Question

10 In tropical region, an aircraft is flying at an
altitude of 10 km. At that altitude the
temperature is 40°C. What is the ambient
temperature on the ground?
(a) 24°C
(b) 40°C
(c) 30°C
(d) 20°C​

Answer 1

Answer:

b is the option is the correct answer

Answer 2

First of all, find the ISA (International standard atmosphere) temperature at 10 km or 33000 ft. Given that for every 1000 ft the temperature drops at 2 degree Celsius:

1000 ft ——— 2 degree Celsius

33000 ft —— x

x = 66

At sea level, the ISA temperature is 15 degrees Celsius. So, the temperature at 33000 ft is:

15 - 66 = -51 degrees Celsius

In the question the actual temperature at 33000 ft is said to be at -40 degrees and we know that the ISA temperature is -51 degrees. With that information we could find how much of a temperature deviation is there between ISA and actual prevailing temperature.

ISA deviation = Actual temperature - ISA temperature

ISA deviation = (-40) - (-51) = 11 degree Celsius.

So, the temperature is 11 degree Celsius hotter than ISA. Or we could also say that the temperature is ISA+11.

As I have mentioned before the mean sea level temperature is 15 degrees Celsius. If the conditions are ISA+11, then the prevailing ground temperature should be:

15 + 11 = 26 degree Celsius