Turbo 182: correct mixture for final approach at high altitude?

We took a newer 182 turbo to a 7000' elevation airport yesterday and
the engine quit at the end of the landing roll. I'm sure the mixture
was way too rich. It restarted without incident, glad we were on the
ground! We had the mixture set about 100 deg rich of peak TIT for
cruise at 9500. How should we have found the correct mixture setting
for power-off final approach, when the turbo is basically adding no
boost and we are at high density altitude? This is not addressed in
the POH. It does say full rich on takoff regardless of airport
elevation. Later that day, when taxiing for takoff, we set 1200 rpm
and leaned for peak rpm, mixture knob was out 1.5-2 inches to achieve
this.

When we returned home to 800' elevation, we checked the idle speed at
full rich, it was about 500 rpm, is this too low?


Thanks,
Barry

I'm not sure the engine quit because the mix was too rich. When you took off
you were boosting the engine to 31 inches (I assume) - effectively sea level
performance. That's why you run it full rich. There may be some other
problem here.

Michael



"Barry Klein" wrote in message
om...
We took a newer 182 turbo to a 7000' elevation airport yesterday and
the engine quit at the end of the landing roll. I'm sure the mixture
was way too rich. It restarted without incident, glad we were on the
ground! We had the mixture set about 100 deg rich of peak TIT for
cruise at 9500. How should we have found the correct mixture setting
for power-off final approach, when the turbo is basically adding no
boost and we are at high density altitude? This is not addressed in
the POH. It does say full rich on takoff regardless of airport
elevation. Later that day, when taxiing for takoff, we set 1200 rpm
and leaned for peak rpm, mixture knob was out 1.5-2 inches to achieve
this.

When we returned home to 800' elevation, we checked the idle speed at
full rich, it was about 500 rpm, is this too low?


Thanks,
Barry

Sorry - I read your initial post incorrectly - realize now you were talking
landing roll. I generally just keep adding a half turn or so to the mix
about every 1000 feet as I descend. By experience I know approximately where
the mix will be on the ground around Denver - about 1.5 inches out. Be ready
to push in the mix along with the power if you have to go around, however.

I added a placard and adjusted my checklist to add mix-full in to my takeoff
checklist. A few times I leaned for run up and proceeded to take off with
the mix an inch out - really affects the climb out.


Michael



"Michael 182" wrote in message
news:iGjMb.25464$Rc4.98379@attbi_s54...
I'm not sure the engine quit because the mix was too rich. When you took
off
you were boosting the engine to 31 inches (I assume) - effectively sea
level
performance. That's why you run it full rich. There may be some other
problem here.

Michael



"Barry Klein" wrote in message
om...
We took a newer 182 turbo to a 7000' elevation airport yesterday and
the engine quit at the end of the landing roll. I'm sure the mixture
was way too rich. It restarted without incident, glad we were on the
ground! We had the mixture set about 100 deg rich of peak TIT for
cruise at 9500. How should we have found the correct mixture setting
for power-off final approach, when the turbo is basically adding no
boost and we are at high density altitude? This is not addressed in
the POH. It does say full rich on takoff regardless of airport
elevation. Later that day, when taxiing for takoff, we set 1200 rpm
and leaned for peak rpm, mixture knob was out 1.5-2 inches to achieve
this.

When we returned home to 800' elevation, we checked the idle speed at
full rich, it was about 500 rpm, is this too low?


Thanks,
Barry

Barry Klein wrote:

How should we have found the correct mixture setting
for power-off final approach, when the turbo is basically adding no
boost and we are at high density altitude?

Did you enrichen the mixture between cruise and landing?
There should have been no reason to. As you reduce altitude and MP, the
mixture will enrichen with decrease in altitude. Had you need to do a go
around, the cruise mixture would have been sufficient for a full power
go-around.

Are you sure about this? I always have to enrichen the mixture as I decrease
altitude.

Michael


"john smith" wrote in message
...
Barry Klein wrote:

How should we have found the correct mixture setting
for power-off final approach, when the turbo is basically adding no
boost and we are at high density altitude?

Did you enrichen the mixture between cruise and landing?
There should have been no reason to. As you reduce altitude and MP, the
mixture will enrichen with decrease in altitude. Had you need to do a go
around, the cruise mixture would have been sufficient for a full power
go-around.

Michael,

What do you experience that causes you to have to enrichen your
mixture as you descend on your airplane? Are you descending while
carrying a very high power setting? I'm asking because I've flown
T182s and TR182s and have never run into a situation that required
enrichening the mixture during descent unless I leveled off at some
intermediate altitude and went to a relatively high power setting.

Otherwise, the only reason to enrichen the mixture during descent is
if the engine actually begins to run roughly. (See the POH which only
recommends enrichening if you experience engine roughness.) Most
people descend at 65% power or less, which means that it is impossible
to detonate the engine due to lack of heat and pressure, so it's
impossible to run it too lean (it will simply start to run rough and
then quit if you get it too lean, you won't hurt anything). Keeping
it leaned during descent helps avoid overcooling (if you believe in
shock cooling), helps keep the plugs from fouling and doesn't waste
fuel. In general, once you lean the engine for cruise on a T182 you
needn't touch the mixture control until you pull it to idle cutoff
after landing, or to go to full rich on a go around.

All the best,
Rick

"Michael 182" wrote in message news:KXjMb.26563$5V2.40699@attbi_s53...
Are you sure about this? I always have to enrichen the mixture as I decrease
altitude.

Michael


"john smith" wrote in message
...
Barry Klein wrote:

How should we have found the correct mixture setting
for power-off final approach, when the turbo is basically adding no
boost and we are at high density altitude?

Did you enrichen the mixture between cruise and landing?
There should have been no reason to. As you reduce altitude and MP, the
mixture will enrichen with decrease in altitude. Had you need to do a go
around, the cruise mixture would have been sufficient for a full power
go-around.

Rick Durden wrote:
Otherwise, the only reason to enrichen the mixture during descent is
if the engine actually begins to run roughly. (See the POH which only
recommends enrichening if you experience engine roughness.) Most
people descend at 65% power or less, which means that it is impossible
to detonate the engine due to lack of heat and pressure, so it's
impossible to run it too lean (it will simply start to run rough and
then quit if you get it too lean, you won't hurt anything). Keeping
it leaned during descent helps avoid overcooling (if you believe in
shock cooling), helps keep the plugs from fouling and doesn't waste
fuel. In general, once you lean the engine for cruise on a T182 you
needn't touch the mixture control until you pull it to idle cutoff
after landing, or to go to full rich on a go around.

All the best,
Rick

The POH for my TB-21 (turbocharged Trinidad) with a
Lycoming TIO-540 calls for putting the mixture full rich
prior to landing. Is that different from what most people
do with this engine?

--
David Rind

"David Rind" wrote in message
...
The POH for my TB-21 (turbocharged Trinidad) with a
Lycoming TIO-540 calls for putting the mixture full rich
prior to landing. Is that different from what most people
do with this engine?

What actual model engine does the TB-21 have? Just knowing that it's a
TIO-540 doesn't give us enough information to compare with our own engines.

The engine in my plane, a TIO-540-AA1AD, cannot stay running at full rich at
idle at high density altitudes, as I mentioned in another post. I put the
mixture to full rich before landing only when landing below 3000' or so (and
then only so that I am more prepared for a go-around...operationally, I wind
up leaning again after leaving the runway so that the plugs don't foul).

Pete

David,

I believe your POH does call for full rich prior to landing (but not
in the descent) in preparation for a possible go around. Otherwise,
there is no reason to enrichen it.

At very high altitude airports, landing with full rich mixture may
cause a rough idle or the engine may actually quit at the end of
rollout, but that depends on the idle mixture adjustment on your
engine.

If your engine runs fine at full rich at low power settings on the
ground, then there is no problem with going to full rich on final in
preparation for a go around. However, you may want to lean it while
taxiing (lean it a long ways so that it will simply quit should you
try to take off prior to going to full rich and it will remind you) so
as to help avoid plug fouling.

All the best,
Rick

David Rind wrote in message ...
Rick Durden wrote:
Otherwise, the only reason to enrichen the mixture during descent is
if the engine actually begins to run roughly. (See the POH which only
recommends enrichening if you experience engine roughness.) Most
people descend at 65% power or less, which means that it is impossible
to detonate the engine due to lack of heat and pressure, so it's
impossible to run it too lean (it will simply start to run rough and
then quit if you get it too lean, you won't hurt anything). Keeping
it leaned during descent helps avoid overcooling (if you believe in
shock cooling), helps keep the plugs from fouling and doesn't waste
fuel. In general, once you lean the engine for cruise on a T182 you
needn't touch the mixture control until you pull it to idle cutoff
after landing, or to go to full rich on a go around.

All the best,
Rick

The POH for my TB-21 (turbocharged Trinidad) with a
Lycoming TIO-540 calls for putting the mixture full rich
prior to landing. Is that different from what most people
do with this engine?

I'll check my POH - I tend to enrichen somewhat by the fuel flow on the
Shadin - maybe this is a bad habit. I'm sure I'm not over 65% on the
descent.

Michael

"Rick Durden" wrote in message
m...
Michael,

What do you experience that causes you to have to enrichen your
mixture as you descend on your airplane? Are you descending while
carrying a very high power setting? I'm asking because I've flown
T182s and TR182s and have never run into a situation that required
enrichening the mixture during descent unless I leveled off at some
intermediate altitude and went to a relatively high power setting.

Otherwise, the only reason to enrichen the mixture during descent is
if the engine actually begins to run roughly. (See the POH which only
recommends enrichening if you experience engine roughness.)