Foxbat a22ls

[TomBrownlie]

hi guys,

 

Just wondering what fuel economy people are getting out of 912 100hp rotax in cruise and what speed ias

 

 

[Downunder]

Won't get much more than 85/90K (with the big tyres) at about 16LPH.....Crank it t0 5500 and get about 18LPH without much extra gain in speed.

 

Couple of variables are fuel tanks, big or standard and prop type/pitch setting.

 

 

[Bennyboy320]

Did a trip a few months back from Caboolture to Hervey Bay & return, 3.3 hrs & used 45 lts, 5000 rpm at 90kts, just under 14ltr/hr.

 

 

[Segal101]

90 kts , that's impressive at that fuel burn rate , I didn't think they would cruise at that speed comfortably !

 

 

[Downunder]

Won't get much more than 85/90K (with the big tyres) at about 16LPH.....Crank it t0 5500 and get about 18LPH without much extra gain in speed.Couple of variables are fuel tanks, big or standard and prop type/pitch setting.

Not sure how much it matters but I use 98 octane unleaded.

Is there a difference in fuel use when on avgas or 95 unleaded for that matter?

 

 

[rdarby]

I cruise at 85kts at 5000rpm and burn 16 to 18 LPH. It takes a lot more fuel to go only slightly faster. I plan at 20 LPH. This is not a fast aircraft I'm afraid.

 

I would think that you may use slightly less 98 than 95 but I bet that individual flying skill would be a bigger factor than the fuel used.

 

 

[Downunder]

I would really like to see a Foxbat with a "cruse" wing. Bring the stall up closer to 45kts and sleek wing would be great for 100kt plus crusing.

 

 

[TomBrownlie]

thanks for the reply guys being playing with the prop seem to be getting a bit better fuel burn it was too coarse full throttle straight level was only full 5200 revs. now got it set to do 5500 flat level. 90kts burning about 19lts

 

 

[DrZoos]

I have noticed no difference in my rotax on 98 v 95 . I ran mine on 98 for several months.

 

There are extraneous variables, but no notable difference.

 

 

[Downunder]

thanks for the reply guys being playing with the prop seem to be getting a bit better fuel burn it was too coarse full throttle straight level was only full 5200 revs. now got it set to do 5500 flat level. 90kts burning about 19lts

I think you may still have it too coarse. I'm pulling 5500 on climb out (55/60kts) and think this is a good way to set it.

It will pull over 5500 quite easily flat and level......

 

 

[Downunder]

I have noticed no difference in my rotax on 98 v 95 . I ran mine on 98 for several months.There are extraneous variables, but no notable difference.

I always use 98. The theory being that if there is any octane degradation, I will still be at a safe octane level.

I think fuel in plain vented tanks is prone to some degradation after a week or so....

 

 

[SDQDI]

I always use 98. The theory being that if there is any octane degradation, I will still be at a safe octane level.I think fuel in plain vented tanks is prone to some degradation after a week or so....

Our local servo has only recently changed over to 98 all we had before then was 95 but I never had any problems.

I thought I had been told that 95 was more reliable than 98 as when the aromatics disappear out of 98 (if not used in a timely manner) it ended up back at 91 whereas 95 was a bit more stable. Now I don't know how true it is as I am no expert in fuel matters, so I try not to store any fuel for too long and if it is there after a few weeks it gets put through the commodore.

 

 

[eightyknots]

Our local servo has only recently changed over to 98 all we had before then was 95 but I never had any problems.I thought I had been told that 95 was more reliable than 98 as when the aromatics disappear out of 98 (if not used in a timely manner) it ended up back at 91 whereas 95 was a bit more stable. Now I don't know how true it is as I am no expert in fuel matters, so I try not to store any fuel for too long and if it is there after a few weeks it gets put through the commodore.

I have heard that too (read in a motoring magazine about ten years ago) but I have never been able to get any verified facts. Does anyone know where to get this data?

 

 

[TomBrownlie]

well the bloke that delivers the fuel here reckons if you keep 98 in 40 4 drums it should keep its grade for atleast 12 months dont know what others opinion are.

 

 

[Downunder]

well this bloke that delivers the fuel here reckons if you keep 98 in 40 4 drums it should keep its grade for atleast 12 months dont know what others opinion are.

SEALED drums are fine but what we are talking about here is fuel in aircraft tanks which are vented to the atmosphere.

To get the higher octane chemicals such as butane are added to the fuel.

 

These chemicals can "cook off" to atmosphere reducing the octane.

 

Obviously no one wants to run a lower octane than recommended for their engine.