  Small-scale magnetic flux ropes (SFRs), in the solar wind, have been studied
for decades. Statistical analysis utilizing various in situ spacecraft
measurements is the main observational approach which helps investigate the
generation and evolution of these small-scale structures. Based on the
Grad-Shafranov (GS) reconstruction technique, we use the automated detection
algorithm to build the databases of these small-scale structures via various
spacecraft measurements at different heliocentric distances. We present the SFR
properties including the magnetic field and plasma parameters at different
radial distances from the sun near the ecliptic plane. It is found that the
event occurrence rate is still in the order of a few hundreds per month, the
duration and scale size distributions follow power laws, and the flux rope axis
orientations are approximately centered around the local Parker spiral
directions. In general, most SFR properties exhibit radial decays. In addition,
with various databases established, we derive scaling laws for the changes of
average field magnitude, event counts, and SFR scale sizes, with respect to the
radial distances, ranging from $\sim$ 0.3 au for Helios to $\sim$ 7 au for the
Voyager spacecraft. The implications of our results for comparisons with the
relevant theoretical works and for the application to the Parker Solar Probe
(PSP) mission are discussed.
