Mixture Control Smarts
The mixture control adjusts the mixture of fuel and air, for combustion characteristics in aircraft engines.
If too much fuel reaches the combustion chamber for detonation the mixture setting is 'rich."
If too little fuel reaches the combustion chamber for detonation the mixture setting is "lean."
A "rich" mixture" will use more fuel and, generally, have a cylinder head temperature "cooler" than a "lean" mixture".
To stop the idling engine, after landing, and before shutting down the plane to leave it, you pull the mixture control all the way out. The very mixture will starve the engine and cause it to stop.
Now for the fun and safety issues. In this blog I will cover two that may save a life or two.
Sometimes when you taxi up to a small terminal a child may dart out from the waiting area to great you. They can't see the rapidly rotating propeller.
No matter where you are, pull out the mixture control and shut off the magnetos. That may or may not stop the engine. If it does stop the engine you may have prevented a very tragic accident.
Do not do anything until the child and the parents have safely set their offspring behind the safety fence. Then you can resume the procedure to park the plane.
Second safety issue is carburetor icing. In a normally aspirated engine the vanes that regulate the amount of air/fuel mixture may ice shut. When a gas expands rapidly the surrounding environment cools. If there is moisture in the air the actual temperature may reach below 32 degrees F and the moisture may change state to ice and starve the engine. This results in a sputtering engine on its way to stopping.
Lean out the engine quickly until it backfires. The backfire may dislodge the ice buildup and the engine will begin to run again.
Your instructor can elaborate on carburetor icing with you in a ground school setting or show the proper technique in flight.
Net effect, you can find your airport and land. Safety at last.
