Engine accessory on-condition maintenance decision-making method considering inherent characteristics and repair characteristics

Abstract

The invention discloses an engine accessory on-condition maintenance decision-making method considering inherent characteristics and repair characteristics, and belongs to the field of turbine engine maintenance, and the method comprises the following steps: classifying turboshaft engine accessories based on the inherent characteristics to obtain classified accessories, the classified accessories comprise a repairable accessory and an unrepairable accessory; performing fault damage analysis on the classified accessories to obtain an external field maintenance decision; determining factory return maintenance accessories based on the external field maintenance decision; and analyzing the factory return maintenance accessory based on the repair characteristics to determine a maintenance decision of the accessory in the overhaul. The method can be used for guiding the maintenance decision of accessories of the turboshaft engine in external field use and factory return overhaul stages, scientifically determining the maintenance mode and the disassembly depth, improving the reliability and maintainability of the engine, reducing the maintenance cost and improving the guarantee capability of the engine.

Description

Technical Field

[0001] The present invention belongs to the technical field of turbine engine maintenance, and in particular relates to a condition-based maintenance decision-making method for engine components and accessories taking into account inherent characteristics and repair features. Background Art

[0002] The turboshaft engine is the core power unit of a helicopter and can be broadly divided into the engine itself and accessories. Unlike the engine itself, accessories (typically field-replaceable units) are key components designed for rapid maintenance and replacement. Their characteristics can be summarized as modular design and high environmental adaptability. Accessories can generally be divided into repairable and non-repairable.

[0003] Currently, maintenance decisions for turboshaft engine components primarily rely on scheduled maintenance and post-failure repair models. These maintenance is performed based on fixed cycles or empirical judgment. While this ensures basic reliability, it has significant limitations: fixed-cycle replacements can easily lead to over-maintenance of non-failed components and waste of spare parts, while post-failure repairs increase safety risks and operating costs due to sudden downtime. Furthermore, subjective judgments based on manual experience can easily lead to misjudgments or missed inspections, and paper-based record management results in data fragmentation, making it difficult to trace the full lifecycle status of engine components and predict potential failures. Therefore, the present invention proposes a condition-based maintenance decision-making method for engine components that takes into account inherent characteristics and repair features. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a condition-based maintenance decision-making method for engine components and accessories taking into account inherent characteristics and repair features, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above objectives, the present invention provides a method for condition-based maintenance decision-making of engine components and accessories that takes into account inherent characteristics and repair features, comprising:

[0006] Classifying turboshaft engine accessories based on inherent characteristics to obtain classified accessories, wherein the classified accessories include: repairable accessories and non-repairable accessories;

[0007] Performing a fault damage analysis on the classified accessories to obtain an outfield maintenance decision;

[0008] Determining the cost of returning to the factory for repair based on the off-site repair decision;

[0009] The repair decision for the accessory during overhaul is determined by analyzing the accessory returned for repair based on the repair characteristics.

[0010] Optionally, the inherent characteristics include: maintainability design features, material properties, service life, functional importance and adaptability to the operating environment.

[0011] Optionally, the process of performing fault damage analysis on the classified accessories to obtain an outfield maintenance decision includes:

[0012] Performing qualitative damage mode determination on the classified accessories based on a numerical control monitoring method to obtain qualitative analysis results, and determining an off-site maintenance decision based on the qualitative analysis results;

[0013] When an off-site maintenance decision for the classified accessories cannot be determined based on the numerical control monitoring method, a quantitative analysis method is used to formulate corresponding maintenance decision criteria for the classified accessories, the damage pattern of the classified accessories is quantified based on the maintenance decision criteria to obtain a quantitative analysis result, and an off-site maintenance decision is determined based on the quantitative analysis result;

[0014] For damage modes that cannot be quantified, the corresponding fault threshold interval is set through field maintenance experience, expert judgment, and historical data accumulation methods to quantify the damage modes that cannot be quantified and obtain field maintenance decisions.

[0015] Optionally, the field maintenance decision includes:

[0016] For repairable accessories, determine whether to replace, scrap, or return to the factory for repair based on the qualitative or quantitative analysis results of the damage pattern;

[0017] For non-repairable accessories, the remaining life of the non-repairable accessories is predicted using the historical operating data, fatigue life curve and degradation model of the non-repairable accessories, and whether to replace them is determined based on the remaining life.

[0018] Optionally, the process of analyzing the returned accessories for repair based on repair characteristics and determining a repair decision for the accessories under overhaul includes:

[0019] Conducting a factory inspection on the returned accessories to determine whether the damage level of the returned accessories is repairable;

[0020] If the returned part is repairable, a repair level is determined according to a threshold value of the damage parameter, and a major repair decision is made based on the repair level;

[0021] If the accessory returned for repair is not repairable, a major repair decision is made based on the criticality of the accessory, replacement cost, and feasibility of alternatives.

[0022] Optionally, the process of formulating an overhaul maintenance decision based on the maintenance level includes: for the repairable parts to be returned to the factory for repair, introducing a repair value ratio based on the remaining life to conduct a quantitative analysis to formulate an overhaul maintenance decision;

[0023] The calculation expression of the repair value ratio is:

[0024]

[0025] Where, L repair L is the remaining life after repair; new The standard life of a new part or the life of a repaired part; C new For new parts fee; C repair is the repair cost; RVR is the repair value ratio.

[0026] Optionally, the process of making an overhaul decision based on criticality, replacement cost, and alternative feasibility includes: establishing a multi-factor decision model that comprehensively considers cost, life, and criticality, making an overhaul decision based on the multi-factor decision model,

[0027] The expression of the multi-factor decision model is:

[0028]

[0029] Where, L repair L is the remaining life after repair; new The standard life of a new part or the life of a repaired part; C 等效 Cost is the calculated equivalent cost to be compared with the cost of a new part; C repair is the cost of repair parts; K f is the critical coefficient.

[0030] Optionally, the criticality coefficient is determined according to the criticality level of the attachment.

[0031] Among them, the criticality coefficient of high criticality accessories is 1.5;

[0032] The criticality factor of the medium criticality accessory is 1.2;

[0033] The criticality factor of low-criticality accessories is 1.0.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] The present invention's situation-based maintenance decision-making method for engine accessories that takes into account inherent characteristics and repair features achieves a scientific and refined maintenance strategy by accurately classifying accessories into repairable or unrepairable, and formulating maintenance decisions based on fault damage analysis and repair characteristics. Compared with traditional maintenance models, this method can significantly reduce maintenance costs and avoid resource waste and safety risks caused by excessive maintenance or post-fault repairs. By introducing the repair value ratio (RVR) and a multi-factor decision-making model, the economy and reliability of maintenance decisions are further optimized, the service life of accessories is extended, and the overall maintenance capability of the engine is improved. At the same time, this method is driven by actual status data, supports full life cycle management and fault prediction, and provides strong support for the intelligent maintenance of engine accessories. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0037] Figure 1 This is a schematic diagram of a method for condition-based maintenance decision-making for an engine that takes into account inherent characteristics and repair features according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0040] Example 1

[0041] Condition-based maintenance formulates maintenance strategies based on the actual condition data of the components. Its core advantages are:

[0042] Accurate decision-making: Sensors monitor the health status of accessories (such as wear, temperature, vibration, etc.) in real time to avoid excessive replacement during regular maintenance or passive repairs after failures, reduce resource waste and extend component life.

[0043] Risk prevention and control: Use data analysis to predict potential failures, plan maintenance windows in advance, and reduce flight safety risks and unplanned grounding losses caused by sudden failures.

[0044] Cost optimization: Dynamically adjust maintenance plans based on life prediction to reduce redundant spare parts inventory and ineffective disassembly and assembly, significantly lowering full lifecycle operation and maintenance costs.

[0045] Data-driven management: Integrating data from the entire accessory lifecycle supports root-cause analysis and design improvements, driving iterative upgrades to maintenance strategies. Compared to traditional models, condition-based maintenance improves maintenance efficiency and reliability through proactive and intelligent means, providing a key enabler for the intelligent transformation of aviation equipment.

[0046] The present invention takes the inherent characteristics and repair features of turboshaft engine accessories as the analysis objects, and proposes a situation-based maintenance decision-making method that comprehensively considers the inherent characteristics and repair features of turboshaft engine accessories in response to the maintenance needs of turboshaft engine accessories during field operation and overhaul.

[0047] This method can be used to guide maintenance decisions for turboshaft engine components during field use and factory overhaul, scientifically determine maintenance methods and disassembly depth, improve engine reliability and maintainability, reduce maintenance costs, and enhance engine support capabilities.

[0048] like Figure 1 As shown, this embodiment provides a condition-based maintenance decision-making method for engine components and accessories that takes into account inherent characteristics and repair features, including the following steps:

[0049] Step 1: Analyze the inherent characteristics and repair features of turboshaft engine accessories. Classify turboshaft engine accessories based on the inherent characteristics to obtain classified accessories, wherein the classified accessories include repairable accessories and non-repairable accessories.

[0050] The engine accessories include two types: repairable accessories and non-repairable accessories.

[0051] In engine maintenance decisions, the inherent characteristics and repair features of components are key considerations. Engine components are often complex in structure, high in value, and have stringent performance requirements.

[0052] The inherent characteristics of an accessory refer to the key features inherent in its design and manufacturing process that affect its performance and maintenance strategy, including maintainability design features, material properties, service life, functional importance and the influence of the operating environment. These ultimately determine the maintainability of the accessory and, based on this, the accessories are further divided into two categories (repairable accessories and non-repairable accessories).

[0053] In this regard, the inherent characteristics of the accessories can be specifically evaluated and generally divided into two levels:

[0054] Regarding maintainability design features, Level 1 refers to redundant design and modular design, with relevant maintainability designs fully or partially considered; Level 2 refers to the lack of relevant maintainability designs and inability to perform repairs, such as one-piece molded parts.

[0055] In terms of material properties, Level 1 is standard materials and special materials, which are generally stable in nature and relatively simple or easy to repair; Level 2 is highly specialized materials, which are generally only used in specific parts or for specific functions, and are difficult to repair or not repairable.

[0056] Regarding service life, Level 1 is long or medium life. Long-life accessories require only maintenance within their designed life cycle and do not require replacement. Medium-life accessories can be maintained or replaced based on inspection and monitoring results. Level 2 is short-life or disposable components that cannot be repaired or have a very low repair value ratio and are only used once.

[0057] In terms of functional importance, Level 1 refers to non-critical components or critical components. For non-critical components, failure will not directly affect engine safety. For critical components, failure will cause performance degradation, affecting use but not fatal. Level 2 refers to critical components, which are directly related to engine control and safety and must be kept in working order.

[0058] Regarding operating environment adaptability, Level 1 is a mild or acceptable non-extreme working environment, in which case the environmental adaptability requirements of the components are not high; Level 2 is an extreme working environment, which requires the components to have extremely high environmental adaptability.

[0059] Therefore, if the number of Level 2 dimensions of an accessory's inherent characteristics reaches or exceeds 1, it can be considered an unrepairable accessory. In other words, if an accessory is rated Level 2 in key dimensions such as maintainability design features, material properties, service life, functional importance, or operating environment adaptability, it indicates that the accessory is unrepairable or irrecoverable and cannot be effectively repaired.

[0060] Secondly, repair characteristics primarily involve repair costs, repair methods, and the required condition of specific components after repair. Specific repair decisions must be constrained by the repair characteristics of the accessory. These characteristics dictate the need for flexible, situation-based maintenance strategies to accommodate the individual repair needs of different components, improving maintenance efficiency and support capabilities.

[0061] The analysis of inherent characteristics and repair features is the core basis of the condition-based maintenance decision-making model. Therefore, maintenance decisions require a comprehensive assessment of these factors and the classification of specific components to ensure that the repaired components meet airworthiness and safety requirements.

[0062] Step 2: Decision on field maintenance of accessories: Perform a fault damage analysis on the classified accessories to obtain a field maintenance decision.

[0063] The first thing to be clear is that in the field component maintenance decision-making process, only the components that require maintenance decisions will be replaced.

[0064] Field maintenance decisions are based on the inherent characteristics of each component, determining whether a specific component is repairable or not. Subsequently, methods such as manual inspection, engine health management (EHM), and digital control monitoring are used to conduct qualitative or quantitative analysis of the damage. This allows for a decision on whether to replace, scrap, or return the component to the factory for repair. Generally speaking, for components whose damage patterns can be qualitatively identified through digital control monitoring, field maintenance decisions can be made based on the qualitative analysis results.

[0065] For some components whose failure modes cannot be directly determined through CNC monitoring, when the failure modes have quantifiable characteristics, quantitative analysis methods can be used to formulate corresponding maintenance decision criteria. Based on the preset failure threshold range (X1, X2, X3), the maintenance strategy is dynamically adjusted:

[0066] Normal range (when 0≤ parameter value<X1), normal use;

[0067] During the monitoring period (when X1≤parameter value<X2), periodic monitoring with a duration of t1 is implemented;

[0068] In the early warning interval (when X2≤ parameter value<X3), high-frequency detection (cycle t2<t1) is implemented, focusing on monitoring, inspection, and testing;

[0069] Execution interval (when X3≤parameter value) triggers component replacement.

[0070] For non-quantifiable failure modes, which can only be analyzed qualitatively, corresponding fault thresholds can be set based on field maintenance experience, expert judgment, and historical data accumulation. These methods transform previously non-quantifiable failure modes into quantifiable and monitorable features, ultimately aligning the analysis of non-quantifiable failure modes with quantifiable ones, thereby achieving unified maintenance decision-making standards.

[0071] For repairable accessories, when it is determined that an accessory is faulty and must be replaced, a new part or repaired part (series of parts) is directly replaced on site, and the faulty part is directly scrapped or returned to the accessory factory for repair. After returning to the accessory factory, further inspection will be carried out to decide whether to repair or scrap it.

[0072] This process mainly generates transaction fees, new parts fees and repair costs incurred by the accessories factory.

[0073] Non-repairable accessories, such as certain high-precision sensors and single-shot molded components, typically possess inherent characteristics: high design precision, specialized materials, and strictly limited service lives. These characteristics directly impact engine performance, necessitating a determination of whether the non-repairable accessory meets replacement criteria. Therefore, during overhauls, accurate predictions of the accessory's remaining life are required using historical operating data, fatigue life curves, and degradation models.

[0074] Remaining life prediction first requires collecting operational data from the accessory during actual use, including operating hours, load variations, and environmental factors, as the basic data source for prediction. Subsequently, based on material testing and historical failure cases, fatigue life curves are established to clarify the accessory's life characteristics under different loads and operating conditions. Furthermore, an appropriate degradation model, such as a linear degradation model or a random process model, is selected to describe the gradual attenuation of the accessory's key performance parameters over time or over its lifetime.

[0075] In specific applications, historical data is analyzed to identify key parameters in the degradation model, enabling the model to adapt to actual operating conditions and improving prediction accuracy. Current accessory health data is input into the model and combined with fatigue life curves to predict future performance trends and determine the remaining time or number of cycles to reach the failure threshold. This approach fully integrates the advantages of data-driven and mechanistic models, effectively reflecting the actual degradation process of accessories and providing a basis for formulating scientific maintenance strategies for irreparable accessories.

[0076] When an accessory that cannot be repaired needs to be replaced, a new part will be directly replaced on site and the old part will be scrapped.

[0077] This process mainly incurs transaction fees and new item fees.

[0078] Step 3: Decision on overhaul accessories considering repair characteristics: Determine the accessories to be returned for repair based on the field repair decision; and determine the overhaul accessory repair decision based on the repair characteristics by analyzing the accessories to be returned for repair.

[0079] From step three onwards, the objects of maintenance decisions are all accessories whose inherent characteristics are defined as repairable. The inherent characteristics of repairable accessories include their high value, the repairability of materials, and the complexity of structure and function. These accessories can withstand harsh operating conditions, and their repair characteristics are mainly reflected in the ability to be repaired multiple times, the targeted repair process, the high requirements for the inspection and repair process, and the balance between cost and life. Their design often takes into account both performance requirements and maintainability requirements, allowing functions to be restored through specific processes (such as welding, coating or machining). The repair process of these accessories requires high-precision testing and strict quality control to ensure that the performance after repair is close to or reaches the original standard, thereby extending its service life and improving the economic efficiency of maintenance.

[0080] After an off-site monitoring inspection determines that a component requires repair, it is returned to the overhaul facility for inspection to determine the extent of damage to the component and whether it is repairable or not, allowing for further work. It's important to note that repairability is determined by the repair characteristics of each component.

[0081] When the damage indicators such as crack length, wear, deformation, etc. are within the standard allowable range and the function can be restored through welding, grinding, coating and other processes, the accessory can be considered repairable. Based on the threshold of damage parameters, the repair level can be defined:

[0082] Level 1 (0≤parameter value<Y1), allowed to continue service without repair;

[0083] Level 2 (Y1≤parameter value<Y2), new parts need to be replaced or old parts need to be repaired;

[0084] Level 3 (Y2≤ parameter value<Y3), new parts need to be replaced, old parts cannot be repaired and are directly scrapped;

[0085] When the damage exceeds the allowable limit or causes irreversible changes in material properties (such as severe ablation, through-the-hole cracks, etc.), the accessory is considered unrepairable.

[0086] Step 4: Decision on repair of repairable accessories during overhaul.

[0087] For repairable accessories, the repair characteristics must be comprehensively considered to determine whether to replace or dispose of the old parts. The old parts must be returned to the accessory factory for further decision-making to determine whether to repair or scrap them.

[0088] This invention introduces a method for quantifying the Repair Value Ratio (RVR) based on the remaining life. The RVR formula is as follows:

[0089]

[0090] Among them, L repair L is the remaining life after repair; new The standard life of a new part or the life of a repaired part (string of parts); C new For new parts fee; C repair For repair costs.

[0091] If RVR is less than 1, the old part will be scrapped and replaced with a new part or a repaired part (series part) depending on the cost. This process will incur new part fees.

[0092] If RVR≥1, the old part will be returned to the corresponding accessory factory for further inspection. The overhaul factory will replace it with a new part or repair it (series part) depending on the cost. This process will generate repair fees, new part fees, and repair fees incurred by the accessory factory.

[0093] Step 5: Make repair decisions for accessories that cannot be repaired during overhaul.

[0094] Although non-repairable components cannot be directly repaired, their replacement cost, criticality, and alternative feasibility still need to be considered in overhaul decisions. Due to the criticality factor involved, the RVR model in step four is not applicable to this step. To this end, a multi-factor decision-making model that comprehensively considers cost, life, and criticality can be established. This model takes the equivalent cost of the repaired component as its core and, by introducing the remaining life ratio and criticality coefficient, comprehensively evaluates its actual economic efficiency relative to new components. Specifically, the equivalent cost of the repaired component is calculated by dividing the repair cost by the ratio of its remaining life to the life of the new component, and further multiplying it by the criticality coefficient to quantify the impact weight of the critical component on the safety and functional integrity of the system. Among them, the remaining life ratio reflects the degree of reduction in the useful life cycle of the repaired component relative to the life of the new component; the criticality coefficient is graded and amplified according to the importance of the component in the system. For example, safety-critical components can be given a higher weight coefficient.

[0095] The details are as follows:

[0096]

[0097] Among them, L repair L is the remaining life after repair; new The standard life of a new part or the life of a repaired part (string of parts); C 等效成本 is the calculated equivalent cost to be compared with the cost of the new part; C repair is the cost of repair parts; K f is the critical coefficient.

[0098] Component criticality is categorized into three categories: high, medium, and low, based on their functional impact and the consequences of their failure. High-criticality components are crucial to the core functionality or safety of the system; their failure will result in equipment unavailability or a serious accident. Medium-criticality components affect system performance or mission execution, and short-term failures will not cause complete equipment downtime. Low-criticality components do not directly affect core functionality, and their failure will not cause system downtime.

[0099] The specific values of the criticality coefficient for components of different criticality can be determined in engineering practice. Here, for high, medium, and low criticality components, the values can be considered to be 1.5, 1.2, and 1.0 respectively.

[0100] For non-repairable accessories, new parts or repaired parts (strings) can be replaced according to the above models during overhaul.

[0101] During this process, the main costs incurred are repair costs and new parts costs.

[0102] The present invention, focusing on the inherent characteristics and repair features of turboshaft engine accessories, has developed a set of on-site maintenance and depot repair decision-making methods for turboshaft engine accessories, which has the following advantages:

[0103] Strong targeting: Combining the inherent characteristics of accessories (such as materials, structure, working environment) and repair characteristics (such as repairability and repair cost), more precise maintenance strategies are formulated to improve the scientific nature of maintenance decisions.

[0104] Reduce maintenance costs: By properly assessing component status, you can avoid excessive maintenance or premature replacement, reduce unnecessary maintenance expenses, and improve cost-effectiveness.

[0105] Improve reliability and safety: Make maintenance decisions based on the actual service status of accessories, reduce the probability of failure, and ensure reliable operation of the engine.

[0106] Optimize spare parts management: Optimize spare parts selection and reserves based on the maintenance methods and replacement requirements of different accessories.

[0107] Extend service life: Through precise condition-based maintenance, the remaining life of accessories can be fully utilized to avoid early scrapping and improve resource utilization.

[0108] As a specific implementation of this embodiment, this embodiment takes a certain type of turboshaft engine as an example, and selects some components and accessories for illustration, as shown in Table 1:

[0109] Table 1

[0110]

[0111]

[0112] In terms of the inherent characteristics of the accessory: The electronic controller features a high degree of integration, high environmental adaptability, high precision and real-time performance, high reliability, and intelligence. Through a modular design, the electronic controller integrates signal processing, logic control, and data transmission. It can operate stably in harsh environments such as high temperature, high pressure, strong vibration, and electromagnetic interference, and provides precise, high-speed control capabilities. It utilizes redundant design and adaptive control technology to ensure system safety and dynamic optimization performance, and possesses excellent maintainability and self-test capabilities. Based on these inherent characteristics, it is determined to be a repairable accessory. Field monitoring is typically performed through visual inspection, CNC BIT testing, and other methods to determine the damage mode.

[0113] The lubricating oil pump is an electromechanical product, constructed with high-precision machining and high-temperature-resistant sealing materials. As a core component of the turboshaft engine's lubrication system, it ensures efficient lubricating oil circulation and stable pressure. The lubricating oil pump offers high reliability and wear resistance. If a failure occurs, such as wear, seal aging, or internal leakage, its function can be restored by replacing seals, repairing the pump body, or replacing worn parts. The lubricating oil pump must operate stably and long-term in high-temperature, high-pressure, and complex oil environments, placing high demands on sealing and mechanical durability. These inherent characteristics determine it as a repairable accessory.

[0114] Oil filters are electromechanical components primarily used to filter impurities and particulates from lubricating oil, preventing contaminants from entering the engine's lubrication system, thereby ensuring the proper functioning of critical components such as bearings and gears. Their core component is a high-precision filter element, capable of maintaining stable filtration performance under high temperatures, high pressures, and complex operating conditions. The oil filter must withstand the pressure fluctuations caused by the flow of lubricating oil and maintain normal operation within a specified pressure differential range. If the filter element becomes clogged or the pressure differential exceeds the specified range, it must be replaced or cleaned to ensure lubrication system reliability. These inherent characteristics determine it to be a repairable accessory.

[0115] The accessory casing nozzle oil circuit is an electromechanical component constructed from high-precision, wear-resistant materials. As a critical component of the turboshaft engine's lubrication and fuel system, it ensures efficient oil delivery and stable injection. Despite its precision flow path design, repairs are not sufficient to restore performance if clogged, worn, or deformed. The accessory casing nozzle oil circuit must operate stably and long-term under high temperatures, high pressures, and fluid impact, requiring high levels of wear resistance and sealing. These inherent characteristics determine it to be a non-repairable accessory.

[0116] The T45 thermocouple is an electromechanical component constructed from high-temperature-resistant materials and special alloys. It serves as a critical temperature measurement component in turboshaft engines, ensuring accurate measurements in high-temperature environments. Designed for rapid response and high precision, the T45 thermocouple must operate reliably in environments with extreme heat, dramatic temperature swings, and potential chemical corrosion. Its high heat and oxidation resistance requirements make it impossible to restore its measurement performance through repair. These inherent characteristics determine it to be a non-repairable accessory.

[0117] The rotating vortex speed sensor is an electronic product that utilizes high-precision sensing elements and anti-interference circuitry. As a key parameter measurement component for turboshaft engines, it ensures accurate acquisition and real-time monitoring of speed signals. The rotating vortex speed sensor possesses high sensitivity and immunity to electromagnetic interference. It must operate stably in environments with high temperatures, high vibration, and strong electromagnetic interference, placing high demands on reliability and environmental adaptability. If performance degradation, component damage, or signal anomalies occur, repairs are not possible to restore measurement accuracy. These inherent characteristics determine that it is a non-repairable accessory.

[0118] Main bearings are mechanical components made of high-strength, wear-resistant alloys. They serve as the core support component of turboshaft engines, ensuring stable mainshaft rotation and power transmission. They require high-precision machining and long-life lubrication. They must operate reliably and consistently under high temperatures, high speeds, high loads, and complex stress environments, placing extremely high demands on durability and reliability. Fatigue damage, excessive wear, or lubrication failure cannot be restored through repair. These inherent characteristics make them non-repairable accessories.

[0119] Repair Characteristics: As components designed for rapid maintenance and replacement, these components are all repairable and can be flexibly replaced in the field. The specific repair characteristics of each component require a detailed analysis based on its actual damage, primarily including repair costs, repair methods, and the required condition of the component after repair. Therefore, detailed repair characteristic analyses of specific components will be conducted in subsequent steps.

[0120] Field maintenance strategy: For different types of accessories, field maintenance decisions need to be made based on different maintenance decision-making criteria. When the performance range is reached or the CNC monitoring system detects functional failure, the field will replace the part and return the old part to the factory for repair.

[0121] For electronic control components, since they have self-checking capabilities, decisions can be made based on the CNC monitoring results.

[0122] For lubricating oil pumps, as electromechanical products, field inspections typically involve visual inspection, lubricating oil monitoring, vibration monitoring, and CNC BIT monitoring to determine their failure modes. Common failure modes include: housing scratches, visible cracks, wear, and oil leakage. The decision criteria are as follows:

[0123] a) Scratches on the oil pump housing:

[0124] When it is in the normal range (0≤scratch depth<0.1mm), it can be used normally;

[0125] When in the monitoring range (0.1mm≤scratch depth<0.3mm), implement periodic monitoring (one flight inspection every 50 times);

[0126] When in the warning range (0.3mm≤scratch depth<0.5mm), high-frequency inspections are implemented (once every 20 flight inspections), focusing on monitoring, inspection, and testing;

[0127] When it is in the execution range (0.5mm≤scratch depth), the replacement of parts is triggered and the old parts are returned to the factory for repair.

[0128] b) Wear of lubricating oil pump:

[0129] When it is in the normal range (0≤wear<0.02mm), it can be used normally;

[0130] When in the monitoring range (0.02mm≤wear<0.05mm), implement periodic monitoring (once every 100 flight inspections);

[0131] When in the warning range (0.05mm≤wear<0.1mm), high-frequency inspections (once every 50 flight inspections) are implemented, with focused monitoring, inspection, and testing;

[0132] When it is in the execution range (0.1mm≤wear), the replacement of parts is triggered and the old parts cannot be repaired.

[0133] c) Oil pump leakage:

[0134] Not allowed and cannot be repaired.

[0135] d) Visible cracks in the lubricating oil pump:

[0136] Not allowed and cannot be repaired.

[0137] For oil filters, as electromechanical components, field testing typically involves visual inspection, vibration monitoring, metal shavings monitoring, and oil testing to determine failure modes. Common failure modes include oil leakage, blockage, screen damage and element rupture, vibration damage, false alarms and sensor failure, and bypass valve failure.

[0138] a) Oil leakage from oil filter:

[0139] When it is in the normal range (0≤oil leakage<0.001ml / h), it can be used normally;

[0140] When in the monitoring range (0.001ml / h≤oil leakage<0.01ml / h), inspection is required (after every 5 flights);

[0141] When the oil leakage rate is within the warning range (0.01ml / h≤oil leakage<0.1ml / h), conduct a focused inspection (after each flight);

[0142] When the oil leakage is 0.1ml / h or less in the execution range, new parts need to be replaced.

[0143] b) Oil filter blockage:

[0144] When it is in the normal range (when the oil flow rate drops by less than 5%), it can be used normally;

[0145] When in the monitoring range (5% ≤ oil flow drop < 10%), regular inspection and attention are required (inspection every 15 working cycles);

[0146] When in the warning range (10% ≤ oil flow rate drop < 15%), conduct key inspections (every 5 working cycles);

[0147] When in the execution range (oil flow drops ≥15%), stop using the device immediately and return it to the factory for repair.

[0148] c) The oil filter screen is damaged or the filter element is broken:

[0149] When it is in the normal range (damage area < 2%), it can be used normally;

[0150] When in the monitoring range (2% ≤ damaged area < 5%), regular inspection and attention are required (inspection every 20 working cycles);

[0151] When it is in the warning range (5% ≤ damaged area < 10%), conduct key inspections (inspection every 10 working cycles);

[0152] When it is in the execution range (damaged area ≥ 10%), stop using it immediately and return it to the factory for repair.

[0153] d) Vibration damage to oil filter:

[0154] When in the normal range (when the vibration amplitude is less than 0.2m / s 2 ), normal use;

[0155] When in the monitoring area (0.2m / s 2 ≤Vibration amplitude<0.5m / s 2 ), requires regular inspection and attention (every 15 working cycles);

[0156] When in the warning range (0.5m / s 2 ≤Vibration amplitude<1.0m / s 2 ), conduct key inspections (every 5 working cycles);

[0157] When in the execution range (vibration amplitude ≥ 1.0m / s 2 ), stop using immediately and return to the factory for repair

[0158] e) False alarm of oil filter and sensor failure:

[0159] When it is in the normal range (when the false alarm rate is less than 1%), it can be used normally;

[0160] When in the monitoring range (1% ≤ false alarm rate < 3%), regular monitoring and attention are required (detection every 30 working cycles);

[0161] When in the warning range (3% ≤ false alarm rate < 5%), conduct key detection (detection every 15 working cycles);

[0162] When in the execution range (false alarm rate ≥ 5%), stop using it immediately and return it to the factory for repair.

[0163] f) The oil filter bypass valve cannot be opened:

[0164] When it is in the normal range (when the abnormal opening frequency is less than 1 time / 100 working cycles), it can be used normally;

[0165] When in the monitoring range (abnormal opening frequency is 1 to 3 times / 100 working cycles), regular inspection and attention are required (every 50 working cycles);

[0166] When in the warning range (abnormal opening frequency is 3 to 5 times / 100 working cycles), carry out key detection (detection every 20 working cycles);

[0167] When in the execution range (abnormal opening frequency > 5 times / 100 working cycles), stop using it immediately and return it to the factory for repair or replacement of the bypass valve.

[0168] For accessory casing nozzle oil circuits, as electromechanical products, field inspections are typically conducted through visual inspection and borescope testing to determine damage modes. Common failure damage modes include blockage and oil leakage.

[0169] a) Oil leakage from the nozzle oil circuit of the accessory casing:

[0170] When it is in the normal range (0≤oil leakage<0.001ml / h), it can be used normally;

[0171] When in the monitoring range (0.001ml / h≤oil leakage<0.01ml / h), inspection is required (after every 5 flights);

[0172] When the oil leakage rate is within the warning range (0.01ml / h≤oil leakage<0.1ml / h), conduct a focused inspection (after each flight);

[0173] When the oil leakage is 0.1ml / h or less in the execution range, the parts need to be replaced immediately.

[0174] b) The oil circuit of the nozzle of the accessory casing is blocked:

[0175] When it is in the normal range (when the oil flow rate drops by less than 5%), it can be used normally;

[0176] When in the monitoring range (5% ≤ oil flow drop < 10%), regular inspection and attention are required (inspection every 15 working cycles);

[0177] When in the warning range (10% ≤ oil flow rate drop < 15%), conduct key inspections (every 5 working cycles);

[0178] When it is in the execution range (oil flow drops ≥15%), new parts must be replaced immediately.

[0179] For T45 thermocouples, which are electromechanical products, field damage modes are typically determined using visual inspection and digital BIT monitoring. Common damage modes include inaccurate output, no signal output, probe bending, cracks and scratches on the rigid conduit, and probe cracks or fissures.

[0180] a) The output of the T45 thermocouple is inaccurate or there is no signal output:

[0181] For this failure mode, the T45 thermocouple has self-detection capabilities, so decisions can be made based on the CNC monitoring results.

[0182] b) T45 thermocouple probe bending:

[0183] When in the normal range (probe bending angle < 1°), use it normally;

[0184] When in the monitoring range (1°≤probe bending angle<3°), implement periodic monitoring (check once every 50 working cycles);

[0185] When in the warning range (3°≤probe bending angle<5°), implement high-frequency testing (check once every 20 working cycles), focusing on monitoring, inspection, and testing;

[0186] When in the execution range (probe bending angle ≥ 5°), the component replacement is triggered.

[0187] c) Cracks and scratches on the rigid conduit of T45 thermocouple:

[0188] When it is in the normal range (crack width or scratch depth < 0.1mm), it can be used normally;

[0189] When in the monitoring range (0.1mm≤crack width or scratch depth<0.3mm), implement periodic monitoring (check every 50 working cycles);

[0190] When in the warning range (0.3mm ≤ crack width or scratch depth < 0.6mm), implement high-frequency testing (inspection every 20 working cycles) with focused monitoring, inspection, and testing;

[0191] When it is in the execution range (crack width or scratch depth ≥ 0.6mm), the part replacement is triggered.

[0192] d) T45 thermocouple probe cracks or cracks, etc.:

[0193] When it is in the normal range (crack width < 0.1 μm), it can be used normally;

[0194] When in the monitoring range (0.1μm≤crack width<0.3μm), implement periodic monitoring (check once every 50 working cycles).

[0195] When in the early warning range (0.3μm≤crack width<0.5μm), implement high-frequency testing (inspection every 20 working cycles), focusing on monitoring, inspection, and testing;

[0196] When in the execution range (crack width ≥ 0.5μm), component replacement is triggered.

[0197] For electronic products, vortex speed sensors are typically monitored in the field using digital control bit-in-the-loop (BIT) monitoring. Common failure modes include no output, deviation, and sudden signal changes. Since these sensors have self-checking capabilities, decisions can be made based on the results of digital control monitoring.

[0198] For main bearings, which are mechanical products, their failure modes are typically determined in the field through vibration monitoring, visual inspection, borescope inspection, etc. Common failure modes include surface fatigue peeling and cracks in the inner and outer rings.

[0199] a) Surface fatigue peeling of the main bearing:

[0200] When in the normal range (peeling area < 0.5mm 2 ), normal use;

[0201] When in the monitoring range (0.5mm 2 ≤Peeling area<2mm 2 ), implement periodic monitoring (check every 50 working cycles);

[0202] When in the warning range (2mm 2 ≤Peeling area<5mm 2 ), implement high-frequency testing (inspection every 20 working cycles), focus on monitoring, inspection and testing;

[0203] When in the execution range (peeling area ≥ 5mm 2 ), triggering the replacement of parts.

[0204] b) Cracks on the inner and outer rings of the main bearing:

[0205] When it is in the normal range (crack width < 1μm), it can be used normally;

[0206] When in the monitoring range (1μm≤crack width<5μm), implement periodic monitoring (check once every 50 working cycles);

[0207] When in the early warning range (5μm≤crack width<10μm), implement high-frequency testing (inspection every 20 working cycles), focusing on monitoring, inspection, and testing;

[0208] When in the execution range (crack width ≥ 10μm), component replacement is triggered.

[0209] Considering the repair characteristics of each component, the decision to return to the factory for repair is made: At this point, the analysis of the repair characteristics of each component is limited to the repairable accessories. Moreover, when the damage exceeds the allowable limit or causes irreversible changes in material properties (such as severe ablation, crack penetration, etc.), some failure modes of the repairable accessories cannot be repaired and will not be discussed until the third step.

[0210] For electronic control components, it is necessary to first analyze the repair characteristics of the specific faulty parts and then conduct a specific analysis based on the repair characteristics.

[0211] For the oil pump, according to the field analysis in step 2, only the oil pump housing scratch is repairable. Therefore, a detailed analysis of this failure mode is conducted.

[0212] a) Scratches on the oil pump housing:

[0213] Level 1 (0≤scratch depth<0.1mm), allowed to continue in service without repair;

[0214] Level 2 (0.1mm≤scratch depth<1.0mm), need to replace with new parts or repair the old parts;

[0215] Level 3 (1.0mm ≤ scratch depth), need to replace with new parts, the old parts cannot be repaired and should be scrapped directly

[0216] For the oil filter, according to the field maintenance analysis in step 2, the following fault modes can be repaired: oil filter blockage, filter screen damage and filter element rupture, vibration damage, false alarm and sensor failure, bypass valve failure, etc.

[0217] a) Oil filter blockage:

[0218] Level 1 (oil flow rate decrease <5%), allowing continued service without repair;

[0219] Level 2 (5% ≤ oil flow rate drop < 20%), need to replace new parts or repair old parts;

[0220] Level 3 (20% ≤ oil flow rate drop), new parts need to be replaced, old parts cannot be repaired and must be scrapped directly.

[0221] b) The oil filter screen is damaged or the filter element is broken:

[0222] Level 1 (damage area <2%): allowed to continue service without repair;

[0223] Level 2 (2% ≤ damaged area < 15%), need to replace with new parts or repair old parts;

[0224] Level 3 (15% ≤ damaged area): new parts must be replaced. Old parts cannot be repaired and must be scrapped directly.

[0225] c) Vibration damage to oil filter:

[0226] Level 1 (vibration amplitude < 0.2m / s 2 ), allowed to continue in service without repair;

[0227] Level 2 (0.2m / s 2 ≤Vibration amplitude<2.0m / s 2 ), need to replace with new parts or repair old parts;

[0228] Level 3 (2.0m / s 2 ≤vibration amplitude), new parts need to be replaced. Old parts cannot be repaired and must be scrapped directly.

[0229] d) Lubricating oil filter false alarm and sensor failure:

[0230] Level 1 (false alarm rate <1%), allowed to continue service without repair;

[0231] Level 2 (1% ≤ false alarm rate < 10%), need to replace new parts or repair old parts;

[0232] Level 3 (false alarm rate 10% ≤): new parts must be used. Old parts cannot be repaired and must be scrapped directly.

[0233] e) The oil filter bypass valve cannot be opened:

[0234] Level 1 (abnormal opening frequency < 1 time / 100 working cycles), allowed to continue service without repair;

[0235] Level 2 (1≤abnormal opening frequency<10 times / 100 working cycles), it is necessary to replace new parts or repair old parts;

[0236] Level 3 (10 times / 100 working cycles ≤ abnormal opening frequency), new parts need to be replaced, old parts cannot be repaired and are directly scrapped.

[0237] Repair Decisions for Repairable Components: Based on the level definitions, further analysis is conducted on components with Level 2 failure modes. This analysis focuses on the repair cost and the remaining life before and after repair to support the calculation of the repair value ratio (RVR) for the remaining life.

[0238] There are two electronic control components with different damage patterns awaiting repair: Component #1 has a less severe fault, costing 50,000 yuan for repair and a remaining lifespan of 8,000 hours. Component #2 has a more severe fault, costing 70,000 yuan for repair and a remaining lifespan of 6,000 hours. The cost of a new component is 100,000 yuan, with a remaining lifespan of 10,000 hours. The calculated RVR for component #1 is 1.6, so repair is recommended. The calculated RVR for component #2 is approximately 0.857, so replacement is recommended.

[0239] For the lubricating oil pump, a component of this type, identified as having Grade 2 damage on the lubricating oil pump housing, was repaired. The severity of the failure was relatively minor, with a repair cost of 5,000 yuan and a remaining life of 7,000 hours. Among the lubricating oil pump spare parts, one repair component (series component) cost 20,000 yuan and had a remaining life of 8,000 hours. The calculated RVR of the current faulty component was 14. Clearly, repairing the faulty component is the optimal option.

[0240] For the lubricating oil filter, repair the two components of this type that are determined to be at the damage level 2 of each failure mode:

[0241] Faulty part #1 has a repair cost of 40,000 yuan and a remaining life of 5,000 hours; faulty part #2 has a repair cost of 28,000 yuan and a remaining life of 6,000 hours. There are currently two replacement parts available for the oil filter: Part #1 is a new part, costs 50,000 yuan, and has an estimated life of 10,000 hours; Part #2 is a repaired part, costs 30,000 yuan, and has an estimated life of 7,000 hours.

[0242] The RVR of faulty part No. 1 relative to spare part No. 1 (new part) is 0.625, and its RVR relative to spare part No. 2 (repaired part) is 0.536; while the RVR of faulty part No. 2 relative to spare part No. 1 (new part) is 1.07, and its RVR relative to spare part No. 2 (repaired part) is 0.92.

[0243] Therefore, faulty part No. 1 must be replaced, and since the RVR of faulty part No. 2 relative to spare part No. 2 (repaired part) is less than 1, spare part No. 2 (repaired part) can be replaced; thus, faulty part No. 1 can be replaced with spare part No. 1 (new part).

[0244] Repair decision for irreparable accessories: irreparable accessories, that is, components with damage level 3, need to be replaced with new parts or repaired parts (string parts) as appropriate during overhaul.

[0245] For the lubricating oil pump, since the engine lubricating oil pump has a very critical function, and the working environment is harsh, the load is high and the reliability requirements are high, it is defined as a high-criticality accessory with a criticality coefficient of 1.5.

[0246] The new lubricating oil pump costs 80,000 yuan and has a lifespan of 10,000 hours. The repair cost of the repaired part is 50,000 yuan and has a lifespan of 8,000 hours. Calculation shows that the equivalent cost is greater than the new part cost. Therefore, the new part is selected for replacement.

[0247] As an auxiliary filter in the engine lubrication system, the oil filter primarily filters impurities. Its operating environment is relatively mild, with low loads and moderate reliability requirements. Therefore, it is defined as a low-criticality accessory with a criticality coefficient of 1.0.

[0248] The cost of a new oil filter is 50,000 yuan, with a lifespan of 10,000 hours. The cost of a repaired part is 30,000 yuan, with a lifespan of 8,000 hours. Calculation shows that the equivalent cost is significantly less than the cost of a new part. Therefore, the repaired part is selected for replacement.

[0249] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A condition-based maintenance decision-making method for engine components and accessories that takes into account inherent characteristics and repair features, characterized in that: The following steps are involved: Classifying turboshaft engine accessories based on inherent characteristics to obtain classified accessories, wherein the classified accessories include: repairable accessories and non-repairable accessories; Performing a fault damage analysis on the classified accessories to obtain an outfield maintenance decision; Determining the cost of returning to the factory for repair based on the off-site repair decision; The repair decision for the accessory during overhaul is determined by analyzing the accessory returned for repair based on the repair characteristics.

2. The method according to claim 1, characterized in that The inherent characteristics include: maintainability design features, material properties, service life, functional importance and adaptability to the operating environment.

3. The method according to claim 1, characterized in that The process of performing fault damage analysis on the classified accessories to obtain field maintenance decisions includes: Performing qualitative damage mode determination on the classified accessories based on a numerical control monitoring method to obtain qualitative analysis results, and determining an off-site maintenance decision based on the qualitative analysis results; When an off-site maintenance decision for the classified accessories cannot be determined based on the numerical control monitoring method, a quantitative analysis method is used to formulate corresponding maintenance decision criteria for the classified accessories, the damage pattern of the classified accessories is quantified based on the maintenance decision criteria to obtain a quantitative analysis result, and an off-site maintenance decision is determined based on the quantitative analysis result; For damage modes that cannot be quantified, the corresponding fault threshold interval is set through field maintenance experience, expert judgment, and historical data accumulation methods to quantify the damage modes that cannot be quantified and obtain field maintenance decisions.

4. The method according to claim 3, characterized in that The field maintenance decision includes: For repairable accessories, determine whether to replace, scrap, or return to the factory for repair based on the qualitative or quantitative analysis results of the damage pattern; For non-repairable accessories, the remaining life of the non-repairable accessories is predicted using the historical operating data, fatigue life curve and degradation model of the non-repairable accessories, and whether to replace them is determined based on the remaining life.

5. The method according to claim 1, wherein The process of analyzing the returned accessories based on the repair characteristics and determining the repair decision for the accessories during overhaul includes: Conducting a factory inspection on the returned accessories to determine whether the damage level of the returned accessories is repairable; If the returned part is repairable, a repair level is determined according to a threshold value of the damage parameter, and a major repair decision is made based on the repair level; If the accessory returned for repair is not repairable, a major repair decision is made based on the criticality of the accessory, replacement cost, and feasibility of alternatives.

6. The method according to claim 5, characterized in that The process of making an overhaul decision based on the maintenance level includes: for repairable parts returned for repair, introducing a quantitative analysis based on the repair value ratio of the remaining life to make an overhaul decision; The calculation expression of the repair value ratio is: Where, L repair L is the remaining life after repair; new The standard life of a new part or the life of a repaired part; C new For the new part fee; C repair is the repair cost; RVR is the repair value ratio.

7. The method according to claim 6, characterized in that The process of making an overhaul maintenance decision based on criticality, replacement cost, and alternative feasibility includes: establishing a multi-factor decision model that comprehensively considers cost, life, and criticality; making an overhaul maintenance decision based on the multi-factor decision model; The expression of the multi-factor decision model is: Where, L repair L is the remaining life after repair; new The standard life of a new part or the life of a repaired part; C 等效 Cost is the calculated equivalent cost to be compared with the cost of a new part; C repair is the cost of repair parts; K f is the critical coefficient.

8. The method according to claim 7, characterized in that The criticality factor is determined according to the criticality level of the attachment. Among them, the criticality coefficient of high criticality accessories is 1.5; The criticality factor of the medium criticality accessory is 1.2; The criticality factor of low-criticality accessories is 1.0.

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