Air Racing for Rotax 912 Series Engines
For aircraft with Lycoming and Continental engines racing means wide open throttle (WOT) for anything up to an hour. For these ‘classic’ engines WOT for long periods is not an issue as they are very low revving, and the difference between cruise and WOT is small. For aircraft with the Rotax 912 series engine air racing is virtually impossible due to the strict 5 minutes at max power limitation.
Rotax 912 Racing
It is common in the UK that aircraft (microlight or Group A) fitted with a Rotax 912 series engine cannot achieve full rpm. This occurs because of the BMAA & LAA airworthiness rules, weight restrictions and airframe restrictions (VNE). To stay within the rules the propeller is set or made very course thus not allowing maximum RPM in level flight. The specific information for each aircraft may be available from the flight test record at initial permit application, should the aircraft be young enough.
Questions for Rotax Gmbh.
- Is maximum continuous power for a Rotax 912 series engine always measured from RPM?
- Is running the engine continuously at maximum RPM below 5500 allowed within the performance limitations?
Certifying a Rotax 912 for racing
Prior to racing;
- Provide the pilot with the relevant information
- Review the aircraft ‘flight test record’ (where available) for VNE & Engine speeds
- Record the maximum RPM achieved in level flight with WOT
- Record the airspeed, OAT, QNH
- Ensure the throttle is WOT and has no further travel
- Validate that the aircraft achieved 100mph (87knots)
- The pilot signs a Rotax 912 declaration
Rotax 912 declaration
I confirm that my aircraft, fitted with a Rotax 912 series engine, is not capable of generating more than 5500rpm in level flight.
I understand that to compete in a 3Rs air race that I need to run my engine at wide open throttle (WOT) continuously for the whole race. If this operation is outside the limitations of the Rotax 912 series engine (maximum 5500rpm for 5 minutes) then it is likely to damage my engine and I am responsible.
- These assumptions are only valid for Fixed pitch propellers. Further thought and procedures will be required for variable pitch or constant speed propellers.