Context : B-type supergiants represent an important phase in the evolution of massive stars .
Reliable estimates of their stellar and wind parameters , however , are scarce , especially at mid and late spectral subtypes .

Aims : We apply the NLTE atmosphere code FASTWIND to perform a spectroscopic study of a small sample of Galactic B-supergiants from B0 to B9 .
By means of the resulting data and incorporating additional datasets from alternative studies , we investigate the properties of OB-supergiants and compare our findings with theoretical predictions .

Methods : Stellar and wind parameters of our sample stars are determined by line profile fitting , based on synthetic profiles , a Fourier technique to investigate the individual contributions of stellar rotation and “ macro-turbulence ” and an adequate approach to determine the Si abundances in parallel with micro-turbulent velocities .

Results : Due to the combined effects of line- and wind-blanketing , the temperature scale of Galactic B-supergiants needs to be revised downward , by 10 to 20 % , the latter value being appropriate for stronger winds .
Compared to theoretical predictions , the wind properties of OB-supergiants indicate a number of discrepancies .
In fair accordance with recent results , our sample indicates a gradual decrease in v _ { \infty } over the bi-stability region , where the limits of this region are located at lower T _ { eff } than those predicted .
Introducing a distance-independent quantity Q ^ { \prime } related to wind-strength , we show that this quantity is a well defined , monotonically increasing function of T _ { eff } outside this region . Inside and from hot to cool , \dot { M } changes by a factor ( in between 0.4 and 2.5 ) which is much smaller than the predicted factor of 5 .

Conclusions : The decrease in v _ { \infty } over the bi-stability region is not over-compensated by an increase of \dot { M } , as frequently argued , provided that wind-clumping properties on both sides of this region do not differ substantially .