Filthie's Mobile Fortress Of Solitude

Filthie's Mobile Fortress Of Solitude
Where Great Intelligence Goes To Be Insulted

Thursday, 16 September 2021

Ground Looping

 



So… why do they do it? Everything I’ve flown has tricycle gear with a steerable nose wheel so ya can’t get in too much trouble. But hell’s bells: my experimental single engined Twinstar rocket ship comes in hot and the second the damn thing touches the ground it either makes for the stubfarts on the side or into the rhubarb! It wants to skew the same way each time too. 

I’ve tried feathering the throttles and applying rudder and I always end up goosing it and getting a ground loop the other way…. Any suggestions sincerely appreciated.

10 comments:

  1. I'm no engineer, but it would figure to me that the plane is either dog-tracking before it touches down, cocking the wheels off in one direction or the other on touchdown, or the landing gear is either not parallel with the fuselage or one wheel is lower than the other, creating ground drag on the low side as soon as the plane touches down...

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    1. Yep. Either main gear alignment or you’ve got a dragging bearing on one wheel. I’m assuming no wheel brakes, yes? Does only pull on landing and is it pulling opposite the p-factor? Higher torque p-factor at max might compensate for the pull on take off roll, but it’ll show up at lower throttle inputs on appr & landing. Does it fly straight? I’ve come across mis-rigged floats on all sorts of bugmashers that’ll cause tge thing to fly sideways. Check your vertical stab & rudder rigging too. Will it start to loop before the tail skid touches down? That points to MLG issues. If not, your tail skid may be offset and skewing things. (Sorry, I’m a 40+ year aircraft mechanic....I live this kinda stuff every day.)

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  2. Have you tried locking the tailwheel?

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  3. This behavior is inherent to the basic design. The wheels are necessarily ahead of the balance point (center of gravity). This makes the vehicle dynamically unstable, like a fork truck or a grocery cart being pushed backwards. It occurs in everything from Cubs to B-17s. Takeoff and landing, happy feet don't sleep. Constant attention to the rudder is required.

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    1. Exactly. The classic work on the subject is Stick and Rudder by Wolfgang Langewiesche (1944). Absolutely removed any desire to fly a taildragger. I've done a lot of shitty landings, including getting stuck in mud when I rolled out into turf that was soft as jello from recent rains (and poor drainage), but I've never ground looped with tricycle gear.

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    2. Yeah but … as an RC guy… some of the tail draggers don’t do it hardly at all. One of the stubfarts has a Spad and that thing tracks straight as an arrow. Another had a de Havilland and that whore tracks like a wheelbarrow going backwards…

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  4. Ya got to keep the tailwheel well within the tracks of the mains...wonder near the edges or beyond and you will go arse over teakettle... ya got to keep your toes moving all the time.

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    1. I get that but when ya slow down… your rudder goes mushy… at that point you start riding the toe brakes I guess… but unfortunately my RC birds don’t have those…

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    2. I wonder if moving the CG aft a little would help any.

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