Percent power altitude

Not exactly. It depends on whether the gauge is calibrated
to an exact temperature or whether the gauge is used only to
find relative peak and degrees above and below. It also
depends on where the probe(s) are installed. EGT has the
probes about 4 inches past the exhaust valves, TIT has THE
probe at the inlet to the turbocharger. ITT has the probe
located between two turbine wheels in a jet engine.

They all measure the temperature of the combustion process
and thus relate to the fuel/air ratio. But how that relates
to the engine operation will vary. On a turbine engine the
critical temp limit is the start temperature. But in a King
Air for example, some models have the temperature probe in
the tail pipe and some have it in the hot section. With the
tail pipe measurement location the start temp limit might be
only 400°C, but it could run continuously at 650° and in
reality, the engine might actually be at the same
temperature.


"John R. Copeland" wrote in
message ...
Beechcraft, for example, calls it "TIT" instead of "EGT".
Some others still call it "EGT" on turbocharged airplanes.
But they all mean the same measurement.

"Jim Macklin" wrote
in message ...
Very true. On a turbocharged airplane the EGT is
calibrated
and called a TIT [an a jet it is ITT or TPT]
The turbo has designed temperature limits and because it
is
rotating at 35,000 to 120,000 rpm it needs very good
strength to stay in one piece. It also needs to be cooled
at a moderate idle speed for 4-5 minutes to allow it to
spool down, cool off and have good oil pressure. A closed
throttle idle doesn't supply enough oil volume to cool the
turn bearing, and a fast idle, particularly a simple fixed
waste gate type won't let it slow down enough.

Bottom line, RTFM for the particular model and serial
number.



"John R. Copeland" wrote in
message
. ..
"Allen" wrote in message
et...

"John R. Copeland" wrote
in
message
.. .
Doug's advice about never leaning above a safe
temperature
is well advised, and it's exactly what I've followed
for
25 years.
In fact, I found that leaning to RAM's recommended
1550F
still results in a little exhaust-system distortion,
and
I've held to
1525F max for the last ten years or so, with better
results.

I believe their recommendation at 75% power is 100
degrees
rich of "peak",
not 100 degrees rich of 1650 degrees. Most engines will
peak at a
temperature less than 1650 degrees.

Allen


OK, let me try to rephrase what Doug already said
correctly...
*At the higher power settings*, say about 70% and above,
the peak EGT *will* rise above steel's softening
temperatures.
If your EGT gauge is calibrated for temperature,
never lean above 900C/1650F, except for very brief time.
Preferably, lean directly to the desired temperature and
fuel flow.
RAM recommends operating at 850C/1550F, but my experience
says
that's slightly too high, and I lean to about 25F cooler
than that.
My penalty is less than 5% additional fuel flow above
RAM's
figures.
Yes, avgas is expensive, but replacing exhaust parts is
expensive, also.

My engines certainly will peak above 1650F at high power
settings,
but not so when operated down around economy power
settings,
which would typically be below 65%.
I normally cruise my TSIO320s at about the 50% power
level,
and even there, my peak EGTs remain above my personal
target
of 1525F.

From my cockpit, I can see down through louvers in the
tops
of my
engine nacelles, into the areas around the turbochargers.
I've had passengers at night ask me why I have
yellow-orange
lights
turned on in the engine compartments. :-/
When you've seen your exhaust components glowing in the
dark,
you get a better appreciation of the stress they endure
hour
after hour.
They are more than red-hot, they are nearly yellow-hot.
Don't abuse your exhaust system any more than necessary.