Fixed-pitch vs. Constant-speed

[gismo]

Which prop type an airplane has is usually not your choice. You might target buying a plane that has one or the other but the prop type probably won't be important in your decision.

^^^ This.

Very few airplanes offer both a CS and FP prop as an option and for the few that do, the difference in performance is rarely significant. Typically you'll find CS props on airplanes with a larger ratio of cruise vs landing speed and that used to mean retractable gear. CS is also generally preferred with engines having more than 150 or 160 HP.

 

[mondtster]

The early Beech Bonanzas (1947-1956) had an electric prop. The design only provided manual control of the prop pitch via a switch in the cockpit so it wasn't "constant speed" at all. In the early 50's an electronic control became available (I think it was originally an aftermarket product) using vacuum tubes and relays to operate the pitch change motor in response to RPM changes. Normally this was only used when large changes in airspeed were anticipated such as when taking off and landing or when leveling off from a climb. Leaving the controller in auto mode all the time tended to wear out the pitch change mechanisms which weren't designed for continuous adjustment. Later a "modern" transistorized version of the controller became available well after the Bonanza line had converted to hydraulic props for new production.

I'm pretty certain it was a factory option on the electric props. There are two different line items on the old equipment lists, one for a controllable pitch setup and one for the constant speed controller.

My plane was originally a constant speed setup, but it was converted to a Hartzell CS prop in the mid 1960s so the box and prop are long gone now.

For what it's worth, I also own another airplane that has the Hartzell diaphragm prop on it that is variable pitch. So I probably own two of the worst Hartzell props to own, lol.

 

[wrbix]

So, would say a Grumman Tiger benefit from a CS? I think most are configured for a cruise prop as their short field performance isn't mind blowing. But they typically cruise comfortably in the 130s with a useful load around 950 lbs.

Seems to me that the Tiger is sort of in the sweet spot.

My Tiger has the MT electrically controllable three blade....sure is sweet to be able to, in cruise, dial in a smooth quiet sweet spot of RPM and MP (22 and 22 is smooth and quiet in my plane) and watch the GPH go down with the RPM.
The issue of climb performance gain is still debated: I've never flown an AA5 with FP; Ron Levy reportedly did a side-by-side comparison FP vs VP and he felt it was a wash. Others claim a climb advantage.

 

[Pilawt]

Very few airplanes offer both a CS and FP prop as an option

Examples of airplanes built with fixed-pitch as standard equipment, but offering constant speed as a factory option, were the early years of the Piper Cherokee 235 and Cherokee Six (260 hp); Mooney M20D Master; and possibly the 200 hp Beech Musketeer Super. Cessna 175 only offered fixed-pitch through 1961, then switched to standard constant-speed in 1962; and among 180 hp fixed-gear Cardinals, only the '69 177A was fixed-pitch, and the 177B (1970-78) was constant-speed.