  TREND50 is a radio detection setup of 50 self-triggered antennas working in
the 50-100MHz frequency range and deployed in a radio-quiet valley of the
Tianshan mountains (China). TREND50 achieved its goal: the autonomous
radiodetection and identification of air showers. Thanks to a dedicated offine
selection algorithm, 564 air shower candidates were indeed selected out of
$7\cdot10^8$ transient radio signals recorded during the 314 live days of data
taken during the first two years of operation of this setup (2011 and 2012).
This event rate, as well as the distribution of the candidate directions of
arrival, is consistent with what is expected from cosmic-ray-induced air
showers according to simulations, assuming an additional $\sim$20%
contamination of the final sample by background events. This result is obtained
at the cost of a reduced air shower detection efficiency, estimated to be
$\sim$3%. This low efficiency is mostly due to the large amount of dead time of
the setup. This result paves the way for the GRANDProto35 experiment, the first
stage of the GRAND project.
