i am not talking about throwing away the charts etc,i can asure you i have more conventional gadgets to plan the prog with,the whizz wheel doesn't have batteries granted,but if you input the wrong figures,therefore,it also follows you will get the wrong output,or am i missing something
The main thing is that there is some process taking place, you drawing the drift onto the wind side of the calculator, twisting it round, thinking which way you need to twist it, probably looking at a chart to double check your thinking.
With an electronic calculator or computer program, you can just push a few buttons and get an answer without seeing the process which took place so it is much easier to end up with a gross error (180 degrees out, wind applied the wrong way etc).
Having said that, I had one student who would frequently mis-use a protractor ending up with a 180 degree error, or sometimes 90 degrees, or apply the wind from the wrong direction (thinking the bearing was where it was going) leading to similar gross errors.