At 20,000 feet, what is the standard temperature?

At an altitude of 20,000 feet, the standard temperature can be determined using the International Standard Atmosphere (ISA) model, which establishes a lapse rate of approximately 2 degrees Celsius per 1,000 feet of elevation in the troposphere. At sea level, the standard temperature is set at 15 degrees Celsius.

When ascending to 20,000 feet, the temperature decreases as follows:

1. From sea level (15 degrees C) down to 20,000 feet, which is 20 degrees of altitude in thousands (20), the temperature decreases by 2 degrees Celsius for every 1,000 feet.

2. Therefore, the decrease would be 20,000 feet x 2 degrees C/1,000 feet = 40 degrees Celsius.

3. Subtracting this from the sea level temperature gives: 15 degrees C - 40 degrees C = -25 degrees C.

Thus, at 20,000 feet, the standard temperature is correctly identified as -25 degrees Celsius. This understanding of the standard lapse rate and how to apply it is crucial for pilots and aviation personnel in Lighter-Than-Air operations, as it directly impacts flight planning and performance calculations.