By doing the exercises 4.58, I don't understand why the calculation is different on question 3 and 4?
They are looking the max time over the airfield. But question 3 , we find the start up fuel first, question 4 start up fuel-taxi fuel -fix reserve.
Anyone would help me?
In Question No 3 you are holding over an aerodrome and therefore you do not require the 15% variable reserve for holding fuel. Simply find the minimum fuel required to do the flight if flight fuel is 53 gallons (79 gallons). Compare this with the actual fuel you have at start-up. All of the margin fuel you have over and above the 79 gallons required may be burnt holding.
In Question No 4 you are doing a search and it is your company policy to carry 15% variable reserve for the search fuel as well (see statement at the beginning of the exercise). So take out all the reserves before you begin - (total fuel - fixed - taxi) ÷ 1.15 = total flight fuel available. Take the transit fuel out of this and you have the fuel available for the search.
