leaning in climb

[Matt]

Hi everyone. I have a leaning question. The POH for my 152 says that the
mixture should be leaned to best power after passing 3000 feet in the climb.
However in other places in the POH (and the Lycoming site) they say not to
lean when at 75% power or higher in cruise. My question: Is the engine
developing less than 75% power during the climb; and is this why leaning in
the climb is OK? Does this guidance in the POH seem contradictory to anyone
except me?

Thanks for all your help.

Matt

[[email protected]]

Matt > wrote:
: Hi everyone. I have a leaning question. The POH for my 152 says that the
: mixture should be leaned to best power after passing 3000 feet in the climb.
: However in other places in the POH (and the Lycoming site) they say not to
: lean when at 75% power or higher in cruise. My question: Is the engine
: developing less than 75% power during the climb; and is this why leaning in
: the climb is OK? Does this guidance in the POH seem contradictory to anyone
: except me?

: Thanks for all your help.

Few things have has much disinformation (DI) and old-wives-tales (OWT) as
aviation. Few things in aviation have as much DI and OWT as engine leaning. I
suggest you read through some of Deakin's articles on www.avweb.com to clarify.

My personal climb-leaning is to lean to a constant EGT. Hold whatever takeoff
EGT is until through 8000'. At that point it's impossible to go over 75% on a
normally aspirated plane.

Even though with the RPM low in a climb, it's probably not possible to exceed
75% power, it's the worst kind of "75% power"... low RPM max MP. Given the low speed
and high angle of attack in a climb, I wouldn't lean to best power until a bit higher
than 3000'. Of course, if it's in the POH is must be gospel.... always driven by the
goals of long engine life, low fuel burn, minimum maintenance, and least money
expended... never by marketing, performance numbers, or band-aid workaround covering
other problems. Nope... never. ;-)

-Cory



--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Jay Honeck]

> Of course, if it's in the POH is must be gospel.... always driven by the
> goals of long engine life, low fuel burn, minimum maintenance, and least
> money
> expended... never by marketing, performance numbers, or band-aid
> workaround covering
> other problems. Nope... never. ;-)

One thing I've learned over a few years of aircraft ownership is that many
of these "rules" are made to fit the most common situation, and must take
into account the lowest common denominator pilot. Because of this, I think
most of the manufacturers are overly cautious about leaning, simply because
they don't want some ham-fisted pilot yanking the mixture back to an
over-lean condition at full power. Thus, the hard and fast "no leaning
below x000 feet rules."

Careful leaning is possible -- indeed desirable -- at any power setting and
altitude. For example, when it's hot (or high, or both), you want to lean
to best power for take-off, and that's at maximum power.

Just don't over-do it. (This is where, IMHO, an engine analyzer pays for
itself. When you have a graphic read-out of EGTs and CHTs for each
cylinder right in front of you, it's much easier not to over-lean.)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Thomas Borchert]

Matt,

> My question: Is the engine
> developing less than 75% power during the climb; and is this why leaning in
> the climb is OK?

Yup. That's where the 3000 feet come from. Because of the lower air density up
there, your airplane will develop less than 75 percent rated power up there.
Two big caveats:

1. We're talking density altitude here. So you might well be leaned during the
roll down the runway at 100 ft MSL elevation, if the temperature is high
enough. Not rare at all.

2. It might make sense to lean even earlier when you want to maintain max
power. One advice given is: Keep the EGT where it was when it stabilized after
took off at full power. If you don't lean, EGT will decrease slowly with
altitude.



--
Thomas Borchert (EDDH)

[Thomas Borchert]

Jay,

> to an
> over-lean condition

Wazzat?

>Thus, the hard and fast "no leaning
> below x000 feet rules."
>

Actually, those rules aren't that hard and fast. I am not aware of any
manufacturer mentioning them for cruise power settings.

--
Thomas Borchert (EDDH)

[[email protected]]

: > My question: Is the engine
: > developing less than 75% power during the climb; and is this why leaning in
: > the climb is OK?

: Yup. That's where the 3000 feet come from. Because of the lower air density up
: there, your airplane will develop less than 75 percent rated power up there.
: Two big caveats:

Actually, 3000' isn't high enough to limit power to 75%. It's only 3" less
than full MP... that'd be 26". If climb RPM is only 2100-2200 or so, THEN it may be
limited to 75%. Cruise power at 3000' DA can easily exceed 75%.

: 1. We're talking density altitude here. So you might well be leaned during the
: roll down the runway at 100 ft MSL elevation, if the temperature is high
: enough. Not rare at all.

Quite normal to have in excess of 2000' increase in DA during the summer.

: 2. It might make sense to lean even earlier when you want to maintain max
: power. One advice given is: Keep the EGT where it was when it stabilized after
: took off at full power. If you don't lean, EGT will decrease slowly with
: altitude.

That's what my post suggested. Very quick, easy, accurate, and safe way to do
things. It does require and EGT, however. It should also be noted that keeping CHTs
below "too high" takes precidence over leaning to a specific EGT. In a long climb you
may have to either nose over for better cooling, or bite the extra fuel burn, fouled
plugs, and decreased power of running WAY rich for best engine long-term health.

Also note that cheaper thermocouple EGT gauges are subject to "cold junction"
errors. They don't read the absolute temperature, but rather the difference between
the probe (hot junction) and connection to the meter (cold junction). Between winter
and summer where that may fluctuate 100 degrees, the indication on the meters will
fluctuate by the same. Colder cold junction (winter) => hotter reading on gauge.

I suspect the more advanced engine monitors compensate for this internally,
but my dumb analog meters do not.

-Cory



: --
: Thomas Borchert (EDDH)


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[OtisWinslow]

My practice has always been to lean for highest rpm when I start the take
off roll. Then richen it up a couple hundred feet up when clearing something
is no longer a factor.



"Matt" > wrote in message
.. .
> Hi everyone. I have a leaning question. The POH for my 152 says that the
> mixture should be leaned to best power after passing 3000 feet in the
> climb. However in other places in the POH (and the Lycoming site) they say
> not to lean when at 75% power or higher in cruise. My question: Is the
> engine developing less than 75% power during the climb; and is this why
> leaning in the climb is OK? Does this guidance in the POH seem
> contradictory to anyone except me?
>
> Thanks for all your help.
>
> Matt
>

[Robert M. Gary]

Can your 152 produce 75% power at 3000 feet?

[Matt]

"Robert M. Gary" > wrote:
> Can your 152 produce 75% power at 3000 feet?

I don't have real-world numbers to back this up, but doing some
interpolation from the cruise numbers in the POH: 75% power is possible at
2425 RPM at 3000 feet with a TAS of 102. In a climb I would be at around 70
knots, so the engine should not be able to reach the cruise RPM of 2425. So
I suppose in a climb at 3000 feet, the engine would not be producing 75%,
and it would be OK to lean.

[Matt]

> I suggest you read through some of Deakin's articles on www.avweb.com to
> clarify.

Yes, I have been reading many great articles on avweb. Unfortunately, my
152 does not have EGT or CHT monitors, so I have to use the "listen, learn,
and pray" method of leaning. I find it mentally difficult to reach over and
start easing the mixture back with the throttle full forward.

[DavidM]

Thomas Borchert wrote:

> 1. We're talking density altitude here. So you might well be leaned during the
> roll down the runway at 100 ft MSL elevation, if the temperature is high
> enough. Not rare at all.

Density altitude cuts the other way as well. If you're flying in cold
weather on a clear day, 3,000 feet indicated altitude might not be that
far above sea level density altitude.

Some day, I'd like to get more information about how density altitude
and my engine interact. By the time the air hits my carb, it's likely
already been warmed up a fair bit, so air density at the carb is not
likely the same as the air density outside the plane.

> 2. It might make sense to lean even earlier when you want to maintain max
> power. One advice given is: Keep the EGT where it was when it stabilized after
> took off at full power. If you don't lean, EGT will decrease slowly with
> altitude.

That's John Deakin's advice as well, and it seems to work. The only
extra consideration is that you want to keep EGT where it would be at a
sea level (DA) takeoff, not necessarily where it was at *this* takeoff.
It might be worth finding a low airport on a day with close-to-ISA
conditions, and actually marking the glass with a blue marker to show
where the needle ends up, though I haven't gone that far yet.

Again, the winter can be a problem, since a sea-level takeoff on a cold
day can put you far below sea level density altitude, and your starting
EGT may be on the high side.


All the best,


David

[[email protected]]

Matt > wrote:
: Yes, I have been reading many great articles on avweb. Unfortunately, my
: 152 does not have EGT or CHT monitors, so I have to use the "listen, learn,
: and pray" method of leaning. I find it mentally difficult to reach over and
: start easing the mixture back with the throttle full forward.

Yeah, I would be too. One thing you might be able to do to "calibrate your
discomfort" would be to climb to an altitude where you cannot get more than 75%...
like 8000' or so. Verify your power at 75% cruise and lean to best power. Note the
mixture position. Linearly interpolate the mixture/altitude from that... :)

If it's your plane, I'd consider adding a cheapie CHT and EGT from Westach.
They're not that expense and it lets you have more real information on engine health.
Not really useful for cruise leaning, but good for a climb leaning and to verify
non-roasted engine CHTs.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[soxinbox]

They probably assume that you have transitioned from Vx or Vy climb to
cruise climb by the time you reach 3000 ft. I do this transition as soon as
I hit pattern altitude.

"Matt" > wrote in message
.. .
> Hi everyone. I have a leaning question. The POH for my 152 says that the
> mixture should be leaned to best power after passing 3000 feet in the
> climb. However in other places in the POH (and the Lycoming site) they say
> not to lean when at 75% power or higher in cruise. My question: Is the
> engine developing less than 75% power during the climb; and is this why
> leaning in the climb is OK? Does this guidance in the POH seem
> contradictory to anyone except me?
>
> Thanks for all your help.
>
> Matt
>

[Roger]

Maybe a cht would help. I think the egt on a carburetor engine isn't much
help. I had a Westach 4 probe EGT on my C150 and found that it didn't help
any except to verify that standard look and listen method was working just
as well. I removed it to put a clock back in the hole. For sale if you
want to try it. BTW I did the Holly Run one year to Tangier Island and many
of the small planes with carburetors had to make the flight with carb heat.
I leaned the engine while using full heat. The engine went to TBO without
any burned valves.

Roger C-150E @ MD43


> wrote in message
...
> Matt > wrote:
> : Yes, I have been reading many great articles on avweb. Unfortunately,
> my
> : 152 does not have EGT or CHT monitors, so I have to use the "listen,
> learn,
> : and pray" method of leaning. I find it mentally difficult to reach over
> and
> : start easing the mixture back with the throttle full forward.
>
> Yeah, I would be too. One thing you might be able to do to "calibrate
> your
> discomfort" would be to climb to an altitude where you cannot get more
> than 75%...
> like 8000' or so. Verify your power at 75% cruise and lean to best power.
> Note the
> mixture position. Linearly interpolate the mixture/altitude from that...
> :)
>
> If it's your plane, I'd consider adding a cheapie CHT and EGT from
> Westach.
> They're not that expense and it lets you have more real information on
> engine health.
> Not really useful for cruise leaning, but good for a climb leaning and to
> verify
> non-roasted engine CHTs.
>
> -Cory
>
> --
>
> ************************************************** ***********************
> * Cory Papenfuss *
> * Electrical Engineering candidate Ph.D. graduate student *
> * Virginia Polytechnic Institute and State University *
> ************************************************** ***********************
>

[Roy Smith]

I don't understand all this talk about leaning in the climb. Watch the
ball, use right rudder, and you get rid of all the lean. Problem solved.

[Ron Natalie]

Thomas Borchert wrote:

>
> 1. We're talking density altitude here. So you might well be leaned during the
> roll down the runway at 100 ft MSL elevation, if the temperature is high
> enough. Not rare at all.

You don't mean leaned here, you mean power-restricted.

For those of us who flew from 6000' airports, we leaned at engine
start and then set best power during the run up. We needed every
ounce of performance we could get to get 152's off the ground at
gross at 8000+ density altitudes.

[Ron Natalie]

OtisWinslow wrote:
> My practice has always been to lean for highest rpm when I start the take
> off roll. Then richen it up a couple hundred feet up when clearing something
> is no longer a factor.
>
>
Actually, on most of the lycomings it's not necessary to screw with this
at all. Set the best power during your run up (at your magcheck rpm).
Climb at Wide Open Throttle. WOT lready adds extra fuel to maintain
engine cooling.

[[email protected]]

Roger > wrote:
: Maybe a cht would help. I think the egt on a carburetor engine isn't much
: help. I had a Westach 4 probe EGT on my C150 and found that it didn't help
: any except to verify that standard look and listen method was working just
: as well. I removed it to put a clock back in the hole. For sale if you
: want to try it. BTW I did the Holly Run one year to Tangier Island and many
: of the small planes with carburetors had to make the flight with carb heat.
: I leaned the engine while using full heat. The engine went to TBO without
: any burned valves.

For cruise leaning, I'll pretty much agree. I put a 4-probe EGT on my PA-28,
but like you say, it generally just will verify that the lean&listen approach works
(or doesn't). One way you may may make it more useful is to play with the carb heat
trick of getting a more even air/fuel distribution. With my analog gauges that's not
really possible, but for a digital readout it may be more useful.

For the lean in a climb, I still think it's *quite* useful... even on carb'd
engines.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[[email protected]]

Roy Smith > wrote:
: I don't understand all this talk about leaning in the climb. Watch the
: ball, use right rudder, and you get rid of all the lean. Problem solved.

Don't *DO* that... I about sprayed coffee all over my computer... :)

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Thomas Borchert]

> For the lean in a climb, I still think it's *quite* useful... even on carb'd
> engines.
>

And priceless for troubleshooting.

--
Thomas Borchert (EDDH)

[[email protected]]

>Actually, on most of the lycomings it's not necessary to screw with this
>at all. Set the best power during your run up (at your magcheck rpm).
>Climb at Wide Open Throttle. WOT lready adds extra fuel to maintain
>engine cooling.

Some of Lyc's specifications result in really rich running
engines. We have a 182RG that has an HA-4 carb, and it runs very rich
at most power settings when the mixture is full forward. The Precision
Aeromotive guys (former Marvel Schebler) tell me that this is the way
Lycoming specified the carb when they designed that particular engine
model (O-540J3C5D), and that you have to get used to playing with the
mixture much more than you did with a 172. We lean while idling on the
ground, full rich for takeoff unless above 3000' DA (as per POH), and
you have to lean it in the climb if you want it to run smoothly and not
smoke. When carb heat is applied in the circuit, it gets pretty rough
unless it's leaned again.
Our airport is at 2975' ASL. We get lots of leaning practice.
Dan

[[email protected]]

Thomas Borchert wrote:
> Jay,
>
> > to an
> > over-lean condition
>
> Wazzat?

That would be if the engine is backfiring ;-)


Personally, I simply lean a fixed-pitch prop Lyc to find peak rpm and
have never had any performance or maintenance issues in nearly a decade
of flying. The engine always seems happy and I suspect that at peak
rpm, I'm probably still blowing a significant amount of unburned fuel
out the exhaust pipe. In those planes I've flown that were equipped
with cht guage, the temps never climbed high enough to be worrisome
either.

[[email protected]]

On Tue, 15 Nov 2005 13:02:57 GMT, "Matt" > wrote:

>Hi everyone. I have a leaning question. The POH for my 152 says that the
>mixture should be leaned to best power after passing 3000 feet in the climb.
>However in other places in the POH (and the Lycoming site) they say not to
>lean when at 75% power or higher in cruise. My question: Is the engine
>developing less than 75% power during the climb; and is this why leaning in
>the climb is OK? Does this guidance in the POH seem contradictory to anyone
>except me?
>
>Thanks for all your help.
>
>Matt
>

I don't think anybody has mentioned the following information, from
Lycoming, which may be useful:
http://www.lycoming.textron.com/support/publications/maintenancePublications/serviceInstructions/SI1094D.pdf

[DavidM]

wrote:

> Personally, I simply lean a fixed-pitch prop Lyc to find peak rpm and
> have never had any performance or maintenance issues in nearly a decade
> of flying. The engine always seems happy and I suspect that at peak
> rpm, I'm probably still blowing a significant amount of unburned fuel
> out the exhaust pipe. In those planes I've flown that were equipped
> with cht guage, the temps never climbed high enough to be worrisome
> either.

Here's a chart:

http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20Operation/Pelican's%20Perch%20Mixture%20Magic_files/pp18d.jpg

The horizontal axis is leaning (left is leaner, right is richer). The
highest point of the BHP curve is peak power -- notice how close it is
horizontally to the highest point of the CHT curve, which represents
the hottest your engine gets.


All the best,


David