Originally Posted by
Weads
Referring specifically to the GXi, the FADEC has full control of the engine from idle to fly. With that said how can we manipulate the throttle for emergency situations i.e tail rotor failures, stuck pedals etc. I understand that when the throttle is rolled off it goes to idle 63Ng, but if I slightly reduce throttle will the FADEC keep Nr,Np and Ng at 100% until it gets to a point the fuel flow from the throttle reduction won’t allow the FADEC to keep it at 100%? Thank you in advance!
Yes, that is correct. The following is a quote from the Manufacturers Data.
"1-12-G. IN-FLIGHT AUTO MODE
OPERATION
NOTE
If throttle is not maintained in FLY detent position during normal flight operations, available engine power may be limited. This will occur if throttle is positioned from the FLY detent (PLA 70°) to a setting which is less than 62° PLA.
Although any throttle position from 62° PLA to full open will provide the FADEC with complete control to maintain NR within limits, the approved throttle position for flight is the FLY detent position (PLA 70°).
During flight in AUTO mode with the throttle in FLY detent position (PLA 70°), the FADEC has complete control over engine operation to maintain NR within limits.
The ECU receives engine and airframe parameter inputs and cockpit command signals, processes them, and modulates the HMU stepper motor driven fuel metering valve to achieve desired engine performance.
If required, as may be the case in certain Emergency Procedures, an alternate means of engine control is also available to the pilot in AUTO mode. This can be achieved by manipulating the throttle below FLY detent position until the required engine performance is achieved. As the throttle is positioned between HMU Power Lever Angles of 40 to 62°, electrical signals are sent to the ECU from the HMU-PLA potentiometer. These signals dictate the amount of authority the ECU has to control maximum fuel flow (NG limiting), and in turn, engine NG speed.
Therefore, as throttle is increased or decreased, the maximum NG speed is regulated electrically by limiting the fuel flow."