Fly with Two Receivers

Sep 18, 2013 6 Comments by

For most high performance 3D aerobatic airplanes, pilots will often split the control system into two separate onboard radio setups to add redundancy and to lessen the demand on the single receiver battery. Usually, they will split the controls left and right. One receiver takes care of the right aileron, rudder servo and elevator servos. The other system takes care of the left side of the plane.

Another reason for using two receivers is for scale pilots and it involves placing one receiver in the wing and another in the fuselage. The wing receiver takes care of the ailerons and has its own battery pack, switch harness and charging jack. I did this with my giant triplane because, I wanted to eliminate the long aileron servo leads often seen taped or tied to a scale model’s cabane struts!

Here’s how I did it.

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(Above) My fuselage receiver is located under the pilot seat and accessible through the cockpit opening.

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(Above) There’s a lot of distance between the fuselage receiver and the aileron servos. A second wing installed receiver makes the airplane easy to setup at the field.

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(Above) While building and covering the top wing, I made a main hatch cover and opening to get to the Aileron receiver system. Here you see the ProTek RC 330T servos (from A-Main Hobbies) used for the ailerons.

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(Above) Like any scale airplane, the aileron servos are installed in their own removable hatch covers.

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(Above) This is the finished Aileron servo hatch. You need to make sure you can easily guide the servo extension wires through the wing to the wing receiver in the center of the wing panel.

 

Begin by making sure your radio gear is compatible with multi-receiver binding. With my Spektrum DX18 transmitter, I was able to use a 9-channel receiver  (AR9020) in the fuselage and an a second Spektrum AR7010 7-channel receiver in the wing.

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(Above) Spektrum AR9020 DSMX 9-channel receiver is my main “fuselage” receiver.

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(Above) The Spektrum AR7010 DSMX is used in the wing to control the ailerons.

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(Above) I used  A123 6.6V LiFE packs from NoBS Batteries for both radio systems, but the aileron servos draw much less from the battery pack than do the fuselage servos since I am running 6 servos in the fuselage. The same switch harnesses were used for both, and available from Hangtimes Hobbies.

The main thing to remember is that your receivers have to be the same type to bind at the same time to a single transmitter. For me, that means you have to use two DSM2 or DSMX receivers and they both have to be set for the same MS for the servos being used. (typically 11MS).

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(Above) Here is a top view of the wing while I am working out the placement of the aileron receiver system.

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The Spektrum secondary antenna receiver is also installed in the top wing with the correct orientation to the receiver. Also, make sure it is located away from any metal parts like the cabane strut attachment points. You may need to make a hatch cover for these aux. antenna receivers if you can not reach them from the main receiver hatch.

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(Above) Here’s the wing hatch in place with switch/charge jack installed. The small black dot shows the ground wire position for the charging lead orientation.

 

So, install the bind plug in your first receiver (the fuselage) and then bind to the transmitter. Once bound remove the plug and switch off the first receiver. I also switch off the transmitter. Now installed the bind plug in the second receiver and bind it to the transmitter. Remove the plug and power down the receiver and the transmitter. Now you are set. I always turn on the transmitter and then the receiver in the fuselage, then the wing receiver. Wait several seconds before turning on the second receiver to make sure the first had successfully bound to the transmitter.

I know this also works with Futaba 10CAG transmitters and receivers but you should check with other brands of radio.

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(Above) My fuselage receiver switch (and smoke pump power switch) are located in the cockpit opening.

 

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(Above) No ugly aileron extension wires between the fuselage and wing to connect or come loose. That’s the idea!

 

That’s it. According to the tech guys at Specktrum, there is no limit to the number of receivers you can bind and operate with a single transmitter, but you do have to consider how far to go. When does the redundancy deliver diminishing returns? Like with a twin engine airplane, there are two chances for an engine out. So too with multiple receivers. you now have twice as many switches, batteries, and connectors to fail. You also have to remember to switch on two radios and charge two battery packs between flights.

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(Above) Here I am switching on the wing receiver system. Remember to switch both receiver systems on before each flight. Also, for extra safety, I recommend a Range Check with the engine running at the beginning of each day of flying.

 

It’s up to you. Should you have radio issues, do not continue to use a questionable setup. I did have one receiver loose a substantial amount of range during my range check so I did not fly. I replaced the receiver and the plane now has about 2 dozen glitch free flights in the log book.

Have fun!

 

Quick Specs

Radio:                   Spektrum DX18 w/9 ch receiver

Aux Receiver:    Spektrum AR7010 7 ch.

Batteries:            NoBS A123 2300mAh w/switch x2

Servos:                 Protek 330T x6

Servo Arms

Hangar 9 Aluminum Rudder

Hangar 9 Aluminum Elevator x2

 

Gerry Yarrish, Scale

About the author

Senior Technical Editor About Me: I have a lifelong passion for all things scale, and I love to design, build and fly scale RC airplanes. With 20 plus years as part of the Air Age family of magazines, I love producing Model Airplane News and Electric Flight.

6 Responses to “Fly with Two Receivers”

  1. Steve says:

    Are those wheels from Arizona Aircrafters?
    Thanks Steve D

  2. William J. Krummel, Jr. says:

    It is not really a redundant system. If you lose one receiver, you lose control over the functions that it controls. A truly redundant system would have a receiver controlling all of the aircraft functions and a backup receiver that will do the same thing in case of a primary receiver failure. I believe this is a requirement for large scale aircraft flown in Europe. Does anyone know where a system such as this can be purchased?

    • Gerry Yarrish says:

      Right Bill, I did not say it was a redundant system, I made the setup to eliminate the long aileron lead wires between the wing and the fuselage.

  3. Bill says:

    Kümmel: Power Box Systems has redundant systems. Duraliteflightsystems.com sellS, them.

  4. Craig says:

    I am looking at doing this for my 1/4 SE5a. One receiver would control Ailerons and one Elevator. The second receiver would control Rudder, the other Elevator and the Throttle. Redundancy is my motivation.

    Good article, thanks.

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