Analysis of A320 aircraft air conditioning system common faults

During the development of China's civil aviation, the A320 aircraft air-conditioning system frequently broke down, and the failures were repeated and complicated, which brought great inconvenience to the flight crew. In the survey results of China's major airlines, it was found that the number of aircraft air-conditioning system failures has almost reached half of the total number. This paper mainly introduces two common faults of the A320 cabin air conditioning system, which are the cabin temperature is too high and the cabin odor fault. The fault is analyzed comprehensively and the solutions are summarized.

A320 aircraft air conditioning system common faults and solution

1. Cabin temperature is too high

Fault phenomenon

The cabin temperature control system keeps the cabin temperature moderate. When the temperature needs to be adjusted, the hot air mixing system will transmit a certain amount of hot air to the place that needs to be adjusted, so as to achieve the purpose of adjusting the temperature of different areas. There is a cabin temperature rotary button in the air-conditioning menu. We can adjust the temperature by rotating it. Rotate it to 18°C at the far left and 30°C at the far right. If you want to set the temperature to 24°C, you can adjust the rotary button to the middle. . When a fault occurs, the compressor outlet temperature will be greatly increased, and the component outlet temperature will also exceed 90 degrees Celsius. At this time, the air conditioning component will issue a prompt, and the cabin temperature will be greatly increased.

Troubleshooting

The higher the temperature, the more intense the molecular motion, and the presence of stress. In severe cases, the air collecting cavity and the corrugation at the outlet of the heat exchanger will rupture. When they are destroyed, the air cannot be mixed in a normal ratio. After mixing in an abnormal ratio The air will be much higher than normal.

And when the aircraft is flying, once the bellows is damaged, the temperature in the aircraft cabin will rapidly increase, but this phenomenon will not occur on the ground. During the use of the aircraft, many sundries will enter the air intake of the heat exchanger and the air circulation machine, causing serious non-ventilation phenomenon, and the ram air fan cannot work normally, which greatly reduces the wind power of the ram air. The temperature is then increased by the decrease in wind. When the aircraft is flying in the air, the internal pressure is relatively small and the external pressure is relatively large, which will lead to more serious damage to components, greatly increase the amount of gas leakage, and thus affect the temperature adjustment. For the hot air mixing system failure, there is often a single Areas and multiple areas experienced high temperature conditions.

2. The cooling effect of the air conditioner is poor

Failure analysis

Check the maintenance history, there has been no air conditioning failure in recent months, check the current and historical flight segments without failure information, do the temperature control test, and the test has no code. Use APU bleed air for the right assembly to work, check that the air conditioner components, hoses, fittings have no leaks. Checking the last work, according to the maintenance prompt MCC20110715, it has been checked that the inlet screws of the air-conditioning compressor are not loose or lost, the seal here is tight and there is no damage and air leakage, the bypass valve of the right assembly has been replaced, and the sensors 31HH, 20HH, 34HH, and switch ACSC left and right to judge, but the result is that the fault remains the same.

Use APU bleed air for two components to work at the same time, the APU bleed air pressure is normal, the crossover valve can be opened normally, the inlet pressure before the FCV is normal, but the flow rate of the right component is far less than the left component, the compressor outlet temperature of the right component and the turbine The outlet temperatures are all higher than the left assembly, but the right assembly compressor outlet temperature is within the normal range and the turbine outlet temperature is outside the normal range. The single component uses APU bleed air to work, and the FCV inlet pressure indicates 20PSI.

Using the APU alone to work the right component, the flow rate of the right component has increased, and both the compressor outlet temperature and the turbine outlet temperature can be adjusted to within the normal range. The high turbine outlet temperature of the right component is mainly due to the large opening of the bypass valve, which leads to the poor cooling effect of the ACM. Disconnect the electrical plug of the bypass valve of the right component, so that the ACSC2 does not control the bypass valve, the bypass valve is in the fully closed position, the temperature of the turbine outlet of the right component can return to the normal position, and the cooling effect of the ACM is normal.

At this time, the cause of the failure is obvious. The bypass valve is always in the open position because of the control logic failure. Further analysis may be that ACSC2 always opens the bypass valve after receiving an error signal, because the flow rate of the right component FCV is higher than the normal value. Much less, which ultimately results in high turbine outlet temperatures and poor air conditioning cooling. After the flight, the FCV was replaced, and the fault was eliminated.

Troubleshooting Summary and Suggestions

When the two components work at the same time, the opening of the bypass valve of the right component is large, and the single right component works normally. It means that when the two components work, the cabin pressure detected by the differential pressure sensor at the outlet of the left and right components is the same. Since the FCV flow of the right component is quite small, the pressure at the turbine outlet of the right component will also be much less than that of the left component. An abnormal pressure difference will be formed at the outlet, so the rear section of the right assembly turbine just simulates an icing condition, which eventually causes ACSC2 to always open the bypass valve of the right assembly.