CBL hasn't suggested that it's particularly hard, just different. Tailwheel pilots (myself included) tend to say "it's no big deal", but this doesn't stop just a teeny bit of preening going on: "ha! I have tamed the wilful beast andf am a p-roper pilot or, indeed, an aviator, as in the days of yore").
I hope that Mr John Farley will not object if I cut and post here a very interesting short essay on ground loops which he posted on pprune a year or so ago. As in all his writings, he explains things very clearly. Here it is:-
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Ground Loop
If you have a paper and pencil, the whole subject takes 30 secs to cover but I don’’t know how to put the appropriate diagrams up here, so a lot of words now follow
Ground loops happen because of the force due to friction that exists between a tyre and the ground.
When an aircraft touches down with a zero drift angle we can ignore the friction forces (sure they have to spin up the wheel but once that has happened the wheel just rolls and does not disturb the aircraft)
But when a wheel touches down with a drift angle, friction causes a drag force which acts 180 deg out to the direction that the aircraft is travelling (not the direction it is pointing). Visualising this is easy if you take an extreme case like 90 deg of drift (!)
This force is not in the plane of rotation of the wheel, so for our convenience we can split it into its two components, one in the plane of the wheel and the other at right angles to the plane of the wheel. It is the one at right angles to the wheel that creates the piloting problem.
Any force applied at right angles to the wheel is ACROSS the long axis of the aircraft and so will make the aircraft yaw.
Whether the yaw so produced REDUCES the original angle of drift or INCREASES will either make our day or spoil it.
So, and thinking only about the main wheels, if you land with the nose heading to the left of the runway and with the aircraft tracking down the runway, the nose will tend to snatch further left (bad) if the main wheels are in front of the CG (taildragger) but pull round towards the runway heading (good) if the wheels are behind the CG (tricycle).
This is the crux of the issue, weight is not strictly speaking a factor. What is a factor is the yawing inertia of the aircraft as this RESISTS the tyre induced yaw whichever way it acts. Thus, for a low inertia aircraft (probably light and short) things will get better or worse very much more quickly than for a high inertia aircraft (probably heavy and long)
I think it is important to recognise that during a ground loop the CG continues to move over the ground essentially in the direction it was travelling at touchdown but the aircraft ROTATES in yaw about the CG (as opposed to a notion of the CG being flung out sideways)
The last time I did a ground loop (it was a secret between me and about 6000 people at the airshow) the aircraft stayed on the runway centreline but remorselessly yawed to the right until I was going straight, but backwards, down the runway (at this point I knew what to do –– open the throttle, until I finished up going forwards and calmly taxy towards the turn off I had just missed……..)
If I have explained things well enough that you are happy with the above all the rest of the ground loop stuff follows easily:
They are less likely to happen on grass as it tends to produce less friction than tarmac.
If you have a tailwheel lock, then the side force from the tailwheel will be stabilising (behind the CG) If you forget to lock the tailwheel it just castors and produces no stabilising effect (bad)
Now you can see why tailskids provide nicer handling ON GRASS, as they tend to dig in more than tailwheels and so enhance their stabilising effect.
You can also see that ground looping on take off is perfectly possible if you let ANY yaw go uncorrected for more than a moment. If you do this the aircraft momentarily continues on its original tack, but points to the side, and bingo the tyres come into play. With a high powered piston, the initial yaw can easily happen due to a torque induced swing or from raising the tail a tad quick and generating a gyroscopic yaw from the prop.
My ground loop (in Bob Mitchell’’s Ryan PT 22) was caused by me being an idiot and lowerering the tail too fast after a main wheel only touchdown –– plus a strong cross wind with a tail component, trying to help the busy controller by expediting my arrival between displays and all that sort of stuff that you know you should not do.
JF
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Alas, the only thing which my flying has in common with Mr Farley's is that I prefer to ground loop in front of an appreciative audience (all those nice spotters at an Old Buckenham fly-in waved and cheered so kindly, assuming that I was displaying the balletic grace of my aircraft on the ground just for them).