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Someone said a canard wing is more prone to icing than a stabilizer. If true, what would explain this?

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    $\begingroup$ "someone" who? when? where? link? $\endgroup$ – Federico Dec 15 '15 at 9:29
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    $\begingroup$ "a friend" :-) an answer stating it's not correct or determined by other factors would be just as accepted $\endgroup$ – user Dec 15 '15 at 9:36
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It has to do with the local speed around the airfoil.

In a canard configuration, the forward wing has to produce more lift per area than the main wing in order to have natural longitudinal (or pitch) stability. This means the suction is more intense, and the pressure on the upper side of the airfoil right behind the leading edge is lower than on the main wing. Also, the angle of attack of the wing is higher, presenting a larger area to the oncoming flow. Large droplets of supercooled water will simply splash on the leading edge and freeze there instantly, causing clear icing.

In a conventional aircraft the tail surface will provide very little lift, and in many cases even produces a small downforce. Now the main wing shows lower pressure on the forward part of the airfoil, just where ice collects the most. In the special case where the tailplane is in the wake of the wing, some of the water droplets will have frozen to the wing already and less water will be available to cause tailplane icing.

The capacity of air to hold water depends not only on temperature, but also on pressure: The lower the pressure, the more likely it is for condensation to happen. Condensed, super-cooled water, or liquid water hitting a cool surface, will form ice. Now you have both components needed for the explanation.

Pitch stability is the explanation for the higher propensity of canard wings to collect ice than conventional tailplanes!

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If the canard has a thinner leading edge compared to the stabilizer, this could happen. From BEA Systems Think Ice:

A relatively large radius aerofoil at moderate or low airspeed creates a larger pressure wave ahead of the leading edge, which forces the air around it, carrying most of the moisture with it. Only droplets sufficiently heavy to overcome this flow will impact on the leading edge. Thus, a large chord aerofoil with a blunt leading edge has low ice accretion efficiency. Conversely, a narrow radius leading edge generates a smaller pressure wave and so the accretion rate is greater.

Note that by the same token, the stabilizer is more prone to icing compared to the main wing.

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  • $\begingroup$ Of course the leading edge radius has also a role in icing characteristics, because a small radius will cause higher suction peaks (= lower pressure) on the top surface than a large radius. But it can not explain the relative difference in icing between canard wings and tailplanes. $\endgroup$ – Peter Kämpf Dec 15 '15 at 15:46
  • $\begingroup$ @PeterKämpf smaller radius also causes larger water vapor gradients (than around less curved surfaces) and will be preferential locations for ice growth independent of the pressure anomaly. $\endgroup$ – casey Dec 15 '15 at 21:46
  • $\begingroup$ @PeterKämpf You're wrong, it can indeed very well explain the difference. In aircraft icing the total accretion is heavily depended (not only in volume but in the form of the ice shape etc.) on collection efficiency. You speak about suctions peaks, pres. grads etc. but you're forgetting that we talk about multi-phase flows. To put it simple, if you have no water there, it wont freeze. The combination of airfoil thickness and the distribution of droplet's mean volume diameter in the cloud are major factors in aircraft icing. Also, for conventional config. the wing is "shielding" the tailplane. $\endgroup$ – ares Oct 13 '17 at 4:36
  • $\begingroup$ A relevant paper -> ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050186904.pdf $\endgroup$ – ares Oct 13 '17 at 4:47

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