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M Roberts wrote:
Conventional wisdom has me confused. Is it saying that the piston engine does a better job at converting the fuel to work, and the Rotary wastes a lot of fuel to heat the engine? But haven't we had reports of Rotaries flying formation with Lycs with equivalent airframes and getting effectively the same fuel burn, thus blowing a whole in this whole BSFC argument? Would the answer to my question be that at equal burn rates, the Rotary would spit more heat out the exhaust and have less to reject through other means, but it also wouldn't be producing as much power?
Yes. Depends on your definition of "a lot". Tracy gets good numbers flying where the airframe is most efficient. This is slower than most people fly. IIRC Tracy burned about 1 gal an hour more than Charlie flying down to Texas. This was not a perfect test and I am going by fallible memory of a phone conversation with Charlie. Even if the fuel burn is 10% more it is really not worth worrying about if you fly the normal 200hrs per year. If you are worried about the 10% there are people out there who have the answer-Turbo compound. All you need to do is spend about 10 million in development to get your $800 a year in fuel back. Or you could just slow down and enjoy the view. Don't we all want MORE time in the cockpit? Now THERE is a no brainer!
Monty
The actual total spread was somewhere between 1 & 2 gallons over the whole 3.5 hour flight. Would have been a slightly bigger spread but I was flying wing & I'm pretty sloppy at flying wing on a long cross country.
I'd love to do the same flight side by side with him at real RV speeds. Monty's right; 5-10 % fuel burn penalty is not too terrible a price to pay if you're saving $10grand on the front end & another at overhaul. If you invest the money at the beginning, the gain will pay for the extra fuel & you'll still have the $10k at overhaul time.
Charlie
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