Archived

This topic is now archived and is closed to further replies.

fro2do

Winds Aloft & Inputting them to the FMC

Recommended Posts

When I complete my flight plan with PFPX and I get the latest winds and temps for the day...when I export 

them to the fmc and I start comparing them during the flight there is a discrepancy to them all.

 

I know that the weather is dynamic and it is trying to compute but how far off is it?

Is there a fault tolerant, and how much?

 

Once I request the winds to the fmc how come I can't change it to the true values at a certain Vor or waypoint during flight?... and because of the wrong data will it interfere with the entire flight plan.

 

Thanks.

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

When I complete my flight plan with PFPX and I get the latest winds and temps for the day...when I export

 

them to the fmc and I start comparing them during the flight there is a discrepancy to them all.

 

Giancarlo

Are you using Online (PFPX), AS2012, or REX as your source of winds aloft?

 

Edit

This is part of a post I made in the PFPX forum. “:I am using AS2012 for the weather and that is selected in PFPX  options. I start AS2012 first and let it run until synthesis completed appears on the status page. I then enter the flight plan which will later be entered into PFPX  as a copy/paste over the PFPX generated plan. I print a NAV LOG and Coded Route Route Weather from  AS2012. I then complete PFPX , release the flight and print the OPF. When comparing the winds at FL340 from AS2012 to the winds from PFPX at waypoints there is a difference. Between running AS2012 and computing the flight in PFPX there is no more than ten minutes elapsed. This has happened on numerous occasions . So I believe the time deference  does not account for discrepancy.”: I assume both PFPX and AS2012 use NOAA as their source of information so you would think the forecasted winds would be the same at each waypoint. However the direction and speed may disagree by 5-10 degrees and 5-10 knots. The whole deal is a mess before you even import the winds into the FMC. But you must remember these values are only forecasts and the winds you encounter during the flight are real and could and probably will be different. What is acceptable? I would say anything as long as ii is not off by 180 degrees or 50 knots at a waypoint proceeding a long leg. I have no idea where the allegedly real weather comes from. Maybe it comes down from Mount Sinai in tablet form delivered by Moses like the Ten Commandments were. Who knows?

 

Michael Cubine

Share this post


Link to post
Share on other sites

 

 


when I export 
them to the fmc and I start comparing them during the flight there is a discrepancy to them all.

 

Have a look here:

http://forum.avsim.net/topic/418750-pmdg-777-issue-tracking-thread-read-before-posting/

 

Specifically:

 

Found / Fixed / Added for Future Update:

[...]

- Wind import .wx file is no longer locked from being written to after initial WIND REQUEST and can now be updated in flight.

- Fixed ACT WIND page ordering. (pages 1 and 2 missing etc)

Share this post


Link to post
Share on other sites

Thanks Michael Kyle for you help I love the bit with the ten commandments but Kyle I read 

that statement but I'm confused I am using Active Sky for the winds but once I export them

to the fmc I can't change it... so is it not working yet or am I doing something wrong?

 

Sorry about this guys but still a bit confused.

altb

Giancarlo.

Share this post


Link to post
Share on other sites

 

 


but Kyle I read 
that statement but I'm confused I am using Active Sky for the winds but once I export them
to the fmc I can't change it... so is it not working yet or am I doing something wrong?

 

As I quoted from the issue tracking thread:

The feature is not working as it should.

You cannot update the winds once you've requested them.

 

Both of these issues will be fixed after the next update.

Share this post


Link to post
Share on other sites

 

 


As I quoted from the issue tracking thread:
The feature is not working as it should.
You cannot update the winds once you've requested them.
 
Both of these issues will be fixed after the next update.

Ok Kyle thanks I understand now.

Share this post


Link to post
Share on other sites
how come I can't change it to the true values at a certain Vor or waypoint during flight?.

 

You wouldn't change them in flight anyway.

Share this post


Link to post
Share on other sites

 

 


You wouldn't change them in flight anyway.

 

Thanks for your reply Jordan that's what I wanted to know if the weather changes why should you

change the settings won't it affect the performance of the aircraft? fuel E.t.c.

Share this post


Link to post
Share on other sites

 

 


You wouldn't change them in flight anyway.

Jordan

 

If you had newer information from say AS2012 why wouln't you update winds at the remaining waypoints in the flight plan? I do it it in the MD-11 if there are any significant changes from what is in the FMS. On some of 10-12 hour flights I do in the MD-11 the ETA and remaining fuel at landing can go haywire real quick in the last third of the flight.

 

Michael Cubine

Share this post


Link to post
Share on other sites

Thanks for your reply Jordan that's what I wanted to know if the weather changes why should you

change the settings won't it affect the performance of the aircraft? fuel E.t.c.

 

During flight, the FMC takes winds from 2 sources; the forecast winds you entered into the FMC during preflight and the winds the aircraft is actually encountering.

 

Fuel and time predictions are based on blending these 2 sources of information together, with forecast winds being used for far off waypoints and actual winds taking priority as the waypoint gets closer.

Share this post


Link to post
Share on other sites

with forecast winds being used for far off waypoints and actual winds taking priority as the waypoint gets closer

 

 

Jordan

 

So you are saying if the flight plan has 15 waypoints left, the FMS is maybe only using the forecasted winds for last 10 and actual for the next 5 waypoints in calculating an ETA. I know it's not as black and white as 15/10/5 but this is the general idea.

 

Michael Cubine

Share this post


Link to post
Share on other sites

Jordan

 

So you are saying if the flight plan has 15 waypoints left, the FMS is maybe only using the forecasted winds for last 10 and actual for the next 5 waypoints in calculating an ETA. I know it's not as black and white as 15/10/5 but this is the general idea.

 

Michael Cubine

It might be done on distance, can't remember exactly! Using your example though, it might use actual winds for the next 5, forecast winds for the last 5, and a mix of the 2 for the middle 5. It's described in the FCOM.

Share this post


Link to post
Share on other sites

It's described in the FCOM.

Jordan

 

I see what you are talking about on page 11.42.38 of FCOMv2. When the problem with changing wind entries is corrected, I think I would still go ahead and enter any significant changes from a new forecast except for maybe the next three waypoints unless they are the start of long legs like 250-350 nm.

 

I just finished a 12.2 hour MD-11 flight and I didn't change any wind entries even though I had a newer forecast. In the first six hours of the flight the ETA was 0323Z or 0324Z. In the last six hours it went to 0345Z.

 

Michael Cubine

Share this post


Link to post
Share on other sites

I wouldn't bother trying to update the winds because I don't think this is done in reality, and PFPX gives me pretty accurate information in the first place.

Share this post


Link to post
Share on other sites

 

 


I wouldn't bother trying to update the winds because I don't think this is done in reality

 

Careful.

 

What one operator does, another operator will turn upside-down, repaint, re-word, and otherwise contradict the former practice.  Example: SWA didn't use A/T or VNAV until recently, while other operators did.  Some operators leave landing lights on until 10.  Some turn some of the lights off at gear retract, and the rest at 10.

 

Remember that your wind pull in the sim is current wind only.  Airline systems generally tend to have forecast winds mixed in to those data pulls to be more accurate for when the aircraft is planned to be there.  So, even if they didn't do it in the real world, you'd probably want to do it occasionally in the sim.

 

I highly doubt that pilots don't update the wind data occasionally, particularly on long segments.  Weather changes, and forecasts get less and less accurate as the time between now and the forecast increases.

Share this post


Link to post
Share on other sites

Weather changes, and forecasts get less and less accurate as the time between now and the forecast increases.

 

 

Kyle

Very true. Last year I had a discussion in the OpusFSX Forum with the developer about forcasted winds and I came to the conclusion that due to a unique set of circumstances the forecasted winds entered into the FMC during preflight could be as old as 18 hours. Towards the end of a 14 hour flight this could result in FMC containing wind forecasts from 28 to 32 hours old. The forecast is certainly out of date. Are the winds significantly diffferent in the newer forecast? Maybe or maybe not. But the two forecasts need to be compared.

 

Michael Cubine

Share this post


Link to post
Share on other sites

 

 


Are the winds significantly diffferent in the newer forecast?

 

Is it going to snow tomorrow, or will it be sunny and kinda nice?  How sure are you about that?  :wink:

 

Remember, aviation forecasting is forecasting the same weather you're seeing forecasted from your daily news sources.  Sure, it might be slightly different source to source, because each one has a different person forecasting, but weather is weather.

 

Air stability is the main issue.

 

Stable air?  Chances are that the forecast won't change too much.

Unstable air?  Good luck...

 

You're from Tampa.  You should know better... :wink:

Sure, you can set your watch by the summer afternoon storms, but where is that anvil going to pop up, exactly?  Unstable air means it could be anywhere.  A front on the other hand?  I can tell you caparatively precisely where that storm is going.  Similarly, what will the wind look like?  The forecast could be stable, or it could be unstable.

 

It just depends on the day.

Share this post


Link to post
Share on other sites

Careful.

 

What one operator does, another operator will turn upside-down, repaint, re-word, and otherwise contradict the former practice.  Example: SWA didn't use A/T or VNAV until recently, while other operators did.  Some operators leave landing lights on until 10.  Some turn some of the lights off at gear retract, and the rest at 10.

 

Aren't wind up dates enroute a new thing that's relatively rare? I certainly saw something not too long ago detailing new technology for updating descent winds; however that might have been the accuracy of the data rather than aircraft being able to receive the information.

 

Remember that your wind pull in the sim is current wind only.  Airline systems generally tend to have forecast winds mixed in to those data pulls to be more accurate for when the aircraft is planned to be there.  So, even if they didn't do it in the real world, you'd probably want to do it occasionally in the sim.

 

I use PFPX which from what I understands uses the ETA for each waypoint and gets the forecast winds for that time, so this is taken into account.

Share this post


Link to post
Share on other sites

 

 


Aren't wind up dates enroute a new thing that's relatively rare? I certainly saw something not too long ago detailing new technology for updating descent winds; however that might have been the accuracy of the data rather than aircraft being able to receive the information.

 

If you're watching a doc that wasn't put out by someone like Lockheed or another current contractor (so, a doc by a news firm, Discovery, and so on), I wouldn't trust its date accuracy.

 

CPDLC is newer but still not entirely "new," per se.  ACARS has been around since the late 70s, and wind/weather data has been able to be uplinked since the 90s.  There may be newer systems that I'm drawing a blank on.

 

 

 


I use PFPX which from what I understands uses the ETA for each waypoint and gets the forecast winds for that time, so this is taken into account.

 

I wasn't aware it pulled forecast wind, but I never checked.  Either way, I just said 'careful' and if you did the research to know that it pulls forecast wind, then I'd call that a careful approach.

 

Still, one airline may do one thing that another doesn't.  Further, a crew will do one thing that another will not.  I never heard the end of the complaints about one captain my friend flew with.

Share this post


Link to post
Share on other sites

If you're watching a doc that wasn't put out by someone like Lockheed or another current contractor (so, a doc by a news firm, Discovery, and so on), I wouldn't trust its date accuracy.

 

CPDLC is newer but still not entirely "new," per se.  ACARS has been around since the late 70s, and wind/weather data has been able to be uplinked since the 90s.  There may be newer systems that I'm drawing a blank on.

 

Can't remember. One for 777simmer to chime in on if he sees this maybe.

 

 

I wasn't aware it pulled forecast wind, but I never checked.  Either way, I just said 'careful' and if you did the research to know that it pulls forecast wind, then I'd call that a careful approach.

 

I'm not 100% as it was a forum enquiry and I can't remember if it was PFPX dev who answered. It seems to work though; I've flown quite a few long hauls using it and accuracy has been pretty good.

 

 

Still, one airline may do one thing that another doesn't.  Further, a crew will do one thing that another will not.  I never heard the end of the complaints about one captain my friend flew with.

 

Ah yes, the rarely spoken of aviation grey area (that shouldn't really exist). Bitten me in the past that has.

Share this post


Link to post
Share on other sites

 

 


Can't remember. One for 777simmer to chime in on if he sees this maybe.

 

Problem is, he could only speak for the operator he flies for.  And, to be honest, pilots aren't always most knowledgeable of the capabilities of the technology in the cockpit.  Not to take a shot at him, or anything, but it's a truth I had to deal with in my last job.  They know it's there, and they know how to use it to their company SOP, but a good number of them didn't know much beyond that, despite existant extra capability.

 

 

 


I'm not 100% as it was a forum enquiry and I can't remember if it was PFPX dev who answered. It seems to work though; I've flown quite a few long hauls using it and accuracy has been pretty good.

 

Cool.  Definitely post if you see anything definitive.

 

 

 


Ah yes, the rarely spoken of aviation grey area (that shouldn't really exist). Bitten me in the past that has.

 

Not to divert the topic too much, but I disagree.  Nobody knows how to perfectly fly an aircraft.  While people should stick to best practices and company SOPs, no company has a perfect SOP.  Some of the better things in life are in the grey area.  The fringe is where you get bitten for pushing boundaries.

 

CIs are grey area.  Company and personal minimums are grey area (or are, at least, not a worldwide standard).  Perhaps I'm misinterpreting what you're getting at.

Share this post


Link to post
Share on other sites

PFPX has a "Departure time". It will use forecasts relevant to the departure time (usually updated every few hours.)

So if the Forecast is right (crystal ball not included) the error should be negligible.

 

Of course this only works if you arrive at the various waypoints 'on time'. If you selected (or more likely didn't select) a Departure time, then spent hours before you did depart, your weather forecast may be hours out... and then the winds won't match.

 

Select a correct departure time in PFPX before releasing flight & saving the data, and depart at that time like a departure slot. Make sure your weather software is configured correctly to inject weather correctly into FSX, FSX default or FSinn weather off etc... 

 

However like the real world, forecasts aren't always 100% accurate. It can be very accurate, but the longer your flight, the more likely the winds at the end of your route will change (and even the forecast will change as more trending data becomes available to the Meteorological services.)

Share this post


Link to post
Share on other sites

 

 


PFPX has a "Departure time". It will use forecasts relevant to the departure time (usually updated every few hours.)

So if the Forecast is right (crystal ball not included) the error should be negligible.
 
Of course this only works if you arrive at the various waypoints 'on time'. If you selected (or more likely didn't select) a Departure time, then spent hours before you did depart, your weather forecast may be hours out... and then the winds won't match.
 
Select a correct departure time in PFPX before releasing flight & saving the data, and depart at that time like a departure slot. Make sure your weather software is configured correctly to inject weather correctly into FSX, FSX default or FSinn weather off etc... 
 
However like the real world, forecasts aren't always 100% accurate. It can be very accurate, but the longer your flight, the more likely the winds at the end of your route will change (and even the forecast will change as more trending data becomes available to the Meteorological services.)

 

Thank you Hopskip you have answered my question I did not realize the time factor,

During my flight planning I tried to depart as scheduled but then I would also change

the time I wanted, And maybe that's why I've always had the discrepancies, will test

tomorrow.

thanks to everyone for your inputs.

altb

Giancarlo 

Share this post


Link to post
Share on other sites

Thank you Hopskip you have answered my question I did not realize the time factor,

During my flight planning I tried to depart as scheduled but then I would also change

the time I wanted, And maybe that's why I've always had the discrepancies, will test

tomorrow.

thanks to everyone for your inputs.

altb

Giancarlo

Also be aware that time acceleration will result in you arriving at waypoints earlier than estimated, which will throw off the forecast wind.

Share this post


Link to post
Share on other sites

PFPX has a "Departure time". It will use forecasts relevant to the departure time (usually updated every few hours.)

 

Trent

 

If I have read the above sentence correctly the following would occur. If I set a flight up at 10:00am to depart at 2:00pm PFPX will calculate the winds based upon a forecast that is valid at 2:00pm. Is this correct?

 

Thank you

Michael Cubiner

Share this post


Link to post
Share on other sites