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Reading this question got me wondering: From what I've heard and read about taildraggers, brakes are needed during takeoff and/or landing rolls to maintain directional control and prevent a ground loop. At low airspeeds rudder authority is insufficient to keep the plane going in a straight line.

How is this achieved when skis are mounted instead of wheels? Is there anything special about skis that makes them more controllable than wheels in these situations?

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I have a fair amount of ski time on Cessna 180s and Citabrias. It's a bit like flying floats. The main thing is, you have no brakes.

For lateral control, the skis have varying amounts of lateral compliance depending on the snow compaction, so you slip and slide more or less for each situation, but generally, the laggy reactions makes it easier to control direction on takeoff and landing compared to wheels. The compliance is like being on wheels on wet grass; instead of darting to the side when the plane swings, it just kind of sashays laterally giving you more time to make corrections.

You may have a ski on the tail, which provides a limited amount of steering control to the extent that the ski design is able to bite sideways (a little skeg on the bottom really helps). A decent tail ski on lightly compacted snow provides pretty good steering control without having to use large blasts of power to blow the rudder. Otherwise, you are dependent on large blasts of power to blow the rudder to turn.

On ice or very deep powdery snow, you will be depending more on power to turn, and this is quite a challenge because the shot of power to get the tail to swing to turn also accelerates you forward, and remember, you have no brakes.

Bottom line is you can't really maneuver in tight spaces when on skis without using huge bursts of power, and annoying the local owner whose airplane may be in your prop wash, so it requires a lot more preplanning and thinking things through.

Some airplanes do without a tail ski, keeping the normal tailwheel, and this makes it easier to maneuver on compacted snow where the tire has some bite. On deep loose snow, the tailwheel becomes an anchor, and you have to lift it out of the snow with shots of power and elevator, on top of lots of rudder to try to maneuver. That can get exciting. A tailwheel-only ski plane in deep snow is a pain. For aircraft with wheel-skis, you normally see a tail ski with a penetrating wheel to do double duty.

So, you have no brakes. So you have to do run-ups on the move, either in a big circle if you have the space, or on the takeoff "roll" if you don't.

Then there's landing at the end of a sunny warm day on a compacted runway and the temperature drops below freezing in the late afternoon as the sun sets, and the runway has a bit of a downhill slope to it, and it's essentially compacted snow with an ice glaze. Did I mention that you have no brakes? Been there, done that.

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  • $\begingroup$ re : "(a little skeg on the bottom really helps)"-- was going to speculate in my answer that it would be only logical to have some sort of skeg to give the tailwheel ski a little extra "bite"-- great answer. $\endgroup$ – quiet flyer May 10 at 16:24
  • $\begingroup$ Sounds like reverse would sure have come in handy! $\endgroup$ – UnrecognizedFallingObject May 11 at 1:41
  • $\begingroup$ When that happened, it was a Citabria and I dimly remember (it was about 1978) using what little directional control I had to head for uncompacted snow on a flat area off to the side to get slowed down. If the runway had berms on each side that prevented that sort of excursion, I would have ended up in the fence at the end. Yeah reverse would be handy, as it would be on floats. On floats you have to get good at shutting down with mixture while still 50 feet away and coasting up to the dock. $\endgroup$ – John K May 11 at 3:01
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You maintain control using the rudder (and throttle)...

It takes a lot of power to taxi around on ski's, meaning you are creating a lot of wind with the prop wash. On wheels you can idle around and move, but on skis, even though you are on snow/ice, it still takes a lot more power to move you. If you want to change direction but go slow, you need to put in power, make the correction, then remove it.

Push rudder then quick blast of power.

It's reported that its difficult to ground loop an aircraft on skis (but not impossible). The aircraft tends to slide sideways rather than tip over.

Some aircraft also have wheels on the skis:

enter image description here Source: GeneralAviationNews

And that may help by using traditional methods to maintain directional control, although if the wheels are in deep snow it probably does very little in that regard.

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From what I've heard and read about taildraggers, brakes are needed during takeoff and/or landing rolls to maintain directional control and prevent a ground loop.

This isn't meant to be a complete answer to this question, but it might help inform your understanding of the differences between operating a tailwheel aircraft on wheels versus on skis to point out that there have have been many tailwheel aircraft lacking brakes entirely (e.g. World War 1 era aircraft.) In many tailwheel aircraft, brakes really aren't an important part of maintaining directional control in most situations, except while taxiing. Attempting to use the brakes to maintain directional control as a tailwheel aircraft is decelerating after landing can actually re-inforce any left or right "swing" of the nose that is taking place, especially in cases where the landing gear "track" (distance between the main wheels) is relatively narrow, and thus can tend to cause a ground loop rather than to prevent it.

Another point worth noting is that when a tailwheel aircraft is on skis, the tailwheel will often have its own small ski, which also helps with directional control.

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    $\begingroup$ (links to authoritative external sources discussing the best techniques to use in various tailwheel aircraft would be helpful here) $\endgroup$ – quiet flyer May 10 at 12:53

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