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SAAB Gripen and Gripen NG thread #4

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  • Urban
    Rank 4 Registered User
    • Jan 2015
    • 121

    @hopsalot ".. and what is the Gripen NG's supersonic range?"

    http://techworld.idg.se/2.2524/1.174...cker-och-stark

    According to this article Gripen c dry thrust is 1.2kg/s and afterburner is 4kg/s. Ill give you the engine burn times dry and wet Measured on rm12 but with the gripen E's fuel(internal).
    This is only theoretical max burns. And with not exactly (but very close to, engine).
    Full dry thrust maximum burntime = 1.2kg/s*60=72kg/min. Internal tank on E version is 3400kg/72kg=47,2 minutes
    Full wet thrust maximum burntime= 4kg/s*60=240kg/min. 3400kg/240=14,16 minutes

    Ill give you an example......
    Now if you max dry thrust a gripen e , it will fly somewhere between mach 1.1 mach 1.25 depending on load of stuff BUT having started with say two droptanks (subsonic), which where dropped before engagement and returning back with pretty much full tank.
    It is very likely that Supercruising back for say 47,2 minus 12 minutes for safety ...35minutes would be quite possible. With the result in a quick and IR-low return and rearm. The range with mach 1.2 (having left the battle and all) is converted to 1468kph.
    So 35 minutes would be 856,3km flown. Super cruise on internal one direction.

    Now it could be used to get close without being seen and with a very low reaction time for the enemy and a whole lot of other type of tactics.... I am not a pilot, but to be able to get out without using the burner to maintain high speed, just has to feel good. Leaving the sound behind makes the overflight dead silent until they already passed, making it harder to position.

    Talking super cruise in general the only speed that is worth anything, is a usefull one an that would be a cruise for most fighters between 1-1.3 where 1+++ is rafale eurofighter and gripen e and the 1.3 might be f-22. F-22 get bingo fuel in no time, maxing out its dry thrust. Unfortunately that is true for most "high" powered aircrafts.
    Max speed super cruise is nothing to look at. Check the fuel and just use math and you will see that only lower speeds are useful.

    Comment

    • mig-31bm
      Rank 5 Registered User
      • Oct 2013
      • 2140

      Originally posted by Urban View Post
      @hopsalot ".. and what is the Gripen NG's supersonic range?"

      http://techworld.idg.se/2.2524/1.174...cker-och-stark

      According to this article Gripen c dry thrust is 1.2kg/s and afterburner is 4kg/s. Ill give you the engine burn times dry and wet Measured on rm12 but with the gripen E's fuel(internal).
      This is only theoretical max burns. And with not exactly (but very close to, engine).
      Full dry thrust maximum burntime = 1.2kg/s*60=72kg/min. Internal tank on E version is 3400kg/72kg=47,2 minutes
      Full wet thrust maximum burntime= 4kg/s*60=240kg/min. 3400kg/240=14,16 minutes

      Ill give you an example......
      Now if you max dry thrust a gripen e , it will fly somewhere between mach 1.1 mach 1.25 depending on load of stuff BUT having started with say two droptanks (subsonic), which where dropped before engagement and returning back with pretty much full tank.
      It is very likely that Supercruising back for say 47,2 minus 12 minutes for safety ...35minutes would be quite possible. With the result in a quick and IR-low return and rearm. The range with mach 1.2 (having left the battle and all) is converted to 1468kph.
      So 35 minutes would be 856,3km flown. Super cruise on internal one direction.
      That calculation is wrong, Thrust specific fuel consumption varied significantly with altitude and speed

      Comment

      • MSphere
        Senior Member
        • Feb 2010
        • 8983

        Originally posted by mig-31bm View Post
        That calculation is wrong, Thrust specific fuel consumption varied significantly with altitude and speed
        If it's wrong, then make corrections.. Nobody has time to study the myriad of graphs you tend to post.

        Comment

        • mig-31bm
          Rank 5 Registered User
          • Oct 2013
          • 2140

          Originally posted by MSphere View Post
          If it's wrong, then make corrections.. Nobody has time to study the myriad of graphs you tend to post.
          If you read the post carefully, you will realize that i already made correction (point out where he is wrong) , and the graph is rather simple for most people to understand what it say
          Last edited by mig-31bm; 8th February 2016, 10:38.

          Comment

          • MSphere
            Senior Member
            • Feb 2010
            • 8983

            Pointing out where someone is wrong does not suffice. Either you got a better calculation that he has or you got nothing..

            Comment

            • mig-31bm
              Rank 5 Registered User
              • Oct 2013
              • 2140

              Originally posted by MSphere View Post
              Pointing out where someone is wrong does not suffice. Either you got a better calculation that he has or you got nothing..
              Very funny that you change your stand now, given the fact that you often have the habit of never backup what you said with calculations
              Just because i didnt give a number of my own doesn't mean what i say was wrong, his calculation is ridiculous regardless, i didn't give any number due to the fact that none of us know the dynamic thrust of Gripen NG at altitude and mach 1.2 so any so called " calculation" are 85% BS or bias

              Comment

              • moon_light
                Rank 5 Registered User
                • May 2012
                • 1029

                Let say TSFC of F414G at mach 1.2 is 2 lb/(h. lbf)
                Gripen NG internal fuel load is 7300 lbs
                dry thrust is 12000 lbs
                [7300/ (12000*2)] * 60 = 18 minutes
                however you need fuel to take off, landing, climb, accelerate, ( and may be even dogfight)
                so IMHO, Gripen NG realistically only has enough fuel to supercruise for around 10 minutes (will be less when including subsonic cruise)
                Last edited by moon_light; 8th February 2016, 11:39.

                Comment

                • Urban
                  Rank 4 Registered User
                  • Jan 2015
                  • 121

                  @mig-31bm
                  So because you add other factors in, the calculations are wrong ? Allow me to smile. I also pointed out theoretical part of it.

                  You are right that the consumption increases, but it is an lesser problem for an aircraft with and smaller engine that has less consumption. Because they in general draw much less fuel.
                  Its also a lesser problem for aircraft made to super cruise and supersonic flight from the beginning.
                  Last edited by Urban; 8th February 2016, 12:21.

                  Comment

                  • Urban
                    Rank 4 Registered User
                    • Jan 2015
                    • 121

                    Originally posted by moon_light View Post
                    Let say TSFC of F414G at mach 1.2 is 2 lb/(h. lbf)
                    Gripen NG internal fuel load is 7300 lbs
                    dry thrust is 12000 lbs
                    [7300/ (12000*2)] * 60 = 18 minutes
                    however you need fuel to take off, landing, climb, accelerate, ( and may be even dogfight)
                    so IMHO, Gripen NG realistically only has enough fuel to supercruise for around 10 minutes (will be less when including subsonic cruise)
                    Wrong ! Internal tank on E version is 3400kg/72kg=47,2 minutes split in two that would be 23,6 minutes. And remember we are talking maximum dry thrust here. what sfc (grams) are you using ? Link?
                    Last edited by Urban; 8th February 2016, 12:16.

                    Comment

                    • obligatory
                      Senior Member
                      • Oct 2008
                      • 7043

                      using static fuel consumption under afterburner to calculate consumption
                      under military power at height where consumption goes down wtf ??!

                      Comment

                      • Robbiesmurf
                        Rank 5 Registered User
                        • Jul 2014
                        • 587

                        Originally posted by mig-31bm View Post
                        That calculation is wrong, Thrust specific fuel consumption varied significantly with altitude and speed
                        If that is specific fuel consumption then it is wrong.
                        SFC= lb fuel/lb thrust/ hr
                        Most gas turbines run at around 0.6-0.7 until reheat is engaged. That increases total thrust but also has a poor thermal efficiency, ergo, the SFC is worse.
                        TOTAL fuel consumption is dependent on engine rpm (pressure ratio), altitude (amplification ratio) and velocity (drag rule/ram effect).
                        That graph looks at best suspect, probably something cooked up by someone who has heard a bit and thinks he knows....
                        Data is normally gathered by tests carried out on altitude test-beds or by flight tests. Nowadays, after so much research they do not have to test as rigorously as they did decades ago, merely confirm knowledge previously and expensively garnered. These figures are empirical and in general unpublished to the public....
                        Your graphs and figures are therefore by virtue, without value. who actually plots these graphs, someone who works in the business or someone who would like to?

                        Comment

                        • Spitfire9
                          Rank 5 Registered User
                          • Jul 2008
                          • 2832

                          Originally posted by Robbiesmurf View Post
                          SFC= lb fuel/lb thrust/ hr
                          Most gas turbines run at around 0.6-0.7 until reheat is engaged.
                          So ball park fuel burn figure for 12,000 lb thrust is 7,200lb-8,400lb per hour? Gripen can maintain supersonic speed on 12,000lb thrust with a minimal drag load (eg 2 x A2A missiles). What supersonic speed does the aircraft need to reach before transonic drag starts to reduce?
                          Sum ergo cogito

                          Comment

                          • obligatory
                            Senior Member
                            • Oct 2008
                            • 7043

                            how long a fighter will remain in transonic is very different from fighter to fighter,
                            depending on wing sweep, area distribution, wing thickness, etc,
                            deltas are as built for transonic, out of current fighters, gripen is hard to beat, only competition being possibly EF,
                            F-16 exit around M1.15, gripen & EF around M1.05, F-35 somewhere after M1.2
                            http://history.nasa.gov/SP-367/f91.htm
                            http://history.nasa.gov/SP-367/chapt5.htm

                            Comment

                            • FBW
                              FBW
                              Rank 5 Registered User
                              • Dec 2011
                              • 3295

                              Originally posted by obligatory View Post
                              how long a fighter will remain in transonic is very different from fighter to fighter,
                              depending on wing sweep, area distribution, wing thickness, etc,
                              deltas are as built for transonic, out of current fighters, gripen is hard to beat, only competition being possibly EF,
                              F-16 exit around M1.15, gripen & EF around M1.05, F-35 somewhere after M1.2
                              http://history.nasa.gov/SP-367/f91.htm
                              http://history.nasa.gov/SP-367/chapt5.htm
                              Sigh, your "analysis" would have been better served to just simply point out aspects of the Gripen design favorable to transonic drag reduction. When you started putting numbers on various aircraft, it becaume a fail.

                              As you pointed out, there are several factors to consider when assessing wave drag. Low aspect ratio and the use of supercritical wings make guessing wave drag based on sweep angle a fools game.

                              Comment

                              • Spitfire9
                                Rank 5 Registered User
                                • Jul 2008
                                • 2832

                                Originally posted by FBW View Post
                                Sigh, your "analysis" would have been better served to just simply point out aspects of the Gripen design favorable to transonic drag reduction. When you started putting numbers on various aircraft, it becaume a fail.
                                obligatory answered my question well enough. Just wanted some guidance. That is what I got. The deltas - Gripen, Typhoon (and presumably Rafale) - appear more favourably shaped for lower supersonic speed transonic drag reduction. I wonder if they win on subsonic transonic drag, too.
                                Sum ergo cogito

                                Comment

                                • FBW
                                  FBW
                                  Rank 5 Registered User
                                  • Dec 2011
                                  • 3295

                                  Originally posted by Spitfire9 View Post
                                  obligatory answered my question well enough. Just wanted some guidance. That is what I got. The deltas - Gripen, Typhoon (and presumably Rafale) - appear more favourably shaped for lower supersonic speed transonic drag reduction. I wonder if they win on subsonic transonic drag, too.
                                  Delta wings have higher drag overall, they are less efficient at subsonic speeds, but have the benefit of higher critical mach. If Obligatory's answer suits you, fine. But it is deficient in the assumption that having a delta wing is the primary factor in reducing transonic drag. (Think YF-102)

                                  The numbers.... like mach 1.05? contrived out of thin air.

                                  Comment

                                  • mig-31bm
                                    Rank 5 Registered User
                                    • Oct 2013
                                    • 2140

                                    Originally posted by Urban View Post
                                    @mig-31bm
                                    So because you add other factors in, the calculations are wrong ? Allow me to smile. I also pointed out theoretical part of it.
                                    The things is , the factor i added in will change the result significantly not just a little bit
                                    Originally posted by Urban View Post
                                    You are right that the consumption increases, but it is an lesser problem for an aircraft with and smaller engine that has less consumption. Because they in general draw much less fuel.
                                    They also carry much less fuel in the first place
                                    Originally posted by Urban View Post
                                    Its also a lesser problem for aircraft made to super cruise and supersonic flight from the beginning.
                                    Not really , if all operate in dry thrust ,then engine of supercruise aircraft will often be more thirsty ( low bypass ratio , run mostly with the core )

                                    Comment

                                    • mig-31bm
                                      Rank 5 Registered User
                                      • Oct 2013
                                      • 2140

                                      Originally posted by Urban View Post
                                      Wrong ! Internal tank on E version is 3400kg/72kg=47,2 minutes split in two that would be 23,6 minutes.
                                      according to this imagine from SAAB internal fuel load of Gripen E is 7300 pounds

                                      Originally posted by Urban View Post
                                      And remember we are talking maximum dry thrust here. what sfc (grams) are you using ? Link?
                                      I think he just scale it up from the graph
                                      Originally posted by obligatory View Post
                                      using static fuel consumption under afterburner to calculate consumption
                                      under military power at height where consumption goes down wtf ??!
                                      at the same speed , then consumption will go down as you go higher , but if you increase your speed then fuel consumption will increase
                                      Originally posted by Robbiesmurf View Post
                                      SFC= lb fuel/lb thrust/ hr
                                      Most gas turbines run at around 0.6-0.7 until reheat is engaged.
                                      not at all speed and altitude though

                                      Originally posted by Robbiesmurf View Post

                                      Your graphs and figures are therefore by virtue, without value. who actually plots these graphs, someone who works in the business or someone who would like to?
                                      these people

                                      Comment

                                      • Loke
                                        Rank 5 Registered User
                                        • Jun 2008
                                        • 3302

                                        Originally posted by mig-31bm View Post
                                        according to this imagine from SAAB internal fuel load of Gripen E is 7300 pounds
                                        According to this link from Saab internal fuel of Gripen NG is 3400 kg:

                                        http://saab.com/globalassets/commerc...g-brochure.pdf

                                        Not that the difference between 7300 lbs and 3400 kg is huge... (195 lbs or 88 kg, or 2.5%)

                                        Comment

                                        • Robbiesmurf
                                          Rank 5 Registered User
                                          • Jul 2014
                                          • 587

                                          Originally posted by Spitfire9 View Post
                                          So ball park fuel burn figure for 12,000 lb thrust is 7,200lb-8,400lb per hour? Gripen can maintain supersonic speed on 12,000lb thrust with a minimal drag load (eg 2 x A2A missiles). What supersonic speed does the aircraft need to reach before transonic drag starts to reduce?
                                          Good questions, the first sounds about right. The second, dependent on the design. They understand the research carried out by Whitcomb and kuchemann and make use of their discovery.
                                          Do remember though that supercruise doe allow them to run longer. due to not using the reheat. An old example of the difference. A Lightning F3 would have about 45 minutes of flight not using the reheat much (take off). Full reheat, about 7 minutes..... We once tested an F6 (Bigger tank) at full reheat for 5 minutes on the ground. It went from full to almost empty.
                                          Last edited by Robbiesmurf; 8th February 2016, 19:35.

                                          Comment

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