What is a snap roll??

[Runyond]

All,

Have been scratching my head trying to figure out what a snap roll is. From Basketcase's list of aerobatic sites I found this - "Snap or "flick" rolls have to be flown normally on a straight line. A snap roll is similar to a horizontal spin. It is an autorotation with one
wing stalled. In the regular snap, the plane has to be stalled by applying positive g forces. In an outside snap, the plane is stalled by
applying negative g. In both cases rudder is then used to start autorotation just like in a spin."

I cannot seem to wrap my mind around what this means. I originally thought this maneuver was around the roll axis (like an aileron roll). The description above makes it sound more like a horizontal maneuver (if that makes sense :confused: ).

Anyone able to help shed some light on this??

Regards,
Denny

[Mitch G]

The plane does roll (mostly) axially, but it's more corkscrew-shaped and has this snap-flick aspect to it.

Assuming you have a plane that can do one - not all can, you can do one by flying straight and level and then yanking back on elevator (i.e. full up) and yanking all the way right or left on the rudder.

I personally find snap rolls one of my favorite maneuvers.


Mitch

[Runyond]

Mitch,

So am I correct in understanding that it is more or less similar to an aileron roll, but much quicker? Does the tail stay behind the fron of the plane though the maneuver or is there some tumble to it as well? To perform one, do you input the elevator and rudder deflections at the same time, or do you wait to establish an up angle first and then deflect the rudder?

Denny

[Mitch G]

The tail cuts a bit of a circle or oval through the air during the maneuver, but stays behind the nose (i.e. no tumble). I'm just a beginner with the maneuver, but I think I pretty much input both rudder and elevator at the same time. Although, as I understand it, you can play with the elevator input during and at the end of the maneuver to extend or continue the roll.

If you have a plane that you think can snap-roll, and that you can regain control of easily enough if you should get dis-oriented, I say get it up about 3-5 mistakes high and try it. You'll see, it's a pretty straight forward maneuver. If it doesn't seem to work the first time, keep trying it. If it still doesn't happen, you may have a snap-adverse plane. To address this problem, you can try tinkering with a more rearward CG, but do that at your own risk.

Then, read my "Avalanche" thread in this forum to get some additional ideas (which I have not yet had a chance to try - stupid winter weather :().


Mitch

[Cadillac84]

Like Runyond, I was scratching my head trying to visualize a "snap roll." The thing that prompted me was a group of photos which I would love to share but don't have the facility to do it. A contract pilot ferrying a Hawker 800 XP from Mexico to the the U.S. performed three or four snap rolls, inflicting very serious (and probably terminal) damage to the airframe. If there is interest, I may try to post the photos in some way they can be seen, but you could probably use Google to find them.

I read about various aerobatic maneuvers and, like Runyond, was just not able to "see" it in my mind.

I happened upon a video clip of a demonstration with an RC plane.

I see that someone has posted "not how you do it in a real aircraft" so keep that in mind.

http://www.metacafe.com/watch/yt-RC5mz5o3VD4/snap_roll_http_www_wild_wings_co_uk/

After you watch that a few times, you can watch from the cockpit of a Cessna 152 which, last time I checked, was a real aircraft. Here's that link:

http://www.metacafe.com/watch/100316/cessna_152_snap_roll_and_spin_over/

I'm not a pilot, so I'll be satisfied with those two.

Chuck

[fhhuber506771]

A snap-roll is a purposeful accelerated stall resulting in a "spin". That spin may not have the plane rotating about a vertical line, but the motion of the plane about the line of travel is the same in a snap-roll as a spin.

The nose stays pretty well on the line of travel and the tail follows a helical path around the line.

It is a very high stress maneuver because you have to load the wing to the point where it stalls... and doing that at speed means HIGH G forces... Depending on how much above "stall speed" you perform the maneuver.

Wings designed to take 40+ Gs have been known to shatter in RC Pattern competition when doing snap-rolls.

[bjr_93tz]

Snap rolls have no place in pattern IMHO. They are not a precision maneuver, they are a sticks in the corner, pray to god roll of the dice whereby if it didn't finish up wings level then better LUCK on the next one. True, plane and TX setup can make them more repeatable but they are still a pig in the poke.

Nobody can perform a true snap roll (by definition) and maintain a straight flightpath either horizontal or vertical and so the maneuver only adds bumps to straight lines and curves which distracts from the gracefulness and precision of the sport.

Don't get me wrong, they do help sort the men from the boys when it comes to downgrades as they can be random and unpredictable on occasion, and they have forced aircraft designs to become both agile and stable however snaprolls in uplines and at bottoms of loops are there only to penalise those who can't afford to have a top dollar motor in their plane with the necessary grunt to pull them out of the stalled mess they are in.

Snaprolls are like filling a NASCAR oval with chicanes and still calling it racing....

[FrankW]

Snaprolls are like filling a NASCAR oval with chicanes and still calling it racing....

NASCAR is boring anyways, bring on F-1!

I love doing snaprolls. They're easy, fun and everyone seems to be amazed when I do them. I'm not sure why, but they are a crowd pleaser... even more so than rolling circles. I really enjoy a one and a half snap into inverted.

-Frank

[bjr_93tz]

I live is Aus, so I used NASCAR as an example, I'm a MotoGP fan myself.

If I have to do a snap roll, I enjoy a "triple snap", where the first bit is 1 1/2 positive snap to inverted, followed by 1 1/2 negative snap to upright in the same direction of rotation. Try adding the 1 1/2 negative to your positve 1 1/2.

The aileron input stays the same, but you switch to down elevator and opposite rudder at the 1 1/2 point when inverted. It takes a while for people to figure out why your plane didn't bury itself or loose any height despite doing 3 "seamless" snaps :D

[FrankW]

Sounds fun, I'll have to give it a shot.

[RocketRob]

Get some altitude, get some airspeed then all at once......Put your left stick in the upperleft corner and the right stick in the lower right corner - hold as long as you dare.....

good test to how strong your airframe is- fun too!

[PerlAddict]

Now, when you say put your left stick in the upper left corner ... is it really necessary to have the throttle at full power to perform a roll well?

I have a feeling I'd rip the wings right off my Taylorcraft trying to do this. I need to pick up a Pitts or Ultimate and starting having some fun with aerobatics.

[RocketRob]

No, but on a plane stressed for some violent maneuvers it makes them occur very quickly and violently. And can result in a nice spin......

[bjr_93tz]

Get some altitude, get some airspeed then all at once......Put your left stick in the upperleft corner and the right stick in the lower right corner - hold as long as you dare.....

good test to how strong your airframe is- fun too!

I fly mode 1 (but with the throttle backwards) so that would give me full down elevator, full left rudder (left stick), full right aileron and full throttle (right stick), ie full power negative snap. Gee, I'd only try that one at the bottom of a downline to make sure I had plenty of airspeed :D

I also cheat a fraction as I have a snap condition which becomes active when the elevator/rudder stick (again mode 1) is boxed giving me suitable throws.

[FrankW]

I fly mode 1 (but with the throttle backwards)

:confused: :confused: :confused:

I don't think I'll be trying that configuration anytime soon.

[fhhuber506771]

Depending on the aircraft... a snaproll at full throttle (high airspeed) might be a very bad idea.

As I mentioned earlier... planes with wings designed to handle 40+G maneuvers have shattered thier wings doing snaps at high speed.

The wing needs to stall before the G force exceeds structural limits. The faster you are flying when you "bury the sticks in the corners; the higher the G force before the wing stalls.

Get a Dynamic Soaring plane going close to 300 mph and try a snaproll and you may see it seem to explode because of the way it could come apart under the G forces. Dynamic Soraing planes have been calculated to approach (or possibly exceed) 100 G in achieving thier extreme speed, but a snap at that speed could MORE THAN DOUBLE the G force.

[FrankW]

Get a Dynamic Soaring plane going close to 300 mph and try a snaproll and you may see it seem to explode because of the way it could come apart under the G forces. Dynamic Soraing planes have been calculated to approach (or possibly exceed) 100 G in achieving thier extreme speed, but a snap at that speed could MORE THAN DOUBLE the G force.

Why would you snap roll a DS plane? My favorite so far are SpaceWalkers, they look great in a snap.

-Frank

[fhhuber506771]

Why would you snaproll any airplane?

Because you want to.

The question came up about the structural implications of doing a snaproll, so I picked the most extreme case I could think of as an example of when you really should NOT try it.
"Carbon Fiber rain" would be the expected result.

[bjr_93tz]

:confused: :confused: :confused:

I don't think I'll be trying that configuration anytime soon.


Pulling the throttle stick back towards me for full throttle is just what you get used to. Dad learned that way as he used to race motorbikes and he taught me that way as well. It's only became a pain in the butt when they started making TX's with the ATL function non-reversable, which necesitated swapping the pot wires on the throttle. Only had to do that on two TX's though. I also pull the throttle stick back for positive collective on the chopper as well.....

The only other thing you have to be careful with though is when you stand in front of a 40% YAK with a DA150 with the throttle stick all the way back and start flipping the prop to start it, any moron within visual range who doesn't know you will go crazy for that split second trying and stop you, thinking you're at full throttle :D

(YES I do use the starting gates on the bigger stuff, mostly ;) )

C'mon fhhuber506771, lighten up, I'm sure that most people realise a full throttle snap on a downline isn't a good idea for 99% of the aircraft out there, especially when you end the statement with a " :D ". A well set up DS'er shouldn't have enough control throw to do a snap roll anyway....

[RV3driver]

Snap rolls have no place in pattern IMHO. They are not a precision maneuver, they are a sticks in the corner, pray to god roll of the dice whereby if it didn't finish up wings level then better LUCK on the next one. True, plane and TX setup can make them more repeatable but they are still a pig in the poke.

Nobody can perform a true snap roll (by definition) and maintain a straight flightpath either horizontal or vertical and so the maneuver only adds bumps to straight lines and curves which distracts from the gracefulness and precision of the sport.

Don't get me wrong, they do help sort the men from the boys when it comes to downgrades as they can be random and unpredictable on occasion, and they have forced aircraft designs to become both agile and stable however snaprolls in uplines and at bottoms of loops are there only to penalise those who can't afford to have a top dollar motor in their plane with the necessary grunt to pull them out of the stalled mess they are in.

Snaprolls are like filling a NASCAR oval with chicanes and still calling it racing....

Snaps can be a precision maneuver if done properly. Snaps and fractions of snaps are included in IAC known sequences from the Intermediate to Unlimited categories.

It is rarely mentioned in RC flying, but the best snaps are done WITHOUT the airplane fully stalled...meaning not just burying the sticks in the corner. You want to use the elevator to increase the angle of attack just enough so that when full rudder is added an instant later, one wing will immediately stall. More elevator than necessary only kills energy, slows the rotation, and makes the stop "softer". Once the snap breaks, unloading the elevator accelerates the snap and greatly reduces energy loss. With proper timing, the stops can be very crisp and precise.

[bjr_93tz]

.....and TX setup can make them more repeatable.....

If you own a 14MZ (can't speak for JR) you should know exactly what I'm talking about ;)

Illegal (for competition) automatic timing functions and other "features" abound in this radio which most either don't know about and organisers have to turn a blind eye to because it's a commercial product by a large RC manufacturer.

If I was running the show, all tx's used in F3A and IMAC should have a "dumb" model setting which disables all mixing and timing and leaves you with servo reversing, subtrim and endpoints. I have a "Vanilla" condition on my F3A ships which disables all the trimming mixes and while it increases the workload the plane doesn't fall out of the sky, however it's much easier to fly straight with the mixes on.

I'm a bit anti-electronic aids when it comes to competiton work but that doesn't mean I won't use them if I can, which is probably weird because my work involves electronics. Anyway, enough ranting from me and back to my Firecracker...