What determines LOP or ROP procedures?

[ryanbatc 12,854]

I've noticed various single and twin props I have use differing procedures for leaning.  What determines how to lean?  Does it depend on fuel injection or carb?  Or turbocharged or not?

 

Also for both procedures do I lean 100 degrees from peak or 50 or what number do the pilots use?

[fs4fun 366]

Ignoramus here. I think it may partly depend on cooling. Some engines would overheat on LOP because they depend in part on the fuel to help with cooling the engine, but otherwise LOP should be preferable because it's less fuel and more range. I just back off peak until I hear a change in engine sound.

[LAdamson 240]

To get the best out of "real life" LOP, you need fuel injection. You also need cylinder head and exhaust temp guages for each cyclinder. And then the fuel injectors should be balanced. For simming purposes, I'd never worry about it. I just lean until the simulated engine sounds at best power. It gets quite noticeable around 6000' if you don't lean.

 

 

For my real life plane, I'd lean until rough, and then three twists rich, on the red mixture knob. That's kind of a Cessna method, even though my plane wasn't a Cessna. But it had a Lycoming. In my case, I knew that my exhaust temperature should be running around 1325 F. This wouldn't apply to everybody. It was particular to my plane, because of the location of the temp probe in the exhaust pipe, and the fact I was only measuring cylinder #3, which is usually the hottest on a Lyc four cylinder. When using that 1325 F. as a baseline, and those three turns rich, I avoided fouled plugs, and had a good running engine. My engine had a carb.

 

 

IMO, there are too many variables, to try to simulate all of the aspects of running ROP or LOP. Even with my carb, there is a chance that perhaps one cylinder is slightly running LOP. Simulating all of this correctly, could be a sim within itself. I think it's just important to simulate the need to lean ( with no turbo or supercharging), as density altitude increases.

 

P.S. --- now that the LOP proceedure is much more accepted than in the past (even though it was well known in WWII), pilots use LOP for less fuel consumption. Running LOP will result in a slower top speed, but saves enough in fuel to make it worth it.