Method and associated system for adjusting sink rate alert envelope for special landing zones

Method and corresponding system for improving sink rate alerting for rotary wing aircraft (12). In one example, the system (10) includes a radio altimeter (28) that produces an altitude value, a processor (20) that is in signal communication with the user interface device and the radio altimeter. The processor receives an altitude value, a position value for the aircraft and landing zone information. The processor determines if the aircraft is on an approach to land at a landing zone that is raised above surrounding terrain based on the received position value and landing zone information. The processor receives sink rate information for the aircraft and generates a sink rate alert based on the received sink rate information and the aircraft altitude value if the sink rate information is greater than a sink rate value adjusted according to the landing zone information. An output device (22, 24, 34) outputs the generated sink rate alert. The landing zone information includes an altitude value.