Mach probe characteristics are evaluated by using a directional Langmuir probe (DLP) in a fast flowing plasma produced by a magneto-plasma-dynamic arcjet (MPDA). The obtained data are compared with Hutchinson's simulation results which are calculated using a particle-in-cell (PIC) code in an unmagnetized plasma [I.H. Hutchinson, Plasma Phys. Control. Fusion, 44 (2002) 1953]. The experimentally obtained data are in good agreement with the simulation results in the wide range of M-i (0.4 < M-i < 1.7). Two types of the Mach probe, where the probe tips are facing to up-down directions and para-perp ones, are compared with model formulas and the simulation results. Good agreements are obtained among these data and calibration factors to determine the Mach number are evaluated. (c) 2005 Elsevier B.V. All rights reserved.