...cut
Matt Prather wrote:
Hi Paul,
How are you doing these days??
I think John Deakin and George Braly demonstrate that the operating
mixture that Lycoming recommends (25-75 deg ROP) is hotter for the
engine
than a 100deg LOP operating point which is possible on many properly
injected Lyc or Cont. If the mixture distribution in a Lyc or Cont is
good enough that all of the cyls reach Peak EGT at the same mixture
setting, operating LOP is a very viable alternative. Just don't run it
within that hottest window, beit ROP or LOP (like you said).
Regards,
Matt-
VE N34RD, C150 N714BK
I am doing fine. Thanks for asking.
I think that is quite possible. I also think what Lycoming has in mind is
if you are at cruising altitude and you are leaned 100 degrees LOP when
you descend and forget to richen [lean] the mixture the engine will go to peak
EGT and burn the valves or ruin the head. One must always think out of the
box and take every possible scenario into consideration. We as engineers
still screw up because there is always someone out there that will do
something you never expected them to do knowing what you know. In other
words the correct operations you take for granted.
If it is always on the rich side it will just get richer when you descend.
All you need do is screw up once and you are out a couple of thousand
dollars the next time the annual comes around more than making up for
the few gallons you saved by running LOP.
Fortunately we don't have to worry about that. The rotary does not care
what the mixture is because it has no exhaust valves and the rotor housing
won't melt unless you are running an electric water pump :)
BTW I was flying with a group of people in C172s around Australia. The
so-called
leader (Lang Kidby I think) of the group was buying the gas. He ragged me
all the time about burning more gas than everyone else. I was aware of
Lycoming cautions
and I do forget to check the mixture when I descend every now and then. I
was running
rich of peak. I would rather not have the engine drop a valve over the
outback.
That probably makes me a bad pilot. Well I got even with him. I made
an unscheduled stop and put 10 gallons extra in the tank on my own nickel
without telling him. You should have seen his face the next time he filled
up the C172 I was flying :)
Paul Lamar
...cut
Hi all,
there is another interesting article from "The pelicans perch" on avweb,
continuing the topic, from the "Pelican's Perch #42:
Lycoming Speaks About LOP", mentioned on a previos post:
http://www.avweb.com/news/columns/182045-1.html (Pelican's perch #8)
It is quite an eye opener if one learned the "other way" to fly flat
pistons.
However note, that Gami never preaches, but proofs their way and also
insists to specially train people to manage their engines with the Gami
equipment installed to really get all the benefits without detriments. If
you read the article you will see, that the recommended procedure right from
the start through shut down is quite different and sometimes
"horror"-inducing for the non-initiated!
Never the less, the engines seem to like it, so does your wallet!
Also note that Gami insists in a quality engine monitoring system - they
boost the JPI EDM engine monitor as their prefered one, but I guess any
good system will do.
I don't know to what extend the findings about how to run a flat six can be
taken over to the rotary, but it is interesting anyway. Though it seems the
main concern on the rotary would be EGT in contrast to CHT on the flat, LOP
seems to be a lot easier on the engine in general than ROP.
Thomas J.
Scenario: Pilot forgets to change the mixture.
Start Operation. Power ...... Fuel Air...... Mixture .. EGT
---------------------------------------------------------------
LOP ..climb .... Reducing ....Same decreasing leaner lower
LOP ..descend .. Increasing ..Same increasing richer higher
ROP ..climb .... Reducing ....Same decreasing leaner maybe the same due to reduced power.
ROP ..descend .. increasing ..Same increasing Richer lower
The combination of increased power with richer mixture and higher EGT
while descending is the valve killer while operating lean of peak.
OK we can now get off this subject as rotaries do not suffer from this
particular air cooled aircraft engine sickness.
Paul Lamar
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