Acro with an MT Electric Prop

Discussion in 'Aerobatics' started by StonewallH, Dec 26, 2019.

  1. StonewallH

    StonewallH Filing Flight Plan

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    I need advice on be best way to operate an Mt electric prop in order to avoid over speeds. Referencing the manual...

    For go arounds high airspeeds should be avoided because an overspeed may occur. The rate of pitch change is only 1°/sec and therefore slower than with hydraulic constant speed propellers. It is recommended to reduce airspeed to the best rate of climb speed before take off power is set.

    The same thing will happen in a loop. If I have full throttle set and 2500 rpm in auto mode, as the airspeed decreases over the top the blades adjust to hold that rpm, so as the airspeed increases on the backside it can quickly over speed unless i keep the power all the way back at idle. It is difficult to do another maneuver back to back because I have to wait for the pitch to change back in order to push the throttle up.

    Would it be better to just switch to manual at the loop entry airspeed 140-160 at 2500 rpm? Does it just act like a fixed blade prop at that point? What would happen over the top as the airspeed decreases to 70 kts?
     
  2. Tarheelpilot

    Tarheelpilot Ejection Handle Pulled

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    Reduce throttle until it catches up ??
     
  3. StonewallH

    StonewallH Filing Flight Plan

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    That is how I currently operate it, trying to see if anyone has any experience in manual mode or does anything different
     
  4. Tarheelpilot

    Tarheelpilot Ejection Handle Pulled

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    I was just guessing because I have no experience behind that prop. Good luck. I’m sure someone here will know or at least pretend to know.
     
  5. FORANE

    FORANE Pattern Altitude

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    I have a MT electric prop on the plane in my avitar. I only run it in manual mode, for all operations 100% of the time it is running. I have the P-120-U controller. While I don't fly aerobatics, I understand the prop and what you are faced with in doing a loop.

    Yes, to answer your question, if you switch to manual mode it becomes a fixed pitch prop. However, in manual mode you may still adjust that pitch in flight with the toggle switch on the controller.

    Do you know your static RPM when at the manual mode takeoff position fine pitch stop limit? I adjusted mine so it isn't up at 2700 or so, down to around 2500 or so. I find I really don't need the added thrust as the plane gets there quickly and the slight change really helps prevent a tendency to bump up against an overspeed event on takeoff. Also limits afterfire when going fine pitch in the pattern and using the prop as a brake.

    If you fly your loop in manual mode you could control blade pitch (and change pitch in anticipation of need) better than in auto mode. I think you will still need to use the throttle when doing this, but manual mode should help.

    I would start by determining your static RPM when at the manual mode takeoff position fine pitch stop limit. If it is above 2600, you should expect to quickly need to pitch out manually (during takeoff roll) if taking off in the manual position. If changing to manual mode at altitude, the prop should just stay at the pitch it was at the time you changed modes.
     
  6. Jeff767

    Jeff767 Pre-takeoff checklist

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    Be aware that running a engine below the rated takeoff RPM decreases your detonation margin. That is why most engine manuals require full rated RPM for takeoff.
     
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