Pre-Flight Checks for RC Helicopters

There is an old saying in aviation that a good flight begins before the aircraft ever leaves the ground. That is every bit as true with an RC helicopter.

RC helicopters are impressive machines, but they are also complicated. The rotor head, tail system, drive train, electronics, battery, servos, and flybarless system all have to work together. Unlike many fixed-wing models, a helicopter has very little tolerance for something coming loose or moving in the wrong direction once the rotor is turning.

A few minutes spent checking your helicopter before a flight can prevent a damaged model—or something much more serious.

Start With a Good Visual Inspection

Before connecting the flight battery, give the entire helicopter a good look.

Don’t just glance at it and think, It was fine the last time I flew it.

Look for anything that seems different.

Check for loose screws, missing hardware, cracked plastic, bent parts, damaged wiring, or anything that appears to have moved since the previous flight. Pay particular attention if the helicopter has been transported in a vehicle, stored for a while, or worked on since its last flight.

Sometimes the problem you catch during a pre-flight inspection isn’t something that failed during the last flight. It is something that loosened while the helicopter was bouncing around on the trip to the field.

Check the Main Rotor Blades

The main rotor blades deserve special attention because of the tremendous forces they experience when the helicopter reaches operating speed.

Inspect both blades for cracks, chips, dents, or other damage. Look closely around the blade roots and mounting holes.

Make sure the blade bolts are secure and that both blades have approximately the same amount of resistance when moved in the grips. They shouldn’t flop around freely, but they shouldn’t be clamped so tightly that they cannot straighten themselves as the rotor comes up to speed.

If you find damage that makes you question whether a blade is safe, replace it.

A rotor blade is not the place for the old “It’ll probably be okay for one more flight” philosophy.

Inspect the Rotor Head and Linkages

Next, work your way through the rotor head.

Check the blade grips, pitch links, ball links, swashplate, main shaft, and associated hardware. Make sure the links are fully seated on their ball ends and nothing feels excessively loose.

Gently move the controls by hand and watch the mechanical parts move. Everything should move smoothly without binding.

If a ball link suddenly feels much looser than it normally does, don’t ignore it. A link that separates in flight can result in an immediate loss of control.

Also check for excessive play in the rotor head. Some movement may be normal depending on the helicopter’s design, but anything noticeably different from previous flights deserves investigation.

Don’t Forget the Tail

The tail rotor may be smaller than the main rotor, but it is just as important to maintaining control of the helicopter.

Inspect the tail blades for cracks, chips, or other damage. Check the blade grips and ensure the tail pitch mechanism moves smoothly through its full range.

Look at the tail control rod and its guides. Make sure nothing is bent, disconnected, or binding.

Depending on the helicopter, also inspect the tail belt or torque tube system.

A belt should have the proper tension and should not show signs of excessive wear. On a torque-tube helicopter, inspect the gears and drive system whenever possible.

Losing tail control during flight can turn a normal flight into a very interesting few seconds—and not the good kind of interesting.

Check the Main Gear and Drive System

Take a close look at the main gear.

Look for damaged or missing teeth and make sure the gear meshes correctly with the motor pinion. Check the motor mount and surrounding hardware for anything that may have loosened.

Rotate the rotor system slowly by hand with the helicopter powered off.

You should feel smooth movement throughout the rotation. Grinding, clicking, binding, or an unusual tight spot is a reason to stop and investigate.

A strange noise on the ground rarely gets better once you put several thousand RPM behind it.

Battery and Electrical Connections

Before installing or connecting the flight battery, inspect it carefully.

Look for swelling, damaged wiring, loose connectors, or other physical damage. Make sure the battery is fully charged and compatible with the helicopter.

Once installed, make sure the battery is securely restrained.

Helicopters vibrate, maneuver aggressively, and can generate considerable forces. A battery sliding around inside the model can change the helicopter’s balance or damage wiring and connectors.

Inspect the ESC, receiver, servos, and visible wiring as well.

Pay particular attention to wires running near gears, shafts, or other moving components. A wire that has shifted slightly may eventually rub against a rotating part and wear through its insulation.

Check the Transmitter Before Powering Up

Before connecting the helicopter’s battery, take a moment to look at the transmitter.

Make sure you have the correct model selected.

Modern radios may hold dozens—or even hundreds—of model memories. Selecting the wrong model can give you incorrect servo directions, throttle settings, flight modes, or other programming.

Verify that throttle hold is engaged before powering the helicopter.

Check your flight-mode switches, rates, timers, and any other switches that affect the helicopter.

This only takes a few seconds, and it can prevent a very unpleasant surprise.

Verify Every Control Direction

Once the helicopter is powered and initialized, check the controls before attempting to spool up.

Move the cyclic controls and watch the swashplate.

When you command forward cyclic, the swashplate should move to pitch the helicopter forward. Pull back, and it should command the opposite.

Move the stick left and right, and confirm the helicopter responds in the correct direction.

Check collective pitch as well.

Increasing collective should increase the blade pitch in the direction needed to produce lift. Decreasing collective should reduce it appropriately.

Finally, check the tail rotor.

Move the rudder stick and make sure the tail pitch mechanism moves in the direction required to produce the commanded yaw.

Don’t simply check that something moves.

Make sure it moves in the correct direction.

Check the Flybarless System

Modern flybarless systems add another extremely important pre-flight check.

After the system has initialized, leave the transmitter controls centered and gently tilt the helicopter by hand.

The swashplate should respond by attempting to oppose the movement.

For example, if you tilt the helicopter to the right, the flybarless system should command a correction that pushes the helicopter back toward level flight.

Do the same thing forward, backward, left, and right.

Then gently rotate the helicopter’s nose and verify that the tail gyro responds in the direction necessary to oppose that rotation.

This check is especially important after changing programming, replacing electronics, performing repairs, or setting up a new helicopter.

A reversed stabilization direction may not be apparent when the helicopter is on the ground.

It will become extremely obvious when the helicopter tries to leave the ground.

Unfortunately, by then you may have very little time to do anything about it.

Something Changed? Check It Again

Any time something changes on the helicopter, treat the next flight with extra caution.

That includes replacing blades, adjusting linkages, changing a servo, updating flybarless settings, replacing the receiver, working on the tail system, or repairing the helicopter after a hard landing.

A hard landing deserves more than a quick look.

Something can bend without being immediately obvious. A link can partially pop off. A main shaft or feathering shaft can develop a slight bend that produces vibration when the rotor reaches speed.

Even if the helicopter hasn’t crashed, give it a more thorough inspection if it has been sitting unused for an extended period.

The fact that it flew perfectly six months ago doesn’t guarantee everything is perfect today.

Before You Spool Up

Now take one last look around.

Make sure the area around the helicopter is clear.

Spectators should be safely behind the flight line and well away from the rotor disk. Make sure no one is walking toward the helicopter or standing somewhere they shouldn’t be.

Check that tools, battery leads, blade holders, towels, or other loose objects have not been left near the model.

Position yourself properly, confirm throttle hold, and make sure you’re mentally ready before beginning the startup sequence.

There is no prize for being the fastest pilot at the field to get airborne.

Pay Attention During Spool-Up

Your pre-flight inspection doesn’t end when the rotor starts turning.

Watch and listen as the helicopter comes up to speed.

Look for unusual vibration, excessive wobbling, poor blade tracking, or movement that doesn’t look normal.

Listen for clicking, grinding, rattling, or other unfamiliar sounds.

If something doesn’t look or sound right, shut it down.

Don’t keep increasing the rotor speed hoping the problem will disappear.

Once the helicopter reaches a stable operating speed, consider making the first few seconds of the flight a simple low hover, particularly after maintenance or adjustments.

Make sure everything feels normal before transitioning into more aggressive flying.

The 30-Second Check That Can Save a Helicopter

Experienced pilots sometimes face a particular danger that beginners don’t yet face: familiarity.

You’ve flown the helicopter fifty times.

Maybe a hundred times.

You know the model. You know the radio. Everything worked perfectly yesterday.

That’s exactly when it becomes easy to skip the pre-flight check.

But screws don’t care how experienced you are. Ball links don’t know how many flights you’ve made. Batteries don’t care that they worked perfectly last weekend.

Develop a routine and use it every time.

Blades. Head. Links. Tail. Drive system. Battery. Radio. Controls. Flybarless correction. Flying area.

It doesn’t have to take long.

Thirty seconds of careful checking may prevent hours of rebuilding.

More importantly, it helps protect you, the other pilots at the field, and everyone who comes out to enjoy the hobby.

A successful RC helicopter flight shouldn’t begin when you spool up.

It should begin with the pre-flight inspection.

Happy flying, York RC Club.