Extended full-power in small pistons

On 3-Jan-2009, "Viperdoc" wrote:

Likewise, Lycoming and Continental always gave some hand waving response
to
questions about running LOP, yet, Cirrus, with now many thousands of hours

of LOP operations now mandate operating in this realm.

So, a lot of what is considered "safe and prudent" operating may be more
of
an old wive's tale, and not supported by actual data.

You might want to read through this article:

http://www.lycoming.textron.com/supp...es/SSP700A.pdf

Scott Wilson

There is a lot of "may", or "can" in their article, but no data. On the
other hand, Cirrus as well as the folks at TAT actually present data,
something that Lycoming and Continental have yet to produce.

I suspect that both companies are not interested in doing any testing or
changing their many year old operating instructions in order to limit their
liability exposure.

On 3-Jan-2009, "Viperdoc" wrote:

I suspect that both companies are not interested in doing any testing or
changing their many year old operating instructions in order to limit
their
liability exposure.

You may be exactly right. Somewhat irrelevant for me, since my 1978 Cessna
172N doesn't have an EGT gauge or cylinder head temp gauges. My POH says to
lean until the tach drops 25 to 50 RPM, which I've read is supposedly
somewhere slightly lean of peak. My partners say they lean until the tach
drops off, then twist the mixture knob back rich a couple of turns. I do the
25 RPM drop-off method, but I've always been worried I might be causing
damage to the engine, based on what I've read in some of the on-line
articles people on this group recommended. Or maybe my partners are damaging
the engine by doing it their way, if not just wasting some gas. I wish
there was a way to be absolutely sure.
Scott Wilson

In rec.aviation.piloting wrote:

On 3-Jan-2009, "Viperdoc" wrote:

I suspect that both companies are not interested in doing any testing or
changing their many year old operating instructions in order to limit
their
liability exposure.

You may be exactly right. Somewhat irrelevant for me, since my 1978 Cessna
172N doesn't have an EGT gauge or cylinder head temp gauges. My POH says to
lean until the tach drops 25 to 50 RPM, which I've read is supposedly
somewhere slightly lean of peak. My partners say they lean until the tach
drops off, then twist the mixture knob back rich a couple of turns. I do the
25 RPM drop-off method, but I've always been worried I might be causing
damage to the engine, based on what I've read in some of the on-line
articles people on this group recommended. Or maybe my partners are damaging
the engine by doing it their way, if not just wasting some gas. I wish
there was a way to be absolutely sure.
Scott Wilson

There is; it is called an engine analyzer.


--
Jim Pennino

Remove .spam.sux to reply.

On 3-Jan-2009, wrote:

There is; it is called an engine analyzer.


--
Jim Pennino

Ah yes, the Holy Grail of operating an engine. Not in our budget
unfortunately; our airplane is completely original, including paint,
interior and the original Cessna avionics. The best thing about our airplane
is that we have a little less than 2600 total hours on it, and she's been
hangared all her life so she's in remarkably good condition. But, we need to
upgrade the radios and transponder before we start looking at engine
analyzers. Guess I should've been more clear; I wish there were a way to be
more sure of operating the engine properly without an analyzer. Thanks for
the thought, though!
Scott Wilson

In rec.aviation.piloting wrote:

On 3-Jan-2009, wrote:

There is; it is called an engine analyzer.


--
Jim Pennino

Ah yes, the Holy Grail of operating an engine. Not in our budget
unfortunately; our airplane is completely original, including paint,
interior and the original Cessna avionics. The best thing about our airplane
is that we have a little less than 2600 total hours on it, and she's been
hangared all her life so she's in remarkably good condition. But, we need to
upgrade the radios and transponder before we start looking at engine
analyzers. Guess I should've been more clear; I wish there were a way to be
more sure of operating the engine properly without an analyzer. Thanks for
the thought, though!
Scott Wilson

Unfortunately monitoring CHT and EGT on all cylinders is the only way to be
absolutely sure.

Monitoring a single cylinder IMHO is a waste of time and money.

Using the POH leaning method won't achieve either maximum power or
economy, but it will be close enough and it will be safe.

The other plus for monitoring all cylinders is if a problem is developing,
it will usually show up on the monitor before any other symptoms become
noticable.


--
Jim Pennino

Remove .spam.sux to reply.

wrote in message
...
In rec.aviation.piloting wrote:

On 3-Jan-2009, wrote:

There is; it is called an engine analyzer.


--
Jim Pennino

Ah yes, the Holy Grail of operating an engine. Not in our budget
unfortunately; our airplane is completely original, including paint,
interior and the original Cessna avionics. The best thing about our
airplane
is that we have a little less than 2600 total hours on it, and she's been
hangared all her life so she's in remarkably good condition. But, we need
to
upgrade the radios and transponder before we start looking at engine
analyzers. Guess I should've been more clear; I wish there were a way to
be
more sure of operating the engine properly without an analyzer. Thanks
for
the thought, though!
Scott Wilson

Unfortunately monitoring CHT and EGT on all cylinders is the only way to
be
absolutely sure.

Monitoring a single cylinder IMHO is a waste of time and money.

Using the POH leaning method won't achieve either maximum power or
economy, but it will be close enough and it will be safe.

The other plus for monitoring all cylinders is if a problem is developing,
it will usually show up on the monitor before any other symptoms become
noticable.


--
Jim Pennino

Remove .spam.sux to reply.

IIRC, that last was the primary benefit that was originally advertised long
ago.

Peter

wrote in message
.. .

On 3-Jan-2009, "Viperdoc" wrote:

I suspect that both companies are not interested in doing any testing or
changing their many year old operating instructions in order to limit
their
liability exposure.

You may be exactly right. Somewhat irrelevant for me, since my 1978 Cessna
172N doesn't have an EGT gauge or cylinder head temp gauges. My POH says
to
lean until the tach drops 25 to 50 RPM, which I've read is supposedly
somewhere slightly lean of peak. My partners say they lean until the tach
drops off, then twist the mixture knob back rich a couple of turns. I do
the
25 RPM drop-off method, but I've always been worried I might be causing
damage to the engine, based on what I've read in some of the on-line
articles people on this group recommended. Or maybe my partners are
damaging
the engine by doing it their way, if not just wasting some gas. I wish
there was a way to be absolutely sure.
Scott Wilson

I don't know about the 172N, but the manual for the 152 had a very similar
recommendation for lean operation--but it was stated for 60% power (and was
obviously appropriate for less than 60% as well).

What does your POH say about the power setting?

Peter

On Jan 3, 10:10 am, wrote:
You may be exactly right. Somewhat irrelevant for me, since my 1978 Cessna
172N doesn't have an EGT gauge or cylinder head temp gauges. My POH says to
lean until the tach drops 25 to 50 RPM, which I've read is supposedly
somewhere slightly lean of peak. My partners say they lean until the tach
drops off, then twist the mixture knob back rich a couple of turns. I do the
25 RPM drop-off method, but I've always been worried I might be causing
damage to the engine, based on what I've read in some of the on-line
articles people on this group recommended. Or maybe my partners are damaging
the engine by doing it their way, if not just wasting some gas. I wish
there was a way to be absolutely sure.

Lycoming says you can lean your normally-aspirated engine
anyway you like if you're at or below 75% power without damaging it.
See your cruise charts. Detonation is seldom any risk at 75% or less.

Dan

I have an engine analyzer in my twin, and it is extremely useful for
monitoring CHT on those hot days, as well as finding out the bad plug that
occasionally occurs on runup. I always run LOP in cruise, and can generally
get down to around 25gph at 8-10k and 174KTAS. I need to adjust my GAMI
injectors, since the cylinders all don't peak at quite the same fuel flow.

It may not be as useful in a 172, but for IO 470's or larger an dngine
analyzer may make more sense. On the other hand, I also have an AEIO 540
Lycoming, and even without GAMI injectors, the engine peaks symmetrically,
probably due to better fuel flow in the Lycoming versus the Continental.