change. This instrument is calibrated in degrees Cel- sius or Fahrenheit. Proper CHT ranges can be found in the pilot’s operating handbook for that machine. 

Air cooling is accomplished by air being pulled into the engine shroud by a cooling fan. Baffles route this air over fins attached to the engine cylinders where the air absorbs the engine heat. Expulsion of the hot air takes place through one or more openings in the shroud. If cylinder head temperatures rise too much in an air cooled engine, it is because of lubrication prob- lems: cooling fan drive belt damage or wear, or air blockage in the cooling fins by a bird or insect nest. 

Liquid cooling systems pump coolant through jackets in the cylinders and head. The heated liquid is then routed to a radiator where the heat is radiated to the atmosphere. The cooled liquid is then returned to the engine. If the radiator is mounted low and close to the propeller, the propeller can constantly move air across the radiator and keep the engine cool even when the powered parachute is not moving. Radiators mounted high and away from the propeller raise the center of gravity and make it more difficult for the radiator to 

cool the engine unless the powered parachute is mov- ing. Breaking in an engine through ground runs on a hot day is when radiator placement is most critical. 

Liquid-cooled engines can overheat for a number of reasons, such as coolant not at proper levels, a leak, a failed water pump, or a blockage of the radiator. Op- erating an engine above its maximum design tempera- ture can cause a loss of power and detonation. It will also lead to serious permanent damage, such as scor- ing the cylinder walls and damaging the pistons and rings. Monitor the engine temperature instruments to avoid high operating temperature. 

Operating the engine lower than its designed tempera- ture range can cause piston seizure and scarring on the cylinder walls. This happens most often in liquid- cooled powered parachutes in cold weather where large radiators designed for summer flying may need to be partially blocked off. 

