Bonanza Level Off and Lean Technique in Cruise

FlyWire takes a look at Engine Management in Level off and Two Techniques for Leaning the engine. I must admit I like LOP, if you fly Rich of Peak, please do it with fuel flows at least 100 degrees Rich of Peak!
FlyWire is about exploring flight and the freedom this incredible experience brings us on a personal level. Flying has always captured the imagination and excitement of living life to its fullest. Hi, I'm Scott Perdue. In a former life I flew the F-4 and F-15E, more recently I retired from a major airline. I've written for several aviation magazines over the years, was a consultant for RAND, the USAF, Navy, NASA as well as few others, wrote a military thriller- 'Pale Moon Rising' (still on Kindle). But mostly I like flying, or teaching flying. Some of the most fun I had was with Tom Gresham on a TV show called 'Wings to Adventure". We flew lots of different airplanes all over the country. Now with FlyWire I want to showcase the fun in flying, share the joy and freedom of flight and explore the world with you. Make sure you subscribe if you want to go along for the ride!
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[@ronaldweiner8243]

Just to clarify, the method Scott used was the JPI lean find RICH OF PEAK. That method finds the first cylinder to go over peak, and generally

[@ronaldweiner8243]

And generally leaves you about 10 degrees lean of peak,. The other method, of LEAN FIND ie the lean of peak method will tell you the LAST cylinder to go over peak. So all of the other cylinders are leaner the last to go over peak. Where as in the first method described all of the other cylinders are richer than the first to go over peak. The point is at altitude the engine is producing MUCH less than 75 percent power in a normally aspirated engine and the RED BOX is nonexistent. So no mixture setting will harm the engine and one can fine tune the mixture as desired.

[@Parr4theCourse]

Thanks that is pretty much what I do in a Cessna 182, I’ve got a few full throttle fuel flow settings for my typical cruise altitudes and just adjust fuel flow accordingly. I double check with 50 degrees rich of peak to confirm every once in a while and it’s dang near spot in each time. Thanks for sharing!!

[@FlyWirescottperdue]

Thanks Parr... it's easier than it looks!

[@pg9511]

Hi Scott, I'm a new member. Love it. On this particular video you speak way faster than I can hear. : )

[@FlyWirescottperdue]

Paul, sorry I do have a tendency to talk fast.

[@m1mulder]

Another fantastic video and short and sweet on leaning the engine! Thanks for sharing and as always these videos are top notch on content and quality. Thank you Scott!!

[@FlyWirescottperdue]

Thank you very much!

[@donc9751]

Scott, I've enjoyed every video of yours that I've seen and love learning about aircraft, flying, working on or maintaining them, even though I'm not a pilot (maybe when I grow up, or better still my bank account grows up!) but I'm learning a lot from you and working my way through all your videos! Thanks for your dedication and work to improve the safety and experience of general aviation! Edited to add: When you flew with Frank I watched your eyes with all his actions and reactions and what I saw tells me you didn't miss a thing!! You maybe didn't say anything but you noticed everything I believe! You would be great to have as an instructor!!

[@FlyWirescottperdue]

Thanks Don, I appreciate that!

[@ss442es]

Good information!, thanks!

[@ronhunt2477]

Ok - I'm confused, you are setting your mixture based on finding ROP on your JPI to determine your 14.6 FF. However, in the description above your state if you fly ROP that you should do it with fuel flows at least 100 degrees ROP, but you never set 100 degrees ROP. Instead you are setting the fuel flow that gave you the peek EGT and you are basically leaving it there. EGT may just be an instrument, as you state, but it is the instrument by which you determine your ROP EGT in order to set 100 degrees ROP or run LOP if you choose to do so. I apologize if I am misunderstanding what you are saying. I've owned a V-35 with an IO520 for several years, My engine generally peeks nearly identical to yours at 1480 EGT give or take, however, I don't fly at peek, I normally fly at 100 ROP. 15.5 will always put me in the ball park for 100 degrees ROP at 65% power. I also have GAMI's and D- Shannon baffles and my CHT's at that setting will run in the 325 - 345 range depending on my load and the OAT with EGT's in the 1380 range.

[@FlyWirescottperdue]

Just Me- thanks for watching and asking the question. The whole exercise was to find Lean of Peak... NOT Rich of Peak. I was saying there are two. ways to do it... but once you know all you really need to do is pull directly to the fuel flow that works. Our engines breathe a lot differently, the 550 is better at being an air machine than the 520 is.

[@markg4459]

Very useful video. Thanks. Impressive #s esp your low CHTs.

[@FlyWirescottperdue]

Glad it was helpful!

[@mannypuerta5086]

I do the same in the 185 with GAMI’s installed. WOTLOPSOP all the time. Just installed a GAD-13 for the G5’s, so I now have TAS, OAT and wind. Great feature.

[@FlyWirescottperdue]

I've been thinking of G5s for the F33C.

[@neatstuff8200]

What about leaning for takeoff at high altitude Scott? I don't remember ever being taught or teaching much about that as I flew mostly out of a sea-level airport. But I found out later that I had been doing it wrong and at higher altitude like Aspen for instance you want all the power you can get.

[@FlyWirescottperdue]

Which means you have to lean for Density Altitude in normally aspirated airplanes.

[@gwndds]

Scott, does your leaning procedure show much difference in fuel flow depending on altitude you are flying?

[@FlyWirescottperdue]

Not really, during descent the FF decreases of course with MP.

[@ryanaquino2015]

Is it normal to see CHTs that low? I’m guessing you have an Io-550 with d Shannon baffles. Were the cowl flaps open?

[@FlyWirescottperdue]

Ryan- The baffles I have are GAMIs and yes, thats pretty normal. Excellent system! I close the cowl flaps when I level off.

[@mynickels]

My first big pull: "too big, too big"!!!!

[@dirtcurt1]

So has "lean of peak" come home to roost with the latest service letter from Continental? Time will tell.

[@apfelsnutz]

Nice video, straight ahead leaning... but just a tad to rich for me. Do you have GAMI s ?

[@FlyWirescottperdue]

Oh yes I do. And I was lean of peak. I just like to go as fast as I can LOP.

[@apfelsnutz]

@@FlyWirescottperdue Great ! I fly a Navion 225-4 and fly at about 10 gal. hr. , but not as fast...LOL ! WOT is the hot ticket ! The 225 will fly all day at 2500 and about 24 inches, depending on altitude, which for me is usually over 6000ft. I live at L00 in the Mojave desert so mountains all around. Thanks again for the video... Ron

[@georgewoodland1766]

At 14.6 gpa are you rich or lean of peak? If so how much below peak or above peak?

[@FlyWirescottperdue]

LOP. Doesn’t really matter if the CHTs are cool.

[@kjackles]

New sub here Scott! I am enjoying your channel. I assume that you know your engine quite well. Sorry to be contrary but… for those who are still learning or operating a new to them engine, this method is sub optimal. If one wants to set power by fuel flow(ff) it is prudent to verify LOP EGT on richest cylinder and/or ROP EGT on leanest cylinder and note those FF numbers. Unless I missed something, you were using ROP "lean find" (which is leanest cyl) to verify peak EGT. That tells you nothing about settings of the richer cylinders. They may or may not be at a desirable power setting. Many stock injected engines run poorly as the richest cylinder approaches peak EGT. This would go undiscovered using peak EGT on the richest cyl . The method depicted is fine if one knows they have conforming F/A ratios across all cylinders. While one can use CHT as a proxy for mixture setting it is heavily influenced by DA and OAT (Cruise CHTs in August should differ from Feb). Also, CHT is a slow and imprecise proxy for combustion event/mixture analysis. CHT can take minutes to reveal what EGT will show in seconds.

[@FlyWirescottperdue]

Kjackels thanks for watching! Honestly, I think you are getting wrapped around the axel on this. EGT is a trend reference, not a control reference. CHT is controlling... and yes it takes a bit of time for CHT to stabilize. Don't forget that CHT is NOT a proxy, it is a direct indicator of stress on your cylinders. FF is what we use to control CHTs. I use the LOP feature to find what FF works and once I have that I just pull the Mixture right to my chosen FF. I don't reinvent it over and over again. I monitor my CHTs to see what is happening and flex accordingly. At higher altitudes, where your HP percentage is low on a NA engine, you may want to fly closer to Peak EGT to extract the max power out of the airplane... as long as your CHTs are under control. A well setup engine can run LOP in a fairly broad range... depending on whether you want to go slow/eco or fast/eco. No engine monitor, no LOP.... for me. I never try to run LOP without a good engine monitor with Fuel Flow and balanced Fuel Injectors like GAMIs. I do run a carbureted engine, with a little carb heat, LOP.... with a good engine monitor.

[@kjackles]

@@FlyWirescottperdue Not wrapped around anything. It's a difference in philosophy I guess. CHT is a direct indicator of the temperature of the probe. A mixture setting that yields a CHT 370° at an OAT of 85° does not have the same margins as that same CHT at an OAT of 5°? To my way of thinking (when setting power), CHT is a proxy for Internal Cylinder Pressure. Where I live, it is entirely possible in the winter to set an absolutely abusive power setting while holding acceptable CHTs. As mentioned earlier, the CHT reading only tells you the temp of the probe. The temp over the barrel can vary a great deal. Not to worry though, most of the GA birds I have seen have perfectly maintained baffle seals and are certainly not prone to hot spots...;-) Anyway, I am enjoying your channel. If I am going to pick aviation nits I should probably start one of my own!

[@FlyWirescottperdue]

@@kjackles Think of it this way... what is the purpose of this whole procedure? I submit that what we are trying to accomplish by running the engine LOP is to operate the engine cleanly (contaminates) and economically. The ICPs indeed have a direct role in heat transfer (and burned valves etc). But since our timing is fixed (for now, until GAMI certifies the PRISM system) all we have to control the ICP is FF. It is generally accepted now that keeping the CHTs below 400F prevents the alloys from going plastic, reducing choke to zero and weakening the material strength. That's why a lot of folks use 380F as an alert temp... to take some action to reduce CHT. Hopefully, the baffles and other items are already in tip/top shape. The ICPs are responsible for the heat, but in fact what we are trying to control for is the CHT. Letting the CHTs run hot for a prolonged period results in premature Cylinder replacement. Of course there are variations in temperatures at different points around the cylinder... and that is why it is a good idea to use a conservative alert Temperature like 380F. That is what I mean by stating that CHTs are controlling. If you keep the CHT temps within an acceptable range then you are more likely to avoid early MX issues. Hopefully. The engine monitors available today are wonderful compared to what we had a few short years ago. It's not perfect, but more than adequate to successfully operate the engine without too much fiddling. If the CHTs are below 380F, then I submit that the ICP is not inordinate. Of course we are talking normally aspirated engines here. When you mention margins at various temperatures... I think detonation. Are you referring to that or temperatures? If it is detonation... then your CHTs will rapidly increase and when they pass 380F, hopefully you react and change the equation.

[@kjackles]

@@FlyWirescottperdue Thanks again for your thoughts Scott. I am referring to both detonation and temp margins. The reality is that most N/A GA engines need to be severely abused to approach even light detonation. The certification margins are very conservative. However, I was also told temp margins are a concern. I have never attended APS but over the years have enjoyed corresponding with some of there knowledgeable folks that happened to instruct for them. One of those gentleman (recently gone west unfortunately) admonished me against using CHT as the sole metric for power settings. One of his rationals was the variation in temps across the cylinder when in the test cell. This was many years ago and perhaps the thinking has changed since. I can say anecdotally that my IO360 will tolerate almost any mixture setting with acceptable CHTs readings on high pressure days with the OAT

[@FlyWirescottperdue]

@@kjackles KJ- You are probably talking about Walter Atkinson, we were friends since the early 90's. . All the data he was referring to was obtained in GAMI's Engine Dyno at Ada, Ok. He was probably getting in the weeds and it doesn't really have much effect. The difference is not great and metal conducts heat very well, so temp variations are not a huge concern in a well maintained engine. If you use CHT as controlling then you will be doing the best you can.

[@deani2431]

I get the thrust of this, but the explanation is confusing (ie: you are seeking LOP but set the JPI for ROP)

[@FlyWirescottperdue]

I don't change the modes of the JPI... its a waste of time.

[@georgewoodland1766]

Gph

[@joeyg7458]

the fuel flow method is the wrong way because it is subject to temp and density altitude…

[@FlyWirescottperdue]

And you justify that how?