OVERVIEW: The PLAB‑250 is an unguided, free-falling aerial depth charge developed in the Soviet Union. It is designed to penetrate the water surface and detonate underwater against submarines.

DETAILS: PLAB stands for “Perekhodyashchaya Lodom Antisubmarinaya Bomba” (naval anti-submarine aerial bomb). The PLAB‑250‑120 variant weighs approximately 120 kg, measures about 1.5 m in length with a 240 mm diameter, and features a truncated ogival nose and anti-skip assembly to ensure clean water entry. It includes a steel body with a front braking ring and stabilizing fins for controlled descent. Internally, it houses a TNT booster and TGAF‑5M (TNT/RDX/aluminum) main charge, with both proximity and hydrostatic fuzes for detonation at depth.

FUNCTION: This bomb is dropped from ASW aircraft or helicopters following sonar or magnetic anomaly detection. It sinks to the preset depth (up to ~300 m) before detonating to damage or destroy submerged submarines.

NOTE:
IOC: Cold War era (exact date unspecified)
Operators: Soviet Union / Russia
Platforms: ASW helicopters such as Ka‑25 and Ka‑28 

SOURCE:
METIS (Fenix Insight): Plab‑250‑120 anti‑submarine aerial bomb ; CAT‑UXO: Plab‑250‑120 aircraft bomb ; Polish Hyperbaric Medicine & Tech Society: Field test on PLAB‑250‑120 ; CMANO‑DB: PLAB‑250 aerial depth charge ; Naval‑Technology: Ka‑25/Ka‑28 ASW helicopter armament config.