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Stabizer Pressure
Howard Rush:
--- Quote from: Chuck_Smith on February 12, 2021, 05:55:10 AM ---The tail force required in a constant radius turn (neglecting gravity and the fact that our loop described on the surface of a sphere) is pretty easy to quantify: ...
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Here's a quantification: https://stunthanger.com/smf/engineering-board/some-forces/
I made a video recording of control deflections of Paul Walker doing a round loop. He does quite round loops. Control deflection is all over the place. I'd post the video, but it's a zillion MB, and I never learned how to make it smaller.
Chuck_Smith:
Cool Howard. As a point of reference, when I do a loop in a full scale aircraft, to make it nice and round I make a 3g pullup but at the top of the loop, I'm basically zero g. If I get it right the pullout ends at 3g and my original entry airspeed, so the elevator is always changing during the maneuver. A loop in a controline plane is a lot more complicated since it involves all six degrees of freedom.
Now for the final blow to the "steering fins" version of the elevator, let's address the horizontal tail's aspect ratio. We know the aspect ratio is key to its span-wise lift distribution along the surface since the AR determines the amount of upwash coming into the surface. The lower the aspect ratio of the tail, all other things being equal, the more it has to deflect the elevator to get create the same change in lift as one of equal area with a higher AR.
OK, now for a visualization that everyone can relate too regarding the shed vortex creating a warped flow field and all that jazz and how the 2D, non-viscous, infinite wing theory is almost completely useless on a real 3D airplane:
I give to you - the Flite Streak. That tiny little elevator attached to a much larger stabilizer doesn't inspire much confidence, but man, it sure as heck turns that little airplane - and quickly. (Notice too that modern combat ships have evolved to tiny elevators on extremely short tails, compared to the long booms and planks we used back in the day.)
Granted, there's a lot of flow visualization required to grok the whole deal of why that little strip of an elevator is so danged powerful, but hopefully it's enough empirical evidence to show that something a lot more complicated is going on than first meets the eye.
Chuck
Aside: it also demonstrates why a "wicker bill" on a racecar wing has such a dramatic effect even though it's chord is negligible compared to the wing it's attached to. I can attach a .300" protrusion onto the TE of an Indy car's car rear wing and the effect is strong enough it will require a change in spring rate to keep from bottoming out at top speed with the added downforce it created.
Howard Rush:
--- Quote from: Chuck_Smith on February 13, 2021, 05:55:23 AM --- (Notice too that modern combat ships have evolved to tiny elevators on extremely short tails, compared to the long booms and planks we used back in the day.)
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Just looking at them, you'd think they'd have no maneuvering stability. They don't.
Chuck_Smith:
--- Quote from: Howard Rush on February 13, 2021, 06:56:18 PM ---Just looking at them, you'd think they'd have no maneuvering stability. They don't.
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Howard, back in our day combat was a lot more savage. We flew like falcons taking prey on the wing. Today they look more like a swarm of gnats :)
Chuck
Ken Culbertson:
y1 y1
--- Quote from: Chuck_Smith on February 15, 2021, 05:13:53 AM ---
Howard, back in our day combat was a lot more savage. We flew like falcons taking prey on the wing. Today they look more like a swarm of gnats :)
Chuck
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y1 y1 It is even hard to tell if there are even any tactics in play other than turn and burn. I used to love combat.
Ken
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