Jose and Roy,

The problem with a TC that is getting a little worn is not that it does
not respond to roll, but that it responds too much to roll. The
internal dashpot is supposed to damp out its response to small,
instantaneous roll hits, so all we see on the needle is either turn, or
a continuous roll. But if the dashpot is worn (the seal wears out and
the fluid leaks out just like the McPherson struts on your car), the
needle goes 'nuts' on every little roll bump, and pegs the needle to
whichever side the roll was towards, regardless of your direction of
turn. The result is that in turbulence all you see is a series of
full-scale left and right deflections, none of which represent your
rate of turn. It's pretty much impossible to control the aircraft
partial panel this way, and if you try you are very likely to get into
an extreme unusual attitude.

The test: during taxi, put the aircraft in a taxi turn at standard rate
on the TC. Suddenly straighten the turn out; the needle should take
2-4 seconds to get back to 1/2 standard rate of turn. If it comes back
faster than that, it is underdamped. If slower than that, the gyro is
probably not turning at full speed, usually due to the bearings wearing
out (tho this is usually hailed by an annoying whine when you first
apply electrical power, something like a Boeing jet starting up...)
Gene