Okay I have always had 'auto-mixture' on, but I would like to be cool and have it OFF, so I need to know when to apply different amounts of mixture (Lean, full, ect) So any advise would be great

Mazza wrote on Feb 2^nd, 2010 at 4:02am:


For normally aspirated (Carburettor) Piston Engines the Mixture should be set Full Rich for take off, cruise, and landing.
(This also helps to cool the Cylinders).

For altitudes above 5,000 Feet ASL the Mixture can gradually be weakened to maintain the correct Petrol/Air mixture for to generate full power Power.
Slowly reduce the Mixture until the Engine starts to falter and run rough, then slightly increase until the Engine runs smooth again.
Observe the Engine RPM, and Suction Gauges...and note any change in airspeed.

Remember to apply Full Rich for landing...to keep the Cylinders cool to prevent engine overheating!

(A Weak Mixture generates heat!)

If taking off from an altitude higher than 5,000 Feet ASL remember to weaken the Mixture slightly for full power!

Paul...G-BPLF...FS 2004...and a packet of Dolly Mixture Sweets... ...!

...and don't forget to pull the Mixture Knob to Full Weak to stop the Engine(s)....!

(This will empty the Carburettor Fuel Bowl to reduce the possibility of an accidental Ignition Start).

...THEN switch off the ignition!

NOT just switch off the Ignition to stop the Engine(s) (Grounding the Magnetos).

....and don't forget to apply Full Rich to Start the Engine(s).... ...!

Paul...G-BPLF...FS 2004...ate all the Dolly Mixtures... ...!

..its fun, (and educational!), playing with the Throttle, Mixture, and Carb Heater controls...and observing the Gauges and sound of the Engine(s) to the response... ...!

ShaneG wrote on Feb 2^nd, 2010 at 11:09am:


Last year, I took a Warrior up into the mountains.. landed at Ingals field (KHSP). It was my first, high-density altitude takeoff in a 160hp airplane 

All you do is push your runup to near full power and then lean for peak RPM. With a constant-speed prop, it's more an 'ear' thing.. but the theory is the same.

ShaneG wrote on Feb 2^nd, 2010 at 11:09am:


THAT is quite the challenge. I attempted that with the 172. It takes a perfect mixture and a long runway for sure. I first threw in a notch of flaps, thinking in my flatland mind that it would help. It did not. More speed, less flaps, and I barely managed a takeoff. It is an excellent challenge to demonstrate mixture settings and high elevations.

With a fixed pitch prop, the answers about leaning the mixture at takeoff power until the rpm drops a bit, then enriching slightly to get the peak rpm, are right.

A constant-speed prop, however, will try to maintain the preset rpm. Lean until it starts sounding a bit rough, then enrich the mixture to smooth it.

References to altitude should really refer to "density altitude," not height above sea level. The aircraft's operating manual should have information about proper leaning.

I've flown from Tucson, Arizona and Edwards AFB in the Mojave Desert. At those 2,300' msl fields, the density altitude easily hit 6,000' on a hot August afternoon.

Art

aeroart wrote on Feb 3^rd, 2010 at 6:57pm:



I'll quote myself from earlier in the thread 


Quote:

ShaneG wrote on Feb 4^th, 2010 at 6:59am:

That's what makes it such a challenge, or course! How do those little planes get there anyway? Up the hill in a truck no doubt.

Here are the three ways I have learned to lean a engine:

1. On run up, lean it back until the RPMs peak. (They will go up and as they fall off, stop.) Then push the mixture control back in to the peak. This is the method that we use at high altitude.

2. This one takes a little time. Fly at full rich, and slowly pull the mixture control out until you get the highest EGTs. This is your peak EGT. Continue to lean it out until you are 100 degrees below the peak EGT. This is very close, (but not exactly) maximum power. It will keep your engine cool without throwing unburned fuel out of the engine.

3. This is one to do only alone or with your copilot only. It may scare your passengers a bit! Start with a full rich mixture, and lean it out until the engine starts to run a tad rough, then push it in until you get a smooth running engine.

I hope this helps,
C170B