Does propeller slipstream cause enough instability to need twin rudders?

[kevjcarvalho]

Is the effect that the propeller slipstream (i.e the helix) hits the tailplane causing much instability quite significant such that if u are using a tractor propeller a single rudder won't work creating the need for two rudders away from the slipstream path??

 

[Cyrus]

There is no easy answer to that question, as it depends on the design of the aircraft. The effect of the slipstream is to induce a sidewash factor that modifies the vertical fins angle of attack.

 

[kevjcarvalho]

Is there any way to actually find the path of the helix?...like using CFD.

 

[Cyrus]

Sure, you can run CFD and then look at a plot of the streamlines. But that is going to be a huge under taking, and require a ton of processing power.