08-12-2009, 06:44 PM
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Join Date: Jul 2005
Location: Detroit, MI
Posts: 1,587
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A Study of Propulsive Efficiency
Moderators - please feel free to relocate this if I placed it wrong.
This data is for a C152. The first five columns are from the POH. SFC is calculated from BHP and GPH.
The C-152 is what Jack Norris and others used in their propless glides back in the mid 90's to get near-perfect drag curves. I used the best L/D and drag at that speed from their data to compute the drag and THP for each speed and altitude shown here. THP/BHP gives propulsive efficiency. The C-152 has poorer propulsive efficiency than an RV because the airplane is not as clean. That said, it is instructive to note the big differences at various speeds and altitudes. (ignore the last two lines of the 2000' section because they are estimated.)
I don't know if the relationships are the same for RV's between altitude, speed or RPM and efficiency. I'm working on that.
__________________
H. Evan's RV-7A N17HH 240+ hours
"We can lift ourselves out of ignorance, we can find ourselves as creatures of excellence and intelligence and skill. We can be free! We can learn to fly!" -J.L. Seagull
Paid $25.00 "dues" net of PayPal cost for 2015, 2016, 2017 and 2018 (December).
This airplane is for sale: see website. my website
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