In 1961, appeared the ASU-85 self-propelled gun, designed specifically for the Soviet airborne forces. Initially was called SU-85, but the name was changed not to be confused with the tank destroyer that fought in WWII. A 85mm D-70 gun was mounted on a PT-76 light tank chassis in a “casemate” type mounting instead of a rotating turret. This assembly had the disadvantage of having a limited traverse of only 12 degrees on each side. It could be transported by MiL Mi-6 “Hook” and MiL Mi-10 “Harke” transport helicopters and by An-12 “Cub” tactical transport aircraft, which allowed them to be deployed almost in any theater of operations. They could be launched in flight providing multiple parachutes and a retro-rockets braking system that stopped their fall few meters before touching the ground. They were used by the Soviet , Polish and East German Armies, and currently it is only used by the Vietnam Army, which recently modernized them.
ASU-85 gallery and more info