Mach Number

from 0.15 (for low-speed, high-lift testing)
through 0.7 – 0.9 (the typical cruising speed of today’s transport aircraft)
up to 1.35 (for aircraft or space vehicles in low supersonic conditions)

Temperature from 313 K (= + 40°C) down to 110 K (= – 163°C)

Total Pressure from 1.15 bar to 4.5 bar

The test section size and the temperature and pressure ranges represent the best combination of parameters to meet the requirements from the aerospace industry.

The operating ranges for each Mach number can be summarized into an overall ETW performance envelope expressed as Reynolds number against Mach number. Pure Reynolds-number, or pure airloads variations at constant Mach number can be achieved by adjusting total pressure and temperature accordingly. Testing at ambient temperature allows data comparison to conventional low- or high-speed tunnels.

With full-span aircraft models a Reynolds number of about 50 million can be reached, and when a larger ceiling mounted half (semi-span) model is used then Reynolds numbers of up to 85 million can be achieved. These Reynolds numbers are based on the mean aerodynamic cord of the respective wing.

The upper Reynolds number limit is obtained at the minimum temperature and at the first reach of either the maximum pressure or the maximum drive power.