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  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. 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. 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. 4-14