Hello everyone,
I'm new to the forum but have flown various Rotax 912ULS engines over the years without issues. However, following the latest Service Bulletin (SB-912-079), I've found myself with a few questions that I hope some experienced users here can help me address.
Over the past 10 years, I’ve flown two different Tecnam P92s, each equipped with a Rotax 912ULS and a fixed-pitch wooden propeller, typically reaching about 5300-5400 RPM on takeoff at wide-open throttle (WOT). These aircraft didn't have a Manifold Pressure (MAP) gauge.
Currently, I’m flying a Savannah with an E-Props V20 fixed-pitch prop, and on takeoff, it hits 5500 RPM. This aircraft has a MAP gauge, which indicates between 28 and 30 inches of MAP at takeoff, depending on atmospheric conditions—exceeding the MAP limits stated in the SB for using RON95 fuel.
I have always used European E5 gasoline (maximum 5% ethanol, RON95) as recommended for anti-knock properties.
The engine on my Savannah has about 50 flight hours, all performed with RON95 fuel, running at around 5500 RPM and approximately 30 inches of MAP for the first 2 minutes of flight (takeoff and initial climb). So far, I haven’t experienced any issues.
Unfortunately, where I live, RON98 fuel is not always readily available.
Here are my questions for those with more expertise regarding using RON95 fuel:
1. After reaching a safe altitude post-takeoff, would it make sense to throttle back to stay below 27-28 inches of MAP, which seems to be a safer range according to the SB?
2. Without noticeable detonation, could briefly exceeding the SB's MAP limits during takeoff have any measurable long-term impact on the engine? Specifically, is there evidence that this practice could lead to engine damage over time?
3. This question isn’t directly related to the SB, but I’m curious: 5500 RPM and 30 inches MAP exceed Rotax’s Maximum Continuous Power (MCP) specs (5500 RPM and 27 inches MAP). Should I consider this setting limited to 5 minutes of operation only?
Thank you in advance to anyone who can shed some light on these questions.
