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  • Spitfire9
    Rank 5 Registered User
    • Jul 2008
    • 2832

    Originally posted by JSR View Post
    buying rafale will be price of France in EU as airbus and business jets sales goes down French willl have to rely on military exports.
    Sorry but I don't understand what you have written.

    I think that Belgium will not seriously consider Gripen E or Rafale or anything else apart from F-35. I think any RFP will be used simply to try to contain the cost of an F-35 deal. Because Netherlands have chosen F-35, that is what Belgium will choose as well. IMO the deal is LM's to lose if they try to squeeze too much from Belgium.
    Sum ergo cogito

    Comment

    • JSR
      JSR
      Rank 5 Registered User
      • Aug 2011
      • 4976

      Originally posted by Spitfire9 View Post
      Sorry but I don't understand what you have written.

      I think that Belgium will not seriously consider Gripen E or Rafale or anything else apart from F-35. I think any RFP will be used simply to try to contain the cost of an F-35 deal. Because Netherlands have chosen F-35, that is what Belgium will choose as well. IMO the deal is LM's to lose if they try to squeeze too much from Belgium.
      the upcoming economic pressures that are coming EU way it be willl be very hard justify imported systems.

      Comment

      • eagle
        Rank 5 Registered User
        • Jan 2000
        • 2369

        Originally posted by Loke View Post
        Belgium has a close collaboration with the Netherlands on fighter aircraft I believe, so F-35 is no doubt the most likely selection.
        Yes the Benelux countries (not to forget Luxembourg) share QRA duties since the beginning of 2017, the Belgian and Dutch air forces take turns in providing the QRA jets.
        Belgium like the Netherlands is also part of the NATO nuclear sharing program. If the want to keep it that that way, the F-35 is the only realistic option. F-18E/F, EF Typhoon and Gripen are all not nuclear capable IIRC, Rafale only with French stuff.
        How can less be more? It's impossible. More is more.
        Yngwie Malmsteen

        Comment

        • LoneWolf
          Rank 5 Registered User
          • Aug 2005
          • 75

          Originally posted by Loke View Post
          Google translated from https://www.svd.se/belgien-spanar-pa.../om/naringsliv

          Belgium no doubt will go for F-35; the real reason why they are asking Sweden to send an offer is of probably because they want to create some competition for the F-35; Gripen can compete with the F-35 on cost, however the others (in particular Typhoon and Rafale) cannot do so anymore.

          Belgium has a close collaboration with the Netherlands on fighter aircraft I believe, so F-35 is no doubt the most likely selection.
          Belgium will probably select the F-35 (and i sure hope we do...) but i wouldnt say its a sure bet. According to insider rumors, F-35 and Rafale are considered the two front runners in the competition and the later will clearly have an edge when it comes to economic offsets... so wait and see.

          And despite our close cooperation with the Dutch, there is at least one historical precedent where we went our separate ways when it comes to fighter procurement. Back in the late 60s, the Netherlands and Belgium planned to jointly buy Northrop F-5s until Belgium changed its mind and went for the Mirage 5 instead (thanks to Dassault offering us a sweet deal including local production).
          Last edited by LoneWolf; 21st March 2017, 19:02.

          Comment

          • totoro
            Rank 5 Registered User
            • Apr 2006
            • 1026

            I know this is a bit off topic, but perhaps people visiting this thread could help me out. How many batteries of rbs 97 (or Hawk) does swedish air force still have operational? And that announced modernization of 2015, how is that going? Has it been finished? Just how much were those Hawks modernized?

            Comment

            • maurobaggio
              Rank 5 Registered User
              • Jul 2008
              • 521

              Originally posted by halloweene View Post
              Nope, no RFI to France (and not sure there ever was a RFI...)


              Agree. This whole story since MMRCA cancellation smells rivalry between Parrikar and Modi.


              India is sensed to have specified a single engine for IAF, but Boeing pitched its F-18...

              Has India canceled the acquisition of the 36 Rafale F3?

              If India did not send an RFI to France it is because there is no need this, since it was the Rafale F3 that won the MMRCA program, although the program has been suspended so far, India has chosen to buy 36 Rafale F3.

              During the 2000s there were several criticisms that MMRCA program from India, once it had not been included the STOBAR fighters from IN to equip its new aircraft carrier INS Vikramaditya.

              The basic idea should be chosen a fighter even in different versions that could have been equipped both IAF and IN.

              For several reasons as schedule and political, the IN has been chosen the MiG 29K, and thus the IAF could have been moving with more freedom to choice among the candidates available without to opt for candidates that has been already developed maritime versions (F/A 18E/F, Rafale M and MiG 35) at this time.

              Coincidentally, the Rafale F3 won the MMRCA program, and at the same time rumors had been surfaced that the Rafale M would be acquired in the future to equip a new aircraft carrier from India.

              India has done their homework about the failures of the MMRCA program, as well as the emphasis on Make in India has not been applied only with IAF, but for IN as well, so anyone that has not developed such maritime version for India untill 2021, probably will not win in India either with IAF and IN.

              If SAAB could have not been removed the Gripen M from the never land until 2021, it certainly will not be India that will taken out the Gripen M from never land with all risks , after all the Rafale F3/M still in the leadership and the F/A 18 E/F has been follow in second place both with IAF e IN, even taking out the F 35A/B/C, the Gripen E and F 16 should have been competing for the 4th place even with IAF.

              Comment

              • halloweene
                Rank 5 Registered User
                • Jan 2012
                • 4350

                Originally posted by maurobaggio View Post
                Has India canceled the acquisition of the 36 Rafale F3?

                If India did not send an RFI to France it is because there is no need this, since it was the Rafale F3 that won the MMRCA program, although the program has been suspended so far, India has chosen to buy 36 Rafale F3.

                During the 2000s there were several criticisms that MMRCA program from India, once it had not been included the STOBAR fighters from IN to equip its new aircraft carrier INS Vikramaditya.

                The basic idea should be chosen a fighter even in different versions that could have been equipped both IAF and IN.

                For several reasons as schedule and political, the IN has been chosen the MiG 29K, and thus the IAF could have been moving with more freedom to choice among the candidates available without to opt for candidates that has been already developed maritime versions (F/A 18E/F, Rafale M and MiG 35) at this time.

                Coincidentally, the Rafale F3 won the MMRCA program, and at the same time rumors had been surfaced that the Rafale M would be acquired in the future to equip a new aircraft carrier from India.

                India has done their homework about the failures of the MMRCA program, as well as the emphasis on Make in India has not been applied only with IAF, but for IN as well, so anyone that has not developed such maritime version for India untill 2021, probably will not win in India either with IAF and IN.

                If SAAB could have not been removed the Gripen M from the never land until 2021, it certainly will not be India that will taken out the Gripen M from never land with all risks , after all the Rafale F3/M still in the leadership and the F/A 18 E/F has been follow in second place both with IAF e IN, even taking out the F 35A/B/C, the Gripen E and F 16 should have been competing for the 4th place even with IAF.
                I just mean that i know there wasn't any RFI sent to France for the single engine fighter deal. I just kind of remember (if i'm not wrong) that "unsollicited offers" arrived from LM and SAAB to India before anyone ever heard about a RFI noone ever saw...

                Comment

                • BlackArcher
                  Rank 5 Registered User
                  • Dec 2010
                  • 4285

                  Originally posted by Loke View Post
                  I found this interesting article on the FCS of Gripen:

                  http://www.icas.org/ICAS_ARCHIVE/ICA...RS/ICA3113.PDF



                  What does this actually mean? Is the (positive) AOA limit 26 or 55? Or both?


                  I found also this:



                  An extra 3g that is quite a lot!




                  http://ac.els-cdn.com/S1474667015332...dbaa31709b3d97

                  So it seems the "soft stop" AOA is 26 degrees; does this then imply there is a "hard stop" AOA, as there is for the g above corner speed?
                  The Gripen's AoA limit, as per multiple authentic sources (FG for instance) is 26 deg. In the Region II of the FCS (past 26 deg AoA), the Gripen's FCS would basically auto-recover the airplane to prevent further departure from controlled flight.

                  The auto-recovery function is normally engaged in both region II and III but the pilot has an option to switch between auto-recovery and direct-link mode in region III. The direct-link mode is used to investigate spin behaviour. The auto-recovery
                  mode is divided into three phases:
                  1. Roll damping.
                  2. Yaw damping (anti spin)
                  3. Nose down (recovery from high/low AOA)

                  In the event of a departure, the FCS will first try to reduce any roll oscillation, then stop the yaw rate and finally pitch the nose down by using AOA and pitch rate as feedback signals.
                  So it's clear that in normal controlled flight, the Gripen cannot exceed 26 deg AoA. That is part of the care-free handling of the Gripen and all other FBW controlled airplanes.

                  Comment

                  • hopsalot
                    Senior Member
                    • Aug 2012
                    • 3166

                    Originally posted by BlackArcher View Post
                    The Gripen's AoA limit, as per multiple authentic sources (FG for instance) is 26 deg. In the Region II of the FCS (past 26 deg AoA), the Gripen's FCS would basically auto-recover the airplane to prevent further departure from controlled flight.



                    So it's clear that in normal controlled flight, the Gripen cannot exceed 26 deg AoA. That is part of the care-free handling of the Gripen and all other FBW controlled airplanes.
                    Indeed, we can go ahead and close out the Gripen AoA discussion.

                    Comment

                    • obligatory
                      Senior Member
                      • Oct 2008
                      • 7043

                      There is a possibility for the pilot to override the soft
                      stop in an emergency situation and pull the control
                      stick back to the hard stop and thus get an extra 3g,
                      when aircraft speed is above 600 km/h. This requires
                      an extra stick force of approximately 135 N.

                      i didnt know gripen has an override mode over the normal soft limited envelope,
                      how much more AoA is required to add another another 3g ?

                      altho the graph display up to 90 degree AoA, he discusses mostly only up to 45 AoA
                      Last edited by obligatory; 22nd March 2017, 06:16.

                      Comment

                      • Loke
                        Rank 5 Registered User
                        • Jun 2008
                        • 3302

                        Originally posted by BlackArcher View Post
                        The Gripen's AoA limit, as per multiple authentic sources (FG for instance) is 26 deg. In the Region II of the FCS (past 26 deg AoA), the Gripen's FCS would basically auto-recover the airplane to prevent further departure from controlled flight.



                        So it's clear that in normal controlled flight, the Gripen cannot exceed 26 deg AoA. That is part of the care-free handling of the Gripen and all other FBW controlled airplanes.
                        True, however in "normal flight" Gripen is also limited to 9g; in the article linked to above, it says that the pilot can override the 9g limit and go up to 12g. This is of course not normal, and is normally never done. However this does not mean that the capability is not there.


                        My question was if something similar was possible also for AOA.
                        The aircraft is still statically unstable in this region and a non-linear prediction of AOA (alpha-dot) and an increasing feedback is used to recover the a/c. In the last region III, from AOA above 55 (45 on re-entry) or below -25 (-20 on re-entry), the aircraft is statically stable and the basic control law is full feed back, with auto-recovery from out of control.
                        "an increasing feedback is used to recover the a/c". What does this mean?

                        Also note in the other article I linked to it says:


                        With a pitch stick command to the softstop, the pilot commands load factor to the load factor limit, when the aircraft speed is above corner speed (corner speed is approximately 600 km/h). Below corner speed a pilot command to the soft stop means an angle of attack command to the angle of attack limit. When the control stick is pushed max forward, the pilot commands normal load factor to the negative load factor limit and below corner speed negative angle of attack to the negative angle of attack limit. The maximum stick forward position is -7 degrees. There is a possibility for the pilot to override the soft stop in an emergency situation and pull the control stick back to the hard stop and thus get an extra 3g, when aircraft speed is above 600 km/h. This requires an extra stick force of approximately 135 N.
                        So below corner speed moving the stick to the soft stop means an angle of attack command to the angle of attack limit. In an emergency situation the soft stop can be overriden and above corner speed this will give an extra 3g (bringing max g to 12); however it does not say what will happen if the pilot overrides the soft stop below the corner speed.

                        A book written by a Norwegian author (on the F-35) claims that max AOA for Gripen is 50; also an F-16 pilot has said he as been told Gripen can go up to 50. However you are right that official sources do state max AOA is 26 degrees, so probably nothing happens if the pilot moves the stick from softstop to hardstop below corner speed?

                        Comment

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

                          Pushing past the soft stop may give higher AoA and more "g" above corner speed, does not mean 12g is available. It's whatever the max AoA allowed by the FCS within a given loadout and configuration. Assuming the aircraft is clean (I don't know if the Gripen is 9g capable with full fuel), then according to the above excerpt, then the FCS seems to allow for momentary excess g up to 12.

                          The corner speed is 323 knots, pretty good (assuming it's at 15,000 feet). The F-16's is around 340-350 knots.

                          Comment

                          • hopsalot
                            Senior Member
                            • Aug 2012
                            • 3166

                            Originally posted by obligatory View Post
                            There is a possibility for the pilot to override the soft
                            stop in an emergency situation and pull the control
                            stick back to the hard stop and thus get an extra 3g,
                            when aircraft speed is above 600 km/h. This requires
                            an extra stick force of approximately 135 N.

                            i didnt know gripen has an override mode over the normal soft limited envelope,
                            how much more AoA is required to add another another 3g ?

                            altho the graph display up to 90 degree AoA, he discusses mostly only up to 45 AoA

                            Above corner velocity is not where you are going to find high AoA, even if you were pulling 12gs. The types of high AoA maneuvers we have been discussing are all going to occur at low speeds, approaching a stall or even post-stall.

                            Comment

                            • obligatory
                              Senior Member
                              • Oct 2008
                              • 7043

                              i think what blackarcher meant was: in software controlled flight, gripen does not exceed 26 AoA,
                              software will see to it that it doesnt go further.
                              i wonder if its common to override software limit among regular pilots ?
                              is there disciplinary measures taken if they do ?
                              it may not be the smartest thing to do in a many vs many scenario,
                              but i think the pilots will have an itch to pull 12g on occasion
                              Last edited by obligatory; 22nd March 2017, 11:20.

                              Comment

                              • hopsalot
                                Senior Member
                                • Aug 2012
                                • 3166

                                Originally posted by Loke View Post

                                A book written by a Norwegian author (on the F-35) claims that max AOA for Gripen is 50; also an F-16 pilot has said he as been told Gripen can go up to 50. However you are right that official sources do state max AOA is 26 degrees, so probably nothing happens if the pilot moves the stick from softstop to hardstop below corner speed?
                                Going out of control in combat is very bad... there are reasons why a pilot might want to risk going over 9Gs briefly in a lightly loaded aircraft. Exceeding the aircraft max safe AoA is not going to be something that is advisable.

                                It is possible that there is some case (speed/altitude/load and/or a specific way of getting the aircraft there)where a Gripen could operate at 50 AoA while under control, but clearly it is a pretty rare case otherwise the FCS wouldn't limit it to 26.

                                Comment

                                • obligatory
                                  Senior Member
                                  • Oct 2008
                                  • 7043

                                  errr, "the aircraft could be “parked” at 70 to 80 degrees of alpha. " (parked as in, controlled flight, indefinitely)
                                  why would it have issues doing 50 aoa ? other than the fact that it slow the fighter down, that is

                                  Comment

                                  • obligatory
                                    Senior Member
                                    • Oct 2008
                                    • 7043

                                    The JAS 39 Gripen is an aerodynamic statically
                                    unstable aircraft in the pitch axis at subsonic speeds
                                    with a time to double amplitude of approximately 0.4
                                    seconds.

                                    correct me if i'm wrong, but does this mean pitch doubles every 0.4 seconds ?
                                    i wonder if any fighter out there bar EF has this rate of pitch,
                                    f-22 might be able to thanks to thrust vectoring but then again there were comments
                                    it had issues with EF
                                    Last edited by obligatory; 22nd March 2017, 11:37.

                                    Comment

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

                                      Originally posted by obligatory View Post
                                      errr, "the aircraft could be parked at 70 to 80 degrees of alpha. " (parked as in, controlled flight, indefinitely)
                                      why would it have issues doing 50 aoa ? other than the fact that it slow the fighter down, that is
                                      To reiterate for those who still haven't grasped the concept- at high AoA the control surfaces on the tail are blocked from airflow by the fuselage. Modern fighters have leading edge devices that can generate strong vortices. Twin tail aircraft can still maintain control at very high AoA due to the tails. Single vertical stabilizer aircraft lose yaw control when the tail does not interact with the vortices. Same is true with the stabilator though many modern fighter use large horizontal stabs so they they do not lose pitch authority at higher AoA.

                                      There is a drawback to twin tails; high buffeting at elevated angles of attack, added weight from both the twin tails and the fact that the tails have to be strong. As a result twin tails such as the Mig-29, F-15, F-18 (and according to testing, the F-35) often suffer fatigue in the vertical stabs. No free ride.

                                      Examples:
                                      Here you see the F-18 at high alpha with vortex coming of leading edge hitting the vertical stabs:
                                      Click image for larger version

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                                      another:
                                      Click image for larger version

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                                      Here is an F-16 at high alpha (notice the tail and vortex coming of leading edge):
                                      Click image for larger version

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                                      here is the X-31 (single tail- with TVC to control yaw and pitch):
                                      Click image for larger version

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                                      From the NASA X-31 study:
                                      They recognized
                                      that, when flying in this very slow post-stall regime, the effectiveness of
                                      pure aerodynamic controls is limited, but that it was possible to minimize the
                                      adverse aerodynamics to ameliorate the issue. But they also realized that additional
                                      control would be needed. One possible solution was to employ thrust
                                      vectoring of the engine exhaust to provide sufficient forces and moments to
                                      control the aircraft
                                      - https://www.nasa.gov/sites/default/f..._the_Stall.pdf

                                      So, no the Gripen is not in controlled flight at very high AoA, without TVC it wouldn't be able to (same as F-16, Typhoon, etc.) The canards help make it safe to exceed the control authority of the tail as they aid with recovery, as the quote in the Rafale thread stated.
                                      Last edited by FBW; 22nd March 2017, 13:52.

                                      Comment

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

                                        A good overview of the history of canards and high AoA tendencies (only a brief mention of Jas-39)

                                        https://ntrs.nasa.gov/archive/nasa/c...9870013196.pdf

                                        Addition- @Obligatory
                                        The JAS 39 Gripen is an aerodynamic statically
                                        unstable aircraft in the pitch axis at subsonic speeds
                                        with a time to double amplitude of approximately 0.4
                                        seconds.
                                        -that has nothing to do with (controlled) pitch rate. All longitudinally unstable designs oscillate, they pitch up (negative static stability), that is why they have FCS.
                                        Last edited by FBW; 22nd March 2017, 12:31.

                                        Comment

                                        • TomcatViP
                                          Rank 5 Registered User
                                          • Nov 2011
                                          • 6107

                                          And the time to double oscillations is what drive the level stability of the FCS. You want that time to remain in a certain range and give more or less control authority depending if you are outside that margin.
                                          In other words, if you time to double the amplitude is low, your control surface will be more restricted in travel to prevent an unexpected departure than otherwise or the plane admissible AoA will be caped at a lower value. The "how Low" is dependent of the airframe and flight range.
                                          Last edited by TomcatViP; 23rd March 2017, 00:38.

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