Dismiss Notice
Welcome to IDF- Indian Defence Forum , register for free to join this friendly community of defence enthusiastic from around the world. Make your opinion heard and appreciated.

Close coupled vs long arm canard

Discussion in 'The Americas' started by Picard, Aug 23, 2014.

Thread Status:
Not open for further replies.
  1. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    Canards overview and general effects

    Canard is a small control surface placed in front of the main wing, similar to how tail is behind it. There are two main variations - long arm and close coupled canard.

    Canard has a major advantage over the horizontal tail in the level flight. As aircraft passes through the transonic region, aircraft experiences an increased nose-down trim change. Control surface has to counter it; and while horizontal tail provides download, causing a large trim-drag penalty, canard can help provide upload, reducing need for elevon/tail trim and thus reducing level-flight drag. Further, canard also allows for an aerodynamically clean end of the aircraft with superior area distribution when compared to the tailed configuration, reducing supersonic drag.

    Canard provides lift when aicraft is turning regardless of configuration and (in)stability level. While stable canard-wing configuration results in canard causing major vortex drag in level flight due to lift generated by the canard (a pair of tip vortices appear due to differences in pressure between upper and lower surface), if aircraft is statically unstable canard can be unloaded, thus avoiding vortex drag in cruise flight; as a result, tailless canard configurations (either close coupled or long arm) tend to have excellent supersonic performance, since there is no interference drag which appears with tailed configurations. In fact, canard is unloaded in all three Eurocanards (Gripen, Rafale, Typhoon), resulting in a lift-to-drag ratios in level flight comparable to tailless deltas, and lift-to-drag ratios in maneuvre better than that of tailless deltas. In either case, their L/D ratios are better than those of tailed configurations.
     
    samsonight likes this.
  2. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    Close-coupled canard

    Wing wake and its downwash diminish horizontal tail's control effectiveness. However, canard is located in wing's upwash, meaning that its influence is magnified, which results in the center of the lift being moved forward more than canard size would suggest. This destabilizing effect has in past meant that a very forward Cg position was required, but has proven beneficial with advent of unstable fly-by-wire aircraft.

    Since aircraft with close-coupled canard are dynamically unstable, they typically show better pitch rate through the angle of attack range than non-canard aircraft of the same configuration. Additionally, large momentary enhancement in lift is observed when canard pitches up rapidly to high angle of attack (this assumes that canards are used for pitch control), thus improving pitch onset/turn onset rate.

    Canard's own downwash can impede lift generation of the parent wing at low angles of attack, but this effect can be countered by proper horizontal and vertical positioning of the foreplane. This is to say that canard has to be high in relation to the wing, as can be seen in Saab's Viggen and Dassault's Rafale. Additional consideration is wing sweep angle, with 45* being ideal as at that sweep angle canard has relatively little influence on the lift generation. At higher angles of attack, downwash can suppress the flow separation on the wing, thus improving lift and reducing drag.


    Aircraft with close-coupled canard does not have to have as large amount of statical instability as one with long-arm canard or tail, since close-coupled canard naturally creates an area of low pressure on forward part of the wing. This results in center of lift being moved forward, increasing aircraft's instability to levels beyond what would be expected by taking lift from the wing on its own.

    Both canard and wing producing two sets of vortices - one from tip and another from root. In close coupled-configuration, canard tip, canard root and wing root vortices all help increase lift at high angles of attack. Mutual influence of canard and parent wing means that free-roling vortices are stabilized and vortex bursting is delayed, especially at high angles of attack; an additional vortex may be formed on the wing where canard downwash suddenly decreases effective angle of attack. Wing vortex also moves canard wortex inward. As a result, wing's trailling-edge control surfaces remain effective at far higher angles of attack than in a long-arm or tailless delta configuration, as vortices allow air flow to remain attached for longer and vortex bursting point reaches wing trailling edge at a higher angle of attack than it would without presence of a canard (vortex breakdown is delayed for both wing and canard vortices, increasing effectiveness of both surfaces at high angles of attack). Necessary wing twist is also reduced, as outboard vortices help prevent the wing tip stall, while inboard vortices increase body lift in addition to improving wing lift. Effects of outboard vortices on wing tip also result in improved roll rate and roll response, especially at high angles of attack.

    This also results in improvement in the maximum lift, which can be as much as 20-30% greater than what is achieved by surfaces in isolation, as well as improved lift for most, if not all, angles of attack (all close-coupled canard configurations discussed in various documents I have read experience lift increase at AoA above 20 degrees, and many experience lift increase at AoA as low as 10 degrees, albeit at low AoA lift enhancement is so minor so as to be insiginificant. At 20 degrees AoA, lift increase in one case was 34% compared to the sum of lift produced by wing and canard on their own. Angle of attack for maximum lift is also increased). Enhancement is largest for canard above and just in front of the wing, and wing camber and twist have no effect on the lift increase; lift improvement is maximized when canard area is 25% of the wing area, and best relation between lift and L/D ratio was achieved in 45*-swept canard. Canard trailling edge and wing leading edge should be as close as possible, but should never overlap else a loss of lift occurs. Beyond Mach 0,9 however, close-coupled canard has little effect on lift.

    As a result, aircraft with close-coupled canard configuration tend to have better air field characteristics and maneuvering performance than they would if canard was removed. A series of tests with F-4 that had canard mounted on the upper forward portion of the air inlets revealed that addition of canard would allow the aircraft to pull a full g more at 470 kph and 9.000 m, and would also lower the approach speed by 14 kph. Israeli Kfir, a modification of Mirage 2000, used close coupled canards to improve airfield performance, as did Saab Viggen. Thanks to favorable canard-wing vortex interactions, Viggen achieved 65% greater lift coefficient at approach than a pure delta wing, reducing takeoff and landing speeds for STOL capability. Use of close coupled canard gave Viggen much greater trim control, and allowed it to use elevons to enhance lift at takeoff, where tailless delta's elevons would subtract from lift.


    Aside from increase in lift, close-coupled canards help reduce drag in maneuvers at all angles of attack but lowest (10* AoA or less) ones, and reduce drag for the same turn rate compared to the canard-off configuration. There are three primary causes for this. First, since increase in lift is apparent even at low angles of attack, close-coupled canard configuration needs lower angle of attack for the same wing size, or less wing size for the same angle of attack, to achieve same lift-to-weight ratio; this results in the same turn rate being achieved with less drag penalty. Second, close-coupled canard supresses flow separation. Flow separation (stall) is a major source of drag, and in delta wing configurations without close coupled canard, first stall can happen at angles of attack well below those required for maximum lift. Third, close-coupled canard configuration requires less control surface deflection (trim) to maintain same angle of attack, thus reducing trim drag.

    All these factors combine to reduce drag for given lift. In fact, lift/drag ratio for close-coupled canard configuration can be 10% greater than for canard-off configuration.


    Additional factor is the design influence. Strongest wing vortices are produced by sharp-edge, highly-swept planforms which have low L/Dmax and thus poor range and endurance, and high approach speed. Thus a selection of a more adequate planform requires an additional mechanism to produce and/or energize vortices.


    Canard is set at neutral AoA during subsonic cruise, producing no lift and causing minor drag penalty. Position of canard ahead of wing also helps move center of pressure forward relative to the center of mass, creating a naturally unstable configuration.

    At supersonic speeds, close coupled canard configurations experience less center of lift shift, reducing induced and trimmed drag compared to tailless delta and long-arm canard aircraft. This is partly offset by comparably minor drag from the canard itself. There is little effect on lift or drag during supersonic maneuvers, and close coupled canard combined with ventral intake actually increases supersonic drag. At transonic speeds, benefits are same as on subsonic speeds.


    Close coupled canard also delays buffet onset and reduces buffet intensity. Additional benefit is controllability at post-stall angles of attack, which is important mostly for safety considerations - close-coupled canard configurations remain controllable at angles of attack up to 100-110*, with no risk of getting trapped in superstall. Further, if FCS is properly developed, close-coupled canard can help dampen roll and yaw oscillations, thus guarding against the wing roll and sideslip; but if FCS is not properly developed, these problems can be magnified. Close coupled canard configurations also have acceptable spin behavior. In emergency, canards can be feathered, rendering aircraft stable or neutral.


    While high canard (canard is above the wing) has been discussed here, most of these effects are true for coplanar canard as well, albeit coplanar canard is significantly less effective, and does not increase aircraft's instability level beyond effect of the canard itself (which, for control canard, is zero at subsonic speeds). Low canard, on the other hand, creates low pressure area at wing's lower surface, causing pitch down moment. Additionally, low canard prevents formation of wing leading edge vortices; both these effects reduce lift compared to the wing alone, coplanar or high canard configuration. Another possibility is an oscillating canard, which would significantly enhance wing pitch response.
     
    samsonight and Gessler like this.
  3. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    Long-arm canard

    Vortex from long-arm canard bursts early due to lack of influence from the parent wing, meaning that long-arm canard has no influence on improving lift beyond increase in wing size it provides. This means that it does not reduce drag at high angles of attack as close-coupled canard does, and consequently long-arm canard configuration has higher drag than even standard tailless delta. Zero lift drag is also more likely to be increased as long-arm canard is harder to fit into the overall body area distribution; if done well, however, zero-lift drag of long-arm canard is less than that of close-coupled canard, and cruise drag is also less at subsonic, and possibly supersonic, speeds.

    However, total instability of aircraft using the long arm canard has to be greater than that of using close-coupled canard for these benefits to be fully realized, since rate of neutral point shift with Mach number is greater than that of close-coupled canard configuration; such difference is not achievable currently as FCS cannot cope with it. Long arm canard will remain inferior in the area of the maneuvering combat regardless of the instability level, making it a better choice for bomber interceptors, supersonic bombers and civilian aircraft than for air superiority fighters. That being said, it is still superior to conventional tailed planforms as it produces immediate response in desired direction.


    Long-arm lifting canard was used in Mirage "Milan" variant to improve aircraft airfield performance. As foreplanes added lift ahead of aircraft center of mass, they required downward elevons to trim. As a result, lift was added both ahead and rear of center of gravity, reducing takeoff distance and improving maneuverability.

    Lifting canard is not used on any of Eurocanards as it has severe security issues - if wing stalls first, then aircraft will likely enter an unrecoverable deep stall. Another factor is that it causes major drag penalty in the level flight. X-31 used control canard in conjuction to thrust vectoring in order to achieve post-stall maneuverability, but that canard required large deflections (+20/-70 deg) in order to be effective, while close-coupled canard requires less deflection.


    While long arm canard does provide longer moment arm (hence the name) and thus potentially higher pitch rate, this benefit is somewhat negated by the fact that close coupled canard can be positioned to produce a low pressure zone at front of the wing which has similar effect. Long arm canard does provide improvement in takeoff rotation, especially compared to the horizontal tail.

    In terms of high-AoA performance, long-arm canard configurations allow a good pitch-down capability, but are controllable over a narrower AoA range than close-coupled canards, up to some 70*. They are also prone to transonic pitch-up issues, and do not provide notable improvement in spin recovery characteristics.


    Conclusion

    Overall, at speeds above Mach 1 and high lift coefficients canard position has little influence on performance. At low lift coefficients, close-coupled canard may reduce drag somewhat, through overall drag is more dependant on other design choices (wing sweep and thickness, area ruling etc). Close coupled canard does have a major advantage over the long-arm canard when it comes to maneuvering combat at subsonic speeds, increasing transient maneuverability (turn onset, roll onset), instantaneous and sustained turn rate, as well as reducing drag. It also has superior high AoA characteristics as well as post-stall and spin recovery capability; though these can be somewhat limited by physical limitations of control surfaces (canards themselves, elevons or horizontal tail). It also reduces drag at supersonic speeds.

    Eurofighter design team decided on a long-arm canard since close-coupled canard combined with Typhoon's air intake position resulted in configuration having unacceptable amount of cruise drag; Gripen and Rafale avoided that problem through competent air intake positioning. Air intake, and consequently canard, position was a consequence of Typhoon being designed for usage of thrust vectoring, and indeed using TVC was shown to reduce trim drag at supersonic speeds. However, while thrust vectoring is a useful addition for designs which show less than adequade aerodynamic performance (Eurofighter Typhoon, F-22, F-15, F-16), prohibitive cost, weight and reliability/maintenance penalties mean that it is not an option for frontline fighter aircraft. Long arm canard has far less influence on maximum lift than close-coupled canard, and does not improve roll performance, or spin recovery characteristics. High AoA recovery characteristics are limited by canard deflection angle. While it does improve pitch performance, that characteristic is shared with the close-coupled canard.


    Overall, MAC instability is (according to the data I found) 45,61% for Rafale, 37% for Typhoon and 25% for Gripen, which means that Rafale likely has the highest pitch rate of three. As static instability forms a greater percentage of total instability level for Typhoon than it is for Gripen or Rafale, Typhoon's supersonic maneuvering performance is likely inferior to Rafale's, though difference probably isn't large.

    Both canard types provide better damage tolerance through overlapping control surfaces,


    As a result, close coupled canard is a superior choice for air superiority fighters, which have to be able to maneuver at high angles of attck at subsonic speeds, as well as to cruise and maneuver at subsonic speeds. It can also be useful for a low-level strike aircraft. Long arm canard is only a good choice for aircraft which expect to spend large percentage of time at supersonic speeds (or cruise conditions in general) and do not expect to enter a protracted turning engagement at subsonic speeds, such as bomber interceptors and supersonic transport/passenger aircraft.
     
    samsonight, Gessler and layman like this.
  4. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    Further reading

    Effect of Canard Vertical Location, Size, and Deflection on Canard-Wing Interference at Subsonic Speeds Blair B. Gloss, Edward J. Ray, and Karen E. Washburn

    LIFT ENHANCEMENT USING CLOSE-COUPLED CANARD/WING VORTEX INTERACTION by John M. Kersh, Jr.

    AERODYNAMIC CHARACTERISTICS OF THE CLOSE-COUPLED CANARDS AS APPLIED TO LOW-TO-MODERATE SWEPT WINGS VOLUME 3: TRANSONIC-SUPERSONIC SPEED REGIME by David W. Laosy

    EFFECT OF WING PLANFORM AND CANARD LOCATION AND GEOMETRY ON THE LONGITUDINAL AERODYNAMIC CHARACTERISTICS OF A CLOSE-COUPLED CANARD WING MODEL AT SUBSONIC SPEEDS - Blair B. Gloss, Langley Research Center,Hampton, Va. 23665

    DESIGN FOR AIR COMBAT by Ray Whitford

    FLOWFIELD STUDY OF A CLOSE-COUPLED CANARD CONFIGURATION by John F. O'Leary

    CANARD-WING INTERACTIONS IN SUBSONIC FLOW - S. SAMIMI1, A. R. DAVARI AND M. R. SOLTANI

    Numerical Study of Steady and Unsteady Canard-Wing-Body Aerodynamics - Eugene L. Tu

    MACH Aviation Magazine - på webben
     
  5. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
  6. BMD

    BMD Colonel ELITE MEMBER

    Joined:
    Nov 20, 2012
    Messages:
    10,798
    Likes Received:
    3,012
    Country Flag:
    United Kingdom
    Further Reading:
    http://ftp.rta.nato.int/public//PubFulltext/RTO/MP/RTO-MP-035///MP-035-01.pdf

    A low forward foreplane position then results in
    the smallest foreplane area, with a consequent benefit on
    drag.

    Further, at the level of instability chosen for the aircraft,
    there was little effect on maximum lift of either position,
    whilst for a less unstable aircraft. a high aft foreplane
    does provide some benefit on lift. Further, the low
    forward foreplane is more effective as a control surface,
    with consequent benefit for nosewheel lift, trim and
    manoeuvre capability. This increase in effectiveness is
    maintained, even at high angle of attack.
     
  7. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    Only in level flight, and for that particular configuration (I have already explained reason why - ventral inlet's interference with canard air flow, a problem that does not exist with either Gripen's or Rafale's configuration).

    See here:
    Coming together - 6/16/1999 - Flight Global
    "As a foreplane located close to the wing produced too much supersonic drag when combined with a chin inlet, designers selected a long-coupled delta/canard configuration."

    http://www.icas.org/ICAS_ARCHIVE/ICAS1998/PAPERS/04.PDF
    "A major impact on foreplane location and foreplane wing coupling is the place of the air intake."

    Ventral intakes = long arm canard:
    http://upload.wikimedia.org/wikipedia/commons/6/64/RSAF_Typhoon_at_Malta_-_Gordon_Zammit.jpg
    http://upload.wikimedia.org/wikipedia/commons/4/40/North_American_XB-70_above_runway_ECN-792.jpg

    Side intakes = close-coupled canard:
    http://www.wallpapersweb.com/data/media/51/Saab Viggen 1.jpg
    http://img4.wikia.nocookie.net/__cb...46/Air_jas-39_gripen_top_smokewinders_lg1.jpg
    http://upload.wikimedia.org/wikipedia/commons/7/7d/F-4_shoulder_canards.jpg
    http://i.imgur.com/3eIJC77.jpg
    http://magazine.flyart.biz/aviation/art/aim-high/02c.jpg

    And Typhoon was to have close coupled canard before problems with intake positioning were discovered:
    http://i146.photobucket.com/albums/r279/sampaix/198520EFAa.jpg

    Canards by themselves cause only a minor drag penalty, it is how they interact with chosen aerodynamic configuration that really matters.

    With minor advantage for the close-coupled configuration. But you have obviously failed to check the reason for that lack of effect on lift, reason that is unique for Typhoon and does not apply to either Gripen or Rafale. Namely, inlet positioning resulted in pressure zone that was destroying lift, thus negating any lift benefit of close-coupled configuration. It also increased drag in level flight.

    And since main advantage of close coupled configuration is in transient performance, close-coupled canard might still be somewhat beneficial to Typhoon, but not with its design goals.

    It is still not as effective as close coupled canard:
    [​IMG]

    X-31 (and Typhoon) loose pitch authority at cca 70*, Rafale and Gripen can pass 100* without problem.

    --------------------

    BTW, these are maximum roll rates:
    Rafale: 290*/s
    Gripen: 240*/s
    Typhoon: 200*/s

    Sustained turn rates:
    Rafale: 28,1*/s
    Typhoon: 28*/s

    Proves my arguments quite well.
     
    Last edited: Sep 2, 2014
    samsonight likes this.
  8. BMD

    BMD Colonel ELITE MEMBER

    Joined:
    Nov 20, 2012
    Messages:
    10,798
    Likes Received:
    3,012
    Country Flag:
    United Kingdom
    It was me who told you that the intake placement was a major factor in canard placement. Multirole fighters need strong fuselage hard points and so the canards have to be CCC to avoid obstruction of the side intakes. This results in bigger canards, lower instability, more drag and a higher RCS. All clearly explained in my link.

    With chin inlets the canard position is entirely at the designer's discretion and LCC is the best balance for air superiority across the range of altitudes and the requirement for both WVR and BVR combat, whereas CCC is better for heavy loads and low altitude lift.

    Why exactly do you believe CCC and chin inlets aren't possible? They are, they just weren't selected for the above reasons. You just can't accept that. Why on Earth would a chin inlet increase drag in level flight? It's painfully obvious to see that the frontal cross section of a Typhoon with chin inlets offers a far smaller drag area. Is an F-16 high drag? One look at the NATOPS manual for the F-16 shows Mach 2.05 is achieved with pitot intakes.

    Oh I also spoke to an Su-37 about your claims of chin inlets interfering with CCC and it found them painfully ridiculous. The MiG-1.44 also chipped in and whilst slightly less CCC, it also found your claims idiotic. The Su-47 also sighed.

    My article was very clear, they carried out a comprehensive study and found CCC produces little extra lift unless you reduce instability or use far bigger canards. Gripen and Rafale both chose the latter in varying amounts.

    Your claims on figures are unofficial (made up) and I've personally observed a Typhoon rolling faster than 200deg/s. Look hard enough at display footage on YouTube and you'll no doubt see it too. Your figures on STRs have both increased by 20% since the last time you fabricated them, so I'll let people make their own judgement on that.

    Pitch control is harder with less stable aircraft, but frankly the benefits of AoAs beyond 70deg are non-existent and it's far better just to take the advantage of increased instability at lower, more applicable AoAs.
     
  9. somedude

    somedude Captain FULL MEMBER

    Joined:
    Sep 1, 2014
    Messages:
    1,499
    Likes Received:
    1,111
    Country Flag:
    Afghanistan
    http://en.wikipedia.org/wiki/Canard_(aeronautics)

    Let's look at supersonic aircraft built after 1950.

    Avro 730: bomber/recon, LCC (canceled)
    North American XB-70 Valkyrie: bomber, LCC (canceled)
    Saab Viggen: fighter, CCC
    Tupolev Tu-144: airliner, LCC (military version canceled)
    Sukhoi T-4: bomber, LCC (canceled)
    IAI Kfir C2 (modified Mirage 5): fighter, CCC
    Chengdu J-9: fighter, CCC (canceled)
    Dassault Mirage III NG (modified Mirage III): fighter, CCC
    Atlas Cheetah (modified Mirage III): fighter, CCC
    Dassault Rafale: fighter, CCC
    IAI Lavi: fighter, CCC (canceled)
    Saab Gripen: fighter, CCC
    Rockwell MBB X-31: fighter, LCC (experimental only)
    VTI Novi Avion: fighter, CCC (canceled)
    Eurofighter Typhooon: fighter, LCC
    Chengdu J-10: fighter, CCC
    Shenyang J-15: fighter, CCC
    Chengdu J-20: fighter, LCC (in development)

    LCC has generally been preferred for larger aircraft (supersonic airliners or bombers), and they have a history of being often canceled or remaining purely experimental. On the other hand, CCC has reigned over smaller fighters, being pioneered by Saab's original designs and on Mirage modifications. The Typhoon and the J-20 are the only ones going against the grain here. Not counting demonstrators, prototypes, or canceled projects, CCC has seen eight different fighter models; while LCC has seen one supersonic airliner mostly famous for tragically crashing at the Paris Air Show and one fighter; with perhaps another in the future depending on how the J-20 development goes.

    It might be argued there are other reasons than aerodynamics for this: canards positioned like on the EFT hinder downward visibility and make it harder to land on an aircraft carrier, whereas the only other LCC fighter, the J-20, still has the canards behind the cockpit. It might also be argued that Rafale and Gripen stayed with CCC because their engineers were already familiar with CCC aerodynamics from their previous designs so it was a safer bet.

    Still it remains that for most existing and proposed canard fighter designs, it's the CCC approach that was chosen.
     
    samsonight and Picard like this.
  10. BMD

    BMD Colonel ELITE MEMBER

    Joined:
    Nov 20, 2012
    Messages:
    10,798
    Likes Received:
    3,012
    Country Flag:
    United Kingdom
    LCC fighters take advantage of larger instability margins, which until the 1990s weren't manageable.

    The visibility one is questionable. It depends where the pilot is looking. The LCCs are always smaller because of the larger pitching lever arm they're on, which means less force is required. In the case of the Gripen and Rafale they're also on side mounted intakes which further obscure view.

    At least 3 of the cancelled projects on your list were experimental Mach 3 bombers (Avro 730, XB-70, Sukhoi T-4). At least two of these were cancelled along with a whole bunch of radical cruise missile designs, included fission-powered ramjets, because ICBMs were invented and hence high speed endo-atmospheric flight was no longer the best delivery option. The Sukhoi T-4 was probably cancelled because ALCMs, namely the Kh-55, were seen as a better option. The Tu-144 bomber was cancelled because well, instability on a bomber isn't that important except perhaps for a range advantage, but again the project was cancelled in the 1970s because the Kh-55 was to make range less important. Although the Tu-144 did have a massive advantage in cruise speed over the Tu-160. Not much can be read into this really. The B-1A was also cancelled. Fast bombers just weren't seen as essential.

    So really no LCC fighters have been cancelled since the X-31 was intended as experimental only. The J-20 is a bigger fighter than the Typhoon with relatively small wings, so the canards can physically be further back. Putting them further forward might also cause issues with the SRAAM launch.:azn:

    I'm not sure a lot of the CCC aircraft on their actually had active canards either. The Viggen and Kfir C2 didn't, so they aren't really in the same league as what we're talking about here. Using instability with fixed canards is obviously impossible.
     
  11. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    You didn't tell me anything I didn't know already.

    And all only relevant for that particular configuration because of the unfavorable interaction between close coupled canard and ventral air intake.

    With chin inlets, yes. But with side inlets close coupled canard is better since it helps not only pitch and turn performance but also roll performance and gust resistance.

    They are entirely possible, but using CCC combined with chin inlets automatically results in several adverse effects, such as increased drag and reduced lift gain.

    Is it that you half read what I write or simply don't want to get it? Chin inlet is not a problem by itself, it is only when it is used in combination with close coupled canard that problems arise. Typhoon designers had two choices - either extend the duct forward of canards, which would prevent the interference but at increased weight, or move canards forward. Third possibility is to move wing leading edge rearwards, but wing was already fixed.

    And I spoke to them and they all think you're blind for missing basic facts. Take a look at relative positions of canards and inlets:
    Su-37:
    http://www.defencetalk.com/pictures/data/3275/Sukhoi Su-37 Terminator performing.jpg
    MiG 1.44:
    http://www.airwar.ru/image/idop/xplane/mfi/mfi-4.jpg
    Su-47:
    Russians Su-47 Berkut aircraft military- Image 1549x1024

    Su-37's canard is well away from air intakes so there is no interference. MiG-1.44 had canards in line with air intakes, not slightly in front like it was the case with original Typhoon's configuration. Su-47 uses same solution as Gripen and Rafale.

    Now compare MiG 1.44:
    http://www.airwar.ru/image/idop/xplane/mfi/mfi-4.jpg
    with BAe EAP:
    https://c1.staticflickr.com/7/6127/5959588541_f7efc44235_z.jpg

    You can see that EAPs canards are just in front of air intakes, while MiG 1.44s are just behind them.

    In other words, none of your examples is representative. J-10 also uses close coupled canard combined with chin inlet, but unlike Typhoon, inlet extends well forward of canards:
    http://www.ausairpower.net/PLA-AF/Chengdu-J-10A-PL-11 PL-8-2S.jpg

    Your article is very clear for that particular configuration. Nothing more, nothing less.

    Give me videos then. As for STR, there was no increase, unless you think that STR is identical at sea level and at 15.000 feet (considering your general knowledge, you may well think that).

    Rafale:
    23,9-26,3 deg/s sustained at sea level
    28,1 deg/s sustained at 15.000 feet

    Typhoon:
    23,4-25,1 deg/s sustained at sea level
    28 deg/s sustained max

    Regarding roll rate:
    Typhoon is the ultimate, says test pilot - 9/9/1998 - Flight Global
    "Eurofighter's roll rate is "-in excess of 200° per second," says Turner"


    Takes about a second for a roll of cca 180*, at 0:30. > ~200*/s


    Around 2-3 seconds for a 360* roll, at 0:05. > ~200*/s

    So yeah, around 200 dps. Maybe slightly above it, but nowhere close to Rafale's 290*/s, and with more sluggish roll onset than either Rafale or Gripen achieve.

    Close coupled canards increase instability beyond aircraft's static instability level, and keep aircraft unstable up to the higher Mach numbers. In other words, Typhoon needed higher degree of instability in order for long arm configuration to work.
     
    samsonight likes this.
  12. BMD

    BMD Colonel ELITE MEMBER

    Joined:
    Nov 20, 2012
    Messages:
    10,798
    Likes Received:
    3,012
    Country Flag:
    United Kingdom
    I find that difficult to believe.

    This interaction you talk of doesn't exist as several other fighters employ CCC with ventral intakes as I've already pointed out.

    But then we're back to the fact that chin inlets perform better at higher AoAs and reduce the fuselage width in any given direction, hence reducing RCS. The only issue is that fuselage pylons are weaker in load-bearing capability. You obviously can't use LCC with side inlets because they block the inlets. It's not a matter that they're better, it's that you don't have a choice with side inlets.

    They'll give the same advantage as with side-inlets, in fact better, because they'll be using the longer, more central part of the wing.

    Rubbish. I've pointed out several aircraft that operated successfully with chin inlets and CCC. MiG-1.44, Su-47, Su-37 and earlier Su-35/Su-27M variants. So British and Russian designers don't know as much as you?

    The Su-37/MiG-1.44 placement is damn near identical to what a CCC Typhoon would have. In fact, in terms of longitudinal placement, a CCC Typhoon intake to canard separation would be almost identical to a Rafale. Damn you're trying so hard to prove something you just can't prove because it's wrong!

    And if the wing-canard separation on Typhoon was the same as Gripen, that's where the intake end would be relative to the canard on Typhoon too give or take a few inches.

    Nope, the study was done when they were considering the overall configuration, at which point they had freedom to put things wherever they wanted. You're also wrong about EAP being CCC, it actually just had LERX between the wing and canards, which is what Typhoon is getting soon.

    Already given you them. No sense repeating the same crap when there's nobody in.

    Well congratulations for proving you're a fool. How on Earth do you expect sustained turn rate to be higher at 15,000ft than sea level. See page A8-54 and A8-57, STR always reduces with altitude, typically by 25% going from SL to 15,000ft. Less dense air, don't you understand anything?:

    https://info.publicintelligence.net/HAF-F16-Supplement.pdf

    In excess of.

    Your figures constantly shift and change and are usually crap. 2 rolls in 3s.



    Yet to see Rafale do a 290deg/s roll. Seen here taking well over 1s for <270deg at 0:10 and 2s for 360deg at 1:00



    You are now failing to grasp what instability actually is. You can't increase it. If you have it you have to counteract it using the canards when turning to prevent the aircraft flipping. Dynamic instability means that oscillations or adjustments in pitch are not under control.
     
  13. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    It is truth.

    It existed in configuration Typhoon used due to incorrect relative positioning of air intakes and canards.

    They only perform better at high AoA if side inlets are not shielded as they are in the F-18 and Rafale, and are also sensitive to the sideslip. As for the RCS, shape has more to do with it than fuselage width, else F-16 would have lower RCS than the F-22.

    J-20 did it. But even many fighters which could use long arm canards (Su-37, J-10) used close-coupled canards instead.

    Nope, as interaction with air intakes will result in lift loss.

    Funny that none of them made it into serial production except for the J-10. And with all of them, canard leading edge was behind air intake (except for Su-37, but even there trailling edge was behind air intake, and canards were not right next to the air intake anyway).

    And Su-47 uses an air intake configuration that is similar to that of Rafale, so you're wrong there:
    http://avioners.net/wp-content/uplo...AAAAAAACFI/X-komlVARMQ/s1600/sukhoi_su_47.jpg

    Bullshit. CCC Typhoon would still have canards that would be in front of air intakes with little to no longitudinal separation, and in very close physical proximity.

    Rafale's canards are actually almost level with air intakes:
    http://upload.wikimedia.org/wikipedia/commons/f/fb/Rafale_RIAT.JPG

    as are MiG-1.44s:
    http://www.airwar.ru/image/idop/xplane/mfi/mfi-4.jpg

    Still doesn't change the fact that results in that study are only relevant for the particular configuration studied.

    EFA was the original tested configuration and it was a close coupled canard:
    http://i.imgur.com/m1a7G.jpg

    EAP increased canard distance from wing but it was still relatively close:
    http://on-target-aviation.com/Assetts/images/EAP CAG.jpg

    Typhoon's canard is far further forward than either EFAs or EAPs:
    http://fc07.deviantart.net/fs71/i/2011/013/5/e/eurofighter_typhoon_ipa5_zj700_by_agnott-d37395i.jpg

    I didn't say either of these figures is correct, in fact 24-26 deg/s at sea level figure is for Rafale A whereas 28 deg/s figure is for Rafale C. But regardless of which set of figures you take, result is clear: Rafale drags less than Typhoon when turning. And if I were like you, I'd simply claim STR of 28 deg/s for Rafale and 24 deg/s for Typhoon.

    In excess of 200 degrees, yes. Which typically means "slightly above" 200 degrees, unless there are other sources avaliable.

    2 rolls in 4 seconds, in your own video.

    As for Rafale

    2:03, well over 200 degrees in 1 second.

    Instability is caused by difference in position between center of lift and center of mass. Close coupled canards create a low pressure area on forward part of the wing, thus moving centre of lift forward; and since effect remains even at high speeds, centre of lift shifts less. Long arm canards also affect center of lift, but only if they themselves are a lifting surface in level flight, as they do not have much effect on the wing. Is that so hard to understand, or you are trolling again?

    During sustained turn yes. Not so during instantaneous turn, and even during sustained turn close coupled canards help reduce drag due to elevon deflection and drag due to air flow separation.

    EDIT:

    This is what Bruno Revellin Falcoz said about canards:
    "Like many other aircraft makers, Dassault has selected a delta-canard configuration for its latest design. “As we were working with the other Europeans, we started to diverge significantly on the design” explains Bruno Revellin-Falcoz [Director of Dassault’s Technical Department]. “Ultimately, we made some radically different choices. They wanted fuselage-mounted canards while we preferred to locate the canards almost above the wing-root. The key advantage of this configuration was that it would channel the air flow over the wing apex, which is where lift-generating vortices are formed. The Eurofighter Typhoon uses its canards as simple control surfaces. Although this creates a significant lever effect, it loses the positive impact on lift and therefore aerodynamic efficiency. That’s why we are certain that the Rafale can handle much better than the Typhoon at high angles of attack, such as during the crucial phases of dogfighting and low-speed flight. While they were groping around in the dark, we benefited from the know-how accumulated through the Mirage III Milan, Mirage III NG and Mirage 4000 programmes."


    But of course, you know more than two companies that have been designing canard jet fighters since 1968 (Dassault Mirage Milan) and 1960 (Saab Viggen), respectively.

    By the way, Mirage Milan was a long-arm canard configuration, but that solution was abandoned in favor of close-coupled canard for Mirage IIIS:
    http://q-zon-fighterplanes.com/wp-content/uploads/2010/06/Dassault-Mirage-IIIS.jpg

    Rafale doesn't have any of Typhoon's aerodynamic issues such as transonic pitch up.
     
    Last edited: Sep 4, 2014
    samsonight likes this.
  14. BMD

    BMD Colonel ELITE MEMBER

    Joined:
    Nov 20, 2012
    Messages:
    10,798
    Likes Received:
    3,012
    Country Flag:
    United Kingdom
    Not based on other things you've said.

    So again, you know better than British, Russian, Italian, German and Spanish aerodynamicists.

    No, they work better because they're in the correct place to capture the air at high AoA. The variable intake lips enhance this effect.

    But the Su-37 disproves your earlier point about inlets and it isn't a delta. The delta MiG-1.44 went for a longer separation, in fact, in many ways, it looks like a large Typhoon.

    Rubbish, countless examples of other aircraft using this setup as I've already mentioned.

    As it would be for a CCC Typhoon. Seriously, move the canard back and the trailing edge is behind the inlet.

    And it was a manoeuvrability demonstrator with forward swept wings, not an air superiority fighter, so non-comparable.

    The trailing edge would be behind the inlet. Any idiot can see that.

    As they would be on a CCC Typhoon.

    Only with the top of the inlet.

    And we've just discussed how CCC wouldn't be any different with chin inlets or side inlets. It's in fact better with chin inlets because the vortex goes over the wing root.

    Then the double delta was replaced by a strake, which is effectively a less pronounced double delta.

    Yep, that's the LERX replacement for double delta. Clearly shows they're thinking about LCC vs CCC benefits and trying to get both but in the end they choose LCC.

    Now the LERX is being added again. All the CCC benefits plus the LCC benefits. Charlie Sheen win.

    None of your figures ever are, you should just stop quoting them and do everyone a favour. You clearly said:

    This demonstrates a clear failure to understand the very basic principles of lift and atmospheric air density variation with altitude. Something a high school student should know.

    So the figures have changed again?

    Picard, you are nothing more than a time-wasting clown. I will post it frame by frame later.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Are you stupid? That is only 270deg.

    Any instability they create they have to counter with the canards to prevent the aircraft flipping and since the pitching arm (separation between canard and centre of mass) is shorter, they have less ability to do that, hence they can't run as much stability because they wouldn't be able to control it effectively.

    You always have to counteract instability with the canards or the aircraft flips.[/QUOTE]
     
    Last edited: Sep 4, 2014
  15. Picard

    Picard Lt. Colonel RESEARCHER

    Joined:
    Feb 4, 2012
    Messages:
    5,864
    Likes Received:
    3,023
    Who had no experience in designing canard-delta fighters.

    So are Rafale's:
    http://f.ptcdn.info/392/006/000/1371707264-1726647-o.jpg

    And Gripen never had any major problems with high AoA despite its air intake positioning.

    It doesn't disprove, check the relative position of canards, they have significant lateral separation from air intakes.

    With close coupled canards.

    All of them invalid as I have clearly explained.

    Leading edge wouldn't be behind it, and as I pointed out, the only CCC aircraft where leading edge is not behind the inlet has significant lateral separation between canard and intake.

    In fact, what you are proposing is EFA configuration, which didn't work:
    https://defenseissues.files.wordpress.com/2014/09/m1a7g.jpg

    So why did you bring it up? And MiG-1.44 and Su-37 are also demonstrators that were never meant for serial production.

    And any idiot can also see that leading edge wouldn't be behind the inlet.

    You call this "almost level"?
    https://defenseissues.files.wordpress.com/2014/09/m1a7g.jpg

    Wrong. Typhoon's canards were moved forward because original position produced too much supersonic drag and negated lift gain that close coupled canards would provide.

    If you want optimum interaction between canard and air intake, you want something like Rafale:
    http://i146.photobucket.com/albums/r279/sampaix/Boundary-Layer-Control.jpg

    (A) shows splitter plate which creates a strong shock, which in turn slows down the air flow. Part of it enters the secondary air intake and cools avionics and engines, while most of it is redirected and accelerated towards points B and E. Air flow directed towards the upper surface (B) helps provide directional stability, much like strakes do. It may also reinforce canard root and LERX root vortices.

    Correct, but also irrelevant for our discussion.

    Because CCC didn't work with intake position they chose.

    Quite wrong. LERX only energizes inner portion of the wing and helps pitch and turn rates, but it does not really help roll rates, and as it cannot adjust to different flight conditions, its effect on both pitch and turn rates is less than that of close coupled canard. Rafale has both LERX and CCC.

    Nope. They never changed, 28 deg/s sustained is Rafale C, 24 deg/s is Rafale A.

    In case you didn't know, 270 degrees is well over 200 degrees.

    Pitch is also countered by trailling edge surfaces, so you are wrong again.

    EDIT:
    Rafale at high AoA flight, clearly showing that canards are at lower AoA than wing and thus drag less than canards in long arm configuration would (note that canards are not at negative AoA that would be required for them to provide pitch down moment):
    http://i146.photobucket.com/albums/r279/sampaix/rafale-001.jpg

    Which is true for all unstable aircraft, even those that do not have canards.
     
    Last edited: Sep 4, 2014
    samsonight likes this.
Thread Status:
Not open for further replies.

Share This Page