The Florida Air Museum in Lakeland has a Wittman W-8 Tailwind with four wooden, propeller-like blades on the engine cowling:

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Source: own work

What are the blades for? It's an experimental aircraft so it's possible that they're unique to this specific airframe.

  • $\begingroup$ That Tailwind has several unique features, including retractable landing gear, adjustable air inlets, and a cowl flap. It was built by a guy named Anthony Occhipinti about 1966. I've seen pictures of it in the past but not with the vanes. It definitely is a one-off. $\endgroup$ – John K Oct 31 at 3:19
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    $\begingroup$ I wonder if the vanes might be intended to serve as "flow straighteners" to reduce the spiral of the propwash-- possibly to increase efficiency and/or to eliminate thrust-related asymmetry in handling (i.e. need for right rudder at high power and low airspeed.) You don't happen to have a picture from the other side to show whether the curved side is on the top or the bottom on those blades do you? On the other hand, a close look suggests the blades are moveable, which may tend to go against this interpretation. $\endgroup$ – quiet flyer Oct 31 at 4:27
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    $\begingroup$ @quietflyer I won't post it as an answer because I don't know for sure, but I am fairly certain that the owner was experimenting with ways to mitigate P factor and torque effects to gain a few knots. I've been in EAA since the mid 70s and this sort of home brew experimentation was very common back when most homebuilts were made from scratch and individual builders would heavily customize their aircraft and try different things. $\endgroup$ – John K Oct 31 at 12:15
  • $\begingroup$ I suppose they are probably only ground-adjustable not movable in flight. Sure would be interesting to see a photo from other side to see whether the 2 blades on the right were mounted with the more curved surface of the airfoil facing up or facing down; if were to straighten out the spiral slipstream one would tend to expect the latter. $\endgroup$ – quiet flyer Oct 31 at 13:14
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    $\begingroup$ It sure looks like right horizontal one is upside-down compared to the left horizontal one, consistent w/ straightening the slipstream. Someone ought to write an actual answer out of all this-- $\endgroup$ – quiet flyer Nov 1 at 3:31

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