Aircraft cavern

Aircraft cavern, a calque of the German word Flugzeugkaverne, is an underground hangar amongst others used by the Swiss Air Force.

Historical

A Mirage IIIRS in front of an aircraft cavern in Buochs airfield, Switzerland

During World War II the neutral Swiss military airfields were for the first time equipped with simple semi round concrete U-43 type shelters protecting the aircraft parked underneath. After World war II, starting in 1947, these open objects became even better protected with steel doors thus creating the U-68 type shelter.

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, defence their neutrality towards the superpowers. In the 1940s the Swiss army already built so-called retablierstollen (re-equipping caves) at some airfields. These retablierstollen consisted of 100m long straight tunnels excavated in the rocks making it possible to store and eventually re-arm small Swiss fighter aircraft like the then used Messerschmitt BF 109. The dimensions of these tunnels are comparable with an autobahn tunnel.

The airfields chosen were Alpnach, Buochs, Meiringen, St.Stephan and Saanen, all located in the mountains with a lot of rocks in the near vicinity of the runway so that the aircraft could be out of sight within minutes after touchdown.

In the early 1950s the first larger excavations in the rocks took place creating more space in the existing caves. The space of these excavations was now used to service the aircraft and to execute some minor repairs. The first larger constructions inside the rocks were at the airfields: Ambri, Alpnach, Buochs, Meiringen, Raron and Turtmann becoming operational from 1951-1954.

As the Swiss air force modernized and changed its aircraft during the 1960s the excavations, now called cavernes, were further modernized and extended. Underground command & communication posts were constructed together with ammunition and fuel storage facilities, generator and technical rooms to keep the facility running and of course also personnel quarters.

From the past until today the cavernes have been used to shelter and service the following aircraft types:

BAe Hawk aircraft and Alouette III helicopters have only temporarily been stored in cavernes after being withdrawn from service before being sold to third parties.

Design and construction

A Swiss caverne has space to hold 22 F-5 Tiger aircraft. The outside door usually consists of composite material, steel with a wooden core. The door is defended by personnel in a hardened bunker covering it with machineguns, making the outside door small arms and hand grenade proof. Past the door is an S shaped tunnel making it nearly impossible to fire on the main blast doors. The blast doors are made of concrete reinforced steel and as long as they are closed, the aircraft parking area remains fully CBRN protected.

There are two or more tunnels. The first tunnel provides space for 11 aircraft and is equipped to handle major overhauls such as engine replacements. The aircraft are moved by lifting them by cranes. Once they are on the crane, they can be moved through the whole length of the tunnel. There is a linking tunnel to the weapon storage area (WSA) which is extra protected by a sealed door. In case of fire the weapon storage may be filled with inert Halon gas to prevent fire and explosions. The WSA not only holds the ammo needed to re-arm the aircraft (missiles and gun shells) but also small arms ammo for all military working in the caverne.

On the opposite side of the WSA is the Command facility holding the workshops to service all aircraft systems, the communications cell, briefing room, kitchen, food & water storage, mess, personnel quarters and no-break generators to maintain electrical power under all circumstances. water for the personnel. The Command facility is also protected by hermetically sealed doors when working under CBRN conditions.

Next to the Command tunnel is another tunnel with the same dimensions as the first one. This one is also capable to hold 11 aircraft.

Fuel storage is located behind all tunnels allowing the caverne to sustain 22 aircraft for about 10 days without re-supplying of electricity, fuel, ammunition etc. from the outside world.

Meiringen Air Base viewed from the Rothorn

Operational use

The Swiss air force operates from Alpnach Air Base, Dübendorf Air Base, Militärflugplatz Emmen, Meiringen air base, Locarno Airport, Payerne Air Base and Sion Airport.

Meiringen is the only airfield with fully operational cavernes. The caverne at Meiringen was extended and refurbished for about 120 million Swiss Francs to comply to the needs of the current Swiss airforce F/A-18 fighters. Because of the weight of these aircraft hanging them in overhead cranes would only be possible against enormous costs so that was no real option. Instead an extra tunnel had to be built as there was no need for overhead cranes anymore. The tunnels are connected by some linking tunnels and extra dispersals were added on the opposite walls of each tunnel making it possible to operate 22 F/A-18s. The aircraft are able to roll in and out at the same time without the need of moving parked aircraft. A linking tunnel constructed directly before the main blast doors makes it possible to refuel and rearm an aircraft immediately after its mission without opening the main blast doors. A very important issue when a unit is working under CBRN conditions. The Meiringen caverne ammo storage has an extra tunnel to the outside.

The former cavernes at Alpnach, Ambri, Raron and Turtmann have been deactivated and closed. The caverne at Buochs Airport has been mothballed and it is estimated that the facility could be reactivated to operate F-5’s within two months.

Origin

Originally, the plan for the Aircraft cavern started its life as a design for "cavern airfields". High costs and technical difficulties prevented these from realisation. The idea of using roads as runways was later part of the design demands for the Swiss motorway network.[1][2]

Other countries

Other countries that have built aircraft shelters inside the mountains include Albania, Bosnia and Herzegovina, Croatia, The People's Republic of China, Italy, Kosovo, Montenegro, Norway, North Korea and Sweden.

See also

References

  1. ↑ (German) Flugplätze stehen unter Schutz bernerzeitung.ch
  2. ↑ (German) FLUGPLATZKOMMANDO MEIRINGEN

Sources and references

External links

External images
Aircraft cavern
M113 in Cavern Turtmann
F-5E in Cavern
Hawker Hunter in Cavern
Patrouille Suisse F-5E in Cavern
F/A-18 and F-5 Cavern Meiringen
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