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How different is V-tail from a conventional tail in the perspective of aerodynamics & flight dynamics of aircraft?

I have seen that many UAVs, like the General Atomics MQ1 Predator, LSI Amber, Mini Harpy, etc have a V-tail. Why is it so?

There are answers on how V-tail reduces the weight and drag but nothing on the dynamics of aircraft.

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As you stated, V-tail has some advantages and some disadvantages when compared to conventional tail assembly. In case of UAVs the disadvantages are negligible, leading to them being a relatively common choice.

The advantages of V-tails are that they have fewer surfaces and (thus) fewer intersections, and they are lighter than a comparable conventional tail. All of these lead to less induced and parasitic drag, enhancing the efficiency of the overall design.

The downsides are susceptibility to yawing and more complex control arrangements with "fly-by-cable". To achieve the same stability as a comparable conventional arrangement, a longer rear fuselage is required.

On UAVs the control system is essentially direct drive, so control logic is managed by software instead of relatively complex arrangement of cables, pushrods and pulleys (as in the V-tail Bonanza [IIRC]). Software can also easily address any issue with stability, and since high maneuverability is not top priority in UAVs, control logic can be programmed as quite "conservative". Basically UAVs are not put into extreme flight conditions, so the adverse properties of V-tail are not an issue.

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    $\begingroup$ The mechanical control arrangement requires a "mixer", a little set of bellcranks to regulate pitch and yaw inputs/outputs, but beyond that though, the complexity isn't that significant. The main flight behaviour issue is yaw excursions in turbulence because vertical gusts, that are offset off the vertical, impart a yaw force as one surface is affected more than the other. This nose hunting in turbulence was the problem with the Bonanza. With a FBW or yaw damping system, the issue is masked. $\endgroup$
    – John K
    May 6 at 14:31
  • $\begingroup$ True, it's not all that complex @JohnK , but more complex than the conventional setup. I remember when I was a kid it was so inspiring trying to sketch out a cable and pulley setup that would execute proper movement of control surfaces 🙂 $\endgroup$
    – Jpe61
    May 6 at 17:17
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    $\begingroup$ A friend was checking out his new glider purchase the other week, with a V tail, and it took a couple of minutes for him to figure out ruddervator movements when he was doing control checks, because he would move the surface while someone held the stick, but the rudder pedals would just give away. He was pretty confused for a second or two lol. $\endgroup$
    – John K
    May 6 at 17:23

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