Controlling Constant Speed Props

[bok269]

What do you do to increase the RPM and prop angle on a constant speed prop?  It seems to me that since all these controllers are designed with only one throttle for manifold pressure there has to be something I am missing.

[ctjoyce]

Look at CH Products. If you want a real prop stack, their stuff is what you want. All other sticks are designed as if your playing fighter games.

Cheers
Cameron

[bok269]

Yeah I saw that, although it is more than I want to spend on just a throttle.  I figure Ill buy their control panel and program a few of the wheels to the engine speed and the Prop angle.

[ctjoyce]

Or you could just get any stick with multiple rotaries and use those.

Cheers
Cameron

[bok269]

Where could I them standalone (htat just meas multiple throttles, correct)?

[Brett_Henderson]

There are key-board combos for controlling prop-rpm and fuel mixture (you'll have to look them up, or somebody will post them)..  Or you can use your mouse in the cockpit.

Before I got a CH yoke..  I assigned buttons on the joystick too...

[Brett_Henderson]

Just for reference.. engine speed (rpm) and prop-angle are kinda the same thing. You don't select a specific blade angle.. you select an rpm and the blade angle (pitch) changes as you change power (manifold pressure) so that the prop remains at a.... "constant speed"  ;)

[bok269]

[quote]Just for reference.. engine speed (rpm) and prop-angle are kinda the same thing. You don't select a specific blade angle.. you select an rpm and the blade angle (pitch) changes as you change power (manifold pressure) so that the prop remains at a.... "constant speed"

[Brett_Henderson]

I know it's kinda counter-intuitive when you think about a variable-pitch prop as a sort of infinitely variable transmission (that's what I thought it was too). It kind of is but not as flexible as you first think. In other words.. you can't set the engine rpm by throttle and then work your way up through the "gears". In essence, that's what's done but you don't select the gears.. that happens automatically, all the time.

If you set manifold pressure to 25" and prop rpm to 2500 (a very standard cruise setting), what happens is that the hydraulics of the prop are constantly adjusting the pitch to maintain that 2500rpm. If you leave those settings in place and just start climbing, the prop will "downshift" so that rpms remain constant.. and so on.

The

[bok269]

So like a CVT (Continuously variable transmission).

[Brett_Henderson]

Yes...kind of, and yet no. Think of a CVT that would would allow you to go full power up to speed and then, not only let the engine stay at a chosen rpm, but would allow for you to change that rpm without changing throttle setting.

A CVT on a car, snow-mobile or ATV has to allow for extreme vehicle speed changes (including stop and go) and at times, will do it's climbing where there is no low-vehicle-speed limit (where a plane would stall).

If you're cruising along on a CVT vehicle and open up the throttle... the engine will rev higher and THEN the CVT will catch up and you'll go faster. In a constant-speed prop plane, when you open the throttle, the rpms don't change (much)... all that happens is that the pictch changes so that there's more "power" available for say, a climb.

[Brett_Henderson]

I guess another way to look at it is...

[bok269]

Interesting stuff.