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  1. #1
    1000+ Poster - Fantastic Contributor Tomlin's Avatar
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    DEEC- Learjet 45 Engine/Speed Mgt. ???

    Are you well versed in the workings of the Lear 45 auto pilot systems? Im really trying to understand how the SPD function works. I understand that the TQ has detents for power settings, but do those detents hold only one setting in the power setting, or is that detent dynamic in that if you begin climbing, the powerplant will respond by adding thrust to maintain that airspeed? Obviously, Im a lot more accustomed to auto-throttle equipped aircraft, and Im confused as to how the DEEC works.

    Any info would be indeed helpful,
    Eric Tomlin-
    Learjet 45 Builder
    www.flightlevel180.org

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    1000+ Poster - Fantastic Contributor Tomlin's Avatar
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    Re: DEEC- Learjet 45 Engine/Speed Mgt. ???

    While doing some research, I found this old post of mine. I now have the answer and wanted to file a correct response in case anyone else has the same question. First off, DEEC and the AP have nothing to do with each other.

    DEEC (Digital Electronic Engine Control) in the LJ45 essentially is a early version of what is now known as FADEC (Full Authority Digital Engine Control).

    The LJ45 has a engine N1 speed limitation schedule that is maintained by DEEC. The physical throttle has detents that the pilot pushes the throttle levers to for various scenarios, i.e. Takeoff, Climb, Cruise. The Takeoff detent provides the highest normal power and calls for the DEEC schedule that basically tells the system the highest N1 speed that is safe for the engine at the altitude, air density, temperature, etc. As the aircraft climbs higher in the atmosphere, the N1 limit increases as far as up to 100%.

    As for auto throttle- The LJ45 doesnt have any such function in real life. The crew maintains the airspeed of the LJ45 via pitch/power and the AP SPD control only works when in a decent/climb mode called SPD and will pitch to maintain the selected forward airspeed value. So, you would pitch the aircraft to climb/descend and once you press SPD, the AP will pitch the aircraft to maintain the forward speed that was present when the SPD mode was selected.

    DEEC/Engines have nothing to do with speed of the aircraft.
    Eric Tomlin-
    Learjet 45 Builder
    www.flightlevel180.org

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  4. #3
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    Re: DEEC- Learjet 45 Engine/Speed Mgt. ???

    Thanks for the update Eric, much appreciated.

    Matt Olieman

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