• Above all, it has to be reliable. When it's needed, it has to work - period.
• It should operate for as long as needed. Whether it's the last 10 minutes of a Sunday pleasure flight, or you're crossing the Atlantic.
• It should be maintenance-free. Benign neglect should not prevent it from working.
• On the rare occasion it's needed, it should automatically engage without operator intervention.
• A simple and convenient pre-flight check should confirm it's working properly.
• This P model ignition has an internal three phase brushless alternator that produce enough power to sustain the ignition when the engine is turning 800 rpm, or more. If the aircraft buss voltage goes off-line, the ignition has an internal alternator. With this arrangement, dual electronic ignitions can be run "clean". No back-up batteries and no back-up magnetos.

The P Model Built-In Alternator

• Adds no (zero) mechanical contact/wear parts to the system
• Adds only a few ounces of weight
• Requires no additional hardware to install
• Will operate as long as the engine is turning

• Adds wiring, switches, and batteries not part of the ignition kit typically provided by the manufacturer.
• Adds installation complexity.
• Adds maintenance.
• Offers a finite interval of back-up power.
• Offers marginal confidence insofar as batteries are not known for unquestioned reliability.

• Compromises the advantages of variable ignition timing and dual spark. Most of the time, mag timing (fixed) will fire before or after an electronic ignition using variable timing. Aircraft engines are designed for simultaneous firing from two plugs. Firing on one plug is not optimal.
• Compromises the maintenance advantage of electronic ignitions. The owner has the same inspection, maintenance, and cost components as before, albeit for one vs. two magnetos.

• Doesn't reduce the maintenance associated with magnetos. It adds what ever (minimal) attention is required for the electronic side.
• Doesn't eliminate underlying reliability issues associated with magnetos.
• Doesn't streamline the cost and complexity of the ignition package, as a whole. It makes it more complicated and much more expensive to produce.
• Requires spark plug gaps be set so magnetos are able to fire. A key advantage of electronic ignitions is the ability to increase spark plug gap to nearly double that of a magneto. You can't do that if your power back-up plan has the plug firing from a magneto.
  

WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov.