Leaning Off
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On the PB4Y conversions, we could easily lean by exhaust color at night; it was as effective as leaning by instrumentation. The short stacks on the R2600's showed the exhaust flame clearly, as did the collector. If one leaned until the flame changed from yellow to a cool blue and then leaned to adjust the length along with power, one could set the mixture fairly accurately, as evidenced by engine instrumentation.
I've replaced crankshaft seals on more than a few occasions on light airplanes when people failed to allow the oil to warm before takeoff.
It really doesn't.
Unless one is drawing air from within the cowling area (such as a carburetor heat test), one doesn't see a significant increase in induction air temperature...certainly not as a result of cylinder temperature. Further, static RPM isn't decreased by CHT during ground operations.
Well surely that proves the point beyond doubt that waiting for the oil temperature to rise into the green sector before engine run-up or take off on these aircraft types, is unnecessary; and may even be counter-productive with regards to engine overheating possibility.
Another factor not often realised by private pilots, is that as cylinder temperatures rise caused by lack of cooling airflow through the cowls on the ground, there is a steady loss of power due to hotter and less dense fuel entering each cylinder. This shows up in the minimum static RPM test if one is carried out.
Unless one is drawing air from within the cowling area (such as a carburetor heat test), one doesn't see a significant increase in induction air temperature...certainly not as a result of cylinder temperature. Further, static RPM isn't decreased by CHT during ground operations.
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I've replaced crankshaft seals on more than a few occasions on light airplanes when people failed to allow the oil to warm before takeoff.
What one must remember is that the average oil temperature gague does not start at 0 deg C. So what everyone should be aware of is what temperature is indicated when it moves off the stop.
While the aircraft FM may not specify a minimum oil temperature one can be sure that the engine manufacturer will have one.
So it is a balance. I agree that if you wait on a UK winter morning for the oil temperature to be nicely in the green then especially since most aircraft have damaged and poorly fitting baffles more damage then good is being done.
I would be more worried about the pressure.
Far to many people automatically set 1000 RPM straight away after start on a cold morning and ignore the fact that the oil pressure is above the max permitted.
The engine manufacturer's manual is essential reading.
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So it is a balance. I agree that if you wait on a UK winter morning for the oil temperature to be nicely in the green then especially since most aircraft have damaged and poorly fitting baffles more damage then good is being done.
Too much pressure means excess pressure in some locations, but inadequate lubrication in others; the oil isn't flowing properly.
Most definitely one must wait until the oil pressure is adequate, before departing, and one should wait until the oil temperature is correct, too. One is not going to damage the airplane if it's too cold to bring the oil temperature up, by idling and waiting for the temperature to rise.
More damage than good is not being done.
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Regarding oil temperature, I am with SNS3Guppy - my students are taught not to conduct runups or apply takeoff power until the oil temperature is within the green arc - 100F in this case. Some of the aircraft have turbos installed and the wastegate is, in this case, controlled by oil pressure. On these aircraft, adequate oil temperature even more critical to prevent overboosting the engine.
Regarding leaning, it is absolutely taught here. The home airport sees temps anywhere from -15C to +40C... Moreover, most of the aircraft cruise at higher altitudes - usually the lowest we fly at is 6000' MSL and leaning is required not only in cruise but even in climb, per the manufacturer's specifications. There's a nice little chart on the panel to follow for climb mixture settings.
In cruise, I teach both rich of peak and lean of peak operations but I usually recommend LOP operations - the aircraft are all lavishly equipped, including EGT and CHT for each cylinder, so running 50F LOP (or leaner) on the hottest cylinder is easily and safely done. On the aircraft with turbos, this means a considerable difference in fuel flow and therefore savings - ~35GPH ROP vs. ~16GPH LOP.
Regarding leaning, it is absolutely taught here. The home airport sees temps anywhere from -15C to +40C... Moreover, most of the aircraft cruise at higher altitudes - usually the lowest we fly at is 6000' MSL and leaning is required not only in cruise but even in climb, per the manufacturer's specifications. There's a nice little chart on the panel to follow for climb mixture settings.
In cruise, I teach both rich of peak and lean of peak operations but I usually recommend LOP operations - the aircraft are all lavishly equipped, including EGT and CHT for each cylinder, so running 50F LOP (or leaner) on the hottest cylinder is easily and safely done. On the aircraft with turbos, this means a considerable difference in fuel flow and therefore savings - ~35GPH ROP vs. ~16GPH LOP.
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I don't come here often (some will say "just as well" 
) but was not suprised to find yet another thread on leaning 
One could write for hours but let's just take the "5000ft" bit.
It is probably true that there is no need to lean below 5000ft, in the sense that the engine is not going to stop if you don't lean it.
It will be running WAY too rich at 5k but it will still run.
In fact one can climb most of the "old" engines to about 8k at full-rich before they start doing funny things.
In terms of the engine itself, however, there is no lower altitude limit on leaning. You could take off, level off at 500ft (501ft, sorry, one has to be legal) and once cruise speed is reached you can lean for peak EGT, and this will be perfectly fine in every way, so long as you are at cruise speed i.e. enough cooling airflow.
I've flown about 1k engine hours on my engine, 100% of the cruise being peak-EGT or lean of peak, and the engine was spotless at 800hrs when it was opened for the infamous Lyco crankshaft swap. This result is completely normal.
The fuel saving (MPG improvement) of peak-EGT/LOP is about 30% relative to full-rich, so anybody moaning about avgas prices ought to be aware of this.
But I wouldn't do it without some engine instrumentation, and there lies the problem.
) but was not suprised to find yet another thread on leaning One could write for hours but let's just take the "5000ft" bit.
It is probably true that there is no need to lean below 5000ft, in the sense that the engine is not going to stop if you don't lean it.
It will be running WAY too rich at 5k but it will still run.
In fact one can climb most of the "old" engines to about 8k at full-rich before they start doing funny things.
In terms of the engine itself, however, there is no lower altitude limit on leaning. You could take off, level off at 500ft (501ft, sorry, one has to be legal) and once cruise speed is reached you can lean for peak EGT, and this will be perfectly fine in every way, so long as you are at cruise speed i.e. enough cooling airflow.
I've flown about 1k engine hours on my engine, 100% of the cruise being peak-EGT or lean of peak, and the engine was spotless at 800hrs when it was opened for the infamous Lyco crankshaft swap. This result is completely normal.
The fuel saving (MPG improvement) of peak-EGT/LOP is about 30% relative to full-rich, so anybody moaning about avgas prices ought to be aware of this.
But I wouldn't do it without some engine instrumentation, and there lies the problem.
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and once cruise speed is reached you can lean for peak EGT, and this will be perfectly fine in every way, so long as you are at cruise speed i.e. enough cooling airflow.
Engine power setting is.
Following your advice - establish in the crusie at 85% power and then setting peak EGT will not be perfectly fine. It will be going against what the engine manufacturer (Lycoming) recomends.
The speed is not a factor. (Although correct technique would mean that cruise power was not set until cruise speed was reached)
Engine power setting is.
Following your advice - establish in the crusie at 85% power and then setting peak EGT will not be perfectly fine. It will be going against what the engine manufacturer (Lycoming) recomends.
Engine power setting is.
Following your advice - establish in the crusie at 85% power and then setting peak EGT will not be perfectly fine. It will be going against what the engine manufacturer (Lycoming) recomends.
DFC
Perhaps you might complete your little homily by posting a lycoming or Continental powered light aircraft POH that has charts for an 85% of full rated power, cruise power setting.......Oh wait you can't
...so what was the point of your post again 
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so what was the point of your post again
Yes the Airframe manufacturer will not publish a complete power curve. Have you ever seen one in the POH for 100% power???
I think that you will only find cruise power settings in most light AOMs.
However, if you take the time to read the Engine manufacturer's manuals you will see that they include plenty of lovely graphs showing the full range of power output / rpm / mp / altitude combinations.
You might find that many of those graphs ( I am looking at the IO540 manual now) are made up of quite straight lines!!
Finally the lycoming manual makes it 100% clear than when operating in the climb or high power settings (above 75%), the mixture should only be leaned to smooth operation ( if power reduction / roughness are experienced) and not for economy. This is also clearly noted in every flight manual.
Therefore whether 80, 85, 90, 95 or 100% BHP is used it makes no difference. Leaning for economy is not permitted regardless of speed
Does that explain the point?
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Maximum Rich, AutoRich, Auto Lean. Chuck
Relevance to this debate?
Relevance to this debate?
It would be interesting to know if these answers are from actual experience on all these different airplanes or if you are an expert on Google research.
So now that you have responded to my question lets delve a bit deeper.
Can you tell me were the A.M.C. is located in the carburetor normally used in the P&W 1830 and what engine malfunctions would compel you to suspect a faulty A.M.C. ?
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Chuck,
I open the floor to you and sit back awaiting an excellent display of your well honed instructor skills as you explain it to us in perfect detail (with diagrams).
I open the floor to you and sit back awaiting an excellent display of your well honed instructor skills as you explain it to us in perfect detail (with diagrams).
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on all these different airplanes
It would be interesting to know if these answers are from actual experience on all these different airplanes or if you are an expert on Google research.
If a 5 year old had obtained the (correct) knowledge from Google and answered your question would that have made the answer any less correct?
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Like I said DFC I read these forums for entertainment and I find plenty here.
I may not be as knowledgeable as you and may fall far short of your skill as a flight instructor but during my career I was never lacking for people who were willing to pay my fee for instructing which was quite expensive compared to the normal instructing fees.
Please read my profile. I come to the forum to debate. Not to advertise.
As I previously stated I come here for entertainment, I no longer teach flying as a means of earning a living but I do use my real name here in my profile for the simple reason I am content with my past history and see no need to pretend I am someone else, and that DFC means I feel comfortable in the knowledge that I will not be attacked by others for my lack of knowledge and the ability to transfer same to others as a teacher.
Anyhow its time to ignore each other as we really have very little in common it would seem.
You take care now and don't let my attitude upset you.
I may not be as knowledgeable as you and may fall far short of your skill as a flight instructor but during my career I was never lacking for people who were willing to pay my fee for instructing which was quite expensive compared to the normal instructing fees.
Please read my profile. I come to the forum to debate. Not to advertise.
Anyhow its time to ignore each other as we really have very little in common it would seem.
You take care now and don't let my attitude upset you.
Last edited by Chuck Ellsworth; 10th May 2010 at 14:14.
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I'm not sure why the dispute above took place, or what it really concerns, as there seems to be no actual disparity among the posts. Just some active measuring of anatomy on both sides of the fence.
DFC is correct in that airspeed has no function on when one should lean. That is, one doesn't lean because one has reached XXX value of speed in cruise. One leans for air density. DFC is also correct that one leans at lower power settings, with the caveat that one may also lean at higher power settings, depending on the system. A good light airplane example is the Cessna 210, in which one will be leaning for fuel flow as one climbs, even at climb power. (One isn't leaning for best economy, but one is leaning per instrumentation and the aircraft manual/handbook, and the engine manufacturer recommendations).
Airspeed does affect mixture, however, and has a measurable effect on manifold pressure, particularly in normally aspirated powerplants. One should adjust one's mixture with any change in altitude, temperature, power setting, or airspeed.
Mixture usage is different in pressure-carburetors that utilize autorich and autolean settings, but I don't believe there are particularly relevant to the discussion, nor do I believe a treatise on operation of a pressure carburetor will benefit most of the posters here (who will never see, or operate a pressure carburetor).
DFC is correct in that airspeed has no function on when one should lean. That is, one doesn't lean because one has reached XXX value of speed in cruise. One leans for air density. DFC is also correct that one leans at lower power settings, with the caveat that one may also lean at higher power settings, depending on the system. A good light airplane example is the Cessna 210, in which one will be leaning for fuel flow as one climbs, even at climb power. (One isn't leaning for best economy, but one is leaning per instrumentation and the aircraft manual/handbook, and the engine manufacturer recommendations).
Airspeed does affect mixture, however, and has a measurable effect on manifold pressure, particularly in normally aspirated powerplants. One should adjust one's mixture with any change in altitude, temperature, power setting, or airspeed.
Mixture usage is different in pressure-carburetors that utilize autorich and autolean settings, but I don't believe there are particularly relevant to the discussion, nor do I believe a treatise on operation of a pressure carburetor will benefit most of the posters here (who will never see, or operate a pressure carburetor).
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I was hoping that "Chuck" would have given us the benefit of his knowledge. Clearly not.
Don't forget that one does not have to go as far back as the DC3 to find compensating carbs.
Many instalations of the Rotax 912 and the Jabbiru engine use carburettors that compensate for altitude and adjust the mixture so the aircraft have no mixture control at all.
These engines are very common on the home-built and microlight fleets.
Therefore a discussion on automatic leaning could benefit almost as many as the average spam can leaning debates.
Don't forget that one does not have to go as far back as the DC3 to find compensating carbs.
Many instalations of the Rotax 912 and the Jabbiru engine use carburettors that compensate for altitude and adjust the mixture so the aircraft have no mixture control at all.
These engines are very common on the home-built and microlight fleets.
Therefore a discussion on automatic leaning could benefit almost as many as the average spam can leaning debates.
DFC is correct in that airspeed has no function on when one should lean.
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Which is why the manufacturers say that in the climb the mixture should only be leaned for smooth operation and no more than the max power setting. i.e. they specifically say not to lean for economy in the climb.
However, the basic issue remains that it is percentage power rather than airspeed that decides the ability to lean for economy.
Remember that when leaned lean of peak EGT it is running cooler. That is in no way a recomendfation to do so!!!
Having said all that one important issue often forgotten or ignored is that the instruments must be calibrated. Not many owners have their engine instruments calibrated ever never mind annually as recomended by the engine manufacturers.
However, the basic issue remains that it is percentage power rather than airspeed that decides the ability to lean for economy.
Remember that when leaned lean of peak EGT it is running cooler. That is in no way a recomendfation to do so!!!
Having said all that one important issue often forgotten or ignored is that the instruments must be calibrated. Not many owners have their engine instruments calibrated ever never mind annually as recomended by the engine manufacturers.
