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A cavern airfield is a cavern-like aircraft hangar (German "Kavernenflugplatz") was a project of the Swiss Air Force at the beginning of the Cold War for use / start of combat aircraft from in a protected mountain air base.

History
Shortly after the World War II and the beginning of the Cold War and a possible escalation between the nuclear superpowers of the East West blocks, the Swiss Air Force began to develop concepts to, as in a case of conflict, defense their neutrality towards the superpowers. A permanent occupation of Switzerland was feared but, more likely Switzerland could be pulled in as a walk  through marshland in the fighting. It was clear that air superiority is important and military airfields are a first targeted in a conflict. Simultaneously with the introduction of jet aircraft DH-100 "Vampire" and DH-112 "Venom" the Swiss Air Force began with the planning of this project and designed it for this aircraft types.

Operation
It was planned that the entrance opening is located at the height of the mountain valley. Through this entrance, the aircraft should enter the facility. The aircraft should either use wartime landing strips (road sections, of the later built Gotthard motorway) for landing. also an air traffic tower should be build next to this landing strip to coordinate the landings and maneuvering of the aircraft on the ground. But also the transportation by military trucks or railroad was planned (the aircraft must be disassembled for transport in the main components: fuselage, wings and tail). In the mountain at the height of the valley floor is the command tunnel, with the communication and command equipment, assembly- maintenance line, briefing, debriefing rooms, sanitary, kitchen, living and sleeping quarters, spare parts warehouse workshops, accommodations, fuel tanks, weapons storage. Diesel engines for the power generator. The pre-flight preparation should be done here to. Then the aircraft are brought with a lift inside the mountain to the level of the runway. At this level, in the mountain, are the lift drive unit, water storage, loading and ventilation systems, the runway with its blastdoor and the launch tower housed. The ventilation systems would have to make, by suction intake ducts, for sufficient air / oxygen and immediate withdrawal of the exhaust gases. The water tanks served not only to supply the facility with water but to also create a water mist extinguishing with enough pressure in case of fire. For starting the main wheels and the nose wheel are held by three sunken U-profiles on course so this would have prevented the aircraft from  colliding with  the walls of the runway during the takeoff run in the tunnel.

Problems
Various points took the project in question. Firstly, the high costs that would be caused by this massive tunnel system who would have been necessary in the mountain. During the excavation in the valley is not a technical problem, the creation of the lift shafts in these quantities and also the construction of the runway inside the mountain in height and the opening in the rock face hold technical risks. The start of the engines and the acceleration inside a "tunnel" with all the risk of fire, false start, hitting the tunnel wall and finally wind gusts, crosswinds when leaving the opening in the rock wall, seemed the project as too dangerous. Also became apparent that the next generation of fighter aircraft which would come in service by the Swiss Air Force (Hawker Hunter, P-16) were greater in size as the Vampires and Venoms. This would have made this system unusable or causing massive enlargement of the dimensions and the associated costs.

Geography
The wartime landing strip was planet  south of Schattdorf   in Schachen,  the  "Schwerverkehrszentrum (Heavy traffic center) or on the E35 motorway between Schattdorf and the motel "My Stop", the entrance of the facility would have been approximately at the location where today the federal company "RUAG Environment" is.  The whole  facility been housed inside the mountain Schilt. Been the starting opening would been built in the rock wall above Rinacht, which would have permitted a safe flight corridor over the "Schiltwald" (Schilt forrest).

Derivation
Due to the above-mentioned problems, it never came to build this facility. Nevertheless, it was groundbreaking for the less elaborate Aircraft cavern of the Swiss Air Force who were built at various military airfields later. Also the idea of  using streets  as wartime runways was considered a few years later when building the Swiss motorway network. A piece of land owned by the government, that was provided for this facility is nowadays still in Federal ownership and the location of the RUAG Division of Recycling.