Ozrunways Winds

[Ozfergie]

I know one of you will be able to answer this - when using Ozrunwys to produce a flight plan which will be most accurate to import - GRIB Winds or Area Forecast winds?

 

My guess is the GRIB winds will be more location specific ???

 

 

[KRviator]

Personally, for long legs, I would use the grid point winds, they are more likely to better compensate for wind variations throughout the flight rather than assuming a 'one size fits all' that you get using Area winds exclusively. But in saying that, if you're not going out of the area forecast, they shouldn't be significantly different?

 

 

[ben87r]

Am I right in assuming GRIB winds are the grid point forecast?

 

I wasn't even aware until now that they were available for lower level. Just checked my area and at 10k as an example there is a fair bit of variation not reflected on the area forecast.

 

I've recently had a few longer sectors (only times I really pay attention to the winds) where they were substantially different.

 

 

[VFR Pilot]

I always found the winds aloft was very accurate but the don't have them any more, are the GRIB winds the same as the winds aloft?

 

 

[Captaincoop]

GRIB is best but can make sure it's not too old a forecast

 

 

 

[MartincaF1]

I attended a product training session by OzRunways last year (a whole year ago... in 2016) where OzRunways's Bas said he uses/prefers Area Forecast for winds.

 

 

[Ozfergie]

I attended a product training session by OzRunways last year (a whole year ago... in 2016) where OzRunways's Bas said he uses/prefers Area Forecast for winds.

That's really interesting - did he say why, can you recall?

 

 

[MartincaF1]

That's really interesting - did he say why, can you recall?

He just said it's his preference. Given I was only a few flying lessons in, I suspect he explained more but unfortunately I can't recall more info.

If you email OZR they're usually responsive - ask them the Q.

 

 

[Jaba-who]

Don't trust any of them. Pick any of them for your planning but don't rely on it.

 

The GRIB winds are still guesstimates. They calculate the expected winds between one side of the big area and the other. But instead of giving one for the whole area they break it up into 5 or 2.5 degree squares. Then they calculate the estimated wind at the centre of the small square and give you that. All sounds fine but it still is entirely dependant on if they have it correct in the first place.

 

I have been using a Dynon D180 for about 10 years which gives true wind aloft as you fly it. Comparing the actual to the forecasts gives some surprising results which show you should not get too worried about any of the forecasts winds. Ok if they re forecasting cyclonic winds etc then yep take note but as far as trying to compare say 10 knots vs 15 or 20 knots - don't get too stressed over small amounts.

 

Have done multiple long trips around Oz ( 10 days at a time with anything up to 6 or more hours in a day ) every year for over 15 years plus lots of standard local flying. Have done some where not a single forecasted wind for the entire trip was correct.

 

The good thing about using iPads/ozrunways or avplan ( and having multiple devices in the average aircraft) is that the planning exercise is really just an exercise now. You will find you will be modifying the plan according to the real world so often that the planning will mostly be redundant.

 

 

[Ozfergie]

Don't trust any of them. Pick any of them for your planning but don't rely on it.The GRIB winds are still guesstimates. They calculate the expected winds between one side of the big area and the other. But instead of giving one for the whole area they break it up into 5 or 2.5 degree squares. Then they calculate the estimated wind at the centre of the small square and give you that. All sounds fine but it still is entirely dependant on if they have it correct in the first place.

 

I have been using a Dynon D180 for about 10 years which gives true wind aloft as you fly it. Comparing the actual to the forecasts gives some surprising results which show you should not get too worried about any of the forecasts winds. Ok if they re forecasting cyclonic winds etc then yep take note but as far as trying to compare say 10 knots vs 15 or 20 knots - don't get too stressed over small amounts.

 

Have done multiple long trips around Oz ( 10 days at a time with anything up to 6 or more hours in a day ) every year for over 15 years plus lots of standard local flying. Have done some where not a single forecasted wind for the entire trip was correct.

 

The good thing about using iPads/ozrunways or avplan ( and having multiple devices in the average aircraft) is that the planning exercise is really just an exercise now. You will find you will be modifying the plan according to the real world so often that the planning will mostly be redundant.

Also really interesting - are you techy enough to know how the Dynon gives you this info?

 

 

[ben87r]

Also really interesting - are you techy enough to know how the Dynon gives you this info?

Calculates your TAS then uses ground speed and drift to work out the vector.

 

 

[Ozfergie]

Also really interesting - are you techy enough to know how the Dynon gives you this info?

OK - so just like all the other GPS devices - it doesn't actually give you a record of the actual winds aloft to compare to either the area winds or another figure that you may have used for planning.

 

 

[Jaba-who]

OK - so just like all the other GPS devices - it doesn't actually give you a record of the actual winds aloft to compare to either the area winds or another figure that you may have used for planning.

Sorry I don't understand this statement.

 

As stated by ben87r - What the Dynon does it uses the GPS it is slaved to to calculate your changing position, your TAS and your heading. From this it calculates your drift and coupled to these is able to calculate the angle of force being exerted on your aircraft to make it undergo the changes in direction. That is, it calculates the wind aloft, actual, as it happens at the time. It then gives you the calculated wind at your level only, at that time in degrees and knots ( along with a little line diagram. It does not use any forecasted winds or data bases. It doesn't generate any table for comparison. It's a real time event.

 

It certainly tells you the degrees and velocity of the wind on the screen Which easily allows you to compare it to the forecasted winds. I guess it gives you a record if you want to write them down as they happen I suppose ( as far as I can tell it doesn't record the winds aloft so you can download them later - allows saving and downloading a lot of parameters but I don't think it does that.

 

 

[Captaincoop]

Windytv, wind forecast

[Ozfergie]

Sorry I don't understand this statement.As stated by ben87r - What the Dynon does it uses the GPS it is slaved to to calculate your changing position, you TAS and your heading. From this it calculates your drift and coupled to these is able to calculate the angle of force being exerted on your aircraft to make it undergo the changes in direction. That is it calculates the wind aloft, actual, as it happens at the time. It does not use any forecasted winds or data bases. It doesn't generate any table for comparison. It's a real time event.

 

It gives you a record if you want to write down the events as they happen I suppose ( as far as I can tell it doesn't record the winds aloft so you can download them later - allows saving and downloading a lot of parameters but I don't think it does that.

 

Sorry I don't understand this statement.As stated by ben87r - What the Dynon does it uses the GPS it is slaved to to calculate your changing position, you TAS and your heading. From this it calculates your drift and coupled to these is able to calculate the angle of force being exerted on your aircraft to make it undergo the changes in direction. That is it calculates the wind aloft, actual, as it happens at the time. It does not use any forecasted winds or data bases. It doesn't generate any table for comparison. It's a real time event.

 

It certainly tells you the degrees and velocity of the wind on the screen. I guess it gives you a record if you want to write them down as they happen I suppose ( as far as I can tell it doesn't record the winds aloft so you can download them later - allows saving and downloading a lot of parameters but I don't think it does that.

I guess my point was that there are several variables in the constant calcs done by Dynon/Ozrunways etc., changes either of the variables will cause the unit to recalculate - so without a record to compare, the wind assumptions that you have used could be more accurate than you think but the TAS and heading (not held) could be the bigger variant.

 

 

[Jaba-who]

I guess my point was that there are several variables in the constant calcs done by Dynon/Ozrunways etc., changes either of the variables will cause the unit to recalculate - so without a record to compare, the wind assumptions that you have used could be more accurate than you think but the TAS and heading (not held) could be the bigger variant.

I think you are saying that forecast winds could be more accurate than the Dynon. Sorry but that is not reflected in actual outcomes or measurements over hundreds of hours and thousands of miles of flying. Experience vividly shows exactly the opposite.

 

I have flown many many trips where the GPS is able to calculate to within seconds the correct actual arrival time at destinations and maintain the correct heading and track throughout the whole leg by taking into account the winds it calculates. so one has to assume that by its very outcome it was correct and displayed little or no variance (inaccuracy).

 

The Dynon has sensors for all of the parameters needed to calculate the wind aloft. Static Air pressure, temperature probe, indicated air speed, compass and GPS location ( track) at fractions of a second intervals and a clock. While there are intrinsic variation in the accuracy of the sensors you have to keep it in perspective. These are minute, comparatively.

 

The variability of the outcome of a formula is more accurate when more of of the parameters are actual measurements and less accurate when it relies on more derived parameters.

 

Most of the parameters needed are measured not derived. Apart from the minimal variability of the relationship between altitude and air pressure so there is likely to be no or negligible variance ( accuracy ) in the TAS.

 

I don't understand what you mean by "heading not held". My understanding is that until you hold it it is not a heading. A heading is not a derived direction it is a measured direction by the compass ( magnetometer in the case of the Dynon) so except for the minimal intrinsic inaccuracy of the magnetometer it is otherwise a fixed measurement.

 

The track is derived from the GPS positioning which is these days mostly within an inaccuracy of about 10 metres or so.

 

So overall within the minimal amounts of inaccuracy of the sensors the winds aloft is going to be accurate and has been shown to be accurate in use.

 

On the other hand.

 

Forecasted winds are hugely broad estimates derived from measurements hundreds or thousands of kilometres apart and calculated according to guesses of temperatures and pressures which generate the air pressure differentials. They have been shown over and over again to be inaccurate, in actual use.

 

So much so that there are a myriad of well described techniques for working out errors in flight, for mitigating errors in flight and for salvaging poor positional outcomes once the hoped for destination has not hoved into sight at the expected time.

 

 

[VFR Pilot]

Excellent Jaba, I have a D180 also and agree 100%

 

 

[Soleair]

+1 on windyty

 

 

[Captaincoop]

I think we re forgetting that the the original post was for flight "planning", of course once we are in the air we have to make an adjustment for the actual winds aloft. Before we had these wonderful gadgets we still he to flight plan based on the best available info and then once in the air, check track, ground speed HDG etc to work out the actual winds for the flight.

 

The question is which do we PLAN with GRIB or area for planning purposes. It's up to you and I suppose it depends on how far you are flying. GRIB is an interpolation of winds so I use them. When I fly for work we use GRIB and they are surprisingly accurate. Time and fuel burn are very close to plan but that doesn't mean we don't check actual along the way, particularly if a level change is needed for turbulence or to get better winds. If that is required then the new level GRIB winds are used. I don't have sofisicated Dynon when I fly (no panel space) but even the flight management computer in the Boeing uses the actual winds at its present position then blends them with the forecast winds (pilot entered) to 100nm ahead and then only to entered forecast winds after that, to arrive at an estimated time and fuel overhead destination. Also area forecast winds are just that-forecast. GRIB winds are based on forecasts, interpolation, weather balloons and pilot reports, so for PLANNING proposes I prefer them. If you don't plan with something how do you plan? Unless it's a short flight using the actual winds at your precise location and applying that for the rest of your flight could prove to be a bad prospect.

 

 

[Captaincoop]

I think you are saying that forecast winds could be more accurate than the Dynon. Sorry but that is not reflected in actual outcomes or measurements over hundreds of hours and thousands of miles of flying. Experience vividly shows exactly the opposite.I have flown many many trips where the GPS is able to calculate to within seconds the correct actual arrival time at destinations and maintain the correct heading and track throughout the whole leg by taking into account the winds it calculates. so one has to assume that by its very outcome it was correct and displayed little or no variance (inaccuracy).

 

The Dynon has sensors for all of the parameters needed to calculate the wind aloft. Static Air pressure, temperature probe, indicated air speed, compass and GPS location ( track) at fractions of a second intervals and a clock. While there are intrinsic variation in the accuracy of the sensors you have to keep it in perspective. These are minute, comparatively.

 

The variability of the outcome of a formula is more accurate when more of of the parameters are actual measurements and less accurate when it relies on more derived parameters.

 

Most of the parameters needed are measured not derived. Apart from the minimal variability of the relationship between altitude and air pressure so there is likely to be no or negligible variance ( accuracy ) in the TAS.

 

I don't understand what you mean by "heading not held". My understanding is that until you hold it it is not a heading. A heading is not a derived direction it is a measured direction by the compass ( magnetometer in the case of the Dynon) so except for the minimal intrinsic inaccuracy of the magnetometer it is otherwise a fixed measurement.

 

The track is derived from the GPS positioning which is these days mostly within an inaccuracy of about 10 metres or so.

 

So overall within the minimal amounts of inaccuracy of the sensors the winds aloft is going to be accurate and has been shown to be accurate in use.

 

On the other hand.

 

Forecasted winds are hugely broad estimates derived from measurements hundreds or thousands of kilometres apart and calculated according to guesses of temperatures and pressures which generate the air pressure differentials. They have been shown over and over again to be inaccurate, in actual use.

 

So much so that there are a myriad of well described techniques for working out errors in flight, for mitigating errors in flight and for salvaging poor positional outcomes once the hoped for destination has not hoved into sight at the expected time.

When you say the GPS is spot on within seconds, is that from top of climb or enroute, because it constantly updates itself? I'm sure it is accurate at top of climb for a short flight of a couple of hundred miles (in Australia) What winds do you use for planning purposes?

 

 

[kaz3g]

My OR isn't entering the Area winds but happily enters the GRIB.

 

Any ideas, please?

 

Kaz

 

 

[dsam]

My OR isn't entering the Area winds but happily enters the GRIB.Any ideas, please?

 

Kaz

Just tested mine and Area or GIRB enter in the plan sheet fine, depending on which I choose. Any chance the MET data needs to re-download on the plan sheet? Perhaps zero winds, dismiss the app from memory, reboot the iPad and see if that sorts it out??

 

 

[Captaincoop]

Where is your flight plan from/to and at what level. I'll try it with my OR

 

 

[dsam]

My OR isn't entering the Area winds but happily enters the GRIB.Any ideas, please?

 

Kaz

BTW Kaz, I'm in Shep at present with friends. One of them tells me that a new airport site has been proposed just off the Old Dookie road near Pine Lodge. Any tips when that might eventuate?

 

Dave

 

 

[coljones]

Here is a link.

 

ACCESS NWP Data Information

 

A decode of this and other GRIB stuff would be nice for us mortals.

 

Cheers