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What's your o200 performance like?
So I should start off by saying I've got about 10 hours in a Cherokee about 12 years ago and have done the rest of my time, got my licence and all in my 750 still.
I've always thought it was a bit underpowered, but it's a small GA plane shaped like a 6x6 so it's not going to be a speed demon.
I get about 2500-2550 WOT in a climb at about 1000ASL, and anywhere from 300-500fpm climb rate at gross. Solo full fuel and me (240lbs) I hit 500-700. Definitely below 1000fpm.
I cruise about 75mph at 2300rpm and maybe 80-82mph at 2450, which is basically WOT leaned out. Other people seem to report 85+mph at 2400 and I'm definitely not anywhere near there.
I finally took a flight in a buddy's 150 and he was hitting closer to 2700rpm in a climb and we were climbing better than the zenith. Same day, maybe an hour apart. Both planes running a 69x48" prop.
So that brings me to my question of am I currently over propped? Seems like turning 2550rpm compared to 2750 will lose about 8-10hp. I've seen other people seem to be running 72x44 or even 76x37.
I've read a few other people and they seem to be getting both faster than me and better climb. It's got me thinking... Anyone have any anecdotes to share?
Replies to This Discussion
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Permalink Reply by Clint L Gosch on
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Hi Nick,
Your climb rpm seems to match mine, I climb at 60mph indicated with 2570 rpm and get about the same rate of climb as you maybe a bit more but not much. My plane is 840lbs, I'm 250lbs, full fuel is 150lbs, my elevation is 860msl. I can get a bit more rate of climb by pulling the nose back to 50mph but 60-65mph let's me stay out of the way of the class C traffic I have to deal with. My prop is a whirlwind 70" GA pitched to 13 degrees. I normally cruise around 3000'msl (around 4000" density altitude) and can get 84mph true (80mph indicated) at 2600rpm. I've left it wide open and leaned to get 2670rpm at a bit higher altitude and gotten 89mph true but it tends to burn a lot of fuel for not a lot more speed. I'm running the smaller cruzer tires on my STOL. A normally aspirated engine won't make 75% power above 3000' density altitude according to the o-200 performance charts so don't be afraid to spin it up a bit more to get some speed, but i'd guess your prop may be limiting you on the RPM. I've found the o-200 to be adequate for what I use my plane for, but the only time it's made advertised climb numbers was on a cold day with minimum fuel, I was 30lbs lighter too. True airspeed at max continuous power at sea-level on a standard day might hit 100mph, but I've never experienced a perfect standard day at sea-level. I played with pitching the prop down to 11.5 degrees (2680rpm at 50mph), climb did improve by 80-90fpm but I lost a about 8mph in cruise. I'm currently running an aeronca exhaust system, not known for being the most efficient. I'm planning to upgrade to a Vetterman system so I can start cleaning up my cowl, should improve the looks and the sound... Vetterman claimed I could expect a 50rpm increase by using thier cross over system, might improve my climb a bit. I've seen decent cruise numbers at 2400rpm on Jimmy Young's C90 equipped STOL, I think he's pitched a bit higher to take advantage of the higher torque output of the C90.
Sorry for the long response but bottom line is your numbers don't seem to far off from mine given our prop differences. Hope this helps, feel free to contact me if you have any other questions.
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You might also play with different flap settings to see how it affects your climb performance. Mine seems to climb at its best rate with a little less than 1 second of flap travel and at 50mph.
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