Primarily for general aviation discussion, but other aviation topics are also welcome.
By Andy Lees
#5570
John's method is certainly simple and could work quite well for faster planes. The problem a beginner has with all these different methods is that he doesn't know the significance of figures like 1/6, 2/3,3/4 or even the significance of angles like 30,45, 60deg. Once someone shows you how to resolve vectors using sines and cosines, then all the mystery suddenly disappears. If you don't have that knowledge, then it is impossible to evaluate the different
methods of getting a groundspeed and drift angle for a given wind strength and direction. They all have their advantages and disadvantages. Without the elementary trigonometry, all those
methods are merely a series of instructions, which you are expected to memorise parrot-fashion and carry out with no understanding. This is exactly what I found 18 mths ago when I
started doing longer cross- countries after getting the PPL.
Now on to the really interesting question, finding the wind direction
and strength on the day, up there. As Irv Lee has pointed out, all these methods assume that you know exactly what the wind is doing. Most people seem happy to put their faith in the 214. I take it into account but don't trust it completely. I know of four ways of getting the wind vector. I'd be really interested to know if anyone out there can add to this.
1) The Whizz-Wheel-- fiddly to use in the cockpit, difficult to read, and easy to make a mistake.(needs a Groundspeed and associated
drift angle).
2) GPS- got to enter a 3 figure heading.-- fiddly, and for me a lot of head-down time.
3)Mental analysis and comparison of the drift component and the headwind component gives a fairly good estimate. Takes me a bit of time and feels like hard work. Not accurate enough for me because all subsequent calculations have in-built inaccuracy and the mental arithmetic makes liberal use of rounding up and down.
4) A specially designed Groundspeed/Airspeed chart made for the individual aircraft ( or identical type) and a measuring device to obtain the wind vector. I made this myself. Essentially it does the same as drawing out a triangle of velocities diagram in the cockpit. Needs a groundspeed
and associated drift angle. Head-down time 5 seconds. Accurate to within 2.5 mph or Kts and 2-2.5deg.
Providing the timing and monitoring of the drift angle on the first
leg of the course is done carefully, at average route altitude, then all the subsequent calculations using the sine/ watch face have been pretty well spot- on. The only reason I can think of, that it has worked so well for me is that the starting point, the wind vector is accurate, and not a guesstimate. The wind can change during the flight but because of the accuracy, you spot this very quickly. Any slight change in heading or groundspeed or both, and in 5-10seconds you've got a new wind vector from which to calculate everything else.
All this stuff might give the impression that I go flying in order to perform lots of mathematical calculations. Not so, I go flying to enjoy
the view over the countryside and like the poet, enjoy map reading.
I just want to find the method of navigation that gets the maximum result in the minimum of time(and understand it fully), so that I have time to look around and enjoy travelling by air. Why not GPS? It's just too easy and it teaches you surprisingly little. I found
it useful at first but as I got used to the visual tricks of the atmosphere and developed some "feel" for navigation, it hardly
got used. It's something to do with being in control. With the GPS,
I sometimes wondered who was the pilot. Electronics of any kind are let down by the displays. Yes, there have been recent improvements but they have a bit to go before they really have the reliability and clarity that the cockpit demands. Much more thought
has to be given to the keys and operating switches ie "guarding" prevention of inadvertant operation and ease of operation with cold gloved hands. I mention this with Richard B in mind who started this post. Good luck with the programming, but don't forget to programme the one on your shoulders. Any thoughts or observations ?
By Richard B.
#5571
Thanx all for the input.

There has vaired ideas and advice on the subject, all which I appreciate. I should have made it clearer that I wanted a formula so that I could do this stuff on the ground for my own thought experiments and would never actually use it while on the wing. In fact I would probably never use it for flight planning either because of how diffcult it is to hold an accurate heading within a few degrees, so the precision achieved in the calculation is really pointless.

However, as several have pointed out, it could be useful for newbies like myself to get a grasp of what is actually going on so as to make the almost automatic adjustments in the air come much more easily.

Thanks again,
-R.
By Steve Morley
#5573
I always found the triangle of velocities, drawn on a piece of paper gave me a good grasp of the fundamentals of being blown sideways.
By Andy Lees
#5574
I agree Steve. Nothing like a good diagram. As yet we don't have
the space for a chart room in our microlights and I can't help thinking that it would take us over the weight limit, so we have to fall back to the use of maths. It's a sort of shorthand code for solving abstract problems. Some of it, the most useful bits have been around for 2,000- 3,000yrs. Until recently I thought it's primary use was to give schoolboys a hard time but with taking up flying I'm beginning to find some use for it after all. Give it a try.
Did you know that, with this stuff you can actually find the height of a tree without climbing it?