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

"john smith" wrote in message
...
[...]
For takeoff, the turbo should maintain sealevel power up to 12,000 feet
MSL, so full rich or slightly leaned mixture would be used on takeoff. I
think I would still lean for best power prior to releasing brakes for
takeoff.

You need to use full rich to keep the exhaust temperature down. With the
turbocharged engine I normally fly, in my airplane, about a third of the
fuel is used just for cooling (30 gph at full power, when theoretically only
about 20 gph would be needed for the 270 hp). The turbocharger controller
ensures that I am getting best power, without any fiddling with the mixture
at all. Even in an aircraft with a manual wastegate, one would ensure best
power using that control, not the mixture.

Pete

"Jeff" wrote in message
...
is this a turbo charged engine also?

Is what a turbocharged engine also? Both the engine that John Smith is
talking about and the engine that I am talking about are turbocharged, as we
both stated in our posts.

I have taken off with a DA of 8800 ft, full rich and not had a problem in
my
T-arrow I use full rich on take off and landing, as my POH says to do.

Have you landed with a DA of 8800' with the mixture full rich? On my
airplane (and apparently John's), the engine would stop on rollout. That
said, maybe you have a superior fuel system on the Turbo Arrow, or perhaps
the engine is just somehow inherently more immune to overly rich mixtures.

Pete

In article , 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?

My best advice is to go to www.avweb.com and read all of John Deakin's
articles on engine operation. These are gems of wisdom that every
flight instructor should have in their kit.

Somewhere I read an article that related that many aircraft
carburetors/injectors are not properly set for idle.

How does it idle? 500 rpm is the bottom end... Another 25 - 30 rpm may help
if it is idling rough...

On the issue of full rich, if you are landing at a low altitude airport then
progressivley enriching the mixture in the descent,arriving at full rich on
short final, makes sense, as the air density in the manifold will be
reasonably high, even after the turbo has spun down and is not boosting
much...
But, if you are landing at an altitude airport, then the throttle pulled
back will allow the turbo to spin down, same as for low altitude airports,
but the intake manifold air density will be low thin and full rich may
lead to a flame out - especially if you have to hit the throttle for a
missed approach, wind shear, etc... Full rich with full throttle is likely
to cause a stumble/stall at that point.... I would tend to keep it
reasonably lean during descent and approach to avoid plug fouling and to
keep it warm, only going to the 'appropriate' takeoff setting on short
final, which is not necessarily full rich at higher altitude airports...
You have already done your homework and know how far in to put the mixture
on short final for the airport you were at... For takeoff, I would run up
to 1800 rpm and lean for best power, knowing that full throttle will enrich
the mixture further, automatically... Just watch your manifold pressure and
cylinder head temps during climbout and richen slightly if needed...
denny

"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.

FWIW here's my TR182 experience. Of course the engine in
a TR182 is a very different beast from a T182T (carburetted
rather than injected, and turbo-normalized only, never boost above
31").

Full rich for takeoff, regardless of altitude, at 31" MP.
Lean to around 18 GPH (1350 or so TIT) with power reduction
to 25" at around 1000 AGL.

Lean to 1450 TIT for cruise.

Descend without further adjustment - TIT remains steady.
I've never experienced rough running in this situation.

Full rich as part of GUMPS check prior to takeoff, in
case of go-around.

John

"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

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?

yes that was the question, I did not see where you said yours was a turbo
charged also, must have over looked it.

yes I have landed to refuel with the DA at 8800 ft.

Is it superior - beats me, I just follow my POH and havnt had a problem yet.

Peter Duniho wrote:



Is what a turbocharged engine also? Both the engine that John Smith is
talking about and the engine that I am talking about are turbocharged, as we
both stated in our posts.

I have taken off with a DA of 8800 ft, full rich and not had a problem in
my
T-arrow I use full rich on take off and landing, as my POH says to do.

Have you landed with a DA of 8800' with the mixture full rich? On my
airplane (and apparently John's), the engine would stop on rollout. That
said, maybe you have a superior fuel system on the Turbo Arrow, or perhaps
the engine is just somehow inherently more immune to overly rich mixtures.

Pete

maybe a stupid question, but if its going to quit on you when you go full
rich on landing, then dont it also risk the chance of quitting if you go
full rich on a go around?
unless its just the high power that keeps it running and idle is what
kills it.

wrote:

Yes. The mixture was too rich.
This is a common problem with big-bore engines when operated
above 3000 MSL.

What we teach at Colorado Pilots Association is to set the
mixture to 15 GPH as you enter the pattern at (near) cruise
power. That way the engine continues to run on the ground. :-)

Of course, if you do a balked landing, you MUST push the mixture
full in after you increase the power for the go around.

Barry Klein wrote:
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

Best regards,

Jer/ "Flight instruction and mountain flying are my vocation!" Eberhard

--
Jer/ (Slash) Eberhard, Mountain Flying Aviation, LTD, Ft Collins, CO
CELL 970 231-6325 EMAIL jer'at'frii.com WEB http://www.frii.net/~jer
C-206 N9513G, CFII Airplane&Glider, FAA-DEN Aviation Safety Counselor
CAP-CO Mission&Aircraft CheckPilot, BM218 HAM N0FZD, 197 Young Eagles!

In article , Jeff
wrote:

maybe a stupid question, but if its going to quit on you when you go full
rich on landing, then dont it also risk the chance of quitting if you go
full rich on a go around?
unless its just the high power that keeps it running and idle is what
kills it.

Go around on approach (depending on height AGL), you will still have
some air under you and it is amazing how fast your hand will push that
mixture lever forward.

Rick Durden wrote:
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

Thanks! So then if I think I'm capable of remembering to push
in the mixture on a go around there is really no need to enrich
the mixture prior to landing. FWIW, I'm good about aggressively
leaning once I'm off the runway.

--
David Rind