DEFA cannon

The DEFA cannon (Direction des Études et Fabrications d'Armement) is a family of widely used French-made aircraft revolver cannons firing the standard 30 mm caliber NATO rounds.

Design history
The initial DEFA 551 was developed in the late 1940s. It was based on the German Mauser MG 213C, an experimental revolver cannon developed for the Luftwaffe. The MG 213 never reached production, but inspired the DEFA, the very similar British ADEN cannon, and the smaller American M39 cannon. As the DEFA 552 it entered production in 1954. In 1968 an upgraded version, Canon 550-F3, was developed, entering production in 1971 as the DEFA 553. The new version provided a new feed system, nitro-chrome plated steel barrel, forged drum casing, and improved electrical reliability.

Overview
The DEFA 553 is a gas-operated five-chamber revolver cannon using pyrotechnic cocking and electrical ignition. It fires a range of 30 mm ammunition in various types, and is capable of continuous fire or of 0.5-second or 1-second bursts.

The 553 was superseded by the DEFA 554, which incorporates a number of detail improvements. The DEFA 554 uses three, rather than two, of the chambers for reloading, increasing rate of fire. Barrel life and mechanical reliability are improved, and an electrical control unit now allows the pilot to select two rates of fire: 1,800 rounds per minute for air-to-air use or 1,200 rounds per minute for air-to-ground attacks. The 554 also provides three pyrotechnic cartridges rather than one, allowing the pilot to cock the weapon only after take-off while still having two cartridges to recock in flight.

Deployment
The DEFA 550 series was the standard cannon armament of all gun-armed French fighters from 1954 until the advent of the Dassault Rafale in the 1980s. A pair of these weapons, with 125–135 rounds per gun, is standard fit on the Dassault MD 450 Ouragan, Dassault Mystere, Mirage III/V, Dassault Étendard and Dassault Super Étendard, Sud Aviation Vautour, Mirage F1, French SEPECAT Jaguars, and the Mirage 2000 series. It was also used on the Israeli A-4E/F/H/N Skyhawk, IAI Nesher, IAI Kfir, and IAI Lavi, the Italian Aeritalia G91Y and Aermacchi MB-326K, the Indonesian A-4, and the South African Atlas Cheetah and Impala Mk.II. Various gun pod installations are available from CASA, Dassault Aviation, and Matra.

The DEFA 550 is very similar to the British ADEN cannon, and can use the same ammunition.

The DEFA 550 series has now given way to the GIAT 30 series used on the Rafale, although it is likely to remain in widespread use for many years to come.