  We compute second order transport coefficients of the dilute Fermi gas at
unitarity. The calculation is based on kinetic theory and the Boltzmann
equation at second order in the Knudsen expansion. The second order transport
coefficients describe the shear stress relaxation time, non-linear terms in the
strain-stress relation, and non-linear couplings between vorticity and strain.
An exact calculation in the dilute limit gives $\tau_R=\eta/P$, where $\tau_R$
is the shear stress relaxation time, $\eta$ is the shear viscosity, and $P$ is
pressure. This relation is identical to the result obtained using the
Bhatnagar-Gross-Krook (BGK) approximation to the collision term, but other
transport coefficients are sensitive to the exact collision integral.
