  We present the results of a photometric monitoring campaign of three well
studied FU Orionis systems (FU Orionis, V1057 Cygni and V1515 Cygni) undertaken
at Maidanak Observatory between 1981 and 2003. When combined with photometric
data in the literature, this database provides a valuable resource for
searching for short timescale variability - both periodic and aperiodic - as
well as for studying the secular evolution of these systems. In the case of
V1057 Cyg (which is the system exhibiting the largest changes in brightness
since it went into outburst) we compare the photometric data with time
dependent models. We show that prior to the end of the `plateau' stage in 1996,
the evolution of V1057 Cyg in the $V-(B-V)$ colour-magnitude diagram is well
represented by disc instability models in which the outburst is triggered by
some agent - such as an orbiting planet - in the inner disc. Following the end
of the plateau phase in 1996, the dimming and irregular variations are
consistent with occultation of the source by a variable dust screen, which has
previously been interpreted in terms of dust condensation events in the
observed disc wind. Here we instead suggest that this effect results from the
interaction between the wind and an infalling dusty envelope, the existence of
this envelope having been previously invoked in order to explain the mid
infrared emissio of FU Orionis systems. We discuss how this model may explain
some of the photometric and spectroscopic characteristics of FU Orionis systems
in general.
