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Thread: SAAB Gripen and Gripen NG thread #4

  1. #1411
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    In fact, India has not been shown such highly interest in the Gripen E, since the Gripen E were rejected in the MMRCA program, as well as India has been sending RFI for several countries like France and Russia that doesn't produce fighters with a single engine like the Gripen E or F 16.
    Nope, no RFI to France (and not sure there ever was a RFI...)

    That was less the IAF and more the MoD with its 'Make-in-India' directives for which the 'free' F-16 assembly line was a particularly attractive idea. With the defence minister Parrikar gone, and no formal process initiated, it remains to whether the plan will see light of day.
    Agree. This whole story since MMRCA cancellation smells rivalry between Parrikar and Modi.

    Didn't IN specify they want a twin-engined fighter, so that rules out both F-35 and Gripen Maritime? Did it change again?
    India is sensed to have specified a single engine for IAF, but Boeing pitched its F-18...

  2. #1412
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    Quote Originally Posted by Yama View Post
    Didn't IN specify they want a twin-engined fighter, so that rules out both F-35 and Gripen Maritime? Did it change again?
    No such engine requirement was specified in the RFI.

    Tender Document

  3. #1413
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    Quote Originally Posted by halloweene View Post
    Agree. This whole story since MMRCA cancellation smells rivalry between Parrikar and Modi.
    That's ridiculous Hallow. Modi & Parrikar are no more rivals than Putin & Shoygu or Trump & Mattis. Parrikar was appointed to his position (from relative obscurity) by Modi and doesn't pose the remotest threat to the PM. As far as defence procurement is concerned, we on places like Keypub tend to think of these decision as ultra-important, but Modi isn't expected to nor has any interest in micromanaging ministry matters. Those responsibilities have been delegated for a reason with the PM only specifying general policy (eg. Make-in-India). I think what you're confused about is his decision to order the Rafales off-the-shelf. He was pitched a deal that he accepted and the MoD obeyed the PMOs directions. Don't mistake that for some emotional or personal investment on his part in French wares (or Russian/US equipment for that matter).

  4. #1414
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    Quote Originally Posted by Yama View Post
    Didn't IN specify they want a twin-engined fighter, so that rules out both F-35 and Gripen Maritime? Did it change again?
    The RFI issued by India did not specify how many engines.

  5. #1415
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    Quote Originally Posted by Vnomad View Post
    That was less the IAF and more the MoD with its 'Make-in-India' directives for which the 'free' F-16 assembly line was a particularly attractive idea.
    That was exactly my point; this is about politics.

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    Quote Originally Posted by Vnomad View Post
    No such engine requirement was specified in the RFI.
    I am aware of that, but Parrikar said in January that Navy was looking for a twin-engined fighter.

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    Belgium wants a concrete offer of new fighter aircraft from Sweden. Will it be a business buys Belgium 34 plan of the new version of Gripen and the price tag is estimated to be around 40 billion.
    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.

  8. #1418
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    Gripen FCS limits

    I found this interesting article on the FCS of Gripen:

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

    The high AOA Flight Control Laws (FCL) are divided into three different AOA regions as shown in figure 2.
    Region I is the normal flight envelope where the limits depend on external stores, flight condition and fuel weight. All information is automatically sensed and the FCS adjusts the FCL between three different values of AOAlimit and four levels of maximum roll rate. The second region (II) is divided into two separate AOA segments. The segment on the positive side is between the positive AOA limit up to 55°. The segment on the negative side is between the negative AOA limit down to -25°. 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.
    What does this actually mean? Is the (positive) AOA limit 26 or 55? Or both?


    I found also this:

    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.
    An extra 3g that is quite a lot!

    The angle of attack limiter is active below corner speed (corner speed is approximately 600 km/h). It will keep the aircraft from going out of control to a high angle of attack situation. For full pitch stick aft to the soft stop the pilot commands angle of attack to the angle of attack limit and for full pitch stick forward, the pilot commands angle of attack to the negative angle of attack limit. The control laws for the angle of attack limiter is similar to the control laws for the load factor limit (see figure 1.4.2).
    The JAS 39 Gripen is a 26 degree angle of attack aircraft for the light external store configurations and 20 degrees for the most heavy external store configurations. The variation of angle of attack with roll stick position is used to give roll command priority, when the pilot demands roll rate.
    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?

  9. #1419
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    Danske Bank ("Danish Bank") analysts have been in India, and conclude that they believe Saab has a real possibility of sales in India:

    Danske Bank is still very optimistic set to Saab's opportunities in India, after like a year ago have been in the country and investigated the matter, and continue to see upside potential in the share.

    It appears from the bank's customer letter on Tuesday.

    This time based conclusions including that the bank has entered Saab's advisor ("Special Advisor") in India following an air show.

    "We believe that the opportunities for Saab in the country is very positive, with several mega orders on the table and with unusually high probability of Saab to land more orders," writes Danish, and mentions that Brazil Gripen Order seems to be a strong support for the Swedish defense group in India .
    Google translated from: http://www.di.se/nyheter/danske-mega...grar-for-saab/

  10. #1420
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    Quote 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.
    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.

  11. #1421
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    Quote 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

  12. #1422
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    Quote 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.

  13. #1423
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    Quote 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.
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  14. #1424
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    Quote 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 at 18:02.

  15. #1425
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    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?
    Binkov's Battlegrounds - military analysis videos

    New video available! F-35 vs Su-35 (Part 2/2, the verdict)

  16. #1426
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    Quote 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.

  17. #1427
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    Quote 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...

  18. #1428
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    Quote 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.

  19. #1429
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    Quote 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.

  20. #1430
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    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 at 05:16.

  21. #1431
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    Quote 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?

  22. #1432
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    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.

  23. #1433
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    Quote 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.

  24. #1434
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    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 at 10:20.

  25. #1435
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    Quote 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.

  26. #1436
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    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

  27. #1437
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    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 at 10:37.

  28. #1438
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    Quote 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 at 12:52.

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    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 at 11:31.

  30. #1440
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    4,452
    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; 22nd March 2017 at 23:38.

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