need explanation on Blade Fans

[Apache-Pilot]

EDF which is the reverse blade fan? left side or the right side?

[WintrSol]

The purpose of reverse rotation in an EDF is so that it cancels the torque, or gyro, effect of the other EDF in a twin fan setup; as such, it doesn't matter which side the reversed fan goes.

[fhhuber]

typical is to have the fans rotate top toward center of the plane, just as with conventional planes that have one normal and one revered rotation.

The basis of this is that if one goes out, the torque of the working motor would tend to help counter the asymmetric thrust effect.

Full scale P-38 had an odd instability in a certain speed range that required the props to turn top blade away from center. I haven't heard of any other case of the top away from center being correct.

[Kloverzero]

Ditto and Ditto, You want the torque of the rotating fans in a twin set up, to pull toward the center of the plane.

[fredmdbud]

The convention is:

Normal rotation: fan rotates clockwise facing forward
Reverse rotation: fan rotates counter-clockwise

If the intention is to use the counter-torque to compensate for wing-drop from yaw tendency, I figure the normal rotation fan would be on the left.

[WintrSol]

Interesting; if the port fan turns clockwise when facing forward, and the starboard fan quits, as the aircraft starts to yaw the gyroscopic force would tend to lift the tail. The running fan would create some torque to lift the starboard wing; not sure if, without a throttle increase, that there would be much moment on that wing though. Also, on a small model, I can't imagine these forces would be very great to begin with.

[gooniac33]

Interesting; if the port fan turns clockwise when facing forward, and the starboard fan quits, as the aircraft starts to yaw the gyroscopic force would tend to lift the tail. The running fan would create some torque to lift the starboard wing; not sure if, without a throttle increase, that there would be much moment on that wing though. Also, on a small model, I can't imagine these forces would be very great to begin with.

you would be amazed to see! I did a whole video series on the small 50mm models because people didn't believe me when I said that torque is a factor until you reach flying speed. It does affect our models and especially the small ones. Here take a look...

https://www.youtube.com/playlist?list=PLsFORvKk7TcGDr-n3p1EXhNT4SCexkE3I

I have had my 80mm jet do some really weird things when the wing stops flying and I punch the throttle... all in the direction of the torque as well... So don't let the small diameter fool you. There is still enough inertia to make things happen.

[WintrSol]

Rapid changes in throttle causing rotation due to torque, without aerodynamic forces to resist it, I would expect; subtle effects on wing position at flying speed due to loss of one of two fans don't seem like they would be that noticeable, to me. My A-10 has both fans rotating in the same direction, and waggling the tail with the rudder doesn't seem to cause the tail to rise and fall from gyro forces. I suppose it might, but it would take a really calm day to see.