RC Helicopter
Flight Basics for mSR and 120SR

Space Considerations

The small Blade mSR is small and nimble enough for flying inside an average house and it will bounce off things it hits leaving both of them unharmed. The same can't be said for the 120SR. Because of its larger size and greater speed there isn't room in an average home to do more than hover and putter slowly around. When the 120SR hits something it's more rigid rotor blades will often break and cause damage to what they hit. On both models a bent tail rotor or flybar will affect handing in ways a beginner will not recognize and will make it difficult to trim for hover, so when first attempting to fly and trim the model its best to find a large open space either indoors or outdoors on a calm evening.

Transmitters: RTF vs. Spektrum Transmitter (Tx)

Ready to Fly (RTF) models come equipped with a transmitter. Bind-n-Fly (BNF) models require the use a compatible RTF transmitter from another model or a Spektrum transmitter purchased separately. The Spektrum Tx provides better control, more adjustment options and the ability to store multiple models in non-volatile memory. I use a DX6i.

New models require binding with the transmitter. The model is powered on first, and the status indicator LED will blink once then after a delay of a few seconds start pulsing rapidly. The Tx is then powered on with the "BIND" switch or button engaged until the indicator on the model goes out again. After a few seconds the he status indicator LED on the model will glow continuously indicating a "bound" state. This binding set-up need only be performed once.

During binding the model stores the unique ID code of the transmitter in its memory. After binding the transmitter, not the model must be turned on first so the receiver in the model can find it when the battery is attached and power the receiver. When ending a flying session the battery should be detached from the model before turning off the transmitter.

Trimming for Hover

Blade models are advertised as "flight tested" but that doesn't mean they will jump out of the box into a perfect hover the first time they are flown. Both will jump to the left on take off (a trait of all helicopters due to the tail thrust) then pendulum (a trait of the 45 flybar Bell-Hiller rotor design) then settle down and either hover in one spot or drift off. Until that sequence happens you can't see how its trimmed and correct for hover, and that takes some space to accomplish without crashing into things.

What defines hover trim isn't the angle of the shaft, swashplate, or that the rotor is level to the horizon, its the ability of those things in combination to keep the model over one spot without control input. Helicopters are inherently unstable so the fact the Blade mSR and 120SR can hover hands off is not the norm, and expecting them to remain in one place for more than a few seconds is unrealistic. So once up in the air for the first time adjust the throttle to maintain a hover then let go of the sticks and observe. More than likely it will start to slowly drift sideways and forward or backwards with the nose/tail spinning around slowly. Correct for and drifting in this order:

Body of helicopter is spinning: The tail is aligned with the tail motor with on the mSR is driven by a separate electric motor adjusted via the trim switch on the transmitter console under the left stick, or via the sub-trim menu for rudder of a Spektum transmitter.

Helicopter is drifting sideways: Sideway movement of a helicopter is controlled by moving the right (cyclic) stick sideways and banking (rolling) the rotor in the same direction. Correcting a sideways drift (crabbing) requires trimming the "aileron" servo is required to neutralize the position of the swashplate, flybar and rotor blades. The servo can be trimmed to ways: 1) moving the servo off center with the transmitter trims, or, 2) leaving the trims centered and adjusting the length of the servo link. For a beginner it is easier to first trim with the transmitter switches, then after gaining some experience flying re-center the transmitter switches, pop the links off the servo arm and turn the head clockwise to shorten and counter-clockwise to lengthen one turn at a time until the sideways drifting is eliminated.

Helicopter is drifting forward or backwards: Forward/reverse movement of a helicopter is controlled by moving the right (cyclic) stick forward / backwards and banking (pitching) the rotor in the same direction. As with the aileron you will eventually want to center the trims and adjust the links, but initially its quicker, easier and less complicated to just click the console trim under the right stick or enter a value for aileron under the sub-trim menu of a Spektrum.

Throttle curve (Spektrum Tx)

Spektrum transmitters allow adjustment of throttle stick response. That is necessary on collective pitch CP models to coordinate movement of the left stick with simultaneous changes in collective pitch and throttle: as pitch is increased throttle must also increase to compensate. Inverted flight with CP models requires V shaped throttle curve with the throttle turning the rotor at "idle" speed when the rotor is at 0 pitch on the ground but increasing throttle when the collective pitch is either increased above 0 (normal flying) or decreased below 0 (inverted flying).

Because the mSR and 120SR are fixed pitch models (i.e. no collective pitch adjustment) they only really need one throttle curve with three characteristics: 1) lift off cleanly into hover; 2) fly level, and; 3) ascent / descend gradually from level flight/ hover.

I set my throttle curve so when the left stick is centered all my different models hover. That makes its easy for my thumb to find hover power, move above it to take off or ascend, and move below it to descend. Since most flying is done around hover having the stick centered also makes moving the stick sideways to control the tail more easier and more predictable.

I keep the center part of the throttle curve used for level flight flatter than the default linear 45 curve so when I'm moving the rudder around any inadvertent change in throttle will not cause the model to bob and weave like a drunken sailor.

Leaving the "Throttle Hold" parameter of the throttle curve set-up equal to 0% allows the throttle hold switch on the back / right of the Tx. Keep the switch UP (cutting power) when handling the model on the ground as a safety measure, and flip it up in any crash to cut power to the rotors to minimize damage to the rotor or from overloading the ESC motor controller on the board with a stuck motor.

Exponential and Dual Rates

Once hovering a Blade mSR or 120SR doesn't go anywhere unless the pilot moves the cyclic (right stick). Conventional wisdom for beginners the Spektrum Tx use lower than 100% dual rates and large about Exponential (Expo) to tame performance and make the sticks less sensitive around center. But with those "training wheels" hobbling performance the helicopter can become so slow to respond the beginner will be to over correct with gross stick movements instead of learning how to control them with finessed.

On the fixed-pitch Blade models throttle controls thrust. In hover main rotor thrust push the air straight down with 100% of the power vertical and 0% horizontal. As cyclic input tilts the rotor blade the forward vector increases and the vertical vector decreases by the same amount so it is necessary to increase when throttle when tilting the rotor - in any direction - to keep the helicopter from descending.

When tilted beyond a 45 angle the rotor will have difficulty generating enough vertical lift to keep the helicopter flying level no matter how much throttle is applied. The combination of extreme tilt and a reduction of throttle on a fixed-pitch model will send it towards the ground like a rock.

I recommend having a large unobstructed space to fly in the first few times and using no expo or very small amounts. Without any EXPO the relationship of stick movement to helicopter movement is quicker and more predictable that when the sticks are dumbed down. Then from that zero baseline a beginner can increase EXPO as needed to find their personal comfort level.

Lifting Off / Landing Checklists

This is my procedure for lifting off:

1) Turn on Tx - wait 2 sec.
2) Flip "Throttle Hold" switch UP (for safety) and lower throttle stick to min.
3) Plug in model and let it bind to Tx.
4) Move cyclic to confirm binding and servos are operating OK
5) Flip "Throttle Hold" switch DOWN
6) Raise throttle slowly to stabilize rotors until light on skids.
7) Increase throttle briskly to 60-70% of travel.
8) When model gets to desired elevation move throttle to center.
9) Let model stabilize in mid-air.

After landing:

1) Flip "Throttle Hold" switch UP (for safety).
2) Unplug model - remove battery

Finally in the Air! Now What Will Happen?

Due to the hybrid Hiller-Bell design of the controls on Blade FP models there is a slight lag in the response of the heli after the stick on the Tx is moved because the servo first moves the flybar which is acting like a gyro (the "Bell" part. But once tilted by swashplate link the wing shape of the flybar tips "flies" it onto a new plane. It is the movement of the flybar which then cyclic feathering pitch of the rotor, decreasing it on one side and increasing it on the other creating unbalanced lift causing the rotor to tilt. But as the rotor tilts flybar stays level, which changes the feathering pitch of the rotor blades back to equal IF the pilot continues to hold the cyclic stick forward.

The need to hold the cyclic stick to sustain the tilt of the rotor the biggest difference in how flying the Blade FP differs from a collective pitch (CP) helicopter; real or model. On a CP helicopter to initiate forward flight you would push the stick forward, but then pull it back to center when the desired tilt is achieved. On the Blade FP models if the stick is pulled back, the design of the flybar causes the rotor to revert to level automatically. So in that sense the sustained cyclic input needed to keep the rotor tilted in any direction is more akin to an overriding of its tendency to automatically revert to a hover state.

Flying skills:

Helis don't handle well when moving slow and descending steeply from hover because that causes them to fly into their own downward rotor wash and turbulence. That's why puttering around in a small room with the 120SR really will not reveal how it flies very well.

Moving forward puts the rotor into "clean" air undisturbed by the rotor wash. If you fly at moderate forward speed, in control, and ease off the cyclic slowly to stop there will be no pendulum swing. With more forward speed outdoors or in a large gym it will result in better more predictable handling and allow more realistic scale flying, such as sweeping banked turns created mostly with aileron input vs. spinning it around by the tail with the rudder.

Don't get in the habit of just releasing the cyclic and letting the model center itself. That's what triggers the pendulum effect. When the stick is released it will initially change the rotor feathering to +/- on opposite sides and stop forward motion, but then because the gyro effect caused the flybar stays level it will cause the rotor to go into a cycle -/+, +/- changes as the mass of the body and tail rock back and forth until lift, gravity and directional momentum come to equilibrium again in a hover state.

The combined effect of the pendulum action and using a lot of EXPO the response lag and pendulum will cause a beginner to move the stick too much to begin with then over-correct, which becomes a vicious cycle resulting in loss of control and a crash. That's why I suggest dialing back the expo and learning to moderate the stick movement from day one.

When you need to stop forward motion to prevent hitting something learn to use the pendulum to advantage to change direction. When the nose swings up for the first time on releasing forward elevator use the rudder to swing the tail around 180 CW (right rudder stick, then push the elevator forward and add throttle. That will cause the model to stop and change directions, flying back towards the open space avoiding the crash instead of bobbing out of control. With practice you'll learn to initiate the stop and initial rise of the nose with reverse elevator for even quicker turns. It's the best crash avoidance maneuver you can learn and practice.

Practice landing on a large low table

A good way to practice controlled forward flight is landing on a coffee table with a 45- 30 glide slope. It trains the reflexes to coordinate elevator (keeping the rotor angle constant) and the throttle (keeping lift just below hover power) as you fly it -- slowly -- into the ground.

The advantage of using a large table vs. the floor as a landing area is being better able to see the cause and effect of "ground effect". That's the additional lift created at low altitude by the rotor wash bouncing off the ground. On the floor its so uniform you won't notice it much, but on landing on a table you notice a distinct increase in lift as you cross the edge of the table when landing. On small table the area is so small the ground effect will be less predictable and more difficult to learn to compensate for. The model will have a tendency to spin around on landing because the mass of the body is so light relative to the kinetic energy still turning the rotor, and if the table is small it will wind up on the floor after an otherwise successful landing.

With a slow steep a decent on landing you will find you'll go from wallowing in the downwash to being buffeted up by the ground effect. But if you practice and learn to approach the landing on a 45-30 glide slope and then pull back on the elevator a bit just before contact with the ground you are able to avoid the downwash and fly through the initial transitional effect of the ground effect as the edge of the table is crossed, but then use the ground effect cushion to "flare" the rotor back and settle the heli gently onto the table.

When you can land smoothly you'll have better reflexes and control when flying in the air level or ascending. It doesn't take much space to practice slow controlled landings and they will greatly improve your hand-eye-control-model response coordination better than just zooming around the room and banging into things...

RC Helicopters
Climbing Up The Learning Curve

This tutorial is copyrighted by © Charles E. Gardner.
It may be reproduced for personal use, and referenced by link, but please to not copy and post it to your site.

You can contact me at: Chuck Gardner

For other tutorials see the Tutorial Table of Contents