Do stealth-focused aircraft have canard configuration? I believe canards have a negative impact on the radar cross section.
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1$\begingroup$ "stealth designs" is rather broad. Aircraft like the Rafale and Typhoon incorporate stealth features, but are not optimized for stealth at the cost of all else. The F-22 and F-117 are more stealth-biased than Rafale and Typhoon. $\endgroup$– HobbesFeb 13, 2019 at 8:27
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$\begingroup$ I think @NitinG is referring to stealth-focused designs like the F-22 and Su-57. $\endgroup$– JihyunFeb 14, 2019 at 15:54
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2 Answers
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So far, no operational stealth aircraft has had a canard wing as the canards do affect the radar cross section.
However, a few experimental and under development under development aircraft have canards, like the Chengdu J-20.
"J20 2" by V587wiki - Own work. Licensed under CC0 via Commons.
The Sukoi PAK-FA, on the other hand uses movable Leading Edge Root eXtensions(LERX), which are much more stealthy and are shown drooping down in the following figure.
Source: defenceindustrydaily.com
There are a few major drawbacks with the traditional canard designs:
- Planform alignment Most of the canards are in aircraft for stability and aerodynamics requirements an as such are not amenable to planform alignment, as their characteristics are sensitive to their shapes and sizes. For example, compare the planform alignment in case of F-22 and Eurofighter Typhoon.
Source: forum.keypublishing.com
Some low observable aircraft, like the Boeing X-36 did have planform alignment, it is simply that it is difficult to achieve.
"McDonnell Douglas X-36 planform" by NASA/Dryden Flight Research Center - http://www.dfrc.nasa.gov/gallery/photo/X-36/HTML/EC97-44165-151.html. Licensed under Public Domain via Commons.
- Canard Angle Most (not all) of the canards have an anhedral or dihedral due to aerodynamics requirements, which means that they are not in the same plane as the wing and reflect radar waves in other directions, increasing RCS. The following image shows the (mis)alignment of canards with the aircraft.
Source: forum.keypublishing.com
More reflecting surfaces Having canards basically means there are two extra surfaces to reflect the radio waves and increase RCS.
Interaction with fuselage and wings The diffracted (radio) waves from the canards can impact on the wings and fuselage and get reflected back, which can increase the radar cross section.
answered Oct 7, 2015 at 11:02
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$\begingroup$ The comparison between F-22 and EF-2000 (or the other canard designs) is not really fair. F-22 was specifically designed for stealth and the angles were adjusted to match while in all the other designs the angles were left at whatever made most sense aerodynamically. It does not prove that adjusting them would have higher aerodynamic penalty in the canard case than in the horizontal tail case. $\endgroup$ Oct 7, 2015 at 12:29
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2$\begingroup$ @JanHudec which is what I'm trying to say- aerodynamic and stealth requirements don't (usually) match. Though we may never know the trade-off (between stealth and aerodynamics), there are some hints- The Chines dropped the canards in J-20 in their (next) stealth aircraft, the J-31 and the Russians moved from canards to LERX in PAK-FA, while maintaining the maneuverability from Su-30 $\endgroup$ Oct 7, 2015 at 12:35
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$\begingroup$ I agree with most of the answer. I just say the particular image is misleading, because the mismatch is there for both canards and horizontal tail. It is not like Lockheed switched away from canards to conventional tail when designing F-22; none of the earlier US fighters uses canards either. $\endgroup$ Oct 7, 2015 at 13:04
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$\begingroup$ @JanHudec I think I see your point. I just wanted to point out the importance of planform alignment and its effect on using of canards in stealth aircraft; I wasn't trying to compare two aircraft with different stealth requirements. $\endgroup$ Oct 7, 2015 at 13:30
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$\begingroup$ Would u mind editing in a quick sentence or a link to define "planform alignment?" Although the diagram indicates it I had to go look it up to make sure I was understanding correctly. I found this on the web: "Planform alignment is a technique for reducing an aircraft's radar cross section by orienting all the flight surfaces of the aircraft at the same angles." $\endgroup$– TomMcWOct 7, 2015 at 18:46
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Canards can be stealthy. There is a very interesting Oregon State University lecture given by Dr. Paul Bevilaqua about the F-35 that actually shows a canard fighter.
The point here is that you use computer models to optimize radar return, especially to the front but also to the rear. A fighter that doesn't look optimized might still be.
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$\begingroup$ Welcome to the site. Link-only answers are generally discouraged here to combat link rot. It would be preferable if you'd explain in your own words what is the main point being made in the linked video. $\endgroup$ Feb 13, 2019 at 15:12
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$\begingroup$ <Result: [..]> what does that have to do with the question? $\endgroup$– FedericoFeb 14, 2019 at 15:19