  Galactic black-hole X-ray binaries (BHBs) emit a compact, optically thick,
mildly relativistic radio jet when they are in the hard and hard-intermediate
states. In these states, BHBs exhibit a correlation between the time lag of
hard photons with respect to softer ones and the photon index of the power law
component that characterizes the X-ray spectral continuum above $\sim$ 10 keV.
The correlation, however, shows large scatter. Our objective is to investigate
the role that the inclination of the system plays on the correlation between
the time lag and the photon index. We find that the correlation between the
time lag and the photon index is tight in low-inclination systems and becomes
weaker in high-inclination systems. The amplitude of the lags is also larger at
low and intermediate inclination angles than at high inclination. Our jet model
that reproduces the process of Comptonization in an extended jet can account
for the observations remarkably well.
