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They reduced torque reaction. On the seafire it was impossible to put a bigger prop on the plane so a contra rotating prop was the next best thing. It weighed more, it was problematic at times under very high G load. To my knowledge they all had the two props going in opposite directions. To me one of the most interesting variants was the Fairey Gannet which had two engines driving the two parts of one contra prop. This gave the power for take off and landing while allowed a longer loiter time for its job in Anti Submarine ECM plane.I noticed both during and after WW2 there were several aircraft that had 2 props on the same shaft/engine. I can't help but think they would do more to harm than improve airflow. One Soviet example had the props rotating in opposite directions.
Did these odd prop configurations actually improve performance?
I think I read somewhere that even with a contra prop the tips are supersonic on the Tu 95 but the engines are 11,800 shp each.The solution to all of these was contra-rotating props, with essentially two three-bladed propellers turning in opposite directions.
yeah, they would have been pushing the envelope, even of contra-rotating props.I think I read somewhere that even with a contra prop the tips are supersonic on the Tu 95 but the engines are 11,800 shp each.
I worked with propfans when I was at HSD. To be sure, I'll have to dig up the CR I wrote, but, yes the rear prop blades are at a somewhat greater pitch, but not as much as you may expect because of swirl. It also depends on how the gearbox is set up, in that it can be set so both props get the same torque, like the wheels ona car with a normal differential, or the same rpm. In the former, blade pitch is controlled to match rpm, while in the latter pitch is controlled to match power.I knew about the torque negation but have always wondered about whether the rear prop got the same lift or was the air between the props disturbed enough to affect the rear one. Would they have run at the same pitch?
Some of the propfan designs had 11 blades in a hub, and production props have eight. The British built five-bladed props, and the Japanese, six. The main -- probably only -- reason to go to contraprops is when there is a diameter restriction. There's also a lot of related nonsense about two or three or one blades being most efficient: also not true.Propellers are kind of self-defeating for high-power engines. As you produce more power, you need a bigger prop to absorb that power (either more blades or longer blades), problem then is that a bigger prop produces more torque, longer blades mean the prop has to turn slower, as the tips exceed Mach 1, and there may not physically be enough room for the mechanisms to control the pitch of 6 blades in one hub.
The torque produced could easily roll the aircraft over at low airspeeds and high power, such as a go-around.
The solution to all of these was contra-rotating props, with essentially two three-bladed propellers turning in opposite directions.
Likely true. The US was also experimenting with contraprops, but the closest they came to service was probably the XB-42, which would have been a great fast bomber in 1943.My understanding of the US position was simply that the gains were not worth the mechanical and engineering problems. Essentially the same reason aircraft don't fly by flapping their wings