Russian Forces have also trained with the An-26 as a bomber. One An-26 was involved in the Purulia Incident in 1995 in which arms were dropped in the Purulia district of West Bengal, India. The reason behind the drop is not disclosed to the public due to national security. Variants An-26 "Curl-A" : Twin-engine tactical transport aircraft. An-26-100 Convertible passenger/cargo aircraft modified from An-26 aircraft at the Kyiv plant from 1999. An-26 Nel'mo An arctic surveillance and reconnaissance aircraft retrofitted with Nel'mo equipment. An-26 Pogoda (Weather) Another aircraft for weather control duties, similar to the An-26 Tsiklon, with a simplified equipment test lab. An-26 Polyot (Flight) A single aircraft retrofitted for the purpose of research of unified air traffic control and monitoring system throughout the USSR, with a comprehensive navigation test lab including precision compasses and Doppler speed/shift sensors. An-26 Sfera (Sphere) A single production aircraft built as a laboratory for atmospheric research. An-26 Shtabnoy (Shtab: or Headquarters) some An-26s delivered to the Soviet and DDR air forces for use as staff transports/mobile command posts. (Life) A single mobile operating room, surgery and intensive care unit ('25 Blue', c/n5406), for the Ukrainian Air Force. An-26A A one-off assault transport prototype with higher performance due to removal of some military equipment. An-26ASLK (Avtomatizirovannaya sistema lyotnogo kontrolya – automated flight control and monitoring system) : A modern flight control and monitoring system equipped with automatic calibration and navigation systems. Recognizable by the distinctive pod low on the forward fuselage side. An-26B A civil cargo version equipped with roller gangsways which can be swung up against the cabin walls when not in use. It was also equipped with two ZMDB Progress (Ivchyenko) Al-24VT turboprop powerplants to deliver higher thrust. An-26B The prototype An-26B retrofitted as a mobile civilian emergency hospital. An-26B Tsiklon (Cyclone) A weather research/control and cloud-seeding aircraft for the Central Aerologic Laboratory. This aircraft was used for rain induction and protection using cloud-seeding chemicals dropped from slab-sided pods hung from pylons. An-26B-100 Convertible passenger/cargo aircraft modified from An-26B aircraft at the Kyiv plant from 1999. An-26BL Alternative designation for the An-26L. An-26BRL Alternative designation of the An-26RL Arctic surveillance and reconnaissance aircraft. An-26D (Dal'niy – long-range) An extended range version with extra fuel in wing tanks and additional external tanks attached to the airframe of the fuselage. One aircraft ('21 Yellow', c/n 13806) was retrofitted and delivered, but no further orders