Nav: "Wind mark up" or "Wind mark down"?

[Evo7]

Hi Chaps

I've just started working through Thom's Air Navigation book. In Chapter 4 he describes two different methods for doing triangle of velocities calculations with the Whizz Wheel - "Wind mark up" and "Wind mark down". Any strong feelings about which is the better one to learn?

[suction]

I've always used 'down' myself, but only because this was how it was initially demonstrated to me. I think I've used 'up' when practising examples from the likes of Mr Thom. I think my fuddled brain always found down a bit more intuitive - but maybe I'm weird :D

-S

[FlyingForFun]

The only thing you need to do for PPL is apply wind to a track to get a heading. For this, wind up is easier, since it doesn't involve jiggling the wheel around.

However, there are a lot of problems which can't be solved using wind up, which you'll need to learn for CPL/ATPL/etc, or might like to know just for interest. For this reason, my instructor insisted that I learn wind down. With a bit of practicing, the jiggling around takes no time at all - and I now find wind down easier than wind up, although this is only because I use it more frequently.

Another good hint for learning to use the wind side of the whiz-wheel is to draw the whole of the wind traingle on, not just the wind mark. This helps visualise exactly what you're trying to do. Obviously once you understand things a bit better, you can stop doing this.

As with all things, though, it's alway a good idea to do whatever your instructor recommends - that way, if you have any questions, he'll be in the best position to be able to help you out.


FFF
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[Evo7]

Thanks for the explanation FFF - I figured that there must be a reason for having two different methods, but Thom doesn't seem to give it. Wind down seems to make a bit more sense to me, so I'll stick with that. My Instructor will probably agree (hopefully) but I'm not going to see him for a couple of weeks so he's going to be stuck with it :)

I'm actually starting to like the CRP-1. Scary.... ;) :rolleyes:

[LowNSlow]

Like the posters above I found wind down more intuitive.

Good old CRP-1's dontcha just love em. Still use my first one although it is getting a bit creaky now. :D

[AerBabe]

I use wind down too. Like my pal FFF said, if you ever fancy doing a CPL or ATPL then that's the method you'll have to use anyway.

I have a slight problem in that my whizz wheel doesn't have a square grid region. If you haven't already bought one, watch out for this! There are ways round it though.

[HelenD]

I leant wind up for the Nav exam but later discoverd that all the instructors use wind down so I learnt that when I started doing Nav.

[Final 3 Greens]

Doesn't matter - either will work fine.

You pays your money, takes your choice.

:)

[Tinstaafl]

Use a 'CR' type circular whiz wheel - they don't use a slide - then the problem disappears! The CR types also simplify some of the Mach No. calculations.

I used my 3 3/4" CR for Oz, USA & UK ATPL exams without a hitch.

Bit more portable too & fits in most pockets...

[AerBabe]

So I need bigger pockets and smaller wheels? If only someone had told me that 18 months ago! :D

[Whirlybird]

If there's the smallest, remotest possibility that you might someday want to do CPL or ATPL exams, learn wind down now. One chap on my ground school course had learned wind up, and there's so much to do on those courses that I really felt for him, as this just added one thing more. Why make the exams harder than they already are?

[Aussie Andy]

Like HelenD I taught myself "wind up" initially - in my case because the "jiggling" had me worried - and got through the exam that way, but when it came to doing the actual Navex's I found my instructors all used wind down, and so when they were checking what I had done etc. they were all very keen for me to use the same method.

I now use "wind down" without even thinking about it. It just seems that itsa "wind down" world out there: don't fight it ;)

[criticalmass]

Used "wind Up" method on my ARC-1 for microlight nav and cross-country rating...but our nav/wind vector problems are very simple!

From what I read in the posts it looks like "wind down" is the better option for more serious work.

[Mark 1]

I favour wind up when calculating hdg & GS from a given track & TAS (the most common problem) as it correctly represents the vectors and no iteration is required.

I successfully got 96% in CPL flight planning using the appropriate method for the task.

The way to remember is wind up blows you to the centre dot from the wind dot - so track is under the centre dot and GS under the wind dot.
Wind-down blows you to the wind dot from the centre dot - so hdg&TAS is under the centre dot and GS&track under the wind dot.
Draw on your triangle of velocities onto the computer and all should be clear

[Noggin]

The Computer was designed to be used Wind Down, that way all the information printed on it is correct.

Like many things in life, you can use it upside down if you really want to!

[Evo7]

Thanks for the thoughts everyone :)

[john_tullamarine]

As someone else suggested above ... it doesn't matter which way you do the sums ... the answers are the same and the apparently reversed techniques are correct trigonometrically, or, at least, can be shown to be able to produce the correct answer .. provided you keep track of what you are doing.

The suggestion that one way is "professional" but that the other is "OK for private pilots" is just so much nonsense, unless there be some perceived elite clanishness involved.

You use whichever way you find more comfortable, although it is probably going to give you fewer troubles in the long run following the "conventional" way for the particular computer.

I would be more concerned that the individual pilot adopt a consistent set of techniques to minimise the likelihood of confusion and consequent error.

The Dalton (E6B) style of wheel provides a means to plot the W/V end of the navigation vector solution (navigation triangle).

The picture we get is the same as if we plotted the triangle directly onto a sheet of graph paper. The easiest way to think of it is to consider the instrument "floating" above the graph paper .. we look through the rose to obtain a view of the grid and the triangle, much in the same way as MS Windows provides a screen through which to look upon the "desktop" beneath.

The conventional solution requires that the centre of the compass rose viewer be located over the intersection of the TAS/HDG and W/V vectors. For this approach, when plotting the W/V vector, it is drawn "wind down" from the centre point.

However, because of the way the grid is drawn (r-theta, azimuth-range, angle-distance .. whatever descriptive term you might prefer) it doesn't matter if one positions the centremark over the other end of the W/V vector .. ie the intersection of the TR/GS and W/V vectors. This is what happens if the W/V vector is drawn "wind up" from the centre point .. actually it makes more sense to think of the W/V in this case as being plotted down from the end point to the centrepoint of the rose as the direction of the wind as plotted is exactly the same.

The instrument plots exactly the same triangle regardless of which approach is adopted. To see this more easily, try drawing an example on paper and then orient the paper with the instrument. To change from one technique to the other is just a matter of moving the instrument "over" the triangle to reposition the centrepoint while, at the same time, rotating it to remain aligned with the radial spokes of the grid.

The solution is read exactly the same for each case .. it doesn't matter which technique is used .. provided no careless mistakes are made, the correct answer results.

The suggestion that the unconventional technique can save a little effort is true, but rather illusory.

It may be helpful to look at the typical navigation problems which we routinely solve on the instrument.

(a) Given W/V, TR, and TAS .. find HDG and GS

The conventional "wind down" plot requires some iteration on the part of the pilot to obtain the solution. The alternative "wind up" technique gives the answer directly. Just be careful of confusing the decal markings.

(b) Given TR/GS and HDG/TAS .. find W/V

Either way works fine.

(c) Given HDG/TAS and W/V .. find TR/GS

The standard way works fine. If you use the "wind up" method, you end up having to do the same sort of iterative processing which the technique sought to avoid in (a).

(d) Given W/V and TR/GS .. find HDG/TAS

Similar to (a).

I really can't see that there is any significant advantage to be had in using the alternative method. If you take the small workload reduction in (a) and (d), you end up with the same sort of problem in (c). A matter of preference, I guess.


The CR works a little differently .. to save size .. which offers the advantage of its being able to be carried in one's shirt pocket.

To remove the need for a bulky slide, rather than plotting the standard (as in the Dalton solution) triangle, a line is drawn through the intersection of the HDG/TAS and W/V vectors and perpendicular to the TR/GS vector (or its extension). This results in a triangle to be plotted which is solved by a combination of figuring simple vector components (left/right crosswind and head/tailwind) and doing some basic trigonometry using the sine and cosine scales around the outside of the instrument (drift and effective TAS) .. the result is no need for a slide with the radial/range grid. It is, however, quite important to remember that we are solving a different triangle from the Dalton, although the end result is the same. A lot of people tend to get confused by this difference.

Unlike the Dalton, there is no need to plot the W/V vector as such and the idea of "wind up" and "wind down" is rather unnecessary. However, the distinction can be made by plotting the reciprocal of the conventional vector .. ie as if the wind is coming from the reciprocal direction but with the same magnitude (speed). Alternatively, this vector can be thought of in the same way as the Dalton situation in that it is just plotted, for curious inconvenience, downstream at a scale distance equal to the wind speed.

The result is that the unconventional plot ("wind down") causes the conventional CR triangle to be rotated 180 degrees about the intersection of the TR/GS and W/V vectors (the rose centre point regardless of which approach is adopted). The pilot must keep this firmly in mind .. while the resolved components of the W/V have the same magnitude the sense or direction, with respect to the instrument markings, is reversed. Provided that the pilot does not make any careless mistakes, the answers are going to end up the same regardless of which technique is adopted.

The standard problems listed above for the Dalton work fine for the CR, regardless of which technique is used. However, with the unconventional method, the mental housekeeping workload on the pilot increases significantly as does the likelihood of careless errors. For the life of me, I can see absolutely no advantage to be had in using the CR instrument in other than the conventional manner. If you want to do so, fine ... just be a little bit careful of the housekeeping workload .. but, surely, it is a bit like marching around the parade ground backwards ? .. a novelty but of little practical value.


The upshot is that the wind up and wind down approaches, for both computers, can be made to work fine for the typical problems we have to solve. I just can't see much point in using the unconventional technique for either instrument, especially in the case of the CR.

[Tinstaafl]

I still have my old Kane E6B type. When I used it for my CPL exams & flying training I found it easier to use Wind UP for the standard problem (to avoid the iterative process), and Wind DOWN for the rest.

A couple of years later I bought a CR & have preferred to use that for the last 15 years or so.

As an instructor I was quite happy to teach using the E6B wind UP or DOWN as well as CR methods.

[Huw Jorgen]

Does anyone actually use the Jepp in such a strange way ?

[Evo7]

Thanks for the detailed post, j_t :)

CPL/ATPLers - What sort of problems are so hard to solve wind up? The ATPL exams are unlikely but remain something of an ambition, so I'm trying to love wind down. However, I've been playing with both methods and currently make fewer mistakes wind up so I'm trying to justify the 'better' method to myself... :rolleyes: :)

[john_tullamarine]

Evo7,

Just a matter of doing it easy on the basis that doing it hard makes life less pleasant.

The decals on the instruments are designed for the instrument to be used according to the "standard" way of doing the things one does .. if the user chooses to do it the "other" way then he/she runs a much higher risk of making careless or unfortunate mistakes ... especially if the instrument is not used day in day out

For the cases I listed above, it doesn't matter .. you get the correct answer ... but why do it hard ?

Matter of risk assessment and personal choice in my view ...

[DOC.400]

Wind down here............

DOC