The RC helicopter, taken apart.
Fifty years of learning to hover, every part of a modern 450, and benches you can drive yourself: the swashplate, the tail and the hover. By the SunTzu RC crew, about 15 minutes.
assembled · 10 assemblies · 102 parts
A helicopter has no wing to lean on. Its wing is the rotor, and it only works while it spins: around 45 turns a second on a 450, with each blade changing its angle as it goes round. Flying one means steering that spinning disc, and stopping the body from spinning with it.
We'll start with the people who first got one off the ground, follow your stick through the swashplate, go part by part through a modern 450, and finish with the two things every helicopter pilot learns early: why it needs a tail, and where the hover is.
Where it started
Scroll through the milestones. Each one links to where we checked it.
c. 1931
A balsa model starts the story
Guinness World Records lists Arthur M. Young's balsa and rubber-band model, built around 1931, as the first RC helicopter. His later models flew on electrical remote control, and his big idea was a stabilizer bar that kept the rotor steady enough to hover.
1969
A 5.5-second flight wins a prize
A German industrialist offered $2,800 in prizes to the first pilot who could fly a model helicopter by radio. Dieter Schlüter won it in 1969 with a flight of 5.5 seconds.
1970
David Gray flies one in Cincinnati
At the 1970 RC show in Cincinnati, David Gray flew his .40-powered RC helicopter, which then made the cover of Model Airplane News. The AMA credits him with the first RC helicopter flight, and the Smithsonian holds his model.
1971
The first kits go on sale
Schlüter was the first to make and sell an RC helicopter kit: a semi-scale Bell Huey Cobra with a fibreglass body and machined mechanics. Horace Hagen got one of the first 50 in April 1971, the first RC helicopter kit in the US.
1978
Collective pitch arrives in kits
Schlüter's Heli-Boy was a bolt-together kit with a .60 glow engine that weighed 8.5 pounds. It had collective pitch, which changes the angle of both main blades at once, plus tail-rotor mixing.
1985
The first world championships
The FAI gave RC helicopters world-championship status in 1983. The first F3C championships were held in London, Ontario, in July 1985, and Japan's Shigetada Taya won the individual title.
1989
A helicopter built for newcomers
Kyosho asked world champion Shigetada Taya to design the Concept 30: easy to maintain, tough in a crash and friendly to fly. It came as the DX trainer and the SE for aerobatics.
2000
Piezo gyros replace spinning wheels
Early tail gyros used spinning wheels that ate battery power. By 2000, Model Aviation was describing piezo gyros with no moving parts that sense yaw and correct the tail servo about ten times faster.
2001
Work starts on the electronic flybar
Ulrich Röhr started VBar in 2001 as a private project to replace the mechanical flybar with electronics, and Mikado has built and sold it ever since. Mikado calls it the first flybarless system with a built-in tail gyro.
c. 2004
The T-Rex 450 makes small electrics popular
Writing in 2007, Model Aviation said Align's T-Rex 450 had arrived about three years earlier and quickly became the small helicopter everyone wanted, on an electric outrunner and a 3S 11.1 V LiPo.
2007
Coaxial helicopters for beginners
E-flite's Blade CX came assembled, with two main rotors spinning in opposite directions to cancel torque, mostly for indoor flying. Model Aviation's 2007 review said almost any experienced RC pilot could fly one safely.
2013
Freestyle 3D gets its own world title
F3N, the FAI's freestyle class for RC helicopters, became an official class in 2010, and its first world championships were held in Germany in 2013.
From stick to swashplate
A helicopter's two sticks do two very different things. The collective stick adds pitch to both blades at once, so the whole disc lifts more. The cyclic stick tilts the disc, and the helicopter goes the way the disc leans. Both reach the blades through one part, the swashplate: raise it for collective, tilt it for cyclic.
Its bottom ring sits on three servos and doesn't turn. Its top ring turns with the head and pushes a link up to each blade's grip. Raise the plate and both links rise together. Tilt it, and each link rides up one side and down the other as the head goes round. Move across the bench below, or tab to it and use the arrow keys.
Collective pitch 0.0 degrees. Swashplate tilted 0.0 degrees forward. Each blade's pitch swings between 0.0 and 0.0 degrees as it goes round.
collective 0.0° · plate level · blades 0.0° to 0.0°
Move across the bench: up and down is collective, left and right is cyclic. Or use the arrow keys.
At full collective both blades on Fig 2 reach about +10°. At full cyclic the plate tilts 7° and each blade swings from −8° to +8° and back once per turn: more bite on one side of the disc, less on the other, so the disc tilts. Real setups are close: the Blade 450 3D's manual sets ±10° or ±12° of collective, and 3D pilots run 10 to 12° of cyclic.
Your radio does the mixing. No one servo is "elevator" or "pitch". The transmitter, or the flybarless unit, works out how far each of the three must move for every combination of sticks. That's what CCPM means, and it's why a helicopter is set up on the bench before it ever flies.
Every part, and what it does
A typical electric 450, from the blade tips in. Scroll and watch the part light up on the helicopter.
Main blades
Main blades
Make all of the lift. Two blades of about 325 mm on a 450.
About 720 mm across
The Blade 450 3D's rotor is 721 mm across and the Align 450LP's 734 mm. The blades are symmetrical and flat on both faces: their pitch, not their shape, decides how much they lift.
Rotor head
Holds the blades in grips that turn on a spindle, so each blade can twist to change its pitch.
2,300 to 2,800 rpm
That's the T-Rex 450's range across its flight modes, about 40 to 47 turns a second. Spinning blades carry a lot of energy: stand well back.
Swashplate
Turns your stick movements into blade pitch. Raise it for collective, tilt it for cyclic.
120° CCPM
Its bottom ring sits on three servos and doesn't turn; its top ring turns with the head. Fig 2 is this part on a bench.
Cyclic servos
Three servos, 120° apart, that hold the swashplate's bottom ring between them.
Three, plus one for the tail
No one servo is elevator or pitch. The radio or the flybarless unit mixes your sticks so all three move together for every command: that's CCPM.
Flybarless unit
A three-axis gyro that steadies the head and holds the tail.
Swash servos up to 200 Hz
Your sticks ask for a rate of rotation and the unit makes the helicopter match it, like fly-by-wire. The Microbeast drives its swashplate servos at up to 200 Hz and its tail servo at up to 560 Hz.
Motor and main gear
A brushless outrunner whose small pinion drives the big main gear on the rotor shaft.
11:1
On the Align 450L a 121-tooth main gear meets an 11-tooth pinion, so the motor turns eleven times for each turn of the rotor.
Speed controller
Feeds the motor from the battery and, on a helicopter, holds the headspeed steady.
Rated in amps
A helicopter flies at a set headspeed. In governor mode the speed controller adds power as the collective loads the rotor, so the rpm doesn't sag in a climb.
LiPo battery
A 3S pack for a 450: 11.1 V nominal, 2200 mAh on the Blade 450 3D.
About 6 minutes
The Blade 450 manual sets the transmitter's timer to 6 minutes, 5 for hard flying and up to 8 if you only hover. Land with charge to spare.
Canopy
The painted shell over the nose. It keeps wind and grass off the electronics.
Two grommets
It pops onto two posts on the frame, so it comes off in a second for a battery swap. Bright colours help you read which way the helicopter is facing.
Tail boom and drive
Carries the tail rotor about half a metre back and drives it from the main gear.
4.07 turns per rotor turn
On the Align 450L a 106-tooth gear drives a 26-tooth tail gear, so the tail always turns in step with the main rotor, about four times as fast.
Tail rotor
Pushes sideways to stop the body spinning against the main rotor's torque.
Pitch sets the push
Its speed is tied to the main rotor, so the tail changes its push by changing pitch. Even with the stick centred its blades sit at some positive pitch: Fig 3 shows why.
Tail servo
Sets the tail blades' pitch through a long pushrod down the boom.
270 Hz and up
The gyro corrects the tail constantly, so the tail servo has to be fast. The Microbeast manual asks for one that handles at least 270 Hz.
Landing skids
Two tubes on a plastic gear that the helicopter sits and lands on.
A wide stance
The width keeps it from tipping on touchdown. For first hovers many pilots bolt on training gear: crossed sticks with balls on the ends.
Why it needs a tail
The motor turns the rotor one way, and the rotor turns the body the other way. Left alone, the helicopter would spin under its own blades. The tail rotor stops it by pushing sideways at the end of the boom, and a coaxial helicopter does it with a second rotor turning the other way.
The bench below sets a 450's body on a turntable with a spring, so the torque shows up as a twist. Drag across it to change the tail rotor's pitch, and find where the pointer reads zero.
tail pitch 8.0° · push 206 g · holds its heading
Drag across the bench to set the tail pitch, or use ← →
At about 8° of tail pitch the tail pushes 2.0 N, and the torque and the push cancel. That's why a helicopter's tail blades sit at some positive pitch even with the stick centred.
That balance moves all the time. Add collective and the main rotor needs more torque; take it away and it needs less. So the flybarless unit's heading-hold gyro senses the yaw and trims the tail pitch for you. The Microbeast talks to its tail servo up to 560 times a second, which is why a good tail servo is fast.
Finding the hover
On a helicopter the headspeed stays put and the collective does what the throttle does on a plane. More pitch, more lift. Strap a 450 to a bench scale and you can watch the rotor take the weight off it.
pitch +0.0° · lift 0 g · scale 762 g · sits on the scale
Drag across the bench to set the collective, or use ← →
The 762 g helicopter reads less and less as the pitch comes in, and at about +6° the scale reads zero: the rotor is carrying all of it. That's about where a T-Rex 450 hovers. A little more and it climbs, a little less and it settles.
Hover is a balance, not a setting. Wind, a fresh or a tired battery and the thin air of a hot Florida afternoon all move it. That's why first lessons are all hovering: small, constant corrections, one control at a time.
Then and now
A club helicopter from around 1980 and a 450 you could buy this weekend. The physics is the same; almost everything else changed.
| Aspect | Around 1980 | Today |
|---|---|---|
| Power | A .60 glow engine; electric flight was still an experiment | A brushless motor and a LiPo pack, 3S on a 450 up to 12S on a 700 |
| Stabilisation | A flybar with paddles, and a tail gyro with a spinning wheel | A three-axis flybarless unit with a heading-hold tail |
| Radio | 72 MHz, one frequency pin per channel at the field | 2.4 GHz spread spectrum, no pins |
| Head | Collective by a wire in a grooved shaft, or none at all | 120° CCPM on three servos; the sticks ask for rates of rotation |
| Learning | Hovering on a tether, and a lot of crashes | A simulator first, then self-levelling and panic-recovery modes |
From Model Aviation's helicopter columns (1978 to 2014), the flybarless explainer and today's manuals.
Flying one in South Florida
A 450 weighs about 762 g, well over the FAA's 250 g line, so the rules are the same as for a plane: pass the free TRUST test, register for $5, and fly with Remote ID or at a recognised club field. The full rules, with sources.
Then start in a simulator. Every crash there is free, and Model Aviation's helicopter guide recommends one too. When you're ready for the real thing, we'll set it up on the bench like Fig 2 and stand next to you for the first hovers.