whiz wheel

[deanofs]

can anyone tell me of ways to learn the whiz wheel, got the Thom book and had a ground school with the instructor too...trouble is I work logically and the damn thing does not appear to be logical at all.....
Ta:confused: :confused:

[FlyingForFun]

It's completely logical - Dean...

Do you understand vector triangles? Not on the whiz-wheel, just on paper? Make sure you understand the maths first, then try drawing the complete wind triangle on the whiz-wheel - makes a lot more sense that way.

FFF
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[Evo7]

I found that Practice :confused:, Practice :mad:, Practice :( worked. It took me a while, but it does get better :)

[piloteddy]

deanofs,

You could try going to this site and downloading a free Nav tutor programme.

http://www.pilot-training.co.uk/FREE_nav_tutor.htm

Its about 3MB's size so it may take a while to download, but it did seem quite good when I used it!

[john_tullamarine]

Is there any reason why the manual which ships with the whizz wheel is no good ? Those which I have seen give adequate examples of how the gadget works ...

[tomcs]

It really is a question of practice. The whole wheel is based around logarithmic scales and everything is based around the number 10 i.e log to base 10.

The wind side is much simpler but does require practise. The easiest is to put the center dot on the 0kt line and put the wind heading on the top detent. Then just put a pencil mark on the wind speed (the squared area not the semicircular area). Then simply take the dot to the IAS that you have planned for, say 95kts with the PA-28. And put the heading for the leg u r calculating into the detent at the top. This shows u where the wind is coming from in relation to the aircraft track. Then adjust for the drift (west is best and east is lest). The drift correction (deg) should be equal to the number of degrees that the pencil mark that u drew is sitting on.

And after that just read the pencil mark off on the speed scale to get the groundspeed that you will get due to the wind effects.

Hope this helps

AND keep PRACTISING!!!


Tom:cool:

[Tinstaafl]

I know a very effective shortcut to learning to use the whizwheel.

Trouble is it takes hours & hours & hours of practice to learn the shortcut.... ;) :D :D

[john_tullamarine]

Tomcs,

I concur that the outer scales are the standard C-D logarithmic scales found on any garden variety slide rule. However, which other scales on the wheel are logarithmic ? .... perhaps you use different whizz wheels to those with which I am familiar ?


I have to agree with Tinstaafl .. there are no shortcuts to most things associated with flying ... one has to put in an appropriate amount of homework ... and, it is a bit like bridge .. the more you practise, the better you get ...

[GoneWest]

Tomcs...

Shouldn't you put that dot over TRUE airspeed - not planned INDICATED airspeed??

[Whirlybird]

deanofs,

If the instructor didn't explain it logically, chances are he didn't really understand it himself. Many don't. Get another instructor to show you. The whizwheel is incredibly useful and worth the effort, really.

[Evo7]

J_T

I've come across a lot of confusing instructions about how to use the flight computer during my attempt to learn how to use it. The booklet that comes with Pooley's CRP-1 is OK for the calculation side but very poor for the wind side, while the section about the whizz-wheel in the Trevor Thom book is long-winded and overcomplex.

Best bet by far is, as Whirly says, to get your instructor to demonstrate it - you'll suddenly get this "I SEE" moment and you're there. It does take time and practice afterwards though, otherwise you forget it again... :)

GoneWest is right - the blue dot is always true airspeed

[john_tullamarine]

Evo7,

I haven't read either the CRP or Thom books to which you refer so I am not able to comment on that. I agree that a simple demo by someone does present the problem that it tends to go in one ear and out the other ... far better to find some good notes and do a bunch of examples ... then the techniques tend to stick a little better ...

Maybe I should write a book on the whizz wheel and cover all the equations which go into both sides of it and make a video of how it works ... then again .. probably no-one would be interested anyway. Certainly, it always has irritated me to see some of the simplistic and paternalistic nonsense in a few of the user manuals around .. if you throw out the dross, the basics tend to reduce to quite simple notes.

[tomcs]

Gonewest...the thing about IAS and TAS is dependant on the altitude at which you are intending on flying!! At the levels that we usually fly at between 2000-4000 feet the TAS is very much similar to the IAS. However the higher u go the bigger the difference.

Thats why I usually dont bother with the TAS. But I would if I was at say FL65-75

But strictly it is the TAS.

Tom

[Saab Dastard]

Deanofs,

To expand on the practical info that Tomcs provided earlier,

There are 3 vectors in the wind calculation:

Wind speed and direction
Heading & IAS (or more accurately TAS)
Track and ground speed

If you know 2 of these you can calculate the third, but remember that a vector has both magnitude and direction.

In the usual flight planning problem, the wind velocity vector is known (from forecast), but the other two are actually unknown, insofar as you will know your desired track but not the ground speed and you know your IAS but not your heading.

This is why the problem requires an iterative 2-step (or more) approach to solution - the "jiggle".

An approximation is made, based on the assumption that heading and track are initially the same. It is then necessary to enter the revised heading to refine / confirm the calculation. In strong winds or large angles between track and wind direction it may be necessary to do this more than once.

In effect you are solving the problem: given wind velocity, heading and IAS, what is your track and ground speed? You are assuming a value for heading, and then checking that the assumption is correct by solving the problem and ensuring that the answer is your desired track, and iterating as required until it does.

Also remember that you are always blown from heading to track, so if you are ever unsure about whether to add or subtract the drift, just look at the direction of the wind on the map and then see how it relates to your track line - which way will it blow your aeroplane, and will you need to increase or decrease your heading to compensate?!

Stick with it, it gets easier!

SD

[tractorking]

one of the things I learned in Xcountry planning
was to try to make all the checkpoints the same
distance if possible, ie:20mi so you dont have to
move the wheel at all or very slightly in flight.

mostly its just common sense when you think
about it, you just have to take a second and
make sure that the answer makes sense.