Which statement is not true concerning sonobuoys?

Sonobuoys are specialized devices used primarily in anti-submarine warfare for detecting underwater sounds. The statement that they are nonexpendable is not true. Sonobuoys are designed to be expendable, meaning they are intended for single-use. Once deployed, they gather data for a specific operation and are typically not recovered, which aligns with their purpose in providing real-time underwater detection without the need for retrieval.

In contrast, the other statements accurately reflect the characteristics and functionalities of sonobuoys. They are deployed from aircraft, enabling them to cover vast areas for underwater acoustics. Additionally, their main purpose is indeed underwater detection, making them crucial tools in maritime operations. The expendable nature of sonobuoys allows for rapid deployment over targeted areas, enhancing their effectiveness in gathering valuable acoustic data during naval missions.