Method for monitoring the health of an aircraft engine

Abstract

Methods for monitoring engine health of an aircraft having a first engine and a second engine are provided. In one example, the method includes obtaining a first turbine gas temperature of the first engine and a second engine turbine gas temperature of the second engine from a first flight. The first turbine gas temperature and the second turbine gas temperature are correlated to one another to define a first value. The first value is compared to a dataset to monitor the engine health.

Description

Technical Field

[0001] The technical field generally relates to engines, and more specifically to a method for monitoring the engine health status of a multi-engine aircraft. Background Technology

[0002] Engines such as gas turbines are used to generate thrust for vehicles such as aircraft. Monitoring engine health during operation is crucial for troubleshooting potential damage and / or changes in engine performance. Accurate monitoring of engine health helps extend the overall lifespan of the engine and improve its efficiency. Engine health can be determined by monitoring engine parameters. By monitoring changes in engine parameters throughout its lifespan, potential engine health problems and / or damage can be effectively addressed and / or completely avoided.

[0003] Current methods for monitoring aircraft engine health include observing engine parameters such as turbine gas temperature (TGT) and monitoring how this parameter changes during engine operation. In one example, TGT data corresponding to the engine is obtained for several flights. The data can be standardized to attempt to correct for various conditions. This data is then arranged chronologically to determine if any changes occur in the TGT. A sudden increase or decrease in TGT might, for example, indicate a change in engine health. Unfortunately, even with attempts to correct for various conditions, external factors that cause variations between flights, such as engine idling time, can introduce significant noise into the arranged data, making it difficult to accurately determine engine health.

[0004] Therefore, it is desirable to provide a method for monitoring the engine health of an aircraft with multiple engines to address one or more of the aforementioned problems. Furthermore, other desirable features and characteristics of the various embodiments described herein will become apparent from the following detailed description taken in conjunction with the accompanying drawings and background information, and the appended claims. Summary of the Invention

[0005] This document provides various non-limiting embodiments of a method for monitoring the engine health of an aircraft having a first engine and a second engine.

[0006] In a first non-limiting embodiment, the method includes, but is not limited to, obtaining a first turbine exhaust temperature of a first engine and a second turbine exhaust temperature of a second engine from a first flight. The method further includes, but is not limited to, correlating the first turbine exhaust temperature and the second turbine exhaust temperature with each other to define a first value. The method further includes, but is not limited to, comparing the first value with a dataset to monitor engine health.

[0007] In another non-limiting embodiment, the method includes, but is not limited to, obtaining a first turbine exhaust temperature of the first engine and a second turbine exhaust temperature of the second engine from a first flight. The method further includes, but is not limited to, obtaining a third turbine exhaust temperature of the first engine and a fourth turbine exhaust temperature of the second engine from a second flight. The method further includes, but is not limited to, correlating the first and second turbine exhaust temperatures with each other to define a first value. The method further includes, but is not limited to, correlating the third and fourth turbine exhaust temperatures with each other to define a second value. The method further includes, but is not limited to, comparing the first and second values ​​to monitor engine health. Attached Figure Description

[0008] In the following description, various embodiments will be illustrated with reference to the accompanying drawings, in which similar reference numerals denote similar elements, and wherein:

[0009] Figure 1 A top view of an aircraft having multiple engines and arranged on a runway according to an exemplary embodiment is shown;

[0010] Figure 2 A perspective side view of an aircraft having multiple engines and arranged on a runway according to an exemplary embodiment is shown;

[0011] Figure 3 A dataset of standardized turbine gas temperatures for multiple engines according to an exemplary embodiment is shown;

[0012] Figure 4 A dataset of multiple values ​​associated with the turbine gas temperature of multiple engines and a moving average of the offsets are shown according to an exemplary embodiment;

[0013] Figure 5 A block diagram is shown of a method for monitoring the engine health of an aircraft having a first engine and a second engine, according to an exemplary embodiment.

[0014] Figure 6 A block diagram is shown of a method for monitoring the engine health of an aircraft having a first engine and a second engine, according to an exemplary embodiment; and

[0015] Figure 7 A block diagram of an engine electronic control unit according to an exemplary embodiment is shown. Detailed Implementation

[0016] The following detailed description is exemplary in nature only and is not intended to limit the various implementations or their application and use. Furthermore, it is not intended to be bound by any theories presented in the preceding background or the following detailed description.

[0017] Various embodiments contemplated herein relate to methods for monitoring the engine health of an aircraft having a first engine and a second engine. Exemplary embodiments taught herein specify obtaining a first turbine exhaust temperature of the first engine and a second turbine exhaust temperature of the second engine during a first flight. In an exemplary embodiment, the first and second turbine exhaust temperatures are obtained during takeoff of the aircraft from the runway. Advantageously, this provides consistent engine conditions for obtaining the first and second turbine exhaust temperatures. In an exemplary embodiment, the first and second turbine exhaust temperatures are obtained under a first set of environmental conditions.

[0018] The first turbine gas temperature and the second turbine gas temperature are correlated with each other to define a first value. In an exemplary embodiment, correlating the first and second turbine gas temperatures includes: standardizing the first and second turbine gas temperatures using a first set of environmental conditions to define a first standardized turbine gas temperature and a second standardized turbine gas temperature, respectively. Next, the difference between the first standardized turbine gas temperature and the second standardized turbine gas temperature is determined to define the first value. The first value is compared with a dataset to monitor engine health.

[0019] In an exemplary embodiment, it is advantageous to reduce the variation in turbine gas temperature between flights due to operational and / or environmental conditions by correlating the first turbine gas temperature and the second turbine gas temperature with each other to define a first value and comparing this first value with a dataset, and to monitor engine health more accurately and effectively. Without being theoretically limited, it is believed that this is because the first and second engines typically operate in a similar manner before takeoff, and therefore all engines of the aircraft are subjected to the effects of each engine's operating conditions on the turbine gas temperature in a substantially similar manner.

[0020] Figure 1-2Top and perspective views of an aircraft 10 according to an exemplary embodiment, including propulsion systems 11 and 13, each including engines 12 and 14, are shown. As shown, the aircraft 10 is positioned on runway 16. Although the aircraft 10 is shown as having two engines 12 and 14, it should be understood that various alternative embodiments of the aircraft 10 may include an aircraft 10 having more than two engines and / or more than two propulsion systems. The aircraft 10 includes a fuselage 18 that serves as the main body of the aircraft 10, supporting wings 20 and 22. Depending on the design of the aircraft 10, engines 12 and 14 may be attached to the fuselage 14, or alternatively, to wings 20 and 22. Landing gears 70 and 72 include a nose landing gear 70 of the aircraft 10, located below the nose portion of the fuselage 18, having one or more wheels 24, and main landing gears 72 of the aircraft 10, located below wings 20 and 22, having wheels 26 and 28, respectively.

[0021] As shown in the figure, engines 12 and 14 are gas turbine engines. In some embodiments, the gas turbine engine may include a turbojet engine, etc. In an exemplary embodiment, the turbojet engine operates by compressing air using an intake fan and compressor blades rotating at operating speed. Fuel is then mixed with the compressed air. The fuel and compressed air mixture then enters the combustion chamber of the turbojet engine, where it is ignited, thereby increasing the temperature and pressure of the combustion chamber. The high-temperature, high-pressure mixture of air and combustion gases then passes through a turbine (which drives the compressor blades) and exits the turbojet engine. After exiting the turbojet engine, the high-temperature, high-pressure mixture is discharged by the propulsion system through nozzles at the rear end of the propulsion system to generate thrust and an exhaust plume (indicated by single arrows 30 and 32).

[0022] Aircraft 10 includes electronic systems 58. Electronic systems 58 include various control systems and devices, including a flight management system, memory storage device 38, engine electronic control system 74, and other systems, including one or more processors such as general-purpose processors, content-addressable memory, digital signal processors, application-specific integrated circuits, field-programmable gate arrays, any suitable programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination designed to perform various aircraft functions. Furthermore, the various systems of electronic systems 58 may include one or more displays that communicate with the processors. The display can be any of a number of known displays adapted to present text, graphics, and / or icon information in a format viewable by the pilot, crew, and / or any other authorized person. Furthermore, the various systems of electronic systems 58 can communicate with one or more other systems, or operate autonomously independent of other systems.

[0023] In an exemplary embodiment, the engine electronic controller system 49 includes a pair of engine electronic controllers 76, each communicating with a corresponding engine 12 or 14. A throttle quadrant assembly (TQA) 80 and / or an automatic thrust controller 82 communicate with the engine electronic controllers 76 to provide engine thrust commands 84 and 86, respectively.

[0024] Figure 7 An exemplary embodiment of an engine electronic controller 76 suitable for use with engines 12 and 14 is shown. The engine electronic controller 76 includes modules for performing engine electronic controller (EEC) functions. The engine electronic controller 76 includes, for example, a processor 88, an engine sensor input-output interface 90, and engine valve actuator hardware 92. The processor 88, engine sensor input-output interface 90, and engine valve actuator hardware 92 are used when performing EEC functions.

[0025] The engine sensor input-output interface 92 receives data 66 from various engine subsystems (not shown) and provides it to various sensors 68, which may include, for example, fluid flow sensors, temperature sensors, speed sensors, valve position sensors, etc. As will be discussed in further detail below, the temperature sensors include a first sensor 34 associated with engine 12 and a second sensor 36 associated with engine 14. Sensors 68 generate sensor data output signals 96, which are provided to processor 88.

[0026] As part of the EEC function, processor 88 processes data 98 ​​from various aircraft systems (e.g., engine thrust commands 84 and 86 from throttle quadrant assembly (TQA) 80 and / or automatic thrust controller 82) and sensor data output signals 96 to generate engine valve control signals 100, which are provided to engine valve actuator hardware 92 to control the corresponding engines 12, 14 of aircraft 10. Processor 88 also provides data 98 ​​from other aircraft systems (including, for example, turbine gas temperature (TGT) of engines 12, 14) to electronic system 58, as described in further detail below.

[0027] Specifically and reference Figure 1 and Figure 7Each engine 12, 14 includes corresponding sensors 34, 36 that measure the turbine exhaust temperature (TGT) of the engine 12, 14. In an exemplary embodiment, the TGTs of engines 12, 14 are the temperatures of the exhaust gases 30, 32 of engines 12, 14, respectively. Sensors 34 and 36 are, for example, thermocouples. In an exemplary embodiment, the aircraft 10 includes a memory storage device 38 that receives data corresponding to the TGT from sensors 34 and 36, respectively.

[0028] The TGT of engines 12 and 14 is obtained from flight and / or during flight (also referred to herein as “first flight”). As used herein, the term “flight” refers to any time from boarding to disembarking when at least one of engines 12 and 14 is running, including taxiing, takeoff, en route, and landing. In an exemplary embodiment, the TGT is obtained from flight under a set of environmental conditions. This set of environmental conditions includes, for example, ambient temperature and the rotor speeds of engines 12 and 14. Environmental conditions refer to conditions relating to and / or influenced by the atmosphere surrounding aircraft 10 at the time the TGT is obtained. For example, the rotor speeds of engines 12 and 14 are affected by the altitude at which aircraft 10 takes off from runway 16. In an exemplary embodiment, memory storage device 38 receives data corresponding to the environmental conditions.

[0029] In an exemplary embodiment, the TGT is obtained approximately during flight when the aircraft 10 takes off from runway 16. As used herein, the term "takeoff" refers to the time when wheels 26 and 28 leave runway 16 and / or the time when the aircraft begins to ascend. As used herein, the term "approximately" should be understood to include actual limits or tolerances for performing the specified mission or event. In an exemplary embodiment, a set of environmental conditions is obtained approximately during flight when the aircraft 10 takes off from runway 16 or during flight when the aircraft 10 takes off from runway 16.

[0030] In an exemplary embodiment, obtaining the Time GT includes retrieving data corresponding to the TGT and environmental conditions from the memory storage device 38 to an external memory storage device 40. For example, the external memory storage device 40 may be located at an airport, remote facility, etc., and includes one or more processors, such as a general-purpose processor, content-addressable memory, digital signal processor, application-specific integrated circuit, field-programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination designed to perform various memory storage functions. The TGT may be transmitted wirelessly via path 102 or alternatively via communication path 104, wherein communication path 104 may be removably coupled to the aircraft, for example, when the aircraft 10 is docked at an airport after flight.

[0031] Correlating TGTs to each other to define a value. In an exemplary embodiment, correlating TGTs is performed by electronic system 158. Electronic system 158 communicates with external memory storage device 40 and includes one or more processors operable to use algorithms to correlate, compare, evaluate, and / or analyze data. In an exemplary embodiment, correlating TGTs to each other includes standardizing TGTs using a set of environmental conditions to define a standardized TGT. For example, the TGT of engine 12 is standardized using ambient temperature and the rotor speed of engine 12, and the TGT of engine 14 is standardized using ambient temperature and the rotor speed of engine 14. This standardization includes mathematically adjusting the TGTs to the result that would be calculated at a "standard temperature" (e.g., a standard temperature of 273.15 K) and a "standard rotor speed" (e.g., the rotor speed at a standard temperature of 273.15 K and a standard pressure of 1 atm).

[0032] In an exemplary implementation, the process of relating TGTs to each other further includes defining values ​​using the difference between standardized TGTs. As used herein, the term "difference" refers to the mathematical difference between values. For example, the difference between 50 and 52 is 50–52 = -2, or 52–50 = 2.

[0033] In an exemplary embodiment, the process of obtaining and relating the TGTs of engines 12 and 14 described above is repeated for multiple flights, each flight having its own set of environmental conditions. For example, the TGTs of engines 12 and 14 are obtained from another flight (also referred to herein as "the second flight") under a set of environmental conditions. The TGTs of the second flight are correlated with each other to define a value. This includes normalizing the TGTs using a set of environmental conditions from the second flight and taking the difference between the normalized TGTs to define the corresponding value.

[0034] refer to Figure 1 and Figure 3 A dataset 42 of standardized turbine exhaust temperatures for engines 12 and 14, according to an exemplary embodiment, is shown. Dataset 42 includes multiple values ​​44 and 45. Each value 44, 45 corresponds to the TGT obtained from one of engines 12 or 14 for a specific flight under a set of environmental conditions for that flight. For example, line 46 includes standardized TGTs from engines 12 in flight time order from multiple flights. Similarly, line 48 includes standardized TGTs from engines 14 in flight time order from the same multiple flights. Thus, the multiple values ​​44 and 45 represent standardized TGTs obtained and associated from multiple flights for the two engines 12 and 14 respectively through the process described above, where each flight has its own set of environmental conditions.

[0035] Also refer to Figure 4The diagram illustrates a dataset 50 of multiple values ​​52 and a moving average 54 of the offset, according to an exemplary embodiment. The multiple values ​​52 correspond to multiple values ​​44 and 45. This means that each of the multiple values ​​52 is defined by taking the difference in normalized TGT of engines 12 and 14 for each of the multiple flights. Line 56 includes the multiple values ​​52 in flight time order.

[0036] Multiple values ​​52 are compared to monitor the engine health of engines 12 and 14. In an exemplary embodiment, the comparison is performed by electronic system 158.

[0037] In an exemplary embodiment, the comparison includes performing a statistical analysis on at least two of a plurality of values ​​52. As used herein, the phrase "statistical analysis" includes analyzing the values ​​being compared using one or more statistical methods. In an exemplary embodiment, the process of statistical analysis includes comparing a value from the most recent flight with other values ​​from the plurality of values ​​52 in the dataset 50. At least one of the values ​​from previous flights is used to generate an average, and then the value from the most recent flight is mathematically compared to the average. For example, if the three most recent values ​​arranged in chronological order of flight time are "5", "5", and "8", then the average (5+5+8) / 3 = 6 is mathematically compared to the value from the most recent flight, which is 8.

[0038] In an exemplary implementation, the average is a moving average. For example, if the three most recent values ​​arranged in flight time order are “5”, “5”, and “8”, then the two-point moving average is (5+8) / 2 = 6.5. Mathematically, this is compared to the value from the most recent flight, which is 8. If another value is collected, and the four most recent values ​​arranged in flight time order are “5”, “5”, “8”, and “8”, then the two-point moving average is (8+8) / 2 = 8. This is mathematically compared to the value from the most recent flight, which is 8. Thus, as a value from a new flight arrives at dataset 50, the moving average “moves” to the most recent value. A three-point moving average is the average of three values, a four-point moving average is the average of four values, and so on. In an exemplary implementation, this average has a seven-point moving average.

[0039] In an exemplary implementation, the average is a shifted moving average. For example, if the four most recent values ​​in flight time order are "5", "5", "8", and "8", then the 2-point moving average with a 2-point shift is (5+5) / 2 = 5. Mathematically, this is compared to the value 8 from the most recent flight. The shift controls how recent the value used in the average is. A 2-point moving average without a shift would, for example, be the average of the values ​​from the two most recent flights. Essentially, the shift pushes the calculation of the average back to the second most recent data. In the exemplary implementation, the average has a 2-point shift.

[0040] In an exemplary embodiment, the mathematical comparison involves calculating the difference between the value from the most recent flight and the average value to define the deviation. In an exemplary embodiment, this deviation is the sum of moving deviations. For example, if the five most recent values ​​in flight time order are “5”, “3”, “7”, “10”, and “10”, then the three-point moving average with a 2-point offset is (5+3+7) / 3 = 5, and the sum of the three-point moving deviations is (7-5)+(10-5)+(10-5) = 12. In an exemplary embodiment, the deviation is converted to sigma units. For example, standard deviation is used to convert the deviation to sigma units. If the five most recent values ​​in flight time order are “5”, “3”, “7”, “10”, and “10”, and the standard deviation of the engine’s standardized TGT is 2, then the 3-point moving average with a 2-point offset is (5+3+7) / 3 = 5, and the sum of the 3-point moving deviations is (7-5)+(10-5)+(10-5) = 12 = 12 / 2 sigma units = 6 sigma units. In an exemplary embodiment, the deviation is the sum of 4-point moving deviations.

[0041] In an exemplary embodiment, the comparison includes comparing a deviation to a threshold. For example, if the deviation is greater than the threshold, it indicates a problem with engine health. If the deviation is less than the threshold, it indicates no problem with engine health. In an exemplary embodiment, the threshold is 8 sigma units. In an exemplary embodiment, in response to comparing the deviation to the threshold, communication related to engine health is sent from electronic system 158 to user interface 60. For example, in response to a deviation greater than the threshold, a “warning,” “alarm,” or “notification” is sent from electronic system 158 to user interface 60.

[0042] Reference Figure 5A method 200 for monitoring the engine health of an aircraft having a first engine and a second engine, according to an exemplary embodiment, is provided. Method 200 includes obtaining (step 202) a first turbine exhaust temperature of the first engine and a second turbine exhaust temperature of the second engine from a first flight. The first turbine exhaust temperature and the second turbine exhaust temperature are correlated with each other (step 204) to define a first value. The first value is compared with a dataset to monitor engine health (step 206).

[0043] Reference Figure 6 A method 300 for monitoring the engine health of an aircraft having a first engine and a second engine, according to an exemplary embodiment, is provided. Method 300 includes obtaining (step 302) a first turbine exhaust temperature of the first engine and a second turbine exhaust temperature of the second engine from a first flight. Obtaining (step 304) a third turbine exhaust temperature of the first engine and a fourth turbine exhaust temperature of the second engine from a second flight. Correlating the first and second turbine exhaust temperatures to each other (step 306) to define a first value. Correlating (step 308) the third and fourth turbine exhaust temperatures to each other to define a second value. Method 300 further includes comparing (step 310) the first and second values ​​to monitor engine health.

[0044] Although at least one exemplary embodiment has been presented in the foregoing detailed description of this disclosure, it should be understood that numerous variations exist. It should also be understood that one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. The foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing exemplary embodiments of this disclosure. It should be understood that various changes can be made to the function and arrangement of the elements described in the exemplary embodiments without departing from the scope of this disclosure as set forth in the appended claims.

Claims

1. A method for monitoring the engine health status of an aircraft having a first engine and a second engine, the method comprising the steps of: The first turbine exhaust temperature of the first engine and the second turbine exhaust temperature of the second engine are obtained from the first flight. The first turbine gas temperature and the second turbine gas temperature are correlated with each other to define a first value; The first value is compared with the dataset to monitor engine health. as well as In response to comparing the first value with the dataset, communication related to the engine health status is sent from the electronic system to the user interface. The steps include obtaining the first turbine exhaust temperature of the first engine and the second turbine exhaust temperature of the second engine from the first flight under the first set of environmental conditions. The relevant steps include: using the first set of environmental conditions to standardize the first turbine gas temperature and the second turbine gas temperature to define the first standardized turbine gas temperature and the second standardized turbine gas temperature, respectively, and wherein the standardization includes mathematically adjusting the turbine gas temperature to the result that would be obtained if calculated at standard temperature and standard rotor speed.

2. The method according to claim 1, wherein, The first set of environmental conditions includes ambient temperature, the first rotor speed of the first engine, and the second rotor speed of the second engine.

3. The method according to claim 1, wherein, The steps include: during the takeoff of the aircraft from the runway, obtaining the first turbine gas temperature of the first engine and the second turbine gas temperature of the second engine from the first flight under the first set of environmental conditions.

4. The method according to claim 1, wherein, The relevant steps also include: calculating a first difference between the first standardized turbine gas temperature and the second standardized turbine gas temperature to define the first value.

5. The method according to claim 4, wherein, The dataset includes multiple values, each of which is defined by calculating the difference between the normalized turbine gas temperature of the first engine and the normalized turbine gas temperature of the second engine from a previous independent flight.

6. The method according to claim 5, wherein, The comparison step includes comparing the first value with the plurality of values ​​in the dataset in order of flight time.

7. The method according to claim 6, wherein, The comparison steps also include: Use at least two values ​​from the dataset to generate an average; and Mathematically compare the first value with the average value.

8. The method according to claim 7, wherein, The average value is a moving average, and wherein, as values ​​from new flights arrive in the dataset, the moving average is the average of multiple most recent values ​​arranged in flight time order.

9. The method according to claim 7, wherein, The average value is a moving average of the offset, wherein, as values ​​from new flights arrive in the dataset, the moving average of the offset is the average of a plurality of near-nearest values ​​arranged in flight time order, and the offset controls the degree of recentity of the values ​​used in the average value.

10. The method according to claim 9, wherein, In mathematical comparison, this includes: taking a second difference between the first value and the average value to define a first deviation.

11. The method according to claim 10, wherein, Mathematical comparison also includes comparing the first deviation with a threshold.

12. The method according to claim 9, wherein, The moving average of the offset has a 7-point moving average and a 2-point offset.

13. A method for monitoring the engine health status of an aircraft having a first engine and a second engine, the method comprising the steps of: The first turbine exhaust temperature of the first engine and the second turbine exhaust temperature of the second engine are obtained from the first flight. The third turbine exhaust temperature of the first engine and the fourth turbine exhaust temperature of the second engine are obtained from the second flight. The first turbine gas temperature and the second turbine gas temperature are correlated with each other to define a first value; The third turbine gas temperature and the fourth turbine gas temperature are correlated with each other to define a second value; The first value and the second value are compared to monitor the engine health status, and In response to monitoring the engine health status, communications related to the engine health status are sent from the electronic system to the user interface. Obtaining the first turbine exhaust temperature and the second turbine exhaust temperature includes: obtaining the first turbine exhaust temperature of the first engine and the second turbine exhaust temperature of the second engine from the first flight under a first set of environmental conditions, and obtaining the third turbine exhaust temperature and the fourth turbine exhaust temperature includes: obtaining the third turbine exhaust temperature of the first engine and the fourth turbine exhaust temperature of the second engine from the second flight under a second set of environmental conditions. The process of correlating the first turbine gas temperature and the second turbine gas temperature includes: using the first set of environmental conditions to standardize the first turbine gas temperature and the second turbine gas temperature to define a first standardized turbine gas temperature and a second standardized turbine gas temperature, respectively. The process of correlating the third turbine gas temperature and the fourth turbine gas temperature includes: using the second set of environmental conditions to standardize the third turbine gas temperature and the fourth turbine gas temperature to define a third standardized turbine gas temperature and a fourth standardized turbine gas temperature, respectively. The standardization includes mathematically adjusting the turbine gas temperature to the result that would be obtained if calculated at a standard temperature and a standard rotor speed.

14. The method according to claim 13, wherein, Correlating the first turbine gas temperature and the second turbine gas temperature to each other includes: calculating a first difference between the first standardized turbine gas temperature and the second standardized turbine gas temperature to define the first value, and wherein correlating the third turbine gas temperature and the fourth turbine gas temperature to each other includes: calculating a second difference between the third standardized turbine gas temperature and the fourth standardized turbine gas temperature to define the second value.

15. The method according to claim 14, wherein, The comparison step includes statistical analysis of the first value and the second value.

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