly of an aircraft Auxiliary Power Unit (APU), comprising:

a processor; and

a memory coupled to the processor, storing computer readable code;

the computer readable code running on the processor to perform the steps of:

acquiring APU messages on a plurality of time points in a time period;

acquiring the operating parameters of the APU fuel assembly according to the APU message, wherein the operating parameters at least comprise starting time STA;

calculating the standard deviation delta of the starting time STA in the time period; and

and determining that the performance of the APU fuel assembly is in a stable period, a decline period or a failure period according to the standard deviation delta.