  We have performed a calculation of the scattering amplitude for the three
body system $\bar{K}NN$ assuming $\bar{K}$ scattering against a $NN$ cluster,
using the Fixed Center approximation to the Faddeev equations. The $\bar{K}N$
amplitudes, which we take from chiral unitary dynamics, govern the reaction and
we find a $\bar{K}NN$ amplitude that peaks around 40 MeV below the $\bar{K}NN$
threshold, with a width in $|T|^2$ of the order of 50 MeV for spin 0 and has
another peak around 27 MeV with similar width for spin 1. The results are in
line with those obtained using different methods but implementing chiral
dynamics. The simplicity of the approach allows one to see the important
ingredients responsible for the results. In particular we show the effects from
the reduction of the size of the $NN$ cluster due to the interaction with the
$\bar{K}$ and those from the explicit considiration of the $ \pi \Sigma N $
channel in the three body equations.
