全許可權數字發動機控制器(Full Authority Digital Engine Control)FADEC,是相對於傳統的發動機液壓控制系統來說的。傳統的液壓控制系統實現控制規律算法主要依靠凸輪的空間曲面來完成,而這個空間曲面構型製造比較困難,因而液壓控制系統控制精度不高。FADEC實現控制規律算法則簡單的多,只需把公式變成代碼進行處理即可,因而控制精度要高很多。
A typical civilian transport aircraft flight may illustrate the function of a FADEC. The flight crew first enters flight data such as wind conditions,runwaylength, or cruise altitude, into theflight management system(FMS). The FMS uses this data to calculate power settings for different phases of the flight. At takeoff, the flight crew advances the throttle to a predetermined setting, or opts for an auto-throttle takeoff if available. The FADECs now apply the calculated takeoff thrust setting by sending an electronic signal to the engines; there is no direct linkage to open fuel flow. This procedure can be repeated for any other phase of flight.
In flight, small changes in operation are constantly made to maintain efficiency. Maximum thrust is available for emergency situations if the throttle is advanced to full, but limitations can’t be exceeded; the flight crew has no means of manually overriding the FADEC
True full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer. If a total FADEC failure occurs, the engine fails. If the engine is controlled digitally and electronically but allows for manual override, it is considered solely an EEC orECU. An EEC, though a component of a FADEC, is not by itself FADEC. When standing alone, the EEC makes all of the decisions until the pilot wishes to intervene.
FADEC works by receiving multiple input variables of the current flight condition includingair density, throttle lever position, engine temperatures, engine pressures, and many other parameters. The inputs are received by the EEC and analyzed up to 70 times per second. Engine operating parameters such as fuel flow, stator vane position,bleed valveposition, and others are computed from this data and applied as appropriate. FADEC also controls engine starting and restarting. The FADEC's basic purpose is to provide optimum engine efficiency for a given flight condition.
FADEC not only provides for efficient engine operation, it also allows the manufacturer to program engine limitations and receive engine health and maintenance reports. For example, to avoid exceeding a certain engine temperature, the FADEC can be programmed to automatically take the necessary measures without pilot intervention.