Helicopter tail transmission shaft bearing high-temperature troubleshooting method

Abstract

The invention belongs to the field of helicopters, and relates to a helicopter tail transmission shaft bearing high-temperature troubleshooting method, which comprises the following steps of: quickly locking main influence factors of a bearing high-temperature problem by adopting a method of keeping an aircraft platform unchanged and directly interchanging and assembling two tail shafts through stipulating temperature indicating sheets with A and B measuring range specifications and pasting positions; the actual working temperature of the bearing can be accurately collected by specifying the ground driving verification working condition and the running time, and the critical value of the normal working temperature of the bearing can be used as a fault judgment basis by determining the critical value. According to practical experience, the minimum radial clearance value after product combination and assembly and the in-cabin environment temperature range value are given, and a solution thought for the problem of high temperature of the tail shaft bearing is provided. And finally, checking complex conditions such as a whole helicopter mounting platform and tail beam deformation, so that the flight stopping time of the helicopter can be effectively shortened.

Description

Technical Field

[0001] The invention belongs to the field of helicopters and relates to a method for troubleshooting high temperature of a helicopter tail transmission shaft bearing. Background Art

[0002] The helicopter tail drive shaft (hereinafter referred to as the tail shaft) is an important part of the helicopter transmission system, and the tail shaft bearing is a key supporting component. The tail shaft bearing described in this article is a deep groove ball bearing with a sealing ring structure at both ends. The bearing is lubricated with grease, and the sealing structure adopts a combination seal with inner and outer rings with teeth, and a rubber sealing ring sandwiched between the spring rings on both sides. The sealing ring is fixed inside the outer ring teeth through the outer spring ring, and the inner diameter of the sealing ring fits the R lip surface of the inner ring. An L-shaped micro-contact design is adopted. When working, the inner ring of the bearing rotates, and the outer ring and the sealing ring do not rotate, forming a dynamic contact seal. The grease is evenly distributed inside the bearing as the rolling elements and retaining frames move, mainly playing the role of lubrication and anti-corrosion. The structure is shown in the attached Figure 1 The inner ring of the bearing and the spline joint are interference fit, the outer ring of the bearing and the outer bushing of the bearing are clearance fit, the inner ring of the bearing is locked and positioned by a round nut, and the outer ring of the bearing is axially positioned by elastic retaining rings on both sides. Its assembly on the tail transmission shaft is shown in the attached Figure 2 As shown. The operating temperature of the bearing is related to many factors such as the bearing itself and the external operating conditions. Under normal circumstances, it is generally not higher than 80℃. When the tail shaft bearing temperature is greater than or equal to 80℃, it is usually considered as a high temperature of the bearing. If the high temperature treatment of the bearing is not timely, the grease inside the bearing will deteriorate, the bearing matching accuracy will change, and in severe cases, the bearing will be stuck and die suddenly, eventually leading to the failure of the tail shaft and the helicopter crash. When the tail shaft bearing has a high temperature problem in the field, at this stage, the technicians usually rely on their personal experience to troubleshoot, which often results in incomplete troubleshooting and repeated faults, causing great inconvenience to users. Due to the lack of standardized process troubleshooting methods, the cause of the high temperature of the bearing cannot be accurately located, which increases the field inspection items and maintenance time, and poses a threat to the safety of pilots. With the increase in the number of tail drive shafts used in field helicopters, the problem of high temperature of the tail shaft bearing is also on the rise. Therefore, there is an urgent need for a standardized troubleshooting method for high temperature of the tail shaft bearing to improve troubleshooting efficiency, reduce the safety risk of field helicopter use, and reduce user complaints. Summary of the invention

[0003] Purpose of the Invention

[0004] The purpose of the present invention is to propose a method for troubleshooting high temperature of a helicopter tail shaft bearing. By standardizing and refining the method, the drawbacks of repeated faults caused by handling faults based on traditional experience can be overcome. Through standardized procedural troubleshooting, the cause of the fault can be accurately located, so that targeted corresponding solutions can be taken to ensure the working reliability of the tail shaft bearing, reduce the risk of safe use in the field, and reduce the user's daily maintenance work time.

[0005] Technical Solution

[0006] A method for troubleshooting high temperature of helicopter tail drive shaft bearings. By specifying two range specifications of temperature indicator sheets A and B and the sticking positions, the method of keeping the aircraft platform unchanged and directly interchangeably assembling the tail shafts of two aircraft can quickly lock the main influencing factors of the high bearing temperature problem. By specifying the ground start-up verification conditions and operating time, the actual working temperature of the bearing can be accurately collected. By clarifying the critical value of the normal working temperature of the bearing, it can be used as a basis for fault judgment. Based on practical experience, the minimum radial clearance value after the product combination is assembled and the range of cabin ambient temperature are given, providing a solution to the high temperature problem of the tail shaft bearing. The following steps are included:

[0007] Step (1) Before troubleshooting, prepare two temperature indicator sheets of A and B range specifications, check whether the temperature indicator sheets are within the validity period, and confirm whether the temperature indicator sheets have turned black. If there is no abnormality, proceed to the next step, otherwise replace the temperature indicator sheets;

[0008] Step (2) keeping the aircraft platform unchanged, swapping the tail shaft of the faulty aircraft with the tail shaft of another normal aircraft, that is, installing the tail shaft with the high-temperature bearing on the helicopter platform with normal bearing temperature, and installing the tail transmission shaft with normal bearing temperature on the faulty helicopter platform;

[0009] Step (3) performs ground start-up verification under the same period and the same operating time conditions. If the temperature of the original high-temperature bearing is still high or the temperature of the original normal-temperature bearing is still normal, it means that the original high temperature of the tail shaft bearing is mainly affected by the tail shaft itself. Therefore, it is necessary to conduct a detailed investigation of the tail shaft factors according to steps (4)-(9); if the temperature of the original high-temperature bearing turns normal or the temperature of the original normal-temperature bearing is high, it means that the original high temperature of the tail shaft bearing is mainly affected by the helicopter platform. Therefore, it is necessary to check the helicopter platform according to steps (10)-(13);

[0010] Step (4) Open the helicopter tail shaft protection cover and check whether the high-temperature bearing has grease leakage, seal wear, inflexible rotation, abnormal noise, etc. If no abnormality is found, proceed to the next step. Otherwise, replace the bearing and verify it according to the following steps;

[0011] Step (5) Re-attach the temperature indicator sheet and drive the vehicle on the ground with an empty mantle load for at least 30 minutes. After the operation is completed, observe the value of the temperature indicator sheet. If the displayed temperature is less than 80°C, the fault is eliminated. Otherwise, proceed to the next step.

[0012] Step (6) If the temperature is between 80°C and 100°C, turn the bearing by hand to check whether the bearing can rotate freely and smoothly. If it is stuck or not flexible, replace the bearing and repeat the above step (5). Otherwise, proceed to the next step.

[0013] Step (7) Check the installation status of the bearing, fix the runout meter on the aircraft platform, and detect the end face runout values ​​of the inner and outer rings of the bearing. If there is no abnormality, proceed to the next step. Otherwise, reinstall and adjust the bearing to meet the requirements, and verify according to the above step (5);

[0014] Step (8) Check whether the tail shaft vibration value and the runout of the laminated coupling meet the requirements of the helicopter installation manual. After ensuring that there is no abnormality, re-attach the temperature indicator and detect the bearing temperature. If the temperature is still between 80°C and 100°C, proceed to the next step;

[0015] Step (9) Remove the tail shaft bearing from the spline joint, measure the inner ring diameter of the bearing and the diameter of the spline joint matching the inner ring of the tail shaft bearing, and then calculate the radial clearance value of the bearing after assembly. If the radial clearance value is less than 0 mm, replace the spline joint with a smaller outer diameter or replace the tail shaft bearing with a larger radial clearance, otherwise proceed to the next step;

[0016] Step (10) Check the installation status of the bearing seat, and check the installation coaxiality of the tail shaft bearing seat according to the installation requirements of the helicopter manual. If there is no abnormality, proceed to the next step. Otherwise, reinstall and adjust the bearing seat until it is qualified and then verify it;

[0017] Step (11) checking the temperature of the cabin around the tail shaft, that is, attaching temperature indicating plates at corresponding positions in the tail shaft cabins of the faulty helicopter and the normal helicopter, driving the helicopter on the ground with an empty load for at least 30 minutes under the same conditions, and then observing the temperature indicating plate values ​​of the cabins of the two helicopters. If the cabin temperature of the faulty helicopter is higher than that of the normal helicopter, the reason for the high temperature of the tail shaft bearing is abnormal engine operation or poor heat dissipation conditions in the cabin, otherwise proceed to the next step;

[0018] Step (12) Check whether there is any abnormality in the connection position between the tail shaft and the reducer mounting platform. If there is any abnormality, reinstall and adjust the tail shaft to meet the requirements and verify it. Otherwise, proceed to the next step.

[0019] Step (13) Check whether the helicopter tail boom is deformed. If there is a large deformation, repair it and re-verify it until the fault is eliminated.

[0020] Furthermore, the purpose of step (3) under the same period and operating time conditions is to ensure that the ground ambient temperature and the bearing operating time are consistent when troubleshooting. At this time, the temperature displayed by the temperature indicator will be a direct reflection of the actual status of the two aircraft, which is conducive to the investigation of the cause of the fault.

[0021] Furthermore, the step (5) of driving the vehicle on the ground with an empty mantle load for at least 30 minutes is mainly to simulate the load condition of a helicopter flying in the air. The 30-minute operation time is to ensure that the lubricating grease can be evenly covered on the surfaces of each roller of the bearing. At the same time, this time can ensure that the bearing can go through the three complete stages of rapid bearing temperature rise, gentle temperature rise, and stable temperature, and the temperature indicator can collect the highest bearing temperature;

[0022] Furthermore, if the temperature in step (5) is lower than 80°C, the fault is eliminated based on the operating conditions of the tail shaft and the internal parameters of the bearing.

[0023] Furthermore, the runout table in step (7) is required to be fixed on a flat surface of the aircraft platform in order to ensure the accuracy of the measured values. According to experience, the runout value of the inner ring of the bearing is usually required to be no more than 0.05 mm, and the runout value of the outer ring is required to be no more than 0.10 mm. If the runout is greater than the above values, it will affect the stability of the bearing operation and cause abnormal bearing temperature.

[0024] Furthermore, the temperature in step (8) is between 80°C and 100°C. This is mainly because the normal operating temperature range of the bearing under this working condition is usually below 80°C. Temperatures above 80°C may cause problems to a greater or lesser extent and require further investigation.

[0025] Furthermore, if the radial clearance value in step (9) is less than 0 mm, the lubricating oil film will not be fully formed, and the friction between the bearing rollers and the raceways will increase, thereby causing the bearing temperature to rise.

[0026] Furthermore, the step (10) requires checking the installation coaxiality of the bearing seat in order to exclude the possibility of large local bearing stress after the installation of several shaft sections. If this happens, the bearing temperature will rise abnormally.

[0027] Furthermore, there are two measures to control the ambient temperature of the bearing in step (11): one is to control the heat source generated by the engine, such as controlling the temperature and injection direction of the engine tail nozzle; the other is to improve the ventilation conditions in the cabin.

[0028] The beneficial effects of this application are:

[0029] The present invention avoids the situation of inaccurate bearing temperature detection by stipulating two range specifications of A and B and the sticking position, which leads to the failure to solve the high bearing temperature problem in time. The method of keeping the aircraft platform unchanged and directly interchangeably assembling the tail shafts of the two aircraft can quickly lock the main influencing factors of the high bearing temperature problem, which is conducive to the rapid troubleshooting of faults. By stipulating the ground start-up verification working conditions and operating time, the actual working temperature of the bearing can be accurately collected, and the influence of other additional factors is effectively eliminated. By clarifying the critical value of the normal working temperature of the bearing, it can be used as a basis for judging the fault. Based on practical experience, the minimum radial clearance value after the product combination is assembled and the range of the ambient temperature in the cabin are given, providing a solution to the high temperature problem of the tail shaft bearing. The last step is to check the cumbersome helicopter installation platform and the deformation of the tail beam, which can effectively reduce the helicopter grounding time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the structural diagram of the helicopter tail shaft bearing.

[0031] Figure 2 This is a structural diagram of the tail shaft bearing installed on the tail shaft.

[0032] Figure 3 Flow chart for troubleshooting high temperature of tail shaft bearing

[0033] Figure 4 This is a schematic diagram of the temperature indicator with A and B range specifications.

[0034] Figure 5 This is a diagram showing the location of the temperature indicator sticking to the tail shaft.

[0035] Figure 6 This is the end face runout measurement table and the laminated coupling runout measurement diagram. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the technical scheme in the embodiment of the present invention will be described in more detail in combination with the embodiment of the present invention. In the example, the same or similar reference numerals throughout represent the same or similar originals or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of them. The embodiments described below by reference are exemplary and intended to be used to explain the present invention, and should not be construed as limitations on the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention. The following is a detailed description in combination with the embodiments of the present invention.

[0037] The troubleshooting process for high temperature of helicopter tail shaft bearing is attached. Figure 3 , the specific method includes the following steps:

[0038] (1) Before troubleshooting, prepare temperature indicators of two ranges, A and B (see attached). Figure 4 ), check whether the temperature indicator is within the validity period, confirm whether the temperature indicator has turned black, and proceed to the next step if there is no abnormality, otherwise replace the temperature indicator;

[0039] (2) Keeping the aircraft platform unchanged, swap the tail shaft of the faulty aircraft with the tail shaft of another normal aircraft. That is, install the tail shaft with the high-temperature bearing on the helicopter platform with normal bearing temperature, and install the tail drive shaft with normal bearing temperature on the faulty helicopter platform.

[0040] (3) Carry out ground start-up verification under the same period and operating time conditions. If the temperature of the original high-temperature bearing is still high or the temperature of the original normal-temperature bearing is still normal, it means that the original high temperature of the tail shaft bearing is mainly affected by the tail shaft itself. Therefore, it is necessary to conduct a detailed investigation of the tail shaft factors according to steps (4), (5), (6), (7), (8), and (9). If the temperature of the original high-temperature bearing turns normal or the temperature of the original normal-temperature bearing is high, it means that the original high temperature of the tail shaft bearing is mainly affected by the helicopter platform. Therefore, it is necessary to check the helicopter platform according to steps (10), (11), (12), and (13).

[0041] (4) Open the helicopter tail shaft protection cover and check whether the bearing with high temperature has grease leakage, seal wear, inflexible rotation, abnormal noise, etc. If no abnormality is found, proceed to the next step. Otherwise, replace the bearing and verify it according to the following steps;

[0042] (5) Re-attach the temperature indicator (see attached) Figure 5 ), start the car on the ground with empty mantle load for at least 30 minutes, and observe the temperature value after the start-up. If the displayed temperature is less than 80℃, the fault is eliminated, otherwise proceed to the next step;

[0043] (6) If the temperature is between 80°C (inclusive) and 100°C (inclusive), turn the bearing by hand to check whether the bearing can rotate freely and smoothly. If it is stuck or not flexible, replace the bearing and repeat the above step (5). Otherwise, proceed to the next step.

[0044] (7) Check the installation status of the bearing and set the runout table (see attached Figure 5 ) is fixed on the aircraft platform, and the end face runout values ​​of the inner and outer rings of the bearing are detected. If there is no abnormality, proceed to the next step. Otherwise, reinstall and adjust the bearing to meet the requirements, and verify according to the above step (5);

[0045] (8) Check the vibration value of the tail shaft and the runout of the laminated coupling (see Appendix Figure 6) Check whether it meets the requirements of the helicopter installation manual. After ensuring that there is no abnormality, re-stick the temperature indicator and check the bearing temperature. If the temperature is still between 80℃ (including 80℃) and 100℃ (including 100℃), proceed to the next step;

[0046] (9) Remove the tail shaft bearing from the spline joint, measure the inner ring diameter of the bearing and the diameter of the spline joint that matches the inner ring of the tail shaft bearing, and then calculate the radial clearance value of the bearing after assembly. If the radial clearance value is less than 0mm, replace the spline joint with a smaller outer diameter or replace the tail shaft bearing with a larger radial clearance. Otherwise, proceed to the next step.

[0047] (10) Check the installation status of the bearing seat and test the installation coaxiality of the tail shaft bearing seat according to the installation requirements of the helicopter manual. If there is no abnormality, proceed to the next step. Otherwise, reinstall and adjust the bearing seat until it is qualified and then verify it;

[0048] (11) Check the cabin temperature around the tail shaft (under normal circumstances, the cabin ambient temperature is usually between 40°C and 65°C). That is, stick temperature indicators at the corresponding positions in the tail shaft cabins of the faulty and normal helicopters. Drive the aircraft on the ground with an empty load for at least 30 minutes under the same conditions, and then observe the cabin temperature indicator values ​​of the two aircraft. If the cabin temperature of the faulty aircraft is higher than that of the normal aircraft, the high temperature of the tail shaft bearing is caused by abnormal engine operation or poor cabin heat dissipation conditions. Otherwise, proceed to the next step.

[0049] (12) Check whether there is any abnormality in the connection between the tail shaft and the reducer mounting platform. If there is any abnormality, reinstall and adjust the tail shaft until it is qualified and verify it. Otherwise, proceed to the next step.

[0050] (13) Check whether the helicopter tail boom is deformed. If there is a large deformation, repair it and re-verify it until the fault is eliminated.

[0051] In a certain implementation case of the present invention, the step (1) specifies two ranges of temperature indicating strips (also called thermal test papers, which may also be replaced by other brands) A and B mainly because the operating temperature range of the helicopter tail shaft bearing is roughly between 40°C and 100°C. The use of two ranges of temperature indicating strips can accurately measure the actual maximum operating temperature of the bearing, avoiding the situation where the small range temperature indicating strip has an excessive value or the large range temperature indicating strip has no display value.

[0052] In a certain implementation case of the present invention, the step (2) of keeping the aircraft platform unchanged is mainly to avoid other factors introduced by humans and affecting the final determination of the cause of the high bearing temperature problem.

[0053] In a certain implementation case of the present invention, the step (3) is mainly to ensure that the ground ambient temperature and the bearing operation time are consistent during troubleshooting under the same time period and the same operating time conditions. At this time, the temperature presented by the temperature indicator will be a direct reflection of the actual status of the two machines, which is conducive to the investigation of the cause of the fault.

[0054] In a certain implementation case of the present invention, the step (5) of driving the bearing on the ground with an empty mantle load for at least 30 minutes is mainly to simulate the load condition of a helicopter flying in the air. The 30-minute operation time is to ensure that the lubricating grease can be evenly covered on the surfaces of each roller of the bearing. At the same time, this time can ensure that the bearing can go through the three complete stages of rapid bearing temperature rise, gentle temperature rise, and stable temperature, and the temperature indicator can collect the highest bearing temperature;

[0055] In a certain implementation case of the present invention, if the temperature in step (5) is lower than 80°C, the fault elimination is mainly determined based on the working condition of the tail shaft and the internal parameters of the bearing.

[0056] In a certain embodiment of the present invention, the runout table in step (7) is required to be fixed on a flat surface of the aircraft platform, mainly to ensure the accuracy of the measured value. According to experience, the runout value of the inner ring of the bearing is usually required to be no more than 0.05mm, and the outer ring is required to be no more than 0.10mm. If the runout is greater than the above values, it will affect the stability of the bearing operation and cause abnormal bearing temperature.

[0057] In a certain implementation case of the present invention, the temperature in step (8) is between 80°C and 100°C. This is mainly due to the fact that the normal operating temperature range of the bearing under this working condition is usually below 80°C. Temperatures above 80°C may cause some problems and require further investigation.

[0058] In a certain embodiment of the present invention, if the radial clearance value in step (9) is less than 0 mm, the lubricating oil film will not be formed sufficiently, and the friction between the bearing rollers and the raceways will increase, thereby causing the bearing temperature to rise.

[0059] In a certain implementation case of the present invention, the step (10) requires checking the installation coaxiality of the bearing seat mainly to rule out whether there is a situation where local bearing stress is large after several shaft sections are installed. If this situation exists, the bearing temperature will rise abnormally.

[0060] In a certain implementation case of the present invention, the step (11) requires checking the cabin temperature around the tail shaft mainly because heat is generated during the operation of the bearing. Under normal circumstances, the cabin temperature is usually between 40°C and 65°C. If the ambient temperature is too high, the heat of the bearing cannot be dissipated in time, resulting in a high bearing temperature. There are two main measures to control the ambient temperature around the bearing. One is to control the heat source generated by the engine, such as controlling the temperature and spray direction of the engine tail nozzle; the other is to clear the ventilation conditions in the cabin, such as adding vents on the helicopter aircraft skin, and reasonably arranging and installing helicopter cabin products.

[0061] In a certain implementation case of the present invention, the work in steps (12) and (13) involves the inspection of the entire helicopter platform. The workload of parameter detection is extremely large and difficult to detect. Therefore, when checking, it is necessary to be particularly careful to perform the inspection according to the requirements of the relevant chapters of the helicopter installation manual. After completing one inspection, the data must be analyzed in a timely manner to discover problems as early as possible, avoid meaningless inspections, and reduce the helicopter's downtime.

[0062] The temperature of the tail shaft bearing of a certain type of helicopter reaches 99°C. The troubleshooting steps for this fault are as follows:

[0063] (1) Before troubleshooting, prepare temperature indicators of two range specifications, A and B. If the temperature indicators are within the validity period and have not turned black, proceed to the next step;

[0064] (2) Keeping the aircraft platform unchanged, swap the tail shaft of the faulty aircraft with a bearing temperature of 99°C with the tail shaft of another aircraft with a normal temperature (65°C);

[0065] (3) At 2:00 p.m. on July 13, 2023 (weather forecast temperature 31°C), two aircraft were started and shut down at the same parking dam, with a cumulative operating time of 40 minutes. After checking the temperature indicator, it was found that the temperature of the bearing, which was originally 99°C, dropped to below 71°C, and the bearing temperature, which was originally 65°C, rose to above 93°C. This shows that the original high temperature problem of the tail shaft bearing is mainly affected by the helicopter platform. Therefore, the helicopter platform needs to be inspected according to steps (10), (11), (12), and (13);

[0066] (10) Check the installation coaxiality of each tail shaft bearing seat according to the installation requirements of the helicopter manual, and find no abnormality;

[0067] (11) Check the temperature of the cabin around the tail shaft, and paste temperature indicators at the corresponding positions in the tail shaft cabin of the faulty and normal helicopters. At 2:30 pm on July 14, 2023 (weather forecast temperature 32°C), on the same parking dam, the two aircraft started and stopped at the same time, with a cumulative operating time of 42 minutes. The values ​​of the temperature indicators in the cabins of the two aircraft were observed. The cabin temperature of the faulty aircraft was 18°C ​​higher than that of the normal aircraft. Therefore, the high temperature of the tail shaft bearing was caused by abnormal engine operation or poor heat dissipation conditions in the cabin. Further inspection found that the injection direction of the tail nozzle of the faulty aircraft differed by 10° from the normal installation position, that is, the injection direction of the engine was closer to the tail shaft bearing position. Finally, the engine was reinstalled for verification, and the original 99°C temperature of the tail shaft bearing of the faulty aircraft dropped to normal, and the fault was eliminated.

[0068] It is understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of ordinary technicians in the field to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and unless defined as here, will not be interpreted with idealized or overly formal meanings. The specific implementation methods described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Within the spirit and principle of the present invention, any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment of equivalent changes for application in other fields, but any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution content of the present invention, any modification, equivalent replacement, improvement, etc., made according to the technical essence of the present invention, should be included in the protection scope of the present invention.

Claims

1. A method for troubleshooting high temperature of a helicopter tail drive shaft bearing, characterized in that: By specifying temperature indicator sheets with two range specifications of A and B and their sticking positions, and adopting the method of keeping the aircraft platform unchanged and directly interchangeably assembling the tail shafts of the two aircraft, the main influencing factors of the high bearing temperature problem can be quickly identified. By specifying the ground start-up verification conditions and operating time, the actual working temperature of the bearing can be accurately collected. By clarifying the critical value of the normal working temperature of the bearing, it can be used as a basis for fault judgment. Based on practical experience, the minimum radial clearance value after the product combination is assembled and the range of the ambient temperature in the cabin are given, providing a solution to the high temperature problem of the tail shaft bearing.

2. The method according to claim 1, characterized in that The following steps are involved: Step (1) Before troubleshooting, prepare two temperature indicator sheets of A and B range specifications, check whether the temperature indicator sheets are within the validity period, and confirm whether the temperature indicator sheets have turned black. If there is no abnormality, proceed to the next step, otherwise replace the temperature indicator sheets; Step (2) keeping the aircraft platform unchanged, swapping the tail shaft of the faulty aircraft with the tail shaft of another normal aircraft, that is, installing the tail shaft with the high-temperature bearing on the helicopter platform with normal bearing temperature, and installing the tail transmission shaft with normal bearing temperature on the faulty helicopter platform; Step (3) performs ground start-up verification under the same period and the same operating time conditions. If the temperature of the original high-temperature bearing is still high or the temperature of the original normal-temperature bearing is still normal, it means that the original high temperature of the tail shaft bearing is mainly affected by the tail shaft itself. Therefore, it is necessary to conduct a detailed investigation of the tail shaft factors according to steps (4)-(9); if the temperature of the original high-temperature bearing turns normal or the temperature of the original normal-temperature bearing is high, it means that the original high temperature of the tail shaft bearing is mainly affected by the helicopter platform. Therefore, it is necessary to check the helicopter platform according to steps (10)-(13); Step (4) Open the helicopter tail shaft protection cover and check whether the high-temperature bearing has grease leakage, seal wear, inflexible rotation, or abnormal noise. If no abnormality is found, proceed to the next step. Otherwise, replace the bearing and verify according to the following steps; Step (5) Re-attach the temperature indicator sheet and drive the vehicle on the ground with an empty mantle load for at least 30 minutes. After the operation is completed, observe the value of the temperature indicator sheet. If the displayed temperature is less than 80°C, the fault is eliminated. Otherwise, proceed to the next step. Step (6) If the temperature is between 80°C and 100°C, turn the bearing by hand to check whether the bearing can rotate freely and smoothly. If it is stuck or not flexible, replace the bearing and repeat the above step (5). Otherwise, proceed to the next step. Step (7) Check the installation status of the bearing, fix the runout meter on the aircraft platform, and detect the end face runout values ​​of the inner and outer rings of the bearing. If there is no abnormality, proceed to the next step. Otherwise, reinstall and adjust the bearing to meet the requirements, and verify according to the above step (5); Step (8) Check whether the tail shaft vibration value and the runout of the laminated coupling meet the requirements of the helicopter installation manual. After ensuring that there is no abnormality, re-attach the temperature indicator and detect the bearing temperature. If the temperature is still between 80°C and 100°C, proceed to the next step; Step (9) Remove the tail shaft bearing from the spline joint, measure the inner ring diameter of the bearing and the diameter of the spline joint matching the inner ring of the tail shaft bearing, and then calculate the radial clearance value of the bearing after assembly. If the radial clearance value is less than 0 mm, replace the spline joint with a smaller outer diameter or replace the tail shaft bearing with a larger radial clearance, otherwise proceed to the next step; Step (10) Check the installation status of the bearing seat, and check the installation coaxiality of the tail shaft bearing seat according to the installation requirements of the helicopter manual. If there is no abnormality, proceed to the next step. Otherwise, reinstall and adjust the bearing seat until it is qualified and then verify it; Step (11) checking the temperature of the cabin around the tail shaft, that is, attaching temperature indicating plates at corresponding positions in the tail shaft cabins of the faulty helicopter and the normal helicopter, driving the helicopter on the ground with an empty load for at least 30 minutes under the same conditions, and then observing the temperature indicating plate values ​​of the cabins of the two helicopters. If the cabin temperature of the faulty helicopter is higher than that of the normal helicopter, the reason for the high temperature of the tail shaft bearing is abnormal engine operation or poor heat dissipation conditions in the cabin, otherwise proceed to the next step; Step (12) Check whether there is any abnormality in the connection position between the tail shaft and the reducer mounting platform. If there is any abnormality, reinstall and adjust the tail shaft to meet the requirements and verify it. Otherwise, proceed to the next step. Step (13) Check whether the helicopter tail boom is deformed. If there is a large deformation, repair it and re-verify it until the fault is eliminated.

3. The method according to claim 2, characterized in that The purpose of step (3) under the same period and operating time conditions is to ensure that the ground ambient temperature and the bearing operating time are consistent when troubleshooting. At this time, the temperature displayed by the temperature indicator will be a direct reflection of the actual status of the two aircraft, which is conducive to the investigation of the cause of the fault.

4. The method according to claim 3, characterized in that The main purpose of step (5) of driving the bearing on the ground for at least 30 minutes with an empty mantle load is to simulate the load condition of a helicopter flying in the air. The 30-minute operation time is to ensure that the lubricating grease can be evenly covered on the surfaces of each roller of the bearing. At the same time, this time can ensure that the bearing can go through the three complete stages of rapid bearing temperature rise, gentle temperature rise, and stable temperature, and the temperature indicator can collect the highest bearing temperature.

5. The method according to claim 4, characterized in that If the temperature in step (5) is lower than 80°C, the fault is eliminated based on the tail shaft operating conditions and the internal parameters of the bearing.

6. The method according to claim 5, characterized in that The runout table in step (7) is required to be fixed on a flat surface of the aircraft platform in order to ensure the accuracy of the measured values. According to experience, the runout value of the inner ring of the bearing is usually required to be no more than 0.05mm, and the outer ring is required to be no more than 0.10mm. If the runout is greater than the above values, it will affect the stability of the bearing operation and cause abnormal bearing temperature.

7. The method according to claim 6, characterized in that The temperature in step (8) is between 80°C and 100°C. This is mainly because the normal operating temperature range of the bearing under this working condition is usually below 80°C. Temperatures above 80°C may cause problems and require further investigation.

8. The method according to claim 7, characterized in that If the radial clearance value in step (9) is less than 0 mm, the lubricating oil film will not be fully formed, and the friction between the bearing rollers and the raceways will increase, thereby causing the bearing temperature to rise.

9. The method according to claim 8, characterized in that The purpose of step (10) to check the installation coaxiality of the bearing seat is to rule out the possibility of large local bearing stress after the installation of several shaft sections. If this happens, the bearing temperature will rise abnormally.

10. The method according to claim 9, characterized in that There are two measures to control the ambient temperature of the bearing in step (11). One is to control the heat source generated by the engine, such as controlling the temperature and injection direction of the engine tail nozzle; the other is to improve the ventilation conditions in the cabin.

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