Subject: [FlyRotary] Re: Shady Bend /
economy test
Tracy Crook wrote:
> At 9.5 GPH and 100 MPH I was climbing at
1500 fpm and getting 10.5
> MPG. It took 40 seconds to climb 1000
feet. Hmmm, I thought, what
> is the average MPG if I
get 10.5 MPG for 40 seconds and 55 MPG for the
> next 5
minutes? I think the answer is around 48 MPG but that seems
> to be too good to be true. Seems like some one would have used
this
> technique long ago if it would give a 60% increase in fuel
economy.
> The error in the EM2 fuel flow readout may be higher
at this low flow
> but nothing like 60%. Any math majors out
there see a flaw in my math
> or logic? Or maybe I was in a
giant thermal at the time? I repeated
> the test twice so I don't
think so.
>
Were you decending at 100mph? If
not, then it is an apples and oranges
comparison, isn't it?
You
went 1.1 miles at 10.5mpg, using .105 gallons.
Assuming a decent speed of
100mph, you went 8.3 miles at 48mpg, burning
up .174 gallons.
In the
total 9.4 miles, you used .279 gallons, for 33.7mpg.
Does that sound
closer to reality?
Actually it was 55 mpg during the descent portion of flight.
I was looking at MPG averages so speed never entered the picture in my quick
& dirty look at this.
But you suggest another way of cross checking the results. Let's
see, I think I agree with your miles traveled calcs so lets look at
it this way. I burned .106 gal in the 40 seconds of climb and
.125 gal during the 5 minutes of descent for a total of .231 gal.
9.4 miles divided by .231 gal gives 40.69 MPG. Not as good as I got
by averaging the MPG during each unit of time (48 mpg result) but
still a pretty good bump up from 30 mpg in level flight. Not sure
where the error is coming from.
Naturally my test results will have to be repeated many more times
before I accept them as fact.
Tracy