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SAAB Gripen and Gripen NG thread #4

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  • swerve
    Rank 5 Registered User
    • Jun 2005
    • 13610

    Originally posted by obligatory View Post
    no, you can add 7.2 tonnes on external load and take off with less than full fuel tank,
    ... capable of topping up in air if needed
    And been done. Take off with everything possible hanging off the wings & refuel from a tanker that's already waiting. Maximum flying weight should be more than maximum take off weight.
    Juris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere.
    Justinian

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    • TomcatViP
      Rank 5 Registered User
      • Nov 2011
      • 6110

      Originally posted by obligatory View Post
      drag has a lot to do with being sleek, the reason f-100 came out on top was a whopping 38% increase in thrust
      Again, no.

      F84 was the sleekest fighter of its time and couldn't catch an F86 or a Mig15.

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      • obligatory
        Senior Member
        • Oct 2008
        • 7043

        @swerve: yes, as speed increases so does lift

        @tomcatVP:
        https://en.wikipedia.org/wiki/Sears%E2%80%93Haack_body
        http://history.nasa.gov/SP-367/chapt5.htm
        http://history.nasa.gov/SP-367/chapt6.htm

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        • TomcatViP
          Rank 5 Registered User
          • Nov 2011
          • 6110

          You are confusing aerodynamics and the artistic work of a designer.
          You Haack body has no wing for example. With the Stilleto mentioned above and the F84, we have a similar confusion, that a slender body will perform better.
          As an example, already mentioned to you times ago, what drive the transonic drag is the body volume section and its evolution according to a sin law*. This includes the section of the fuselage, wings, tail surfaces etc... This why the F102 with its bulges on the rear performed better aerodynamically than without (and "sleeker" it was before the remodeling work). Same goes for the Buccaneer.

          It is important to seat on a rational base when it comes to complex system as are aircraft. They often constitute a sum of basic problem that it is good to have some sens with before discussing it in overall. You should take the time to clear your mind of such false opinions.

          *In wiki (you link), at the bottom, this is exactly what is written - I wonder if you have ever read it:

          A superficially related concept is the Whitcomb area rule, which states that wave drag due to volume in transonic flow depends primarily on the distribution of total cross-sectional area, and for low wave drag this distribution must be smooth. A common misconception is that the Sears–Haack body has the ideal area distribution according to the area rule, but this is not correct. The Prandtl-Glauert equation which is the starting point in the Sears–Haack body shape derivation is not valid in transonic flow, which is where the Area rule applies.
          Last edited by TomcatViP; 22nd February 2017, 02:05.

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          • hopsalot
            Senior Member
            • Aug 2012
            • 3166

            Originally posted by haavarla View Post
            I haven't followed the Gripen E much.
            Is the wing on C and E identical?
            Per this chart pretty much, 30m^2 vs 31m^2:

            http://aviationweek.com/site-files/a..._2014_jas7.pdf

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            • rcolistete
              Rank 5 Registered User
              • Jun 2013
              • 156

              Originally posted by obligatory View Post
              apparently payload is ~7.2 tonnes, which is over 2 tonnes, or over 40% more than your 'findings'
              https://twitter.com/GripenNews/statu...921665/photo/1
              With the oficial MTOW (16.5 tonnes), the maximum external load with maximum internal fuel would be about 5.1 tonnes (16.5 - 8.0 - 3.4). 7.2 tonnes external payload was cited years ago by Saab (and Brazilian Air Force), but without maximum internal fuel. This also happens for some air fighters (some Flankers, many naval air fighters, etc).

              With the new (is it oficial ?) MTOW (17.0 tonnes), then the maximum external load with maximum internal fuel would be : (17.0 - 8.0 - 3.4 = 5.6) tonnes. Simple arithmetic, it is not any "finding".

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              • obligatory
                Senior Member
                • Oct 2008
                • 7043

                err, no, max take off weight is not equal to max load,
                a fighter takes off at 200 km/h or so, but cruise much faster and will have more lift at higher speed,
                so it can top off from a tanker once airborne IF range is an issue,
                but in a gripen E, cases when range is an issue shall be rare and far in between.
                in a typical mission, few are the times when a fighter is loaded to max take off weight even.
                Last edited by obligatory; 22nd February 2017, 18:19.

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                • swerve
                  Rank 5 Registered User
                  • Jun 2005
                  • 13610

                  Originally posted by rcolistete View Post
                  With the oficial MTOW (16.5 tonnes), the maximum external load with maximum internal fuel would be about 5.1 tonnes (16.5 - 8.0 - 3.4). 7.2 tonnes external payload was cited years ago by Saab (and Brazilian Air Force), but without maximum internal fuel. This also happens for some air fighters (some Flankers, many naval air fighters, etc).

                  With the new (is it oficial ?) MTOW (17.0 tonnes), then the maximum external load with maximum internal fuel would be : (17.0 - 8.0 - 3.4 = 5.6) tonnes. Simple arithmetic, it is not any "finding".
                  This has already been covered. Maximum T/O weight should be less than maximum possible flying weight. You can take off at maximum T/O weight with space for more fuel, then top up once airborne to a greater weight, though that's likely to be something very rare. I think the Israelis may have done it a couple of times for very long range raids.

                  BTW, I recall some US aircraft being listed in various publications as having maximum external loads which require less than full internal fuel. The quoted loads are usually the sum of the maximum loads of all the hardpoints.
                  Last edited by swerve; 22nd February 2017, 21:10.
                  Juris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere.
                  Justinian

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                  • VishnuSom
                    Rank 5 Registered User
                    • Jan 2000
                    • 212

                    A bunch of Gripen pics - Enjoy folks

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                    • VishnuSom
                      Rank 5 Registered User
                      • Jan 2000
                      • 212

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                      • VishnuSom
                        Rank 5 Registered User
                        • Jan 2000
                        • 212

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                        • VishnuSom
                          Rank 5 Registered User
                          • Jan 2000
                          • 212

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                          • VishnuSom
                            Rank 5 Registered User
                            • Jan 2000
                            • 212

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                            • VishnuSom
                              Rank 5 Registered User
                              • Jan 2000
                              • 212



                              Former IAF Air Chief Marshal Arup Raha

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                              • VishnuSom
                                Rank 5 Registered User
                                • Jan 2000
                                • 212

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                                • VishnuSom
                                  Rank 5 Registered User
                                  • Jan 2000
                                  • 212

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                                  • VishnuSom
                                    Rank 5 Registered User
                                    • Jan 2000
                                    • 212

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                                    • Loke
                                      Rank 5 Registered User
                                      • Jun 2008
                                      • 3302

                                      Hi Vishnu,

                                      thank you for sharing those great photos, it is much appreciated!

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                                      • Loke
                                        Rank 5 Registered User
                                        • Jun 2008
                                        • 3302

                                        Last week, Czech and German fighters executed a joint training in the airspace of the Federal Republic of Germany. Two Czech Gripen fighters carried out aerial fights with two German Eurofighter Typhoon aircraft.

                                        The agreement to conduct the joint training regime was signed on 15 February in Brussels by the Czech and German Defence Ministers, Martin Stropnicky and Ursula von der Leyen. "The document confirms our resolution to create more intensive joint training scenarios and, at the same time, share our knowledge and experiences. Germany is one of our key strategic partners both inside and outside the NATO region," said Martin Stropnicky.

                                        The exercise was carried out to increase mutual cooperation and improve inter-operability between the armed forces of the two countries.*

                                        The one-and-half-hour training consisted of three combat scenarios. The flights were carried out within the format of aerial combat manoeuvring 2 on 1, 1 on 1, and 2 on 2 combats. The joint training is being conducted once in every two weeks.

                                        http://www.gripenblogs.com/Lists/Pos...t.aspx?ID=1618

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                                        • Loke
                                          Rank 5 Registered User
                                          • Jun 2008
                                          • 3302

                                          “Arm seat,” says a voice in my ear. This is the point of no return, as I head to Yelahanka’s 3-kilometre runway in the rear seat of a Saab Gripen D. I depress the catch that secures the ejection seat arming mechanism and push the switch from the ‘safe’ position to ‘armed.’ This simple action, more than anything in the past ninety-odd minutes, drives home the reality of what is about to happen.
                                          http://www.gripenblogs.com/Lists/Pos...t.aspx?ID=1622

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