Engine mixture guidelines

Jose wrote:




In real airplanes there is a lag. Lean it out slowly.

The initial lean should be very quick. It's called the "Big Pull."
Fine tune as slow as you need to. You need to avoid the red box, that's
why you lean quickly.

The initial lean should be very quick. It's called the "Big Pull." Fine tune as slow as you need to. You need to avoid the red box, that's why you lean quickly.

I've only heard of a red fox, not a red box. What is that?

In general, I lean to a bit richer than I ought to be, and then after it
stabilizes, I lean from there. But if you overshoot, that's not good.

Jose
--
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What really happens when you go towards peak EGT is you're assuring a
pretty efficient burn inside the cylinders, the exhaust contains little
unburnt fuel and little oxygen. If you play a little with the mixture
when prop and throttle are firewalled you'll probably pick up some RPM,
even at low altitudes. It's especially noticable on hot days.

In cruise with constant speed props the prop pitch changes a little,
taking a healthier bite of the air so as to use the additional power.
CHT is a simple way of measuring what's going on -- it's telling you,
as you go from rich to lean, when you're getting the hottest -- call
that best -- internal temps. Since the fuel (I was taught) helps in
cooling, you want not to overlean so as to save the valves. That
statement probably deserves some research -- why not run schiometric
(I'm sure I mis spelled that) combustion? Does anyone know for sure?

For that matter, if you do get peak power at max EGT, why run on the
rich side? Wouldn't it make sense in terms of fuel economy to run on
the lean side a bit?

I know the dogma, what I'm interested in is the justification. Any
powerplant engineers out there?

Jose wrote:

The initial lean should be very quick. It's called the "Big Pull."
Fine tune as slow as you need to. You need to avoid the red box,
that's why you lean quickly.


I've only heard of a red fox, not a red box. What is that?



At and below 60% there is no red box, put the mixture anywhere you want.

At 65% power use richer than 100 ROP or leaner than peak.

At 70% power use richer than 125 ROP or leaner than 25 LOP.

At 75% power use richer than 180 ROP or leaner than 40 LOP.

At 80% power use richer than 200 ROP or leaner than 60 LOP.


As you transition from takeoff power to cruise power if you are going to
be LOP make sure you lean rapidly to the values listed for LOP ops.
Fine tune as necessary.

Newps writes:

The initial lean should be very quick. It's called the "Big Pull."
Fine tune as slow as you need to. You need to avoid the red box, that's
why you lean quickly.

The red box?

--
Transpose mxsmanic and gmail to reach me by e-mail.

Jose writes:

I suspect most MSFS simulated aircraft do not simulate engine damage
from improper leaning. They will simulate the fan quitting at idle
cutoff though.

Yes. Most types of damage are not simulated in MSFS aircraft, nor is
cumulative damage simulated (as far as I know).

Leaning the mixture beyond a certain point does indeed stall the
engines in the Dreamfleet Baron model I fly in simulation.

In real airplanes there is a lag. Lean it out slowly. A Cessna 182
manual I remember reading said that it should take about two minutes to
find the peak. This may also not be adequately simulated in
"entertainment level" simulators.

I see a lag in the simulator, also.

I've never heard "a full turn", though I have heard the less helpful
phrase "a bit". Not all airplanes have vernier controls, and I don't
think MSFS aircraft do either.

The Baron has controls similar to the real aircraft, that is, two
levers for mixture.

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Mxsmanic,

t does indeed stall the
engines in the Dreamfleet Baron model I fly in simulation.


Engines don't stall. Airplanes do.

--
Thomas Borchert (EDDH)

wrote:


Remember FULL rich for takeoffs and landings unless your flying at
Leadville, CO or some other really high altitude airport.

No. Lean above 5000 as a general rule. Some aircraft, like my Bonanza,
has a scale on the fuel flow instrument that tells you where to lean to
for every takeoff regardless of altitude.

Newps,

No. Lean above 5000 as a general rule.


I would say 3000. But that's pretty much a matter of taste. What's
important is: we're talking density altitude!

--
Thomas Borchert (EDDH)

"Thomas Borchert" wrote in message
...
Newps,

No. Lean above 5000 as a general rule.


I would say 3000. But that's pretty much a matter of taste. What's
important is: we're talking density altitude!

--
Thomas Borchert (EDDH)

You are in agreement with the POHs for the C152 and Tomahawk, which are the
two that I recall at the moment. IIRC, that involved leaning to peak RPM at
full throttle--part throttle operation was another matter. One of them
specifically authorized 25 RPM lean of peak for reduced power operation,
such as transitioning at 60% power--which my rather old instructor refused
to believe even when shown!

Amusing but true. He was quite serious, and the same debate is still
raging--25 years later!!!

Peter