Like Matt said, it looks like he's trying to snap the plane by looking at the rudder and elevator deflection. One thing that would make it a little more crisp and snappy would be less or even opposite aileron.

Nice video of a fun flight. But there looks like a lot of corkscrew aileron rolls. Just a personal thing.
 
Low Pass said:
One thing that would make it a little more crisp and snappy would be less or even opposite aileron.
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No...it's in-snap aileron that helps speed up the rotation a bit. For planes like RV's and Pitts' with partial-span ailerons, half deflection or so works well. Full deflection adds too much drag. Monoplanes with full-span ailerons work well using about 1/4 deflection.

Mostly what makes a snap really go is unloading the elevator to around neutral immediately after it breaks. Watch the snap starting at 2:08 in the video - the elevator is held most of the way around. In competition, this would be called a "buried" snap. Cool video and nice air-to-air work.
 
sandifer said:
No...it's in-snap aileron that helps speed up the rotation a bit. For planes like RV's and Pitts' with partial-span ailerons, half deflection or so works well. Full deflection adds too much drag. Monoplanes with full-span ailerons work well using about 1/4 deflection.
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My defintion of a snap is a roll done with one wing stalled. What I saw was a tight spiraling roll.

I know without a doubt the spins tighten from a spiral to a spin with opposite aileron in the -8. As for the snap roll, I'll make a point to actually follow through on the inputs next time I'm out.
 
Low Pass said:
I know without a doubt the spins tighten from a spiral to a spin with opposite aileron in the -8.
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Very true about spins, but spins and snaps are different animals. The reality is good snaps are typically flown with a bit of in-snap aileron.

Check out this video from Ty Frisby, an acro instructor with Sunrise Aviation who has competed in the Unlimited category. You'll see a bit of in-snap aileron.

www.youtube.com/watch?v=Gu3BfXKstJ4&feature=related

Also check out Alan Cassidy's book 'Better Aerobatics' - which is THE best acro book available, with incredibly detailed descriptions of the maneuvers.
 
sandifer said:
Very true about spins, but spins and snaps are different animals. The reality is good snaps are typically flown with a bit of in-snap aileron.

Check out this video from Ty Frisby, an acro instructor with Sunrise Aviation who has competed in the Unlimited category. You'll see a bit of in-snap aileron.

www.youtube.com/watch?v=Gu3BfXKstJ4&feature=related

Also check out Alan Cassidy's book 'Better Aerobatics' - which is THE best acro book available, with incredibly detailed descriptions of the maneuvers.
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And check out the French Connection's Daniel H?ligoin's Snap Roll. No aileron input. Rudder and elevator alone. Forcing the horizontal spin.

http://www.youtube.com/watch?v=6ETc1mNNQg8
 
Low Pass said:
No aileron input. Rudder and elevator alone.
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Holy cow...that's exactly how I snap my Pitts! :D S-1's snap so fast, aileron doesn't have a lot of effect, so I don't bother. Never said a snap REQUIRED aileron, just that in most planes it helps a bit. But you had said OPPOSITE snap aileron helps speed the rotation, which it does not. If it does, you are clued into something world aerobatic champions are not.

Low Pass said:
Forcing the horizontal spin.
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"Horizontal spin" simply gives something for folks to relate to. Many disagree that this is an accurate description, since with a spin, BOTH wings are stalled (and stay stalled) and THEN autorotation is started by inducing yaw. Rotation occurs (much more slowly than a snap) because of the difference in DEPTH of stall between the wings.

In a proper snap roll, neither wing is stalled before the yaw is induced, but the resulting yaw quickly stalls one wing only. Because one wing is still flying, this is why in-snap aileron helps a bit...and again why it's not a true spin. However, too much aileron could unstall the down-going wing and slow the snap into a spiral. The objective of the snap is to get through it as fast as possible, with as little energy loss as possible.

Sorry, I just love talking acro. :D
 
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Great video!

Really really cool video!

Superb flying! That guy really knows his stuff! And professional made video too! Nice with timed split-screen and everything! One of the best RV-acro videos I've seen!
Anyone knows who this guy is? An ex-fighter jock maybe? Or a display pilot?

Thanks alot for sharing!
 
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ao.frog said:
Anyone knows who this guy is? An ex-fighter jock maybe? Or a display pilot?
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No, no...just some dude out fartin' around. It's a neat video, but there really isn't any heroic flying going on here...nothing anyone with a modicum of aerobatic experience couldn't do just as well.
 
snap rolls

I am pretty sure Van discouraged snap rolls in the RVs. Is that true for all models or just the -4?

notice about 3:08 a flight of three B1-RD's shoot through the frame.

Nice looking airplane and video.

CM
 
Here's a followup.

Took my -8 out for a "spin" this morning. ;) Did several snap rolls at ~65 kts. In-turn and opposite aileron had no observable effect on the snap rotation speed. But it does for sure tighten the spin.

Using aileron may be the practice with more advance acro. It just doesn't seem to do much with the RV(-8).

...."Horizontal spin" simply gives something for folks to relate to.
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IAC uses this to describe snap rolls.
....Many disagree that this is an accurate description, since with a spin, BOTH wings are stalled (and stay stalled) and THEN autorotation is started by inducing yaw.
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BOTH wings stalled in spin?? Now that would be new to me. The assumption I've been working under for a long time is that only one wing stalls in the *typical* spin and snap.

Other question brought up on snaps. Personally, I never enter them at more than 70 kts. Nor do I do them with anyone onboard.

And it is a very nicely done video!
 
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I must need another diversion today...

Low Pass said:
BOTH wings stalled in spin?? Now that would be new to me. The assumption I've been working under for a long time is that only one wing stalls in the *typical* spin and snap.
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So said the other philosophers when Aristotle observed the Earth was not flat. :D

You are of the opinion that the dynamics of a spin are no different than those of a snap roll. I strongly disagree, but I guess nobody can prove nuthin'. :)

In order to spin, the aircraft must stall first (this involves both wings). If one wing has normal airflow over the aileron, don't you think opposite spin aileron would slow the roll component of the spin rather than increase it? Just because both wings have exceeded critical AOA does not mean there cannot be a lift/drag differential between them causing autorotation. Stalled wings still create lift.

In a proper snap roll, you do NOT exceed critical AOA (but come relatively close) before initiating yaw. This is why one wing remains flying, and why aileron effects are different during a snap vs. spin. I think this is the critical distinction between the snap and spin. Otherwise, I can't see a reason for ANYONE to question the assertion that a snap is nothing but a horizontal spin. However, spins and snaps DO share the fact that autorotation is caused by an imbalance in lift between the two wings. But the dynamics of this imbalance are completely different. My two cents.

Alan Cassidy's very well respected book has an excellent treatment of spins. He even plots the lift/drag curve between the two wings (both shown above critical AOA). I would be interested in an aerodynamic explanation refuting this.

Really, this book is worth every penny and then some - even if you want to ignore the sections on spins and snaps. :)

www.shopeaa.com/betteraerobatics.aspx

More on Alan Cassidy:

www.worldaerobatics.com/Freestyle/Alan.htm
 
Brazilian team,

http://www.tuaregaerobatics.com/p/team.html

You may have to dig around to get stuff in English, most of it is in Portuguese. Google does a translate.

Ref reading material, while Alan's book is good, he was inspired by this book by Annette Carson and Eric Muller.

http://www.transair.co.uk/product4.asp?SID=2&Product_ID=6134

This pre dates Alan's book and is a superb treatise on the explanation of aerobatics.

Difficult to find now, but still around.

And I think the aeroplane and video were very nicely produced. Shame he didn't have a Go-Pro inside, the quality would have been lots better.
 
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