Figure 1-9 Density Altitude Effects on Aircraft Performance

CHAPTER ONE

AVIATION WEATHER

HIGH TEMPERATURE OR

LOW TEMPERATURE OR MOISTURE

MOISTURE

Lower Air Density

Higher Air Density

Higher Density Altitude

Lower Density Altitude

Decreased Thrust and Lift

Increased Thrust and Lift

Longer Takeoffs and Landings

Shorter Takeoffs and Landings

Figure 1-9 Density Altitude Effects on Aircraft Performance

113.

ALTIMETER ERRORS

Pressure

When an aircraft flies from one place to another at a constant indicated altitude (by referencing

the barometric altimeter), it is flying along a surface of constant pressure. Figure 1-10 shows the

path of an aircraft as it follows such a constant pressure surface, done by flying a constant

indicated altitude. As the sea level pressure on the surface decreases (all other conditions

remaining the same), the whole column of air aloft is lowered, causing an aircraft flying at an

assigned MSL altitude to descend to a lower AGL altitude. Only by updating the reference of the

altimeter setting can this potential problem be eliminated, and a more constant AGL altitude can

be maintained.

Figure 1-10 Path of Aircraft Flying a Constant Indicated Altitude with Decreasing Surface

Pressure

1-12

General Structure of the Atmosphere, and Atmospheric Temperature and Pressure