On a clear winter night, the jetliner begins a normal descent for landing. The descent profile is loaded into the flight management computer. Air traffic control (ATC) asks the crew, “Airport and traffic in sight?” Visibility seems assured. “Cleared for the visual to Runway 26, follow company traffic 5 miles ahead,” the controller directs. The first officer responds, “Cleared for the visual; we will follow company.” As long as they monitor the speed and do not overrun the company flight, this will be routine.
As expected, the altimeter smoothly unwinds and the crew comments on the clearness of the desert sky. Suddenly … where did the runway go? It was there a moment ago. “CAUTION TERRAIN,” the synthetic voice calls out. Terrain? The crew is certain their airplane is well above the ground. This must be a nuisance alert. “TERRAIN AHEAD, PULL UP!” Quickly the captain disengages the autopilot, increases thrust and begins to climb. Only then do both pilots realize how…
