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krisyyz

TOD or average winds into FMC?

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Hello,

 

Sorry if this has been addressed in the past. I'm relatively new to using FS build and AS2012 with PMDG. The 737s FMC page asks for a CRZ WND entry. Is it better to use the TOD wind or the average wind component for the CRZ winds entry? I did some flights using AS2012, and the winds aloft from AS2012 were not as accurate inflight when compared to the AS flight log predictions. This affected the ETE. What method do you use to connect AS2012 wind predictions and PMDG CDU planning?

 

Thanks

 

Kristof

 

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The 737s FMC page asks for a CRZ WND entry. Is it better to use the TOD wind or the average wind component for the CRZ winds entry?

 

You've answered your own question there...

 

The FMC is asking for CRZ WND (short for 'cruise wind' of course), so would you think it would be better to use average cruise wind, or the wind at the very end of your cruise?

 

(It's asking for an average of the wind across the entire cruise portion - wind at/after T/D would be entered on the descent page of the VNAV pages)

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Do yourself a favour and turn off winds aloft in AS2012..they dont play nice together anyway..and having it on just makes the ngx spaz out.

 

Like so..

 

 

 

Havnt seen one case of this with winds aloft off.

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Do yourself a favour and turn off winds aloft in AS2012..they dont play nice together anyway..and having it on just makes the ngx spaz out.

 

I disagree.  I wouldn't tell people to not use a feature that adds realism just because yours isn't configured properly.

 

Are you using DWC?  Have you disabled turbulence effects? 

 

Here's proof that AS2012 can be used with wind aloft left on:

 

2011-12-27_17-32-54-355.jpg

 

The plane is behaving normally, making a normal right turn, accelerating normally at 10,000, with wind aloft left on.

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+1

I am using winds aloft (with DWC) in AS2012 with NGX without single problem.

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Nice pic!

 

Im in DWC, turb off..if i turn WA on strange things happen.Also winds change dramatically in direction and strenth, as the OP pionted out :

 

and the winds aloft from AS2012 were not as accurate inflight when compared to the AS flight log predictions.

 

 

I dont have FSUIPC registered so wind smoothing is not an option i can test.

 

 

..but turning off Winds Aloft cured the problems i was having.

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You've answered your own question there...

 

The FMC is asking for CRZ WND (short for 'cruise wind' of course), so would you think it would be better to use average cruise wind, or the wind at the very end of your cruise?

 

(It's asking for an average of the wind across the entire cruise portion - wind at/after T/D would be entered on the descent page of the VNAV pages)

Thanks! I meant say TOC wind, not TOD.  Entering the average winds make sense.

 

 

Do yourself a favour and turn off winds aloft in AS2012..they dont play nice together anyway..and having it on just makes the ngx spaz out.

 

Like so..

 

attachicon.gifngx on crack!!.jpg

 

Havnt seen one case of this with winds aloft off.

 

I appreciate your suggestion, but one of the reasons I got AS2012 was to inject a level of realism into FSX.  I was worried about the S-turn issue with PMDG, but I haven't experienced it yet.  As mentioned, I've played around with the winds settings so I don't get massive changes in wind direction/strength.

 

Currently, I load up AS2012, then start FSX once I'm parked at the gate in the PMDG737, I start FSBuild for route planning.  However I have to reload the flight plan within AS2012 after the route is complete so I can get the waypoint winds.  Is that the correct order of setting up a flight?

 

Greatly appreciated,

 

Kristof

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Thanks

 

Kristof

Hello! You mentioned FSBuild and AS2012. One thing you could do (if you haven't already), is to have FSBuild read wind data from AS2012 before your flight (during planning).

 

When you have everything setup, the normal flow goes like this:

 

Start AS2012 (DWC and winds aloft enabled). Wait for the AS2012 to read and process the weather data. After it has completed, plan your flight with FSBuild.

 

Because FSBuild reads weather from AS2012, your FSBuild flight plan will be extremely accurate. I've managed to do flights, where my waypoint arrival times and fuel remaining have been spot on (+/- 1min and +/- 200lbs).

 

EDIT: I forgot to mention that I personally do not start FSX until I have finished planning the flight with FSBuild.

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Hello! You mentioned FSBuild and AS2012. One thing you could do (if you haven't already), is to have FSBuild read wind data from AS2012 before your flight (during planning).

 

When you have everything setup, the normal flow goes like this:

 

Start AS2012 (DWC and winds aloft enabled). Wait for the AS2012 to read and process the weather data. After it has completed, plan your flight with FSBuild.

 

Because FSBuild reads weather from AS2012, your FSBuild flight plan will be extremely accurate. I've managed to do flights, where my waypoint arrival times and fuel remaining have been spot on (+/- 1min and +/- 200lbs).

 

EDIT: I forgot to mention that I personally do not start FSX until I have finished planning the flight with FSBuild.

 

 

Thanks for that! I wasn't sure if the AS2012 weather snapshot txt file includes global weather or simply included the weather for the flight plan loaded in AS.  So I take it you could change the route and destination in FSbuild as long as AS2012 is going and you'll still get an accurate weather picture.

 

Thanks,

Kristof

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The 737s FMC page asks for a CRZ WND entry. Is it better to use the TOD wind or the average wind component for the CRZ winds entry?

 

The FCOM merely says:

Cruise wind entry provides input to optimize FMC calculations.

Enter the forecast cruise wind.

Following on from some additional reading it seems the CRZ WIND entry is for the ToC wind for the entered CRZ ALT. Its purpose is to define the best econ speed in the climb starting with zero wind on the ground and linearly interpolating to the CRZ ALT. The LEG, RTE DATA pages are for entering forecast leg winds for predictions and smoothing against actual cruise wind. A general and unwritten rule of thumb is to enter a wind for a leg if it differs by more than 10kts or 10º of the previous entry.

 

I fly with some guys who like to enter the average wind and leave it at that. Not my preferred method, but if there is a difference it is subtle.

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Following on from some additional reading it seems the CRZ WIND entry is for the ToC wind for the entered CRZ ALT. Its purpose is to define the best econ speed in the climb starting with zero wind on the ground and linearly interpolating to the CRZ ALT.

 

While the ISA DEV is certainly related to the ISA DEV at the anticipated cruise, where did you see that the CRZ WIND entry is for T/C?  In the descent, given the higher probability of altitude constraints with a fixed airport location at which you should be at 0 AGL, wind would play a large role.  In climbing, however, wind would not play a role at all in calculating a best climb speed.  The best econ speed would be the one that uses the least amount of fuel with the best rate of climb.  While wind would influence your ground track at that best rate, it's not a factor in the calculation (see here).

 

Seems like more like it's a simple average to feed to the FMC so that it can calculate if you have enough fuel given the average wind across your route, right from the INIT page.

 

I'm curious to see if you have official references stating otherwise, however.

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I guess that this is one of those things that vary between operators. The last DVD I watched (Just Planes) was Air Canada (Embraer) flight from Canada to US and back.

 

When the pilot programming the FMS asked for the cruise winds, the pilot flying responded that "our TOC winds are xxx at xx knots". This was then the value that went into the box.

 

I would thing that this would work for shorter flights.

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I guess that this is one of those things that vary between operators. The last DVD I watched (Just Planes) was Air Canada (Embraer) flight from Canada to US and back.

 

When the pilot programming the FMS asked for the cruise winds, the pilot flying responded that "our TOC winds are xxx at xx knots". This was then the value that went into the box.

 

I would thing that this would work for shorter flights.

 

Yeah, the Embraer leads me to believe that it was a shorter flight and that the two would be similar enough not to matter (cruise average would be similar to T/C).

 

What concerns me about all of the video evidence of things is that people in simming rarely ever fact check.  How many times have we seen the 250/10 "rule" come up and people just repeat it because the last guy said it?

 

I'm not necessarily disagreeing with you, it's just nice to have a specific official reference from an FCOM or other manufacturer-specific source.

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where did you see that the CRZ WIND entry is for T/C? In the descent, given the higher probability of altitude constraints with a fixed airport location at which you should be at 0 AGL, wind would play a large role. In climbing, however, wind would not play a role at all in calculating a best climb speed. The best econ speed would be the one that uses the least amount of fuel with the best rate of climb.

You are correct with regard to best climb speed (MAX RATE or Vy), this is approximately clean speed + 50, and would contribute the lowest possible trip fuel burn (all other things being equal).

 

I am assuming that your mention of "best econ speed" is a reference to ECON speed which is the only FMC speed that uses the CRZ WIND input. ECON speed is the lowest cost determined by the operator according to their chosen cost index (CI) taking into account airframe time, fuel and possibly even schedule. Therefore "best econ" becomes a tautology and ECON speed (for all relevant phases of flight) is slower with a tailwind and faster in a headwind to best balance those vs over time compromises expressed through the CI.

 

I got the extra information from the Bulfer FMC Users Guide. Also the FCTM has this to say on ECON speeds:

 

 

For ECON climb, the speed is a function of gross weight (predicted weight at top of climb),
predicted top of climb wind, predicted top of climb temperature deviation from
ISA, and cost index.

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Also the FCTM has this to say on ECON speeds:

 

Awesome - thanks!

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The FCOM merely says: Following on from some additional reading it seems the CRZ WIND entry is for the ToC wind for the entered CRZ ALT. Its purpose is to define the best econ speed in the climb starting with zero wind on the ground and linearly interpolating to the CRZ ALT. The LEG, RTE DATA pages are for entering forecast leg winds for predictions and smoothing against actual cruise wind. A general and unwritten rule of thumb is to enter a wind for a leg if it differs by more than 10kts or 10º of the previous entry.

 

I fly with some guys who like to enter the average wind and leave it at that. Not my preferred method, but if there is a difference it is subtle.

 

Yeah, the Embraer leads me to believe that it was a shorter flight and that the two would be similar enough not to matter (cruise average would be similar to T/C).

 

What concerns me about all of the video evidence of things is that people in simming rarely ever fact check.  How many times have we seen the 250/10 "rule" come up and people just repeat it because the last guy said it?

 

I'm not necessarily disagreeing with you, it's just nice to have a specific official reference from an FCOM or other manufacturer-specific source.

 

 

So if you are doing a short flight, let's say less than 500nm, entering the TOC wind as the CRZ wind on the PERF INIT page is sufficient.  However, if you are doing a longer sector, entering the average wind component would be the best approach? 

 

I recently flew KDEN-CYYZ in a B738,  I had to change altitudes several times due to CBs and winds variations. I updated the winds on the LEGs page to match the new winds aloft (based on AS2012 flight log) and my ETE was still off by about 20minutes.  Is that the correct procedure?

 

Thanks,

 

Kristof

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Is that the correct procedure?

 

According to Vagabondo (and his reference to the FCOM), the correct procedure is to enter the T/C wind in that position.  I, personally, always entered the average, assuming the FMC was using it for its cruise calculations.

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So if you are doing a short flight, let's say less than 500nm, entering the TOC wind as the CRZ wind on the PERF INIT page is sufficient. However, if you are doing a longer sector, entering the average wind component would be the best approach?

I would say that regardless of the trip length the ToC wind should be entered as the CRZ WIND in PERF INIT and the LEGS, RTE DATA pages updated with the forcast winds where the differ significantly from the ToC. Then the FMC can calculate the most efficient speeds for each leg with the most accurate ETA and arrival fuel.

 

If you were to enter an average wind in PERF INIT and leave it at that, I reckon the FMC would calculate speeds based on that wind, any significant difference in enroute wind from the forecast could affect all the predictions.

 

That's my opinion, but any overall loss or gain over a number of flights is probably immeasurable and would thus remain conjecture :(

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Hi,

 

This is what we use on the Airbus A320.

 

  • at the first waypoint in cruise, insert wind DIR/VEL, and temperature at the initial CRZ FL.
  • at next waypoint where wind differs by 30° or 30 kts and temperature by 5°.

This can be entered on the ground or in cruise (to keep you busy). Also before the flight check the DTG with the CFP.

 

Have a nice flight

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I would say that regardless of the trip length the ToC wind should be entered as the CRZ WIND in PERF INIT and the LEGS, RTE DATA pages updated with the forcast winds where the differ significantly from the ToC. Then the FMC can calculate the most efficient speeds for each leg with the most accurate ETA and arrival fuel.

 

If you were to enter an average wind in PERF INIT and leave it at that, I reckon the FMC would calculate speeds based on that wind, any significant difference in enroute wind from the forecast could affect all the predictions.

 

That's my opinion, but any overall loss or gain over a number of flights is probably immeasurable and would thus remain conjecture :(

 

 

I actually watched some JustPlanes videos last night, the pilots did enter the ToC wind in the PERF INIT page.

 

Thanks for all the input everybody!

 

Kristof

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Because as we all know, there's no wind at FL350.

 

oh wait, Jetstreams happen at FL350 and can exceed 100kts wind speed.

 

S turns can be managed by turning off (clear air) turbulence effects. Clouds still make turbulence if you want to. Up/Down drafts can still work fine. Gusts are ok.

 

Wind Smoothing is good so you don't get 50+ knot changes in wind velocity in 1 second as you cross the 'border' between one weather reporting area and another.

 

Good weather = Weather program like ActiveSky with Winds aloft enabled and FSUICP smoothing the wind-shifts. FSX Turbulence effects disabled. (cloud turbulence effects dialled down a bit from maximum but still present).

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Good weather = Weather program like ActiveSky with Winds aloft enabled and FSUICP smoothing the wind-shifts. FSX Turbulence effects disabled. (cloud turbulence effects dialled down a bit from maximum but still present).

 

Trent

 

Look at the first post of this thread http://forum.avsim.net/topic/387061-activesky-2012-settings-what-i-am-using-now-with-ngx/. This works for me for the NGX, 744, and MD-11.

 

Michael Cubine

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