Leaning with fixed pitch and no egt

[Jim K]

Went on my first xc last night. Aircraft in question is an Archer III, Lycoming O-360, fixed pitch prop, no egt gauge. Return leg was 4500', so I decided to lean the mixture once we leveled off. I pulled it back what I considered to be slowly, probably 5 sec. or so, until the RPM dropped about 100 and the engine coughed a little, then richened it back to peak RPM. FI admonishes me for pulling it back way too fast, and tells me to push it about halfway back up. Not worth arguing about (especially as poh only says to lean above 5000'), so i did as instructed, but i can't help but think what i did was appropriate.

So... was I too aggressive? My argument is that with a fixed pitch prop, and no autopilot, i can't take my attention away from flying the plane very long, and a minor pitch change will change the engine rpm, so it has to be done somewhat quickly. Also, as long as the engine is running smoothly, and staying cool, it's not producing enough power to damage it.

I'm pretty sure he doesn't read this board, but let me add that I like the guy, and we get along well. Just trying to get another perspective. I've flown with 3 FIs, and one thing I've learned is that sometimes they directly contradict each other, so sometimes you have to figure out what makes the most sense to you.

 

[Salty]

Does the mixture have a vernier control, or just push/pull? You can turn back the mixture with a vernier pretty easily without taking your attention off the plane. You can do it with a push pull also, but it’s admittedly more difficult. That’s why I replaced the push/pull with a vernier when I did my engine overhaul.

 

[Clip4]

Does the mixture have a vernier control, or just push/pull? You can turn back the mixture with a vernier pretty easily without taking your attention off the plane. You can do it with a push pull also, but it’s admittedly more difficult. That’s why I replaced the push/pull with a vernier when I did my engine overhaul.

What Archer has a vernier?

 

[Salty]

What Archer has a vernier?

Probably a lot of them that have had overhauls. But, I’ve never been in one, so I don’t know, that’s why I asked the question.

 

[Clip4]

Went on my first xc last night. Aircraft in question is an Archer III, Lycoming O-360, fixed pitch prop, no egt gauge. Return leg was 4500', so I decided to lean the mixture once we leveled off. I pulled it back what I considered to be slowly, probably 5 sec. or so, until the RPM dropped about 100 and the engine coughed a little, then richened it back to peak RPM. FI admonishes me for pulling it back way too fast, and tells me to push it about halfway back up. Not worth arguing about (especially as poh only says to lean above 5000'), so i did as instructed, but i can't help but think what i did was appropriate.

So... was I too aggressive? My argument is that with a fixed pitch prop, and no autopilot, i can't take my attention away from flying the plane very long, and a minor pitch change will change the engine rpm, so it has to be done somewhat quickly. Also, as long as the engine is running smoothly, and staying cool, it's not producing enough power to damage it.

I'm pretty sure he doesn't read this board, but let me add that I like the guy, and we get along well. Just trying to get another perspective. I've flown with 3 FIs, and one thing I've learned is that sometimes they directly contradict each other, so sometimes you have to figure out what makes the most sense to you.

Without an EGT, the engine can only be leaned for best power using RPM. The POH states:

“Use of the mixture control in cruising flight reduces fuel consumption significantly, especially at higher altitudes. The mixture should be leaned during cruising operation above 5000 ft. altitude and at pilot's discretion at lower altitudes when 75% power or less is being used. If any doubt exists as to the amount of power being used, the mixture should be in the full RICH position for all operations under 5000 feet.”

Lean slowly enough to monitor the RPM increase until the value begins a decrease and return to maximum RPM or lean until engine begins roughness and lean to maximum RPM.

For giggles, ask your FI to explain why the takeoff checklist says mixture set and not full rich.

 

[GeorgeC]

No need to rush; it's a process, not an event. Get in the habit of adjusting it slowly, or one day you'll pull it too far too fast.

What was your % power for your RPM/DA? If 65% or lower, lean until rough, enrich until smooth, don't worry, be happy.

 

[Htaylor]

Probably a lot of them that have had overhauls. But, I’ve never been in one, so I don’t know, that’s why I asked the question.

Archers have a throttle quadrant that doesn't really allow for a Vernier control.

 

[Salty]

Archers have a throttle quadrant that doesn't really allow for a Vernier control.

I see. That makes it easier to move slower than a regular push/pull though.

 

[RyanB]

Probably a lot of them that have had overhauls. But, I’ve never been in one, so I don’t know, that’s why I asked the question.

There are no Archer III’s with vernier controls.

 

[luvflyin]

Went on my first xc last night. Aircraft in question is an Archer III, Lycoming O-360, fixed pitch prop, no egt gauge. Return leg was 4500', so I decided to lean the mixture once we leveled off. I pulled it back what I considered to be slowly, probably 5 sec. or so, until the RPM dropped about 100 and the engine coughed a little, then richened it back to peak RPM. FI admonishes me for pulling it back way too fast, and tells me to push it about halfway back up. Not worth arguing about (especially as poh only says to lean above 5000'), so i did as instructed, but i can't help but think what i did was appropriate.

So... was I too aggressive? My argument is that with a fixed pitch prop, and no autopilot, i can't take my attention away from flying the plane very long, and a minor pitch change will change the engine rpm, so it has to be done somewhat quickly. Also, as long as the engine is running smoothly, and staying cool, it's not producing enough power to damage it.

I'm pretty sure he doesn't read this board, but let me add that I like the guy, and we get along well. Just trying to get another perspective. I've flown with 3 FIs, and one thing I've learned is that sometimes they directly contradict each other, so sometimes you have to figure out what makes the most sense to you.

I think he was being a little over cautious. Spending 5 seconds easing it back doesn’t sound way to fast to me. I see your avatar is a Cherokee, is it your airplane we are talking about? If so, you got the feel for it. 5 seconds is a long time when you know you can do the first couple inches or so right away.

 

[Bonchie]

I don't know why he'd have you push it "halfway" back in. That'd be way too rich. In a Cherokee, lean to rough (and no, you don't have to crawl the mixture back over the course of 30 seconds or something, just don't yank it back) and then nudge it back in to recover the RPM that was lost.

 

[Stewartb]

Out til it stumbles a little, in 1/2 to 3/4". When you get an expensive monitor dollars to doughnuts it'll validate that procedure.

 

[Tantalum]

@Jim K I was taught and told to do it the exact same way you did it, in fact the only admonishment I've had is for not pulling it back fast enough and potentially keeping the aircraft engine too long at a peak location

many people are afraid of the mixture knob and don't really know how to use it well, tend to run the airplane way too rich. if you have a fuel flow gauge then the poh tends to have pretty good tables in there to dial up the mixture and RPM to get the desired fuel flow and percent power

 

[Caramon13]

For me I lean it back until I start seeing a slight RPM drop, then I go a little further until roughness and then move it back to the position when it started to drop, plus a little extra. I don't like to fly right on the edge of the RPM drop, I like a little buffer just in case.

On Cessna's it's mechanical for me, lean until rough, then usually three twists towards rich of the vernier and it's set.

 

[Tantalum]

Anecdotally related.. my friend used to fly An-2 in Ukraine and indicated that they have no real mixture knob on it.. rather, each cylinder has it's own carburetor with a balloon type mechanism that "auto leans" based on the ambient air pressure (there is an "automatic altitude mixture control" adjustment valve though).. but ideally no real need to lean

 

[simtech]

In my Cherokee (O-360) only time I'm full rich is start up and take off. I'm a flat lander so no DA to contend with. But in cruise climb out I lean to max RPM. Once in cruise if I want to go fast I'll lean again to max RPM or to save a bit I'll lean until the engine stumbles then enrich it just enough to make it smooth. Ill do the big pull kinda fast but I also know about where its gonna be anyway. Well and I do go full rich for landing though it's not needed but less to do if a go around is needed.

 

[midlifeflyer]

Out til it stumbles a little, in 1/2 to 3/4". When you get an expensive monitor dollars to doughnuts it'll validate that procedure.

How much you pull out depends a lot o the density altitude 1/2" to 3/4" would be overly rich for taxiing on the ground in Denver.

But you make the right point. The old school "lean until engine roughness, the enrichen to smooth it out" gets one to almost the same place as a full engine monitor with lean assist. I've even heard it's LOP but have not verified that.

 

[Salty]

There are no Archer III’s with vernier controls.

POA, the friendliest place in hell. The only place you can go, and within a matter of minutes, have no less than 4 people correct you on something you didn't actually get wrong in the first place.

 

[RyanB]

have 4 people correct you on something you didn't actually get wrong in the first place.

We’re just correcting you.

 

[Salty]

We’re just correcting you.

You can't correct someone for asking a question. The very first sentence in my post:

Does the mixture have a vernier control, or just push/pull?

Well, you can, but it just makes the place extra friendly.

 

[RyanB]

You can't correct someone for asking a question.

Well, you can, but it just makes the place extra friendly.

That’s why it’s a correction. Educating you that an Archer doesn’t have that style mixture control.

 

[Salty]

That’s why it’s a correction. Educating you that an Archer doesn’t have that style mixture control.

Maybe the sixth time will help me understand. Even though I clearly showed I understood the FIRST time.

I see. That makes it easier to move slower than a regular push/pull though.

Anyway, thanks for driving my point home with a sledge hammer.

 

[wilkersk]

For the sake of argument, assuming a standard day at your stated altitude (4,500' PA), and according to the POH, if you're not over 2,450rpm, then what you did was perfectly alright.

 

[wilkersk]

How much you pull out depends a lot o the density altitude 1/2" to 3/4" would be overly rich for taxiing on the ground in Denver.

But you make the right point. The old school "lean until engine roughness, the enrichen to smooth it out" gets one to almost the same place as a full engine monitor with lean assist. I've even heard it's LOP but have not verified that.

And then, there's "the big pull" : http://www.csobeech.com/lean-of-peak.html

 

[MIFlyer]

Anecdotally related.. my friend used to fly An-2 in Ukraine and indicated that they have no real mixture knob on it.. rather, each cylinder has it's own carburetor with a balloon type mechanism that "auto leans" based on the ambient air pressure (there is an "automatic altitude mixture control" adjustment valve though).. but ideally no real need to lean

Sounds like the pressure carbs on geared lycomings, though those are one per engine


Sent from my iPad using Tapatalk

 

[midwestpa24]

Sounds like your instructor was scared of the engine shutting down. He should try it once or twice. Its not as scary as it sounds. On one aircraft I fly, the difference between the stumble and off is about 1/8 of an inch or less. If you go too far, all you have to do is push it back in, the engine will come right back on.

In your situation and aircraft, I would pull it back until you see the peak and/stumble, then enrichen the mixture 1/2 inch past the peak rpm.

 

[RyanB]

Maybe the sixth time will help me understand. Even though I clearly showed I understood the FIRST time.

Anyway, thanks for driving my point home with a sledge hammer.

You made an assumption that was incorrect. A few of us made a correction to inform you that Archer’s don’t have a vernier. Whatever kind of conclusion you’d like to draw from that is your game, but none of us drove any point of yours home - we just made a simple correction.

These things happen occasionally, as it proves that none of us know everything, and so it’s okay to admit that.

 

[Jim K]

No need to rush; it's a process, not an event. Get in the habit of adjusting it slowly, or one day you'll pull it too far too fast.

What was your % power for your RPM/DA? If 65% or lower, lean until rough, enrich until smooth, don't worry, be happy.

Yes, shooting for 65%

I think he was being a little over cautious. Spending 5 seconds easing it back doesn’t sound way to fast to me. I see your avatar is a Cherokee, is it your airplane we are talking about? If so, you got the feel for it. 5 seconds is a long time when you know you can do the first couple inches or so right away.

That's the one. It's a club plane. We also have a couple Dakotas, but the archer is based much closer, so I'll probably fly it more.

Thanks for all the responses. I have a fair amount of experience tuning carburetors and FI systems, so I get the theory. I think when he heard it stumble he was afraid I was going to kill it, which I get. He has a lot of experience in a lot of different planes from a da40 to a Lear 75, so i respect his opinion, I just felt he was a bit over cautious here.

I had another instructor tell me never to use the parking brake because he took off with it dragging once. Personally I don't feel safe doing a runup without the brakes set, so I tend to take it all with a grain of salt.

 

[chemgeek]

Lycoming's instructions for most engines is to lean until engine roughness is encountered, then enrichen slightly until engine smooths out. This is "best economy." For "best power" you would enrichen to peak rpm after leaning to roughness. For my O-320-E2G, leaning to first roughness and 3-4 clicks toward rich does the trick for best economy. That's the recommended procedure for cruise as long as you are below 75% power.

 

[IK04]

obfuscate
verb
ob·fus·cate | \ ˈäb-fə-ˌskāt ; äb-ˈfə-ˌskāt, əb-\
obfuscated; obfuscating
Definition of obfuscate
transitive verb

1a : to throw into shadow : darken
b : to make obscure obfuscate the issueofficials who … continue to obscure and obfuscate what happened— Mary Carroll
2 : confuse obfuscate the reader
intransitive verb

: to be evasive, unclear, or confusing The suspect often obfuscated during the interrogation.

 

[WannFly]

Yes, shooting for 65%


That's the one. It's a club plane. We also have a couple Dakotas, but the archer is based much closer, so I'll probably fly it more.

Thanks for all the responses. I have a fair amount of experience tuning carburetors and FI systems, so I get the theory. I think when he heard it stumble he was afraid I was going to kill it, which I get. He has a lot of experience in a lot of different planes from a da40 to a Lear 75, so i respect his opinion, I just felt he was a bit over cautious here.

I had another instructor tell me never to use the parking brake because he took off with it dragging once. Personally I don't feel safe doing a runup without the brakes set, so I tend to take it all with a grain of salt.

That. use your own judgement when you are the PIC. example, we always turn into the wind when doing runup. great, what about when its -10 below? why on earth would you want cold air the blow in when the cylinders are barely at 280 degrees... I asked that to one my CFI's once, he scratched is head and finally admitted most planes where there isnt an engine monitor, they go by whats they have been doing. curiously enough that habit didnt change after as well.

same with leaning. yah the POH says run full rich if below 5000, i dont, i go by what my engine monitor tells me, granted the POH was written keeping one EGT gauge in mind. however, the same engine on Cezzna POH says to run full rich below 3000. On the ground, i am shooting for best power for take off or a min of 2350 when holding brakes, i move the mixture control until that is achieved, then i go my merry way (900 MSL airport, in summer sometimes close to 3000 DA)

 

[Jim K]

That. use your own judgement when you are the PIC. example, we always turn into the wind when doing runup. great, what about when its -10 below? why on earth would you want cold air the blow in when the cylinders are barely at 280 degrees... I asked that to one my CFI's once, he scratched is head and finally admitted most planes where there isnt an engine monitor, they go by whats they have been doing. curiously enough that habit didnt change after as well.

same with leaning. yah the POH says run full rich if below 5000, i dont, i go by what my engine monitor tells me, granted the POH was written keeping one EGT gauge in mind. however, the same engine on Cezzna POH says to run full rich below 3000. On the ground, i am shooting for best power for take off or a min of 2350 when holding brakes, i move the mixture control until that is achieved, then i go my merry way (900 MSL airport, in summer sometimes close to 3000 DA)

Do you go full rich to land, or do you have a means to return to your takeoff setting? We are at 750', and 3000+ DA in the summer is not uncommon.

 

[RyanB]

That. use your own judgement when you are the PIC. example, we always turn into the wind when doing runup. great, what about when its -10 below? why on earth would you want cold air the blow in when the cylinders are barely at 280 degrees... I asked that to one my CFI's once, he scratched is head and finally admitted most planes where there isnt an engine monitor, they go by whats they have been doing. curiously enough that habit didnt change after as well.

same with leaning. yah the POH says run full rich if below 5000, i dont, i go by what my engine monitor tells me, granted the POH was written keeping one EGT gauge in mind. however, the same engine on Cezzna POH says to run full rich below 3000. On the ground, i am shooting for best power for take off or a min of 2350 when holding brakes, i move the mixture control until that is achieved, then i go my merry way (900 MSL airport, in summer sometimes close to 3000 DA)

Agree.

It’s also to note that full rich is far richer than maximum power requires.

 

[RyanB]

Do you go full rich to land, or do you have a means to return to your takeoff setting? We are at 750', and 3000+ DA in the summer is not uncommon.

No need. You’re leaned for best power. Keep it that way on a day like that.

 

[Jim K]

No need. You’re leaned for best power. If you went full rich, the airplane wouldn’t be able to produce best power under those atmospheric conditions.

Okay...I wasnt thinking... you can always set it on approach or in the pattern, add a little extra, and be very close to your best setting on the ground.

 

[WannFly]

Agree.

It’s also to note that full rich is far richer than maximum power requires.

something else i had learnt from POA (imagine that), it might have been from either from you or @Ravioli , cant remember know, before shut down, aim for 1000 RPM, leave it there, next time when you start dont touch the throttle and that has worked perfectly. i used to struggle the sweet spot while starting...

 

[midlifeflyer]

same with leaning. yah the POH says run full rich if below 5000, i dont,

I was the student in a proficiency check on a hot day at my 246 msl home airport. Since I had a little () more experience than he with density altitude and leaning, with density altitude in the 2,000+' range I showed him how leaning for takeoff would increase available power and make our takeoff easier. Eye-opener for him.

 

[midlifeflyer]

And then, there's "the big pull" : http://www.csobeech.com/lean-of-peak.html

Love those guys but I suspect the "big pull" is less of an issue than they make it. If the concern is high CHTs, at least in the airplanes I have flown, I have not seen temps rise to the danger level in the ordinary course of the leaning process. That said, especially on high performance engines, I kind of like the idea of learning where the ballpark setting is manually. Just makes the whole thing more efficient.

 

[Ravioli]

something else i had learnt from POA (imagine that), it might have been from either from you or @Ravioli , cant remember know, before shut down, aim for 1000 RPM, leave it there, next time when you start dont touch the throttle and that has worked perfectly. i used to struggle the sweet spot while starting...

I don't know if it was Me, Myself, or I. But that's how I do it.

 

[RyanB]

something else i had learnt from POA (imagine that), it might have been from either from you or @Ravioli , cant remember know, before shut down, aim for 1000 RPM, leave it there, next time when you start dont touch the throttle and that has worked perfectly. i used to struggle the sweet spot while starting...

I don't know if it was Me, Myself, or I. But that's how I do it.

Rob’s intelligence is about 1 standard deviation better than I, so I’m going to say he provided that tid bit of knowledge.