Tracy, What is your fuel burn, engine or prop rpm, IAS and

estimated

hp

output at your preferred economy cruise speed.  I believe that I

read it

before that you run the engine at around 5000 rpm with a 20 to 1

air/fuel

ratio.  I'm trying to get some numbers to give to a prop

manufacturer so

that they can come up with a prop design for the Glastar.  I

know

that

it is

an apples and oranges comparision but knowing what the engine is

producing

at a given rpm and a know prop size might be useful in

extrapolating

performance numbers for another airplane.

Del Johnson

Prop makers really don't care about that stuff but I'll give a few

data

points for reference.  Prop makers basically want to know:
1.  Max HP
2.  Target max RPM
3.  Airspeed at WOT, level flight
4.  Max allowable diameter.

My prefered econo cruise numbers vary with altitude but at 12,500 I

set

up

for 5300 rpm, 175 [MPH] TAS & 6.25 GPH.

Tracy

Is that about 140 mph indicated? I am trying to relate your figures to

mine. Us Aussies can't breath above 9,500 feet.
Ian

The IAS varies a little with density altitude variations but it is usually
around 135 - 137 IAS at 12,500. Maybe a bit higher at 9,500. If you are
looking for the very best econo cruise number, all the RVs are at their best
at 130 mph indicated, regardless of altitude.

Tracy
tcrook@rotaryaviation.com

 
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