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JSACKS

Interpreting WIND predictions in the 744 FMC

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When you input the WIND in the RTE DATA pages of the 744's FMC, how is that data applied to the flightplan? Is it carried forward in the flight and applied to all future waypoints until/unless changed by any subsequent entry/entries? It seems that this might be the case. But as I am still experimenting and inexperienced with this aspect of the FMC, I wanted to ask here.Appreciate any clarification, thanks.Jonathan


Jonathan Sacks

Dell XPS Gen 4, Pentium IV Northwood extreme 3.8Ghz, 3Ghz RAM, eVGA 7900 GTO,

12 GoFlight modules plus MCP-PRO AP and EFIS, GF pedestal, CH rudder pedals,

CH throttle quadrant, 42" LG LED, 24" DELL LCD, Windows XP, FS2004, FSUIPC 3.96

FS Autostart 1.1 (Build 11), FS Navigator 4.6, UT, FE, GE, REX, PMDG, Level-D, PSS, etc.

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Jonathan:You can input layers individually, or once entering a layer, apply and look for the W carat all the way down, that will apply your entered wind bearing/speed to all levels below.From my mate Steve B. In the UK I have gone to entering 2 levels - 1000 feet (to ground) and cruise (FL33, 35 etc). We do get to playing with the FMC CDU and revise as we receive updated data in real time from the ND wind indicator.Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png


Best-

Carl Avari-Cooper

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The effect of entering winds can be seen in the projected fuel on board at destination value, which changes in concert with the inputs.


Dan Downs KCRP

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May I add my voice to those calling for contributors to give a proper name when signing their forum entries. It makes posting so much more personal.I tend not to use the winds aloft entries into the FMC during the en route phase of flight because I usually monitor the difference between planned and actual fuel remaining at major en route waypoints. But I feel that it is very important to enter wind data for each descent. This makes it much more likely (assuming that the reported winds are the same as those actually encountered) that I shall arrive at my airport approaches smoothly and accurately.I use wind data from Active Sky for my destination airport, and usually enter wind direction and speed to my waypoint data for each of FL300, FL240, FL120 and 1000 ft when I am within 150 nms of my Top of Descent. Entry of this data can then make sometimes significant changes to my TOD point.Regards,


Cheers, Richard

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I think my question might have been misunderstood here, or maybe I did not pose it with sufficient clarity or accuracy. Let me elaborate further as follows:I am not asking about layered winds (at least not right now!). I mean to ask about the manner in which the FMC processes wind data for a waypoint. In this regard I had thought originally that when you enter a WIND bearing/speed on the RTE DATA page, the FMC would calculate the total flight time based on reaching that specific waypoint utilizing the wind data entered. However, it seems that the FMC will apply just one single given bearing/speed for a given waypoint to all future waypoints of the flight. At least this appears to be the case in entering wind data for waypoints during the CRZ portion of the flight.For e.g., on my flight from KIAD to EGLL, I entered a wind bearing/speed for waypoint MVY (at CRZ level) which is only 370nm into the 3200nm flight. I observed that when the data was input to the RTE DATA page for that specific waypoint, the projected flight time immediately fell from 7 hours (with no wind data entered at all before) to 6 hours 35 minutes. In other words, the FMC took the wind data and seems to have applied it forward to the remaining 2800nm of the flightplan--even though I did not specify any additional wind bearing/speed data to any of the remaining waypoints.I found this to be interesting as I had projected the same average wind speed all the way over the North Atlantic to waypoint SHA (about 2800nm down range) and even beyond. So it seems that this is a useful shortcut in that you don't need to enter the same wind bearing/speed data into every single waypoint in the CRZ portion of the flight.I am inexperienced with this procedure and so I am trying to get confirmation as to whether the FMC is in fact supposed to work in this manner. Sorry if I appear stupid with this question, but I just don't know.Hope this is clear and thanks for any guidance.Jonathan


Jonathan Sacks

Dell XPS Gen 4, Pentium IV Northwood extreme 3.8Ghz, 3Ghz RAM, eVGA 7900 GTO,

12 GoFlight modules plus MCP-PRO AP and EFIS, GF pedestal, CH rudder pedals,

CH throttle quadrant, 42" LG LED, 24" DELL LCD, Windows XP, FS2004, FSUIPC 3.96

FS Autostart 1.1 (Build 11), FS Navigator 4.6, UT, FE, GE, REX, PMDG, Level-D, PSS, etc.

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Jonathan, you're correct, this is how the FMC in the sim works. If you enter wind info into one waypoint, this info will propagate into remaining enroute wp's. Of course, you can finetune every single waypoint afterwards to suit your needs if you like. What I usually do for shorter trips, is to enter average winds info from Active Sky into 'CRZ WIND' at the 'PERF INIT' page, and eventually insert greater changes for specific waypoints if needed. On longer trips, I tend enter as much info as possible from AS into RTE DATA, as winds changes can be quite significant on longer trips. It take some time, but I like to get as real as possible, that's my way to do it. Lazy real world drivers have ACARS to do the dirty work for them :)

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Jonathan,You must remember that as the PMDG AOM (page 12-57 & 12-58...the very last 2 pages) states this function is not a faithful reproduction of the RW 744 FMC, there is however a measure of functionality...If no wind entry is made on any RTE DATA page the FMC will assume that there are no forecast winds, this will affect your time & fuel estimates.In the PMDG FMC we can only enter one wind entry per waypoint & no OAT entry, in the RW 744 FMC you have the ability to enter wind data at four altitudes, and the OAT (deg C) at one altitude. In the RW 744 FMC the propagation of wind data is not restricted to the CRZ waypoints but also CLB waypoints. You will note that in the PMDG FMC the propagation of wind data is not possible on CLB or DES waypoints (those not at your CRZ altitude).You are correct in your assumption that a wind entry at a given waypoint is propagated forward through the route to the subsequent waypoints. Should you know the given wind at further waypoints along your route, perhaps at or after a Step Climb these will also propagate forward & so on.For example I am currently flying from EGLL to WSSS, so lets see how this works...With no wind entry the FMC is predicting my eta as 0711z tomorrow morning with 13.9t of fuel remaining.The current wind at my present CRZ altitude (FL330) is 286/2 (unrealistic but thats VATSIM CRZ WX for you!)...entering this wind data at the active waypoint on my route gives a new predicted eta of 0707z with 14.6t of fuel remaining...this data is also propogated forwards to each subsequent waypoint in my route & is indicated by the W> symbology.One important point to remember...if you decide, or if when flying online ATC decide to give you a DIR INTC to a waypoint/position further along your route you should select the ABEAM PTS prompt, this will ensure that your wind data & its propagation along the route is saved.So as you can see even only a light wind can have some effect on your eta & fuel remaining at destination. IMHO this is a crucial part of the a/c operation, it was disapointing to not see its faithful reproduction in the PMDG 744, in balance to my comment it is probably viewed by the majority of users as a minor issue, there is some functionality available so it should not detract from one's enjoyment of this magical beast!!!Before I get flack for my comments in the end I can live with it! There are so many other wonderful things to savour & enjoy!!!You may also be aware of the capability to enter wind data at 4 separate atitudes in the DES FORECASTS page which you can get to by selecting the FORECAST> prompt on the VNAV ECON DES page, data entry here can significantly affect the FMCs ability to keep you on the correct VNAV descent path in order to meet speed & altitude constriants further along the route.For the seriously afflicted pilots like Carl & myself the constant updating of the wind data entry is a labour of love as we strive toward the nirvana of arriving with exactly the amount of fuel our sums & scribbles on paper said we would have!! We are now within 1000kgs or so with some certain accuracy on most of our flights!!!Perhaps some of the RW 744 pilots on this forum could add their wisdom at this point.Kind RegardsSteve BellPS I'm just passing UBBB (Baku) on the western shores of the Caspian Sea...no caviar for me on this trip though!!


Steve Bell

 

"Wise men talk because they have something to say.  Fools talk because they have to say something." - Plato (latterly attributed to Saul Bellow)

 

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Dear Steve and Per:Many thanks to you each and both for your comments. This is EXACTLY the type of response I was hoping for. I am very grateful for your time and effort.Also, I do understand that functionality in this respect is limited in the PMDG model. So it's not a big issue for me in that regard; I just wanted to ensure I was understanding this aspect correctly.I also appreciate the measures you recommend for a DIR INTC procedure. Jonathan


Jonathan Sacks

Dell XPS Gen 4, Pentium IV Northwood extreme 3.8Ghz, 3Ghz RAM, eVGA 7900 GTO,

12 GoFlight modules plus MCP-PRO AP and EFIS, GF pedestal, CH rudder pedals,

CH throttle quadrant, 42" LG LED, 24" DELL LCD, Windows XP, FS2004, FSUIPC 3.96

FS Autostart 1.1 (Build 11), FS Navigator 4.6, UT, FE, GE, REX, PMDG, Level-D, PSS, etc.

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>One important point to remember...if you decide, or if when>flying online ATC decide to give you a DIR INTC to a>waypoint/position further along your route you should select>the ABEAM PTS prompt, this will ensure that your wind data &>its propagation along the route is saved.Steve could you explain that procedure a little bit more please? And that +/- 1000 Kgs off in fuel figuring for a 10 hrs flight seems pretty accurate to me, what are you using for flight planning? Bozhan http://www.flythy.com/images/avsimbanner.jpg

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Bozhan,Pages 12-35 & 12-36 (FMC FLIGHT PLAN MODIFICATION) of the PMDG 744 AOM describe 'Direct to' Flight Plan Modifications. The 'ABEAM' prompt can be seen in the 3rd picture on Page 12-35 at LSK 5R, it is not discussed there but by selecting it prior to pressing the 'EXEC' light the FMC will 'draw' an abeam waypoint on the dotted white new route of flight to the 'Direct to' waypoint, as such 'ABEAM' waypoints are subsequently annotated with '01' (e.g. LON01 etc). Should a further Flight Plan Modification be made these abeam waypoints then become annotated with '02' (e.g.LON02 etc) I suspect is to indicate that they are an abeam reference of the original waypoint position on the new route of flight.As for flight planning a few known constants & know variables, & the application of the speed/distance/time triangle to those constants is the key. There is an excellent section in the AOM on this subject, & Dan Downs himself has produced a very useful 744 fuel planner which is available from AVSIM.Other than that it's as simple as a good old fashioned pencil, eraser, calculator (if your maths like mine is poor) & some paper for your scribbles!!Kind RegardsSteve Bell


Steve Bell

 

"Wise men talk because they have something to say.  Fools talk because they have to say something." - Plato (latterly attributed to Saul Bellow)

 

The most useful tool on the AVSIM Fora ... 'Mark forum as read'

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Guest D17S

Still have fingers crossed for that (RW) enroute winds update from (Satcomm > FMC) Active Sky feature in the FSX 744. Load in a variable to the AS winds parameter and let the fun begin. Then, there'd actually be a reason for us simmers to keep that scribble-pad up to date. Ever see a RW flight plan after a flight? Wind/temp/fuel at every waypoint (Well generally. It's easy to tell the inspired-new guys from the old-handers). As it should be, there's so little else going on during a successfully boring flight.

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Sam,While we are at it here are my FSX744 wish list items:1. Fully implemented WPT WIND DATA entries, as you say with ACARS/SATCOM uplink facility to upload from FS WX, AS or SB3.2. FIX Page PRED ETA/ALT entry possible (useful for displaying that all important MSA, crew changeover times & an instant indication of pred eta at a particular pos).3. RTE OFFSET function, if activated displaying WPT data (eta) by each WYPT.4. OFFPATH DES function, those blue/white dash/dot circles are handy for energy management.Finally...Drivers for the Aerosoft Australia MCP/EFIS/EICAS compatible with FSX744...there is no other big Boeing MCP product on the market.Kind RegardsSteve Bell


Steve Bell

 

"Wise men talk because they have something to say.  Fools talk because they have to say something." - Plato (latterly attributed to Saul Bellow)

 

The most useful tool on the AVSIM Fora ... 'Mark forum as read'

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