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    Originally posted by FBW View Post
    One last time, why are you looking up Mach 1.8 at 27k feet when it is limited to 750 CAS below crossover altitude.
    What is the crossover altitude for 750kCAS & Mach 1.8 according to you?

    Crossover altitude is the point where a given airspeed coincides with a specified Mach number. So according to the chart it IS 27.5kft for 750kCAS & Mach 1.8 and I'm perfectly ok to do what I did.

    Why does http://hochwarth.com/misc/AviationCalculator.html suggest it is higher than that? Because the underlying equations are not valid for Mach numbers greater than 1, as is pointed out clearly enough on the site itself. Plug the erroneous CAS value from the CAS/Mach/TAS/EAS Conversion into the Crossover Altitude calculator and it miraculously gives the correct altitude - but that doesn't make the CAS value any less wrong.

    Originally posted by FBW View Post
    Two, you obviously didn’t cross reference with temp on naca conversion chart. The one I gave you matches perfectly +/- 5 knots with naca
    All the calculators and charts I consulted agree on the temperature value for 27.5kft which I gave. That NACA table dates from 1943, so it's hardly the Standard Atmosphere we know today, but temperature interpolated between 27kft & 28kft works out to -39.4C, speed of sound to 592kts - close enough, all things considered.

    Originally posted by FBW View Post
    Use your head, why did early airspeed record attempts always occur in morning when the air is cool and calm?
    Very early? Because once your (piston) engine has reached operating temperature (tolerances & lubricant viscosity nominal), cold air with its higher density will benefit volumetric efficiency and hence power output, not to mention better waste heat rejection in the radiators. Compressibility was not yet a significant concern. Later on? It depends TM. Low altitude jet records were actually flown in the *highest* possible temperatures (New Mexico & the Mojave Desert for Sageburner and Greenamyer's efforts) because a Mach limited aircraft will achieve the highest TAS with the highest speed of sound (which is proportional to the square root of ambient temperature, as stated earlier).

    Originally posted by FBW View Post
    To be continued, but simply put, you used a crap calculator that does not adjust for pressure/ temp unless you look up international standard day for a given altitude it’s online (should be 217 ish k) I’ve given You all the info you need, use it.
    Well, your suggested Standard Atmosphere calculator (http://hochwarth.com/misc/AviationCalculator.html) gives the same temperature as the one I used. Since I've shown why I did it the way I did pretty exhaustively, maybe you can make your case for an OAT of 217K in similar detail.

    As for crap calculators, I'd submit that I'm not the one using a source which explicitly states it's only valid for Mach <1...
    Last edited by Trident; 13th June 2018, 05:55.
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      Originally posted by FBW View Post
      Here try this, a simple google True airspeed Mach 1 30,000 feet. Then use your method of reading conversion chart without temp conversion. It’s right in front of you.
      I did, first result is another calculator which only offers a small number of altitude levels for selection. I tried 30kft & Mach 1.8 and got 1062kts TAS. Using my method of reading the chart I get 1060kts - still fail to see the problem.
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        Chinese Y-30. To be equipped with DSI intake plus engines, like on their fighters, drones, trainers, etc

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          Chinese Y-30. To be equipped with DSI intake plus engines, like on their fighters, drones, trainers, etc
          Nope ... if you look at the c/n of that bird it's just an older Y-20 static test frame.
          Attached Files
          ...

          He was my North, my South, my East and West,
          My working week and my Sunday rest,
          My noon, my midnight, my talk, my song;
          I thought that love would last forever; I was wrong.

          The stars are not wanted now; put out every one:
          Pack up the moon and dismantle the sun;
          Pour away the ocean and sweep up the woods:
          For nothing now can ever come to any good.
          -------------------------------------------------
          W.H.Auden (1945)

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            I have difficulty on which part of photograph to focus..the plane or the creature in front corner..
            Last edited by ananda; 13th June 2018, 12:52.

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              compare the size of the person next to the plane

              here is the y-20

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                The girl is clearly Photoshopped into that picture, look at the quality of the background image of the Y20 compared with the foreground pic of the girl.

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                  It's not the same plane, period.
                  There is plenty to detail that will bring anyone to the right conclusion. See cockpit windows profile, wiper size or wing root section (this one is for a slower plane, probably turboprop) for example.

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                    I don't know how anyone can believe that the very clear picture Deino provided is even connected to that transport aircraft in the picture.. which is quite blurry.

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                      I don't know how anyone can believe that the very clear picture Deino provided is even connected to that transport aircraft in the picture.. which is quite blurry.
                      Simply since there were several more images posted at several Chinese forums and one guy even was so close to post detail shots ... IMO anyway better than posting ps'ed fake images only to mislead the size of that bird.
                      ...

                      He was my North, my South, my East and West,
                      My working week and my Sunday rest,
                      My noon, my midnight, my talk, my song;
                      I thought that love would last forever; I was wrong.

                      The stars are not wanted now; put out every one:
                      Pack up the moon and dismantle the sun;
                      Pour away the ocean and sweep up the woods:
                      For nothing now can ever come to any good.
                      -------------------------------------------------
                      W.H.Auden (1945)

                      Comment


                        KJ-500A: KJ-500 with IFR probe

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                          Chinese internet is going wild over it with many thinking its a new medium airlifter.
                          this one came from a popular site called chinchin

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                            Chinese internet is going wild over it with many thinking its a new medium airlifter.
                            this one came from a popular site called chinchin
                            NO, not really the Chinese Internet, but some stupid fan-boy pages like the "popular site called chinchin". I don't know why all that hype. Even the original poster of these images confirmed by the c/n - just look at the post I made one page back - it is NOT the Y-30, it is plain and simple a test specimen of the Y-20 manufactured already in 2009 ... this "thing" was built also at XAC and not at Shaangxi, which develops the Y-30.
                            ...

                            He was my North, my South, my East and West,
                            My working week and my Sunday rest,
                            My noon, my midnight, my talk, my song;
                            I thought that love would last forever; I was wrong.

                            The stars are not wanted now; put out every one:
                            Pack up the moon and dismantle the sun;
                            Pour away the ocean and sweep up the woods:
                            For nothing now can ever come to any good.
                            -------------------------------------------------
                            W.H.Auden (1945)

                            Comment


                              J-20 air refuelling?
                              Attached Files

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                                Oh come on ! ... these are so badly photoshopped....
                                ...

                                He was my North, my South, my East and West,
                                My working week and my Sunday rest,
                                My noon, my midnight, my talk, my song;
                                I thought that love would last forever; I was wrong.

                                The stars are not wanted now; put out every one:
                                Pack up the moon and dismantle the sun;
                                Pour away the ocean and sweep up the woods:
                                For nothing now can ever come to any good.
                                -------------------------------------------------
                                W.H.Auden (1945)

                                Comment


                                  Oh okay my bad!

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                                    Indeed. The J-20 must be rather underpowered if it needs reheat to keep up with the tanker...

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                                      Oh okay my bad!
                                      No problem, and sorry, if I was a bit hash with my reply.

                                      The J-20 - and no other PLAAF-type - has the ability to be refuelled via a boom and also the J-20 has a IFR-probe similar to the J-10, but retractable.
                                      ...

                                      He was my North, my South, my East and West,
                                      My working week and my Sunday rest,
                                      My noon, my midnight, my talk, my song;
                                      I thought that love would last forever; I was wrong.

                                      The stars are not wanted now; put out every one:
                                      Pack up the moon and dismantle the sun;
                                      Pour away the ocean and sweep up the woods:
                                      For nothing now can ever come to any good.
                                      -------------------------------------------------
                                      W.H.Auden (1945)

                                      Comment


                                        And mismatched nozzles....
                                        "The early bird gets the worm but the second mouse gets the cheese."

                                        Comment


                                          What is going on here with the J-20 program ?? Why is nobody keeping track of it ?

                                          The Chinese brass say that the jet is in service. With what engines ? Surly this first batch isn't fully stealth. They don't have serrated engine nozzles.

                                          How many are being built ?

                                          Everyone is watching the su 57 at every turn and making theories about the state of the program yet the J-20 program just goes unnoticed. Everyone just nods their head when the Chinese make statements about the program.
                                          Last edited by KGB; 9th July 2018, 17:34.

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