CASPIAN SEA MONSTER

4 min readOct 2, 2023

The Caspian Sea Monster, known by its Russian acronym KM (Korabl Market), was an experimental ground effect vehicle that emerged in the 1960s under the development of the Central Hydrofoil Design Bureau in the Soviet Union. This vehicle was initially operational in 1966 and underwent continuous testing by the Soviet Navy until 1980, when it met its demise by crashing into the Caspian Sea. From 1966 to 1988, the KM was the most substantial and heaviest aircraft globally. Its unexpected discovery by the United States and subsequent attempts to discern its purpose became a notable espionage episode during the Cold War.

Design and Development

The KM was an experimental aircraft conceived between 1964 and 1966 when the Soviet Union explored ground-effect vehicles. Like aeroplanes, these vehicles utilize ground effects to fly just a few meters above surfaces, primarily over bodies of water like the Caspian Sea. It was crafted at the Central Hydrofoil Design Bureau under the leadership of the chief designer, Rostislav Alexeyev, and the lead engineer, V. Efimov, with manufacturing taking place at the Red Sormovo plant in Gorky (now Nizhny Novgorod). When completed in 1966, the KM became the most significant aircraft globally, featuring a wingspan of 37.6 meters, a length of 92 meters, and a maximum take-off weight of 544 metric tonnes. Its design allowed it to fly at an altitude of 5–10 meters, using ground effect.

The KM was equipped with ten Dobrynin RD-7 turbojets, with two mounted in the tail and eight in the canard position. After take-off, the eight canard-mounted engines would shut off, leaving the two tail-mounted engines to propel the craft during regular travel. Although technically classified as an aircraft, its low-flying altitude rendered it virtually invisible to many radar systems. It was primarily utilized by the Soviet Navy but operated by test pilots from the Soviet Air Forces. The KM was officially categorized as a marine vessel, and a tradition of breaking a bottle of champagne against its nose was observed before its inaugural flight.

Operational History

In June 1966, the KM, after its construction, was transported along the Volga River to the testing grounds near Kaspiysk on the Caspian Sea. This operation was conducted covertly, with the aircraft covered in camouflage and travelling exclusively at night. Its maiden flight took place on October 16, 1966, an exceptional event since most Soviet aircraft designers did not personally pilot their creations. The KM’s testing revealed an optimal cruising speed of 430 km/h and a maximum operational speed of 500 km/h, although some sources suggest speeds of up to 740 km/h.

Initially perceived as a promising asset for military and rescue missions, the KM’s intricate design led to numerous challenges, causing progress to decelerate. Alexeyev shifted his focus to other ekranoplan projects, and the KM was subjected to tests on the Caspian Sea for 15 years until a pilot error resulted in its destruction in 1980. While no lives were lost, the KM was heavily damaged, and no efforts were made to salvage it. It sank a week later and remained submerged, as it was deemed too weighty to recover. There were no intentions to construct a second KM. Nevertheless, the KM served as the foundation for the Lun-class ekranoplan developed by the Central Hydrofoil Design Bureau in the 1980s, with one example, the MD-160, entering service with the Soviet Navy and later the Russian Navy before decommissioning in the late 1990s.

The KM retained the title of the largest aircraft globally and remains the second-largest aircraft ever built, surpassed only by the Antonov An-225 Mriya, which first flew in 1988, eight years after the KM’s demise.