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I'm wondering why modern widebody aircraft (such as B787/777, A330/350 etc.) don't use horizontal stabilizers with T-tail configuration. What's the difference between placement of this element? There are quite a lot of military planes (C-17) and smaller ones that use it (Fokker 70, CRJ-9) in T-tail configuration, as shown here:

enter image description here

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A horizontal tail on top of vertical tail would require strong and heavy structures, which in turn is not good for economics of flight. The bigger the plane is, the more challenging the loads the tail has to handle are, so what might be a feasible solution on a regional jet might not work at all for a large jet.

T-tails are an obvious choice when the engines are tail mounted, and in C-17 I guess the main reason is to keep the tail away from the wake of the main wing in certain "areas" of flight envelope: C-17 is a high wing configuration, and as a military aircraft it is subjected to more "challenging" flight states.

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    $\begingroup$ Military cargo aircraft also need to be able to land on unimproved runways, and quickly unload large items like trucks & tanks. The T-tail would seem to make it easier to design a nice, wide rear ramp for this. $\endgroup$
    – jamesqf
    Oct 5 '21 at 16:52
  • $\begingroup$ You have good points there, the h-tail beig set higher, it is pretty much save from sand, rocks, dust and whatnot the engines and tires will kick up during ground roll/rotation. Mind if I borrow this into my answer? $\endgroup$
    – Jpe61
    Oct 5 '21 at 18:21
  • $\begingroup$ @jamesqf On the other hand, there is the C130... Maybe underwing turbofans are more likely to throw up debris? $\endgroup$
    – sdenham
    Oct 5 '21 at 21:14
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    $\begingroup$ @sdenham: The C-130 is a pretty old design (close to 70 years), and per Wikipedia inherited a lot from previous designs. Maybe the designers back then didn't think of a T-tail, or figured the tradeoffs weren't worth it? $\endgroup$
    – jamesqf
    Oct 6 '21 at 2:44
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    $\begingroup$ @jamesqf My comment to this has been written three years ago already. $\endgroup$ Oct 6 '21 at 21:23
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It might have something to do with the super stall phenomenon in which a stalled wing blankets a T-tail.

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  • $\begingroup$ Isn't deep stall mostly a problem for small GA planes? An airliner could easily be designed to handle it with the autopilot, and airliners are not flown close to a stall condition anyway. The only airplanes where a deep stall is a very serious concern, are gliders, because they are flown closer to their stall conditions than any other plane. Yet even among gliders you can occasionally find T-tail configuration, and not all of them are in danger of a deep stall. For example, the IS-28b won't deep stall, yet the single-seater variant (IS-29d) can. Both have T-tails. $\endgroup$
    – vsz
    Oct 6 '21 at 5:48
  • $\begingroup$ I should check, but iirc super stall and deep stall are not synonymous. $\endgroup$
    – Jpe61
    Oct 6 '21 at 9:14
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    $\begingroup$ @vsz "An airliner could easily be designed to handle it with the autopilot". Ah yes, the 737-8 function? In short, it is a bad bad idea to design in a flight problem, that you then need to automate out for the plane to be functionally flyable. If your automation errs, your plane stops flying $\endgroup$
    – PcMan
    Oct 6 '21 at 13:46
  • $\begingroup$ @vsz Deep stall was the cause for several crashes, notably of the BAC One-Eleven in 1963 and the HS Trident three years later. Tupolev, when learning of the first crash, increased the size of the horizontal tail of the Tu-134 by 30%. The British engineers were less able to learn from their mistakes. $\endgroup$ Oct 6 '21 at 17:20
  • $\begingroup$ And as for super stall, a good example would be the saab draken, with it's hideous stall characteristics... $\endgroup$
    – Jpe61
    Oct 6 '21 at 18:17

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