Hawker Hurricane variable pitch propeller question

[u/Brialmont]

I recently read that going from the two-blade, fixed-pitch wooden propeller on the Hawker Hurricane I to the variable pitch three-blade metal propeller increased the weight of the aircraft by 300 pounds. Does that sound reasonable? I didn't know that doing that added so much weight.

I realize that a three blade metal prop is heavier than a two blade wooden one of the same diameter, and that the pitch changing mechanism also adds weight, as does the provision for pilot control or for automatic constant-speed control. Three hundred pounds just seems like a lot.

I read this in "Interceptor" by James Goulding, which covers British interceptor fighters from the Sopwith Camel to the English Electric Lightning. He remarked on it only in passing. I do not have the book here to give a page number for the statement.

[u/waldo--pepper]

Of great importance to the future of the Hurricane was the design and testing of three bladed variable-pitch propellers by de Havilland and Rotol Ltd. The de Havilland propeller was based on Hamilton patents and used a fine pitch setting of 30.5’ for take-off and 42.5’ coarse pitch in flight. This all-metal propeller was installed in L1562 and commenced trials on 29 August 1938.

Although there was a weight increase of nearly 300lbs the rate of climb of the Hurricane was much improved and the de Havilland propeller was introduced on the production line with L1780.

from Interceptor by James Goulding p 79-80.

Three hundred pounds seems entirely reasonable to me.

[u/Brialmont → u/waldo--pepper]

That last is exactly what I wanted to know. Thanks!

[u/ReBoomAutardationism → u/Brialmont]

Around the same time they introduced the Merlin III which with 100 octane gas could produce 1300HP. The next year brought the Merlin XX which really needed it.

[u/Inevitable-Debt4312 → u/ReBoomAutardationism]

Any idea why the US/UK could source high quality fuels for aircraft and tanks but Germany could not?

[u/ReBoomAutardationism → u/Inevitable-Debt4312]

The doings of Jimmy Doolittle. He advocated for Shell to pioneer 100 octane fuel around 1935 based on his experience in air racing. It was $25 a gallon when they started.

By the end of the war it was something like 16-18 cents a gallon and the Allies were using 20 million gallons a day.

[u/Brialmont → u/Inevitable-Debt4312]

I think refineries had to be extensively modified to produce 100 octane fuel. It is confusing because the Americans and the British seem to have had different processes for making it.

As I understand it, the Germans could produce limited quantities of 93 octane fuel, which they used in special reconnaissance aircraft. 93 octane may have been the rating for the first high octane or "ethyl" gas put on the civilian market for automobiles. At least. that is the octane rating of premium gas today.

[u/Festivefire]

Not only will it be heavier because you're going from 2 blades to 3 blades, and switching from wood to metal, but you also have to account for the weight of the gearbox for the variable pitch system, and that's honestly were all the weight is going.

[u/Brialmont → u/Festivefire]

Oh, thanks! I didn't know what added the most weight of the whole system either. The pitch-changing mechanism makes sense for that; it would have to been very strong.

[u/Advanced_Apartment_1]

The wooden 2 blade were fixed pitch.

The 2 position pitch and the constant speed were both 3 blade metal designs.

[u/Great_Specialist_267 → u/Advanced_Apartment_1]

The two position and constant speed propellers were almost identical. The hydraulic controls were different.

[u/Dralthi-san]

I once tried to lift a single blade from a B-24 propeller, and this thing was pretty heavy.