  L\'{e}vy walk is a practical model and has wide applications in various
fields. Here we focus on the effect of an external constant force on the
L\'{e}vy walk with the exponent of the power-law distributed flight time
$\alpha\in(0,2)$. We add the term $F\eta(s)$ ($\eta(s)$ is the L\'{e}vy noise)
on a subordinated Langevin system to characterize such a constant force, being
effective on the velocity process for all physical time after the
subordination. We clearly show the effect of the constant force $F$ on this
Langevin system and find this system is like the continuous limit of the
collision model. The first moments of velocity processes for these two models
are consistent. In particular, based on the velocity correlation function
derived from our subordinated Langevin equation, we investigate more
interesting statistical quantities, such as the ensemble- and time-averaged
mean squared displacements. Under the influence of constant force, the
diffusion of particles becomes faster. Finally, the super-ballistic diffusion
and the non-ergodic behavior are verified by the simulations with different
$\alpha$.
