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cujo

Baron 55 2 Blade prop

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Baron 55 - When 2 blade prop selected the animation shows contrarotating props i.e. not rotating in the same direction.

Can this be corrected?

regards

Mike

Edited by cujo
missed out aircaft type

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Are you sure you are not seeing visual harmonics, for lack of another term, that can occur between the time of engine start and arrival at full idle RPM?  Check the start of the second engine in this video, at about a minute and a half into the video.

https://www.youtube.com/watch?v=w-5ln_m5BVE

This is a three-blade prop Beech E55.  If you search for a B55 you will likely find a two blade prop starting up and in that can be seen the same illusion when the first (left) engine is started.

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Thanks for the reply Frank

If you switch between 3 blade and 2 blade in flight cruise you can clearly see the port prop effect changes direction.

Mike 

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As the person who scripted the animations for the B55/E55, I can absolutely guarantee that what you are seeing is an optical illusion.

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MIke. Clearly the props move in the correct direction when starting up the engines.  Both should turn clockwise (from left to top to right) when looking at them from the pilot's seat.  What you are observing is a visual harmonic, or stroboscopic effect of the light passing through the spinning blades at certain speeds.  Obviously this effect will be different between a two bladed prop and a three bladed prop as the passage of light is affected by the number of blades and speed.  Here are a couple of links to describe what you are seeing....  While sitting still with both engines at idle, increase the RPM on the port engine to 2500. Then switch to an outside view and look directly at the nose of the aircraft from a point in front of it.  Then note the blade rotation...

https://io9.gizmodo.com/why-do-wheels-sometimes-appear-to-spin-backwards-1593807400

https://www.scientificamerican.com/article/why-is-it-that-when-you-l/

Edited by fppilot

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I understand what you are saying but should not this effect be the same for both props at the same time? It is with the 3 blade prop.

If you adjust the revs and pitch until the effect is just rotating you can clearly see the starboard prop effect moving anticlockwise and the port prop moving clockwise with the two blade prop. With the 3 blade prop both prop effects move anticlockwise.

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The blades are not synchronized (there's no control for that) so the blades on the two engines are not spinning at the exact same speed.

I repeat, I animated this model's props, so I am absolutely certain they are rotating the same direction.

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I do not dispute the fact that the props are rotating in the same direction, that is obvious on start up. I am just observing the prop moving animation effect. I am not making a criticism just an observation that if you switch between the 3 and 2 blade props you will observe one prop animation reverse.

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Yes, one is still only observing an optical illusion... :smile:

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OK Mike.  Here you go!  Check out this very good real world 310R video.  Watch the whole half hour if you wish. I did and enjoyed it.

Here is why I am pointing this one out to you. Use the progress bar at the bottom of the video to advance to a bit over the 8 minute mark into the video and observe the visual effects of the blade rotation.  Then advance to the 11 minute mark into the video and observe the visual effects of the blades again.  Note at that point the visual effects appear to have the blades rotating in opposite directions.

https://www.youtube.com/watch?time_continue=8&v=wLYSCjCoYP8

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