For a predetermined reaction time T3, for example 10 seconds, the LOOK-AHEAD distance (LAD) in nautical-miles for a terrain advisory signal can be determined-simply by multiplying the speed of the aircraft (V) by the total time TTOTAL as shown in equation (8) LAD = V * ( 0.0000278 + 2 * 0.000252854 * V ) + fixed ??? ??? distance * K , ( 8 ) where K is a constant, for example 0.