A rather tricky question for the scientifically minded

[blackknight]

Hi guys and gals, hope everything is going well, I got my PPL in august last year and after saving up some more money between applying for sponsorships i am doing some constructive flying time, ie navigation, however i find it to be a bit of a pain when i am planning my flights as i have to do them in a rush due to time constraints etc... I was thinking of investing in a little flying computer but already have a pocket pc running windows and more importantly Excel 2000, I want to know if anyonme knows of a formula that can work our:
DRIFT,HDG(True),G/S, from inputting the variables of W/V and CRS!

I can already convert to hdg(m) and HDG(c)
and do all the distance/time equations, i just need a little help with the more complex ones

Thanks

Blackknight

[Rusty Cessna]

Dear Black,

I must tell you that I don't know of a formula to work out this but there must be one, or else our whiz wheels wouldn't work. However, Drift, Heading, Track are al the same principles as the "boat" scenario we saw in our PPL nav books.

These things are quite simple to work out, you can either use the triangle of velocities method described in your book, or the basis that that derives from, which is force resolution which is physics. This is simply using trigonometry to resolve a set of forces into one vector quantity. You may be familiar with this if you a-level physics, but I don't know. Now my point is, I have a thing called "Modelus" which is a mathematical modelling program, and I have seen the "Boat" scenario on it, seeing as its all worked out by differentiation and simple equations, im sure there is a way to find the formula for these equations.

Sorry to drag the thread on with nothing concrete, but I will have a play tonight and see what I can do.
Rusty

[This message has been edited by Rusty Cessna (edited 21 February 2001).]

[ShortFinal]

Hey,

Try http://indigo.ie/~weston/weston_download.html , Should find what your looking for.

SF

[Cypher]

Hey Blackknight..

funny you should mention this.. I do have the formulae for what you want. Even works out fuel consumption. BUT they are not entirely accurate, usually 0.5 to 1 knot out, and plus or minus one degrees.

the formulae approximate a good old whiz wheel.. but I never bothered to tweak it. I only used it as a check. (I need to model the speed circles on the wheel, the formulae use trig to figure out the soltion)

I can download you the program I created on my mathematical calculator if you want it, or at least provide a more detailed explanation if you want it via email.

[taildragger2]

Here's an equation for you!


£65.50(CRP-5) + .99p(Pen) = Problem solved

:) :) :) :) :) :) :)

If this isn't ideal then try the vector triangle.

BUT---- "The plotting solution to the vector triangle is long and laborious. The solution is more easily obtained using a navigation computer(CRP-5)" PPSC Gen. Nav.

........Tailwinds.........TD2

[blackknight]

Cypher, if you can e-mail me the program i will be very grateful, i will tweak it myself a little and let you know any improvements

Blackknight

[batty]

If your intending on doing your ATPL exams then get used to the CRP5 since you need to know it inside out, once you can its just as quick as booting up the confuser.

[James#1]

With all respect Blacknight, If you do not know how to make these computations then in the intrests of saftey I would spend a little more time cracking the books and a little less flying until you have full knowledge of the tasks involved in pre-flighting!
There should be no time constraints that would prevent you from doing the pre-flight computations which as I am concerned are a prerequisite to any flight!
Good luck!

[Noggin]

Why do you have to make life so difficult? formulae for working out drift and heading! Whats wrong with some simple rules of thumb and a little mental arythmetic. You don't go to bed standing up in a hammock do you? Maybe you do.

[landedoutagain]

blackknight, email me what you want and ill explain the trig formula - its useful to know it cause it also helps doing polar stereographic calculations (that is what theyre called isnt it?) if like me you hate doing scale drawings!
for now though, i would suggest getting a handheld gps and noting down drift and g/s when you are flying and looking at it afterwards if you have time - its very handy to be able to estimate such stuff at short notice for diversions and so on...

[AffirmBrest]

Don't they teach trigonometry at school anymore?? That said, I've forgotten most of it but try the following:

The 'vector triangle' is worked out using the Sine Rule:

Sin A/a = Sin B/b = Sin C/c where a,b and c are the lengths of the triangle (G/S, TAS and Windspeed) and A,B and C are the angles opposing those respective lengths. The problem comes when resolving the angles inside the vector triangle with the bearings given (Wind direction, HDG and TRK). You need to write a suitable algorithim to work these out. Basically if you have any 4 variables you can work out the 2 missing values (Usually HDG and G/S).

You may need to use some other formulae - Cosine rules and/or pythagoras etc., but they all tie in together so a decent GCSE level textbook should provide all you need.

Sorry I can't be of more help but if you can program a computer you damn well ought to have reasonable trig! (I can't program a computer and have v. bad trig)

------------------
...proceeding below Decision Height with CAUTION...

[blackknight]

James#1,
Firstly I have my gotten my PPL, and secondly I am very literate in the art of the CRP-5, I also got 95% in my PPL NAV exam.

The reason I made this post is because if like me you are looking at doing some serious cross country flying, then planning all the heading, drift etc... can become a tad time consuming when you have to start using a different wind component every second or third leg. I intended to use this program merely as an aid, and also because it will help me to remain literate with the CRP-5 as well

Blackknight

[This message has been edited by blackknight (edited 22 February 2001).]

[batty]

If you have got your PPL on the way to getting sponsorship then, well done but keep using the CRP 5. 95% in the PPL Nav well done, I got 84% in the ATPL Nav and my CRP 5 nearly melted it was used that much. The more you use it the better it gets!(like many things in life!)It will also teach you rules of thumb to apply. You cant use formula in the exams you just dont have the time.
If you are just carrying on at PPL level then use any way you like as long as it gets the right answer.

[Jumbo Jockey]

May I highly recommend "Diversion Planning" by Martyn Smith, a very thin pamphlet containing all you need to know. And no, I am not Martyn Smith!

(Should be available from Transair)