8

The Rafale and the Gripen are quite similar but the Eurofighter Typhoon has the canards far forward. I've been told that this was due to the shape of the air intake.

Apparently the Typhoon's air intake was designed to work in combination with thrust vectoring control. This feature was never implemented so I believe the canards may be less effective than other aircraft, in terms of performance, (specifically turn/pitch rate). Am I totally wrong?

close coupled canard Vs long arm canard

Rodrigo de Azevedo
  • 1
  • 1
  • 9
  • 28
O'Terror
  • 1,383
  • 13
  • 23
  • 1
    Longer arm means less force needed from the canard, so less drag, especially at high speed when lift center shifts backwards and requires more lift from the front. Shorter arm means the wing can benefit more from the vortex. Basically if you want high speed then long, or high manuveribility then short. – user3528438 Aug 18 '20 at 01:33
  • 1
    Do you have any sources for that? I would have expected quite the opposite. – user33651 Aug 18 '20 at 06:04
  • 1
    @hph304j, no way, this is because vortex from the close coupled canard (Rafale jet fighter)energises the airflow on top side of the wings like vortex generators system ,from that gain agility.Look at videos of the Rafale demo. – George Geo Sep 20 '22 at 04:41
  • @GeorgeGeo but given the fact that user3528438 cleary states that the longer arm means less force for a given needed moment, i would suspect, that the eurofighter can generate a much bigger pitching moment at full deflection than the close coupled canard, which should translate into higher maneuverbility. – user33651 Sep 21 '22 at 18:53
  • The thing is like that ,Canards used in Eurofighter are big and after initial deflection to give the desired AoA ,they return in the same angle as airflow to not overshooot (their movement is not big in flight ).Their main Role Is stabilisation . – George Geo Sep 24 '22 at 02:22

1 Answers1

5

The Viggen was the first canard aircraft ever to be built in production quantities. Its close-coupled canard is fixed, with landing flaps being the only movable part. Its purpose is solely to maintain aerodynamic flow over the wing at high angles of attack and thus enhance both manoeuvrability and low-speed handling. Saab were not able to develop movable canard technology in time, nor was it necessary in order to meet the aircraft specification. Nevertheless, getting the darn thing into production after 60 years of failure was a staggering achievement.

The Gripen, Rafale and Typhoon canards are also used to maintain high-alpha airflow. However theirs have an additional function as control canards. Their own angle of incidence can be varied to help control aircraft pitch directly, to contribute to other more subtle manoeuvres, and (at least in the case of the Typhoon) to minimise radar cross-section.

The further forward a control canard is placed, the smaller it need be to provide sufficient control authority, just as a long rear fuselage allows a smaller tailplane. Its only real issue is that it interferes more with pilot visibility, but its smaller relative size minimises that.

Guy Inchbald
  • 7,042
  • 18
  • 36
  • 1
    The Grippen canard is, however, also an all-flying control canard. What Viggen has is largely irrelevant for this comparison. – Jan Hudec Aug 17 '20 at 20:22
  • Thanks, I must have read the question wrong. I have edited my answer accordingly, but have left in the Viggen bit as it has got a couple of upvotes so must have interested somebody. – Guy Inchbald Aug 18 '20 at 17:54
  • "Nevertheless, getting the darn thing into production after 60 years of failure was a staggering achievement." That sounds like a story, do tell! – Kenn Sebesta Aug 01 '21 at 14:38
  • @KennSebesta That would need a new question. Basically, avoiding all the pitfalls the canard can offer is hard. By the late 1960s, the credibility gap was not the least of them. – Guy Inchbald Aug 01 '21 at 15:35
  • The forward canard of the EF-2000 also interferes with intake aerodynamics. Where else do you have an engine which is directly influenced by pitch control commands? – Peter Kämpf Aug 02 '21 at 05:28
  • @Peter, MiG-21, but in a different way. Like any axial (conical) supersonic intake, it's not very tolerant to AoA changes. So the cone moves forward at higher AoA. But instead coupling it with the AoA sensor, it is actually coupled to the stick position (and Mach, of course). – Zeus Aug 03 '21 at 01:54
  • @Zeus That's why I said directly. All belly intakes use forebody compression on purpose to increase trans- and supersonic thrust at high AoA. But in the EF-2000 it is already the canard position by itself, regardless of AoA, which influences thrust. – Peter Kämpf Aug 03 '21 at 06:35