How It Works

The current turbulence mode function in weather radars relies on analyzing the measurement processed from the radar returns.  The measurement, known as the “second moment”, is the measure of the second spectral moment estimate from the weather radar signal processor providing a reflectivity-weighted variance of the radial velocities.  The overall result is a measure of the shear or turbulence within the resolution volume.  If the second moment value is greater than a defined threshold value, a region of magenta is shown on the display to indicate an area of potential turbulence.  The problem with this technique is that the turbulence metric does not differentiate between aircraft types or various configurations – a Boeing 737 would display the same magenta picture as an Airbus A380 when in fact these aircraft would react much differently to the turbulence.

AeroTech’s E-Turb Hazard Prediction Algorithm, when implemented as software in Predictive Wind Shear radar systems, scales the radar second moment based on the aircraft’s current configuration (type, weight, altitude, speed, etc.) and calculates real-time estimates of predicted g-load.  These predicted g-loads are then provided to the radar display processor and can be translated, using various thresholds, onto the display as multiple levels of turbulence, scaled to the aircraft’s configuration and flight conditions.  From these indications the aircrew can easily assess the impact that turbulence will have on their aircraft.

Examples

The following figures show some examples of an E-Turb Radar display that can be produced using the predicted g-load output from the AeroTech Hazard Prediction Algorithm and established thresholds for the levels of turbulence to be displayed. The examples are taken from actual recordings of the E-Turb radar during the NASA Turbulence Prediction and Warning System (TPAWS) program In-Service Evaluation with Rockwell Collins and Delta Air Lines.  Somewhat different from the current turbulence mode magenta display is Rockwell Collins’ display of two-levels of turbulence hazard: speckled magenta representing a region of light turbulence and solid magenta representing a region of moderate or greater turbulence.  The green, yellow, and red regions are the standard display of reflectivity measured by the airborne weather radar.  In the examples, the dotted line represents the actual flight path of the aircraft through the region.