Some of the advantages of fuel injection are: Disadvantages include: The ignition system provides the spark that ignites the  fuel-air mixture in the cylinders. Components include  a magneto generator, an electronic control box that  replaces mechanical points, spark plugs, high-voltage  leads and the ignition switch(es). Individual manu- facturer designs will vary and pilots must be familiar  with the aircraft operating procedures for the PPC be- ing flown. Most modern PPCs use an electronic timing system  instead of the mechanical points inside the old magne- tos which also housed the points. Capacitor discharge  ignition (CDI) systems are a common example of an  electronic ignition system. Electronic ignition sys- tems operate without any moving parts to increase  reliability and efficiency. A CDI system begins to fire  when the starter is engaged and the crankshaft begins  to turn. It continues to operate whenever the crank- shaft is rotating. Most powered parachutes incorporate a dual ignition  system with two individual coil systems in the mag- neto, two individual electronic ignition timing sys- tems (electric box), two separate sets of wires, and  Detonation is an uncontrolled, explosive ignition of  the fuel-air mixture within the cylinder’s combustion  chamber. It causes excessive temperatures and pres- sures which, if not corrected, can quickly lead to fail- ure of the piston, cylinder, or valves. In less severe  During normal combustion, the fuel-air mixture burns  in a very controlled and predictable manner. Although  the process occurs in a fraction of a second, the mix- ture actually begins to burn at the point where it is  ignited by the spark plugs, then burns away from the  plugs until it is consumed completely. This type of  combustion causes a smooth buildup of temperature  and pressure and ensures that the expanding gases de- liver the maximum force to the piston at exactly the  right time in the power stroke. You can identify a malfunctioning ignition system  during the pretakeoff check by observing the decrease  in RPM that occurs when you first turn off one igni - tion switch, turn it back on, and then turn off the other.  A noticeable decrease in engine RPM is normal dur- ing this check. If the engine stops running when you  switch to one ignition system or if the RPM drop ex- ceeds the allowable limit, do not fly the powered para - chute until the problem is corrected. The cause could  be fouled plugs, broken or shorted wires between the  magneto and the plugs, or improperly timed firing of  the plugs because of the control box.  A magneto uses a permanent magnet to generate an  electrical current independent of the aircraft’s elec- trical system which might include a battery. The air- craft electrical system can fail—the battery can go  dead—however, this has no effect on the ignition sys- tem which uses a separate generator in the magneto.  The electricity from the separate ignition coil on the  magneto generator goes into the ignition control box  where the correct voltage is produced and timed to  fire the spark plugs at the proper time. The magneto  also sends a signal to the electric control box to pro- vide the timing signal to fire the spark plugs. It should be noted that “no drop” in RPM is not nor- mal, and in that instance, the powered parachute  should not be flown. Following engine shutdown,  keep the ignition switches in the OFF position. Even  with the battery and master switches OFF, the engine  can fire and turn over if you leave an ignition switch  ON and the propeller is moved because the ignition  system requires no outside source of electrical power.  The potential for serious injury in this situation is ob- vious.  The operation of the ignition system is controlled in  the cockpit by the ignition switch(es). Since there are  two individual ignition systems, there are normally  two separate ignition toggle switches. two spark plugs per cylinder. Dual ignition systems  increase overall reliability of the engine. Each igni- tion system operates independently to fire one of the  two spark plugs. If one ignition system fails, the other  is unaffected. The engine will continue to operate nor- mally, although you can expect a slight decrease in  engine power. Combustion Ignition System 4-9 • No carburetor icing. Better fuel flow. • Faster throttle response. Precise control of mixture. • Better fuel distribution. Easier cold weather starts. • Difficulty in starting a hot engine. Vapor locks during ground operations on hot  days. • Problems associated with restarting an engine  that quits because of fuel starvation.