Why is LOP (lean of peak) controversial?

I'm not asking about LOP itself, but why it's so "hot" snicker a topic.
It would seem to be a simple thing to me: the cylinders run at decent
temperatures LOP or they do not. What else is there?

I know at least one person in person, and others from their postings, that
are getting success running LOP. I also know at least two persons that
think that LOP is some myth that kills cylinders. One of those two people
tells a story of someone that bought gami injectors, ran LOP, and then
cooked four of six cylinders.

What I don't understand - and what that person hasn't answered, BTW,
perhaps because he doesn't know - is why that person that "cooked" four
cylinders would have failed to see a problem immediately on his CHT probes.

So...what am I missing?

- Andrew

Because in years past, several respected gurus of the GA field had
stated that LOP would "burn the engine up" if you did it, and
recommended running ROP. In fact, Lycoming actually recommended running
50 deg ROP at full power operation, which G. Braly's research has shown
is the absolute worst place to run. Many are probably just trying to
cover their ass for being so wrong in the past. At least that is my
take, since I believe as you do that it is either true or it isn't.
Good point.

Bud


Andrew Gideon wrote:
I'm not asking about LOP itself, but why it's so "hot" snicker a topic.
It would seem to be a simple thing to me: the cylinders run at decent
temperatures LOP or they do not. What else is there?

I know at least one person in person, and others from their postings, that
are getting success running LOP. I also know at least two persons that
think that LOP is some myth that kills cylinders. One of those two people
tells a story of someone that bought gami injectors, ran LOP, and then
cooked four of six cylinders.

What I don't understand - and what that person hasn't answered, BTW,
perhaps because he doesn't know - is why that person that "cooked" four
cylinders would have failed to see a problem immediately on his CHT probes.

So...what am I missing?

- Andrew

On 09/26/06 15:38, Andrew Gideon wrote:
I'm not asking about LOP itself, but why it's so "hot" snicker a topic.
It would seem to be a simple thing to me: the cylinders run at decent
temperatures LOP or they do not. What else is there?

I know at least one person in person, and others from their postings, that
are getting success running LOP. I also know at least two persons that
think that LOP is some myth that kills cylinders. One of those two people
tells a story of someone that bought gami injectors, ran LOP, and then
cooked four of six cylinders.

What I don't understand - and what that person hasn't answered, BTW,
perhaps because he doesn't know - is why that person that "cooked" four
cylinders would have failed to see a problem immediately on his CHT probes.

So...what am I missing?

- Andrew


I think John Deakin covered this topic in one of his columns. He explained
why most of the POHs are worded the way they are, even when it doesn't make
sense. For example, have a look at this article (I think this is the right
one - I can't find the index to his articles on the AVWeb site any longer):

http://www.avweb.com/news/pelican/186216-1.html

My impression of the point he tried to make was that the manufacturers
believe LOP operations is hard to get right unless you really know what
you're doing (and have the proper measuring equipment, i.e.: EGT) and that
ROP operations is "safer" from a legal standpoint.

.... but it's been a while since I've read his articles on the topic, so
I could be off here.

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

Andrew Gideon wrote:

I know at least one person in person, and others from their postings, that
are getting success running LOP.

You can add me to the list of aircraft owners who religiously run LOP. I
bought my aircraft from a pilot who also operated the engine LOP, and I was
able to get about 2,600 hours out of an engine that had an 1,800 hours TBO.
In the interest of full disclosure there was some cylinder work done to the
engine early on, but I can guarantee it was not because a cylinder got
cooked. It probably had to do with the fact that they were Continental
cylinders.

In my case, my engine's cylinder head temperatures rarely get above 310
degrees F and most times operate in the 285 degree F range during cruise
flight. The times they do climb to 310 or 320 degrees F is when I am
climbing to altitude on a very hot day.

One note: Running LOP requires a meticulously maintained ignition system.
Plugs need to be cleaned every 100 hours or so, plug wires need to be
inspected and replaced if needed, magnetos have to be operating to
capacity, and capacitors cannot fail.

Something as simple as one fouled plug can result in unacceptably high
exhaust gas temperatures that lead to a higher than desired turbo-inlet
temperatures.

I also know at least two persons that
think that LOP is some myth that kills cylinders. One of those two people
tells a story of someone that bought gami injectors, ran LOP, and then
cooked four of six cylinders.

Without knowing their specifics, I can say with experience of operating a
turbo-normalized Bonanza that running LOP does introduce the RISK of
cooking cylinders, but this risk is easily managed, in part, by including
the engine analyzer in one's scan every minute or two.

Leaning to a lean of peak temperature involves pulling the mixture PAST
peak temperature to a relative fuel flow, then allowing airspeed and engine
temperatures to stabilize (perhaps a few minutes of level flight). Once
stable, the mixture is then enrichened to peak temperature in order to
discover peak temperature and then steadily but without delay leaned back
to about 75 degrees lean of peak.

Constant monitoring of the engine analyzer gauge and fine tuning of the
mixture knob is mandatory.

Changing altitudes (usually descending), even in my turbo-normalized
aircraft, does require a slight change in mixture or temperatures can begin
to climb.

What I don't understand - and what that person hasn't answered, BTW,
perhaps because he doesn't know - is why that person that "cooked" four
cylinders would have failed to see a problem immediately on his CHT probes.

My speculation is that it could be one of three reasons. First, but most
unlikely, perhaps the probes were incorrectly installed. Second, maybe
this owner failed to monitor his engine analyzer often enough, which could
be a result of the location of the gauge in the panel or simply the pilot's
weaker instrument scanning discipline. And thirdly, this owner may not
have had the engine analyzer high-temperature alarms properly set up?
Again, just speculation here.

--
Peter

"Peter R." wrote:

In my case, my engine's cylinder head temperatures rarely get above 310
degrees F and most times operate in the 285 degree F range during cruise
flight. The times they do climb to 310 or 320 degrees F is when I am
climbing to altitude on a very hot day.

I should have included that 380 degrees F is considered the absolute top
end of the safe temperature curve, at least according to Tornado Alley
Turbo and GAMI, both of whom have done extensive testing of LOP operations.

Even on a hot day at higher density altitude (and effectively less ram air
cooling), 320 degrees F is the highest I have seen my cylinder head
temperatures reach.

--
Peter

So...what am I missing?

- Andrew


Hi Andrew

Google Walter Atkinson LOP.
He is the most knowledgeable that I know of on aircraft engines and is
always happy to discuss engine questions - especially LOP.
If you just want to read what he has to say, search the archives in the
Cessna and Piper groups.

HTH

Tony

--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE

"Mark Hansen" wrote in message
...

I think John Deakin covered this topic in one of his columns. He explained
why most of the POHs are worded the way they are, even when it doesn't
make
sense. For example, have a look at this article (I think this is the right
one - I can't find the index to his articles on the AVWeb site any
longer):

http://www.avweb.com/news/pelican/


http://www.avweb.com/news/pelican/186216-1.html

My impression of the point he tried to make was that the manufacturers
believe LOP operations is hard to get right unless you really know what
you're doing (and have the proper measuring equipment, i.e.: EGT) and that
ROP operations is "safer" from a legal standpoint.

... but it's been a while since I've read his articles on the topic, so
I could be off here.

Read #8, 15, 16 and particularly #18. Those are the basis of the Advanced
Pilot Seminars http://www.advancedpilot.com/index.html (Well worth a couple
thousand $$ to protect a $25-30K engine...not to mention your butt).

If applicable, read the Turbo's series, #31-36, and #59, 63,64 as well.

--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO (MTJ)

"Andrew Gideon" wrote:


One of those two people tells a story of someone that bought gami
injectors, ran LOP, and then cooked four of six cylinders.


Another example of how a little knowledge is a dangerous thing.

*Improper* LOP operating technique can harm cylinders, even cause
catastrophic failure by detonation.

--
Dan
C172RG at BFM

On Wed, 27 Sep 2006 09:20:12 -0500, Dan Luke wrote:

*Improper* LOP operating technique can harm cylinders, even cause
catastrophic failure by detonation.

Hmm. Detonation, if I follow all this correctly, yields lower EGTs. So
someone leaning by EGT could be fooled into thinking that all is well,
even while cylinders are being damaged. This is exactly the type of idea
I was missing; now I think I see.

But CHT goes up, right? Would it go up enough (ie. beyond 400) to raise a
pilot's concern?

- Andrew

"Andrew Gideon" wrote in message
news
On Wed, 27 Sep 2006 09:20:12 -0500, Dan Luke wrote:

*Improper* LOP operating technique can harm cylinders, even cause
catastrophic failure by detonation.

Hmm. Detonation, if I follow all this correctly, yields lower EGTs. So
someone leaning by EGT could be fooled into thinking that all is well,
even while cylinders are being damaged. This is exactly the type of idea
I was missing; now I think I see.

But CHT goes up, right? Would it go up enough (ie. beyond 400) to raise a
pilot's concern?


http://www.avweb.com/news/pelican/182132-1.html

Pelican's Perch #43:
Detonation Myths

We've all been taught about detonation in piston aircraft engines. It's what
occurs when combustion pressure and temperature get so high that the
fuel/air mixture to explodes violently instead of burning smoothly, and it
can destroy an engine in a matter of seconds. Right? Well, not exactly.
AVweb's John Deakin reviews the latest research, and demonstrates that
detonation occurs in various degrees - much like icing and turbulence - with
the milder forms not being particularly harmful. Heavy detonation is
definitely destructive, and the Pelican offers some concrete data on how to
avoid it.
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