CSOBeech - Lean of Peak Beechcraft Engine Operations

Green of Peak Engine Ops (formerly LOP) Saves Gas & Engines!

Confused about Lean of Peak (LOP) Operations?

The folks at Advanced Pilot Seminars can teach you more about why flying your engine "Green" of Peak is the best operating decision you can possibly make for the health of your engine!

The folks at Advanced Pilot Seminars even have an on-line course that you can purchase to get yourself educated on what's really happening in the internal combustion event. People say it's like "Myth Busters" for the operation of the piston aircraft engine!

Check out this LOP PowerPoint Presentation and this EGT Leaning Presentation created by Advanced Pilot Seminars for a good grounding in why this is the most efficient and effective operating technique for your air cooled horizontally opposed aircraft engine.

Check out the GAMI injectors page HERE

Check out this Engine Management Article written by Peter Holt

Below are pics of my spark plugs after 200 hours of Lean of Peak Operations. No self respecting CSOB wants to break or damage anything expensive and that's a big part of why I run my B55 Baron LOP. The folks running ROP are just kidding themselves and running their engines at the highest internal combustion pressures possible (and also the highest CHTs).

Removing the fuel past peak EGT does not melt cylinders, how the heck can removing the source of combustion energy do anything but remove the intensity of the fire! Your CHTs will be lower and that's a good thing for your cylinders.

Baron Owner and IA Stuart S. offers the following simplified explanation of LOP operations:

"The combustion event begins with the spark and the peak pressure occurs milliseconds later. LOP adds a bit of time to the event. The higher the RPM, the further past TDC that the peak internal combustion pressure occurs (ICP), resulting in less CHT."

This is another good reason to climb to your cruise altitude at maximum continuous RPM!

LOP is so easy a Caveman could do it <grins> See John Deakin's LOP guidance HERE

Here's the rough math on my LOP operations:

Give up ~3% of airspeed and receive about ~16% better range or fuel economy!

To me, that's a great deal. That's like getting 16 gallons of free fuel for every 100 gallons you burn! Or, on a massive headwind cross country trip not having to make that fuel stop. PLUS all the other advantages of lean and clean burning combustion operations inside your engine.

Here are pics of my Exhaust stacks after a 5 hour LOP flight from KATW to KDTO

Left Engine IO-470L Right Engine IO-470L

Here is their infamous "Red Box" mixture vs. altitude diagram. Their recommendation is to avoid operations in the "Red Box". Note that above 8,000' the Red Box does not exist! You cannot hurt a normally aspirated engine with your mixture settings at altitudes above 8,000'.

Still confused? Click the link above for their seminar or on-line course.

Learn to use this KNOB!

The Dangerous Red Box

Just where is that "red box" John Deakin keeps talking about? Some rough numbers, good (that is to say, BAD) for most of these engines -- these are "no fly zones," DO NOT set the mixture between them:

Red Box = No Fly Zone

At and below about 60% power, there is no red box. Put the mixture wherever you want it.

At about 65% power or so, 100ºF ROP to Peak.

At about 70%, 125ºF ROP to 25ºF LOP.

At about 75%, 180ºF ROP to 40ºF LOP.

At about 80%, 200ºF ROP to 60ºF LOP.

All those numbers are approximate! Please don't start splitting hairs, here!

You probably don't want to run your engine between those mixture settings. If you do, you are running very high peak pressures inside the combustion chambers, and that peak pressure is occurring too close to top dead center.

There's a chance you read too fast, and missed this very important point, so let me put it another way:

Outside the Box

At 65% power, use richer than 100 ROP, or leaner than peak EGT.

At 70%, use richer than 125ºF ROP, or leaner than 25ºF LOP.

At 75%, use richer than 180ºF ROP, or leaner than 40ºF LOP.

At 80%, use richer than 200ºF ROP, or leaner than 60ºF LOP.

On most of these engines, with a properly set mixture at full rich, at sea level, full power, the EGT ends up at about 250ºF ROP, with some as high as 300ºF ROP and temps of 1250-1300F on most EGT monitoring equipment.

Lean of Peak Operation For IO-550						Lean of Peak Operation For IO-520
GPH	HP	GPH	HP	GPH	HP	GPH	HP	GPH	HP	GPH	HP
10.0	50%	13.0	65%	16.0	79%	10.0	52%	13.0	68%	16.0	84%
10.2	51%	13.2	66%	16.2	80%	10.2	53%	13.2	69%	16.2	85%
10.4	52%	13.4	67%	16.4	81%	10.4	54%	13.4	70%	16.4	86%
10.6	53%	13.6	68%	16.6	82%	10.6	55%	13.6	71%	16.6	87%
10.8	54%	13.8	69%	16.8	83%	10.8	56%	13.8	72%	16.8	88%
11.0	55%	14.0	70%	17.0	84%	11.0	58%	14.0	73%	17.0	89%
11.2	56%	14.2	71%	17.2	85%	11.2	59%	14.2	74%	17.2	90%
11.4	57%	14.4	72%	17.4	86%	11.4	60%	14.4	75%	17.4	91%
11.6	58%	14.6	73%	17.6	87%	11.6	61%	14.6	76%	17.6	92%
11.8	59%	14.8	74%	17.8	88%	11.8	62%	14.8	77%	17.8	93%
12.0	60%	15.0	75%	18.0	89%	12.0	63%	15.0	78%	18.0	94%
12.2	61%	15.2	75%	18.2	90%	12.2	64%	15.2	79%	18.2	95%
12.4	62%	15.4	76%	18.4	91%	12.4	65%	15.4	81%	18.4	96%
12.6	63%	15.6	77%	18.6	92%	12.6	66%	15.6	82%	18.6	97%
12.8	64%	15.8	78%	18.8	93%	12.8	67%	15.8	83%	18.8	98%

Conversion Factor		14.9				Conversion Factor		14.9
Max HP		300				Max HP		285

	ROP Percent Horsepower Chart
	RPM
MP	2700	2600	2500	2400	2300	2200
29	100.0	97.5	95.0	92.5	90.0	87.5
28	96.5	94.0	91.5	89.0	86.5	84.0
27	93.0	90.5	88.0	85.5	83.0	80.5
26	89.5	87.0	84.5	82.0	79.5	77.0
25	86.0	83.5	81.0	78.5	76.0	73.5
24	82.5	80.0	77.5	75.0	72.5	70.0
23	79.0	76.5	74.0	71.5	69.0	66.5
22	75.5	73.0	70.5	68.0	65.5	63.0
21	72.0	69.5	67.0	64.5	62.0	59.5
20	68.5	66.0	63.5	61.0	58.5	56.0

Above charts courtesy of Beech Lister Elliott S.

Here's what Lindbergh taught P38 Lightning pilots during WWII

Instructors warned WWII P-38 pilots that running their fuel mixture lean would cause their engines to melt down in mid-air. Charles Lindbergh told them to do it anyway.

His legendary 1927 solo flight across the Atlantic didn’t just make him famous; it forced him to become one of the world's foremost experts in squeezing every possible mile out of an aircraft engine. When he arrived in the Pacific Theater during World War II as a civilian technical representative, he brought this deep, practical understanding of fuel conservation to pilots flying the P-38 Lightning.

In the Pacific, distance was a deadly enemy. The twin-engine P-38 Lightning was a formidable fighter, but pilots were strictly limited by their fuel range. Standard Army Air Forces doctrine dictated running the engines in "auto-rich" during cruise to prevent the engines from overheating or suffering severe detonation.

Lindbergh knew from his Atlantic crossing and years of test flying that the standard military doctrine was overly conservative. Young fighter pilots were taught a simplified, foolproof way to operate complex machinery to prevent them from accidentally destroying their engines. Lindbergh, however, deeply understood the thermodynamic relationship between manifold pressure, engine RPM, and fuel mixture.

He confidently instructed pilots to drastically drop their engine RPM—from the standard 2,200 RPM down to around 1,600 RPM—while significantly increasing their manifold pressure to maintain airspeed. Under these specific, low-RPM conditions, the engines could be safely switched to "auto-lean" without causing detonation or overheating. The lower internal friction at reduced RPM offset the stresses of the higher manifold pressure, allowing the lean fuel mixture to burn with maximum efficiency.

By adopting Lindbergh's unorthodox engine settings, P-38 squadrons extended their combat radius by nearly 50 percent. This massive increase in range allowed fighters to escort bombers all the way to distant, heavily defended targets and strike Japanese forces that assumed they were safely out of reach. Lindbergh’s supreme confidence didn't come from a reckless disregard for the manual; it came from a profound, scientific mastery of internal combustion that the manual's authors simply hadn't trusted average pilots to execute.