POH says 5 min max but without a range it doesn’t compute for me. So realistically what we’re talking about here is you can run max rpm for five minutes or until exhaust gas temperature is reach max allowable. Then you have to let the engine return to normal operating temperatures. So theoretically, if there was some reason for it, you could run full power for five minutes then cruise for 30 minutes and then full power for five minutes then cruise for 30 minutes, etc. etc. As long as your EGT’s return to normal temperature, right?
Link to 915 shows 5500 rpm continuous is allowed. 916 does too in image. https://rotax.my.salesforce-sites.c...rsion/download/0685c00000GmC8OAAV?asPdf=false
Do you ever get up to 10-13k? What does it true out at that max continuous RPM? Seems like 140 knots is doable in several of these LSAs.
Consider it 'takeoff power.' You're managing engine temps just like a traditional aircraft engine. In a Superstol with CS prop, that's 9.5+ gph and 1200-2000 fpm. Full throttle Vy climb deck angle limits forward visibility, so the available power isn't necessary during my normal operations. The 10mph TAS difference from 5.5-6.0gph economy cruise and ~8.2gph max continuous power doesn't justify the extra fuel burn.
Very cool. Thanks for the education! Sounds like setting up with a cruise prop is ideal for XC flyer and there is still plenty of FPM climb out.
The MT 80 constant speed was recommended and its been great. Seems to make the most of the 915 and in a STOL plane every bit of cruise speed is appreciated. Since I have A/P its a TAA for logbook purposes.
The difference is that market forces, not authoritarian government, have created the current situation. And its a good thing that contrary to your earlier point includes demand from a segment of car people who want sustainable simplicity and choose to spend a lot of money on it instead of buying new limited-life cars with their fun money. In the case of GA almost everybody wants sustainable simplicity and for good reason, not least because while you can't manufacture an airplane cheaply, there are lots of planes and engines out there which are and will be good investments, thriving and surviving decades after they were built. While a lot of people were whining and missing the point even pre-2020, I think the best opportunity ever to buy, own and fly light aircraft may now have passed them by as attrition and increased demand has ratcheted the costs upward. Even without COVID politics bumping up demand, no evolved and affordable situation lasts forever and privately owned GA may get to point where something like the Rotax 916 might be able to occupy a small niche in the US market, even at its very high cost level. Maybe clone Lycomings will take over more broadly, as happened with PMA engine parts. For sure the GA market will continue to evolve, but driven by demand not fantasy.
Is it correct that due to engine/gearbox/prop vibration issues the engine cannot use an aluminum prop, only wood core and some composite props?
Whatever 'low inertia' means to Rotax, I guess. I wouldn't hang the extra weight of an aluminum cs setup on the nose even if it were available. The options for the 915 were fixed, ground adjustable, and CS. For my use and resale considerations, CS was the obvious choice.
Am I missing something? Can Rotax be run at full horsepower continuously, despite what the manufacturer says? I read that the 916 is capable of 160 hp during takeoff, but only has 137 continuous hp, which is hardly better than the 135 continuous hp of the 915. Can the 915 run at 141 hp full time, and will the 916 be able to run at 160 hp all the time?
See my prior post. They both show 5 min max. The other poster FancyG explained the temp component. Over temp seems like a clearly bad idea at any altitude
So at 2,500 feet the rotax and a 150 hp O-320 are tied. Two minutes worth of climb at 600 feet a minute gets you half way there. If it’s 5 minutes at 160 then 4 minutes worth of climb gets you to about 2500 feet just in time to reduce power down to what the O-320 is making. Assuming a STP day at sea level. On a hot day it shifts in the favor of the Rotax.
I can’t find an MT-80 on their website. I did find something that said the MT-34 can be used with a 915.
