  We present the analysis of hot spot brightness in light curves of the
eclipsing dwarf nova IY Ursae Majoris during its normal outburst in March 2013
and in quiescence in April 2012 and in October 2015. Examination of four
reconstructed light curves of the hot spot eclipses showed directly that the
brightness of the hot spot changed significantly only during the outburst. The
brightness of the hot spot, before and after the outburst, was on the same
level. Hereby, based on the behaviour of the hot spot, IY UMa during its normal
outburst follows the disk-instability model.
