There are several ignition cutoff systems on the market today. These cutoff devices are valuable since they provide both safety and convenience for gas powered aircraft. For this how-to article I used an ignition cutoff device provided by Smart-Fly to show how they are installed, how to operate them and the benefits of such a device.

The extra safety that electronic cutoff devices provide are as follows:

• If the transmitter is OFF but the ignition is switched ON the cutoff device will prevent the engine from starting by accident.
  
  
• Safety while in the air - Should the receiver lose power from a dead battery, bad switch or broken wire the plane would normally go to the last throttle position. With this device it will kill the motor in such an event.
  
  
• If the throttle servo or linkage fails you can kill the motor to bring the aircraft down instead of flying around until the tank is empty which could be hazardous in a large, powerful aerobatic plane

This particular cutoff device consists of two modules that are connected by a fiber optic cable. The fiber optic cable ensures that there is no electrical connection between your ignition and the radio system which could cause interference.

Modules, Fiber Optic Cable, Instruction Leaflet	Transmitter Module Close-up	Receiver Module Close-up

This particular unit has an added benefit. It actually recognizes and works with dual receiver systems that are quite common to large gas powered aircraft today. If your primary receiver loses power, the 2nd receiver can still control the cutoff so you don't lose power. This way you aren't forced to land dead stick if one RX is still working.

On the technical side the modules work like this: The transmitter module sends light via the fiber optic cable to the receiving unit. When the transmitter is sending the signal the receiver turns on its electronic power switch allowing the ignition unit to receive power from the ignition battery. When the transmitter is off, it turns the power off to the ignition.

INSTALLATION OF THE SMART-FLY IGNITION CUTOFF DEVICE

Installing the device is a very simple and fast process. For this article I decided to install it into my Wildhare 35% Giles. The first step is to plug the transmitter module's deans connector into the auxiliary channel of your radio. This is the channel where you will switch the ignition on and off. The channel you select will vary depending on your particular radio and setup. It is best to put it on a switch that is easily accessible BUT not one that is likely to be accidentally switched thus causing a deadstick! The transmitter module is marked for receiver one and receiver two. If using only one receiver just tie up the 2nd lead with a twist tie to keep things neat and plug ONLY the receiver 1 lead into your RX

Next loosen up the ferrule (fiber optic connector) and insert the fiber cable into the hole. It should go in about 5/8" then tighten the ferrule. This will keep the fiber optic cable secure. Mount the unit using either Velcro or some foam as I did in this installation to protect from vibration.

Modules, Fiber Optic Cable, Instruction Leaflet	Transmitter Module Close-up	Receiver Module Close-up

Next the cutoff receiver module is installed. The receiver unit should be mounted near the ignition unit. It must go between the ignition on/off switch and the ignition module. Don't put it between the battery and the switch because the receiver module will always be on and drain your battery. The lead marked battery goes to the ignition switch side and the lead marked ignition goes to the ignition itself. Next, you must route the fiber optic cable from the transmitter module to the receiver module. Although the cable can be cut with a sharp knife to customize its length, I just coiled up the excess in case the system was ever used in another plane which required additional length. Once the cable is run you secure it to the fiber optic connector the same as was done with the transmitter. Last, mount the module with some foam or Velcro to protect from vibration.

The last thing to do on this installation is install the optional red LED onto the fuselage. For this I drilled a 1/4" hole per the instructions. I removed the deans connector from the LED assembly and slipped the wires through the hole. The housing just pushes in snug into the hole. You can see the completed installation below.

To test the system turn your radio and ignition switches on. Flip the switch on your transmitter that you assigned and look at the transmitter module which will show a lit green LED when "hot" (see pic below). If you installed the optional LED as I did you will see the red LED light up as well. I've tested this in sunlight and you can see the LED fine. This is a great visual indicator so you know when the ignition is hot.

If you are using a single PCM receiver with this particular device you should set your transmitter failsafe to cut the engine. Since my Giles uses a single receiver I setup my JR 10X to kill the ignition in the event it goes into failsafe mode for any reason.

That is all there is to it. The installation took me about 25 minutes total including taking all these pictures for the article. If your looking for some extra safety, peace of mind and a visual indicator to know when your ignition is armed consider installing a cutoff device in your gasoline powered aircraft. I know I'll be flying with a lot more peace of mind this season!

For information on the Smart-Fly cutoff device used in this article visit www.smart-fly.com

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Quest Engineering & Development
1328 East Cottonwood Lane
Phoenix, AZ 85048
(480) 460-2652
website: www.smart-fly.com
email: info@smart-fly.com