Engine/Propeller efficiency
Paul Prentice published tables in his 1991 book "Fly About Adventures and
the Ercoupe." His tables have checked out pretty well, from my experience with
measured speeds during in-flight observations. Ed Burkhead
The following material is used by permission of the author and copyright
holder, Paul Prentice. Paul may be contacted at
Flyabout1@cs.com
to request
permission for any other use. All rights reserved.
For each engine, these are at the "recommended cruising RPM according to the
"Operators Manual" by Teledyne Continental Motors Form X30012 FAA approved
Dec. 1980.
All numbers @ 5.1 degrees Celsius @ 5,000 feet.
prop=ST7351 IAS=106 TAS=114
prop=CR7353 IAS=111 TAS=119
C-90 @ RPM=2350 prop=CL7150 IAS=106 TAS=114
prop=ST7152 IAS=110 TAS=118
prop=CR7153 IAS=114 TAS=123
C-85 @ RPM=2400 prop=CL7148 IAS=104 TAS=112
prop=ST7150 IAS=108 TAS=116
prop=CR7152 IAS=112 TAS=121
O-200 @ RPM=2500 prop=CL6948 IAS=103 TAS=111
prop=ST6950 IAS=108 TAS=116
prop=CR6952 IAS=112 TAS=121
For comparison: The C-85 with a 50 inch pitch prop. The 50 inch pitch means it would theoretically travel 50 inches forward during one turn.
113.6 miles/hour = (50 inches * 2400 rev/min * 60 min/hour ) / (12 inches/foot) / (5280 feet/mile)
ENGINE PROP COUPE AVG CRUISE TIAS TAS MAX IAS TAS
TYPE SIZE MODEL EFFICIENCY RPM SEA LVL 5000' RPM SEA LVL 5000'
C-75 7351 C-D 97 2275 106 114 2275 106 114
C-85 7150 CD-to-G 95 2400 108 116 2575 116 125
C-90 7152 F1-F1A 95 2350 110 118 2475 116 125
C-90 7153 A2-A2A 97 2350 114 123 2475 120 129
O-200 6950 D-G 91 2500 108 116 2750 118 127
These are the best table I've seen.