Expected Climb with Catto Prop and O-320 in my 6A

I already have 11 hours in my Phase I and getting more comfortable in the plane. I am starting to sort out documenting performance and wondering what I should be expecting.

I have not done any real climb tests, but today I paid greater attention to climb performance. Coming off the runway at 100 MPH, I was getting 1500 FPM and felt good about that. However, at 1000 AGL, I pulled the power back a bit (forget now that setting, maybe 2400 or 2500) and went to a 140 MPH cruise climb. At both 120 and 140, I only seem to be getting 750 FPM when stabilized. Should I be climbing at full throttle? What is a recommended cruise climb to get better results. The prop seems pretty course.

Today I got to 8000 DA or so and was seeing 199 MPH at WOT and best power mixture (leaned to peak RPM), so it would seem that I am not too course of a prop.

I am wondering what type of climb I should be expecting from this prop and the best way to get it.

My engine is a freshly overhauled O-320 / 160 HP.

Thanks for your assistance here.

I think you should climb WOT and full rich. This opens the enrichening circuit in the carb and the butterfly is straight vertical, providing most even fuel distribution, thus best cooling in the climb. Given that, then airspeed will dictate vertical speed. I can climb out at 120 knots and 1000 FPM or better and 80-100 knots yields 1500-2000 FPM. Round numbers. At 8000 ft, WOT and leaned to max RPM I'd think you'd go past 2700 rpm slightly, if not, then maybe you are too course

Dbro172 said:

I think you should climb WOT and full rich. This opens the enrichening circuit in the carb and the butterfly is straight vertical, providing most even fuel distribution, thus best cooling in the climb. Given that, then airspeed will dictate vertical speed. I can climb out at 120 knots and 1000 FPM or better and 80-100 knots yields 1500-2000 FPM. Round numbers. At 8000 ft, WOT and leaned to max RPM I'd think you'd go past 2700 rpm slightly, if not, then maybe you are too course

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Thanks for the detail here. Yes, at 8000, I got about 2750 leaned to max RPM, so I am thinking that my prop is properly pitched. Though I would rather get 2800+ so that I can get to 2700 at higher altitudes. So do you run WOT from take off up to cruise altitude? Do you have cooling problems with a 100 MPH climb? I haven't used that speed past 1000' AGL yet.

Larry

Yes, WOT and full rich all the way up to cruise altitude. I will nose it over to 120 KIAS +/- after 1000' or so too. If it still gets too hot, then i reduce throttle and level off for a bit, to get the temps down Then usually when I go back in full throttle the temps are settled down.

Faster

You'll be amazed what a 140 MPH climb will give you at WOT.

Try it sometime,
Best,

Dbro172 said:

I think you should climb WOT and full rich. This opens the enrichening circuit in the carb and the butterfly is straight vertical, providing most even fuel distribution, thus best cooling in the climb. Given that, then airspeed will dictate vertical speed. I can climb out at 120 knots and 1000 FPM or better and 80-100 knots yields 1500-2000 FPM. Round numbers. At 8000 ft, WOT and leaned to max RPM I'd think you'd go past 2700 rpm slightly, if not, then maybe you are too course

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This is more or less my experience with my Aymar/Demuth prop. I typically cruise climb at WOT and 120 knots, yielding ~1,000 FPM. In fact, I went flying during the heat of the day on Friday (it was 88F), and the CHT's stabilized at 400F in a 120 knot climb to altitude at WOT (2450 RPM).

Thanks for the experience here. Does my max cruise speed seem optimum (8000 DA, 2750 RPM, 199TAS) or should I be expecting higher? Just want to know if I should be looking for drag issues. I seem to be hitting or beating Van's numbers.

Larry

lr172 said:

Thanks for the experience here. Does my max cruise speed seem optimum (8000 DA, 2750 RPM, 199TAS) or should I be expecting higher? Just want to know if I should be looking for drag issues. I seem to be hitting or beating Van's numbers.

Larry

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My airplane is pretty clean and that's how fast it would be if I flew it at that RPM. I typically cruise at 2400-2450 rpm and see 150-155 knots.

Just curious what your fuel burn is at WOT and 8,000 DA?

Scott

Sdemeyer said:

Just curious what your fuel burn is at WOT and 8,000 DA?

Scott

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An O-320 running 75% power should be burning around 9.6 GPH, regardless of what airplane it is in. 8,000' DA and WOT should give you right around 75% power.

Leaning

11 hours on a new overhaul is not enough to start leaning.
Do you have evidence that the rings are seated?? How are your CHT's??
The reduction in power and increase in airspeed at 1000' or even 500' is EXACTLY how you should break in a newly overhauled engine. IF you can keep the CHT below 400 F. in a high speed full throttle climb, this is fine.
When you get to 4-5000', run 75% power until you have at least 20 hours on the engine, 25 hours would be more conservative. THEN you can lean.
When you are certain the rings are seated you can accept 425 CHT in climb.
The above numbers come from Mahlon Russell's break in protocol for engines that have not had test cell run. The protocol worked flawlessly for me. Less than 1/2 quart oil in 25 hours.
I have a carbed 0 320 with 10-1 pistons on a very tightly cowled non RV. In ambient temperatures as high as 115 F I was able to stay within the above numbers except for a few second excursion to 425 on the first couple of flights. I DO NOT have piston cooling nozzles on my engine on the advice of a well known engine shop that builds engines for Reno racers.

How many blades?

Hi,

Curious if that's a two or three bladed Catto?

-jon

I have a two blade catto that was set up for a 160HP RV-9. I was surprised that it ended up being pretty close to what I need. I am not sure that I will have it re-pitched.

I do run a bit richer than optimum in most cases. My cruise temps leaned or rich are in the 350-360 range at most speeds. I climb out of the pattern at 100 MPH and never seem to get over 400. I believe that richer is probably better for break in, but millions of engines are broken in every year in the auto world without any deviation from the standard mixture settings in the FI computer and many of these run much longer than our TBO levels. I may pay the price for this some day, but I don't believe that I will.

I learned on my first flight that richer isn't always better. My engine performs poorly on the T/O roll with full mixture. I need to pull it 1/4-1/2" to get good performance.

Larry