Rotax fuel consumption?

[Confabulous]

I'm currently researching the Ban-Bi, which has a Rotax 912/912S, in an effort to work out how much I'm going to pay for building/running it in total (I haven't bought it yet). In order to do that without breaking the bank, I'm creating an accurate sim model in X-Plane (I know it'll only be 95% accurate but that's enough for me if I get the Cd, shapes and airfoil right)

The thing is, it appears the Rotaxes (Rotaxii?) burn MORE fuel at higher altitude (in real life) for the same RPM, whether wobbly prop or not. How is this possible? I don't understand it. Does anyone have any experience with Rotax products? I know the V220T is coming out, and that's FADEC etc, but they'll never get a 220hp engine on the a/c so it's not relevant.

Any thoughts? I've searched the net but it's not giving me realistic SFC figures at altitude. I know it's a long shot, but someone might be able to help.

PS: How does the Ban-Bi (or any aircraft) get a relatively high roll rate with flaperons? The roll authority of the flaperons is only +3/-5 degrees!

[ChrisVJ]

My 912S uses 18 litres/hour at 5,200 revs.

While it is interesting to know and gives a very rough guide to running costs I'm not sure why people get worked up over the exact consumption or fuel cost.

There was a thread on another site that asked whether the poster could use 87 Octane gas in an uprated 912.

Simple really. Even if you used 10 Gals /week average and bought the best gas as opposed to the cheapest the difference would be about $75 a year.

If that bothers you for Pete's sake get rid of the plane. Who wants to risk death for $75?

[Rod1]

I am 95% of the way through building an MCR-01 Club. I assume you are going for the MCR-01 VLA not the MC100? All Ban-Bi’s so it gets confusing! I will PM you my contact details and you are welcome to give me a call; I have flown the VLA, Club and the ULM.

In real world use you will get about 18lph using Mogas. Avoid Avgas if possible as it is bad for the engine with increased oil changes etc to try to get read of the lead. I was running an AA5B with a fuel cost of £45 ish per hour, so £17 to go faster was a considerable inducement.

Rod1

[Evil J]

Incidentally, whilst on the subject-how do you go about getting Mogas at the larger airports?

[Rod1]

No Mogas at larger airports that I know of. But provided I keep Avgas use to a minimum, by using Mogas from home base etc I expect to avoid the worst of the problem. The engine is cleared to run on it, it just does not do it any good and with an endurance of 4.5 hours at 130Kn I can get a long way between refills.

When 100LL dies Mogas may become available at larger establishments, after all, most of the GA fleet can run on it and there is no other alternative without changing every Piper and Cessna engine for a JetA1 burner.

Rod1

[Genghis the Engineer]

Apart from copying most microlight pilots and using a couple of jerry cans, Sywell has a MOGAS pump.

G

[Evil J]

Pressumeably then you can mix MOGAS and AVGAS in the tank in any ratio then?

[Mariner9]

No probs for Rotax engines mixing 100LL and Mogas in any ratios EJ. But as Rod 1 mentioned earlier, the lead doesn't do the engines any favours if used excessively.

100LL is also :mad: :mad: expensive too ;)

Rod, when do you expect to get your MCR flying?

[Rod1]

She is booked in to be painted in about 6 weeks. After that there will be a number of little jobs. My estimate is around Christmas for a finished aircraft, but then the paperwork will need to catch up and test flying needs happen. Because of the time of year it may be April before she comes out to play.

Rod1