Engine mixture guidelines

On Sat, 30 Dec 2006 09:59:53 -0800, Darkwing wrote
(in article ) :


"Mxsmanic" wrote in message
...
Up to now when flying in simulation, I've had the simulator take care
of engine mixture adjustments. However, since I'd have to do this
myself in real life, I've decided to make some modest attempts at
managing mixture myself. Unfortunately, the POH and the other sources
I've consulted are rather vague on how mixture should be adjusted.
Can anyone offer general guidelines on when to enrich or lean the
mixture? It seems that max rich is used when maximum power is
required (?), such as at take-off, but I'm not clear when the mixture
should be leaned in particular. And what are the potential
consequences of an incorrect mixture?

--
Transpose mxsmanic and gmail to reach me by e-mail.

Ask your instructor! HAHAHAHAHA!

He is not willing to pay for an instructor. All of the instructors here have
stopped giving him free instruction.

If he wants an answer he can pay my going rate of $40 an hour via PayPal and
I will reply by email. No refunds if he disagrees with my answer.

(snipped)
Ask your instructor! HAHAHAHAHA!

He is not willing to pay for an instructor. All of the instructors here
have
stopped giving him free instruction.

(snipped)
In that case, like a runaway train without an engine, the entire discussion
will gradually coast to a stop...

On Tue, 2 Jan 2007 01:12:46 -0800, Thomas Borchert wrote
(in article ):

Mxsmanic,

Thanks! Is the stated rule that mixture should be adjusted to just
short of maximum EGT pretty reliable under all circumstances?


No. It's a very bad rule, actually. Go find more info on leaning on the
net, and you'll see.



The only things that start more arguments than flying "lean of peak" are
slips with flaps and a discussion of lift.

On Sat, 30 Dec 2006 13:56:30 -0800, Scott Post wrote
(in article ):

In article ,
Mxsmanic wrote:
Up to now when flying in simulation, I've had the simulator take care
of engine mixture adjustments. However, since I'd have to do this
myself in real life, I've decided to make some modest attempts at
managing mixture myself. Unfortunately, the POH and the other sources
I've consulted are rather vague on how mixture should be adjusted.
Can anyone offer general guidelines on when to enrich or lean the
mixture? It seems that max rich is used when maximum power is
required (?), such as at take-off, but I'm not clear when the mixture
should be leaned in particular. And what are the potential
consequences of an incorrect mixture?


If you're simulating a rental just leave it full rich.



Ouch!

But ain't it the truth?

On Sat, 30 Dec 2006 09:27:14 -0800, Mxsmanic wrote
(in article ):

Up to now when flying in simulation, I've had the simulator take care
of engine mixture adjustments. However, since I'd have to do this
myself in real life, I've decided to make some modest attempts at
managing mixture myself. Unfortunately, the POH and the other sources
I've consulted are rather vague on how mixture should be adjusted.
Can anyone offer general guidelines on when to enrich or lean the
mixture? It seems that max rich is used when maximum power is
required (?), such as at take-off, but I'm not clear when the mixture
should be leaned in particular. And what are the potential
consequences of an incorrect mixture?



Okay, despite the opinion and experience of many pilots and mechanics, it is
time to point out that most engine and aircraft manufacturers do not
recommend running engines lean of peak. There are some mods out there that
are specifically designed for LOP operation (GAMI injectors, most notably)
and there are a few pilots here who are strong advocates of LOP operation.
Despite the fact that LOP is recommended by some highly respected pilots,
theirs is not the majority opinion, however.

There are even conspiracy theorists who suggest that engine manufacturers
discourage LOP deliberately to shorten engine life and increase sales.
(Apparently they presume that the increased sales outweigh the potential cost
of class-action lawsuits.)

There are equally respected pilots who argue in favor of ROP operation. They
figure that the engineers who built the engine probably know best how to take
care of it. Given that the owner of my flight school agreed with them, I flew
ROP (and probably will again).

The LOP advocates will tell you that running ROP is the reason so many
engines get top overhauls before TBO. I tend to think that the reason for it
is that too many planes don't fly enough, too many pilots don't lean the
mixture at all, and pilots don't inspect the engine for things like damaged
valves which, if not detected, will cause a cracked cylinder.

I have heard very powerful arguments from both sides about it. I do not hold
a strong opinion either way, but since this thread has been dominated by the
LOP crowd I thought I might just mention that not everyone shares their view.
My own practice is to follow the engine's handbook.

Near as I can determine, the biggest problem with LOP operation is that most
engines run pretty rough, especially if the engine is carbureted. They just
don't distribute the mixture evenly to all cylinders and LOP makes it worse.
It is a little easier to be successful at LOP with an injected engine.

Running ROP makes it a little easier to cool the engine if you are getting
pre-ignition or detonation problems. In general, if the engine is starting to
run rough, you want to make the mixture richer, not leaner.

You should also lean the engine aggressively when taxiing. It is real easy to
foul the plugs by taxiing with a rich mixture. I have known some individual
planes that will fail a mag check every time you taxi with the mixture full
rich.

Skydiving planes generally make it to TBO without a top overhaul or any other
major engine work, despite the fact that several times a day, every day, they
take off, climb at full throttle as fast as possible to drop altitude, then
basically coast back to the field with the engine at idle, with pilots who
don't lean at all or who use all different kinds of leaning strategies. Our
instinct is to call that mistreatment of the engine, but in fact it is the
secret to long engine life: run it constantly and keep it out of the red box.

C,

The only things that start more arguments than flying "lean of peak" are
slips with flaps and a discussion of lift.


It's not only LOP, it's that 50 or 75 ROP is usually a bad place.

--
Thomas Borchert (EDDH)

C,

it is
time to point out that most engine and aircraft manufacturers do not
recommend running engines lean of peak.


Not quite. MOst don't say anything about it. The new ones tend to
provide settings for it.

--
Thomas Borchert (EDDH)

The only things that start more arguments than flying "lean of peak" are
slips with flaps and a discussion of lift.


It's not only LOP, it's that 50 or 75 ROP is usually a bad place.

Part of the reason that "lean of peak" starts so many arguments, and that
they quickly become so acrimonious, is the failure of contributors to state
whether they are talking about peak rpm or peak egt, what instruments are
available, what power level, and what engine ane prop.

There would still be discussions, and they would still be heated; but there
would be a POSSIBILITY that at least two of the contributors MIGHT be
discussing the same subject.

Peter
grrr

On Sun, 7 Jan 2007 02:30:43 -0800, Thomas Borchert wrote
(in article ):

C,

it is
time to point out that most engine and aircraft manufacturers do not
recommend running engines lean of peak.


Not quite. MOst don't say anything about it. The new ones tend to
provide settings for it.



New what? Manufacturers? Engines? Planes? I don't know of any Cessnas, Pipers
or Beeches that provide settings for it. Or Lycomings or Continentals. What
does Cirrus say?

As you know, LOP has been written about quite a lot in recent years. The one
thing I have noticed is that it is a lot easier to get a high performance
engine to run smoothly LOP than it is for the trainer types.

Peter Dohm wrote:



Part of the reason that "lean of peak" starts so many arguments, and that
they quickly become so acrimonious, is the failure of contributors to state
whether they are talking about peak rpm or peak egt,




I have never, ever heard of LOP discussions talk about peak RPM. Why
would that ever even enter the conversation?