Leaning Engines
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Leaning Engines
Following on from another thread about poorly taught subjects at PPL.
Leaning was brought up. I agree it is badly taught due to lack of experence of instructors in their hour building etc.
How many private pilots do actually lean the engine?
MJ
Leaning was brought up. I agree it is badly taught due to lack of experence of instructors in their hour building etc.
How many private pilots do actually lean the engine?
MJ
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I only started to lean when I bought a share in my current steed last November. Didn't before that because I was sh1t scared of the engine even getting remotely near the point of quitting; even the slightest change in engine tone was not an enjoyable experience.
I know this is incorrect but wasn't taught during PPL, so didn't learn about it until later.
In fact the for the first 15 hours of my PPL training I thought the mixture control was just a way of shutting the engine down
Andy
I know this is incorrect but wasn't taught during PPL, so didn't learn about it until later.
In fact the for the first 15 hours of my PPL training I thought the mixture control was just a way of shutting the engine down
Andy
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Always lean - and always fly as high as possible.
Came as a big surprise when on a trip in France a couple of years back I got my Warrior down from 34 litres an hour to 26 (Cruising at FL75). That's a saving worth having.
Just wait until you move onto something like a Seneca. In that you have a fuel flow meter - almost straight after take-off you pull the fuel levers back to 15 gph in the climb - then back further to 10gph in the cruise. Really unsettling the first time you do it as it's totally against everything you were taught in a small single.
Came as a big surprise when on a trip in France a couple of years back I got my Warrior down from 34 litres an hour to 26 (Cruising at FL75). That's a saving worth having.
Just wait until you move onto something like a Seneca. In that you have a fuel flow meter - almost straight after take-off you pull the fuel levers back to 15 gph in the climb - then back further to 10gph in the cruise. Really unsettling the first time you do it as it's totally against everything you were taught in a small single.
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As you say, it can make a big difference, especially to the wallet.
I flew to Ireland and back at the weekend in an aircraft that made it easy, with all sorts of whizzy computerised displays of fuel flow, egt for each cylinder, and a 'lean assist' function that walks you through the whole process as you do it.
The fuel flow dropped from 12 gph at full rich to just under 9 at best economy flying at around 7,000', which was more than enough to finance a few pints of Guinness.
I flew to Ireland and back at the weekend in an aircraft that made it easy, with all sorts of whizzy computerised displays of fuel flow, egt for each cylinder, and a 'lean assist' function that walks you through the whole process as you do it.
The fuel flow dropped from 12 gph at full rich to just under 9 at best economy flying at around 7,000', which was more than enough to finance a few pints of Guinness.
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Leaning ...
I lean the Archer above 3500'. It has an exhaust temperature gauge which makes the process easy.
I tend not to lean the 152. I guess that is because:
1. I fly shorter trips.
2. I fly more locally, which means lower altitude (South East airspace).
3. There is no ET gauge, so rely on engine note to lean correctly. No biggy, but that gauge in the Archer is fun to watch.
Both aircraft are hired wet.
TG
I tend not to lean the 152. I guess that is because:
1. I fly shorter trips.
2. I fly more locally, which means lower altitude (South East airspace).
3. There is no ET gauge, so rely on engine note to lean correctly. No biggy, but that gauge in the Archer is fun to watch.
Both aircraft are hired wet.
TG
Last edited by Tall_guy_in_a_152; 25th Apr 2003 at 07:01.
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During my PPL, no. Now, yes - for taxi and cruise. Personally I don't think it is not taught because of a lack of experience of the instructors. I think it isn't taught because ignoring it means one less thing to worry about, it's not tested on, it isn't essential in typical training types, the instructor is not paying for fuel or engines and most training (certainly in the south east) is done at low altitudes.
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Leaning has become fairly automatic for me. When I've finished climbing, I level off, accelerate, trim, then reach for the mixture control. Even if it's 1500 feet. The only time I don't lean is when I'm doing circuits or practising manoeuvres that involve high power settings. In an O-300 C172 I get about 25 or 26 litres per hour at 2300rpm.
Why do it if it's not fun?
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Not on my current aircraft. But that's only because it doesn't have a mixture control - it's all done automatically.
I have on every other aircraft. Never really got the hang of using the EGT when leaning - it always seems to lag more than I expect - that's because as a student none of the aircraft I flew had a serviceable EGT guage, so I was only taught the method of leaning till it runs rough then pushing it forward a bit. But the only aircraft I've ever flown with EGT guages that worked all had fuel-flow meters, so I just set the fuel flow recommended by instructors for each phase of flight.
FFF
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I have on every other aircraft. Never really got the hang of using the EGT when leaning - it always seems to lag more than I expect - that's because as a student none of the aircraft I flew had a serviceable EGT guage, so I was only taught the method of leaning till it runs rough then pushing it forward a bit. But the only aircraft I've ever flown with EGT guages that worked all had fuel-flow meters, so I just set the fuel flow recommended by instructors for each phase of flight.
FFF
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Leaning can save you more than 20% in fuel for the same speed. There is NO negative impact on the engine especially if you can lean LOP (lean of peak) where the temps start to fall again.
Full-forward on everything normally means about 125F-150F ROP (rich of peak); that's how engines tend to be set up, for max power and extra cooling (plenty of unburnt fuel) during a full-power climb. But it's silly to cruise like that.
The trouble is that to lean correctly you need adequate engine instrumentation. With that, e.g. an EDM700, you can lean until you see peak EGT and then continue LOP; once LOP there is little additional "mpg" gain because LOP engine power output is nearly proportional to fuel flow.
I am suprised someone here leaning a Seneca during climb - Lycoming specifically prohibit leaning above 75% power so the man must have meant a cruise climb at 75% power or less, and with the airspeed being sufficient for cooling.
Carburreted engines are harder to lean because of uneven fuel distribution, so the onset of vibration tends to be seen earlier. The trouble is that if one leans only part-way to peak-EGT, one could end up in the detonation region (~50F ROP) - although detonation isn't actually likely to happen below 75% power.
A good reference for this type of engine management is Deakin's articles at avweb.com.
Full-forward on everything normally means about 125F-150F ROP (rich of peak); that's how engines tend to be set up, for max power and extra cooling (plenty of unburnt fuel) during a full-power climb. But it's silly to cruise like that.
The trouble is that to lean correctly you need adequate engine instrumentation. With that, e.g. an EDM700, you can lean until you see peak EGT and then continue LOP; once LOP there is little additional "mpg" gain because LOP engine power output is nearly proportional to fuel flow.
I am suprised someone here leaning a Seneca during climb - Lycoming specifically prohibit leaning above 75% power so the man must have meant a cruise climb at 75% power or less, and with the airspeed being sufficient for cooling.
Carburreted engines are harder to lean because of uneven fuel distribution, so the onset of vibration tends to be seen earlier. The trouble is that if one leans only part-way to peak-EGT, one could end up in the detonation region (~50F ROP) - although detonation isn't actually likely to happen below 75% power.
A good reference for this type of engine management is Deakin's articles at avweb.com.
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I am not aware that Lycoming specifically prohibit leaning - In fact at high elevations and/or high temperatures you will NEED to lean to achieve maximum available power for take-off.
The EDM that IO540 mentions is a fab piece of kit - specifically because the probes are positioned in every cylinder - not just in one. That means that as you lean you can see which cylinder reaches peak first thereby reducing any tendency to run too hot.
I used to fly aircraft with Continental IO 550 engines. That engine was specifically set up to run with very wide throttle settings (full in many cases) and various power settings both lean and rich of peak (by 40 deg F). Interestingly, peak EGT was not approved for any length of time due to this being too hot.
By not leaning you are actually increasing wear on the engine by causing excessive lead build up on the valves which in turn fail to seat properly.
It is also worth noting that most of our piston engines are fuel cooled to some extent (as well as air cooled). The limitaion on leaning your engine may occur way before 40 deg rich of peak if the cylinders fail to cool adequately thru lack of fuel.
I am therefore a great exponent of multi-probe EGT and CHT instruments as well as accurate fuel flow instrumentation. Sadly the CAA make it rather expensive to pursue installation of these devices as far as full certification and approval (and then bang the drum about being a safety regulation group!)
The EDM that IO540 mentions is a fab piece of kit - specifically because the probes are positioned in every cylinder - not just in one. That means that as you lean you can see which cylinder reaches peak first thereby reducing any tendency to run too hot.
I used to fly aircraft with Continental IO 550 engines. That engine was specifically set up to run with very wide throttle settings (full in many cases) and various power settings both lean and rich of peak (by 40 deg F). Interestingly, peak EGT was not approved for any length of time due to this being too hot.
By not leaning you are actually increasing wear on the engine by causing excessive lead build up on the valves which in turn fail to seat properly.
It is also worth noting that most of our piston engines are fuel cooled to some extent (as well as air cooled). The limitaion on leaning your engine may occur way before 40 deg rich of peak if the cylinders fail to cool adequately thru lack of fuel.
I am therefore a great exponent of multi-probe EGT and CHT instruments as well as accurate fuel flow instrumentation. Sadly the CAA make it rather expensive to pursue installation of these devices as far as full certification and approval (and then bang the drum about being a safety regulation group!)
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I was never given any advice about leaning during my training, and when I asked the owner of the school about it, he said that it's cheaper to burn avgas than to have engines burn due to excess lean running. Don't know if it's true but it sounded plausible to me!
I always lean as necessary on injected engines but don't on non injected engines - don't know why force of habit I 'spose.
How many of youy brave leaners will actually lean back whilst say mid channel in a single- me , I don't touch the damn thing over water, no sir whatever it is coasting out it stays that way
I always lean as necessary on injected engines but don't on non injected engines - don't know why force of habit I 'spose.
How many of youy brave leaners will actually lean back whilst say mid channel in a single- me , I don't touch the damn thing over water, no sir whatever it is coasting out it stays that way
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How many of you brave leaners will actually lean back whilst say mid channel in a single
The particular aircraft I was flying makes it especially easy, with a fuel flow meter and egt and cht monitoring for every cylinder, but I'd still make the effort in any machine.
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Lycoming are no different to continental in most cases. They don't usually recommend leaning above 75% power, although it does depend on the airframe it is fitted to, the major exception I know of is the lycoming L/TIO 540, where leaning in climb (85%) is acceptable. It might be more useful if the particular model of a/c is mentioned here. For example, the seneca comes with both lycoming (naturally aspirated) engines, (seneca 1) and continentals (turbocharged) 2,3,4, and 5. You can lean the 1 for takeoff if necessary, but NEVER the turbocharged ones for takeoff. It depends on whether it is naturally aspirated or turbocharged.
While we're at it, yes it can be efficient to cruise higher with regard to fuel, but depending upon how you are paying for the aircraft it can be more expensive to do so. Fuel cost is but one facet of the overall picture, and with normally aspirated engines, higher is not always cheaper.
While we're at it, yes it can be efficient to cruise higher with regard to fuel, but depending upon how you are paying for the aircraft it can be more expensive to do so. Fuel cost is but one facet of the overall picture, and with normally aspirated engines, higher is not always cheaper.
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M14P
Yes one needs to lean at high elevations etc but then the engine is nowhere near developing full rated hp. If the airfield is at say 7000ft then the full throttle hp may be only 60% of max rated. So one isn't actually leaning above 75% power.
There are various articles on the lycoming website - sorry I don't have the URLs handy but could dig them up.
Not a problem in the UK
What happens with a turbo engine (which would develop max rated hp at 7000ft) I don't know. Do they need leaning at takeoff?
Yes one needs to lean at high elevations etc but then the engine is nowhere near developing full rated hp. If the airfield is at say 7000ft then the full throttle hp may be only 60% of max rated. So one isn't actually leaning above 75% power.
There are various articles on the lycoming website - sorry I don't have the URLs handy but could dig them up.
Not a problem in the UK
What happens with a turbo engine (which would develop max rated hp at 7000ft) I don't know. Do they need leaning at takeoff?
No leaning for take off in a forced induction a/c. Max horsepower is maintained up to whatever the rated altitude is.
Apart from that caveat, I lean anytime the manual says I can, should or must, at all altitudes including below 1000'.
Apart from that caveat, I lean anytime the manual says I can, should or must, at all altitudes including below 1000'.
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Avweb.com has a great article on leaning (J Deakin I think).
On a similar subject, there is also a pretty good 45 min video sold via Sporty's which gives a lot of info on engine (recip) management, fuel mixtures etc.
On a similar subject, there is also a pretty good 45 min video sold via Sporty's which gives a lot of info on engine (recip) management, fuel mixtures etc.
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When learning i was tought the old wives tale dont lean til over 3000 and by the way just forget it anyway you've got more important things to worry about!
I didnt know what the red knob did for years i suspect like most.
Then bought into an old cherokee 180 which fouled its bottom plugs if you didn't lean.So started to learn a bit.
biggest learning curve was when i sat behind an IO540 which has a fuel flow. Properly leaned out the difference is 24gph full rich in a nominal 65% cruise as opposed to 12.5gph makes a hell of a difference.
Read Deakin he explains it all. following his advice i just had a EDM 700 fitted what a wonderful toy!
Someone was worrying about detonation in the context of running near peak egt at 75% power at altitude, if you look at most poh's you cannot get 75% power at any setting at that sort of altitude with a normally aspirated or injected engine. i cannot get near 75% at 8K.
certainly my poh expressly forbids lean of peak opperation and so do most folks advise agains trying to unless you also have gamijectors. I have for short periods set lop and it seems to work much cooler engine with little power loss.
Anyone got an opinion on lop running and gami's????
I didnt know what the red knob did for years i suspect like most.
Then bought into an old cherokee 180 which fouled its bottom plugs if you didn't lean.So started to learn a bit.
biggest learning curve was when i sat behind an IO540 which has a fuel flow. Properly leaned out the difference is 24gph full rich in a nominal 65% cruise as opposed to 12.5gph makes a hell of a difference.
Read Deakin he explains it all. following his advice i just had a EDM 700 fitted what a wonderful toy!
Someone was worrying about detonation in the context of running near peak egt at 75% power at altitude, if you look at most poh's you cannot get 75% power at any setting at that sort of altitude with a normally aspirated or injected engine. i cannot get near 75% at 8K.
certainly my poh expressly forbids lean of peak opperation and so do most folks advise agains trying to unless you also have gamijectors. I have for short periods set lop and it seems to work much cooler engine with little power loss.
Anyone got an opinion on lop running and gami's????
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I hadn't really come across it in the UK other than as a cursory lesson before but freshly arrived back from a trip to SA where many of the airfields are above 3000ft it has now been drummed into me.
My instructor there even made the point about leaning once again whilst cleared for take off and not to allow ATC to become impatient with you whilst this takes place.
My instructor there even made the point about leaning once again whilst cleared for take off and not to allow ATC to become impatient with you whilst this takes place.