After going over one of my older questions about forward swept wings, I realize I have never seen a forwards-swept horizontal stabilizer. Do they exist? What would be their advantages, if any?
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$\begingroup$ I think one of the main drawing points for forward swept wings would be the stall characteristics. Because of the way the air flows over the wings, the tips always stall before the root (or so I think I remember). They will also have better controllability in transonic and supersonic speed profiles. I suppose the elevator could have the same resilience to pressure waves from going supersonic, but I don't think the stall characteristics would matter as much. $\endgroup$– alexMar 25, 2017 at 12:22
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$\begingroup$ This is a very interesting question. I too cannot find any aircraft designs with forward-swept horizontal stabilizers. $\endgroup$– Juan JimenezApr 10, 2017 at 19:56
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2 Answers
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Forward sweep is chosen when the designers value resistance against tip stall and a rear location of the wing spar higher than low mass. None of those advantages of a forward swept wing has any weight in the design of a horizontal tail, so a forward swept tail has never been selected.
answered Apr 19, 2017 at 20:49
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The HFB Hansa , a business jet made in Germany in the 60s used forward swept wings, as did several research jets in the 60s -70s but I don't think any had a forward swept stabilizer. Forward swept lifting surfaces have the advantages of rearward swept surfaces, delaying shock wave formation to higher Mach number by reducing the effective thickness of the airfoil, without some of the disadvantages, tip first stall, decreased roll response, decreasing effectiveness at high angles of attack. But the forward swept lifting surfaces have disadvantages as well like, the requirements for much stiffer structure to avoid flutter and more tendency for Dutch roll.
With the advent of fly by wire, and the relaxed stability requirements that go along with it, the horizontal stabilizer on many new aircraft are operating at very low lift coefficients in cruise so I am not sure if there would be much advantage, except perhaps in a fighter optimized for gun fighting (close in high turn rate, heavily g loaded condition). The flutter issue is much easier to design for today, since we have extremely high modulus, low mass, graphite fibers we can use but nobody even seems interested in going with a forward swept wing, much less a stabilizer.
The aviation industry seems to have settled into a very conservative mind set after the heady days of the cold war, probably due to the immense cost of developing truly new technologies. I don't think we are likely to see a production forward swept, wing or tail, aircraft for quite some time.
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1$\begingroup$ this is more comment/speculation on your side, rather than an actual answer. $\endgroup$– FedericoMar 20, 2017 at 22:07
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$\begingroup$ Do you have a better answer, Federico, or just another opinion? @strato man, there's an example of fwd swept tail that has been in production for a very long time, the Mooney. :) $\endgroup$ Apr 10, 2017 at 19:55
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$\begingroup$ @JuanJimenez I have neither an answer nor an opinion, but this does not make this post any better. $\endgroup$– FedericoApr 20, 2017 at 12:26
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$\begingroup$ @federico Your comment is an opinion. I for one disagree with you. $\endgroup$ Apr 21, 2017 at 13:03
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1$\begingroup$ @Federico Yes. It shows. Since you are hell-bent on it, I'll give you the privilege of having the last word. $\endgroup$ Apr 23, 2017 at 17:56