Do contra rotating propeller incidence angles of first and second prop with different spin diameters affect positive or negative thrust an speed of the a/c?
closed as unclear what you're asking by TomMcW, vasin1987, J. Hougaard, Gerry, Manu H Jan 14 at 9:37
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I would say that the propellers are there to create positive thrust, so if they created negative thrust, they would not be used. It seems logical to me.
Also, I believe you're asking about contra-rotating propellers. It's a minor difference in definition.
If a twin engine airplane (for example) has one engine that turns to the right, and the other engine turns to the left, they are counter-rotating.
If a single engine drives two propellers, and they turn opposite directions, they are contra-rotating.