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This is slightly related to my other question on variable-pitch controls.

I want to know if WW2-era aircraft typically had variable-pitch or constant-speed propellers. Variable-pitch lets the pilot adjust the propeller blade pitch. "Constant speed" is the same as variable-pitch, but the engine does it automatically to keep the best performance at various airspeeds. This also lets the engine keep a constant RPM so it can always run at its optimal RPM, also increasing efficiency.

Anyway, were such things seen in WW2? Were they the norm, or the exception? Did single-engine aircraft have them, or were they more common on multi-engines?

I'm interested in all the nations who made aircraft, especially USA, UK, USSR, Germany, and Japan. And I'm interested specifically in the combat aircraft, like fighters and bombers, not necessarily the civilian transports of the era. This will give us a good idea if the extra complexity and weight was acceptable for combat aircraft of the era.

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  • $\begingroup$ i believe there was a change happening at the time. At the beginning of the war, there were many aircraft with fixed pitch. Some had high/low pitch. During WW2 technical innovation was rapid, and rather soon most high-performance aircraft had constant speed propellers. But not all aircraft were high-performance so some staid at fixed-pitch. $\endgroup$
    – ghellquist
    Commented Dec 20, 2018 at 21:43

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Most WW2-era military aircraft had constant speed propellers.

People often confuse variable pitch, controllable pitch, and constant speed. In general practice they are all the same thing, as all constant speed propellers are just the most common form of a variable pitch propeller.

There were very few aircraft where the pilot only had a simple control to just vary the pitch of the propeller. A few aircraft also had propellers that were only adjustable on the ground.

Most aircraft made since early WW II either had a fixed pitch, or constant speed propeller. “Constant speed” means the pilot controls engine RPM through either a hydraulically, or electrically, operated control system. It really is a type of RPM governor.

Some notable exceptions were the early Hurricane and Spitfire fighter aircraft that initially had wooden, 2-bladed, fixed pitch propellers because they were lighter than metal constant speed propellers. There were performance penalties though so these were soon replaced with metal 3 bladed, 2 position "controllable" propellers, with coarse and fine pitch settings. By 1940, they were all updated to metal constant speed propellers.

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  • $\begingroup$ ..." In general practice they are all the same thing as all constant speed propellers", this is not true. The difference between variable pitch and constant speed is the variable pitch DOES NOT HAVE A GOVERNOR. The Continental "E" series engines found on Bananza, Navion, Grummen Goose, etc are all variable pitch (no governor). There was an adapter called a "T" drive that could be added that would convert the "E" series to constant speed. I owned several Navions and pilot workload with a variable pitch is considerably higher than a "set and forget constant speed". $\endgroup$
    – jwzumwalt
    Commented Jul 3, 2018 at 11:54
  • $\begingroup$ The focus of the question was WW II military aircraft. Even for general Aviation aircraft, those aircraft you mention are exceptions, and my statements "in general" and "most common" are still true. $\endgroup$
    – Mike Sowsun
    Commented Jul 3, 2018 at 13:54
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    $\begingroup$ The Navion and Grumman Goose ARE WWII Military aircraft (and there are others). There is no "general practice" where variable pitch is "the same" as a constant speed. $\endgroup$
    – jwzumwalt
    Commented Jul 3, 2018 at 22:12
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    $\begingroup$ @jwzumwalt, The Navion is not a WWII military aircraft in any sense of the term. According to navion.com/history.html it was "designed at the end of the WWII... for the civilian market." Having a few models also designated for military use later in that same decade doesn't gain it acceptance into the big boy club that won the war. (the OP emphasized they were interested specifically in fighters and bombers) $\endgroup$
    – Michael Hall
    Commented Jul 8, 2022 at 1:16
  • $\begingroup$ @ Michael Hall - I owned two military Navions it depends on the model (The original A model were mostly military). North American, built 164 improved L-17B Navions for the U.S. Air Force. General McCarthy was assigned one and flew it during the Philippine campaign. See this article by the National Military Museum. nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/… $\endgroup$
    – jwzumwalt
    Commented Jul 20, 2022 at 22:12
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Variable pitch (with feathering) was virtually universal on (at least American) multi-engine fighters, bombers, and transport aircraft even early in the war: the DC-2 had feathering variable pitch, and it entered service in 1934. The P-38 had feathering and variable pitch, and was in service before the US entered the war.

Constant speed propellers were also found on many single engine combat aircraft -- one was the Hellcat, which entered service in 1943, though it's very possible the technology was introduced earlier. The P-47 Thunderbolt also had this feature.

When you're talking about aircraft that weigh several tons and need to deliver thousands of horsepower through a propeller, especially for combat operations, the weight and cost of variable or constant-speed propellers became negligible by comparison to the cost of the aircraft or the cost of fielding a losing design.

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    $\begingroup$ You haven’t really answered the question clearly and seem to be adding to the confusion . Both the P-38 and DC-2 had constant speed propellers, as did most high performance aircraft of the time. $\endgroup$
    – Mike Sowsun
    Commented Jul 3, 2018 at 2:53
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A constant speed propellor is a variable pitch propellor, the idea is that the pitch is adjusted automatically so that engine rpm remains constant with varying altitude and power settings.

The answer is yes, they were used in World War Two, although some light aircraft and older types used in the early war years had fixed pitch propellors.

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    $\begingroup$ This defines what a constant speed prop is, but it doesn't seem to answer the question about whether they were used in WW2 or not $\endgroup$
    – Pondlife
    Commented Aug 26, 2018 at 18:30
  • $\begingroup$ The answer is yes, they were used in World War Two, although some light aircraft and older types used in the early war years had fixed pitch propellors. $\endgroup$
    – J. Southworth
    Commented Aug 26, 2018 at 23:11
  • $\begingroup$ A variable pitch propeller does NOT have a governor while a constant speed does. The two are not the same. $\endgroup$
    – jwzumwalt
    Commented Aug 27, 2018 at 11:52
  • $\begingroup$ A constant speed propellor has variable pitch and a governor, whereas a variable pitch propellor does not necessarily have a governor. $\endgroup$
    – J. Southworth
    Commented Aug 28, 2018 at 10:22
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Constant speed propellers were introduced in WWII. If you have a somewhat late war perspective (USA), then they were ubiquitous.

However, there is a great story about coming in and retrofitting Spitfires as quickly as possible during the war to upgrade them to constant speed props.

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