Cessna 340 High Altitude Operations (Please Help)

Dear Colleagues.

My name is Stefano Rota. I am from Quito, Ecuador. I am a commercial pilot, I did all my flight school in ICARO FLIGHT ACADEMY www.learn2fly.aero here in Quito. Currently, i have a chance of flying as a PIC a Cessna 340 for a friend of mine, based here in Quito. I used to fly this as a copilot but I didnt know that much back then and last, I was just being an assistant for COMS etc.

Any way, the fact is this is an airplane which I am aware is not adequate for operating at this altitude (Takeoffs) and I want to get some things clear before we start. So if possible I would like to receive a few tips, from people who have operated C340 or similar C421, C414 at different elevations. The airplane is getting maintenance done in TAMIAMI and were gonna ferry the plane down with the instructor, and do a few flight here in the highland as the airplane handles totally different.

Quito, is the capital, airport based at 9,228 FT. Yes, you saw right, NINE THOUSAND FEET. Now. I have been reading the POH and the procedures and all, and I have a doubt. This C340 has two Continental 6 Cyliner 310HP engines. In my flight school we used to fly Cessna 172's with 210HP engines, and for example we used to reduce the mixture for startup, basically to ZERO. On the run up we would regulate it based on RPMS, etc, and in takeoff we would get 12gph. And then we would never touch it again.

NOW, on the 340, I was reading the manuals and the takeoff procedures say MIXTURE RICH. Now. I have some doubt. As we are taking off from 9 thousand feet I find it hard to believe the mixture needs to be rich! And based on my experience thats not right. The books don't say anything regarding high altitude takeoffs so Im lost. Is it correct to take this plane off with the mixtures rich regardless of the altitude? In the MAXIMUM CLIMB checklist you see the following

1. Power 2700 Full Throttle Below 20,000FT
2. Airspeed 108
3. Mixtures FULL RICH BELOW 20,000FT
LEAN AS REQUIRED ABOVE 20,000FT
........

This is the only LIST or thing I could see regarding Maximum Climbs etc, but I will keep on looking. So, whats your take on this guys? I believe id be killing my performance with the engines at that rate of fuel flow. But thats why I am asking. We used to take it off like that, we had a long takeoff roll, but it had a good rational climb. But tell me what you think

Thanks in advance, and please, let me know, and I will have more questions. Thank you.

Stefano Rota

On 1/30/11 4:58 PM, UIO Spotter wrote:
/snip/
NOW, on the 340, I was reading the manuals and the takeoff procedures
say MIXTURE RICH. Now. I have some doubt. As we are taking off from 9
thousand feet I find it hard to believe the mixture needs to be rich!
And based on my experience thats not right. The books don't say
anything regarding high altitude takeoffs so Im lost. Is it correct to
take this plane off with the mixtures rich regardless of the altitude?
In the MAXIMUM CLIMB checklist you see the following

1. Power 2700 Full Throttle Below 20,000FT
2. Airspeed 108
3. *Mixtures FULL RICH BELOW 20,000FT
LEAN AS REQUIRED ABOVE 20,000FT*
.......

This is the only LIST or thing I could see regarding Maximum Climbs etc,
but I will keep on looking. So, whats your take on this guys? I
believe id be killing my performance with the engines at that rate of
fuel flow. But thats why I am asking. We used to take it off like
that, we had a long takeoff roll, but it had a good rational climb. But
tell me what you think
/snip/

Stefano,

The big difference here is that the 340's engines are turbocharged, and
have altitude compensated fuel injection pumps. The engine in the 172XP
you flew did *not* have either of those features. To make a long story
short, Cessna's published leaning procedures are correct, i.e full rich
below 20,000 ft., for full power takeoffs and climb. This is because the
turbochargers will provide the engines with Sea Level manifold pressures
up in to the 12-15,000 ft. range, and the injection pumps will
automatically lean for best full rich performance above those altitudes.

Happy Flying!
Scott Skylane

Scott, you made my day! THANK YOU! Finnaly some one took the time to give me a logical explanation. I for some reason never thought of the turbochargers! Makes so much plain sense! Thanks and I owe you big time!

On Feb 1, 9:43*pm, UIO Spotter wrote:
Scott, you made my day! THANK YOU! Finnaly some one took the time to
give me a logical explanation. *I for some reason never thought of the
turbochargers! Makes so much plain sense! Thanks and I owe you big time!

--
UIO Spotter

In order to get book performance, you will need to verify that you are
getting
correct manifold pressure and fuel flow on every takeoff. If the
system is
not in good repair, it could easily not give takeoff power at 9000'.

Takeoff distance will still be quite a bit longer than lower
elevations. And
you need to use accurate speeds for landing... it will look really
fast out
the window.

We practice at Leadville, CO elevation 9927' 6500 feet length.

Bill Hale Loveland CO BPPP instructor

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