Wide open Throttle leaned to lower RPM

Tom-D

Tom-D

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Tom-D
From the ezchronicles.com

http://www.ezchronicles.com/?p=30

Quote
The trip up to Wisconsin was flown at LOP, lean of peak, throttle wide open and RPM aggressively reduced with mixture. This is now fairly routine after the last two years of testing and tweaking toward optimum efficiency. During that time only one cruise flight was flown at higher power settings, coming back after a hundred dollar fajita, described in the EZ Chron What Flying is Really About. On that trip things were pretty exciting outside and not much time was spent inside the cockpit figuring data. Otherwise, all of the recent flights had the throttle full open with aggressive leaning to low rpms, between 2200 and 2000. So until now I had not looked at max cruise.

You can notice lots of folks talking LOP. Several of the local spam can drivers say they have been doing it for years. Cool. Listening further, it seems they might be talking about something a little different. They are in fact “leaning lean of peak”. However they are first setting RPM with throttle, the normal practice. But there is a difference in flying with the rpm set with throttle and then leaning LOP, versus putting the throttle wide open and then reducing rpm to 2000 with mixture. Not earth shattering. But interestingly preferable if one can do it. Probably could use a better term for the more aggressive leaning practice.

end quote

Thoughts ??
 
I'm pretty sure my thoughts on the matter are relatively clear to you. I don't use it to bring back RPM obviously but I do use the red handles to reduce power WOT.
 
This blog or what ever it is is "like putting the cart before the horse". Running LOP should be done under strick guildines, on a properly equiped aircraft engine, following sound advice from experts.

JMHO
 
Geico266 said:
This blog or what ever it is is "like putting the cart before the horse". Running LOP should be done under strick guildines, on a properly equiped aircraft engine, following sound advice from experts.

JMHO
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Running LOP was done by Charles Lindberg with no instrumentation for it, pretty much every plane during WWII was subject to LOP operations.
 
I always just figgured that power enrichment exists for a reason but what do i know?
 
Henning said:
Running LOP was done by Charles Lindberg with no instrumentation for it, pretty much every plane during WWII was subject to LOP operations.
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That is my point, it was done under strict procedures and conditions, and I doubt if they referred to a blogger. ;)
 
Geico266 said:
That is my point, it was done under strict procedures and conditions, and I doubt if they referred to a blogger. ;)
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Charles Lindberg wrote the procedure by the seat of his pants and results in operations as a long distance air mail pilot. This was simply a man listening to machines and observing the results. He went on to teach aviators flying with Chenault in Burma as well as with the 8th Air Force. He went out and met with squadrons and taught them how to do it by flying missions abroad and at home with them in what ever plane they were flying and showing them how it's done, how to get that extra range to get the bombers deep to the south east industrial regions and how to get fighter cover further along with them. These men then take the same information and disseminate it among other squadrons. That's basically how it was done.

I had the good fortune of flying a good few hours with some of the last active ones when I was just starting out. I wish I'd of flown with my Uncle Lloyd more, but he did give me my first stick and first trick at the helm when I was 3 or 4. I have heard a lot of his stories though, there's a lot of good meat in them.
When I worked for Ward Foley I was at the right place at the right time for flying. Sometimes I wish I'd of stayed another year.
 
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Skylane81E said:
I always just figgured that power enrichment exists for a reason but what do i know?
Click to expand...
It exists for two reasons. Being somewhat rich of stoichiometric increases power at the same airflow by allowing the preferential combustion of Hydrogen which generates more heat than the Carbon (which is blown out the exhaust as CO and as unburned HC). Also, at high power settings the extra fuel helps keep temperatures down. But, all this is at the expense of fuel consumption - ****ing fuel out the exhaust is not a very efficient thing to do.

On the other hand, reducing power by reducing fuel and running with excess air reduces the fuel required to generate power at the crankshaft for two reasons. One is that opening the throttle further (to WOT in this case) increases the manifold pressure and reduces the pumping work during the exhaust / intake strokes - reducing the work required to pump the air reduces losses and wasted fuel energy. Second, running with excess air reduces the heat losses to the cylinder walls during the expansion stroke, again improving the utilization of the fuel energy.

Of course, there can be too much of a good thing. A very lean mixture is difficult to ignite and burns slowly. If the mixture does not ignite (misfire) you are once again sending unburned fuel out the exhaust. Or if you get poor ignition, that results in a "slow burn" in which the fuel burns too late in the expansion stroke to extract all the combustion energy. And, as you go leaner, the optimal spark timing changes - in the typical aircraft engine the fixed timing will limit the benifits of lean combustion when you get to very lean mixtures.

Now, some of the observed benefit from running lean comes from the way that it is typically done. A pilot sets a manifold pressure / rpm and then pulls on the red knob. This does two things. First, as you go lean, you do improve the fuel efficiency as noted above. And, second, you reduce the actual power delivered to the crankshaft and reduce the aircraft speed somewhat which also reduces you fuel consumption at the expense of travel time. But it does provide more efficient operation than simply closing the throttle a little to get to the same delivered crankshaft power for the reasons outlined above.

Bottom line is running a higher air flow with a lean mixture will be more efficient than closing the throttle and running a richer mixture. But, in aircraft operations at high altitudes, the air available is, of course, limited. And, a lot of the touted benefits from lean come from operating at reduced power at more efficient air speeds.
 
Tom-D said:
Several of the local spam can drivers say they have been doing it for years. Cool.
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I've been flying my "spam can" that way for a couple years. Throttle goes wide open on takeoff roll and I keep it rich for the climb, throttle stays full open and I reduce RPM with LOP mixture for cruise. Reduce it even more for descent until about 5000' MSL then go back to ROP and throttle reduction to control power.

Of course, I have a matched set of injectors and a fully instrumented engine - I would not recommend doing this without the right equipment and knowledge of what it's doing. I've got just over 600 hours on my IO360 doing this and it's happy as can be. I also lean aggressively on the ground and have not had a single fouled plug in those hours.
 
We don't know what fuel system the EZ flyer has.

What happens in a carb at WOT that does not happen at any other time?
 
Tom-D said:
What happens in a carb at WOT that does not happen at any other time?
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The throttle plate is approximately lined up with the axis of the throttle bore.

This results in two things. Maximum air flow with minimum pressure drop. And, the fuel droplets do not tend to get deflected to one side of the intake manifold.
 
Tom-D said:
We don't know what fuel system the EZ flyer has.

What happens in a carb at WOT that does not happen at any other time?
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Depends if it has some type of 'power valve'/enrichment valve.
 
airguy said:
Of course, I have a matched set of injectors and a fully instrumented engine - I would not recommend doing this without the right equipment and knowledge of what it's doing. I've got just over 600 hours on my IO360 doing this and it's happy as can be. I also lean aggressively on the ground and have not had a single fouled plug in those hours.
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Unless you are Henning or Lindburg. :rofl: Just yanking your chain Henning! :D

Seriously, I have not heard of the WOT lean to RPM technique, but I certainly don't know every LOP operation. From what I do know I would caution against running WOT LOP below 7500' MSL. I run LOP alot below 75% power at all altitudes. Of course above 7500' you are at approx 75% power or below and LOP it easy in a properly set up engine.
 
Geico266 said:
Unless you are Henning or Lindburg. :rofl: Just yanking your chain Henning! :D

Seriously, I have not heard of the WOT lean to RPM technique, but I certainly don't know every LOP operation. From what I do know I would caution against running WOT LOP below 7500' MSL. I run LOP alot below 75% power at all altitudes. Of course above 7500' you are at approx 75% power or below and LOP it easy in a properly set up engine.
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in any natural aspirated engine you can use this method at any altitude with no damage to your engine. Removing fuel from the engine will not harm it.
 
Capt. Geoffrey Thorpe said:
The throttle plate is approximately lined up with the axis of the throttle bore.

This results in two things. Maximum air flow with minimum pressure drop. And, the fuel droplets do not tend to get deflected to one side of the intake manifold.
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this is true, which results in _________ ?
 
Geico266 said:
This blog or what ever it is is "like putting the cart before the horse". Running LOP should be done under strick guildines, on a properly equiped aircraft engine, following sound advice from experts.

JMHO
Click to expand...

Running LOP has been done for years by every pilot that followed the lean to stutter and then enrichen to smooth technique. That places the mixture just a bit richer than it would quit, that is about .05 parts per million on the chart I linked above. on age 2 of the page.
 
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Tom-D said:
in any natural aspirated engine you can use this method at any altitude with no damage to your engine. Removing fuel from the engine will not harm it.
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I am not disagreeing with you, and this makes sense, but what about detonition above 75% power? :confused:
 
Tom-D said:
Any stock engine he would be running in a EZ would have a version of the Marvel Schibler MA3

http://www.kellyaerospace.com/articles/Accessory_AMT.pdf
note the horse power graph on page 2.

there is no power enrichment valve in the MA 3
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Then nothing except the expected reduction in manifold vacuum.

HOWEVER! I will add this about LOP with a carb, you may find you can smooth a bit onset lean roughness by altering the throttle plate some near full open as it causes the turbulence and airflow in the plenum which can help even distribution. Then you can go even further reducing fuel flow smoothly by cracking carb heat, but you have to be careful about detonation, (low/no risk at typical optimum cruise altitudes for a NA plane) altitude.
 
Geico266 said:
I am not disagreeing with you, and this makes sense, but what about detonition above 75% power? :confused:
Click to expand...

you can't get above 75% leaned this way. You can only get detonation when you have an abundant supply of fuel. and a slow moving piston that will build pressures above designed parameters.
 
Geico266 said:
I am not disagreeing with you, and this makes sense, but what about detonition above 75% power? :confused:
Click to expand...

How do you make 75% power with no fuel? Look at your airspeed to see what your power is, not your engine instruments.
 
Maybe I should ask the question in a different way.

Define " on the Step "
 
Leaning to rough and then enriching to smoothe is how I learned it and then had it confirmed to me by a lycoming guy... It's what I do and teach. I have engine instruments for CHTs and EGTs in the decathlon.. Seems fine

But, I start out at 4500 feet field elevation too
 
What I found most funny about pilots using that term is that by its definition whenever a plane is flying, it is 'On the Step', ie a body is being dynamically supported by forcing it through a fluid such that it lifts above its natural buoyant level in that fluid.
 
I read somewhere at lower altitudes you can set the throttle to a 75% power setting with best power mixture, then lean the RPM back to the desired power setting. Above 8000 ft leave it wide open and lean back to whatever power setting you want. I think that was in a Piper POH

Most everywhere I have read that you basically cannot hurt the engine with the mixture knob if it is producing below 75% power.

Cessna recommends that you lean the 152 (at 75% or less power) until you see an RPM drop of 25-50 rpm for the best economy setting. Thoughts?
 
The more time I've spent flying aircraft with a JPI and probes on every cylinder, the more I realize, it's not rocket science. If you lean to max power it'll be hot as hell. If you lean a bit more everything cools right off.

I generally look at the exhaust gas temperature as I'm going through about 800 AGL. Then I keep leaning to maintain that same EGT. It keeps things rich enough but not ridiculously rich. Once I get up to cruise altitude I quickly lean until it's rough and then I enrichen to where it's smoother. It's almost always LOP and all the available instrumentation always indicates things are happy. If you richen a bit more yet then the temps start to go crazy. This is where people bite themselves in the ass.
 
And some of us stuck behind O470s with crappy induction systems can't take the roughness that going much LOP causes.

Now with altitude the throttle does stay fwd.
 
jesse said:
The more time I've spent flying aircraft with a JPI and probes on every cylinder, the more I realize, it's not rocket science. If you lean to max power it'll be hot as hell. If you lean a bit more everything cools right off.
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I believe you, but why do many POH's recommend you lean to peak power above 3000ft with the throttle wide open?
 
dell30rb said:
I believe you, but why do many POH's recommend you lean to peak power above 3000ft with the throttle wide open?
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Because the POH's were written by the same people that will sell you your next engine.

jesse said:
I generally look at the exhaust gas temperature as I'm going through about 800 AGL. Then I keep leaning to maintain that same EGT. It keeps things rich enough but not ridiculously rich.
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I do basically that, I'll lean slightly as I climb especially if I'm going fairly high for cruise. I try to target the peak EGT I normally get on takeoff conditions but I'm also closely watching CHT's during the climb. I'll happily add another GPH to keep the CHT's happy until I level out and cooling airflow picks up, then I go WOTLOP and watch the CHTs cool down while EGTs go up. In my 172 I usually see TAS at 6000-8000 cruise stabilize at 120kts on 7.8-8.2 gph depending on OAT.
 
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Skylane81E said:
And some of us stuck behind O470s with crappy induction systems can't take the roughness that going much LOP causes.

Now with altitude the throttle does stay fwd.
Click to expand...

Right there with ya, buddy. I've tried the "cock the throttle plate" and "partial carb heat" and every possible way.

It just ain't happening on the induction system on the typical O-470 carb'd engine. Rarely, you see someone who managed to get lucky enough that it works.

It's just a huge gas burning beast, so we give 'er the gas and she's happy. If we want to operate economically, we climb. ;)

Got the latest results from Blackstone today. They said they see the added Calcium from the CamGuard (interesting... our engine will never have osteoporosis apparently. Ha.) and we must have mixed a tiny bit of AvGas into our sample. Oops. Probably in the drain tube.

But otherwise, as they put it... "Your O-470 is showing very little wear at [950 or so] SMOH, and is ready to go get $100 hamburgers."

Haha. I love the little personal notes they add to their analysis comments.
 
Skylane81E said:
And some of us stuck behind O470s with crappy induction systems can't take the roughness that going much LOP causes.

Now with altitude the throttle does stay fwd.
Click to expand...

It will get very smooth if you keep pulling.
 
Henning said:
Depends if it has some type of 'power valve'/enrichment valve.
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The enrichment schedule doesn't really matter if you're controlling power by limiting fuel other than the potential need to pull the red knob further out for the desired fuel flow and mixture.
 
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