Hi, I'm confused with this one. My calculations are different!

I did a practice exam, question was "maximum distance aircraft can plan to fly".

NORMAL TAS.......................190 kt

ASYMMETRIC TAS...................110 kt

NORMAL FUEL FLOW.................120 lt/hr

ASYMMETRIC FUEL FLOW.............85 lt/hr

FUEL TANK CAPACITY...............680 lt

FIXED RESERVE 45 min CALCULATED AT CRUISE RATE.

VARIABLE RESERVE OF 10 percent OF THE TRIP FUEL.

START UP AND TAXI ALLOWANCE......15 lt

I got it wrong due to where I put the fixed reserve in the below calculations.

Your workings show we include the fixed reserve in the first bit and take off 10% as if a variable reserve had been added to the fixed:

Flight fuel available = (680 [full] - 15 [taxi] - 90 [fixed res]) รท 1.1 [var res] = 523 litres.

My workings assumed the "trip fuel" (on which the variable reserve is calculated) does

*not* include the fixed reserve, meaning we haven't added 10% to the fixed reserve so we don't need to take it off - so remove fixed reserve

*after* the variable reserve has been removed:

Flight fuel available = (680 [full] - 15 [taxi]) / 1.1 [var res] = 604 litres - 90 [fixed reserve] = 514 litres

This made a difference to the answer I chose

I guess assuming you're right, i'm wondering why we add 10% to the fixed reserve? Does that make the fixed reserve "trip fuel"?