Propellers for Ercoupes


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The standard propeller that was furnished with all C-75 Ercoupes was a Sensenich 74FC48T, a wooden climb propeller.

Later on, additional propellers were allowed for this airframe & engine combination, many of them had been carried over to higher performance engines.

Surprisingly any any fixed pitch wood propeller that is approved for the Continental c75/85 engine, and that falls within a static R.P.M. range of 1900 to 2050 can be used. Fifty R.P.M. additional is allowed at each end of the range to cover instrument errors and variable conditions, making the total range permissible in field operation 1850 to 2100.

Not many people use wooden propellers anymore, but recently there has been a trend to embrace wood again as a material for props. The dampening qualities of wood and the weight saved and probably the saved money also are the decision factors here.

The C-75 uses a 73-74 inch prop, while the C-85 is shorter (71-72 inches) to allow faster running.

PropellerSensenich
74FC48T
(Standard Equipment)
Sensenich
74FC52T
Lewis L55C
72” Dia.
49” Pitch
McCauley
1-A-9O
73” Dia.
51” Pitch
Cruising Speed at 2275
Maximum Speed
R.P.M. at Maximum Speed
Max. Rate of Climb at Sea Level
Take-Off dist.,Turf, Zero Wind
103MPH
121MPH
2600
700’/min.
560 Ft.
108MPH
120 MPH
2520
680’/min.
620 Ft.
111 MPH
118 MPH
2420
610’/min.
600 Ft.
109 MPH
122 MPH
2500
710’/min
520 Ft.
------------McCauley 1A90 Service Manual

Not to the surprise to many, the aluminum McCauley outperformed all other propellers, even though pitched for a normal to cruise setup. It made the McCauley defacto the standard Ercoupe propeller.

More to performance from the Sensenich publications:

PROPELLER PERFORMANCE

In selecting a propeller, keep in mind that both aircraft and engines of the same model may vary in performance, and that operators may want different performance characteristics. For instance, one person may require a high climb rate while another seeks maximum cruising efficiency.

STANDARD PITCH / NORMAL FLYING
For normal or cross country flying, a fixed pitch propeller that turns between rated engine RPM and 50 RPM over rated at full throttle level flight at sea level will give best all-around performance.

CRUISE PITCH
A cruise propeller will turn 50 to 100 RPM under rated engine RPM at full throttle level flight. While cruise pitches will provide 4-6 mph higher airspeeds at cruise power rpm’s, maximum level flight speeds are no better than climb or standard pitches, and the take-off and climb performance will noticeably suffer.

CLIMB PITCH / HIGH ALTITUDE OPERATION
For improved take-off and climb performance, use a climb pitch propeller that will turn 100 to 150 RPM over rated engine RPM at full throttle level flight (refer to your particular aircraft Type Certificate for propeller limitations). Climb pitches will typically reduce flight speeds by 4-6 mph at cruise power RPM’s. A climb pitch is also recommended for aircraft operating from high density altitude runways.

And here another article about torque versus rpm and the right propeller to use: Torque versus RPM



Page last modified on November 03, 2016, at 03:26 PM