There is a general perception that an airline pilot should be very good at maths in order to be good at controls. 

This is actually true, but the pilot does not need to excel in it to become a good one. What is rather more important is how quickly can the pilot calculate so he can take decisions on the go. Being adept in arithmetic calculations like addition, subtraction, multiplication and division is good enough to calculate how much fuel is required for a flight or to decide the rate of ascent or descent .

To get an Air Transport Pilot’s Licence (ATPL), knowledge of trigonometry and Pythagoras theorem are necessary ,but these are not required to be used on a daily basis. There are, however, software and devices that can run the number for pilots. Once the pilots understand them, they just need to choose the correct formula, plug in the number and get the answers. 

What is commonly used is the application of the three times table to calculate, using a rule of thumb, if the aircraft is too high or low when descending. This involves the calculation of removing the last three digits of the altitude and multiplying the remaining number by three, to roughly calculate how many miles the pilot needs to descend. For example, at 30,000 feet, the pilot needs to multiply 30 by three, which gives 90. This means at 30,000 ft, he would need roughly 90 nautical miles to descend, assuming a constant three-degree glide path. But these calculations need to be worked out in the head quickly. 

Another application that the pilot needs is weight calculations. For an aeroplane to fly, it cannot weigh more than the amount of lift it generates. Each plane has a known empty weight and everything that is onboarded like fuel, passengers, luggage, and cargo should be added to the empty weight. The final number should be at or below the maximum takeoff weight as per the aircraft manufacturer and listed in the pilot’s operating handbook. 

Interesting, isn’t it? But then there are no re-takes. The pilots have to get their Maths right each and every time. (Source: and