Part of the Fuel-Powered RC Airplanes Center
Smoke is one of those additions that can make a big aerobatic airplane easier to see and a lot more fun to watch. It can also coat the inside of the airplane with greasy fluid—or create a fire hazard—if the tank, pump, tubing, wiring, or injector is poorly installed. I want a smoke system to deliver only the fluid the exhaust can vaporize, with every part mounted and tested as carefully as the engine’s fuel system.
This guide belongs to the Fuel-Powered RC Airplanes Center.
How an RC Smoke System Works
A separate tank holds smoke fluid. An electric pump sends that fluid through heat-resistant tubing to an injector in the muffler or exhaust header. The hot exhaust vaporizes the fluid and produces the visible smoke trail. Smoke output depends on exhaust temperature, injection location, fluid flow, and the type of smoke fluid.
A standard muffler may not retain enough heat or provide a suitable injection point. Use components intended for the engine and exhaust system rather than drilling a muffler at a guessed location.
Main Components
- Smoke-fluid tank with a secure stopper, pickup, and vent arrangement
- Fuel- or smoke-compatible tubing and fittings
- Electric smoke pump sized for the engine and exhaust
- Injector fitting installed at the manufacturer’s recommended location
- Battery or regulated power source suitable for the pump
- Radio channel, switch, and mixing when proportional operation is desired
Tank and Plumbing
Mount the smoke tank close to the airplane’s center of gravity when practical so the model’s balance changes as little as possible. Secure it against vibration and protect the lines from heat, sharp edges, and moving linkages. Clearly distinguish smoke plumbing from engine-fuel plumbing during installation and maintenance.
The pickup needs to remain submerged during normal maneuvers. The vent must let air replace the fluid being pumped without allowing fluid to siphon into the airplane. Follow the pump and tank manufacturer’s plumbing diagram.
Pump and Radio Setup
The simplest arrangement uses an on/off transmitter switch. A proportional channel or throttle-to-pump mix can reduce fluid at low throttle and increase it as exhaust heat rises. Start conservatively. Too much fluid can cool the exhaust, reduce smoke quality, leak from joints, or collect inside the airplane.
Program a positive off position and confirm that failsafe leaves the pump off. Keep pump wiring and connectors secure, and verify that the chosen power source can handle the load without affecting receiver voltage.
Ground Testing
Do not make the first full-flow test in the air. Work through the system on the ground and make one change at a time:
- Test the pump with the engine off and the outlet routed into a container so direction and flow can be confirmed.
- Inspect every fitting and line for leaks.
- Run the engine outdoors with the airplane securely restrained.
- Turn smoke on briefly at a throttle setting recommended by the system manufacturer.
- Increase flow only until the system produces reliable smoke without excessive raw fluid.
- Reinspect the airframe, exhaust, and plumbing after the system cools.
Safety and Cleanup
Treat the smoke system like a second fuel system. Smoke fluid, exhaust, and mufflers can cause burns, fire, breathing irritation, and slippery residue. Keep fluid away from brakes, tires, covering seams, radio equipment, and hot components unless the system instructions specifically permit the installation. After every test, look inside the airplane as well as underneath it; a clean exterior does not prove that a loose fitting is not filling the fuselage with fluid. Do not operate smoke where field rules, fire conditions, spectators, or local restrictions make it inappropriate.