Calculations

This page was going to be purely about the Whiz wheel as I learn to use it, but I have decided to add some on-line calculators which you can either use to make the calculations for you or just use them to check your results on the whiz wheel while you learn how to use it.

Fuel weigh
Fuel weight is a simple calculation so long as you know the specific gravity (Sp.G) of the fuel, this also varies with temperature, however for the needs of a microlight pilot using MOGAS / Unleaded petrol the SpG is taken to be 0.711 and the formula is simply the number of litres * Sp.G = Kg

To do the calculation on a whiz wheel Line up the number of litres on the inner wheel with the Ltr point on the outer wheel (found at number 10) then locate the Sp.G Kgs and read the value that aligns with 0.711 on the outer wheel on the inner wheel.

Stones and Lbs to Kgs
The conversion is simply number of stones * 14 + the number of lbs, this gives the weight in lbs. To convert lbs to Kgs times the number of lbs by 0.453592.

To do this on the whiz wheel first we convert Stones to Pounds by doing 14 * number of Stones.

Rotate the inner scale until the index (number 10) is directly under the number to be multiplied.
locate the multiplier on the inner scale.
Look directly over the multiplier and find the answer on the outer scale.
Now add the number lbs the result of the above to give the total weight in lbs.

Now we convert lbs to Kgs:

Rotate the Inner scale until the number of lbs is under the lbs mark on the outer scale.
Locate the Kgs mark on the outer scale read the number of Kgs from the corresponding position on the inner scale.

 

Time for a given speed over the ground and distance

The formula for this is distance  / speed = time in hours

Example 150nm at 300 kns = 0.5 hours, to convert to minutes,  0.5hours*60mins in an hour=30mins.

To do this on the Whiz wheel

Rotate the inner scale Time index (located at 60) to your speed on the outer scale.

Find the number of Nautical miles on the outer scale and read the corresponding inner scale for the time it takes to travel that distance.