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.

"john smith" wrote in message
...
[...] Had you need to do a go
around, the cruise mixture would have been sufficient for a full power
go-around.

You do understand that he's talking about a turbocharged engine, right?
Generally speaking, full rich is the correct mixture setting for a
turbocharged piston engine, for full-power takeoffs regardless of altitude.

Pete

"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!

My airplane, with a Lycoming TIO-540, will do the same thing at high
altitude airports if the mixture is set full-rich prior to touchdown.

Operationally, I simply leave the mixture alone during descent. Given that
descents are usually made at reduced power, theoretically I could even lean
the mixture during the descent (opposite of what you'd normally do with a
normally aspirated engine at power settings near cruise), but I just keep an
eye on the turbine inlet temperature and normally no change in mixture
setting is required to keep the TIT in the ballpark of 1500 F.

During a go-around, it is critical that I remember to push the mixture
full-rich, but since it is just as critical that the engine not stop until I
am actually done flying the airplane, this is an acceptable trade-off.

I also need to keep the mixture lean while taxiing, otherwise I get fouled
plugs. I asked my mechanic about both issues (since they seem related) and
he verified that the idle mixture is correct for my installation. It just
runs rich at or near idle power unless the mixture is manually adjusted. At
higher density altitudes, idle mixture is so rich it will flood the engine
and make it stop.

[...] 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.

I assume you mean you just did this as a test during taxi, and that you
returned the mixture to full rich before takeoff?

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

Sounds about right, but I don't know the specifics for that engine. It
might be that it's supposed to be higher. I would ask the mechanic
maintaining the aircraft if he has the engine manual for the engine
installed, and then you can read in that what the actual numbers should be.

Pete

Thanks everyone for the info. This was my first flight in a turbo, my
experience is with non-turbo 182s.
My buddy was in the left seat for the landing, 6750', about 50 deg F. I'm
not sure what he did for final approach,
may have gone to full rich.

Ragards,
Barry
----- Original Message -----
From: "Peter Duniho"
Newsgroups: rec.aviation.piloting
Sent: Sunday, January 11, 2004 3:01 PM
Subject: Turbo 182: correct mixture for final approach at high altitude?


"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!

My airplane, with a Lycoming TIO-540, will do the same thing at high
altitude airports if the mixture is set full-rich prior to touchdown.

Operationally, I simply leave the mixture alone during descent. Given
that
descents are usually made at reduced power, theoretically I could even
lean
the mixture during the descent (opposite of what you'd normally do with a
normally aspirated engine at power settings near cruise), but I just keep
an
eye on the turbine inlet temperature and normally no change in mixture
setting is required to keep the TIT in the ballpark of 1500 F.

During a go-around, it is critical that I remember to push the mixture
full-rich, but since it is just as critical that the engine not stop until
I
am actually done flying the airplane, this is an acceptable trade-off.

I also need to keep the mixture lean while taxiing, otherwise I get fouled
plugs. I asked my mechanic about both issues (since they seem related)
and
he verified that the idle mixture is correct for my installation. It just
runs rich at or near idle power unless the mixture is manually adjusted.
At
higher density altitudes, idle mixture is so rich it will flood the engine
and make it stop.

[...] 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.

I assume you mean you just did this as a test during taxi, and that you
returned the mixture to full rich before takeoff?

Yes, we did this just to get a smooth idle for taxi. We went full rich on
the takeoff roll and climbed out to 8500' nicely.
I just mentioned this to demonstrate how lean we needed to go to get to the
best power setting at 1200 rpm.


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

Sounds about right, but I don't know the specifics for that engine. It
might be that it's supposed to be higher. I would ask the mechanic
maintaining the aircraft if he has the engine manual for the engine
installed, and then you can read in that what the actual numbers should
be.

Pete

I have a turbo arrow, my POH also says full rich on take off. Thats what
I use on take off and landing. I do not adjust the miicture untill I am
at cruise altitude.
how come you didnt just set it to full rich like the book suggested?

you either have a fixed or an automatic wastegate, the automatic
wastegate will use the turbo as needed. the key is to fly as the book
says to fly and not try to out guess the airplane.

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

is this a turbo charged engine also?
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.

Peter Duniho wrote:
My airplane, with a Lycoming TIO-540, will do the same thing at high

altitude airports if the mixture is set full-rich prior to touchdown.

Operationally, I simply leave the mixture alone during descent. Given that
descents are usually made at reduced power, theoretically I could even lean
the mixture during the descent (opposite of what you'd normally do with a
normally aspirated engine at power settings near cruise), but I just keep an
eye on the turbine inlet temperature and normally no change in mixture
setting is required to keep the TIT in the ballpark of 1500 F.

During a go-around, it is critical that I remember to push the mixture
full-rich, but since it is just as critical that the engine not stop until I
am actually done flying the airplane, this is an acceptable trade-off.

I also need to keep the mixture lean while taxiing, otherwise I get fouled
plugs. I asked my mechanic about both issues (since they seem related) and
he verified that the idle mixture is correct for my installation. It just
runs rich at or near idle power unless the mixture is manually adjusted. At
higher density altitudes, idle mixture is so rich it will flood the engine
and make it stop.

[...] 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.

I assume you mean you just did this as a test during taxi, and that you
returned the mixture to full rich before takeoff?

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

Sounds about right, but I don't know the specifics for that engine. It
might be that it's supposed to be higher. I would ask the mechanic
maintaining the aircraft if he has the engine manual for the engine
installed, and then you can read in that what the actual numbers should be.

Pete