• Attitude (roll, pitch), relationship to terrain (altitude, closure rate acceleration)
• Terrain type (mountainous, rolling, etc.) and terrain trends (rising, falling)
• Validity/reliability of sensor inputs
• Response capabilities of pilot and aircraft.

Using this dynamic rate, the GPWS algorithm computes the following to determine a potential CFIT:

• The predicted altitude loss due to pilot/aircraft response time
• The predicted altitude loss due to roll recovery
• The predicted altitude loss during the actual recovery
• The predicted altitude loss due to the underlying terrain
• Aircraft Sensors

Cubic's flight testing and analysis proved that GPWS will work with sensors already existing on most aircraft. These sensors include:

• Radar altimeter
• Air data computer
• Altitude gyros
• Engine torque and rotor speed
• Aircraft discrete signals (i.e., Weight on Wheels and Landing Gear Position)

GPWS software is unique in that it does not rely on a single sensor input or data, but combines and filters several appropriate sensor inputs to derive the best possible CFIT prediction.

The GPWS algorithm also continually assesses the validity of input data to keep its computations accurate and free of incorrect or polluted data. For example, the algorithm places a limit on how long it will consider altitude inputs to be valid without the radar altimeter on line.

Future sensors, such as Forward Look and Map Systems are accommodated by the P3I desing of the GPWS avionics.

No False Alarms
Altitude-warning devices are not new in aviation. But they do have a troubled history in low-level, highly dynamic flight environments. The high incidence of false and "nuisance" alarms have rendered these systems as a "less than reliable" flying companion. Experience and research have proven that aircrews will turn off or ignore devices that prove unreliable and burdensome. For this reason, Cubic's GPWS was designed to eliminate false alarms.

Choose Your Implementation
Adaptable to all classes of rotary wing aircraft, GPWS can be installed as a 1/4-ATR (short) avionics package interfaced with discrete sensors, or via the MIL-STD-1553B data bus. It can also be embedded in computers already on-board.