[NSRCA-discussion] Snap entry in FAI

Mon Jun 16 14:13:25 AKDT 2008

Continuing:

We can all agree what a loop looks like and all agree what an axial roll 
looks like right?  The problems begin when we get into the "stalled" 
maneuvers -stalls, snaps,spins.  Different planes behave and "look" 
differently in the stall therefore there cannot be one standard "look" 
for these maneuvers.  Intuitively we know that different designs have 
different airfoils and each plane has different wing loadings depending 
on their weight and will stall differently.  Back to aerodynamics 101 we 
know that a wing stalls when you exceed it's critical angle of attack 
and this angle does not change as far as that wing is concerned. 
Different wings will of course have differing critical angles of attack 
before they stall. So, differing wings designs must look differently as 
they will reach critical angle at different times. The only thing that 
changes is the speed at which the wing will stall if you try to maintain 
level flight while reducing it's airspeed.   So, does a plane need to 
depart from it's original flight path to stall? NO.  It just needs to 
pivot around the c/g to take the wing past it's critical angle of 
attack.  The c/g of the airplane can absolutely maintain it's track 
through the air.  The speed of the rotation in a snap or spin will 
depend on the airfoil and amount of control throws used as well as c/g 
but the key is that you do not have to leave your c/g track through the 
air to stall the wing.  Period.  Same for stalls at the entry to spins - 
you can fly level and reduce airspeed while increasing pitch until you 
bring the wing to and past it's critical angle of attack.  This may be 
15-20 degrees of nose up attitude - not some false 40-45 degree pitch up 
designed to "show" the stall.  Both wings are stalled and should count 
as stalled. Period.  They may look differently, but both are stalled and 
correct.  We need to get away from what "looks" right in a stalled maneuver.

Chris

fire away.......

chris moon wrote:
> 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-----
>> From: Woodward, Jim (US SSA)
>> To: General pattern discussion
>> Sent: Mon, 16 Jun 2008 12:37 pm
>> Subject: Re: [NSRCA-discussion] Snap entry in FAI
>>
>> Jon,
>>
>> I’m shocked - you are totally wrong here. Do not equate “fuselage”
>> to “pitch” in the reading of this definition. As a judge you
>> should NOT apply a “pitch-assessment” pass/fail criteria to
>> judging FAI snap rolls. It is completely rejected. The plane and
>> therefore “fuselage” must autorotate about the flight axis, which
>> means that the nose and tail of the plane will move in a conical
>> fashion. The pilot can initiate with all 3 axis at one time.
>>
>> It is the responsibility of the judge to determine if autorotation
>> occurred, and not determine how or in what order the pilot did it.
>>
>> Thanks,
>> Jim
>> ------------------------------------------------------------------------
>> *From:* nsrca-discussion-bounces at lists.nsrca.org
>>
>> [mailto:nsrca-discussion-bounces at lists.nsrca.org
>> ] *On Behalf Of
>> *Jon Lowe
>> *Sent:* Monday, June 16, 2008 1:21 PM
>> *To:* nsrca-discussion at lists.nsrca.org
>>
>> *Subject:* Re: [NSRCA-discussion] Snap entry in FAI
>> You are correct, as long as there is no roll induced at the same
>> instant. I overlooked that possibility. Not sure how rudder alone
>> will induce the "supposed to be in a stalled condition" though!!
>> There are many attitudes (e.g. 45 down on center) where a judge
>> could not likely see a rudder departure alone first, and thus
>> conclude that departure did not occur before the roll departure
>> started. And a judge might also not see a pitch departure first on
>> a end box upline snap, but he could see rudder first. It is VERY
>> clear that simultaneous roll with either or both of the other axes
>> departures is NOT allowed as others have tried to state here. I
>> did say that pitch and yaw departure could happen simutaneously,
>> in my original post, as long as roll doesn't occur at the same time.
>> Jon Lowe
>>
>>
>> -----Original Message-----
>> From: JShulman>
>> To: General pattern discussion
>>>
>> Sent: Mon, 16 Jun 2008 11:22 am
>> Subject: Re: [NSRCA-discussion] Snap entry in FAI
>> Jon,
>> I don't see where it says pitch break? Rudder first will show
>> attitude break and separation from the flight path. So if one uses
>> rudder and elevator first this is also correct.
>> Regards,
>> Jason
>> www.jasonshulman.com
>> www.shulmanaviation.com
>> www.composite-arf.com
>>
>> -----Original Message-----
>> *From:* nsrca-discussion-bounces at lists.nsrca.org
>>
>> [mailto:nsrca-discussion-bounces at lists.nsrca.org
>> ]*On Behalf
>> Of *Jon Lowe
>> *Sent:* Monday, June 16, 2008 12:11 PM
>> *To:* nsrca-discussion at lists.nsrca.org
>>
>> *Subject:* Re: [NSRCA-discussion] Snap entry in FAI
>> I suggest people re-read the definition ofsnap-rolls from the
>> FAI sporting code. I did a few minutes ago. Here it is:
>> "5B.7.5. *SNAP-ROLLS*
>> A snap-roll (or flick roll/rudder roll) is a rapid
>> autorotative roll where the model aircraft is in a stalled
>> attitude, with a continuous high angle of attack
>> Snap-rolls have the same judging criteria as axial rolls as
>> far as start and stop of the rotation, and
>> constant flight path through the manoeuvre is concerned.
>> At the start of a snap-roll, the fuselage attitude must show a
>> definite break and separation from the
>> flight path, before the rotation is started, since the model
>> aircraft is supposed to be in a stalled
>> condition throughout the manoeuvre, If the stall/break does
>> not occur and the model aircraft barrelrolls
>> around, the manoeuvre must be severely downgraded (more than 5
>> points). Similarly, axial
>> rolls disguised as snap-rolls must be severely downgraded
>> (more than 5 points).
>> Snap-rolls can be flown both positive and negative, and the
>> same criteria apply. The attitude
>> (positive or negative) is at the competitor’s discretion. If
>> the model aircraft returns to an unstalled
>> condition during the snap-roll, the manoeuvre is severely
>> downgraded using the 1 point/15 degree
>> rule."
>>
>> Note that "the fuselage attitude must show a definite break
>> and separation from the flight path, before the rotation is
>> started..." That means that simultaneous pitch and rotation is
>> specifically NOT permitted. I would interpret it as meaning
>> that pitch and yaw could theoretically happen simultaneously,
>> as long as no roll is involved. Sorry Matt, the rules as
>> written do NOT allow actuation in all three axes
>> simultaneously. The rule also states that a constant flight
>> path has to be maintained.
>>
>> Let's face it, the only way to prevent severe downgrading from
>> EVERY judge, not just some judges, is to have a pitch break
>> first. Takes any question away.
>> Jon Lowe
>>
>>
>> -----Original Message-----
>> From: rcmaster199 at aol.com
>> To: nsrca-discussion at lists.nsrca.org
>>
>> Sent: Mon, 16 Jun 2008 10:46 am
>> Subject: Re: [NSRCA-discussion] Snap entry in FAI
>> A "Flick" and a "Snap" roll are the same roll in full scale
>> aerobatics parlance and reference material.
>>
>> Do these mean the same thing in model aerobatics? In my view,
>> they do
>>
>> The latest FAI regs allow actuation of the three main axes
>> simultaneously...that is, the regs don't specifically
>> differentiate "Pitch Break" from other deviations. I don't
>> think they specifically require that the model must rotate
>> about it's flight path either, I don't believe (.....plane
>> must rotate in a conical fashion about the fight axis....).
>> The model would probably present the best if that's done, so
>> pilots may want to consider that when executing the maneuver.
>>
>> In my take, a rapid Pitch is desired to preload the wing.
>> Contrary to popular belief, both panels dot not have to stall
>> for a snap to occur. Quite the opposite. Upon rudder
>> deflection, the port panel will practically stall (lift much
>> much less than the other panel) but the starboard panel must
>> be lifting to create the autorotation. If both panels stall,
>> the model will fall out of the sky for a distance and a snap
>> would not occur at the correct moment in time
>>
>> MattK
>>
>> -----Original Message-----
>> From: Woodward, Jim (US SSA)
>>>
>> To: General pattern discussion
>>
>>>
>> Sent: Mon, 16 Jun 2008 8:47 am
>> Subject: Re: [NSRCA-discussion] Snap entry in FAI
>>
>> Guys,
>>
>> I thought the FAI changes explicitly allowed flick rolls? The
>> rule
>> reads, "... fuselage attitude must show a definite break and
>> separation
>> from the flight path."
>>
>> It does not say, "MUST SHOW PITCH BREAK." Please DO NOT
>> ERROUNIOUSLY
>> APPLY A PASS/FAIL MAJOR DEDUCTION initial assessment to the
>> snap roll.
>> Watch the whole maneuver then render your score.
>>
>> A break and separation from the flight path simply means that
>> the nose
>> and tail of the plane must rotate in a conical fashion about
>> the fight
>> axis. Yaw, roll, and pitch can all break at the same moment if
>> that is
>> how the pilot does it.
>>
>> Hey :) some really handsome smart guy wrote some stuff at this
>> link
>> below about snap rolls to help clarify how they are done in IMAC.
>>
>> http://www.mini-iac.com/DesktopDefault.aspx?tabid=77
>>
>> thanks,
>> Jim
>>
>>
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