If you have 375 lbs of usable AvGas and need 50 lbs for non-cruise flight, how long can you cruise to meet night VFR requirements?

To determine how long you can cruise while ensuring you meet the night VFR (Visual Flight Rules) requirements after reserving a portion of your fuel for non-cruise flight, you first need to establish the amount of fuel that will be available for cruising.

You start with 375 lbs of usable AvGas and you need to set aside 50 lbs for non-cruise operations. Thus, the amount of fuel available for cruising is calculated as follows:

Available fuel for cruising = Total usable AvGas - Fuel required for non-cruise flight

Available fuel for cruising = 375 lbs - 50 lbs

Available fuel for cruising = 325 lbs

Next, to find out how long you can cruise with 325 lbs of fuel, you need to know the fuel burn rate of your aircraft in pounds per hour. For instance, if you assume a typical burn rate for many light aircraft is around 10 lbs per hour (this value can vary, so it's important to know the exact burn rate for the aircraft in question).

To calculate the duration of the cruise, you would use the following formula:

Cruising time (in hours) = Available fuel for cruising / Fuel burn rate per hour

Cruising time (in hours