The RC plane, taken apart.
More than 120 years of radio, balsa and lithium, every part of a modern trainer, and benches you can drive yourself. By the SunTzu RC crew, about 15 minutes.
assembled · 9 assemblies · 79 parts
Every RC plane, from a foam trainer to a turbine jet, does the same thing: it turns the movement of your thumb into the movement of a surface a few metres away, fast enough that it feels like you're holding the plane. Understanding that chain is the difference between flying and being flown.
We'll start where it started, follow one command through a real linkage, then go part by part through what you'll actually buy.
Where it started
Scroll through the milestones. Each one links to where we checked it.
1898
Tesla steers a boat by radio
At an electrical exhibition in the new Madison Square Garden, Nikola Tesla steered a model boat across a pool without wires. He was granted US patent 613,809 that November.
1937
The Good twins fly Big Guff
In Kalamazoo, Walt and Bill Good made the first test flights of Big Guff, a radio-controlled model they built themselves. Rain kept it from an official flight at that year's Nationals.
1940
Three Nationals in a row
Big Guff won the RC event at the Nationals in 1938, 1939 and 1940. In 1938 it won on a ground demonstration after a crash, which tells you a lot about early radio.
1941
A hobby becomes the first mass-produced drone
Actor and modeller Reginald Denny's Radioplane company turned his hobby into target drones for gunnery practice. Deliveries of the OQ-2 began in June 1941 and about 15,000 were built during the war.
1945
Discovered on the drone line
An Army photographer at the Radioplane factory in Van Nuys took pictures of a young worker named Norma Jeane Dougherty, around 1944 to 1945. She became Marilyn Monroe.
1950
The engine that fit in your palm
Cox released the .049 Thimble Drome Space Bug glow engine in October 1950. Tiny glow engines put powered models within reach of almost anyone.
1950s
One channel, rudder only
Through the 1950s most RC flying used a single channel: a rubber-band escapement flicked the rudder left or right. Multi-channel reed radios, with Orbit a leading maker, arrived late in the decade.
1962
Proportional control
Doug Spreng's Digicon flew in 1962: surfaces that moved exactly as far as the stick, not just full left or full right. By the 1965 Nationals three in four entrants used proportional radios.
1967
The Kwik Fli wins
Phil Kraft won the Nationals with his Kwik Fli III and his own proportional radio. Kraft gear and low-wing pattern planes set the look of the sport for years.
1984
Radios with a memory
Computer transmitters such as the Multiplex Royal MC stored settings for several models, along with mixes and trims. Setting up a plane moved from the workbench to a menu.
2005
2.4 GHz ends the frequency board
Spektrum showed its 2.4 GHz DSM system in October 2004 and the DX6 air radio followed in late 2005. Transmitters now pick clear channels themselves, so pilots no longer had to share crystal channels.
2000s
Electric goes mainstream
Lithium polymer packs and brushless outrunner motors became the norm in the mid-2000s, and foam bind-and-fly planes followed. No fuel and no tuning: charge, bind and fly.
2013
A plane that rescues you
Horizon Hobby's AS3X (2011) steadied small planes with on-board gyros. SAFE, announced in 2013, added beginner modes and a panic button that levels the plane for you.
2024
Remote ID becomes the rule
Registered model aircraft had to broadcast Remote ID from September 16, 2023, and FAA enforcement began on March 16, 2024. Clubs with recognised fields (FRIAs) are the exception.
From thumb to elevator
Move the stick and the transmitter measures where it is. The receiver turns that into a pulse between 1000 and 2000 microseconds, sent about fifty times a second. The servo compares the pulse with its own position and drives its arm to match, at roughly 400° a second.
Then plain mechanics takes over. The servo arm pushes a pushrod, the pushrod pushes a horn on the elevator, and the elevator turns on its hinge. The bench below is that chain with real dimensions. Move across it, or tab to it and use the arrow keys.
1500 µs · servo 0° · elevator 0.0°
Drag across the bench, or use ← →
Look at the readout on Fig 2 at full stick. The servo turns 45°, but the elevator moves only 20.4°. That's because the arm hole is 12 mm from the servo's centre and the horn hole is 24 mm from the hinge: the horn is twice as long, so it turns about half as far. The trailing edge ends up moving 15.3 mm, which is what the ruler on the bench reads.
This is how you tune a plane. Move the pushrod to an arm hole further out, or a horn hole closer in, and you get more throw for aerobatics. Do the opposite and the plane gets calmer, and the servo has more leverage against the air. Your transmitter can trim throws too, but getting the mechanics close first keeps the servo's full resolution.
Every part, and what it does
A typical electric trainer, from the wingtips in. Scroll and watch the part light up on the plane.
Wing
Wing
Makes the lift. On a trainer it sits on top of the fuselage and tips up slightly at each end.
1.2 to 1.5 m span
That high wing and upward tilt, called dihedral, make the plane level itself when you let go of the sticks. It's the most forgiving layout there is.
Ailerons
Roll the plane. One goes up while the other goes down.
One servo per side
Most foam trainers put a small servo in each wing half. Older designs used one servo in the middle and torque rods out to each aileron.
Stabiliser and fin
Keep the plane pointing the way it's going, like the feathers on an arrow.
Fixed surfaces
The horizontal stabiliser steadies pitch and the vertical fin steadies yaw. The moving surfaces hinge off their back edges.
Elevator
Pitches the nose up or down. Pull back, the trailing edge rises, the tail goes down and the nose comes up.
±20° in Fig 2
The throw depends on the linkage, not just the servo. Fig 2 works it out from the arm and horn lengths.
Rudder
Yaws the nose left or right, and usually steers the nosewheel on the ground too.
Coordinated turns
A little rudder with your ailerons keeps a turn clean. Some trainers skip ailerons altogether and turn on rudder alone.
Brushless motor
Spins the propeller. On most trainers it's an outrunner: the outside case is what turns.
KV = rpm per volt
A 1000 KV motor on an 11.1 V pack spins about 11,100 rpm with nothing attached. Under load it turns slower, and on a full 12.6 V pack it turns faster.
Propeller
Turns that spin into thrust.
10 × 7
Ten inches across, and seven inches of pitch: how far one turn would screw it forward if the air were solid. Bigger props pull harder and draw more current.
Speed controller (ESC)
Turns battery power into the three-phase pulses a brushless motor needs, at whatever throttle you ask for.
Rated in amps
Choose one rated above the motor's peak draw. Most have a BEC that powers the receiver and servos, and a cutoff that eases off the motor at around 3.2 to 3.4 V per cell.
LiPo battery
Stores the energy. Light and punchy, and unforgiving if you mistreat it.
3S = 11.1 V
Each cell is 3.7 V nominal, 4.2 V full, and around 3.8 to 3.9 V for storage. Never run one below 3 V per cell. A 2200 mAh pack rated 30C can deliver 66 A.
Receiver
Listens to your transmitter on 2.4 GHz and sends each servo its pulse.
One channel per control
Throttle, aileron, elevator and rudder make four. Set the failsafe so that if the signal is lost, the throttle cuts instead of carrying on.
Servos and pushrods
Move each control surface to an exact angle and hold it there against the air.
1000 to 2000 µs
A servo reads a pulse about 50 times a second and turns to match it. Pushrods carry the motion to horns on the surfaces. Small foam trainers often use 9 g micro servos.
Balance point
The spot where the plane balances on your fingertips. Get it wrong and nothing else matters.
About ¼ to ⅓ of the chord back
The manual gives the exact spot; slide the battery to hit it. The old saying holds: a nose-heavy plane flies badly, a tail-heavy plane flies once.
Finding the balance point
Every manual marks a spot under the wing where the plane should balance. Rest it there on two fingertips: if the nose drops, it's nose heavy; if the tail drops, it's tail heavy. The battery is the heaviest thing you can move, so it's how you fix either.
The bench below is the same sum, on a lab balance. Slide the battery and watch where the beam settles.
battery 124 mm ahead · CG 30.0% · in range
Drag across the beam, or use ← →
The 185 g pack weighs about a sixth of the 1150 g airframe, so it has to sit roughly 6 times further from the mark to balance it: 124 mm ahead against the airframe's 20 mm behind. Slide it a few centimetres and you move the whole plane's balance by several millimetres.
Nose heavy is safe, tail heavy is not. A nose-heavy plane needs more up elevator and lands faster, but it flies. A tail-heavy one pitches up, stalls and can be impossible to recover, which is why the old saying ends "flies once".
Power, on the bench
Before a new motor and prop go in a plane, they go on a thrust stand. The motor sits on a lever that presses a load cell, a wattmeter sits between the battery and the speed controller, and a servo tester stands in for your throttle stick. Try it.
0% · 0 rpm · 0.0 A · 0 g
Drag across the bench, or use ← →
Half throttle doesn't mean half the thrust. From half to full, the rpm goes up about 1.9 times, the thrust about 3.5 times and the power about 6 times. Thrust grows with the square of the rpm, power with the cube.
That's why throttle management is flight time. At 32 A, a 2200 mAh pack lasts about 3 minutes. At the 5 A of half throttle it lasts closer to 21. Most trainers cruise well below half and save full power for take-off and climbs.
Then and now
A club trainer from the seventies and one you could buy this weekend do the same job. Almost everything else changed.
| Aspect | 1970s | Today |
|---|---|---|
| Airframe | Balsa kit, built over weeks and covered in heat-shrink film | Foam, out of the box in an evening |
| Power | Glow engine on methanol fuel, tuned with a needle valve | Brushless motor and a LiPo pack |
| Radio | Crystal-controlled channel, checked against the field's frequency board | 2.4 GHz that finds clear channels on its own, with telemetry |
| Help | An instructor and a buddy cord | An instructor, a buddy box and gyro modes with a panic button |
| Paperwork | Club membership | TRUST, FAA registration and Remote ID, or a FRIA |
Flying one in South Florida
Before your first flight you'll pass the FAA's free TRUST test, register anything 250 g or heavier for $5, and either fit Remote ID or fly at a recognised club field. Miami and Fort Lauderdale also sit under busy controlled airspace, which is one more reason to start at a club. The full rules, with sources.
Or let us walk you through it. We'll help pick the trainer, set it up on the bench exactly like Fig 2, and stand next to you with a buddy box for the first flight.