IAC Known Sequences for 2019

[1flyingyogi]

Originally Posted by ronschreck

Well, look at you! One contest in Primary and you are already practicing Intermediate figures. I'm going to keep my eye on you!

Your -4 is a different beast than my -8 so what works for me may be different in subtle ways. Generally speaking, a snap roll works when one wing is stalled just when the yaw motion is introduced. The sweet spot for my -8 is 100-110 knots upon entry. I suspect it might be lower for the -4 and maybe Bill McLean can chime in here. Snaps work best at a high power setting with plenty of prop wash over the tail so it would be best to slow slightly below your ideal entry speed, add full power and initiate the snap as you get to entry speed. Apply rapid aft elevator to pitch up about 10 to 15 degrees. You should feel about 3.5 Gs in this pitch up. (Full aft stick is NOT required.) Add rudder just as you add back stick. Full rudder position should be reached at the same time the Gs peak at 3.5. This is the point where one wing stalls and the other at high alpha induces a rapid roll into the stalled wing. As soon as this happens you should release the back stick pressure as you don't want both wings to stall. It's OK to add just a bit of aileron into the snap as well. To recover, lead the stop point and apply full opposite rudder as you jab the control stick slightly forward of neutral. The point where you lead the stop point will vary with aircraft so that will come with practice.
More than any other maneuver, the snap procedure is very dependent upon aircraft type, trim, speed and pilot inputs. You may do a hundred before you find the right combination. You will know when you find it. There is no doubt when the inside wing stalls and rapid rotation occurs. You will feel it and hear it and the RV grin is evidence that it really happened!

It doesn't mean much that I'm practicing snaps - just having some fun! And I have a lot of experience - a whole TWO contests under my belt, not just one! (sarcasm)

I'll give your suggestions on the snaps a try. Perhaps what I was doing wrong was waiting for the stall to happen BEFORE applying rudder. From what you're saying, it sounds like I should apply rudder right as I reach about 3.5G's on the pull. Let me try again next time I'm out. Thanks!

[RV8Squaz]

Hi Brian,

A fellow competitor gave me a good tip that seems to work. He told me to lead with the rudder a bit before pulling the bulk of the g. It seems to give the airplane some direction before stalling the wing. And I agree... you don?t have to go to the stop with the stick, but it does have to be an aggressive pull. Good luck!

[ronschreck]

Brian,

Another way to "cheat" is to hold a little right rudder (yawing to the right) just before entering a left snap. The air flow pushes the vertical stabilizer to the right as you reverse the rudder and the additional swing of the tail gives it a bit more momentum.

[sandifer]

Originally Posted by 1flyingyogi

Perhaps what I was doing wrong was waiting for the stall to happen BEFORE applying rudder. From what you're saying, it sounds like I should apply rudder right as I reach about 3.5G's on the pull. Let me try again next time I'm out. Thanks!

IMO those who often call snaps "horizontal spins" do a huge disservice to the understanding of proper snap technique. As you've discovered, pulling to the stall or buffet before applying rudder doesn't work. In fact, for good snaps in most airplanes you don't pull to the stall or buffet at all. You pull just enough so that the rudder application will THEN stall a wing. Excess elevator degrades the snap quality and kills more energy. The timing of the stick pull and rudder application has a huge effect on the "snappiness" of the snap. I'm talking small fraction of a second differences. Most folks tend to pull too much and delay the rudder application too much. They also do not unload soon enough and far enough at the proper time as the snap breaks to really accelerate the rotation to its full potential. Again, small fractional second differences between all the inputs has a huge effect. Since your hand generally moves faster than your foot, for all practical purposes, think of the two inputs being made simultaneously. Most likely even so, you will be leading slightly with the elevator, which is proper. Just be careful to avoid showing any yaw before the pitch change. IAC rules on snaps will nail you for that. Observing simultaneous pitch/yaw change is OK.

[1flyingyogi]

Originally Posted by sandifer

IMO those who often call snaps "horizontal spins" do a huge disservice to the understanding of proper snap technique. As you've discovered, pulling to the stall or buffet before applying rudder doesn't work. In fact, for good snaps in most airplanes you don't pull to the stall or buffet at all. You pull just enough so that the rudder application will THEN stall a wing. Excess elevator degrades the snap quality and kills more energy. The timing of the stick pull and rudder application has a huge effect on the "snappiness" of the snap. I'm talking small fraction of a second differences. Most folks tend to pull too much and delay the rudder application too much. They also do not unload soon enough and far enough at the proper time as the snap breaks to really accelerate the rotation to its full potential. Again, small fractional second differences between all the inputs has a huge effect. Since your hand generally moves faster than your foot, for all practical purposes, think of the two inputs being made simultaneously. Most likely even so, you will be leading slightly with the elevator, which is proper. Just be careful to avoid showing any yaw before the pitch change. IAC rules on snaps will nail you for that. Observing simultaneous pitch/yaw change is OK.

That was very helpful! Thanks Eric. I have a better understanding of what I was doing wrong now. Now lets see if I can put all this good information to use tomorrow. =)