The Rotax engine is a favorite among LSA makers for its lightweight and excellent fuel efficiency. Piper also likes the fact that the Rotax can burn either avgas or premium auto fuel with no modifications. The engine turns the propeller through a reduction gearbox so that the crankshaft spins about 2.4 times for each rotation of the propeller. The relatively small displacement of the Rotax and lightweight propeller it uses makes for smooth operation, and electronic ignition assures quick and easy starts.
The Rotax is a dry sump engine, meaning the lubricating oil is pumped out of the engine into a separate tank. If you want to check the oil before takeoff, you have to "burp" the engine by rotating the propeller by hand for several revolutions. This procedure pumps oil that was left in the engine at shutdown back into the sump, and, with the oil filler cap removed, you can hear it "burp" when the pump delivers the oil. After that, you can check the dipstick and get a true reading of the oil level.
The TBO of the Rotax 912S series engine used in the PiperSport was recently increased from 1,500 hours to 2,000 hours. There are more specific and stringent maintenance and overhaul requirements for the Rotax engine compared with conventional aircraft piston engines of similar horsepower, but fans of the Rotax point out that the excellent fuel economy, and ability to use auto fuel, can make up for some of the difference in engine maintenance costs.
The Rotax has liquid cooling for the cylinder heads but uses air flow to cool the cylinder barrels and crankcase. Rotax says that, if the cooling fluid were lost through a leak, the engine could continue to operate at reduced power without overheating, allowing plenty of time to fly to an airport. The liquid cooling keeps engine operating temperatures more stable and within a narrower range than for an air-cooled engine, so internal tolerances are tighter in the Rotax and oil consumption is low compared with the traditional air-cooled engine.
There are twin carburetors on the Rotax similar to those on many motorcycle or snowmobile engines, except in aircraft use there must be carb heat, and it's there. Fuel is pumped from the wing tanks by an engine-driven pump that is backed up with an electric standby pump. So, operation is the same as in other Pipers where you turn on the standby pump for takeoff and landing.
As on nearly all LSA, the nosewheel castors freely and brakes and rudder are used for steering. The brakes are the normal toe type on the rudder pedals. The main landing gear legs are the flat leaf type with a tubular strut for the nosewheel, so there are no oleo struts to maintain and overhaul. The PiperSport landing gear looks much sturdier to me than on most LSA, but Piper has made some changes to make it even more durable for the training environment.
The two PiperSports that were displayed at the U.S. Sport Aviation Expo in Sebring, Florida, this past January were representative of the final configuration but lacked every detail. For example, the standard BRS whole-airplane recovery parachute was not installed. The airplanes had three-blade, ground adjustable fixed-pitch props that are probably standard, but it was not certain. And work on increasing the stick-force gradient in pitch had not yet been completed on the airplanes.
To get a feel for what the PiperSport flies like, Piper's longtime do-everything pilot Bart Jones talked me through a preflight and cockpit check. Inside the cockpit there are standard four-point harnesses to fasten, and the rudder pedals move to suit pilots of various sizes because the seat position is fixed. The cockpit is roomy, with plenty of space to rest inboard elbows on a center console that hides a storage compartment.
The few times I have flown Rotax-powered airplanes, I have always been impressed by how easily the engine starts — just turn the key — and by its smoothness. It buzzes, or hums, instead of the loping idle that is common to conventional direct-drive aircraft piston engines. Vibration is low, and throttle response is good. But again, there is a difference. Most Rotax engines have a very strong spring that pulls the throttle to full open as a safety feature in case the operating mechanism fails, so the throttle must be locked to remain in any intermediate position. Many airplanes use vernier-style push-pull throttles with the center locking button to keep the throttle where you want it. The PiperSport has a throttle lever with triggers just below the knob. You hook your fingers on the triggers and lift up to move the lever, and then release to lock it in place. It is intuitive to use and reminds me of the idle cutoff lockouts that are common on many business jet throttles. The friction locks are positive enough to keep the throttle lever from creeping forward but do not have enough resistance to prevent the pilot from moving the lever if the friction lock system somehow fails.
