person to the funnel or nozzle. To guard against the  possibility of static electricity igniting fuel fumes, a  ground wire should be attached to the aircraft before  the fuel cap is removed from the tank. The refueling  nozzle should then be grounded to the aircraft be- fore refueling is begun, and should remain grounded  throughout the refueling process. The passage of fuel through a chamois increases the  charge of static electricity and the danger of sparks.  The aircraft must be properly grounded and the noz- zle, chamois filter, and funnel bonded to the aircraft.  If a can is used, it should be connected to either the  grounding post or the funnel. Cell phones should not  be used while refueling as they could pose a fire risk. Two-stroke engines require special two-stroke oil to  be mixed into the fuel before reaching the cylinder of  the engine. In some engines, an oil injection pump is  used to deliver the exact amount of oil into the intake  of the engine depending on the throttle setting. An ad- vantage of an oil injection system is pilots don’t have  to premix any oil into the fuel. However, an important  preflight check is to make sure the two-stroke oil res - ervoir is properly filled. If a two-stroke engine doesn’t have an oil injection  system, it is critical to mix oil into fuel before it is  put into the tank. Just pouring oil into the fuel tank  doesn’t give it the proper chance to mix with the gas  and makes it difficult to measure the proper amount of  oil for mixing. To mix two-stroke oil you should: Most small aircraft use a direct-cranking electric  starter system. This system consists of a source of  Many powered parachutes are equipped with a cylin- der head temperature (CHT) gauge. This instrument  indicates a direct and immediate cylinder temperature  While the oil system in a four-stroke engine and the  fuel-oil mix in a two-stroke engine is vital to the in- ternal cooling of the engine, an additional method of  cooling is necessary for the engine’s external surface.  Powered parachute engines operate with either air- cooled or liquid-cooled systems. The burning fuel within the cylinders produces in- tense heat, most of which is expelled through the ex- haust system. Much of the remaining heat, however,  must be removed, or at least dissipated, to prevent the  engine from overheating. Four-stroke engines use either a wet-sump or dry- sump oil system. Refer to Chapter 5 of the  Pilot’s  Handbook of Aeronautical Knowledge for more in- formation on four-stroke oil systems. In a four-stroke engine, the engine oil system per- forms several important functions, including: Electrical power for starting is usually supplied  by an on-board battery. When the battery switch is  turned on, electricity is supplied to the main power  bus through the battery solenoid. Both the starter and  the starter switch draw current from the main bus, but  the starter will not operate until the starting solenoid  is energized by the starter switch being turned to the  “start” position. When the starter switch is released  from the “start” position, the solenoid removes power  from the starter motor. The starter motor is protected  from being driven by the engine through a clutch in  the starter drive that allows the engine to run faster  than the starter motor. electricity, wiring, switches, and solenoids to operate  the starter and a starter motor. The starter engages the  aircraft flywheel or the gearbox, rotating the engine  at a speed that allows the engine to start and maintain  operation. Mixing Two-Stroke Oil and Fuel Oil Systems Engine Cooling Systems 4-13 • Find a clean, approved container. Pour a little  gas into it to help pre-dilute the two-stroke oil. • Pour in a known amount of two-stroke oil  into the container. Oil should be approved for  air-cooled engines at 50:1 mixing ratio (check  the engine manufacturer for proper fuel to oil  ratio for your PPC). Use a measuring cup if  necessary. Shake the oil-gas mixture around a  little to dilute the oil with gasoline. • Add gasoline until the 50:1 ratio is reached. If  you choose to use a water separating funnel,  make sure the funnel is grounded or at least in  contact with the fuel container. • Put the cap on the fuel can and shake the  gasoline and oil mixture thoroughly. • Lubrication of the engine’s moving parts. Cooling of the engine by reducing friction. • Removing heat from the cylinders. Providing a seal between the cylinder walls and  pistons. • Carrying away contaminants. Starting System