Ground School
The following section
is mainly designed for those who have little or no knowledge of aerodynamics,
and/or are totally new to the hobby. Even experienced pilots will benefit
from this, as there are some differences between models and full scale.
Please read it thoroughly.
First, if you are
just starting out: There are benefits to getting an ARF (Almost Ready to
Fly) as opposed to kits. Generally speaking, by the time you buy a kit,
the hardware and the covering, you have spent as much as the ARF. And it
will take you at lest twice as long to put the kit together. You will also
need the appropriate tools to install the covering. So too with an "Almost
Ready to Cover" plane. And if you do destroy an ARF, you won't have the
time investment loss. The advantage to the kit is you know how well it
is constructed, and the covering will probably be better quality material.
Keep in mind that covering the aircraft alone is an art in itself, and
will probably take 10 to 15 hours. Build kits in the fall and winter; ARFs
in the spring and summer.
Second, if you are
just staring out: Don't load up your Visa/Mastercard with all kinds of
equipment, flight boxes etc. Get some fuel and get to the field. After
you've worked with an instructor, and met some fellow pilots, then decide
what equipment you want. There is a lot to choose from. And there is a
lot of good used equipment available through the club or swap meets. All
too often, new hobbyists overspend, don't learn as quickly as they had
hoped, and get discouraged. This is especially true if they tear up their
first airplane. Keep your investment small until you gain some momentum.
Third, now that you've
stared: Unless you're sure of yourself, don't be too quick to buy that
"second" plane. Chances are you may be buying a second "first" plane. Take
your time. On the other hand, you may surprise yourself and be able to
jump directly to a "third" or "fourth" plane. Get some flight time in after
you've soled and you'll have a better idea.
We will not get into
any discussions of model kit building, or radio systems at this time. Together
they could have their own entire manual.
Granted, one doesn't
have to know how to fly the space shuttle to fly a model aircraft. However,
a general understanding of basic aerodynamics will help to understand why
it does what it does. Our objective here is to provide you with the concept
of aerodynamics, not the technicalities. For those who wish to go into
aerodynamics at greater depth, student or private pilot flight manuals
are a good place to start.
Note: Referring to
aircraft as to right or left, is as a pilot would view it from the cockpit.
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Wings:
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There are three basic
wing profiles.
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Flat Bottom:
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Creates the most lift
and is the most stable. Most trainers are flat bottom.
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Semi-Symmetrical:
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Still stable, yet allows
more maneuverability and extends aerobatic capability. Great for "second"
planes.
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Fully Symmetrical:
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Least stable and most
aerobatic. For more experienced flyers only. There are three basic wing
locations.
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High-Wing, Mid-Wing,
Low-Wing:
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Stability diminishes
as the wing comes down; the high wing being the most stable. Here too,
most trainers are high wing. A fully symmetrical, mid-wing with no dihedral
is the most aerobatic.
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Dihedral:
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Dihedral is the angle
in the wing when looking at it from front or rear. The more dihedral, the
more stable and self recovering. The straighter, the more aerobatic but
less stable. A low-wing aircraft requires more dihedral to be as stable
as a high-wing, all other factors being equal.
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Washout:
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Washout is a twisting
of the wing when viewed from the wing tip. The trailing edge is higher
at the wing tip than at the fuselage. This increases stability and self
recovery. It allows the outer wing area to still "fly" (maintain control)
even if the inner wing area is in a stall condition. Refer to "stalls"
later. Washin is reverse, and has no practical application.
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Ailerons:
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Ailerons control the
bank of the aircraft which turns the aircraft. Refer to "lift" later. The
up aileron decreases "lift", while the down aileron creates more "lift",
thereby banking the aircraft. The aircraft always banks or turns toward
the up aileron.
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Vertical Stabilizer:
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The stationary part
of the rudder assembly.
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Rudder:
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The movable control
surface of the assembly. Its primary function is to coordinate the bank
and turn. However, in the case of model aircraft, it can be used to steer
or turn the craft.
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Horizontal Stabilizer:
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The stationary part
of the elevator assembly.
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Elevator:
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The movable control
surface of the assembly. Its primary function is to control the angle (nose
up, etc) of the aircraft. However, in the case of model aircraft, it is
basically used to control altitude. Technically, power controls altitude
and elevator controls angle, which in turn controls airspeed. Refer to
more advanced flight manuals.
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Flaps:
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Flaps create more "lift".
There are several basic types of flaps, none of which are used on trainer
planes. Refer to more technical manuals.
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Lift:
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Lift is created when
the air moving over the top of the wing moves faster that the air underneath.
Air over the top must travel a greater distance, therefore it must move
faster to get to the rear at the same time. The faster the air moves past
a surface, the less pressure it exerts on that surface. The pressure underneath
is greater pushing the wing up. This is lift. Lift is always 90 degrees
to the relative wind. Lift is always 90 degrees to the span of the wing.
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Relative Wind:
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RW is the air coming
at the aircraft; it is always exactly opposite the direction of travel.
Do not confuse this with the wind conditions you are flying in. The angle
of the wing as it hits the RW is called the angle of attack. Too high of
an angle of attack, without enough airspeed, will cause the wing to stall.
Refer to "stalls "later.
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Components of lift:
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When the aircraft is
banked, the "lift" is banked too. The "vertical component of lift" is no
longer as great. This is why you have to add up elevator to maintain altitude.
The "horizontal component of lift' causes the aircraft to turn. If you
bank too steep, the "vertical component" will lessen even more and the
wing will stall and fall. Refer to "stalls" later.
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Propellers:
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A propeller is nothing
more than a rotating airfoil in the horizontal direction. Applying more
power creates more horizontal lift (better known as thrust) which pulls
the aircraft through the air. Do not think of a propeller as blowing air
rearward.
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P-Factor:
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For the sake of simplicity
we will only say that P-factor is the unequal thrust or torque of the propeller.
During power on, or climbing conditions, the right side of the propeller
produces more thrust. This causes the aircraft to drift left. This is why
an aircraft that rolls straight, will run off to the left of the runway
on take-off. Correct with a slight right rudder.
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Stalls:
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A stall is the loss
of "lift". This condition occurs when the angle of attack becomes too great
for the air to flow smoothly over the top surface. The air then becomes
turbulent (much like the spoiler on a race car) and no longer produces
lift. When this happen, the nose of the aircraft will drop abruptly resulting
in the loss of altitude. Stalls can occur with power on, or power off,
at low speed or high speed, depending on various other conditions. The
most common are while climbing too steeply and turning after take-off,
or when banking too steeply while turning final to land. All stalls have
one thing in common. They all require lowering the nose to recover. Point
of interest: A spin is nothing more than a sustained stall with rotation.
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Flight Pattern:
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The FP, or traffic pattern,
is made up of four legs. Starting at the runway, the first 90 degree turn
is the crosswind leg. The second 90 degree turn becomes the downwind leg
which is parallel to the runway. The third turn is the base leg which is
90 degrees to the runway again. The forth turn becomes the final leg towards
the runway. Henceforth the term: "Turning final". Proper departure for
the pattern is to turn only 45 degrees not depart straight out the crosswind
leg. Proper approach and entry is to head in on a 45 degree angle towards
the downwind leg. Aim for the end of the runway where you plan to set down.
Turn downwind when you are at an appropriate distance away from the runway.
Do not enter the pattern straight in on the downwind as you may encounter
departing aircraft.
There are those who
believe that flying a model aircraft is more difficult than a full scale.
Visualizing yourself from the aircraft view takes some practice. It's like
an out of cockpit experience. Everything is fine so long as you are coming
towards yourself, is a whole different story. Think of it as sitting backwards
on the dashboard of your car steering wheel between your legs, and driving
down the road. Here's a reference list to help you along.
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Aircraft Direction
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Control Movement
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Aircraft Reaction
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Aircraft Going Away
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Aileron
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Same
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Elevator
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Same
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Rudder
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Same
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Coming Towards You
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Aileron
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Reversed
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Elevator
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Same
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Rudder
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Reversed
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Inverted Going Away
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Aileron
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Same
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Elevator
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Reversed
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Rudder
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Reversed
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Inverted Coming Towards You
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Aileron
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Reversed
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Elevator
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Reversed
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Rudder
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Same
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