Wind up or wind down method

[Deputy Dog]

Hi Guys,

I am a wind up type dude cos that was the first method I came across in Thev Thom when learning. It is also the easiest (I think) having looked at others.

Almost everyone else I know uses wind down, including the confuser ?

Is it more accurate ? :confused:

Is it the preffered method for ATPLers ?

I will change to wind down if there is a good enough reason.

[FlyingForFun]

DD,

Yes, there is a good reason for using wind down. Wind up is fine for calculating heading from desired track, which is all you need to do for PPL. But when you come to the ATPL exams, you'll need to do other calculations, e.g. calculating your track from your heading, calculating the wind from your heading and your track, etc. etc. etc. These can only be done with wind down.

So learn wind down now, and save yourself a lot of hassle later on! It's only slightly more complicated to calculate heading from track, but it'll make things much easier later on!

FFF
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[African Drunk]

I agree for ATPL wind down.

[Tinker]

If you choose to use the wind up method, you do need to understand what is going on if you plan on continuing to your atpl's. For me it is the quickest and most fool proof method for wca, but if you do not really understand it, it can easily throw you for those calculations (which thankfully are in my distant past) that require wind down.
I would say if you don't intend to continue past ppl, stick with what you know, if you are aiming for your atpls try the other method and see what suits you. I prefered wind up, like you I learned that method first,I didn't have any problem differentiating between problems requiring wind up or wind down but we are all different and you won't know what floats your boat till you try.

[john_tullamarine]

It doesn't really matter which approach you adopt .... but consider the following

(a) if you do it differently to the way the instrument is designed, the decals are inappropriate to your method which increases the risk of making silly mistakes

(b) what you gain here .. you lose there.... meaning that there are some very minor workload gains by shifting from one technique to the other. However, by the time you get sufficiently proficient to keep track of what you are doing and not make mistakes .... it would have been far easier just to learn and develop proficiency in the standard technique for the particular instrument.


The story is -

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.

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.

[Field In Sight]

I used the wind up method before trying the wind down method. Then if I hadn't flown for a while I'd forget which one I used.

Now what I do has made it much simpler to understand.

1. Draw out a dummy triangle of velocities on a piece of paper. You will have to remember how the heading is affected by wind to produce the track. Make sure you use the standard 1,2 & 3 arrows to indicate each vector.

Then if you know the track (usually) then dot in the centre of the E6B is between the wind and the track vector.
I make sure I draw all of the vectors on the E6B so that it looks as if it makes sense.

Then as you have the full triangle you can see how everything is related and easily read off headings/groundspeeds etc.

As Hannibal of the A-Team said "Works for me".

[Deputy Dog]

Thanks for your excellent replies guys,

So doesn't seem that there is much difference in using one over the other. So long as you know what you are doing you will get the same answer and just as accurately. Is this a fair assessment ??

I am actually planning to the ATPL's and figured that now is a good time to change from wind up to wind down if there was one or two really good reasons to use wind down method.

I remember my PPL instructor once saying that wind down allowed you to do more calculations at ATPL level but I did not imagine at the time I would ever consider going commercial, so stuck with wind up. Anyway, I found I could do exactly the same calculations with wind up as down with LESS fuss.

When I ask people now, especially ATPLers, they all seem use wind down. Is this cos the examples in the notes use this method ??? Is it more accurate or not ?? why do people recommend one over the other ??

I actually know people who have passed ATPL's using crp1, using compressability equn's and calculator instead of new £70 + whizzey wheel. Does anyone recommend this !!??

Regards

DD

[Father Mulcahy]

Deputy

quote:

"I actually know people who have passed ATPL's using crp1, using compressability equn's and calculator instead of new £70 + whizzey wheel. Does anyone recommend this !!?? "

In the great scheme of a 30-40-50k frozen ATPL an extra 70 quid for a CRP-5 is not that much. I hear what you're saying, and in my ATPL Instruments/Navigation exams there were no compressability questions whatsoever... You pays your money and takes your choice. However the CRP-5 is much larger and therefore the dot of your pen will cover less of a spread of answers - some of the G Nav CRP-5 answers are really tightly grouped.

Re the Wind Up Method, Baz the Nav instructor at Bristol GS says, and i quote "Anyone who teaches the wind up method should be p&%sed on and shot, in the order."

There is a hell of a lot of wind side calculations in the Nav and Flight Planning exams you have to know your stuff, and not just the PPL finding heading/gs from wind/track/tas but wind finding, multiple drift lines etc. If the whole of the rest of the class uses wind down and the book gives all the explainations that way, why buck the trend ? If you're gonna swap to wind down, swap now, not two weeks before your exams during the brush up course.


Best of Luck

FM

[Send Clowns]

If you are ever intending to fly commercially do not even consider the wind-up method. It is difficult to relearn the opposite way, and in your CPL/ATPL General Nav course you will be taught wind-down. Some of the techniques are difficult and illogical wind-up, so you would be prone to errors. Of course in the classroom only one technique can be taught to the class, and this will be wind down.

In fact if taught correctly the wind-down method is no more difficult than wind-up, and makes more sense. Take the trouble to learn correctly now.

Best of luck - any problems drop me a line.

Send Clowns [Gen Nav instructor, BCFT]

[Tinstaafl]

You could always use wind up for the case you're already familiar with, and wind down for the others.

That's what I did for my CPL exams. I had no trouble recognising which problem needed which method. Nor did I have difficulty remembering the methods.

For IR & ATPLs (Oz, USA & UK) I used - and vastly prefer - a CR5.

[oxford blue]

The trouble with your recommendation, Tinstaafl, is that you're thinking like an airline pilot who doesn't do this crap anyway, and is only paying lip service to it in order to get a tick in the box.

You haven't thought it through as to WHY a professional navigator would use the CRP5 for real. Well, I'll tell you.

Having done his flight planning on the gound, our professional navigator gets airborne. He has found heading to fly from track off his chart and forecast wind. The problem is that that wind is for a regional forecast that covers the whole of (say) Northern UK, and a six-hour period.

After half an hour in the air, our professional navigator finds an (actual ) wind. He does it by comparing his Air Vector of Heading and TAS with his Ground Vector of Track and Goundspeed (from 2 successive fixes 20 minutes apart).

Now he has a wind which is much more recent and local than his forecast. It is over a period of only the last 20 minutes and over the area he has flown over for the last 20 minutes.

This is much better than the forecast. This is what's actually happening in the bit of airspace he's actually been flying in over the last 20 minutes or so. He would be much better off using this to decide which heading to fly to maintain track.

The problem is, if he uses the method that you're advocating, he now has to re-plot his wind the other way on the CRP5. He done his wind-finding downwind, and he now has to write all this stuff in his log, then rub out his wind mark, then re-plot upwind in order to calculate his new heading. This is a no-no. If you can calculate the desired heading from track wind-down, you don't even have to write down what the wind is (that bit's just log-keeping).

All you have to do is use the wind mark on your CRP5 from the wind you've already found and then you can calculate the new desired heading to fly (using the wind-down method). No REAL navigator would chop and change depending on which task he was trying to do. The only reason that you give the advice that you do is that you've never had to do this for real. You see it purely as an academic exercise to get through an exam.

Well, it isn't. And I (and obviously John Tullamarine as well) believe in trying to turn our students into professional pilots, not exam-passing tick-in-the-box merchants.

Wind down every time for all three operations:

1) Finding heading from track

2) Finding track from heading.

3) Wind finding from comparison of Air Vector and Gound Vector.

[Alex Whittingham]

You misjudge Tinstaafl, Oxford Blue. I suspect he knows exactly what he's saying and I agree with him.

Your scenario of the 'professional navigator' is 30 to 40 years out of date and has minimal relevance to the skill sets required of a modern pilot. It matters not a jot whether pilots use the wind down method, the wind up method or cast dice. As long as they consistently get the right answers I don't care and they probably don't either.

JT's point was exactly that. Both methods have their merits and both will give the same solutions.

Having said that, if I were to train a student from scratch I would certainly use wind down because the markings on the CRP5 for heading and drift are correct for that case and not for wind up. If he's already learnt the wind up method and knows what he's doing we can work with that and we should get the same results.

[Deputy Dog]

Thanks again guys for your replies. Wind down method has the edge because as Alex W says CRP5 markings for hdg, drift are correct for that case and not for wind up.

Trev Thom says basically use whichever unless someone recommends differently for a good reason.

I agree with Tinker, Tinstaafl and Alex in that I can use wind up for ease and be able to spot the wind down scenarios separately.

As regards CRP1/CRP5, probably see if I can use crappy 1 accurately enough before shelling out another £70+ on crappy 5. I intend to do ATPL's distance learning instead of the £65,000 + option so £70+ is still alot of money for something you may not really need.

I believe you can buy bags of disposable paper crappy 5's in the states for a fraction. Can you get those here ?? I'm interested for one ...... ;) ;)



Regards

DD

[Tinstaafl]

Oxford Blue,

I'm quite familiar with the in-flight tasks you mentioned and used to teach them.

Never the less, I still find it easier and a lower over all workload to put a new spot on the graticule once, than to jigger around the graticule every time I resolve the most common navigation triangle problem.

And yes, I am considering the task(s) of the navigator. The pilot navigator.

BTW, when was the last time a pilot needed to use this skill ie calculate actual wind then apply it to the remainder of the leg/flight? Not once in nearly 20 years have I had to use it (apart from exams, of course). I've chosen to do it as an alternative to many other navigational solutions to maintain my skills or just because I was bored.

[Send Clowns]

The problem, DD, is that there are functions on the CRP-5 that are not available on the CRP-1. Compressibility calculations, for CAS/TAS above 300 kts TAS and fuel weight/volume convertions for various specific gravities as examples. Both are possible by formulas and electronic calculator, but the CRP-5 is quicker, simpler, requires less learning and will get the same answer - remember the JAA answers are calculated on a CRP-5.

The CRP-5 is a Pooley's product, so I doubt that the paper examples are CRP-5s. They are most likely generic flight computers. I would stick to the real thing - it is expensive, but I have 4 good flight computers (2 RN-issue of different sizes, Jeppeson aluminium and a CRP-5) and the CRP-5 really is the best.

Good luck.

[Deputy Dog]

Having now sucessfully completed my ATPL theory (hadn't even started when I posted the original message) If you are doing your brushups with Bristol then it is better to bite the bullet and stick with Wind Down method for no other good reason than it is the method used in class. Easier not to "rock the boat" as it were.

Regards

DD

[Tinstaafl]

Well done on passing them!


Reading this post again, it struck me as quite interesting the polarity between UK & USA/Oz about the general type of flight computers used. Wonder why that is?

UK is staunchly slide based, USA CR circular type. Oz used to be slide based some 20 odd years ago but has rapidly changed to CR.

Just an idle thought...