  The Five-hundred-meter Aperture Spherical Telescope (FAST) will become one of
the world-leading telescopes for pulsar timing array (PTA) research. The
primary goals for PTAs are to detect (and subsequently study)
ultra-low-frequency gravitational waves, to develop a pulsar-based time
standard and to improve solar system planetary ephemerides. FAST will have the
sensitivity to observe known pulsars with significantly improved
signal-to-noise ratios and will discover a large number of currently unknown
pulsars. We describe how FAST will contribute to PTA research and show that
jitter- and timing-noise will be the limiting noise processes for FAST data
sets. Jitter noise will limit the timing precision achievable over data spans
of a few years while timing noise will limit the precision achievable over many
years.
