SportFlying.aero

Engines in sport aircraft can be two-stroke, four-stroke, or whatever. They just have to conform to the limits and other good-sense requirements. One of the requirements is that the engine is a reciprocating engine. Gas turbine engines are not allowed.

There is no horsepower limit for the engine but the basic lightweight design of the plane will result in it using an engine of about 100 horsepower or less. Some of the engines in sport planes are ones that were originally developed for homebuilts and ultralights, such as the Rotax line. Others are new downsized engines produced by manufacturers such as Lycoming and Continental, who also make engines for larger aircraft. One of the advantages of buying a finished aircraft rather than building your own is that the engine decision has already been made for you, though you might have an option or two.

Maximum speeds, too, are critical to the definition of LSAs. That's because sport aircraft are designed to be simple and safe. Increasing the maximum airspeed of an aircraft can greatly complicate an otherwise simple plane. The FAA limits are reasonable. Your craft must be rated by the manufacturer for no more than a "maximum continuous power" or VH. It's not the airplane's highest speed (called VNE or never-exceed speed), but the maximum speed in level flight. For LSAs that number is 120 knots or 138 mph.

Flying Words

Which should you use: knots or mph? Most regulations and manufacturers present speeds in knots or nautical miles per hour. If you become a commercial pilot you will use knots almost exclusively. However, many sport and recreational pilots prefer mph or miles per hour because that's what they use when driving. Use whichever you wish—as long as you identify whether it is knots or mph. ATC (air traffic control) uses only knots so you must remember to use that measurement during radio communications. To convert knots into mph, simply multiply knots by 1.15. To convert mph into knots, multiply mph by .87.

Stall speed is important, too, because that's the speed at which the aircraft lands. The stall speed needs to be 45 knots (51 mph) or lower. Without flaps it can be 51 knots (59 mph) or lower. The point is that these simple aircraft should have low landing speeds to make them easier and safer to land.