Željava aircraft cavern

Entrance to the aircraft cavern

The Željava aircraft cavern on the Bosnian - Croatian border near Bihać was the largest military aircraft cavern in Europe.

history

West of Bihać , near the village of Željava and at the foot of the Plješevica ridge , Europe's largest aircraft cavern was built between 1957 and 1970. Known as Klek or Objekat 505 , the complex cost the Yugoslav state around 6 billion dollars to complete . It held up to 80 MiG-21 combat aircraft, 110 pilots and 1,400 air force soldiers . The construction should withstand a nuclear attack with an explosive force of 20 to 30 kilotons. To protect the facility, a garrison with 5000 soldiers was built outside the cavern and was used until the outbreak of the Yugoslav Wars.

With the withdrawal of the Yugoslav People's Army from Bosnia in 1991, the caverns and slopes with a total of 56 tons of explosives were made unusable. Some areas inside are contaminated with PCB . Parts of the slopes and the outdoor area are still heavily mined.

elements

Outdoor facilities and slopes

In front of the mountain, five runways and taxiways to the four tunnels were created. Each of the three main runways is long enough to allow a MiG-21 to take off with a full load. The other two are intended as alternative slopes.

Command center

A command center was integrated north of the mountain .

Radar center

On the ridge of the 1650 m high " Gola Plješevica " there is a radar control center, also built into the mountain. Only the dome of the British Marconi S-613 search radar can be seen from the radar center . The radar control center has a storage room with four radar controller workstations, a separate room with the same radar controller workstations, an entrance protected by a reinforced door and six offices for meteorologists, flight preparation and radar operators. The radar control center is connected to the cavern 121 m below by a lift. With the S-600 radar system, consisting of 3D search radar and an altitude measuring radar, aircraft could ideally be recorded 400 km deep in the Italian, Austrian and Hungarian airspace. In this way, six aircraft could be tracked at the same time and intercepted by interceptors.

Control tower and staff rooms

In the middle of tunnel number four there is an access tunnel to a cylindrical room. Connected to this are five tunnels for evaluating the reconnaissance images, ELINT, operations control center, parachute pack and the squadron room. In addition to toilet facilities, there was an elevator that went 30 m up to the war control tower. Workplaces with radio equipment were located behind a 68 mm thick armored steel plate, and behind that there was a storage room with several radar monitoring workplaces.

Tunnel

The front and rear tunnels could be closed hydraulically with approx. 30 cm thick reinforced concrete-reinforced armored gates ABC-safe. The recess on the bottom through which the armored door was pushed was mechanically closed with movable steel plates so that the combat aircraft could roll over it. The panels were gently guided into the gap by a quarter-circle spur at the front of the armored door. The pre-tunnels were used to protect against NBC weapons and direct hits from precision bombs . Their pressure energy should be directed around the corner and evaporate at the end of the tunnel in an enlarged chamber and not be able to penetrate into the inner area of the cavern. The armored doors only be an inverted T-shaped opening free, whereby exclusively combat aircraft with a single vertical stabilizer (eg. MiG-21, Orao , Super Galeb ) could pass.

Fliegerstollen

The three tunnels (aviator galleries), which were reached after driving through, served as storage and maintenance halls. Each of them was oval, 20 m wide, 8 m high and between 350 and 500 m long. Two MiG-21s could stand next to each other in the tunnel. This means there is enough space for a tanker truck and personnel to pass next to a parked fighter aircraft. Electric tugs were used to drag the aircraft one by one in and then outside again to preparation areas before deployment. There the engines were started with the help of launch devices and the combat aircraft were able to take off from there directly on the runway. These facilities allowed operation with up to 80 MiG-21s kept ready for operation in the cavern. After a successful mission, the combat aircraft parked the engines on the staging plate in front of the cavern. There they were attached to aircraft tugs with electric motors by means of tow bars and pulled into the flying tunnel. The tugs were operated electrically to prevent any explosions of the escaping fuel in the tunnels. In the allocated parking spaces in the tunnel, the fighter planes were subjected to a simple intermediate flight check, refueled with kerosene from an airfield tanker and ammunitioned.

Support rooms

Inside the cavern there was enough space for four fully equipped MiG-21PF squadrons in the 3.5 km long tunnel. 110 pilots and air force troops were quartered there. The important rooms were provided with a total of 56 armored bunker doors. In various side knobs and niches were two diesel - generators for 1000 and 625 kVA, three squadron command stands, air compressors installed and air conditioning, a situation center, a canteen for 1,000 people, an infirmary and a developing chamber for wet images of MiG-21R reconnaissance aircraft. Water was taken from an underground river and distributed to the individual wet cells. Repairs were carried out in the maintenance tunnel No. 2 (in Serbian: Vazduhoplovno Technička Radionica) using the adequate equipment and spare parts.

ventilation

In order to be able to operate in the event of war, the whole complex had to be self-sufficient with breathing air. Seven air conditioning units were distributed over the various sections in order to achieve the necessary air flow. The air was sucked in through seven triangular intake ports camouflaged against air reconnaissance. In the climatic chambers, the air was first cleaned of any contamination by air filters and then heated to 18 ° with the air conditioning system. The used air was pumped outside through the ventilation system with positive pressure.

Aviator ammunition and kerosene storage

Next to a large ammunition depot for machine gun ammunition , air-to-air missiles and unguided bomb were five cylindrical fuel tanks for 500,000 liters of kerosene present. These supplies were able to ensure the restricted flight operations of 60 MiG-21s for two months. There were also tunnels to an ammunition depot 5 km away and underground fuel lines to a fuel store 20 km away.

NBC protection

The approximately 120 m long maintenance tunnel 2 was mainly used as a repair workshop. In the event of an incident, it should have been used as a decontamination tunnel in order not to contaminate further rooms with contaminated aircraft returning from operations. In the decontamination tunnel, around four aircraft could be decontaminated simultaneously with high-pressure water nozzles. The tunnel could be sealed off from the others with ABC-safe armored gates. After the decontamination , the fighter planes were able to roll into the air tunnels assigned to them. Large compressors were installed along with seven air conditioners. This generated overpressure in 13 lockable chambers of the complex against penetrating chemical warfare agents .

Deployed relays

Jagdgeschwader 117 ( lovačko-avijacijski puk , LAP for short) consisting of the following four squadrons:

3 fighter squadrons (124th, 125th fighter squadron and parts of that part of the 129th squadron from Pula for training flights ) with MiG-21PF ( lovačko-avijacijski eskadrila , LAE for short)

323rd Reconnaissance Squadron ( izviđačko-avijacijska eskadrila , IAE for short) with MiG-21R

Thus, the facility was occupied with four squadrons, whose task was the interception hunt and tactical reconnaissance.

Used aircraft types

Mikojan-Gurewitsch MiG-21F-13 ("Fishbed-C") interceptor (internal designation L-12)
Mikojan-Gurewitsch MiG-21PFM ("Fishbed-F") interceptor (internal designation L-14)
Mikojan-Gurewitsch MiG-21R ("Fishbed-H") reconnaissance aircraft (internal designation L-14i)
Mikojan-Gurewitsch MiG-21bis ("Fishbed-N") fighter-bomber (internal designation L-17)
Mikojan-Gurewitsch MiG-21US ("Mongol-B") two-seater for retraining from Jastreb to the MiG-21 (internal designation NL-14)