Laminar Flow Airfoil

At my gliding club there is an older glider with a large toggle switch on the panel. That switch is labeled "BUGS". Always amuses me...

The "BUGS" switch is an input to whatever that glider uses for a flight computer. A single bug splat disrupts the laminar flow and significantly reduces the performance of the wing in that spot. Enough splats and you have to let the flight computer know that the performance of the glider has significantly decreased. In practice that affects things like the final glide calculation. Without the adjustment you might think you have gained enough altitude to get back to the gliderport without having to climb again, but you could end up a bit short.

For a while I flew an aero commander 100 “darter” (not the 112 low wing type) that looked like a Cessna 172 with a Mooney tail. It had a couple of cool innovations, fiberglass leaf springs for the landing gear, and a laminar flow airfoil. The gear was great, flexible without feeling springy, and the airfoil gave me about a 0.5-1gph cruise efficiency improvement over the 172 with the same engine/prop at the same speed. (Depending on how clean/waxed the wing was, rain, etc)

The wing was not good for bush flying though, it was either flying or not flying, not much middle ground. Popping off in ground effect to accelerate was much less effective than in a 172.

The stall break was a slight burble, then a clean break with no extra warning. The airplane was well mannered, though, hard to get it to drop a wing, and very controllable in a falling leaf stall.

I recall hearing many years ago about undesirable flight characteristics of the Rutan Vari-Eze when the laminar flow canard got too contaminated with bugs and became very nose-heavy.

A solution adopted by many owners was to put micro vortex generators on the upper surface, which wasn't great for the laminar flow, but maintained predictable flying characteristics irrespective of contamination.

That had potential risks, though, because the airplane was designed to have the canard stall before the main wing, which would lower the nose and prevent the main wing from ever stalling - eliminating the possibility of the stall/spin accident. Adding the vortex generators could change the aerodynamics enough to the point where the main wing could be stalled before the canard. At that point, since you have no downward-lift-generating tail surface, breaking the stall can be difficult and you could end up in an unrecoverable stable "deep stall".

Now there are cases where you can see vortex generators on both the upper and lower surfaces of some control surfaces, as on the Quest Kodiak, to provide better low-speed authority in the wing stall regime.

What really surprised me when I heard about it was that even after all those decades of research and development, there was still room to develop novel laminar flow wings and fuselage to be used in a business jet[1] in the early 2000s.

[1] https://global.honda/en/products/HondaJet/innovation/innovat...

https://www.hondajet.com/-/media/HondaJet/Documents/Technica...