To get off the ground, your R/C airplane or helicopter needs power — whether from an electric motor, a gasoline engine, or most frequently, a glow engine. The size and type of engine will be determined by the size and type of aircraft. Helicopter engines are designed specifically for the space, weight and power requirements of R/C helicopters…airplane engines are engineered for the same criteria, applied to fixed-wing aircraft.
Choosing your aircraft engine
Many R/C planes as well as helicopters have names that contain a number. That number designates the class of engine which is required. Planes that are “40 size” use a .40-class engine, which includes those in the .40 to .53 cubic inch displacement range (for your convenience, all of Tower Hobbies’ product descriptions list the appropriate engine range in full).
Too much power is not a plus!
R/C trainer planes are usually designed for .40-class 2-stroke glow engines, and often fly best with engines from the lower end of their recommended ranges — a .40 cubic inch engine will work fine with a “40 size” trainer. The plane’s requirements might indicate that a .46 or even larger size is acceptable. But in this case, bigger is not necessarily better — the larger engines will require more throttle control from you. And you have enough other things to learn!
By contrast, seasoned pilots often gravitate toward the middle or higher end of the engine displacement ranges recommended for their “sport planes.” That’s because the added power gives their aerobatic maneuvers more oomph…and the pilots themselves have the experience to handle it.
What to consider?
2-Stroke or 4-Stroke?
Refer to our engine basic section for a comparison of these engine types. In brief, 2-strokes are cheaper and easier to operate, but 4-strokes offer better fuel economy and a more realistic sound.
Ball Bearings or Bushings?
Some aircraft engines feature crankshafts that are supported by bushings…others use ball bearings instead. If low cost is your priority, go with the bushing-equipped engine. If you’re willing to pay a little more for an engine that will run smoother and last longer, look for an engine with ball bearings.
Ringed or ABC?
An engine’s piston and cylinder assembly can have either of these types of construction.
Ringed engines use an aluminum or iron piston that moves inside an iron sleeve. The piston is surrounded by a ring that provides compression. Advantages include economy, easy starts and good power. Disadvantages? The possible need for a longer break-in period, and greater susceptibility to damage if your carburetor is not adjusted properly.
ABC engines use an aluminum piston that moves inside a chrome-plated brass sleeve. The fit of the piston and cylinder is perfected at the factory to provide excellent compression. Advantages include easy starts, shorter break-in, greater power, longer life and less susceptibility to damage from improper carburetor settings. Disadvantages? Higher price — and costlier repair, if the piston/cylinder assembly ever needs to be replaced.
What accessories will I need?
For whatever aircraft engine that you order (or is included with your model), check the “Accessories Needed” link on its towerhobbies.com product page. There, you can quickly find out what additional items are required to run it.
All glow engines will require glow fuel, fuel line, spare glow plugs and perhaps a muffler or tuned pipe. With airplane engines, you’ll also need propellers — and possibly an engine mount and spinner.
Propellers come in many different sizes and shapes. Your engine’s instructions will recommend appropriate sizes (as will the Accessories Needed link on towerhobbies.com for that particular engine). Sizes are given in two numbers (6 x 3, 10 x 6, etc.). The first number is the diameter of the prop in inches. The second number is the pitch, or twist, of the propeller. The larger the number, the greater the pitch — a prop with a pitch of 4 will move forward 4 inches during one revolution.
Spinners are the cones you see on the “nose” of model airplanes. Though they offer some aerodynamic benefits, they’re primarily cosmetic. Spinners are available in white, black, and some colors, as well as with a polished aluminum finish. Choose whatever makes your model look best!
If your airplane kit is not equipped with an engine mount, perhaps the simplest solution to mounting is a Great Planes Adjustable Engine Mount. Their design offers enough flexibility for you to get an exact fit for almost any 2- or 4-stroke glow engine. Many engine manufacturers also offer mounts that are custom-made for their engines.