Winds aloft

[av8trflying]

Gents with all knowing knowledge,

Can anyone give me a tip on how to work out winds aloft whilst in a climb at different heights?

I have asked around and i get varying answers with a lot being "I dont know"

cheers for your answers

[Arm out the window]

It's not exactly clear to me what you're after, but you can get the winds off the ARFOR and interpolate for intermediate levels, then there's the grid points wind and temps forecasts for higher.

If it's an estimate of what wind to use for a climb, I was taught to apply the wind 2/3 of the way up, because you'll spend proportionately more time there as the rate of climb reduces.

Then there's the so-called Ekman spiral which as I recall says that the wind backs with height, eg. if it's 180 on the surface it might go round to 160 by 5000 ft or something - obviously not always the case!

Dunno if any of that's any use, but good luck.

[AerocatS2A]

Why do you want to know?

For an exam you'd use the winds 2/3 of your cruise altitude for your initial climb. I suppose for an intermediate climb you'd just average the winds from the different levels if they're significantly different. In real life do what your company ops manual says, or if it doesn't specify, use something suitably conservative.

[flyhardmo]

I use a GPS :ok:
Works like a charm

[av8trflying]

Sorry guys should have been clearer.

I was after how to use the cockpit instruments or gps to work it out.

I have been told before that GPS is useful to estimate upper winds by evaluating groundspeed and track made good but i was wondering if someone could explain it to me.

Cheers

[RadioSaigon]

Have a look at the GPS Book of Words -it's usually in there -certainly is in mine!

When all else fails, have a look at the manual...

[av8trflying]

Thanks saigon, its usually the simple things!!

[Arm out the window]

How about this?
With GPS groundspeed and track readout, you should be able to easily work out head/tailwind component (if you know your TAS) and drift angle.

Now crosswind component = drift x (TAS/60), so you can fairly simply work out the crosswind in knots too.

Given both those, drag out the dreaded whizzwheel and plot them and you can read off the wind.

Example: 180 KTAS, groundspeed 150, track 180, heading 187.

Headwind component 30 kt.
Crosswind - 180/60 x 7 = 21 knots from the right.

Putting those on the whizz wheel, I get a wind of about 215 at 36 kt.

Sound reasonable?

[XRNZAF]

Using the good old nav computer in 5 easy steps...

1. Put your TAS under the centre dot,

2. Put your true heading under the 'true index'

3. Place a mark where your drift meets your groundspeed,

4. Rotate the wheel around so that your mark lies directly BELOW the centre dot.

5. Then simply read off the wind direction (degrees true) under the true index and wind speed is the distance between the centre dot and your mark. (Oh no my pocket protector is leaking.....:8)

XRNZAF. :ok:

[flyitboy]

gee you guys, yr giving me a headache. :E



F

[Biggles_in_Oz]

from Ed Williams Aviation Formulary

TAS and windspeed from three (GPS) groundspeeds.

Determine your groundspeed on three headings that differ by 120
degrees (eg 40, 160 and 280 degrees), call these v1, v2 and v3

Let vms = (v1^2 + v2^2 + v3^2)/3
a1= v1^2/vms -1
a2= v2^2/vms -1
a3= v3^2/vms -1
mu= (a1^2 + a2^2 + a3^2)/6
Let bp and bm be the roots of the quadratic b^2 -b + mu =0 ie:
bp= 1/2 +sqrt(1/4-mu)
bm= mu/bp
The TAS and windspeed are then given by sqrt(vms*bp) and sqrt(vms*bm)
-- provided that the TAS exceeds the windspeed. If this is not the
case, the roots are exchanged.
This is a handy way to check your TAS (and the calibration of your
airspeed indicator) using your GPS groundspeed, even though the wind
is unknown.
obviously this is something that you'd preprogram into a PDA or calculator beforehand.

[flyitboy]

OMG 'Biggles', thou shall be respected from now on:D, not sure what for tho other than making all the ATPL theory seem like childs play!:{
Do pilots really use that stuff in the real world?


F

[Biggles_in_Oz]

Personally, I don't try and work out actual winds during climb, as it'll probably change with altitude and I spend much more time in cruise than in climb.

When in cruise and a long way away from any navaids or really obvious landmarks, I'll work out the actual wind ala what XRNZAF and Arm out the window would do.

[pw1340]

If you are using a garmin gps then search through the menus for "E6B flight computer". Once in that page you enter the following:
- altitude
- airspeed
- baro pressure
- oat
- heading

It will calculate and display:
- tas (you can leave ias, press, temp out and enter your own tas)
- head/tail wind component
- wind direction
- wind speed
- density alt

This is a feature on the newer portable units (96, 196, 296) but if my memory is correct it is also on the pilot 3 and even the garmin 100.

Hope this helps.

PW

[pile-it]

A rule of thumb for wind component on climb - if you only want to know how you're going with respect to headwind or tailwind: 3 X Altitude + IAS gives an approximate TAS to compare with your current GS from GPS or DME. E.g. IAS 150 passing 10,000 gives approx TAS 150 + 3 X 10 = 180. GS from GPS 195 gives a wind component of +15. Check at each level passing to see if tailwind/headwind is increasing or decreasing to find the most favourable level for cruise.

[ForkTailedDrKiller]

Here's how I do it - seems to work out OK.

1) I generally only fly at A090 or A100 - occassionally higher to get on top of summer Cu. I get better Next G reception up there so I can post on PPRuNe enroute.

2) I only work on winds at my planned cruising altitude. When you fly something that climbs to 10,000 in 10-12 minutes depending on weight (eg FTDK) then winds in the climb are virtually irrelevant.

3) Ignore the forcast winds completely - they are invariably WRONG. eg yesterday winds a A090 were forcast to give me a 15+ kt headwind, however I had a 170 kt GS (ie 10 kt tailwind) most of the way south.

4) Climb at a constant IAS (eg 110 kts in the Bo), run a TAS every couple of thousand ft, and compare it to your GS on the GPS.

5) When you get to your planned cruise alt - if you don't like what you find - descend to where you expect to get a better GS, if circumstances allow.

Dr :8

[av8trflying]

Thanks guys for all of your help.

I think pile-it's way is the one I was after.

The reason why i asked for a solution during climb is for parachuting as the jumpers want to know the winds through different levels.

Once again thanks.

[kalavo]

Ahh skydivers, why didn't you say so!

Print out and give them the forecast. They'll pick a completely random run in direction and get out over the airfield +/- 0.5nm anyway.

While climbing mention the GPS seems to agree with the forecast.

From 10,000' they can usually get back from 1.5nm (some tandems and students can only manage 1nm). From 14,000' they can usually get back from 2nm out (again students and tandems sometimes don't notice where they are and find it harder more than 1.5nm).

After landing, one of them will put on their grumpy face and say that didn't work, we should try a run in of (another completely random direction) and get out at (another completely random distance no more than 0.5nm from the drop zone so they'd make it back even downwind. If the person is a senior jumper the others will agree, and they'll be happy for the rest of the day.

This works for speeds up to about 30kts. The only thing that changes above that is how grumpy they look after the first flight :)

Note: If they pick you as being someone who really understands how the GPS works, they'll also start asking if they can move the point you drop them out at 0.25nm to the N, S, E of W of the actual drop zone. Again it makes no difference, they'll all usually get back in any wind that doesn't exceed your crosswind limits. :) Just make sure you fly as accurately as you can... if you're a bare CPL holder, some of the skydivers will have more hours in aircraft than you do (6000 jumps = at least 1500hrs flight time :) and generally know how to read a GPS and will see when you dont do what you were asked :)

[imlost]

just as a rough guide.... in parachute dropping you will know your ias for the whole climb and jump run.... work out before the flight the tas you'll expect for every couple of thousand of feet up to drop altitude. if atc/traffic allows it, do a circling climb on the first run of the day and compare gs v tas ie gs will increase when turning onto downwind and decrease when turning up wind.... this will give you a good idea of wind on climb. also if cloud is present have a look at the direction its travelling... since the jumpers will be under canopy at about the same height, this is quite useful. get yourself established onto the jump run early for the first jump! use gs v tas and drift to get an idea of winds aloft (we would use the forcast wind as a starting point for the run direction) then adjust it as you fly the jump run, either by offseting the run into wind or even a different track. late in the jump run is not a good time to be pulling out the wizz wheel... just take a rough guess!!
after the first dump.. have a chat to the jumpers and refine the run direction... it the winds are completely different than expected late on the jump run, dont hessitate in telling the jumpers to stay in the plane... and reverse the run direction.... it better than picking them out of trees and off power lines!! im sure you'll find plenty of opinions from jumpers on how to fine tune the run!! hope this helps!

[av8trflying]

Thanks guys for all of your help, it is very much appreciated.:ok:

[Arm out the window]

"How dare you ,sir! Clearly, you are located in some far outpost of the Empire!"

Do we perchance detect the wrath of a forecaster? :)

[Sexual Chocolate]

God almighty. There are some interesting methodologies in this thread.

Do an orbit while maintaining a constant IAS and monitoring your GPS. You need three pieces of information.

As you orbit, watch your groundspeed tick down until you reach a heading where it pauses, and then starts climbing again. This is the heading which gives you your lowest groundspeed. This is where the wind is coming from. Remember what the groundspeed was at this point. Keep turning and note the groundspeed when you are 180 degrees out from where the wind is coming from. This will also be your highest groundspeed. Subtract the lowest groundspeed from the highest groundspeed and divide by two. This is how strong the wind is.

Next, lean down to the loadmaster or the jumper who thinks he is spotting your aeroplane and yell: the wind is xx knots from xxx, you little prick. Then go back to flying your aeroplane and keep ignoring directions from the skydivers.:E

av8trflying - check your PMs

[youngmic]

For a real lazy way to determine HW or TW whilst on climb so as to pick the most favorable wind, try the following, It is an expansion of Pile it and others principal.

On your note pad/knee board or whatever right down a permanent note with your IAS v TAS for each 1000' level.

Eg.
IAS TAS
1000' 100 102
2000' 100 103
3000' 100 105
4000' 100 107
5000' 95 104
6000' 95 106
7000' 95 107
8000' 90 104
9000' 90 106
10000' 90 108

So now as you climb, peg your IAS accurately and you can then X check your GS against the written done TAS figure. The reducing IAS is simply an adjustment to maintain optimum climb performance. You can even jot down the GS at a particular level as you continue the climb hoping to improve the GS.

The given IAS above are just generic and the TAS is close but not dead accurate, a reference note for ISA variations is handy to.

Done once and then it's just a glance at the table there after.

Hope it helps