[NSRCA-discussion] Snap entry in FAI

Mon Jun 30 08:48:21 AKDT 2008

Autorotation for a snap roll requires at least a partial stall, which you can achieve with a sharp pitch break and a kick of the rudder.  The advancing wing picks up speed, the retreating wing loses speed, making the retreating wing more susceptible to an accelerated stall.  It may be that none of the wing gets completely stalled, but the retreating wing just produces a lot less lift than the advancing wing. The retreating wing is also blanked a little bit by the fuselage yaw getting in the way of the air stream, so it probably loses some lift from that as well.  So, the model tends to autorotate in the direction of the rudder being applied.  Application of ailerons makes it much more controllable, to get the rate of rotation up and to help keep it on a line.

Saying that it is acceptable for the model to demonstrate departure in all three flight axis simultaneously is saying that it is allowed to roll prior to autorotation without downgrade, which is not correct.  This is because it always takes some finite amount of time for the pitch break to develop, so if you hit a snap switch, or jam all controls exactly at the same time, you are assured that some amount of rolling movement at the onset was not achieved in a stalled condition, however the rest may have (should have) been.  That roll prior to autorotation should be downgraded.  The best we can really hope for as judges pinned to the ground is that if you see a good pitch break slightly preceeding the rolling, then an autorotation may have been involved.  Some displacement in the direction of the pitch break must occur; another good clue, not a defect in and of itself.

Ed

Date: Mon, 30 Jun 2008 08:15:19 -0400From: jim.woodward at baesystems.comTo: nsrca-discussion at lists.nsrca.orgSubject: Re: [NSRCA-discussion] Snap entry in FAI

Hi John – GREAT points.

This is why I feel that the snap-roll definition is totally out of whack.  Using the ‘stall’ approach to formulating the definition, or any comparison to actual full scale aerobatics, is totally unwarranted and not applicable to a pattern plane.  We need a “50-word-or-less” approach to this maneuver definition and I’d like it to read something like this:

Snap Roll:  The model must autorotate through the described angular rotation in the direction indicated by the maneuver description.
Definitions:

Autorotate:  Model demonstrates departure in all three flight axis which may occur simultaneously.  If the autorotation is perceived to be led by a pitch break just prior to the autorotation, it is not cause for downgrade.

Simultaneous:  same time.
Direction:  Positive snap-rolls pitch towards the canopy, Negative snap rolls pitch towards the belly.

Judging Notes:  The judge is looking for two things to occur for the maneuver to be fully scorable:  Autorotation and the correct direction.  If there is autorotation and the plane went the correct direction, the maneuver is score able but subject to the 1 point per 15 degree rule.  If the judge perceived that the model rolled prior to the autorotation was initiated, the 1 point per 15 degree rule is applied.  If the judge perceived that model stopped autorotating prior to the completion of the described angular rotation, the 1 point per 15 degree rule is applied.  This is typically referred to as “Aileroning in or out of a snap-roll.”  

Anyway – that’s my take on it.  Lets take all this arm-chair aerodynamic bologna out of the definition and create something that is both flyable, and judge-able.
Thanks,
Jim

From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of John GayerSent: Sunday, June 29, 2008 11:46 PMTo: General pattern discussionSubject: Re: [NSRCA-discussion] Snap entry in FAI

The only way to have a steady-state high alpha with a low pitch attitude is to be descending with nose high. Alpha is based on relative airflow.I would like someone to explain how, if the wing, or one panel, is stalled how the ailerons are continuing to control the direction of rotation. If there is a stalled wing, then it will be the one with the "down" aileron as that wing has the higher incidence angle. This stalled panel would cause a roll contrary to the aileron deflection. This is actually what happens when you get an oeverweight airplane too slow and add some surface deflections. It will snap contrary to the aileron.As we perform snap rolls in pattern, I do not  believe there is any stall involved at all. The manuver is all "smoke and mirrors". In which case the rulebook is always right as it defines the maneuver to be performed. Perhaps flick roll is the better name.Johnchris moon wrote: 
Thanks Del. We are actually on the same page. My points were directed more generally than towards anyone who is posting to this topic. I just wanted to make it clear that personal preferences are not a judging parameter and that exaggerated elements in order to please someone who is looking pretty much only for certain elements of a maneuver rather than the whole is also wrong. Also, I read posts where people clearly don't understand the difference between aircraft pitch attitude and angle of attack. Two very different things. I see time and again people (yes, me too) get whacked for not showing some silly 40 degree nose up attitude in order to "prove" the plane stalled before beginning a spin. A wing of course is flown by angle of attack and a plane can be at a high angle of attack yet a "low" nose high attitude to the ground. So, a high angle of attack and a true stall can occur at a relatively low nose high attitude relative to the ground but how often is it downgraded or zeroed because the judge does not know the difference between the two? All of the time. I see and hear it all of the time. "He could not have stalled because the nose was not high enough" Wrong, wrong, wrong.This link has some basic info for those who want to read even more:http://www.aerospaceweb.org/question/aerodynamics/q0165.shtmlI also agree that judging is way better than before in just about every respect. We can always make it better of course and these discussions make some mad and some frustrated but enlighten others. If one does not truly understand basic aerodynamics, then they cannot become a good judge. The concepts of pitch attitude and angle of attack are key to understanding stalls and snaps so they are key things that we all must understand. Understanding the difference makes judging these maneuvers so much easier.AMA vs. FAI I also agree completely about having to change gears when judging these classes back to back at a contest. Even trying to keep the rules straight for the 2 types is difficult at best.I hope as well as others that you can continue participating in pattern with us! We need everyone.ChrisDel wrote:> Chris...> Please!!! don't take this personally directed at/ _you_/ or any _one > individual_. The list is a great medium to have intellectually > stimulating discussion that often is educational.> Judging is an arbitrary art. Do we all have the same calibrated > eyeball? No.. But all judges should be seeing and judging the same > maneuver with similar downgrades. Are all downgrades going to be > identical.. Not realistically ~ No.. Is that the best we can do.. > possibly..? The NSRCA has worked hard with many volunteers over the > years trying to enlighten and improve the caliber of judging and it is > much better than it was 20 years ago..> At this stage of evolution when the judges are reduced to nit picking > shows how well the judging has improved for the overall big picture. > Is it realistic to stop the nitpicking.. It is part of the beast we > enjoy to participate in.. Some terminology in the judging guide could > be tweaked and improved on for those that like to over analyze. The > snap by its very nature if often judged just on the merits of the snap > itself which no judge should ever do. Entry and exit are also worthy > of their focus. That snap in some cases happens in less than 1 sec. It > is always going to have disparity in the scores just based on the fact > not all eyes see and recognize all the details they need to catch in > that sec. let alone feeling burnout or watery eyes etc. that make a > judge miss something.> It is hard to expect all judges to shift gears from FAI to AMA and > back again during the same day or same contest. Dwindling numbers make > that a reality.> I will always contend that your mission as a pattern competitor is to > show the judges to the best of your ability what the rule books > describes. As a pilot if you try to change your flying to what one > given judge expects your are hurting yourself and your overall > performance. I guess that is why they still insist on throwing out > some judges scores at the major competitions. Wish it weren't so but > that is also part of the process.> I personally didn't read anyone saying they were judging by the way > they like it.. I may have missed some posts but what I read, some were > showing, for clarification, that some statements being made, where in > error and just trying to clarify what the specific rule actually > states... Not what someone interprets..> I have always had an issues in FAI judging when 2 pilots flies > identical maneuvers and one flies consistently 5 degrees off in > track/heading and the other flies on the rail do they both deserve a > 10 if all elements in the maneuver have been done per the rules? Some > argue that 1 point / 15 is applied before they get to a 15º error.. > others read it to mean that your don't give a down grade till at least > 15º of track have been shown. Thankfully in AMA we have the 1/2 points > to work with.> So yes you are right that no judge is to judge based on what they > prefer except when it comes to style and presentation ~ the lower > criteria for downgrades.> ~~~ Who gets the better score...? Dean Pappas once told us that the > one that hides their corrections the best. That alone is another art > /subject. So when judging ~~ do you best to be consistent and fair to > all.. When flying ~~ do your best to show the judges you do know how > to fly the maneuvers without any detectable errors. Learn to hide your > corrections.> I sincerely hoped I helped Chris. Feel free to comment on or off list > as you feel apropos. I still love the sport and what it has to offer > but am having to give it up ~~ possibly forever.. only time can tell..> Del>> ----- Original Message -----> *From:* chris moon > *To:* nsrca-discussion at lists.nsrca.org> > *Sent:* Tuesday, June 17, 2008 12:15 PM> *Subject:* Re: [NSRCA-discussion] Snap entry in FAI>> Is it not the pilot's responsibility to simply fly the maneuver as> depicted? Why then must they exaggerate a portion to placate a judge> who wants to see it their way? Our judging training materials> distinctly say not to downgrade just because the maneuver is not done> the way you like. The example was one pilot making sharp corners in a> square loop vs another making larger more rounded corner. Both are> correct and should be judged identically but can anyone argue that> one> way should be downgraded because it was not the way "you like it"> Stalls, snaps and spins are no different. Not the way I like it = so> what. If it is done correctly it is always a 10. I would think> that if> the other judges are consistently giving "normal" scores and I am> zeroing or giving some nominal score, that there has to be an issue> going on. Am I the only one who is consistently right in my thinking> and everyone else is all wrong? Or, could it be the other way around?>> Chris>>>> Del wrote:> > It is the "PILOTS" responsibility to fly the maneuver as> described per> > the rules. If said pilots chooses to not make it obvious or> > discernable to the judge then enjoy the score you should be awarded.> > Del> >> > ----- Original Message -----> > *From:* chris moon> > *To:* nsrca-discussion at lists.nsrca.org> >> > *Sent:* Monday, June 16, 2008 5:11 PM> > *Subject:* Re: [NSRCA-discussion] Snap entry in FAI> >> > George - you have made an excellent point in that the interval> may by> > "minuscule" and not overly noticeable to everyone. It is absolutely> > wrong for some to claim that you must "show" them as judge an> > exaggerated pitch up just to satisfy a personal interpretation> of the> > maneuver. Just as is is absolutely wrong for those judges to demand> > another overly exaggerated pitch up as a stall entry to a spin> > maneuver. It is never the job of the participant to exaggerate a> > portion of a maneuver just to prove it exists, therefore your> > usage of> > the term "minuscule" in terms of the time interval between pitch and> > rotation is something we need to keep in mind.> >> > Chris> >> > george w. kennie wrote:> >> My lip is becoming too painful from biting it, so I think I'm> > going to> >> stick my nose in here somewhere.> >> I think I'm with Jon on this one.> >> My logic, however flawed, tells me that if I am flying my plane> >> straight and level and I input rudder, no matter how much, there> > is no> >> way that this input will induce a stall to the airframe.> > Therefore, it> >> seems to me, that the necessary force required to stall the main> >> lifting surface must come from the elevator. It would further> > seem to> >> me that this input must, by it's very nature produce a pitching> >> attitude to the fuselage whether positive or negative. So I> > would have> >> to conclude that the attitude "break" referenced by the rule can> > only> >> refer to a "pitch" break and would be impossible to confuse> with an> >> attitude change induced by the rudder seeing that the required> > result> >> is to stall the main wing.> >> And yes Jon, I agree that it would be necessary to lead with the> >> elevator in order to bring about this attitude change before> > rotation> >> is started, however miniscule the interval might be.> >> Of course I'm still open to hearing other interpretations and> their> >> validations as these observations are strictly opinions.> >> G.> >>> >> ----- Original Message -----> >> *From:* Jon Lowe> >> *To:* nsrca-discussion at lists.nsrca.org> >>> >> *Sent:* Monday, June 16, 2008 2:10 PM> >> *Subject:* Re: [NSRCA-discussion] Snap entry in FAI> >>> >> Jim,> >>> >> I have no clue how you think all three axes can be initiated at> >> the same time. You keep forgetting the part of the RULE, quoted> >> verbatim below, that says the "fuselage break and separation from> >> the flight path" must happen "BEFORE THE ROTATION IS STARTED". I'm> >> NOT equating fueselage break to pitch break, it could break in> >> pitch and/or yaw, if it doesn't start rotation at the same time.> >> If you initiate all three axis at the same time, rotation WILL> >> start at the same instant, and that is specifically NOT permitted.> >> READ THE RULE! The judge MUST determine if the fuselage broke and> >> separated from the flight path first, BEFORE the rotation started.> >> If it didn't, he MUST severely downgrade.> >>> >>> >> Jon Lowe> >>> >>> >> -----Original Message-----> Klipped 4 reposting>> ------------------------------------------------------------------------>> _______________________________________________> NSRCA-discussion mailing list> NSRCA-discussion at lists.nsrca.org> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion

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