Hi Bob,
In this question i noticed it states 122.7 ÷ 20.4 = 6.1 hours but when i run this equation on my calculator it comes up with 6.01 hours. I cross checked this on google and i still get 6.01.
If you then multiply 6.01 by the Ground speed of 178kt you would cover 1069.78nm which is quite a difference from 1085.8nm.
I also noticed that when taking off the final reserve for all equations in these exams you divide by 1.1
Is this the only way to do it for the exam? Because if i work out 10% of 100 for example and then subtract that from 100 i get 90, whereas if i divide by 1.1 i get 90.9 which can also change the final answer by quite a lot with bigger numbers.
Many thanks
If you take out the reserves and allowances from the total fuel on board, you are left with 110% of the trip fuel.
If you then divide that by 1.1 you get 100% of the trip fuel.
Using the ECHO for example, Assuming you had 128 litres when you dipped the tanks, when you take out the final reserve and taxi fuel you get (128 - 15 - 3 + 110 litres). That 110 litres represents 110% of the trip fuel. So trip fuel = 110 ÷ 1.1 = 100 litres.
That's not the same as finding 10% of 110 (which is 11) and taking it away from 110 (which is 99).
When you subtract the final reserve fuel and taxi allowance from the total fuel you are left with 110% of the trip fuel, so divide that by 1.1 and you get 100% of the trip fuel.
Ah yes i can see what you're saying now. Sometimes math isn't as obvious until you run the calculations in a few different ways. Thanks again
