Constant Speed Propeller advice
I've been flying the Warrior since its release but I also own the Arrow III. So I decided I wanted to spend some time with it as well, but I'm not sure I'm following the correct procedures for a constant speed propeller. I've tried looking at various forums and the operating procedures, but it seems pretty grey. So, going to tell you what I think is acceptable, and if someone(s) would be kind enough to validate or correct me, I'd appreciate it.
For takeoff I have the Propeller full forward (full RPM's?) and the Manifold Pressure at 100% as well. As I climb out, I keep both at 100% but lean the engine for power, until I reach my cruise altitude, for this purpose, 8000'. Once at altitude I set 2500 RPM (best power setting?) and at 8000' the charts say to run full Manifold Pressure for 75% power, then lean to EGT +100 degrees F. Is all this an accurate use of a constant speed propeller? I'd really appreciate any feedback, positive or negative.
You should consult the flight manual for precise settings. In general, you don't do anything terribly wrong, but 2500 rpm in cruise should be pretty loud and inefficient. Normally, you do the following:
Takeoff: all full forward;
Climb: full throttle, prop 2400-2500 rpm (or full forward), mixture rich and leaning from 3000 ft up;
Cruise: use cruise charts from FM/POH: throttle in green, RPM in green, mixture for best power/flow;
Landing: prop/mixture forward.
You increase power prop first then throttle, you decrease throttle first then prop.
Thanks so much for the response. Yes, I am using the Performance charts to get the numbers I used, I just wanted to make sure I was applying them properly. I didn't really think about the noise level in the cabin, that is probably why they have power settings for both 2200 and 2500 rpm. I didn't notice the noise was any louder than the Warrior, but I'll fly them back to back today, so should be able to compare.
The following applies to normally aspirated Arrows.
According to my maintenance folks, you can run an IO-360 all day long at full throttle and RPM and still get home to tell about it.
With that said, here is what I was taught;
Careful with leaning. From memory, the engine operators manual state not to lean above 75% power. A good rule of thumb is not to lean below 5,000 ft (you can't generate more than 75% power there.) You really don't need to lean the Arrow until you get to cruising altitude unless you are climbing above 8,000 ft MSL or so. By delaying leaning, you will keep the cylinder heads cooler.
Take off with full throttle and max rpm. If below 5,000 ft, its easy... all the levers go full forward. If above 5,000 ft, full throttle and full rpm, then lean to 100 ROP or maybe a little richer.
I was taught (and I bet there will be differing opinions here) to reduce power to 25 squared at 900 ft AGL (to minimize the time to get to an altitude where you can safely return if you loose power). This is subjective. If you are more comfortable attempting a return to the field upon loosing power at say 1,000 ft AGL or 1,500 ft AGL, then keep full power in until you reach that altitude. I hold 25 squared until I reach cruising altitude (at some point you will no longer be able to get 25 inches of MP if you are climbing above 4 or 5,000 ft... in that case just use full throttle and 2500 rpm).
At cruise altitude set MP & RPM to get desired performance. If in doubt, 24 squared works well in any Arrow. Lean for desired performance if above 5,000 ft (or if you are sure you are generating <= 75% power)
So to sum it up, balls to the wall for takeoff, 25 squared for the climb, and 24 squared for cruise and only lean above 5K MSL. That's easy enough to remember without having to reference the POH.
@berniev Thanks! Good information as well, so 2400 RPM is less wear and tear on an engine than 2500?
@katchaplin The vibration at 2400 rpm is less annoying, especially with a 3 blade prop. I think it's more a matter of personal preference. Refer to the poh for valid combinations of RPM and manifold pressure . The older arrows, especially to 180 horsepower iFly, generate 75% power at 24 squared.
so 2400 RPM is less wear and tear on an engine than 2500
Let's say, it's less load. You can think of the manifold pressure as the amount of power the engine delivers per cycle and of RPM as a multiplier, i. e. how often this power is delivered. In the real world, vibration can be a concern, too. As has been truly noticed above, IO-360 is a rather enduring engine. So for purposes of setting power you reduce to 25/2500 or 25/2400 in climb mainly to increase your comfort and the comfort of those on the ground around the airport. If you don't care, you can climb at full/full.