Gents, a short message, I expect visitors.

Ed was one of the known modelers who did a lot of research with a the thick wing (of the Taurus) to reduce the speed of the plane in vertical downwards going maneuvers.
I do design my equipment to make one more step to maintain constant speed and I did tell this before.

Now there maybe is some doubt I can use the propeller as a brake.
That’s the reason of this short story.

My roots were in Heer-Hugowaard a “polder” in The Netherlands, true but.

WARNING A JOKE,

Jan Adriaensz Leeghwater (1575-1650) was born in De Rijp and was able to show the world the bottom of the sea using propellers and wind energy. One of the biggest problems is the environmental effects, because of the brake power these windmills were generating, the speed of rotation of the globe has been reduced in 100 years (were did I read 100 years before?). Our days are 1 % longer for us than for Wilbur and Orville Wright,
So when we can use the propeller as a brake for the world, why not for such a little plane?

BTW The distance between Heer-Hugowaard and is De Rijp 22,6 km, 14 miles, so you see small country!

BUT TRUE
Yes, we are able to use the propeller as a brake.

What to do?

Always the angle of attack has to be within the limits to prevent stall, stall during propulsion, stall during braking. To have a usable brake range-ability, it is better to use (more) symmetrical airfoils. You cannot buy them, have to make them.
To prevent stall the airspeed controller system has to be designed to do the job.
Several tricks are known in my profession to use in these systems, mostly too complicated to explain.

The easy way to explain the stall function is saying:
You also can fly inverted, only using an asymmetrical airfoil for that does make the wing stall easier so that's not clever, also to prevent stall in inverted flight you have to maintain a certain flight speed, so to brake you have to maintain a certain revs of the engine compare with the measured flight speed, so a controlled negative AOA of the prop.

For me is extra

Controlling the "appearance" of constant speed flying F3A is relatively easy . . we have a throttle stick . It's the manoeuvres that give us trouble . As for the constant speed on vertical down lines . . I believe it is really about motor and prop choices, AND
induced drag designed into the airframe.

like using an activated parking brake while trying to maintain a controlled speed by using a manual throttle powered car, driving downhill.

So for sure not a constant speed.
When you do not understand this? Let not make the know how of Leeghwater be my problem!
Think about this, the next step can be reload the brakepower in the battery, that's possible with a varable speed drive.

BTW: When you use electrical propulsion the constant speed (rpm, brussless!!!) of the propeller can result in a proportional controlled speed within the stall limits of the rotating prop, so not bad but not perfect (loadfactor!) . When you have to add engine power to go downwards also this proportional control loop is history.
Cees