Unknown winds
- Thread starter ZL340B
- Start date
z987k
Well-Known Member
Like figuring out what the headwind and crosswind component are given a wind direction and a runway?
drunkenbeagle
Gang Member
Easy, it is just a bit of trigonometry. I'm assuming that you have a known wind direction and speed, and want to fine the component headwind and crosswind. The E6B is just a polar plot of sine/cosine.
First, you need to find the angle of the crosswind relative to the runway or your direction of flight. Subtract one from the other.
Mostly, you are going to care about calculating crosswind components. Easiest way is to just memorize sine function for a few key angles.
sin(0) = 0 (no x-wind)
sin(30) = 0.5
sin(45) = 0.707
sin(60) = 0.866
sin(90) = 1 (straight head wind)
Knowing this, you can interpolate in your head and be within a knot or two all of the time, which is good enough. The mental math will be less accurate when it is near a straight headwind, but it is also less critical then - who really cares much whether it is 2 or 3 kt crosswind component?
drunkenbeagle
Gang Member
A
Adler
Guest
Just look at a lake and read the water.
Cessnaflyer
Wooooooooooooooooooooooooooooooo
But I fly in the Atacama.
Sorry, I should have been more clear; it's part of the CAX exam.
You're given:
True Course
True Heading
True Airspeed
Ground Speed
and from that, you are supposed to determine the wind direction and velocity.
I am indeed using the Jepp CR computers and unfortunately, there's not much help here as most people use the E6B.
Thanks for your help.
You're given:
True Course
True Heading
True Airspeed
Ground Speed
and from that, you are supposed to determine the wind direction and velocity.
I am indeed using the Jepp CR computers and unfortunately, there's not much help here as most people use the E6B.
Thanks for your help.
drunkenbeagle
Gang Member
Eh, you know what I meant. But hopefully those two cases should be obvious (to everyone but me!)
I figured it was a typo.
I try to teach my students the following:
20/30
30/50
45/70
>60 assume 100
Meaning that if the wind is different from my heading by 20 degrees/about 30% of the wind is a crosswind. etc. Anything greater than 60 just assume 100%
So, with a 10 knot wind:
20/30 =3 knot crosswind
30/50: = 5 knots
45/70 = 7 knots
60 = 8.6 knots, close enough to 10 knots from a performance/how is it going to handle/ etc for a low time pilot.
Life saver! Thanks guys for all the help! Appreciate the 'rule of thumb' methods you guys also mentioned; will surely come in handy in the cockpit.
When I first got my ppl and was doing a cross country, I tried to calculate winds with my wiz wheel. I figured out that was a pain while trying to fly an old 152 with no AP or GPS. I then learned what I have posted above and coupled that with the TLAR method.
ElihuSmails
Well-Known Member
I learned a slightly different rule of thumb for the x-wind.
3/5
5/7
7/9
In other words:
30deg = 50%
50deg = 70%
70deg = 90%
The mnemonic that helped it finally stick was "A .357 costs $5.79". Dumbest thing I ever heard, but I suppose that's why it worked.
3/5
5/7
7/9
In other words:
30deg = 50%
50deg = 70%
70deg = 90%
The mnemonic that helped it finally stick was "A .357 costs $5.79". Dumbest thing I ever heard, but I suppose that's why it worked.
Rocketman99
Frozen Guppy Manipulator
In UPT we were taught the simple rule of thumb:
>30 - 1/2
>45 - 2/3
>60 - 3/4
Works on wind components and other things like calculating your lead point for a turn on course using standard rate turns.
>30 - 1/2
>45 - 2/3
>60 - 3/4
Works on wind components and other things like calculating your lead point for a turn on course using standard rate turns.
TFaudree_ERAU
Mashin' dem buttons
All you need to know about wind is that you are supposed to ask tower for a wind check at least three times from final approach fix to touchdown.