Building up an RC plane from scratch is almost as fun as flying it. That’s why many of us love to build our own models or tinker with them. As with any good DIY project, some issues might pop up once in a while. Is your RC plane going backward?. It’s incredibly frustrating when that happens, but it’s generally easy to fix.
Your RC plane could be going backwards because you have the wrong propeller for your motor rotation. In some rare cases, even your battery polarity can cause the backward flight. Setting these things right should solve the problem if you do it right.
There are quite a few reasons for this problem. That’s why it’s crucial to identify the issue accurately. If your problem is the motor, you can fix it without much hassle. If it’s something else, you would probably need to replace the part. I’ll now explain how to pinpoint the cause of your problem and how you can deal with them.
Why is Your RC Plane Going Backwards?
People design planes for going forward, so they don’t have the necessary components to go in reverse. That makes it extremely annoying when your plane starts pushing itself backward. That’s because it won’t fly as much as it would drag itself a few feet back. It would then spin because of the wind resistance on its back wings.
If your plane is flying backward, first check what kind of machine you have. There can be quite a few combinations between props and engine.
- Check the engine: If you are using a gas engine and your plane is going backwards, you have the wrong props installed. A gas engine RC plane won’t fly that way for any other reason than that. Gas engines are straightforward.
That’s why you can’t usually change the rotational direction. In cases like these, your best bet is getting a different propeller setup.
If you have an electric motor and your plane is flying backward, the motor is spinning the wrong way.
Electric motors can rotate in both directions with the help of electronic speed controllers. If you don’t want to tinker with the ESC setup, you can slap on a different propeller. That alone should fix the problem.
But ESC’s are easy to edit, and it would be far cheaper to reverse the rotation of your motor.
- Did you drain your battery: Manufactured planes usually have chargeable batteries. The problem with batteries like this is that they become gimmicky when you bleed them dry too much. If you see that your motor’s spinning in the right direction in conjunction with your propeller, then your problem probably lies in the battery.
If you drain a battery out too much and leave it like that, it might change its polarity the next time you charge it back. That will cause the motor to receive the wrong charge and spin in the opposite direction. It makes your plane do the exact opposite of what you want it to do.
The battery polarity is probably the most annoying problem of them all. It doesn’t just make your plane fly backward, it reverses every control on your plane. It affects things like the wing flap movements and any other function you have that requires a motor.
- Did you get the right propellers: I see many newbies who pick any old propeller from the shop. But propellers are crucial for RC planes. You can usually tell if it’s responsible for your plane going backward fairly easily.
Press the throttle and move your hand in front of the props. If your plane has a propeller at the front, you should feel the air being sucked in by the props towards the plane. If the air flows toward your hands, then you have the wrong propellers.
Alternatively, if your plane has props at the back, they should push the air out toward the end of the plane.
I want you to check your plane thoroughly and compare the issues I just explained. Once you figure out what issue your plane has, it will be easier for you to follow through with the fixing options.
Troubleshooting Your RC Plane
If you can identify the cause of your RC plane malfunctioning the fixing it shouldn’t be that hard if you have even the basic idea on RC plane mechanics. Here are some troubleshooting methods that you can apply.
Reversing The Motor Rotation
If you checked your plane and found a brushless electric motor, follow the instructions I’m about to give you, and your plane should start flying right in no time.
- ESC setup- single direction: If you are struggling with your plane perpetually going backward, you probably do not have a multi-rotor or a bi-directional ESC setup. What you have is likely to be a Single directional ESC. Electronic speed control supplies power to your motor, thereby controlling the speed at which you move.
Most modern RC planes have brushless motors. These are essentially three-phase motors.
That means there are three electro-magnets inside the motor that surround the permanent magnet in the middle. The electronic speed controller connects to these three electromagnets separately.
It then sends power to each of these electro-magnets one by one in clockwise or counterclockwise order in a set frequency. That frequency determines how fast the motor spins.
When one electromagnet receives electricity and starts producing its magnetic field, the rotor with the permanent magnet spins in its direction. Once it reaches that point, ESC powers up another adjacent magnet and the rotor follows. Repeating this process causes the rotor to continuously spin, and that’s how your propeller moves.
I assume you connected the three wires from the ESC with the motor but you didn’t check if the rotation direction was correct for your prop setup.
It’s easy to change the direction on brushless motors with an ESC. You only need to switch two of the three wires connecting your motor to the ESC. They can be any two wires while you leave one alone. I always keep the middle wire connected and switch the outer two wires.
- Multirotor ESC- bidirectional: Bidirectional ESC’s are set up in a way that you can make the motor spin in both directions. This is more commonly seen in Water Rc planes such as Mini mags. Water Planes have bidirectional systems even though they can’t fly properly backward.
The reasoning behind that is to let the planes steer backward on water. These planes land on lakes and other water bodies, so they might be hard to retrieve in certain cases. Having a reverse motor allows it to back paddle from tricky situations.
If your plane is a water Rc plane, and it’s flying backwards when you move the controller forward, you have two options. One is to get used to moving the controller backward for moving your plane forward (genius right?), this saves you a lot of hassle, but you probably won’t like it.
The second option is Reprogramming your ESC. You need to get a multi-rotor ESC and connect it to the motor. Then you got to flash it on a computer to get the correct settings.
Fixing The Battery Polarity
You are more likely to face the reversed polarity problem on battery-run RC, usually on the old mass-produced planes.
They usually run on two motors on both wings instead of a single front rotator. You probably don’t want to mess around too much with the design of this sort of plane. so the edits need to be as small as possible
These planes usually run on two motors, so you don’t have to check the motor rotations on both of them if you know that the battery changed polarity. Merely switching the wires connecting your motor to the power source should fix your issue.
This sort of design is ancient, and you are not likely to find them on high-end RC planes anymore.
If you don’t have anything to attach the wires directly to the motor, you can also cut them in the middle. Then connect them appropriately by adding extra wires in the middle. Try to use thin wires to prevent extra weight.
Setting Up The Right Propeller
I saved propellers for last because you can bypass this step if you can fix motor direction. But if you can’t change the motor direction or that step fails, then you can take a look at this step. In truth, changing your propeller is probably easier than changing motor rotation direction.
As you might already know, there are two ways a propeller works. It can either push the air or pull the air inward. There are two different setups that RC planes use.
One is called a tractor configuration and the other is called a push configuration. How you need to solve your plane from going backward, depends on which of these configurations you have.
- Tractor Configuration: Planes that have a single front propeller are called Tractor configuration. Meaning, if your motor spins counter-clockwise these propellers pull the air from the front and push it out the back. That effect drags your plane forward.
Most RC planes use this setup because of its simplicity. It also helps keep your engine cool because the air flows right into the engine compartment.
It’s aerodynamically more suited for RC projects. Now that you know how it works, it’ll be easier for you to understand why your plane goes backwards.
You probably don’t have the right propeller for your setup if your plane is going backwards. Your motor is spinning in a way that’s making your propeller push the air out, instead of sucking it in. It could either be because your motor is moving the wrong way, or you have a pusher propeller on the front.
Unfortunately, you can’t fix the propeller by flipping it. Pusher propellers are designed differently than tractor propellers. You can’t even make it work if you reverse your motor rotation from counterclockwise to clockwise. You have to get a proper tractor propeller for your plane.
Try to get one that fits the size of your motor. All propellers are marked with two sets of numbers. The first one is the diameter and the second one is the pitch. Pitch determines how far the plane goes per revolution of the propeller.
If you have a strong motor you can get larger diameters. If your motor is big enough you can get the larger ones.
- Pusher configuration: Pusher is a setup that you would commonly see at the back of the plane. Instead of climbing by pulling the air in, they push themselves forward.
So what happens if your motor spins in a direction that pulls the air with your propeller? Your plane will start shooting backwards. The same thing will happen if you have a tractor propeller at the back.
Fixing it is the same as the previous one. You gotta get a proper pusher propeller for your motor.
Here comes a tricky part, most pusher configurations use two motors at the back. They need to rotate in alternate directions. Even if you have two pusher propellers, if they both rotate clockwise or both counterclockwise, your plane will start spinning.
Pay attention to the spin direction when you set your pusher propellers. One of them needs to spin counterclockwise, and the other needs to spin clockwise to keep the balance of your plane.
You need to take care of the motor speed too. Sync them both in a way that they have the same number of revolutions per minute.
If your motors are not in sync, your plane will be unbalanced even if you have the right propellers and rotating directions. They will tend to veer towards the side with the faster motor.
I don’t find the double motor pusher setup particularly appealing. It’s harder to maintain and set up. It requires a better cooling system for the engine because the air gets pushed out the back. You would usually end up needing a vent system on your wings. Without good filtering, your engine will overheat.
As you can see, fixing your RC plane going backwards is not tough at all. You merely need to identify what’s causing the issue and fix it. Most of the time, you won’t even need to deal with propeller setups and design.
Reversing the motor rotation usually fixes the problem 90% of the time.
Hopefully, now you have a proper understanding on fixing the problem of RC plane going backwards.