Carl's 4-Place Bearhawk

1-12-2021

Electric Flaps - Pt 2

After exploring all aspects of both the manual overhead flap system and the electric flap system, I found there were some negative points to both systems. These issues came down to a large metal tube sticking into the cabin that could become a hazard with the overhead flaps, and the speed of flap deployment with electric flaps. 

After a lot of consideration, I decided to install the electric flaps if it was at all feasible and could meet the following requirements:

1) Must be easy to use in flight

2) Must add a minimum weight to aircraft over existing manual flap system components

3) Must have deployment speeds comparable to manual deployment

4) Must be controllable through the VP-X Sport.

The basic arquitecture was simple to envision, essencially locate the actuator in the ceiling area above the pilot and attach it to a crosstube spanning the cabin which in turn would be attached to the existing flap levers in the wing roots via a linkeage with rod-ends.

I used a formula to calculate the necessary lever length versus flap lever lengths to determine which actuator would meet my speed requirements. I settled on the PA-04 actuator from Progressive Automations with a 400 lbs load capacity and traveling at 0.78"/sec. By selecting a 2" input lever (at actuator) I can achieve a flap deployment speed of 1.6"/sec. at the flap lever at full load. A rough calculation shows my deployment speed between each "notch" should be 0.9"/sec. I find that speed quite acceptable.

The problem I ran into next involved the current draw at full load which was 12 amps. My VP-X circuit was limited to 10 amps. After some research and consultation with Bob Nuckoll, he graciously provided a schematic using two SPDT relays to solve this problem.

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