Leaning Off

[fireflybob]

Simple question - do you teach your students to lean off? If not, why not?

[SNS3Guppy]

Lean off what?

[S-Works]

Yes, simple answer!!

We owe it to our students to teach them the correct method of managing all of the systems in the aircraft they fly. This includes the use of the mixture setting AND the theory behind it.

[Cows getting bigger]

Yes, always. But unfortunately our club doesn't have a leaning policy so many instructors (including the CFI) don't bother. Methinks the membership should be asking why hourly rental charges are rather volatile. :rolleyes:

Then again, we are still in denial mode believing that the only aircraft suitable for training must have Cessna written on the aircraft.

[RTN11]

Of the 4 schools I have flown with, only one seems to teach the use of mixture correctly as a standard practice.


One school says the reason they don't (and in fact ask me not to) is that incorrect use of the mixture can do more harm than good, particularly if flying too lean. So they think it's better in the long run for the engine to run fully rich all the time.

Another reason I've had is that during a training flight, you rarely get high enough to warrent leaning the aircraft. Some POH do state not to lean below 5000'. How often do you take students higher than that, now that spinning isn't a requirement.

I myself was not taught to lean correctly until i did my FI rating. I had some idea, and had read the book, but an instructor had never mentioned it.

['India-Mike]

I do it as part of 4(ii), with the caveat that I'm teaching them a technique only - should be done in practise with reference to FM/POH.

But I'm still learning so content to take advice to the contrary

[Intercepted]

Some POH do state not to lean below 5000'

Which has turned out to be wrong in most cases (based on pilot experience).

Some of us lean and save avgas succesfully and without engine damage at 2500' despite POH statements.

The POH is something every pilot should respect, BUT it's not a bible.

[Cows getting bigger]

Just to add - I encourage pilots to aggressively lean the mixture on the ground whilst they are doing the plethora of checks the club SOPs present them with. :bored:

[SNS3Guppy]

Perhaps "leaning off" is a way of saying "leaning." Got it.

The POH is something every pilot should respect, BUT it's not a bible.


Actually, so far as the aircraft goes, it is. It's part of the legal certification of the airplane, and the airplane is unairworthy without it. The airplane is also unairworthy unless it is operated in accordance with the Aircraft Handbook, Pilot Operating Handbook, Aircraft Flight Manual, or whatever particular document is assigned that aircraft.

One must be careful, however, to differentiate between guidelines and limitations.

Some manufacturers recommend leaning above a particular altitude, not because the aircraft should not be leaned below that altitude, but as a way of "idiot proofing" the airplane.

Yes, improper leaning can result in damage to the engine (and ultimately the airplane and occupants). No, leaning below 3,000', 4,000', or 5,000' will not hurt the engine, airplane, or occupants. A recommendation to lean at higher altitudes is a gentle way of saying that one shouldn't lean above 75% power...or more specifically, that one can't hurt the engine when leaning below 75% power. By the time your mighty steed reaches several thousand feet, a normally aspirated (non-turbocharged, non-supercharged, non-turbocompound engine) isn't producing enough power and can't be run at a high enough power setting, to do harm.

Leaning for takeoff is necessary at higher elevation airports to protect the engine from fouling, to allow it to run cleanly, and to allow the engine to produce the most power possible for takeoff. This is safe, because one is unable to harm the engine...it won't produce enough power to cause damage.

Leaning should be accomplished per density altitude; One may very well be sitting at sea level and be able to lean with abandon, even for takeoff, due to density altitude. A hot summer day at 100 degrees F (37 deg C), one is already at a 3,400' density altitude on a standard-altimeter day with high humidity...one is very close to being able to lean as though one were flying at 3,000 MSL on an ISA standard day.

Another reason I've had is that during a training flight, you rarely get high enough to warrent leaning the aircraft. Some POH do state not to lean below 5000'. How often do you take students higher than that, now that spinning isn't a requirement.


This may or may not be true for aircraft based at a sea level airport, but as we've just ,seen, one may easily be at an altitude where leaning is important, before we take off...at sea level...based on density altitude.

I learned to fly light airplanes at field density altitudes of 7,000' to 10,000, where leaning for takeoff was always necessary. Even if one is based at sea level, leaning for takeoff may be advisable, or necessary.

Does your operating handbook specifically state that one should NOT lean below 5,000'?

Then again, we are still in denial mode believing that the only aircraft suitable for training must have Cessna written on the aircraft.


What does that mean, and how does it relate in any way to leaning an airplane engine?

Leaning a piston aircraft engine is basic to operating the engine. There is absolutely no excuse for failure to teach a student to properly lean the engine.

One school says the reason they don't (and in fact ask me not to) is that incorrect use of the mixture can do more harm than good, particularly if flying too lean. So they think it's better in the long run for the engine to run fully rich all the time.



This is nonsensical. The same logic would dictate that one never take off, because one might crash. It's better for all concerned to stay in the ground, then.

Ridiculous.

A student should be taught proper ground operation of the mixture, and proper use in flight, every bit as much as proper operation of carburetor heat, fuel management, and emergency procedures.

[P.Pilcher]

A number of years ago a pilot flying a C172 with 3 pax got his fuel sums a little wrong and realised that he was getting somewhat low on his return leg. He therefore slowed down to what he thought was the speed for maximum range and leaned out his engine as much as he could (2000'). He made it home - just and the following day the aircraft was found to be unable to develop its normal static full power R.P.M. The licensed engineer arrived and discovered that five out of six cylinders were cracked due to being overheated. An expensive bill for the owners!

P.P.

[fireflybob]

A number of years ago a pilot flying a C172 with 3 pax got his fuel sums a little wrong and realised that he was getting somewhat low on his return leg. He therefore slowed down to what he thought was the speed for maximum range and leaned out his engine as much as he could (2000'). He made it home - just and the following day the aircraft was found to be unable to develop its normal static full power R.P.M. The licensed engineer arrived and discovered that five out of six cylinders were cracked due to being overheated. An expensive bill for the owners!

Thanks for all the replies.

P.Pilcher, thats an interesting story. So if we taught pilots to lean correctly on a regular basis, would this damage to cylinders be avoided?

Btw, on Ex 4 we teach (don't we?) the effect of the mixture control rather than how to lean off correctly?

[Tinstaafl]

Unless the exemplar pilot thought best range is at a high power (>65 to 75% and unlikely considering he reduced speed from cruise so must have reduced power from normal cruise setting) then he could lean all he wanted and do no damage to the engine. Indeed, if he reduced enough the engine would be lean of peak and run *cooler*.

More likely is that the engine had developed cracked cylinders over time but the cracks were only just found and/or the pilot in this example leaned at some power setting greater than 75% eg during climb at lower altitudes.


As for the original question: I always taught my students to lean at any altitude with 'leanable' power settings, starting from effects of controls. Usually not emphasized (although encouraged) during ab-initio stages but definitely required once navexes started.

[DFC]

I teach the method for leaning as specified in the engine manufacturer's operator's manual which is often partially copied into the AFM / POH.

If you fly with a Lycoming then this is essential reading;

http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf

I am in agreement with Cows getting bigger regarding agressiveleaning on the ground. This must be agressive to prevent full power being set with a lean setting. In this regard it is a good exercise to taxi the aircraft using the mixture to adjust the RPM (fixed prop)while also maintaining a smooth operation.

Very few pilots will have ever read the Engine Operating Manual for their aircraft. This is the first big mistake.

The second one is that few if any schools ask that the aircraft is operated at a particular power setting in the cruise. They frequently ask that the aircraft is cruised at 2400 RPM (fixed pitch prop) or 23" / 2300 RPM (VP prop) and ignore the fact that the power output at those figures will vary from both day to day and from one altitude to the next.

Lycoming recomends that the engines are operated at 65% or less and give excellent instructions on how to lean for both Best Power and Best Economy. The AFM/POH will specify fuel flow for various cruise (pressure) altitudes at 65% power with either best economy or best power leaning.

Unfortunately, if you ask an instructor what RPM they are going to use to get 65% power at 3000ft QNH 993 and ISA -10 they will give you a very blank look. They simply use 2400RPM but don't know what that gives and therefore have no idea of what the fuel consumption should be.


A number of years ago a pilot flying a C172 with 3 pax got his fuel sums a little wrong and realised that he was getting somewhat low on his return leg. He therefore slowed down to what he thought was the speed for maximum range and leaned out his engine as much as he could (2000'). He made it home - just and the following day the aircraft was found to be unable to develop its normal static full power R.P.M. The licensed engineer arrived and discovered that five out of six cylinders were cracked due to being overheated. An expensive bill for the owners!



Can't comment on the Continental powered 172 - would have to look at the continental engine manual. However, if it was the bog standard Lycoming 4 cylinder version that was in use as above, Lycoming would clearly refer you to their publication above which dismisses the posibility of leaning being a cause of such damage at low power settings.

Such damage is more likely to be caused by shock cooling and was probably already there prior to the flight and the extra fuel consumption being a good possible indication.

I can tell you from experience that pilots do damage club engines by excessive leaning. They hire the aircraft at £x per hour (take-off to landing + 10 minutes) including whatever fuel they happen to burn. What they do is fly at very high power settings to reduce the flight time (on which they are billed) as much as possible and then lean the mixture to prevent the excessive fuel burn being noticed. Since most clubs don't have that accurate a fuel burn figure they get away with it. The engines don't meet their full life and the report from the overhaul shop cites over leaning and the school bans leaning. But people still do it anyway!!

Operate the engine in the cruise at 65% or less and Lean as per the engine manufacturer's instruction (best economy or best power) and you will a) have a long engine life and b) get very close to the published fuel burn figures if you keep accurate records.

---------------
PS

Most of the "don't lean" / "leaning will damage the engine" instructions come from training organisations. They often have stories about how they had engines damaged by excessive leaning.

They seem to ignore that on a regular basis the aircraft cruises for 10 minutes after departure and sudenly the throttle is closed, the engine idles (with a few brief demands of high power) for 5 minutes then operates at max power for 5 minutes which is followed by a brief cruise and again the throttle is suddenly closed. This is repeated several times per hour and the exercise happens daily sometimes and often more than once a week. But they blame leaning for the engine not reaching it's recommended number of hours before overhaul.

Lycoming don't design an engine for training in PFL's or Stalls or EFATO and are adamant that shock cooling is to be avoided. They even specify a maximum rate of cooling. Ignoring this is what breaks engines.

[Say again s l o w l y]

I've always taught students how to lean ON the the aircraft whilst wearing shades and to spout lines from Top Gun in order to help them pull women.

Or is that not what you are asking?

If you mean do you teach them how to manage the engine properly, which includes leaning, then of course. What do you think FI's are? Incompetent morons?

[Big Pistons Forever]

Unless the exemplar pilot thought best range is at a high power (>65 to 75% and unlikely considering he reduced speed from cruise so must have reduced power from normal cruise setting) then he could lean all he wanted and do no damage to the engine. Indeed, if he reduced enough the engine would be lean of peak and run *cooler*.

More likely is that the engine had developed cracked cylinders over time but the cracks were only just found and/or the pilot in this example leaned at some power setting greater than 75% eg during climb at lower altitudes.


As for the original question: I always taught my students to lean at any altitude with 'leanable' power settings, starting from effects of controls. Usually not emphasized (although encouraged) during ab-initio stages but definitely required once navexes started.

I also think it was highly unlikely that the actions of the pilot in the quoted example damaged the engine. If he was flying at best range than the power setting would have been in the range of 45 %. At this power setting it is virtually impossible to cause engine damage by overleaning. And if an attempt is made to run the engine at high power settings with out first enrichening the mixture the engine will simply quit.

Engine damage in training aircraft due to miss handling comes in two varieties.

1) Cracked cylinders due to shock cooling. This occurs when the pilot rapidly reduces power from high power settings to idle or very low power settings, particularly on cold days. It is exacerbated if a prolonged descent is subsequently made at higher airspeeds and, especially bad if followed by suddenly going to a high power setting. Unfortunately a bit of this kind of abuse is necessary to carry out some training exercises, particularly the practice forced approach manoevre.

2) Burnt cylinders due to overheating is usually cause by long climbs at full power at low airspeeds and on hot days. Since most training aircraft do not have cylinder temperature guages there will be no immediate indication of this condition allthough the oil temp will provided a lagging indicator.

However there is no reason training aircraft have to suffer these problems if some basic good operating practices are taught. These include

1) Let the engine warm up. Runup (and especially takeoff) power should only be applied when the oil temp is in the green arc.

2) Make all (non emergency) throttle movements slow and deleberate.

3) After solo, drill into the students that the throttle and mixture control are connected. Except for the part of the flight immediately after takeoff, and after the prelanding (or HASEL)check has been carried out, all power changes start with verifying the position of the mixture control.

4) When carrying out PFL's, if possible start with a lower than normal cruise power setting and avoid back to back approaches. Allow a few minutes for the engine temps to stabilize before going into the second PFL. After the first PFL I take control, establish a low power setting, and use this time to debrief the student.

5) Point out to the student what is "normal" oil temp and oil pressure for the conditions. Make sure the student is actually paying attention by periodically covering the engine guages with your fingers and ask "what were they iondicating"

6) Have a formal brief for precautions required for engien operations on hot days (ground and air)

7) Teach the student how to properly lean and at the later stages of training have them lean in the cruise segment every no matter how short it is.

[DFC]

A number of years ago a pilot flying a C172 with 3 pax got his fuel sums a little wrong and realised that he was getting somewhat low on his return leg. He therefore slowed down to what he thought was the speed for maximum range and leaned out his engine as much as he could (2000').



If he was flying at best range than the power setting would have been in the range of 45 %.


Just to clarify a big point. Maximum range is obtained at the best combination of groundspeed and fuelflow.

Speaking generally;

In zero wind conditions the speed for maximum range is the best lift/drag ratio speed - best glide speed.

In a tailwind it pays to reduce towards minimum drag (minimum sink speed).

In a headwind it pays to increase speed.

The best example being having a GS of 0 when at 75% power setting in level flight. In that case increasing power will increase range.

So someone stating that they got the best [B]range[/BB] from the aircraft may in some cases indicate that they were operating at a lot more than 75% power if they were at a level that is lower than that at which the engine is unable to produce more than 75% power (normally aspirated).

[Centaurus]

He therefore slowed down to what he thought was the speed for maximum range and leaned out his engine as much as he could (2000'). He made it home - just and the following day the aircraft was found to be unable to develop its normal static full power R.P.M. The licensed engineer arrived and discovered that five out of six cylinders were cracked due to being overheated. An expensive bill for the owners!


I doubt the accuracy of the reason for the cracked cylinders. To fly a Cessna 172 with four people on board at 2000 rpm, would surely be flying for endurance (very slow speed) than range because you would be lucky to get 75 knots at that RPM leaned out.

Over time, with cylinders that have already been re-conditioned several times cracking is to be expected. If aircraft owners are so tight with their money to the extent they cut corners to avoid installing new cylinders at overhaul time, then cracking of several times over reconditioned cylinders is inevitable, and you can't blame the pilot for that - no matter how convenient for the owner.

In my experience, very few private pilots even know what minimum static RPM means - or where to find the figure in the flight manual; let alone its significance as far as engine performance is concerned. Some pilots assume (wrongly) if the take off RPM is in the green band on the RPM gauge, the engine is delivering full power.

It is quite possible that in the Cessna 172 mentioned, the aircraft had failed to attain minimum static RPM for months, and no one had noticed.

[Centaurus]

However there is no reason training aircraft have to suffer these problems if some basic good operating practices are taught. These include

1) Let the engine warm up. Runup (and especially takeoff) power should only be applied when the oil temp is in the green arc.

Not necessarily so. The Cessna 172 Skyhawk Information Manual under the sub-heading WARM-UP states: "If the engine accelerates smoothly, the airplane is ready for take-off. Since the engine is closely cowled for efficient in-flight cooling, precautions should be taken to avoiding overheating during prolonged operation on the ground. Also long periods of idling may cause fouled spark plugs".

Note there is no mention about oil temperature being in the green before run-up or take-off.

Similarly, the Cessna 152 Information Manual under WARM-UP, has this to say:
"Most of the warm-up time will have been conducted during taxi and additional warm-up before take-off should be restricted to the checklist procedures. Since the engine is closely cowled for efficient in-flight cooling, precautions should be taken to avoid overheating on the ground".

Those precautions would possibly include conducting any run-up into wind and avoidance of prolonged idling while conducting checks. That includes waiting for oil temperatures to rise when this is not required by the manufacturer.

Since neither the Cessna 172 or Cessna 152 are equipped with cylinder head temperature gauges it is difficult for the pilot to judge whether or not the engine is over-heating on the ground.

The Limitations Section of both the C172 and C152 make no mention of a requirement to have the oil temperature "in the green" before run-up or take off.

Turning now to the Normal Procedures (Cold weather operation) in both the C172 and C152 Information Manuals - where both state the following:

"During cold weather operations, no indication will be apparent on the oil temperature gauge prior to take-off if OAT are very cold. After a suitable warm-up period (2-5 minutes at 1000RPM). accelerate the engine several times to a higher engine RPM. If the engine accelerates smoothly and oil pressure remains normal, and steady, the airplane is ready for take-off".

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.

In the venerable DH 82A Tiger Moth there is no oil temperature gauge and the only engine limitation before run-up is to check the oil pressure normal at 35 PSI at 1000RPM.

Of course, the above comments apply to Cessna 152, 172 and the Tiger Moth and I do not have copies of the Information manuals of other light training types. Some aircraft with large radial engines certainly do have an engine oil temperature limitation before run-up is started. The Sea Fury has an oil temperature lower limit of 15 C as well as 120C CHT. The Convair 440 with its R2800 radials required a min oil temp of 40 C before run-up while the DC3 has an oil temp limit of 40C.

With light training types such as the C172, not only is there no operational requirement to have the engine oil temperature in the green sector before run-up but this waiting time for the oil temperature to reach the green sector often means sitting on the ground at the holding point for a long time. As Cessna warns - this can lead to overheating of the engine due to the close fitting cowls that are designed for efficient cooling while airborne.

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.

It is important for instructors to be aware of the engine operating procedures published in specific aircraft types they may instruct on. Instructors must be careful not to rely too much on their personal opinions when it comes to engine handling and where possible stick to the facts as published in the relevant flight operational documents of the aircraft manufacturer.

[Pull what]

I like the way the crew leaned the engines on night charters on the Derby Airways/British Midalnd, Canadair Argonaughts with 4 Merlin engines.

The first officer was sent back to observe the colour of the exhaust flame!

Btw, on Ex 4 we teach (don't we?) the effect of the mixture control rather than how to lean off correctly?

Bob-- the most important effect is that if you get it mixed up with the throttle it can get very quiet!

[rogerg]

I used to lean the pratts in the Beech 18, to a nice electric blue visible in the exhaust, when in the cruise.

[SNS3Guppy]

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.

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.


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.

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.


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.

[DFC]

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.



Which is more about the pressure than the temperature and hence why most aircraft manuals specify that the pressure must remain within limits as the power is increased.

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.

[SNS3Guppy]

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.

Of course it's about oil pressure...which upon start-up on a cold day, is a function of temperature.

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.

[samusi01]

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.

[IO540]

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.

[DFC]

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.



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.

[Big Pistons Forever]

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.


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 :rolleyes:...so what was the point of your post again :hmm:

[DFC]

so what was the point of your post again


I was pointing out that the ability to lean for best economy is based on the percentage power output and not on the airspeed. Therefore if you read IO540's post again one could do what they describe (base leaning on airspeed) and exceed the limits imposed by the engine manufacturer.

Yes the Airframe manufacturer will not publish a complete power curve. Have you ever seen one in the POH for 100% power??? :D

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!! :D

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?

:D

[Chuck Ellsworth]

DFC, when you were flying the DC3 could you over lean it at any power setting?

[DFC]

Maximum Rich, AutoRich, Auto Lean. Chuck

Relevance to this debate?

[Chuck Ellsworth]

Maximum Rich, AutoRich, Auto Lean. Chuck

Relevance to this debate?

We are discussing engine leaning DFC and you seem to either know so much I was wondering how you would respond to that question.

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. ?

[DFC]

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). :D

[DFC]

on all these different airplanes


Please read my profile. I come to the forum to debate. Not to advertise.

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.


I think that you need to remember the difference between knowledge and skill. You asked a knowledge based question. I answered it.

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?

[Chuck Ellsworth]

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. :ok:

[SNS3Guppy]

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]

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.

[bookworm]

DFC is correct in that airspeed has no function on when one should lean.

I think you and DFC are reading too much into IO540's initial comment. In my experience in a typically cowled light aircraft, the cooling will be adequate to permit leaning to peak EGT at 75% power at cruise speed, but doing so at 75% in the climb will cause the CHTs to become uncomfortably high. In that sense, airspeed is really quite important in deciding when and how much to lean.

[DFC]

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.