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Tail Wind Head wind

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    Tail Wind Head wind

    Hello PMDG Folks
    Just curious. Yesterday, there were all these news about super tail winds going into England crossing the Atlantic East Bound.
    BAW approached sub supersonic speeds of 700s mph

    I know we enter winds in the FMC.

    Are tail winds and headwinds simulated in the sense that you can actually see the difference in time going east and west crossing the pond.
    Can you simulate a 200 knt plus tail wind effect on T7 or 747 forexample.

    Thanks

    Bill Hagag

    #2
    Originally posted by nhagag View Post
    Hello PMDG Folks
    Just curious. Yesterday, there were all these news about super tail winds going into England crossing the Atlantic East Bound.
    BAW approached sub supersonic speeds of 700s mph

    I know we enter winds in the FMC.

    Are tail winds and headwinds simulated in the sense that you can actually see the difference in time going east and west crossing the pond.
    Can you simulate a 200 knt plus tail wind effect on T7 or 747 forexample.

    Thanks

    Bill Hagag

    The aircraft don't "provide" the winds in the simulator per-say, but If you use weather programs like Active Sky, you will see these differences. The PMDG aircraft only allow you to import the winds from a weather program. For example, the other day I had a 150knt tailwind over South Korea & Japan. My flight 25 min shorter than usual. On the return, it was a lot longer with a significant headwind.

    Also, flight planners like SimBrief do a good job of calculating upper winds for your flight plan. Once flight plan and winds are uploaded into the aircraft, my flight times are very accurate. (based off what the initial flight plan was giving me). Within +\- a few minutes. Fuel is accurate as well. I think PMDG have done a great job with these two aspects.

    Cheers.
    Last edited by Tino; 11Feb2020, 18:42.
    Sante Sottile - CYVR

    Comment


      #3
      Yes this is possible. I allready crossed a couple of times the atlantic and it was always faster east bound then west bound due to the wind. I use active sky for the wheather and by loading the wind uplinks in the FMC I get pretty good ETA forecasts. Without the wind uplink it even sometime says insufficient fuel (in case of tailwind) because simbrief is calculating less fuel because of tailwind, so it's necessairy to have the correct wind uplinks in the FMC.
      Last edited by Hendrik96; 11Feb2020, 18:46.

      Comment


        #4
        The effects of the wind on your ETA's is simulated, however the effect of winds on the speed commanded by the FMC is not.
        In real life, with a certain cost index, the aircraft will adjust its speed based on the wind input.
        With 100kt headwind it will fly significantly faster than with 100kt tailwind.

        At lower altitudes the difference is more visible in the 737 than at high altitudes. Cruising at FL230 for example with CI6 you'd usually get around M.53 aka 250kt cruise speed.
        With a 100kt headwind that'll go up to over 280kt. With a 100kt tailwind you'd probably start to feel the buffetting

        Every airline should show this effect on the cruise IAS/Mach Number, however currently I'm only aware of the NGXu and the Aerosoft A330 having it.
        Other PMDG products, FSL, Leonardo, etc. all do not have it.

        Comment


          #5
          Thank you Emi for these answers.
          Something else came to mind after I posted my question.
          Do airlines worry about the effect of theses speeds on the airframe of the aircraft. They are not built to be supersonic or sub-supersonic

          Bill Hagag

          Comment


            #6
            I think this isn’t an issue since those enormous speeds due to tailwind only affect the groundspeed. The airspeed (speed through the actual air) isn‘t faster than without the tailwind. You can calculate the groundspeed with the addition of the tailwind component to the airspeed.

            Comment


              #7
              Originally posted by nhagag View Post
              Thank you Emi for these answers.
              Something else came to mind after I posted my question.
              Do airlines worry about the effect of theses speeds on the airframe of the aircraft. They are not built to be supersonic or sub-supersonic

              Bill Hagag
              Yes Bill, they do, but probably not in the way you are thinking because aircraft like the B737 and B744 don't fly supersonic through the air with a huge tailwind. It is only the aircraft's Ground Speed that changes with a head or tailwind; not its True Airspeed.

              As far as the FMS Cost Index is concerned, each airline will usually determine the most ECON-omical speed to fly at on a particular route and this will determine the CI for that aircraft's flight. The FMS uses the CI to set its performance parameters and the actual figure used can also be commercially sensitive, because it takes into account the operating cost of the aircraft (I.e. maintenance, crew etc) versus the cost of the fuel. Generally speaking, the higher the cost of fuel the lower the CI will be. For example, a Flight Plan with a CI of zero will result in the minimum trip fuel for maximum range airspeed and, as the CI increases the economy speed will increase.
              Michael Codd

              Comment


                #8
                I also saw that report of the 747 NYC to London in record time, but no one ever said what the wind actually was. Is 200 kts tail wind ever been seen??
                Paul Gugliotta

                Comment


                  #9
                  Originally posted by Paulyg123 View Post
                  I also saw that report of the 747 NYC to London in record time, but no one ever said what the wind actually was. Is 200 kts tail wind ever been seen??
                  Sure. A great place to find them is East of Japan over the N Pacific in the winter. Jet streams were 'discovered' by Americans during WWII when Japanese balloons made it to Oregon. AAF BGen Curtis LeMay caused a lot of consternation by the B-29 crews when he ordered low level bombing because the winds blew the bombs off target from altitude. I've heard that there is a similar strong jet in the Southern hemisphere over Australia as well and I've seen some of that on my runs to and from YSSY.

                  Keep in mind that the strong winds the other day were primarily driven by a bombastic cyclone low, which used to be rare but we're starting to seem them every year.
                  Dan Downs KCRP
                  i7-10700K 32GB 3600MHz 1080Ti

                  Comment


                  • Michael Codd
                    Michael Codd commented
                    Editing a comment
                    Southern jet streams are quite common over the Great Australian Bite. The gale and heavy rain that hit the UK last weekend had a windspeed recorded over the Isle of Wight of 97mph and another one is forecast to hit the UK next weeknd. These depressions are formed along with the jet stream and carried across the North Atlantic by all the hot air coming out of North America these days. Apparently it's called Global Warming!

                  #10
                  Originally posted by Hendrik96 View Post
                  I think this isn’t an issue since those enormous speeds due to tailwind only affect the groundspeed. The airspeed (speed through the actual air) isn‘t faster than without the tailwind. You can calculate the groundspeed with the addition of the tailwind component to the airspeed.
                  Not exactly.
                  Here is my diagram to show Wind effect on Max Range speed (Vmrc). With no wind, you should fly at point D(Vmrc). With wind, the AS not change thus the curve not move, but the GS change thus the distance cover is based on moved origin, thus the green and the red line needed to be use, with tail wind, you AS can be reduced, with Head wind, incrase, as the green and red dot shown here.
                  TIM20200212093955.png
                  ECON speed is some what more complex but same principle here.
                  ZHU Hai
                  B737 Ground instructor

                  Comment


                    #11
                    Originally posted by Paulyg123 View Post
                    I also saw that report of the 747 NYC to London in record time, but no one ever said what the wind actually was. Is 200 kts tail wind ever been seen??
                    well over 200

                    https://groundspeedrecords.com/
                    Mike Teague - p3dv4.5 - B736 B737 B738 B739 B77L B77W B744 B748

                    Comment


                    • MeatServo
                      MeatServo commented
                      Editing a comment
                      I see my Cheyenne II record is still holding 9 years later.
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