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Thread: Rafale news & discussion part XVI

  1. #2851
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    Quote Originally Posted by FBW View Post
    I provided you with everything you need to understand the topic. There is no magic, no unknown in flight control. You are the one that needs to provide counter evidence that the Rafale has a magical control of yaw when the vertical stab is blocked in high AoA, it is exactly that simple. If you can't, (which you cant't) then you'll get why the F-16, Rafale, and Gripen are AoA limited to around 30 degrees operationally. Testing is a different matter as they have sufficient margin of recovery.

    Please, if you are so confident, show me a study where a single vertical tail ( without tvc) can operate at very high alpha, with full control. I've provided you with articles in this and the Gripen thread that show they can't, period.
    if your faith brings to you the need to speak about magic all the time, that's your problem.... You have operational aircraft that operate safely without any vertical tail at all, and without TVC either, like the B-2. They don't fall from the sky at any windshear, any pitch up, or other variation in their flight (or load for that matter)... You are the one to claim you know why the value chosen is exactly that one... you have to prove it. I say they tested the thing at almost 3 times that value without departing controlled flight (fact), so why have they chosen to stay at 30, and not 35, or 28 or any other value, I don't know. How am I supposed to provide data to prove that "we don't have the data relevant to the reasons of that particular choice"? You state that YOU KNOW WHY, so YOU ARE TEH ONE HAVING TO PROVIDE VALID DATA TO SHOW IT.. as long as you don't have data related to that particular decision on that particular aircraft, all you can put forward, as you did until now, are facts that, while interesting in their own right, are irrelevant to this discussion

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    Quote Originally Posted by Yama View Post
    I don't understand what this discussion is about anymore (if I ever did). Surely it is obvious to any common sense person that AoA limitations are not put there just for the heck of it? In some cases there might be a 'soft limit' which can be exceeded if a situation demands but even that has a rationale behind it.
    That's what several of us have been saying all the time: they had their reasons, but up to now, nobody could bring solid information bout these reasons.. and we have a bunch of guys who are all over the place claiming "because it couldn't go any further" posting explanations about other types of aircraft none of which uses the same layout/FCS as the one we talk about

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    Minister of defence JY Le Drian announced start of first F4 standard. More netcentric, new missiles, sensors and engine evolution.

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    Too cool, I repeat. I have given u the explanation, then I gave links in case some still doubted why. The B-2 example proves my point. Flying wings use split ailerons in some cases. And no, they cannot fly at a high AoA at all due to yaw control as wing blocks aileron effectiveness. Also why flying wings are subsonic.

    I did provide valid data, i'm sorry if you don't understand the rationale. There is nothing special about the Rafale's control surfaces. Every aircraft will suffer decreased pitch and yaw if flow is disrupted. Instead of yelling in caps, show me how the tail provides lateral stability when blocked, I provided enough visually and in actual reports that single tails suffer decreased yaw control at high AoA. As for why the Rafale was tested at an AoA three times the FCS limit, I explained that too. Look back, a clean airframe can recover from that type of departure. Once loaded (especially with an asymmetric load) it would be dangerous to risk departure in combat. The FCS is about carefree handling so the pilot does not have to worry about exceeding the departure limits at a variety of weights and with various stores.

    Prove me wrong or stop whining because you feel I'm attacking your beloved Rafale. I'm actually not, the layout has advantages.... and disadvantages just like every other control configuration.. Shocking I know.
    Last edited by FBW; 22nd March 2017 at 20:58.

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    Quote Originally Posted by TooCool_12f View Post
    That's what several of us have been saying all the time: they had their reasons, but up to now, nobody could bring solid information bout these reasons..
    It is hard to fathom what these reasons could be other than higher aoa's would compromise safety.

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    Quote Originally Posted by Yama View Post
    I don't understand what this discussion is about anymore (if I ever did). Surely it is obvious to any common sense person that AoA limitations are not put there just for the heck of it? In some cases there might be a 'soft limit' which can be exceeded if a situation demands but even that has a rationale behind it.
    Yes, that is essentially their argument.

    Because nobody can definitively prove that the Rafale's AoA limit is there for a reason, as is the case for every other fighter, it must just be a totally arbitrary limit.

    The same logic would mean that the Rafale can fly faster than its top speed, carry more than its max load, etc etc, because maybe those are all just totally arbitrary limits that are imposed for no real reason.

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    Quote Originally Posted by halloweene View Post
    Early days but is the expectation that all aircraft will be upgraded to F4 or just new build? Given engine modifications it could become a somewhat costly exercise to bring all up to F4 standard.

    It talks about missiles, is this a MICA replacement or better meteor suppprt and perhaps additional third nation missile requirements?

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    The point is that tommorrow B-TX - a trainer - would probably have a wider flight maneuvering envelope than a today Rafale. EoA

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    Quote Originally Posted by Ozair View Post
    Early days but is the expectation that all aircraft will be upgraded to F4 or just new build? Given engine modifications it could become a somewhat costly exercise to bring all up to F4 standard.

    It talks about missiles, is this a MICA replacement or better meteor suppprt and perhaps additional third nation missile requirements?
    Missiles : highly probably mica ng. Work on mica ng already financed a year or two ago.

    As it is F4 standard and not MLU, block will be retrofittable. Which do not mean every airplane engines will be changed (think like AESA) but new ones would be fitted with. Older engines would be replaced little by little... And air intakes would not allow more than 8.2/8.3 T thrust afaik.

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    Quote Originally Posted by TomcatViP View Post
    The point is that tommorrow B-TX - a trainer - would probably have a wider flight maneuvering envelope than a today Rafale. EoA
    Blah blah.........

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    No, it's true. Open you eyes.

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    no, not tomorrow, perhaps the day when mach 2 supercruise is to be expected,
    but that day is not tomorrow
    the missile will require about five times the G capability of the target to complete a successful intercept.
    -Robert L Shaw

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    Quote Originally Posted by FBW View Post
    Too cool, I repeat. I have given u the explanation, then I gave links in case some still doubted why. The B-2 example proves my point. Flying wings use split ailerons in some cases. And no, they cannot fly at a high AoA at all due to yaw control as wing blocks aileron effectiveness. Also why flying wings are subsonic.

    I did provide valid data, i'm sorry if you don't understand the rationale. There is nothing special about the Rafale's control surfaces. Every aircraft will suffer decreased pitch and yaw if flow is disrupted. Instead of yelling in caps, show me how the tail provides lateral stability when blocked, I provided enough visually and in actual reports that single tails suffer decreased yaw control at high AoA. As for why the Rafale was tested at an AoA three times the FCS limit, I explained that too. Look back, a clean airframe can recover from that type of departure. Once loaded (especially with an asymmetric load) it would be dangerous to risk departure in combat. The FCS is about carefree handling so the pilot does not have to worry about exceeding the departure limits at a variety of weights and with various stores.

    Prove me wrong or stop whining because you feel I'm attacking your beloved Rafale. I'm actually not, the layout has advantages.... and disadvantages just like every other control configuration.. Shocking I know.
    there's no blinder man than the one that doesn't want to see... I never stated the vertical tail provided control at high AoA, I said the only thing that can be said: the airflow around the aircraft is managed by the canards. What exactly they manage to achieve and how efficiently is what Dassault know but nobody around here does (or can't speak).. you might not like it, but still, you posted data from 40 years ago (basically, 20 years before the Rafale C flew for the first time). You posted data about the F-16, We also had data about the Gripen.. about the Typhoon.. they all had limitations, but none is identical to each other, nor to the Rafale as well. Not that the Rafale flies on pixiedust, but they are all different, have different characteristics and different ways to manage them. You are the one wanting to draw conclusions based on data that are irrelevant for the type. I simply say: if you don't have relevant data, your reasoning can be considered, at best, as a speculation, not as a proven fact.

    And again, I don't say "they put that restriction there for fun".. never had. I said there may be different reasons, for example they may have concluded that going beyond 30° increases drag way too much without bringing any significant advantage in terms of maneuvering, thus, is undesirable in combat (as you probably know, in post-stall regime, the airframe, while still managing to remain airborne, acts mostly as a giant airbrake: generating lots of drag for little lift). Again, I don't say (to the difference of you) "I know that it is the reason", it is a speculation, just like what you say... You say the aircraft may depart.. maybe, but on the other hand, in flight test they had difficulties to make it depart into a spin.. even when doing everything they could to spin it, it just wouldn't spin, and when they finally managed to spin it, by disconnecting a good part of controls, simply releasing the stick with control surfaces in neutral was sufficient to recover, the aircraft stabilized itself.

  15. #2865
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    Quote Originally Posted by FBW View Post
    I provided you with everything you need to understand the topic. There is no magic, no unknown in flight control. You are the one that needs to provide counter evidence that the Rafale has a magical control of yaw when the vertical stab is blocked in high AoA, it is exactly that simple. If you can't, (which you cant't) then you'll get why the F-16, Rafale, and Gripen are AoA limited to around 30 degrees operationally. Testing is a different matter as they have sufficient margin of recovery.

    Please, if you are so confident, show me a study where a single vertical tail ( without tvc) can operate at very high alpha, with full control. I've provided you with articles in this and the Gripen thread that show they can't, period.
    Hmm, seems you are are right -- although as you probably know the Typhoon managed by only minor tweaks to improve the AOA limit from a mediocre 25 degrees and up to 36 degrees, which seems pretty decent to me. Still far away from the AOAs reached by the Hornet, but at the same time I also wonder about the huge advantages about going above, say, 35 degrees. Even if the Hornet pilot remains in control, will he not lose an enormous amounts of energy going to very high AOA, becoming a sitting duck?

    Having too small max AOA limit is not good however AFAIK the Typhoon customers have so far not bothered to implement the significantly higher AOA limit in spite of the relatively low cost; perhaps other things are at the end of the day considered more important (e.g. upgrades to sensors and avionics suite)? Presumably with a good SA the Rafale/Typhoon pilot will never end up in a position that forces him to drop below corner speed and go to high AOA in the first place... (for Gripen there are no AOA limits above corner speed, but rather g limits, I assume the same holds also for Rafale and Typhoon?)

  16. #2866
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    Quote Originally Posted by TomcatViP View Post
    The point is that tommorrow B-TX - a trainer - would probably have a wider flight maneuvering envelope than a today Rafale. EoA
    Boeing TX has straight wing and canted twin tail, it is basically a shrunken Hornet. I think Boeing did a terrible job if it doesn't have AoA limits far higher than Rafale.
    Of course, that configuration is not that great for transonic drag, acceleration and so on...
    Last edited by Yama; 23rd March 2017 at 08:46.

  17. #2867
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    Quote Originally Posted by TooCool_12f View Post
    there's no blinder man than the one that doesn't want to see... I never stated the vertical tail provided control at high AoA, I said the only thing that can be said: the airflow around the aircraft is managed by the canards. What exactly they manage to achieve and how efficiently is what Dassault know but nobody around here does (or can't speak).. you might not like it, but still, you posted data from 40 years ago (basically, 20 years before the Rafale C flew for the first time).
    Look, I get what you are trying to say. And I'm probably as sick of this conversation as most of the posters trying to read through the Rafale thread and having to wade through this. For the final time, yes the canards manage airflow (that is the point of close coupled (control) canards), they energize airflow over the wings and provide some pitch control just like any foreplane. They are an advantage, the vortex generation over the wings prevents stall over a wide range of alpha. Every aircraft begins to lose control surface effectiveness as AoA increases, it can be gradual, or in some cases abrupt. The vertical stab has a purpose, the Rafale uses it same as any aircraft. In fact, a simple look at the Rafale shows that the tail is relatively high for two reasons: provide control at high AoA and stability at high speed.
    Click image for larger version. 

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    T-ViP brought up the T-X design. The requirement is for a 25.5 degree AoA limit i believe, but it is a trainer so the handling has to be relatively benign. Notice a similarity between the T-100 and the Rafale?
    Click image for larger version. 

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    And again, I don't say "they put that restriction there for fun".. never had. I said there may be different reasons, for example they may have concluded that going beyond 30° increases drag way too much without bringing any significant advantage in terms of maneuvering, thus, is undesirable in combat (as you probably know, in post-stall regime, the airframe, while still managing to remain airborne, acts mostly as a giant airbrake: generating lots of drag for little lift). Again, I don't say (to the difference of you) ".
    I'm not going to debate the pros and cons of maneuver in the post stall regime. A 29* AoA limit in air to air and a 20 degree limit in ST1 & ST2 is a result of Dassault designing the DFCS to allow carefree handling. If 35+ AoA was controllable at all weights and loads, you can be assured the limit would be higher.
    Last edited by FBW; 23rd March 2017 at 12:31.

  18. #2868
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    Quote Originally Posted by FBW View Post
    I'm not going to debate the pros and cons of maneuver in the post stall regime. A 29* AoA limit in air to air and a 20 degree limit in ST1 & ST2 is a result of Dassault designing the DFCS to allow carefree handling. If 35+ AoA was controllable at all weights and loads, you can be assured the limit would be higher.
    True, OTOH as the Typhoon example shows, when Typhoon was designed they did not put that much emphasis on the AOA limit; the indication for this is that by only minor tweaking they could increase the AOA significantly; had they considered high AOA to be important during the design phase one would think they would have done more research into this at that time*.

    Who knows; perhaps Rafale could also get a higher AOA with some minor tweaking. This may not happen of course since at the outset Rafale has higher AOA than what Typhoon has, thus it may not be viewed as too much of a disadvantage compared to the competition -- unless of course the 36 degree AOA on Typhoon spurs Dassault to do something similar (assuming the Rafale is up to it of course).


    *One of the former Typhoon test pilots stated in a forum post that his "gut feeling" was that the AOA could have been set higher than 25 degrees...:

    It's an interesting philosophical test dilemma. I flew the first carefree trials in Typhoon with an AOA limiter set higher than the current service limit, but subsequent modelling (not related to the flight test results) made the clearance empire reduce the limits for general testing, and that inevitably ended up in initial service. Notwithstanding that, the jet was absolutely solid at the peak AOAs, no matter what I did to it and I remain certain that there's still more usable lift (at much higher drag) at and beyond the AOAs I saw. No, I don't have the numbers to prove it (Catch 22 again) but I do have judgement and feel - which is why you use human pilots for this, instead of an autopilot.

    Basck to the subject matter of displays. I also flew some displays in the jet, both with the earlier (higher) AOA limit and the subsequent service limit. The fundamental difference was that with the higher AOA I had some extra drag to play with, which made a big difference in speed control - I had something to help balance out the stunning thrust. In contrast, at the service AOA levels I could fly much of the display at full back stick but still had to sometimes play with the throttles to keep speed under control. (As Tarnished says, you don't have a problem getting speed back in these jets , but you can have a problem getting rid of it!)
    http://www.pprune.org/flight-testing...efree-fcs.html

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    Quote Originally Posted by Loke View Post
    True, OTOH as the Typhoon example shows, when Typhoon was designed they did not put that much emphasis on the AOA limit; the indication for this is that by only minor tweaking they could increase the AOA significantly; had they considered high AOA to be important during the design phase one would think they would have done more research into this at that time*.

    Who knows; perhaps Rafale could also get a higher AOA with some minor tweaking. This may not happen of course since at the outset Rafale has higher AOA than what Typhoon has, thus it may not be viewed as too much of a disadvantage compared to the competition -- unless of course the 36 degree AOA on Typhoon spurs Dassault to do something similar (assuming the Rafale is up to it of course).


    *One of the former Typhoon test pilots stated in a forum post that his "gut feeling" was that the AOA could have been set higher than 25 degrees...:



    http://www.pprune.org/flight-testing...efree-fcs.html
    That is an interesting account that reinforces a couple of interesting points... first that the Typhoon has some additional potential with fairly minor tweaks... and second that an AoA limiter is absolutely not about somehow forcing pilots to fly fast. (also provides an interesting contrast to the F-35 pilot's write-up where he talks about the value of being able to brake quickly)

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    Quote Originally Posted by hopsalot View Post
    That is an interesting account that reinforces a couple of interesting points... first that the Typhoon has some additional potential with fairly minor tweaks... and second that an AoA limiter is absolutely not about somehow forcing pilots to fly fast. (also provides an interesting contrast to the F-35 pilot's write-up where he talks about the value of being able to brake quickly)
    Indeed. At a time a specific FCS with relaxed rules was considered for Rafale demos. The idea was abandoned for several reasons (cost, accuracy of the show to operational version)

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    Quote Originally Posted by halloweene View Post
    Indeed. At a time a specific FCS with relaxed rules was considered for Rafale demos. The idea was abandoned for several reasons (cost, accuracy of the show to operational version)
    Right, because such a tweaked version couldn't be used on an operationally configured (loaded) aircraft because of the risks described in other posts in this and the Gripen thread.

    I am sure an airshow configured Rafale could safely venture into areas that a combat loaded Rafale couldn't because it wouldn't have to worry about the possibility of an asymmetric load, nor even the full altitude/speed envelope. (given that airshows happen fairly low and slow)

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    Quote Originally Posted by hopsalot View Post
    That is an interesting account that reinforces a couple of interesting points... first that the Typhoon has some additional potential with fairly minor tweaks... and second that an AoA limiter is absolutely not about somehow forcing pilots to fly fast. (also provides an interesting contrast to the F-35 pilot's write-up where he talks about the value of being able to brake quickly)
    here is what he said:
    "Notwithstanding that, the jet was absolutely solid at the peak AOAs, no matter what I did to it and I remain certain that there's still more usable lift (at much higher drag) at and beyond the AOAs I saw."

    in other words, the limiter could have been set higher, but wasnt....
    the missile will require about five times the G capability of the target to complete a successful intercept.
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    Quote Originally Posted by Loke View Post
    I think these are some very valid points -- apart from training exercises (which we in most cases don't know the details of and therefore hard to properly assess) we have other sources, e.g. the Swiss leaks that clearly showed that in both the 2008 version but even more so the 2015 version of Rafale is much more capable than the F-18, also in a2a (as you would expect). High AOA limit no doubt is "nice to have" but I do have the impression there are many other factors that are much more important for the outcome, in particular sensors, sensor fusion, MMI, networking, etc. With good SA the Rafale will never be "surprised" by a Hornet suddenly showing up in WVR in an akward position thereby trigger the need for a high AOA manouver at exactly that point. The current Rafale does not even have HMD still it is doing quite well in a2a it seems.
    Sorry for the late reply, I was short on time.

    I have actually found the video where the pilot ("Easty") involved in the BFM explains the exercise details at 3:30.



    The pilot basically just confirmed the stuff I was talking about.
    It is interesting to note that the attacker in the last setup became defender because he wasted the opportunity to score ("tight window" I was talking about) and was so low on energy that he lost the fight.

    Of course, SA is the most important aspect of the aerial fight (BVR and WVR), but that was not specific subject of the discussion.

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    Quote Originally Posted by obligatory View Post
    here is what he said:
    "Notwithstanding that, the jet was absolutely solid at the peak AOAs, no matter what I did to it and I remain certain that there's still more usable lift (at much higher drag) at and beyond the AOAs I saw."

    in other words, the limiter could have been set higher, but wasnt....
    Yes, that is what he said. The program as a whole decided differently.

    He may be right, but then again he may not.

    Even if he is "right" in that the limiter might have been set higher, how much higher are we talking about? 2-3 degrees? That would bring it close to the Rafale...

    Even with the aerodynamic modification kit the Typhoon still only gets into the low-mid thirties for AoA so we aren't talking about competitive with the Hornet/Super Hornet, F-35, F-22, or various Sukhois.

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    France launches F4-standard Rafale development

    https://www.flightglobal.com/news/ar...opment-435500/

    Now in English

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    France launches F4-standard Rafale development

    https://www.flightglobal.com/news/ar...opment-435500/

    Now in English

    Although this was certain (Except for VivS) a new standard and a new tranch are always quite a milestone for a program worth celebrating.

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    Has Dassault provided any data on cost reduction due to export contracts? In the last few years a total of 84 have been sold to 3 different countries. This represents an increase of 37.3% against the 225 acquired by France.
    History and Military Technology blog

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    Quote Originally Posted by hopsalot View Post
    Yes, that is what he said. The program as a whole decided differently.

    He may be right, but then again he may not.

    Even if he is "right" in that the limiter might have been set higher, how much higher are we talking about? 2-3 degrees? That would bring it close to the Rafale...

    Even with the aerodynamic modification kit the Typhoon still only gets into the low-mid thirties for AoA so we aren't talking about competitive with the Hornet/Super Hornet, F-35, F-22, or various Sukhois.
    I'd like to insist on one point. Main uses of high AoA are turning ability and slow manoeuvrability. About slow manoeuvrability, it is interesting to check landing speed. 155/135 kts for F35 A/B afaik and Rafale 115 kts. Says some.

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    Quote Originally Posted by halloweene View Post
    I'd like to insist on one point. Main uses of high AoA are turning ability and slow manoeuvrability. About slow manoeuvrability, it is interesting to check landing speed. 155/135 kts for F35 A/B afaik and Rafale 115 kts. Says some.
    Hallow, don't go all former AvWeek editor over this. Not everything needs to be framed in an F-35 v. Rafale context. I'd be suprised if anyone would question Rafale's lower landing speed, they designed it to have favorable landing characteristics for carrier ops (Some specific changes to M withstanding). The F-35C is considerably different.

    Chalk this up to residual annoyance from time spent in the viper den.

  30. #2880
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    Quote Originally Posted by a89 View Post
    Has Dassault provided any data on cost reduction due to export contracts? In the last few years a total of 84 have been sold to 3 different countries. This represents an increase of 37.3% against the 225 acquired by France.
    Dassault had an agreement that the gouvernement financed a big part of development, but Dassault also had to invest. In return, Dassault would recocer its incestments theough exports. As a result, the exported aircraft are considered separately and don't necessarily influence the price for those aimed at the french air force.

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