  In real applications, drops always impact on solid walls with various
inclinations. For the oblique impact of a Leidenfrost drop, which has a vapor
layer under its bottom surface to prevent its direct contact with the
superheated substrate, the drop can nearly frictionlessly slide along the
substrate accompanied by the spreading and the retracting. To individually
study these processes, we experimentally observe ethanol drops impact on
superheated inclined substrates using high-speed imaging from two different
views synchronously. We first study the dynamic Leidenfrost temperature, which
mainly depends on the normal Weber number ${We}_\perp $. Then the substrate
temperature is set to be high enough to study the Leidenfrost drop behaviors.
During the spreading process, drops always keep uniform. And the maximum
spreading factor $D_m/D_0$ follows a power-law dependence on the large normal
Weber number ${We}_\perp $ as $D_m/D_0 = \sqrt{We_\perp /12+2}$ for $We_\perp
\geq 30$. During the retracting process, drops with low impact velocities
become non-uniform due to the gravity effect. For the sliding process, the
residence time of all studied drops is nearly a constant, which is not affected
by the inclination and $We$ number. The frictionless vapor layer results in the
dimensionless sliding distance $L/D_0$ follows a power-law dependence on the
parallel Weber number $We_\parallel$ as $L/D_0 \propto We_\parallel^{1/2}$.
Without direct contact with the substrate, the behaviors of drops can be
separately determined by ${We}_\perp $ and $We_\parallel$. When the impact
velocity is too high, the drop fragments into many tiny droplets, which is
called the splashing phenomenon. The critical splashing criterion is found to
be $We_\perp ^*\simeq$ 120 or $K_\perp = We_\perp Re_\perp^{1/2} \simeq$ 5300
in the current parameter regime.
