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Trying To Understand V-tail Theory  
User currently offlineHappy-flier From Canada, joined Dec 1999, 299 posts, RR: 0
Posted (9 years 8 months 3 weeks 3 days 16 hours ago) and read 4150 times:

For the longest time I have had the desire to understand the physics behind the V-tail design. I like this tail design for the simple reason that it seems to be one of the best configurations for a hypothetical roof-mounted, single-engine jet- (or ducted-fan-) powered version of something like a Lake amphibian. (I'm not designing one, but it never hurts to dream a little ...  Big grin). The other ideal tail type for such an aircraft would probably be an ordinary horizontal stabilizer possessing two vertical stabilizers at the end of each stabilizer - kind of like a Connie tail, but obviously without the central fin.

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And, so, here are some of my questions:

  • How do you perform lateral maneuvres in a V-tail aircraft when the tail assembly must also function to control pitch?

  • How do you correct for a crosswind during takeoff?

  • How do sideslips get done in a V-tail aircraft?


  • Just some basic ones to get going. Many thanks in advance.


    May the wind be always at your back . . . except during takeoff & landing.
    5 replies: All unread, jump to last
     
    User currently offlineCancidas From Poland, joined Jul 2003, 4112 posts, RR: 11
    Reply 1, posted (9 years 8 months 3 weeks 3 days 14 hours ago) and read 4079 times:

    while i never flew a v-tail aircraft this was once explained to me by a half-drunk pilot out at the airport. according to him, control inputs were the same as they are on an aircraft with conventional control surfaces. the mechanism for those ruddervarots actually handles any differences. i didn't exactly believe him then. wonder if i should at all, anyone have a better explanation?


    "...cannot the kingdom of salvation take me home."
    User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 26
    Reply 2, posted (9 years 8 months 3 weeks 3 days 12 hours ago) and read 4023 times:

    As far as yaw/pitch control goes, v-tail arrangments require a complex control mixer which the pilot of such an aircraft may be able to explain to you better than I can. I assume such a mixer is just some sort of automatically balanced input-deflection balancer which produces the desired movement.

    V-tails are quite prone to dutch roll problems (due to their large effective dihedral), and they impose greater loads on the tail section of aircraft than do normal tail designs. However, V-tails provide good spin-recovery characteristics and produce slightly less drag than conventional tails (through a reduction in interference drag, not parasite drag - after all, the same total surface area is needed to maintain the same stability and control forces).

    Cheers,
    QantasA332


    User currently offlineLeanOfPeak From United States of America, joined Oct 2004, 509 posts, RR: 1
    Reply 3, posted (9 years 8 months 3 weeks 3 days 4 hours ago) and read 3932 times:

    Everyone so far is right.

    To give you an impression of how messy the control mixing is...

    Both ruddervators deflect up or down to control pitch (So that the horizontal components fight each other and cancel out and a pure pitching moment is obtained).

    For yaw, one ruddervator deflects up and the other deflects down (So that the vertical components fight each other and cancel out and a pure yawing moment is obtained).

    And for a given input of yoke position and rudder pedal position, there is a specific configuration of those two control surfaces that matches it.


    User currently offlinePPGMD From United States of America, joined Sep 2001, 2453 posts, RR: 0
    Reply 4, posted (9 years 8 months 3 weeks 3 days 3 hours ago) and read 3908 times:

    Cancidas,

    You got a better explanation than I did when I first asked how it worked. The MX guy's answer was PFM.

    LeanOfPeak,

    That's exactly how I have seen how the they work in flight. Now there is an issue, the V-tail models have less overall rudder authority than the conventional tail models. Which can be an issue when you are landing at airports with a single runway, sometimes you simple run out of enough rudder to line yourself up.

    The V-tails are fun to fly, but there advantages are few, you get at most a couple of knots over the convention tail, smaller engine bonanzas, and they have a knack of flying off in flight (I kid on that one, but there was an issue, that required the issuing of an AD). It is kind of fun flying them, but in the end it's not much different than any other doctor killer, it just looks cool with the V-tail.



    At worst, you screw up and die.
    User currently offlineWingscrubber From UK - England, joined Sep 2001, 845 posts, RR: 0
    Reply 5, posted (9 years 8 months 3 weeks 1 day ago) and read 3719 times:

    I had this explained to me on my aircraft maintenance course at college by a guy who'd worked on bonanzas, leanofpeak is exactly right but you must consider that in terms of the control mixing, the pitch/elevator function of the flight surfaces has priority over the rudder function. I was told that this is achieved through a sprung link in the rudder control, so if pitch and yaw inputs are made at the same time the pitch input can overcome that of the yaw on whichever flight surface is required to move. I did a really cool diagram of how it all works...if I had it I'd scan it in and show you but no idea where it is heh.  Smile/happy/getting dizzy

    -Pete



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