If it Flies...-2010/08

74 MODEL AVIATION
mph crosswind will provide a nice challenge
during landing.
Nailing a three-pointer in these conditions
is worth more than 20 great landings in easy
conditions—and your flying buddies notice.
Simply flying figure eights above the runway
and compensating for a considerable breeze
so that all crossovers are in the same place
will help you call the wind your friend.
There are three big challenges when flying
in the wind. Landing is the biggest, despite
the fact that taking off is the first one you’ll
face. Once in the air, planning your turns so
your model ends up where you intended it to
be will help create the impression of complete
control.
Let’s start with that takeoff. If the wind is
blowing straight down the runway, things are
going to be much easier than if there is a
crosswind. But there are still precautions we
should take to maintain positive control.
Airspeed is your friend. Repeat this
newfound mantra to yourself several
times. I’ll wait.
Okay, now that this allimportant
principle is fresh
in your mind, it’s time to
look at the nature of the
wind itself. Sometimes it is
steady, but that is the
exception rather than the rule.
The wind varies, sometimes
suddenly, and it is wise to
plan for these gusts.
Challenge the wind and win
Dean Pappas | DeanF3AF2B@If It Flies ... pappasfamily.net
If the wind suddenly dies off during
takeoff, for a moment you will have that
much less airspeed. The model will recover
its normal climbing airspeed in a second or
two, but if you were climbing steeply, that
momentary loss of airspeed could lead to a
partial loss of control or even a stall.
One hates to harp on the subject of safety,
but takeoffs generally happen close to people,
so any loss of good control authority during
takeoff constitutes something of a safety
hazard. I learned this the hard way when I
was maybe 13.
It was the kind of day I described earlier in
this column: windy, gusty, and almost directly
down the runway. My trusty T-45, a greatflying
40-sized sport/RC Aerobatics (Pattern)
aircraft that probably qualifies for one of the
Nostalgia Pattern events these days, climbed
steeply as I commanded as is only possible in
such a headwind.
When only 40 or so feet from the ground,
the wind stopped. The airplane stalled and
immediately did a half snap roll, and then
headed straight for the ground. The pullout
would have been complete at minus 2 feet.
The crash occurred on the runway, and some
of the pieces came to rest not all that far from
the other pilots’ feet.
Sobered by the experience (after all, those
feet belonged to my friends and they weren’t
too bashful to let me know that I had been
stupid) and annoyed at losing a good aircraft
at the beginning of the flying season, I went
back to the workshop to build my third T-45.
HI GANG.Where I live, wind has dominated
the weather these last few weeks. Around here
it’s called spring: a handful of gorgeous days
interspersed with high winds and rain. It put
some backyard lawn furniture into orbit and
shattered the neighbor’s glass-topped picnic
table into his pool. Ouch!
Wind is part of the landscape, so get used
to it. When the trees are bending, you might
as well leave the airplane in the workshop or
drive to the flying field, leave the model in the
car, and join the hand-flying session. My club
keeps a few kites in the maintenance shed,
and they often come out on those too-windyto-
fly days.
Maybe you are so eager to fly that you
consider risking your aircraft anyway.
Hopefully, and I think this is the best-case
scenario, you feel the fresh breeze in your
face and look forward to the challenge it
presents.
Yes, wind-flying is a challenge that offers
the finest sense of accomplishment. A
howling gale isn’t required. Even a 5 or 10
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So the first lesson is to keep plenty of
airspeed immediately after takeoff and until
you have plenty of altitude. That means full
throttle and a moderate climb angle.
A crosswind adds another element to the
task. Airspeed is still your friend, because it
helps you maintain control. That control will
help you preclude the wind from “getting
under” the windward wingtip.
Once the wind has rolled a model such as
the T-45, immediate correction is needed to
prevent it from becoming a kite instead.
Therefore, on days with a fair bit of crosswind
you should begin the takeoff roll already
holding the aileron control partway into the
wind.
Keep the airplane straight on the runway
with the rudder, as usual, so that the
momentum of the aircraft is in the direction of
the runway. Gradually reduce upwind aileron
control so it is almost gone at the instant the
model leaves the ground.
The airplane’s momentum will tend to
keep it headed straight down the runway for a
second or two afterward, and as long as the
wings are level, the aircraft’s yaw stability will
“weathervane” it so that it flies straight
compared to the relative wind. Yes, the model
will naturally assume the correct crab angle for
climbout, provided it was headed straight just
before liftoff and the wings are kept level (or
briefly upwind wingtip low) throughout the
process.
Some of you may have noticed that one
thing not mentioned in the preceding is the
idea of continuously holding rudder control
into the wind. It’s not desirable and not
helpful. The airplane flies best when it is
flying coordinated; that is, neither slipping nor
skidding sideways.
When an airplane is slipping or skidding, it
is draggier than normal and responds to
changes in wind and airspeed in different and
often undesirable ways. A good example is a
snap roll resulting from a stall that occurs
while the pilot is holding some rudder control.
There is one time when a sideslip is useful
in crosswind conditions: during landing. I will
go into that later, but a proper sideslipped
crosswind landing is an advanced flying
technique that few ever master.
Another useful technique is an intentional
sideslip used to make the airplane draggier,
temporarily, so that altitude can be dumped
without speeding up undesirably. Here, care
and practice are needed to avoid the stall/snap
roll/spin scenario that can result.
When taking off or landing, whether there
is a crosswind or not, the general rule is to fly
the airplane coordinated. Wind or not, if the
model is drifting to one side as you try to fly
along the runway, you don’t fix it by standing
on the rudder or intentionally missetting the
rudder trim; you turn the model until it’s
headed the right way. That’s almost too
obvious, isn’t it?
A few months ago, we spent a fair bit of
time figuring out how to trim the ailerons and
rudder so that the aircraft is flying straight and
clean, so why mess that up? The trick is in the
subtle difference between “pointed” and
“headed.”
Did you ever row a boat across a river?
The same is true when you are flying around.
It helps to plan the exits of your turns; exit a
few degrees early or late, so you can point the
airplane into the sidewind a bit when the turn
is done.
With a bit of practice you will learn to hit
the angle close enough that the fine-correction
turns will be hardly noticeable—just shallow,
banked turns to nail those last few degrees.
Come to think of it, this is good
preparation before setting up for landing on a
windy day. Fly your approach at a comfortable
flying-around altitude, with the intent of flying
directly above the center of the runway. Finish
the turn to the runway heading in your
customary place, level the wings, and keep
them level while carefully watching what
develops. Does the model drift in toward the
flightline or out away from it? How quickly
can you detect it?
If the aircraft needs to be turned to get it
headed in the right direction, don’t be shy
about it. Execute a turn the way you always
do: bank, pull, and level. The sooner you catch
it, the more shallow-banked turn can be used
to correct it before the airplane travels far in
the wrong direction.
Ninety-nine percent of all crosswind
landings with RC models are flown down the
runway with the course correction(s) that
counteract the effect of the crosswind. The
important thing is to be alert and not allow a
gust of wind to bank the aircraft downwind. If
it is drifting with the wind, turn it toward the
wind a little—okay, maybe a lot!
Once you feel like you have mastered this
technique, it is time to add a refinement. As
you are set to touchdown with the airplane,
bank it slightly into the wind and straighten it
to the runway with rudder input in the “with
the wind” direction.
The goals are:
1) To do this just enough that the wheels
contact the ground rolling straight instead of
scrubbing sideways on the runway.
2) To do this so low to the ground that
when you bank the aircraft into the wind, the
upwind wheel touches down immediately.
That’s how most full-scale airliners are
landed these days. That’s what works
consistently and minimizes the beating that the
airplane and landing gear would take from
contacting the runway at an angle.
The advanced technique is closer to what is
used when flying full-scale lightplanes. The
“bank into the wind and rudder the airplane
straight at the last moment” technique I
described is exaggerated so that your model is
flying banked into the wind for the last two or
three seconds of the landing approach, while
opposite rudder is used to keep the nose
pointed directly along the runway.
Do it right and it looks great, but don’t be
surprised by how ugly the first few attempts
may look. Just remember not to let the wind
get under the upwind wingtip.
Remember what I wrote about the
desirability of a bit of extra airspeed after
takeoff? It applies before landing too. A
sudden gust or sudden lull in wind can wreak
havoc close to the ground unless you have
good roll control. If your model maintains
good roll control authority down to as slow as
it will fly, you might not need to carry much
extra airspeed.
Want a simple but compelling challenge?
On a windy day, fly large consecutive circles
without letting the airplane drift with the wind.
Not so easy, is it? Do you find yourself
needing to tighten or loosen the turn a whole
lot to get back to where your airplane started?
If so, that is a sign that you made the right
correction—but too late. As a result, you
needed to use a great deal. The corrections to
maintain a nice, round circle have to happen a
quarter-circle earlier than you might think.
Flying into the wind slows the model’s
progress against the ground, while the rate of
turn (in degrees per second or minutes to fly
around 360°) will be the same for a given bank
angle. That means that the turn radius will be
tighter while headed upwind and looser while
going downwind. The trick is to subtly change
the bank angle early enough to get the job
done without being obvious about it.
Try removing some bank approximately
45° after the passing directly downwind and
putting that same amount of bank back in at
45° before the dead-upwind part of the circle.
Add extra bank 45° after the far-upwind end of
the circle (before the wind makes the model
cover too much ground) and take it out well
before the downwind end of the great circle.
Do this for a while, and that wind-distorted
turn to final approach will finally make sense.
Anybody can look good flying a model in
dream air, but the wind can help you look
great—and I don’t mean with the stuff that
goes back and forth in the pit area.
See you next time. Until then, have fun and do
take care of yourself. MA
August 2010 75
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