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gatt
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 Posted: Thu Jun 24, 2004 8:15 pm Post subject: dumb question?: Using the EGT gauge |
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The Cessna 172 I'm flying now has an EGT (exhaust gas temperature?) gauge on
it that I've never seen in the other aircraft I've flown. It has two needles
and a fixed indicator at about 75% that looks like a snowflake.
Anybody care to explain, or just point to a good aviation link, about how to
use it? My CFII has been activated for guard duty for two weeks so I'm
flying solo until then.
-c
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Brian C.
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| Posted: Thu Jun 24, 2004 8:59 pm Post subject: Re: dumb question?: Using the EGT gauge |
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| Quote: | The Cessna 172 I'm flying now has an EGT (exhaust gas temperature?) gauge
on
it that I've never seen in the other aircraft I've flown. It has two
needles
and a fixed indicator at about 75% that looks like a snowflake.
Anybody care to explain, or just point to a good aviation link, about how
to
use it? My CFII has been activated for guard duty for two weeks so I'm
flying solo until then.
-c
|
The EGT is useful in properly leaning the mixture. With power set, the more
you lean the mixture, the higher the EGT, until a peek is hit. Beyond that
peek, the EGT drops, and eventually the engine looses power. You usually
lean to peek EGT, the enrich the mixture enough to lower the EGT back down 2
notches.
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SpammyFriends
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| Posted: Thu Jun 24, 2004 10:19 pm Post subject: Re: dumb question?: Using the EGT gauge |
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On Thu, 24 Jun 2004 16:59:37 -0400, "Brian C." <farside6 (AT) aol (DOT) com>
wrote:
| Quote: | The Cessna 172 I'm flying now has an EGT (exhaust gas temperature?) gauge
on
it that I've never seen in the other aircraft I've flown. It has two
needles
and a fixed indicator at about 75% that looks like a snowflake.
Anybody care to explain, or just point to a good aviation link, about how
to
use it? My CFII has been activated for guard duty for two weeks so I'm
flying solo until then.
-c
The EGT is useful in properly leaning the mixture. With power set, the more
you lean the mixture, the higher the EGT, until a peek is hit. Beyond that
peek, the EGT drops, and eventually the engine looses power. You usually
lean to peek EGT, the enrich the mixture enough to lower the EGT back down 2
notches.
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We have one. You'll learn the sweet spot for EGT with it. I still
lean until rough, then enrich 2 turns.
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gatt
Guest
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| Posted: Thu Jun 24, 2004 10:19 pm Post subject: Re: dumb question?: Using the EGT gauge |
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"Brian C." <farside6 (AT) aol (DOT) com> wrote
| Quote: | The EGT is useful in properly leaning the mixture. With power set, the
more
you lean the mixture, the higher the EGT, until a peek is hit. Beyond that
peek, the EGT drops, and eventually the engine looses power. You usually
lean to peek EGT, the enrich the mixture enough to lower the EGT back down
2
notches.
|
Excellent! You have contributed to my knowledge. Thanks and good flying!
-c
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charles.k.scott@ddddartmo
Guest
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| Posted: Mon Jun 28, 2004 2:44 pm Post subject: Re: dumb question?: Using the EGT gauge |
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On Thu, 24 Jun 2004 15:19:44 -0700, "gatt"
<gatt (AT) livefromtheclocktower (DOT) com> wrote:
| Quote: |
"Brian C." <farside6 (AT) aol (DOT) com> wrote
The EGT is useful in properly leaning the mixture. With power set, the
more
you lean the mixture, the higher the EGT, until a peek is hit. Beyond that
peek, the EGT drops, and eventually the engine looses power. You usually
lean to peek EGT, the enrich the mixture enough to lower the EGT back down
2
notches.
Excellent! You have contributed to my knowledge. Thanks and good flying!
|
The Cessna Training Manual actually calls for the airplane to be
leaned below peak EGT. They state that you should reach cruising
altitude, pull the mixture out until the needle peaks, keep pulling it
till it begins to lower, then turn the mixture in until you've
achieved 25 to 50 degrees below the peak you saw. The guage in our
172 had two needles, one that you could set as a guideline, the other
recorded ETC. It also said that you could lean until the rpm began to
drop, and then lean further till you got a specified rpm drop. I
forget exactly what that rpm drop is supposed to be. Could be as much
as 150 rpm. This also would be leaning past peak, even if you did not
have an EGT guage.
In the POH for the Cessna I trained in, it also stated that you could
lean the engine out during climb. In this case you leaned for maximum
rpm, which is another way of saying leaning for best power, which is a
setting on the rich side of peak. You can be obsessive about this and
lean every 30 seconds or minute, or just lean once in a while.
One more way of leaning during the climb is to note the EGT
temperature during the takeoff, and lean to that temperature as you
climb. That way you will never overlean during the climb as the
mixture is always overrich for full power (with the mixture full
forward, sea level) and as you climb and the air thins, the mixture
becomes more rich which has the effect of cooling off the EGT. So
leaning during the climb simply restores the mixture close to the
takeoff mixture setting, if you adjust to the takeoff temperature.
During local airwork training we did not bother with leaning, I only
learned about that when we were headed out on cross country's. My
instructor was reluctant to go into it in a big way, he taught the
"lean till it stumbles then richen it out till it didn't" routine.
I noticed that when descending, if the mixture was full rich, that EGT
guage was bottomed.
Corky Scott
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charles.k.scott@ddddartmo
Guest
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| Posted: Mon Jun 28, 2004 5:00 pm Post subject: Re: dumb question?: Using the EGT gauge |
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On Mon, 28 Jun 2004 10:44:14 -0400, [email]charles.k.scott (AT) ddddartmouth (DOT) edu[/email]
wrote:
| Quote: | The guage in our
172 had two needles, one that you could set as a guideline, the other
recorded ETC.
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Rats, I hate it when I do that. I meant to say EGT.
Corky Scott
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smackey
Guest
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| Posted: Tue Jun 29, 2004 3:02 am Post subject: Re: dumb question?: Using the EGT gauge |
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"gatt" <gatt (AT) livefromtheclocktower (DOT) com> wrote
| Quote: | "Brian C." <farside6 (AT) aol (DOT) com> wrote
The EGT is useful in properly leaning the mixture. With power set, the
more
you lean the mixture, the higher the EGT, until a peek is hit. Beyond that
peek, the EGT drops, and eventually the engine looses power. You usually
lean to peek EGT, the enrich the mixture enough to lower the EGT back down
2
notches.
Excellent! You have contributed to my knowledge. Thanks and good flying!
-c
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The asterisk "*" doesn't really have anything to do with the EGT
except for calibration. Instructions are to lean until peak at a
certain altitude/power setting, then using a small screwdriver, tune
the needle to the asterisk. This keeps it on the guage rather than
running out of room at the top of the scale at certain
setting/altitudes. The guage has no temperature markings, as I'm sure
you've noticed. The large marks are usually at 100 degeree intervals,
and the small ones at 50 degrees, of course. The method is to lean to
peak on the needle, then either enrich or lean from peak by a certain
number of degrees, depending on which school of thought to which you
subscribe.
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