How did the controls work for variable-pitch props?

Variable-pitch propellers date way back to the 1930's and even earlier. I would like to know, what kind of controls they used? Some kind of lever or crank? How heavy were these controls? I'm thinking of the drag the propeller has, since even near landing, the prop could be spinning very fast and would be resistant to changing it's pitch.

I'm interested in the old days, before modern electrical control by wire.

Note: I am not asking how the variable-pitch mechanisms work. I might ask that in a separate question.

• Related. You may include your current state of research as explained in the help center. Jul 1, 2018 at 9:37
• Why would the propeller be resistant to changing pitch? The blades rotate around axis through their aerodynamic center and the centrifugal force is parallel to that axis, so it does not affect rotation around it either. The only force opposing the control is the feathering spring or counterweight that feathers the propeller in case of failure of the mechanism. Jul 1, 2018 at 21:44
• Note that how the mechanism works determines how the controls may work. So while you may not be asking it, it is still very relevant. Jul 1, 2018 at 21:48
• @JanHudec A feathered propeller has the least drag in a glide, while a normally-pitched prop has the most drag. So there must be an increase in drag if you're changing the blade-pitch to be more "steep". That increase in drag would resist the pitch change just like control surfaces are resistant to deflection. Jul 2, 2018 at 0:42

1 Answer

Control by wire? As in electrically?

Many of the small planes like Cessna Cardinal use an engine like Lycoming O-360 (4 cylinder) use a spring to return the blades to a flat pitch, and engine oil pressure to change the blade pitch. The control knob in the cockpit mechanically allows the oil pressure to change the pitch. In other small planes, like a Bonanza, there is a set of counterweights instead of a spring to accomplish the same. No electric control at all.

• Can you tell me how big is this control knob and how many turns is needed for a change of x angles of blade pitch? Jul 2, 2018 at 11:35
• In Cessnas, it is a knob, maybe 1.5inch in diamater. aircraftspruce.com/pages/ap/cessna_controls/… I unwind it (or pull it out) to increase the pitch until I see 2400 RPM in cruise. Full forward for takeoff. On descent for landing, I work both the RPM and manifold pressure, when finally slow enough on speed the RPMs are driven by the throttle directly and pitch control has no effect, and then the blue knob goes all the way in. I can't say on the number of turns and resulting pitch change. Jul 2, 2018 at 15:30