[NSRCA-discussion] Snap

Mon Oct 12 05:55:25 AKDT 2009

I kept a copy of the following e-mail.  Probably is some years old (~2005).  I believe will help in this discussion.  I hope that Dave Lockhart does not mind since this was already in this opinion group.  I think this could clarify some of the issues we have been discussing.  It is clear to me that snap roll is very difficult to do properly and that is the reason of the high K-factor.  Here is Dave's e-mail: "I think Bjorn made an extremely good point and analogy comparing the 3 pt shot to a snap.   I think snaps are precision manuevers .   I don't think luck with snaps is any different that luck with spin entry/exits or stall turn entry/exits.   All are difficult to consistently perform without downgrade (especially the snaps), and that is generally reflected in the KFactor (oops, another can of worms). 

  The reason stall turns are often performed conservatively is simple - a zero for a flopped stall turn is death - the scoring is usually so close at the top, that a single zero will take a pilot out of the running for the 1,000. I would say at the top levels, most pilots are 90+ % to complete a tight radius stall turn (the one that appears to rotate on the CG, and is not subject to a downgrade).   The same pilots are 99.9% to complete the slightly open radius stall turn that will get the minor downgrade.   If we as a pattern community want to see less conservative stall turns, all we need to do is increase the point deduction for the slightly open radius stall turn - the risk has to equal the reward, so to speak. 

  To specifically answer the 2 questions you posed (my opinions of course) - 1)   If it is indeed a true snap (and not a twinkle roll or barrel roll), then it does add to the capabilities of the pilot. 2)   Until we can achieve a level of consistency in judging snaps, they detract from the event. 

  Now, the long part, including some of the "secrets". 

  Airplane design - In general, in the early/mid 1990s, most designs migrated towards increased pitch stability and damping (which is often but not always synonomous with long tail moment).   This was great for groove/lock in corners and lines, but not good snaps - and perhaps not a bad bias considering the relatively low number of snaps in the pattern.   The increased pitch stability made it more difficult to setup a plane to do good snaps (and spins).   The same designs also generally migrated towards increased yaw stability (actually good for snaps, bad for spins, others will not agree).   My personal setups used as much as 35 degrees of elevator to achieve consistent stall entries to snaps and spins (and all of the elevator remained during the spin, but not during the snap) and 40 degrees of rudder in spins ( ele / rud only spins).   In recent years, the number of snaps in patterns have increased, and the newer designs have shifted towards less pitch stability (and less yaw stability, but that change is a response to the combined rolling/looping and rolling circle maneuvers). 

  Airplane setup - This is critical with any design, and when a snap is attempted, a couple things can happen - - a good snap. - a twinkle roll (not a snap). - a barrel roll (not a snap). 

  The majority of the setups I see are not sufficient to consistently perform nice snaps.   Consistently meaning the setup is not very tolerant of differing weather conditions (hot vs cold, snapping in/out of relative wind), pilot techniques, or entry airspeeds .   I have on more than one occasion been asked to check a setup for snaps when the owner of the plane was having problems with snaps.   In some instances, I've been able to consistently snap a plane with no changes to the setup, but improvements to the setup made it easier for the owner to consistently snap the plane.   The below descriptions are generalizations based on my experience flying a variety of planes and observing a variety of planes and pilots from a variety of perspectives (amazing how much differently snaps look from different perspectives).   And, the below does not take into acount the effects of wind on track and offer relative descriptions of control throws (exact control throws are influenced by design, weight, pilot technique, etc).   The most critical setup element is pitch - if enough pitch authority is not available, the break can not be achieved - the adjustment to make is more elevator throw, or a more rearward CG (and if neither work, the design has too much stability in pitch to snap properly). 

  - The "twinkle" roll - The plane that has too little elevator, a little bit of rudder, and a boatload of aileron.   Very common.   The plane has little or no displacement from track (or the path is an extremely tight barrel) during the "twinkle" and returns to the original track with zero displacement or deviation in track.   The rotation rate is probably equivalent to a full stick deflection aileron roll (might be marginally higher due to a slight assymetry in lift between wing panels caused by the minor amount of rudder used).   The tail follows the nose exactly and no "cone" is inscribed.   The advantage of flying a "twinkle" roll is that there is very little if any loss in track, the entry is non-critical, airspeed loss in the "twinkle" is minimal, and the only variable the pilot needs to concentrate on is getting the wings level at exit.   As with the stall turn, it is a risk/reward thing - why risk doing a real snap if the "twinkle" is getting scored?   The other benefit of the setup for a "twinkle" is that less elevator throw is used, and that makes the plane smoother in all other manuevers . 

  - The "barrel" roll - this one can be easy to see, or hard to distinguish from a snap, and the setup that yields this result is often variable.   A very tight diameter barrel roll is hard to distinguish from a good snap because it will exhibit a pitching element on entry and the plane will displace from track in pitch and yaw during the snap, but will generally return to track for full snaps (1, 2, 3....rotations) and generally remain displaced of the track (in pitch and yaw) by the diameter of the barrel for 1/2 snaps (.5, 1.5, 2.5 ....rotations).   Very little if any cone inscription is visible after the entry to the barrel.   The large diameter barrel has the same characteristics of tight diameter barrel, but easy to see, simply because of the large diameter alone.   Any change in the control inputs during the "barrel" are generally very easy to see - because the plane is not stalled and responds readily to any change in surface deflection. Insufficient elevator to initiate the break is generally the cause of barrels.   Adding aileron usually increases the rotation rate, and often reduces the diameter.   Adding rudder may reduce the diameter of barrel, increase the rotation rate, give the appearance of the inscription of a cone (but it is only in yaw, and not in pitch, and the airplane is not in a stalled condition), and may also add the look of a "cartwheel".   The benefit of the "barrel" setup is that less control throw is used (smoother in other maneuvers), the rotation rate is slow (easier to hit exit) and the track is unchanged (but might be dispaced ). 

  - The "good" snap - I hope we know what it is in writing by now (actually seeing it takes practice), so just some notes.   Theoretically, the break can occur without displacement in pitch - but this never happens in practice (angular acceleration, mass, and other physics properties are real.........blame Newton).   A good clean break (very fast elev servo and fingers) will reduce the amount of track deviation and displacement in both pitch and yaw.   The rotation rate of the snap will be marginally effected (if at all) by low / high rate aileron - ailerons don't work very well when the plane is stalled. 

  Piloting Technique and more setup - To me, a good setup for snaps has a bigger "sweet" spot - the exact entry airspeed and exact timing of the control inputs can vary and still yield a good snap.   And the good setups "feel" the same whether snapping left or right, positive or negative.   I fly with triple rates - normal flying is rud on high, elev and ail on medium.   For spins, everything is on high.   For snaps, I use a variety of rates setup to make the variety of snaps feel balanced and I attempt to get the snaps from different perspectives in different manuevers to "present" the same.   It takes a lot of time to setup. The technique for all types (different rotations in different attitudes) of snaps is similar (lead with elevator, then rudder, then aileron) but the timing of each input usually varies a bit on both the addition and removal of the inputs.   And each specific snap is usually a little different - I "feel" the plane approaching the entry to the snap and try to gauge exact airspeed, wind condtions , evaluate what the track is and if I want to change the track, etc.....and then I make very small changes to the addition of the inputs to get the desired effect ( ie , I might use more elevator lead to change the track in pitch if the plane was diving slightly in pitch track prior to the snap, or lower than usual on airspeed).   During the snap itself, I watch the progression of the snap and decide if I got the entry I wanted (expected), and if I need to make any changes on the timing of the removal of control inputs on the exit of the snap ( ie , maybe hold the same rudder or imediately go to opposite rudder on the exit to immediately correct a deviation in yaw track).   The more I fly, the better I can make these adjustments because I seem to see things better, the snaps seem to take longer, my fingers seem to move faster, and I better know what the mental image of the plane should be at any instant during the snap. 

  "Tells" and "cheats" One of the easiest snaps to judge is the 45 downline snap (airplane is upright and executing a single positive snap).   The airplane is front and center, and the break in pitch is easy to observe - and it is actually easy to confirm.   Odds are, if you don't see a break, you will see the track of the line steepen as the airplane passes through 90 degrees of rotation - because the rudder is now "bottom" rudder (and the plane is still flying, or if snapping, the break was in yaw, not pitch), and the track of the plane will be steeper than 45 degrees at the finish of the snap.   Kinda of odd to see a 45 downline get steeper after a positive snap??   Big tell, and pretty common to see.   I see the same thing on 1.5 snaps on a 45 downline .   The same thing also happens on 45 uplines when the line substantially flattens out after the snap, but with an added variable - the flattening may be partly due to reduced airspeed and gravity (but the plane will show the initial loss in track at the 90 degree point in rotation). 

  Exits - exits are generally judged more critically than entrances - for snaps, rolls, and radii. A "cheat" to help with the exit of a snap is to take out elev and rud before the snap is complete - such that all the pilot is doing is completing a roll to level flight, and completing a roll is easier than completing a snap - the tell is a substantial change in roll rate (rotational inertia exists and for our models, the heavy wing monster that appreciably demonstrates this is rare).   This type of cheat is also employed on spin exists and on the exit of part and full rolls.   The roll rate is slightly reduced as the rolling element nears completion to make it easy to nail wings level.   Most judges will downgrade for the wings not being level, fewer will catch the change in roll rate.   The same thing applies to corner radii - they are often softer close to the exit to make it easier to hit the line.   The reason the cheats are employed is because downgrades are not being applied - "no whistle, no foul". 

  How do some guys maintain distance during the entire flight (including stall manuevers ) when flying in a crosswind?   They don't.   They are just sneaky at hiding the wind drift, and make corrections / allowances where they are the hardest to detect.   Humans having pretty poor depth perception at 150 meters also helps.   This past fall, I had a trusted observer stand in the field underneath my flight track and was told that the flight track was about 145 meters, +/- 3 meters (a bit more variation after spins).   And the observer was surprised to see how visible the rudder corrections were - as the same observer saw far fewer rudder corrections when viewing similar flights as my caller. 

  Prior to spins and stall turns, you will usually see a very small "cheat" into the wind, and then a little drift with the wind allowed immediately after the stall manuever , followed by a small "cheat" into the wind to return to the original track.   A single 15 degree change in track is easy to see and downgrade.   Very aggressive compensation for wind (difference between attitude and track) while technically correct rarely scores well. Three 5 degree changes in track are harder to see and harder to downgrade, and present nicer (even if not as correct technically). 

  With snaps - to hide the lateral displacement and yaw track change in a snap, the "cheat" is normally opposite the direction of the snap prior to the snap entry - 5 degrees nose in before a snap and 5 degrees nose out after the snap is harder to detect than simply being 10 degrees off after the snap.   And of late, there is no doubt in my mind that being 10 degrees off before the snap will earn little or no deduction if the exit of the snap is nailed.   All deviations in roll, pitch, and yaw track should be equally downgraded whether before or after the snap - it is a goal that needs to be achieved.   The change in track during a snap can often be hidden (or mitigated) to a large extent by wind - this is simply smart piloting by choosing to snap into (usually) the wind.   And in the instance of a snap at the end of the box, where the displacement or loss of heading in yaw is particuarly easy to see, a more pronounced and aggresive break in pitch can be used to minimize the deviation in yaw, as the deviation in pitch is harder to see (and thus harder to downgrade). 

  Regards, 

  Dave DaveL322 at comcast.net " 

Vicente "Vince" Bortone 

----- Original Message ----- 
From: "Dan" <warrior523@ mchsi .com> 
To: "General pattern discussion" < nsrca -discussion at lists. nsrca .org> 
Sent: Sunday, October 11, 2009 6:14:39 PM GMT -06:00 US/Canada Central 
Subject: Re: [NSRCA-discussion] Snap 

No pitch break = no snap roll.  It' s not a matter of anyone's opinion, it's an aerodynamic fact.  If it' s truly this hard to judge, they should simply be eliminated. 

Ed 

Okay if you say so but what is it if it is not a barrel roll or an axial roll?  Certainly it is a snap, and certainly there is a pitch break but it does not have to come before the rotation it can happen simoultaneously.  I can fly level or vertical (up or down) or at any other angle in between and flip my elevator stick repeatedly from one end of a line to another and my plane does not stall (oops I know I should say the wing or wings do not stall)  The arguement for a pitch break is fascious reguarding our models.  I go ahead and do the bump prior to the snap if that is how the judges at that time want it, but to say that a plane did not snap just because there was not an  initial pitch break does not equal actuality.  

Dan 

----- Original Message ----- 
From: Ed Alt 
To: General pattern discussion 
Sent: Sunday, October 11, 2009 5:45 PM 
Subject: Re: [NSRCA-discussion] Snap 

----- Original Message ----- 
From: Dan 
To: General pattern discussion 
Sent: Sunday, October 11, 2009 5:12 PM 
Subject: Re: [NSRCA-discussion] Snap 

I know better than to enter this conversation but, but, well here goes.  Don, I agree with your post about the three types of rolls.  If it is not axial and it is not a barrell roll the it is a snap roll.  Some one at some time put in the description of a snap the requirement of a ptich break.  Man has this caused problems.  Now tell me if a plane does a snap roll without a leading pitch break then what roll was it, axial, nope don't think so.  Was it a barrel roll, nope not that either so low and behold it must have been a snap roll.  We have all set in a judging chair and watched snap manuevers and we have flown these maneuvers.  We can all say that we have seen and or flown many true snap rolls that did not have a any visible pitch break, some are judged on our 1 to 10 scale and others at times receive the zero.  In the current Masters sequence the 45 degree downline snap for example.  I have flown that manuever many many times and I have thrown in the "required" pitch bump and I have at times neglected to do the bump, but you know what, in either method the airplane performed a snap roll. 

I have been flying pattern since the late sixties and going all the way back to then I have know and been able to recognize a stall turn and its difference from a hammerhead turn.  I for the life of me it seems that a stall turn is named very aptly. 

Some of us live for the nitpicking discussions of stalls and snaps and wording in maneuver descriptions, others just want a simple description and go out and fly or judge it to our perceived perfection.  Is it any wonder we seem to be decreasing in our numbers.   

Dan Curtis 

----- Original Message ----- 
From: Vicente "Vince" Bortone 
To: General pattern discussion 
Sent: Sunday, October 11, 2009 7:47 AM 
Subject: Re: [NSRCA-discussion] Snap 

Amen.... 

Vicente "Vince" Bortone 

----- Original Message ----- 
From: "Ed Alt" < ed_alt at hotmail.com > 
To: "General pattern discussion" < nsrca -discussion at lists. nsrca .org > 
Sent: Sunday, October 11, 2009 7:33:56 AM GMT -06:00 US/Canada Central 
Subject: Re: [NSRCA-discussion] Snap 

Don: 
I don't agree with that. You need to see a distinct pitch break and yawing action to accompany the pitch break, otherwise there is no real evidence that autorotation occurred. "Tail coning" alone is not even a reliable indicator of a snap.  You can easily cheat that to sell a "snap".   A snap is a stalled wing, autorotation maneuver. Also, the tendency to downgrade snaps because of any line displacement goes entirely against the physics of what must occur in order for a real snap roll take happen.  I think we should have a rule that most clearly accounts for the physics of what must occur for it to be a real snap, or just take them of sequences entirely.  And of course, educate judges and pilots accordingly.  Also, when you're a judge, don't be afraid to zero or severely downgrade a wiffle snap, or whatever is being presented to you if it's not a real snap. Especially don't be afraid of zeroing snaps when it's a big name trying to sneak a snap cheat in front of you. 

Regards, 
Ed 

----- Original Message ----- 
From: Don Ramsey 
To: 'General pattern discussion' 
Sent: Sunday, October 11, 2009 7:01 AM 
Subject: [NSRCA-discussion] Snap 

Ok, how about this for the snap?   “If its not a barrel roll and not an axial roll, it’s a snap.” Maybe have the coning of the tail in the description. This eliminates about 90% of the judging differences. 

Don 

From: nsrca -discussion-bounces at lists. nsrca .org [mailto: nsrca -discussion-bounces at lists. nsrca .org] On Behalf Of Bob Richards 
Sent: Saturday, October 10, 2009 8:09 PM 
To: General pattern discussion 
Subject: Re: [NSRCA-discussion] basic judging question (warning 4 letter word) 

I think changing the judging criteria, just for the snap part of the manuever , would suffice. 

--- On Sat, 10/10/09, John Ferrell <jferrell13 at triad.rr.com> wrote: 

? 

I believe " We could fix most of that, by assigning a low K to snap maneuvers" is the only appropriate solution. If you cast them out, it is giving up. 

John Ferrell  W8CCW 

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