Written by David Algie. Posted in ACA3


The throttle in the ACA is a single power lever. There are no prop or mixture controls. Since the throttle lever is acting on a rotary sensor, it's motion is much smoother than a throttle using a cable. The system has safety routines like ice break mode, if ice is detected to be holding the throttle plate open, it will attempt to break it. As the engine develops more power than can be handled on the ground, the system senses gear squat and reduces available power a small amount until airborne.

prop controll   The ACA features an electronically controlled hydraulic constant Mach propeller. This lightens pilot workload, and increases aircraft climb performance. The system is fully automatic, sensing throttle position, air density, and RPM . Over 70% throttle it goes into constant Mach, under that and it divides up the power setting to prop RPM. In the event of engine failure, the propeller automatically feathers. The ECU has sensors to prevent the propeller from feathering during commanded engine shutdowns.
One of the specific features of the ACA is it's sea level cabin comfort up to FL290. This is unheard of in other aircraft, and presents unique requirements in the systems and design of the ACA. Pressurization pressure is supplied from the engine normalizing system, which keeps the engine operating at sea level conditions. A single outflow valve is utilized that incorporates an internal over-pressure (Max. Diff.) relief, and defaults to a closed position to hold cabin pressure in the event of engine failure. When gear squat is sensed on the ground the system moves to equalize the cabin pressure to local pressure.


The ACA features a 3-axis trim system with rudder trim, with each trim servo unit completely concealed from the airstream with no exposed pushrods or control horns, giving a very clean design. Trim position is indicated on the dash LCD, and can be controlled from a joystick mounted "coolie hat".


The trim system is also part of the autopilot system, or AFCS (Automatic Flight Control System). The basic autopilot is an attitude hold system, with controls for pitch and roll. A TCS (Touch Control Steering) button allows the aircraft to be maneuvered to a new attitude with the autopilot engaged. The flight director control head allows various navigation modes to be selected.

  • TRK - Heading hold
  • ALT - Altitude hole
  • GPS NAV - Follow preprogrammed course
  • GPSS - Same as GPS NAV but anticipates waypoints and steers early to provide smooth transitions
  • V NAV and/or V GPS

The above listed modes are being evaluated as aircraft navigation is currently advancing at a rapid pace. GPS is advancing to become a sole means of navigation, and the FAA has a phase out schedule for VOR and ILS systems.



The flaps are a long travel fowler type, and driven by stepper motors that check for synch on startup each time. Flap position and status are indicated on the LCD. Initial flap slot opening is used for air brake. A single touch button moves the flaps to their next position, or up again. The system also interfaces with the trim system, to provide automatic pitch trim due to pitch moment changes from using the flaps.


EICAS Notes:

Faults which might self clear:

    • no command

Faults able to be reset in flight

    • Controller fault
    • PDU fault
    • Command error

Faults only able to be reset on the ground:

    • Position faults

Position faults X out flap indication on EICAS