Wind correction / wings level take 2

[Keith Black]

Dave, thanks for taking the time to enlightening us. This is the type of
thing that I really want to understand. I wish we'd have flying technique
discussions more often.

Regarding you explanation, I'm still trying to wrap my mind round this one.
Looking at it analytically my first inclination is to agree with Jim
Woodward's description where he states that when flying a crab angle in a
strong crosswind aileron input is required through each radius to keep the
plane on track. I don't see how this wouldn't be the case, but perhaps I'm
not taking into account the effect of the crosswind on the crabbed plane.

Let's take this to an extreme to illustrate the point. Say the plane is
flying right to left in a crosswind that is so strong that a 45 degree
inward crab is required to keep the plane from blowing out. Now we come to
the center of the box where we pull for a centered stall turn. Since the
plane is facing in at a 45 degree angle I would think a pull without aileron
input would make the nose of the plane go away from the flight line and
expose the belly of the plane. Therefore to prevent this from happening
wouldn't one need to slowly mix in left aileron through the 1/4 loop radius?

This is something I've pondered while practicing by myself may a day.

Second questions: At NATS on Wednesday afternoon there was a pretty stiff
direct crosswind. I felt like I did a decent job of keeping my plane from
blowing out by keeping a continuous crab angle through most of the flight.
However, I didn't score as well as I though I would and to be honest even in
my own opinion the crab angle didn't look too pretty. When some others flew
I notice that they didn't seem to have as much crab angle (this is
especially true when watching the FAI guys).  I'm not sure if this has to do
with air speed (me flying too slow), the type of plane (mine having a great
deal of side fuse area), tricks such as those you listed to cheat the wings
in or corners, or what. Any insight in this area would be VERY MUCH
appreciated.

Thanks to all who help me and other get a grasp on these issues.

Keith Black


----- Original Message ----- 
From: "David Lockhart" <DaveL322 at comcast.net>
To: <discussion at nsrca.org>
Sent: Monday, August 09, 2004 6:42 PM
Subject: Re: Wind correction / wings level take 2


> The "crab" angle needed is the same whether straight and level, straight
up,
> or straight down - assuming airspeed is constant.  Once the "crab" angle
is
> set to get the desired track, no inputs are needed other than those needed
> to maintain the attitude and airspeed (not synonomous with groundspeed) of
> the plane as compensation for wind gusts or altitude variations.  I say
> "crab" in quotes because the airplane is not really crabbing (unless you
are
> holding rudder, or "slipping" with opposite rudder and aileron) - it only
> appears to be crabbing because we (pilots and peanut gallery) are standing
> on the ground (a fixed reference, not moving like the air the plane is
> flying in).
>
> The crab angle needed is simple vectors - direction the plane is pointed
> (attitude) plus the crosswind component equals track of the plane - if the
> track isn't what you want, change the attitude of the plane.  Given
constant
> airspeed, the vector sum (track) does not change whether the plane is
> horizontal or vertical up/down - because the vector sum does not change -
so
> there is no need to use aileron or rudder in the corners or anywhere else.
>
> BUT - always an exception(s) right?  It is very difficult to truly
maintain
> constant speed, and wind gusts are real - so those are some reasons
> adjustments to the attitude of the plane need to be made (whether done
with
> rudder or aileron, the direction of the plane is changed).  And when the
> plane is not on the desired line, the crab angle must be increased or
> decreased to get back to the desired line.  And in strong winds, extreme
> crab angles rarely get scored well - it gets very hard to score a "10" to
a
> square loop that has a 30 degree difference between track and attitude (in
> pitch, assume wind is down the runway), or a stall turn that leans 30
> degrees in yaw (direct crosswind) and only rotates 120 degrees at the top.
>
> Changing the crab angle of the plane (actually changing the vector heading
> of the plane is what we really want) can be done several ways - banking
the
> wing, holding the rudder, or in corners by slightly dropping a wing -
which
> is a "stealth" way to make the change.
>
> I have left out some details - but they get pretty specific to airplane
> design and setup - suffice to say the "best" piloting technique is not
> exactly the same for all planes - but we are getting down to the last
couple
> % at that point.
>
> Regards,
>
> Dave Lockhart
> DaveL322 at comcast.net
>
> ----- Original Message -----
> From: "Wayne Galligan" <wgalligan at goodsonacura.com>
> To: <discussion at nsrca.org>
> Sent: Monday, August 09, 2004 6:43 PM
> Subject: Re: Wind correction / wings level take 2
>
>
> > Ken,
> >
> > The best way to visualize this is get a stick plane.  Hold at a crab
angle
> > say 15 degrees.  The elevator is working at an angle to the intended
path
> > thus the wings will not follow that same path unless corrected with the
> > ailerons.  All your doing is correcting to make the wings level in the
> path
> > and not cheating the angle for wind drift.  I had a mess of a time with
> this
> > and understanding it till I used my stick plane to help draw the path
the
> > plane would take for the given maneuver.  Its obvious if wings aren't
> level
> > when pulling to an up line but gets more complicated when crab angle and
> > push/pull is involved.
> >
> > Wayne Galligan
> >
> >
> > ----- Original Message -----
> > From: "Ken Velez" <kvelez at comcast.net>
> > To: <discussion at nsrca.org>
> > Sent: Monday, August 09, 2004 5:32 PM
> > Subject: Re: Wind correction / wings level take 2
> >
> >
> > >    I still don't understand why are the wings moving or why they need
to
> > be
> > > moved.  If you fly a horizontal line left to right with the same wind
> > > condition as described by Jim, once you achieved the crab angle to
> > maintain
> > > a straight line no more rudder is needed unless the wind changes. The
> > > airplane should maintain that heading and wings level. In case of  the
> > > reverse humpty if you push from the top with the crab angle in and the
> > wings
> > > are level before the push the track is maintained without the help of
> wing
> > > movement. That's what we are looking for anyway, track straight with
> wings
> > > level. If thru that push or pull the wings move I think the problem
lies
> > > somewhere else. As far as Dave Lockhart we fly together some times and
I
> > can
> > > tell you if you see any roll movement thru a loop or loop segment the
> > source
> > > of  the roll correction is other than wind correction. If wing
position
> is
> > > used to wind correct in my opinion it should be downgraded.
> > >
> > > Regards
> > > Ken V.
> > > ----- Original Message -----
> > > From: <js.smith at verizon.net>
> > > To: <discussion at nsrca.org>
> > > Sent: Monday, August 09, 2004 2:41 PM
> > > Subject: Re: Wind correction / wings level take 2
> > >
> > >
> > > While attending the Sayre contest this past weekend, my friend and I
> > decided
> > > to do a little practice judging while Dave Lockhart flew.  We were
> amazed
> > to
> > > see him doing exactly that.blending the roll while executing loops.
In
> > fact
> > > we had a discussion after his flight trying to figure out how he did
it.
> > > Our conclusion was "you roll into the wind" while pulling or
pushing.at
> > > least for quarter loops.
> > >
> > > When Dave flew, you couldn't see the roll correction.just the fact
that
> > the
> > > track was perfect going in and perfect coming out and the wings were
> > always
> > > level or square to the flight line.  A real treat to watch!
> > >
> > > Scott
> > >
> > > >
> > > > From: Jim_Woodward at beaerospace.com
> > > > Date: 2004/08/09 Mon PM 01:39:25 EDT
> > > > To: discussion at nsrca.org
> > > > Subject: Wind correction / wings level take 2
> > > >
> > > > Hi All,
> > > >
> > > > I think discussion about 1 single maneuver will address everything I
> > sent
> > > > initially below.  P05, Reverse humpty-bump, 2/4 down, 1/2 roll up:
> > > > Scenario.  The wind is blowing 20 mph 90 degrees out.
> > > >
> > > > 1.  Entry;  the plane is flying a horizontal inverted track at the
top
> > of
> > > > the box right to left, the fuselage is yawed 10 degrees  inward to
> > > > compensate for the wind.
> > > > 2.  Entry Radius:  Pilot pulls up elevator while simultaneously
adding
> > > > aileron and rudder to transition the plane to a vertically tracked
> > > > downline, fuselage is angled into the wind to maintain vertical
track.
> > > > 3.  2/4 is performed maintaining track (still angled in to
compensate
> > for
> > > > the wind)
> > > > 4.  Bottom radius:  The pilot pushes around the bottom adding rudder
> to
> > > > maintain track, ailerons to level the wings around the bottom, then
> > > > opposite rudder to lean "into" the wind on the upline. (obviously,
> pilot
> > > > nor judge wants to see banked wings at the bottom this maneuver
which
> > > > would result if no aileron was added due to downline cant/angle of
> > > > fuselage to maintain track).
> > > > 5.  1/2 roll is performed still angled in somewhat.
> > > > 6.  Pilot switches rudder input to still compensate for the wind on
> the
> > > > upline.
> > > > 7.  Exit radius:  Pilot pushes out, using rudder to maintain
heading,
> > and
> > > > aileron to create wings level across the top of the box.  Blended in
> > with
> > > > the exit, the plane is now wings level angled "in" to compensate for
> the
> > > > wind, heading into the reverse double I.
> > > >
> > > > There is a lot of "flying" going on in the 3 different radii of this
> > > > maneuver.  The wings/plane MUST actually roll to achieve the various
> > > > "wings-level" positions of the: downlines, bottom radius, upline,
and
> > upon
> > > > exit.  Is this amount of "flying" done in the radii simply addressed
> in
> > > > the wind correction statements like:  "each maneuver must be
> > > > wind-corrected to preserve the overall geometry"?
> > > >
> > > > My contention again is that the plane MUST perform a blended rolling
> > > > element during the radii to create a cross-wind corrected maneuver.
I
> > > > think the best looking thing to do is move the wings at a rate
> > > > proportional to the arc of the radii - thus, you don't "see" a
> discreet
> > > > aileron fix.  A discrete aileron fix at the end of the radii would
be
> a
> > > > certain queue to downgrade.  I believe I've learned the correct way
to
> > fly
> > > > a cross wind condition, but I have not heard anyone really discuss
the
> > > > amount or "flying" going on in the various radii to handle a cross
> wind
> > > > condition.
> > > > Thanks,
> > > > Jim W.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > ----- Forwarded by Jim Woodward/BEA on 08/09/2004 01:05 PM -----
> > > >
> > > >
> > > > Jim_Woodward at beaerospace.com
> > > > Sent by: discussion-request at nsrca.org
> > > > 08/09/2004 09:12 AM
> > > > Please respond to discussion
> > > >
> > > >
> > > >         To:     discussion at nsrca.org
> > > >         cc:
> > > >         Subject:        Wind correction / wings level
> > > >
> > > >
> > > >
> > > > Hi All,
> > > >
> > > > I want to bring up a discussion point about wind correction.  This
may
> > > > seem obvious to some but I want to ensure I have the right picture
in
> my
> > > > mind (started thinking about this since Don S. posted his comments
> about
> > > > Q.S. flying wind correction in finals, and confirmed during some
> > practice
> > > > yesterday).
> > > > 1.  Wind correction is supposed to be done while maintaining wings
> > level.
> > > > 2.  You are supposed to use the yaw angle to correct for the wind.
> > > > Situation:  Pilot is flying a square loop ( at center).  Wind is
> blowing
> > > > 90 degree out 20 mph.  Pilot fly's past center at a some yaw angle
in
> to
> > > > compensate for the wind blowing out.  The pilot pulls a 90 degree
> radius
> > > > to a vertical upline.  The fuselage is canted in to the wind to
> > compensate
> > > > for the wind blowing out.  *Point of discussion:  If the pilot were
to
> > > > pull another 90 degree radius, the wings would become "unlevel" as
the
> > > > plane reaches the top leg of the square loop.  *Point of discussion:
> > So,
> > > > if the pilot is using the correct technique for wind correction
(wind
> > > > correcting force being yaw angle), then every time the pilot creates
a
> > > > radius, you should definitely "see" the ailerons moving the wings
> > through
> > > > the radius to ensure that as the radius is finished, the wings are
> level
> > > > for the next line and the fuselage is yawed for wind correction.
Same
> > > > thing next radiu s;  The pilot adds pitch, moves the wings,  and
adds
> > the
> > > > correct rudder to transform the top of the box line to the next
> downline
> > > > (wings level, yawed into the wind), etc.
> > > >
> > > > *Point of discussion:  We spend a lot of time concentrating on wings
> > level
> > > > for normal pattern flying and usually "any" type of aileron or wing
> > > > movement is a visual key for a downgrade using the 1 pt / 15 degree
> > rule.
> > > > However, this is false to accurately judge flying on a windy day.
In
> > > > order to fly in a crosswind, nearly EVERY radius will have some
amount
> > of
> > > > roll induced (and necessary) to ensure that the "lines" can be flown
> > with
> > > > wings level and in order to utilize yaw as the wind-correcting
force.
> > > >
> > > > That said/ when and how much roll should be used?  I would guess
that
> > you
> > > > would want to seamlessly input the pitch, aileron, and rudder so
that
> > the
> > > > plane just appears to go from one wind corrected line to the other
> > > > magically.  What is the judging criteria for inputting a roll
function
> > in
> > > > the radius to ensure the wings stay level & fuselage stays canted
> > (yawed)
> > > > into the wind from one wind corrected line to another?  Should the
> > amount
> > > > of aileron needed to go from one wind corrected line to another line
> > start
> > > > and finish corresponding to the actual duration of the radius?  What
> if
> > > > the pilot only correct s the wing as the plane is nearing the end of
> the
> > > > radius, is this some downgrade because the correction was placed
near
> > the
> > > > end of the radius instead of "evenly-througout" the radius?
> > > >
> > > > I'm sure I'm exaggerating this situation and I am purposefully, to
> > > > stimulate some talk on the subject.  Again, my contention is that
for
> > some
> > > > wind conditions, in order to maintain the overall geometry of the
> > maneuver
> > > > that there MUST be roll correction during radii to seamlessly move
> from
> > > > one wind corrected line to another, and this roll correction should
> not
> > be
> > > > downgraded.
> > > >
> > > > Any takers?
> > > > Jim W.
> > > >
> > > >
> > >
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