ROTAX Electric Systems
The ROTAX engine has 3 (three) seperate electrical systems
- battery charging 1 (which runs all the aircraft system such as radio, lights, some instruments, sterio, etc.
- Engine ignition system 2 (provides spark to the engine running)
- Engine ignition system 3 (provides spark to the engine running)
Overloading electrical system can lead to stator damage.
Internal generator
- Standard equipment on all 9 series engines is an internal generator rectified externally to 14 volts DC for charging battery for 12 volt system.
- 18 amps is maximum capacity at full power engine RPM.
- 14 amps is maximum continuous design load
- Exceeding 14 amps on a continuous basis will damage stator
Optional external alternator/more power/two electric systems
- Add external alternator (separate 40 amp system) for more power if needed
- S-LSA must get permission and specific instructions for installation from the airframe manufacturer.
- If you install, separate dual electric system is best.
Low RPM starting/problem avoidance
- Rotax ignition system output power is dependent on engine RPM, low RPM is less power.
- Car system ignition runs off battery full power (12 volts) all the time, however, if battery goes dead, engine fails.
- ROTAX ignition separate from battery system and therefore more reliable.
- Healthy engine requires about 240 RPM to start
- Typical cranking speed is about 360 RPM for healthy engine in warm weather with fully charged battery.
Starting problem avoidance
- Starting problems are typically:
- Fouled carburetors from storing aircraft with un-stabilized auto gas because idle jets become fouled (requires carburetor service).
- Insufficient cranking speed from undercharged battery, loose grounds, or undersized starting cables.
- Old spark plugs fouled from lead deposits
- Spring pack in the Torsional damper becomes soft (gearbox requires service)
- Sprague clutch on starter is worn out (requires service)
- Starting problem is not typically electric ignition if both ignition systems were functioning properly during your last flight. it is unlikely that your ignition system is the cause.
- At low starting RPM, can not see spark if cap is pulled to check for spark (as with automobile engines). Spark adequate to start engine but too weak to be seen except maybe in the dark.
- If you disconnect plugs and try starting this will burn out the stator. Have plugs grounded/plugged in when cranking over engine.
- When engine is running at idle RPM, plenty of energy to see spark.
LOGBOOKS – ENGINE TIME
- Engine logbook should be a separate logbook from the airframe logbook.
- Hour meter is important. Some systems, when master switch on, the engine is gaining hours. This can be a waste of engine time and expense if master switch is accidentally left on.
- Hour meter that only records time while engine is running better, such as oil pressure switch or RPM sensor.
Next: Starting, idling, carbs
