blimpy
New member
Has anybody got or made their own chart of rpm vs % power / altitude/ Manifold Pressure/ fuel flow
for the franklin 150 in the cruisair ?
The manual says the sweet spot is 2435 rpm with the F-200 prop.
Dan T thinks this = 75% power at ~ 3000 ft.
In my local flying / training mode I was using about 8.1-8.5 gph typically cruising at 2400 rpm
at 4500-5500 ft, well leaned.
Past 6 hours have been cross country flown at 2450 rpm, 6500 ft predominantly, full rich for initial climb, slightly leaned for cruise climb, normally leaned for cruise - burning a consistent 10 gph overall.
With my current prop adjustment static rpm is 2550 max.
At 6500 feet full throttle rpm in level flight is 2500 rpm... and 2450 requires nearly full throttle.
I haven't noted the manifold pressure, but can next time.
While the break-in of the 2 new cyls is happening, I guess I need to continue to fly at this "high" power setting.
But I would sure like to be seeing some of the "famous economy" the plane is supposed to be capable of on
cross country flights.
My best guess is that 2300 rpm would be a pretty good compromise between speed and fuel flow.
It would be really nice if somebody had tabulated their experiences.. since there is little info of the kind found in a
"modern POH". I guess there is Franklin chart somewhere.. which might be a start. Forgot about that.
Seems like the thing could reasonably be flown anywhere from 2100 to 2500 rpm
and give fuel flows somewhere between 7 and 10 gph in cruise.
Now to really show my ignorance.. flying at 8500 feet and higher rpm and hp will drop off
as the air thins and the prop itself loses 20rpm/1000 or 200 rpm at 10K feet.
How does one manage their throttle/ and fuel flow under these circumstances ?
Use the M.P guage ??
At lower elevations it makes no sense to run full throttle... when air density limits hp.. what then ?
I'd like to know when I am running 55% 65% 75 % power and be able to predict fuel flow from that.
The kid with the blimp
for the franklin 150 in the cruisair ?
The manual says the sweet spot is 2435 rpm with the F-200 prop.
Dan T thinks this = 75% power at ~ 3000 ft.
In my local flying / training mode I was using about 8.1-8.5 gph typically cruising at 2400 rpm
at 4500-5500 ft, well leaned.
Past 6 hours have been cross country flown at 2450 rpm, 6500 ft predominantly, full rich for initial climb, slightly leaned for cruise climb, normally leaned for cruise - burning a consistent 10 gph overall.
With my current prop adjustment static rpm is 2550 max.
At 6500 feet full throttle rpm in level flight is 2500 rpm... and 2450 requires nearly full throttle.
I haven't noted the manifold pressure, but can next time.
While the break-in of the 2 new cyls is happening, I guess I need to continue to fly at this "high" power setting.
But I would sure like to be seeing some of the "famous economy" the plane is supposed to be capable of on
cross country flights.
My best guess is that 2300 rpm would be a pretty good compromise between speed and fuel flow.
It would be really nice if somebody had tabulated their experiences.. since there is little info of the kind found in a
"modern POH". I guess there is Franklin chart somewhere.. which might be a start. Forgot about that.
Seems like the thing could reasonably be flown anywhere from 2100 to 2500 rpm
and give fuel flows somewhere between 7 and 10 gph in cruise.
Now to really show my ignorance.. flying at 8500 feet and higher rpm and hp will drop off
as the air thins and the prop itself loses 20rpm/1000 or 200 rpm at 10K feet.
How does one manage their throttle/ and fuel flow under these circumstances ?
Use the M.P guage ??
At lower elevations it makes no sense to run full throttle... when air density limits hp.. what then ?
I'd like to know when I am running 55% 65% 75 % power and be able to predict fuel flow from that.
The kid with the blimp
