Model Variants (Including Prototypes)
TsKB-26 - Prototype Model Designation
TsKB-30 - Developmental Model
DB-3 - Base Military Designation
DB-3B - Production Model Designation; appeared in 1937; early models featured M-85 765 horsepower engines with later models fitted with M-86 960 horsepower engines; armament consisted of just three guns of 7.62mm caliber.
DB-3F - Appearing in 1940; featured a elongated nose assembly and improved armor protection; system re-designated to more familiar naming of "IL-4".
IL-4 - Re-designation of DB-3F system by 1940; armament caliber increased to all 12.7mm types (UBT); some metal construction replaced with less-costly wood.