What Does a Helicopter Mechanic Do?

The helicopter main reducer has the power input end of the engine and the power output end connected to the rotor and tail rotor attachment drive shaft. It is one of the main transmission components on the helicopter and the most complex, largest and most important component in the transmission.

The development of helicopters for more than sixty years has roughly gone through five generations. The first generation from the late 1930s to the mid 1950s, with wooden hybrid rotors, metal articulated hubs and piston engines as the main features, the maximum flight speed is less than 200 km / h, and the total life of the rotors and the main reducer is low. 600 hours; the second generation from the early 1950s to the mid 1960s, with metal blades and articulated hubs, turboshaft engines, a flying speed of nearly 250 km / h, and a total rotor and main reducer life of 1200 Hours; from the third generation in the mid-1960s to the mid-1970s, the development of FRP blades, bladeless hubs and new turboshaft engines, with a flying speed of nearly 300 km / h, a rotor life of 3600 hours, and a main reducer The total lifespan is 2400, 3600 hours; from the fourth generation of the 1970s to the early 1980s, composite blades and hubs and new turboshaft engines were developed. The flight speed has exceeded 300 km / h. The total life of the main reducer reaches 4500. 6000 hours; from the mid-1980s to the present, bearingless, ball-flexible or hingeless rotor flow is being developed with a maximum flight speed of more than 370 km / h (at sea level The state of the fixed-wing aircraft is up to 510 km / h), and other performances of the helicopter (such as vibration, noise level, weight reduction, increased safety, reliability, main reduced input speed, etc.) have been newly improved, especially The total life of the main reducer has reached 9,000 to 13,500 hours. ^[1]

The working characteristics of the main reducer are

The main reducer is a separate component on the helicopter. It is installed in the reducer compartment at the upper part of the fuselage, and is supported on the body load-bearing structure by a bracket. The main reducer is composed of a casing, a reduction gear, a shaft system and a lubrication system. See the outline and parts of the main reducer of a helicopter (pictured right).

1. The principle and structure of the reducer is universal. It can be scaled down and scaled out according to the proportion of the mainframes of different powers to design its derivative models, reduce the research and development time and costs of subsequent models, and make the design once and for all. ^[2]

The main reducer must be equipped with an independent, autonomous lubrication system to reduce friction and wear on gears and bearing surfaces, prevent overheating, corrosion, scratches, and discharge the wear products through oil circulation. The main reducer lubrication system should ensure reliable lubrication under various working conditions, sufficient heat dissipation, good system sealing, low oil consumption, and easy maintenance and inspection with a metal wear detection and alarm device.

Because it is impossible to use visual inspection and direct detection to check the technical status of the internal parts of the main reducer during use, apart from using space and time personnel, you can judge the slip through the oil temperature and pressure instructions, and the metal chip alarm device in the oil system. Whether the oil system is working properly, the technical status of the reducer parts should also be determined by regularly checking the state of the oil in the reducer, because after the use time has reached the overhaul interval, it should be returned to the factory for overhaul in order to ensure the critical components of the helicopter. The safe and reliable operation of the main reducer. ^[3]

1. Strengthen fault diagnosis and analysis capabilities

For helicopter condition monitoring systems, waveform analysis is mainly used to improve the ability to analyze faults. Time domain analysis and frequency domain analysis are the most common waveform analysis methods. In addition, the application of genetic algorithms, BP neural networks and SVP is often used to diagnose gear faults. For generator faults, discrete wavelet transforms and generalized regression neural networks are used to diagnose faults. At the same time, wavelet packet transforms and wavelet neural networks are used for helicopters. Diagnose the failure of the main reducer. Strengthening the grasp of these fault diagnosis and analysis techniques has an important role in improving the ability of diagnosis and analysis. ^[4]

2.Improve fault prediction capabilities

The failure of the helicopter main reducer is mainly composed of a combination of Kalman filtering, DWT and neural network. Specifically, the vibration signal is collected on the helicopter main reducer using a vibration sensor, and discrete wavelet transform is performed after resampling and removing noise, and then Kalman filtering budget is performed to achieve the ability to predict the failure of the main reducer in advance. At present, it is necessary to strengthen the integration of prediction capabilities and diagnostic capabilities, make full use of diagnostic networks, and achieve the ability to predict signal failures. Predicting faults can avoid wasting resources due to excessive maintenance. Accurately predicting faults is a prerequisite for maintenance, providing a scientific basis for maintenance, and preventing accidents caused by insufficient maintenance, reducing the incidence of accidents. ^[4]

3.Perform regular inspection and maintenance

In order to reduce the failure rate of the main reducer, it is necessary to strengthen the daily maintenance of the main reducer. Regularly check the oil level and leakage of the oil to ensure that the amount of oil meets the requirements. The magnetically blocked oil filter condition of the reducer ensures that the oil is clean and free of metal shavings. Periodic inspections of the oil radiators are also required to ensure the normal operation of the oil cooling device. The power transmission system must also be checked regularly to ensure that the gears can operate normally.The heat transfer nodes of the helicopter main reducer system are divided, and the heat transfer network model is established.The temperature field of the main reducer is analyzed to ensure the main deceleration. The internal temperature of the aircraft is stable, try to eliminate the failure rate of the helicopter's main reducer to ensure flight safety. ^[4]