Why does an engine tend to perform better at sea level then it does at high altitude?

As power decreases with altitude, the thrust moment of the operating engine lessens, thereby reducing the need for the rudder and it’s countering yaw. So at Sea Level the Vmc is the highest. The higher the density altitude, the lower the Vmc.

How does altitude affect jetting?

The general rule for jetting is to drop one main jet size for every 2,000 feet of elevation increase.

Why must a carburetor supply a rich mixture during idle?

Why must a float-type carburetor supply a rich mixture during idle? Because at idling speeds the engine may not have enough airflow around the cylinders to provide proper cooling. (1) The mixture used at rated power in air cooled reciprocating engines is richer than the mixture used through the normal cruising range.

How does altitude affect ignition timing?

Your ignition timing is probably the most critical and the easiest to adjust for altitude. The reason being is that in thinner air you have a little less compression pressure causing the fuel mixture to burn slightly slower. To compensate for this, your timing should be advanced about 8 to 10 degrees.

Why don’t carburetors work at high altitudes?

The simple reason is that high altitude changes the density of air, but not the density of fuel. Most simple carburetors use a simple venturi design that mixes air and fuel by VOLUME. But, the correct air/fuel mixture must be based on MASS, not Volume. If the air/fuel Volume is correct at sea level, it will be too rich at altitude.

Why is fuel too rich at high altitudes?

If the air/fuel Volume is correct at sea level, it will be too rich at altitude. This is because a given volume of air will have less Mass at high altitude, while a given volume of fuel will have the same Mass at high altitude.

How do Aircraft carburetors work?

Aircraft carburetors have a mixture control to “lean” the volume of fuel to the volume of air, and are then able to maintain the correct air/fuel ratio at all altitudes. Leaning is not done to counter carburetors that do not “preserve the fuel-air ratio over changing altitude”.

Why is air compressed at sea level but not at high altitude?

But at sea level the air is compressed more than at 30,000 feet. As the airplane, or you, go up in altitude the air gets “thinner”, or less dense. Less dense means that the air is not as compressed. For some volume of air, 1 cubic foot for example, higher pressure air will have more air molecules than lower pressure air.