What are the two discoveries during flight?

• A. Indicated altitude and pressure altitude
• B. True altitude and density altitude
• C. Absolute altitude and true altitude
• D. Density altitude and indicated altitude

Answer: (B)

The main idea here is how altitude is described and used in flight under varying air conditions. Two quantities you’ll determine to understand your actual position and how the aircraft will perform are true altitude and density altitude.

True altitude is your actual height above mean sea level. The altitude shown by the altimeter (indicated altitude) is affected by local air pressure and temperature, so it may not match your true height in nonstandard conditions. To know how high you really are above the Earth, you adjust for pressure and temperature to arrive at the true altitude.

Density altitude translates the current air density into an equivalent altitude in standard atmosphere. It matters because air density affects engine power, lift, and performance. You compute it starting from pressure altitude and correcting for the outdoor temperature; higher density altitude means thinner air and reduced performance, even if you’re at the same indicated altitude.

So, true altitude tells you actual height above sea level, and density altitude tells you how the air will affect performance under the present conditions. These are the two quantities pilots actively determine during flight to ensure safe terrain clearance and predictable performance.

Indicated altitude is what your instrument shows, and pressure altitude is the standard-atmosphere reference used for planning; they are not the pair that describes the actual height and performance under current conditions. Absolute altitude relates to height above the terrain, which is not the standard reference used for flight planning and performance assessments.