In 1942, following the surprise German invasion of the Soviet Motherland in June of 1941, no concept (except for retreat) was off the table for the defenders. Taking the fight to the enemy became the battlecry of 1942-1943 and one of the more unorthodox plans intended for the Red Army was the use of a "glider tank" capable of being airdropped directly into battle from a passing mothership. This became the short-lived Antonov A-40 which, eventually, proved itself an unsuccessful venture.
Oleg Antonov designed the concept in which biplane wings, tailbooms, and tail surfaces were affixed to a lightweight tracked combat tank. The Soviets experimented with several of these airborne ideas in the 1930s and early 1940s - including more conventional glider drops and parachute-dropped tanks and tankettes - and these examples would be carried aloft by Soviet bombers modified as mothership platforms. The glider tank was devised as a solution in which the tank could be brought onto, or very near, the battlefront with the crew already inside the vehicle and ready-to-fight. The thinking was that numbers of these attackers could help to overwhelm unsuspecting enemy positions, giving the Soviets the advantage on their way to victory.
The vehicle-of-choice became the T-60 Light Tank (described in detail elsewhere on this site). This track-and-wheel combat system had been around since 1941 and was available in relatively good numbers (total production eventually reached nearly 6,300 units before war's end in 1945). Its compact dimensions (4m x 2.3m x 1.75m) and manageable weight of 5,800 kilograms made it an ideal candidate for the desperate Soviet Army. Additionally, the crew commitment for the small vehicle was just two personnel. Armament was modest with a 20mm gun serving as main armament while a 7.62mm coaxial machine gun supplied the necessary anti-infantry protection.
Around this starting point was developed an over-under biplane wing configuration utilizing N-type struts and applicable support cabling. A cradle allowed the T-60 tank to be nestled into the framework. From the trailing edges of the lower wing element emerged twin tailbooms and each of these held a single vertical fin for the needed stability/controlling in the air. A common horizontal tailplane joined the two tail sections together. Since the tank served as the "fuselage" of the aircraft, no true undercarriage was to be fitted - instead, the running gear of the tank served as the ground contact for the system.
The vehicle had an empty weight of 4,420lb with a Maximum Take-Off Weight (MTOW) of 17,205lb. Its listed overall length reached 39.6 feet. while the wingspan reached 59 feet.
Most, if not all, of the work on the T-60 glider tank was had in 1942 - by which point the system was designated as the Antonov A-40 but also eventually recognized as the "A-40T" and the "KT" in sources. A Tupolev TB-3 four-engined heavy bomber was to serve the project during its active testing phase. However, during the maiden flight held on September 2nd, 1942, the mothership was forced to drop its tank payload due to its sheer weight and generated drag (this despite the tank lacking some of the necessary combat components such as its full ammunition and fuel load). The tank was glided to the surface under control by its driver and managed to survive the precarious fall. This ended the An-40 venture as more conventional weapon systems were relied on instead going forward - and these instruments helping to bring the Third Reich sufficiently to defeat before the middle of 1945.
The An-40 was therefore something of a success and a failure for its short time aloft. The Soviet Air Force lacked a more powerful heavy bomber component to help see the program through and the glider tank concept appeared more-and-more novel with each passing month of the war. Despite this failed initiative, the Red Army continued work in the field during the post-World War 2 period and ended up generating a family of successful lightweight air-droppable tanks complete with an amphibious capability to boot. These systems have developments such as the An-40 to thank for their existence in the Soviet-Russian ranks.