In order to ensure the safe flight of aircraft under the ice weather conditions, the atmospheric data probe usually has the function of heating and deicing, and is controlled by the air data Heater Controller. In this paper, a design scheme of air data heating controller is presented, and its rationality and superiority are demonstrated by comparing the relevant models. Civil aircraft need to be able to fly safely in the freezing weather specified in Appendix C of FAR25. In order to verify the conformity of the atmospheric data system to the provisions of 25.
1323 (i), 25.1325 (b) and 25.1326, the atmospheric data probe should have the function of heating and deicing, and be controlled by the atmospheric data heating controller. In this paper, a design scheme of air data heating controller is presented, and its rationality and superiority are demonstrated by comparing the relevant models. FAR25.1323 (i) requires that “each airspeed indication system must be equipped with a heated airspeed tube or equivalent means to prevent failure due to icing. FAR25.1325 (b) requires that “when the aircraft encounters the continuous or discontinuous maximum icing state specified in Appendix C of this Part, the relationship between the air pressure in the hydrostatic system and the real external atmospheric static pressure remains unchanged. FAR25.1326 requires that “if there is an airspeed tube heating system equipped with flight instruments, an indication system must be set up to give instructions to the flight crew when the airspeed tube heating system does not work. The design scheme of the air data heating controller is shown in Fig. 1. Input includes ADHC equipment working power supply (28 VDC), TEST power supply (115 VAC, 50 mA), heating power supply (115 VAC, 5A), ON/OFF switching signal and TEST signal. A) The heating controller is in the closed state, relays S2, S3 and S4 are connected 1 and 2, the heating power supply is in the open state, and the load sensor is not heated. B) Control Panel Press TEST button, relay S1 1, 3 connected, sensor heating circuit receives TEST power supply, thermostatic element integrity of external load sensor is checked, through no display, otherwise trigger the corresponding failure alarm, such as PITOT HEAT FAIL, STATIC HEAT FAIL, TAT HEAT FAIL. A) The heating controller is in working state, the relays S2, S 3 and S4 are connected 1 and 3, and the heating power supply is connected. The load sensor is heated.
B) The TEST button is pressed by the control panel, and the TEST does not work at this time. Through ADHC internal circuit, the working current of TEST is only 50 mA, which does not affect the service life of load equipment. The working principle is simple. If the equipment fails, there will be corresponding alarm message prompts to guide maintenance personnel to troubleshoot.
The following is a summary of the air data heating controller schemes for the relevant aircraft. The comparison shows the rationality of the proposed scheme. The A320 uses a heating controller, but monitors the integrity of the sensor only when it is in a heating state. Because the total temperature sensor is not heated on the ground, its integrity can not be known.
The B737 uses a heating controller, but monitors the integrity of the sensor only when it is in a heating state. Usually when the runway is ready to take off, the heating will be turned on.
If the sensor heating fault is found, the aircraft will have to slide back to the parking space. In this paper, a design scheme of air data heating controller is presented, and its rationality and superiority are demonstrated by comparing the relevant models.