Oerlikon GDF

The Oerlikon GDF or Oerlikon 35 mm twin cannon is a towed anti-aircraft gun made by Oerlikon Contraves (renamed as "Rheinmetall Air Defence AG" following the merger with Rheinmetall in 2009). The system was originally designated as 2 ZLA/353 ML but this was later changed to GDF-001. It was developed in the late 1950s and is used by around 30 countries.
Design and development.
The system uses twin autocannons, firing 35×228mm NATO-standard ammunition. It was originally designated 353 MK and is now designated as the KD series. The same KD series 35mm cannons are used in the Leopard 1 based Gepard and Type 74 tank based Type 87 SPAAG and Marksman self-propelled anti-aircraft guns (SPAAG). The system could be paired with the off-gun (remote) "Super Fledermaus" fire control radar, which in the late 1970s was upgraded to the "Skyguard" system. The weapons was aimed either directly, by way of an advanced sighting system, or automatically, by locking onto the target with radar. Early models carried 112 rounds ready to fire, and an additional 126 stored on the chassis as reloads. Later versions with automated reloading carry 280 rounds total. A typical engagement burst is 28 rounds.
In 1980 an upgraded model, the GDF-002 was produced, which featured an improved sight, and the ability to be directed by an off-gun digital control system. A few years later a third version of the system was being produced, the GDF-003, which was broadly similar to the GDF-002, but included some enhancements like self-lubricating weapons and integrated protective covers.
In 1985 a further upgraded model was produced, the GDF-005, which was introduced, featuring the "Gunking" 3D computer-controlled sight with an integrated laser range-finder and digital control system. The GDF-005 also introduced an automated ammunition-handling system, which eliminated the need for the two reloaders, reducing the crew from 3 to 1.
The guns are usually transported by a 5-tonne 6×6 truck.
KD series cannons.
Development of the KD series cannon began around 1952 soon after Oerlikon calculated that 35 mm was the optimum calibre for an anti-aircraft gun. The KD series cannons were a design adapted from the post-war 20 mm KAA 204 Gk cannon. Several designs were developed, including a water-cooled design, designated Mk 352, which was tested by the U.S. Navy.
The final design was the Mk 323, which was developed in two variants, a belt-fed version the KDA, and a linkless version the KDC, fed by seven-round clips. Both designs are gas-operated, with a propped-lock locking system.
Super Fledermaus.
The Super Fledermaus fire control system was designed and built by the then separate Contraves company. It consists of a four-wheeled towed trailer with an E/F band pulse doppler search radar with a range of around 15 km and a pulse doppler tracking radar operating in the J band, also with a range of 15 km. It was also used as the fire control system on the Gepard SPAAG.
Skyguard.
The Skyguard system is contained within a towed trailer, mounted on the roof of which is a pulse doppler search radar, a pulse doppler tracking radar and a co-axial television camera. The trailer also houses the crew of two and a small petrol generator. Skyguard is an all-weather air defense system for the control of aircraft at low altitude and at low and medium altitude range up to 3,000 m. The maximum effective distance is given as 4,000 m. The system takes the air surveillance, target acquisition, calculation of the derivative-action values and the control of two Oerlikon 35 mm anti-aircraft guns. Skyguard is served by four people.
It was created by Oerlikon-Buehrle. The weapon was introduced in the 1960s in the Swiss Army and got updates in 1975, 1995 and 2010. They are still in use. It had replaced the system Contraves Super Fledermaus in the Swiss Air Force. The Skyguard radar system was used in the German Air Force for surveillance of low-altitude flight zones. The radar unit is readied quickly through the use of hydraulic systems for antenna erection and leveling after deployment. A typical fire unit using the Skyguard consists of two twin 35 mm gun platforms with a single Skyguard fire control radar.
Skyguard systems can also incorporate an optional SAM module based on the GDF's mount and radar system but with the guns replaced by four missile canisters. It can be armed with either Aspide or RIM-7 Sea Sparrow missiles. In Greek service the Skyguard system with RIM-7M is known as the VELOS.