Leading edge main spar, Rans S-21. thoughts?

Brad W

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what do you think of this design, where the wing's leading edge IS the main wing spar? (it's an extruded aluminum D-shaped beam)

I keep thinking about the structure being compromised after it takes a hit. No doubt it's strong, and it would prob take quite a bird to dent it...but once it's dented, seems like that wing is done....not likely repairable.

I'm thinking about hangar rash, hitting a sign post, big bird strike....or even lightning.

(the lightning thing...many years ago I attended a lecture by Bruce Fisher. He was involved in a NASA lightning strike study back in the 1980's. One of the photos he showed was the leading edge of a GA plane...cessna I think it was. Lightning had hit a wingtip, and traveled down the wing, departing the other wingtip...if I remember correctly, it was in the nav light wiring that was just inside the leading edge...anyway, the entire leading edge was imploded...invertered. What was a D shaped outie was now a D shaped innie. A result of the magnetic field produced by the high current he said.)
 
It is fairly thick and D shaped, so it won’t be hurt by small birds and the like. The airplane’s speed is fairly low too, which helps.

Lightning? I wouldn’t be taking an S-21 near that kind of weather anyway.

Bottom line for me is that damage to the LE wouldn’t be an A or B list concern for me.
 
what do you think of this design, where the wing's leading edge IS the main wing spar? (it's an extruded aluminum D-shaped beam)
FYI: they've used this type construction for helicopter main rotor blades for decades. Its basically bullet-proof.

1708569178196.png
 
If you can blow out a main spar located at the leading edge, you can blow out a main spar located at 25% MAC.
There are a more than a few aircraft that count on the leading edge skin to provide torsional rigidity as part of a skin / spar D cell or use a tubular spar at the leading edge.
 
well, yeah I wrote some of those as a far-out theoretical thing....
I suppose my real thought revolves around a more probably hangar rash even. Pull a wing into a post or something. Dent that thing and the wing is done....
but if the spar is deeper into the wing, then sheet metal is damaged and that is repairable

FYI: they've used this type construction for helicopter main rotor blades for decades. Its basically bullet-proof.

View attachment 125729
thanks for posting that. Interesting. Ive read a lot of biographies of helo pilots in viet-nam. Lots of stories there about blades taking tree hits, taking rounds, etc...
 
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