# Rotary-Wing Night Flight Day or night, vision is the primary sense providing crewmembers with awareness of aircraft position or SA. Eyes can rapidly identify and interpret cues in daylight. During darkness, visual acuity decreases proportionally as the level of illumination decreases. NVDs improve the capability of the human eye to see at night, but still suffer from limitations as conditions deteriorate. This chapter covers NVDs and provides a general discussion of night vision and techniques for completing missions safely --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://229.gitbook.io/229-hub/knowledge/army-aviation-fundamentals/rotary-wing-night-flight.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.