The airplane usually drops sonobuoys, a device to collect sounds ... said in another news conference on Sept. 24 that the Russian patrol aircraft is believed to usually be engaged in search ...

It did not enter service with the Russian Air Force until the early 2010s ... anti-submarine warfare systems, radio sonobuoy ...

A sonobuoy (a portmanteau of sonar and buoy) is a relatively small buoy - typically 13 cm (5 in) diameter and 91 cm (3 ft) long - expendable sonar system that is dropped/ejected from aircraft or ships ...