Remote Control Helicopter
R/C Helicopter Terminology
- 3D (flying)
- High performance flying, usually
combining two maneuvers at once. For example, mixing a loop and a roll, to
loop while rolling etc...
- 540 Stall
- A high speed climb followed by a
540 degree Pirouette as the heli stops climbing .
- ABC / Non-Ringed
- These letters stand for aluminum,
brass and chrome or a composite such as nickel. These engines have an aluminum
piston and a chrome or composite coated brass cylinder sleeve which allows
them to be more efficient for higher performance. They have no piston ring
and rely on a very tight piston/cylinder fit to obtain a piston/cylinder seal.
New ABC engines are normally hard to turn over by hand. Because of the tight
fit, it is very important that the engine is broken in properly.
- This is really an airplane term,
but is easier to say than "cyclic roll." Ailerons are what banks a plane left
or right, but does not really exist on a helicopter.
- The shape of a wing which produces
- Angle of
- The angle between the direction
of the cord of the blades and the relative direction of the wind.
- A prefabricated model - Almost Ready
to Fly Autorotation
- A maneuver to land in the case of
engine failure; the momentum of the rotor blades can be just enough to slow
the heli down just before landing.
- An adjustment on many transmitters
that allows you to adjust the maximum throw of a servo. This is used to avoid
binding. See binding.
- Ball Link
- Connections that allow for adjusting
controls using a ball on one end, and a link that "snaps" onto the ball on
- Describes the play in the meshing
of two gears. Too much backlash and the gears could slip or break the teeth,
too little backlash could cause excess wear and tear. The common rule is the
thickness of two sheets of paper for the right am ount of backlash.
- Base Load
- A short "whip" antenna about 6 inches
long used instead of the long dangly antenna that comes with the receiver.
- Bell and
- A control system commonly used for
r/c helicopters that allow the pitch of the blades to change depending on
where they are in their rotation with the aid of paddles to take a substantial
load off the control system. Bell is the co ntrol system that involves the
swashplate and linkages to adjust the pitch and Hiller is the part that uses
a flybar or paddle to make the cyclic more responsive.
- A bad condition where the control
ajustments can not move as far as the maximum servo travel. This puts extremely
high torque on the servo constantly and can ruin a servo with time.
- Boom Strike
- A devastating event when a landing
is hard enough that the momentum of the rotor blades bends them down to the
point that one of them makes contact with the boom. This generally destroys
the blade, boom, control wire, and tail drive sy stem. This is also one of
the most common events experienced by new pilots who overreacted and pushed
the heli into the ground.
- Brain Fade
- A mental condition where the person
flying the heli, suddenly forgets which way to move the controls, or which
control to move at all. This can happen for no apparent reason, even when
you think you're comfortable at flying.
- Buddy Box
- Two similar transmitters that are
wired together with a "trainer cord." This is most useful when learning to
fly -- it's the same as having dual controls. The instructor can take control
by using the "trainer switch" on his transmitter
- CA Glue
- A form of "super glue" commonly
used in model building, don't use it on foam.
CCPM mounts the servo's pushrods directly to the swash plate at 120 degree
increments, like an equilateral triangle. With these three servo's the swash
plate can be tilted in any direction, and when they all mo ve in the same
direction the swash plate can be raised and lowered. All the mixing is done
electronically by the transmitter, which means you MUST have a ccpm compatible
- CG ("Center
- For modeling purposes, this is usually
considered -- the point at which the airplane balances fore to aft. This point
is critical in regards to how the airplane reacts in the air. A tail-heavy
plane will be very snappy but generally very unstable and susceptible to more
frequent stalls. If the airplane is nose heavy, it will tend to track better
and be less sensitive to control inputs, but, will generally drop its nose
when the throttle is reduced to idle. This makes the plane more difficult
to land since it takes more effort to hold the nose up. A nose heavy airplane
will have to come in faster to land safely.
- There are two types of "channels"
when talking about R/C. One is the channel the Tx transmits on, the other
is how many control surfaces a Tx can control.
- A weighted fuel pick-up used in
a fuel tank to assure the intake line is always in fuel
- R/C helicopters use a clutch so
that the engine can idle without the rotor blades spinning. Usually they use
clutch shoes which when spinning spread out and rub against the clutch drum
causing it to rotate and spin the gears.
- The imaginary pulling force the
helicopter applies to the blades while they're spinning.
- Describes the control which adjusts
the pitch of the rotor blades; causing the heli to ascend or descend without
the need to change the rotor RPMs. This is usually the up and down movement
of the left stick on the Tx. Having the ability to do this means you can use
the momentum of the blades when spinning to do an autorotation if the engine
dies and gives quicker response time as well.
- Describes the controls which adjust
the horizontal attitude of the helicopter, as in roll left-right and pitch
forward and backward. Both of these movements are controlled by the right
- Dead Stick
- The term is more common with R/C
airplanes (because you have enough time to say dead stick), but it's a term
that describes an emergency landing due to a power loss when the engine quits.
- Dialed In
- The term used to describe when you're
power / cyclic / tail rotor mixing is set up just right, so that when you
add power / cyclic the mixing adds / removes tail rotor thrust to maintain
the exact same heading without needing input from t he pilot. Usually, you
must spend quite some time making the mixing more or less sensitive via trial
and error, by rapidly adding and removing power / collective. All heading
hold gyro's are already "dialed in" by nature, all that needs to be done is
to adjust the sensitivity so the tail does not wag / act sluggish. All mechanical
and non hh piezo gyro's will need to be dialed in manually by tweaking the
mixing on the Tx. Heavy cyclic inputs also affect the torque on the helicopter
and must be mixed w ith the tail if that is possible on the Tx you are using.
Again, this is already taken care of with a heading hold gyro and only applies
to standard mechanical and piezo gyros.
- Describes how the advancing side
of the rotor disk is moving faster and thus produces more lift than the retreating
side. This causes the helicopter to bank in forward flight and is dampened
by flapping blades.
- The force that air pushes back onto
a moving object when resisting it's movement.
- Dual Rates
- A feature of some Tx models which
allows a person to flip a switch to make the controls more or less sensitive.
- This is another airplane term, but
is easier than saying "cyclic forward / back." The elevator is what pitches
the plane forward or back, to dive or climb, but does not really exist on
- A feature of some Tx models that
allows a person to program in different control sensitivities depending on
the position of the stick. Usually, this means the further the stick movement,
the faster the controls. This allows the middle area of the controls to be
less sensitive, but also allows full servo travel on the outer limits of the
- A feature of some Tx and Rx models
that support PCM. Failsafe is used so that the servo's go to a predefined
position if the signal is lost. In an airplane this can be to go to a low
idle while putting the plane in a gentle turn, but in a helicopter it is not
as useful since helicopters are naturally unstable there is no predefined
setting to prevent a crash.
- A rod which helps support the rotor
blades and give them more ridged strength. A flapping head has two feathering
shafts (one for each blade) and a sea-saw head has one feathering shaft (running
the span of the head)
- An abbreviation for Fast Forward
Flight. Usually in excess of 50 MPH, or near the maximum speed of the helicopter.
- Fixed Pitch
- A term that describes a helicopter
with no collective adjustments. This means that you control the height strictly
with the rpm's of the rotor blades. These are easier to maintain, stronger,
and simpler to build but lack major feature s of the collective (variable
pitch) type. For one: you can NOT do autorotations with these helicopters
and the "vertical control" is much less responsive than the collective of
a "standard" heli.
- A type of rotor head where the two
rotor blades are not connected directly through the feathering shaft (a thick
wire), each blade can move somewhat independently of the other resulting in
smoother control of the helicopter and the to some degree the feel of a .60
- The slang term which describes a
R/C heli that has a motor which runs on gasoline.
- A device used to automatically hold
the rotor RPM constant. Used in conjunction with idle-up modes. This device
is not needed, but aids when flying 3D.
- Ground Effect
- Described as an increase of performance
within 1/2 rotorspan of the ground. Which means, near the ground your blades
produce more lift.
- Ground Resonance
- This describes the phenomena that
can make a helicopter shake itself to bits on the ground, even when it is
perfectly balanced in the air. This is more common in seesaw type heads which
aren't as dampened as flapping heads, and is also more common on pavement
or hard surfaces which don't absorb vibrations.
- Usually a term associated with gyros,
it describes the sensitivity of the gyro. Too much gain causes the tail to
wag back and forth, while too little gain won't hold the tail steady.
- Glow Fuel
- The special kind of fuel R/C vehicles
typically use. It contains a good portion of nitromethane and other chemicals.
- Glow Heater
- A device you connect to the glow
plug on a engine which heats the coil element so that the fuel can ignite
and the engine can start.
- Glow Plug
- A plug that looks like a small spark
plug, but has a wire coil in it which stays hot enough once the engine is
running to ignite the next combustion cycle, and keep the motor running.
- A device used to help stabilize
the yaw of a helicopter. They come in three forms right now. Mechanical, Piezoelectric,
and Piezoelectric with heading hold. Mechanical gyros use a real spinning
disk inside a small enclosure and help resist the yaw due to the torque of
the main rotor blades by adjusting the tail rotor pitch. Piezoelectric gyros
do the same thing, but are more accurate / responsive. See Heading Hold for
the third type.
- A physical property of a spinning
object too complicated to explain, but to put it simply, is the same reason
when you're holding a spinning bicycle tire and you try to turn it, it banks
and when you try to bank the wheel, it turns. The rotor blades act the same
way, so then when you want to pitch the helicopter forward, the force that
the blades must apply would make it seem like it should bank left.
- Header Tank
- A small fuel tank connected between
the main tank and the engine. It purpose is to capture air bubbles / foam
that would otherwise be going into the carburetor. This extra fuel tank is
mostly used by 3D fliers due to the nature of the ir flights. This small tank
can also be used to see when you're about to run out of gas, if you can't
see your main fuel tank while the canopy is on.
Hold (HH) or Heading Lock
- A feature mode of some gyros that
stands out by its property to hold the heading of a helicopter and resist
the tendency to weathervane. Once trimmed, the tail needs very little input
to hold a directional heading, even in high c ross-wind conditions.
- Heli Transmitter
- A transmitter with special features
for flying helicopters, the most important of which is mixing. Most heli's
need at least 5 channels to fly. Computer Heli Remotes allow you do program
advanced and custom mixing rates for vario us flying styles. Computer remotes
also let you store multiple "models" so you can save all your programming
to memory for multiple aircraft. I use 1 model for real flight and a 2nd model
for Sim flight.
- Hot Start
- The ability for the engine to start
itself (without the glow-warmer) if you turn the start shaft after the engine
has been running a while. This is because the engine is so hot the heater
is not needed to cause ignition. This is also da ngerous because it can catch
you off guard and send your blades into a frenzy.
- The process of flying, while not
- A condition where the cylinder has
filled with fuel and can not complete a rotation. Forcing the cylinder to
rotate if you try and start the engine can ruin the connecting rod. You remedy
the situation by removing the glow plug and letting the fluid drain. This
can be caused by over-filling your gas tank which 'spills' into the muffler,
from where it has direct entrance into the cylinder.
- Idle up
- A feature on most transmitters that
will not allow the throttle to fall below a minimum setting. This is useful
because the vertical portion of the left stick simultaneously controls throttle
and collective. When flying inverted you need negative collective, you do
not want your engine to go to idle when you move your stick all the way down,
so idle-up will keep the RPMs high so you can maintain inverted flight indefinitely.
Effectively putting a "cap" on the low-end of the throttle.
- Internet Relay Chat, a real-time
chat medium that has been part of the internet before the world wide web existed.
Here you can talk to many people real-time in groups called "channels." Each
channel has a specific topic you're supposed to ta lk about, but as you can
imagine, the topic usually drifts.
- Jesus Bolt
- Most helicopters have two of these
bolts. The Jesus bolts are the bolts that hold the main mast to the frame,
and the head to the main mast. If you loose either one of these bolts your
entire rotorhead will seperate from your helicopter. They're called a "Jesus
Bolt" because when they break the pilot was known to say "Oh Jesus!"
- Too Lean
- This means that fuel to air ratio
is too low, and the engine will run hot. This can damage the engine rapidly,
so it is recommended to start adjusting the engine on the rich side and work
toward the lean end. Usually, turning a needle va lve clockwise makes the
mixture more lean.
(Red / Blue)
- A special glue for holding metal
to metal screws in their sockets so they don't come loose in a strong vibration
environment. Loctite is color coded by strength, red being the strongest and
blue being medium. Most people use blue locktite because if red is used the
screws may never come out again.
- A term that describes a function
of many transmitters that allows one control movement to affect more than
one control surface at a time. Revolution Mixing is an example of this, but
mixing can also be used to add power when you input large cyclic movements.
- As in "Fuel / Air" mixture. This
balance of fuel and air is what determines the effectiveness of the engine,
as well as how fast the engine runs. You tune the mixture with the needle
- Needle Valve
- A small dial near the carburetor
of the engine that adjusts the mixture of fuel and air into the combustion
chamber. Some carbs have two needle valves, one for high rpm and one for low.
The low RPM also controls how smooth the transi tion is from low to high.
- A term that describes hovering or
maneuvering with the nose of the helicopter pointed at the person controlling
it. This is a advanced step in the learning stages of flying a helicopter
because both roll and yaw are backwards in relation t o the controller.
- These are the shorter stubby blades
on the end of the two rods opposite the rotor blades. These aid in pitching
the main rotor blades for quicker responses and less servo stress.
- Paddle Timing
- A term to describe how far off the
rotation cycle the paddles rotation should be. There is a delay from when
the pitch is applied to a paddle and when the paddle is actually moved up
or down, it turns out that the paddle pitch must b e applied about 90 degrees
before you want the paddle to have risen or lowered. This delay is designed
to work with gyroscopic precession which is why the movement of the paddles
and blades may make it SEEM like forward cyclic would actually make the hel
icopter pitch backwards. 90 degree timing offset + 90 degree gyroscopic precession
turns the backward control into the correct movement. This is also why you
should look at the swash plate to test the servo reversing, and not look at
which way the blade s / paddles move.
- PCM / PPM
- PCM is Pulse Code Modulation which
means the signal is somewhat digital, meaning the receiver can tell the difference
between the transmitter signal and rf noise. Most PCM receivers can be set
for a "default" so that when transmission is lost you can have the controls
go to a predefined position, this is also called failsafe. PPM is strictly
FM, and is susceptible to RF noise, but not as much as AM. PPM, or FM, is
the most common because it's cheaper than PCM and the failsafe abilities of
PCM are not as useful to a helicopter as it is to an airplane, since airplanes
can somewhat fly themselves if trimmed right.
- Peak Charger
- A peak charger automatically shuts
off when your battery is fully charged. This means longer run times for your
vehicle. Peak chargers are nearly foolproof, if you forget to turn it off,
the charger does it for you. No more overcharged batteries
- A maneuver described as a high yaw
rate of a helicopter, when the tail spins around the canopy one or more times.
- Pitch Meter
- A measuring device used to check
the varying pitch settings of your rotor blades and paddles. You need the
pitch of the corresponding blades to be very close or they will not track
- The distribution of pressure over
- A method of connecting servos to
the control points with two connections, one on either end of the servo connection
/ control connection. This allows the servo to push a connection on one end
and pull the connection on the other end. Th is is used to fight slop and
use the servo power more effectively by "balancing" the pivot point.
- The direction the wind his hitting
the rotor blades taking in to consideration flapping and retreating blades.
- Every rotating or shaking thing
has a resonance freqency. When something is at it's resonance frequency, every
imbalance adds to itself at every cycle. This leads to a force which mathematically
goes to infinity and no helicopter can handle those stresses for long. Using
large training gear usually change the resonance frequance to right around
that point your helicopter likes to hover. This can result in violent shaking
even if your blades are balanced and all your mechanics are good. What you
can do is change the resonance frequency, or avoid it by changing your hover
rpm. Shorten or lengthen your training gear to easily solve this problem,
or increase your rpm a bit.
- A dangerous situation resulting
when in fast flight where the blade that is flying towards the helicopters
tail looses enough airspeed to generate lift. This can result in loosing control
of the helicopter.
- This is a mixing function on a transmitter
which lets you program a throttle to rudder mix so that as you add more power
the transmitter automatically adds more rudder to compensate for the increase
in torque. This function should be inhibited if you're using a heading hold
- Rotary Wing
- Term which describes the main rotor
blades of a helicopter.
- Describes how the airspeed over
the tips of the blades is different that that over the other parts of the
- Yet another airplane term, but not
as common as aileron and elevator. This is what controls the yaw of an airplane,
and is synonymous with the tail rotor / vertical stabilizer aka "tail fin."
- Rudder Offset
- This is a transmitter function that
lets you specify a additional amount of rudder trim for idle-up modes which
usually have a higher RPM or different blade pitch curve and thus different
amounts of torque to compensate for. This function should be inhibited if
you're using a heading hold gyro.
- Too Rich
- This means that the Fuel to Air
ratio is too high, and the engine will garble. This does not damage the engine,
but it does drastically reduce the power output. Usually, turning the needle
valve screw counter-clockwise makes the carburet or run more rich.
- Abbreviation for Receiver, the portion
of the radio system that is mounted in the helicopter and adjusts the servos
according to the transmission from the Tx.
- A form of rotor head where the two
rotor blades are "connected" through a feathering shaft (thick wire) so that
when one pitches up the other pitches down. This makes for a more stable helicopter
an a simpler design, but does not hand le as well as a flapping head type.
- A device that can turn a lever arm
one way or the other with many points between the two extremes. These adjust
all the control points of a R/C vehicle.
- A dangerous condition when descending
from a hover where the helicopter's rotor blades enter their own down-wash.
This can cause a crash if you don't recover soon enough. Note: This is not
a fatal condition on model helicopters because they have such a huge power
to weight ratio, however it can catch you off guard and it does require more
time to stop descending if you're in this state.
- Describes the imprecision of a control
system, meaning the controls can be "wiggled" without the servo's moving.
Slop can make the helicopter more unpredictable and less responsive to control
- There are two stabilizers, the horizontal
and vertical. These help the helicopter to weathervane, so that while in forward
flight, the helicopter points into the wind. 3D fliers will have smaller stabilizers
so that they can fly sidew ays / backwards faster without weathervaneing.
The vertical stabilizer also prevents the tail rotor from hitting the ground.
- This is a feature of many transmitter
models that allows you to adjust the trim of control surfaces while still
having the trim control on the Tx centered. This way you have full trim adjustment
- Swash Plate
- A device that the control arms spin
around on so that the pitch of the blades is changed depending on their relative
position to the helicopter.
- A particular subject being discussed
on a news group, or the grooves that a screw has / grooves that a screw screws
Curve / Pitch Curve / Programmable Points
- Somewhat like exponential in that
you change the way the servos move as you move the stick. Usually you would
have a different curve setting for each idle up mode. In idle up one you might
have th e throttle at 100% when the left stick is full down, at 50% when it's
in the middle, and back to 100% when the left stick is full up. This way you
can fly upside down. Some radio's have more curve points than others, which
means you could have parts of the stick less sensitive than others, so you
could make it easier to hover gracefully on a machine with a very sensitive
- A feature that comes with many transmitter
models. The opposite of Idle-Up, as in, this switch will keep the throttle
at idle so that you can increase the collective without gaining high rpms
/ power. This switch can be used as a "s afety" switch while you carry your
heli to the flight line, but is more commonly used to practice autorotations
or if tail rotor control is lost causing the heli to pirouette rapidly opposite
rotor blade direction, because when the engine is at idle, the tail rotors
loose power so the heli will slow down it's pirouettes and you can autorotate
to the ground in a more controlled manner. It is also advisable to hit this
switch in the case of an emergency so that if the heli hit something it has
no power bei ng applied to the rotor / tail blades.
- Torque is applied to the body of
the helicopter because of the engine spinning the rotor blades, this causes
the helicopter to want to spin in the opposite direction of the rotors.
- Total Aerodynamic
- The net force vector applied by
the various forces of lift.
- TR or T/R
- Short for Tail Rotor. Used to counter
the torque then engine puts on the rotor blades which left unbalanced would
make the heli spin like crazy.
- Larger landing gear so that landing
at a angle is less dangerous. Beginners use these while learning to hover
and they typically are made of two crossing sticks with whiffle balls on the
- If the pitch of both rotor blades
is not exact, one rotor blade will be slightly off axis of the other blade,
it will look like one blade is higher then the other. Viewed from the side
with blades at eye level rotor blades would look like this: >< Ideally,
you want perfect tracking, so that the blades appear to be perfectly flat
and look from the side like this: --
- When holding a heading with a helicopter
hovering level the force the tail rotor puts on the helicopter to keep it
aligned causes the entire helicopter to move the opposite direction of the
tail thrust. This is compensated wit h right-cyclic in most US helis, but
depends on the direction the rotor blades spin.
- When in forward flight, the spinning
rotor disc produces more lift than in a hover.
- When in a slow forward flight, wind
in the rear part of the disk enters at a lower angle of attack due to the
leading edge of the disk pulling air down, which results in vibrations.
- Abbreviation of the remote control
- When you're talking about a wing
or a rotorblade, washout is a twist in the blade so that part of it is at
a different angle of attack than the rest, allowing you to recover from a
stall before it's too late. The term washout mixers, levers or arms are also
used in the rc helicopter community and are referring to the mixing arms that
connect directly to the top of the swashplate and are mixed with the paddles
and main blades through a set of linkages and joints.
- The property of the helicopter to
point into the wind like a windsock. The amount of weathervaining is determined
by the size of the vertical stabilizer.
- A funnel shaped tube of fabric that
generally signifies a 10 knot wind when fully extended.
- Yaw Rate
- A term that describes the control
input of a heading hold type gyro. Instead of the rudder control adjusting
strictly the tail pitch, as it does with a other gyro, a yaw rate gyro will
uniformly control the rate at which the helicopter ya ws.
- Yaw / Pitch
- Terms that describe the change of
attitude of a helicopter. Yaw is the movement about the vertical axis; Pitch
describes leaning forward or backward; and roll describes leaning to the left
or right (bank).
A simple Z-shaped bend in the wire
end of a pushrod, which is used to attach the pushrod to a servo output arm