Cold War, Experimental

SNCASO Trident – France’s Record Breaking Interceptor

The SNCASCO (Sud Ouest) Trident was developed in the 1950s in France as a high powered, interceptor aircraft as part of a wider scheme to revive the French aircraft manufacturing industry. France had wanted to catch up with other nations in restarting its air capabilities in the aftermath of the Second World War and also wanted a plane that could intercept and shoot down high altitude bombers.

The design process resulted in the Trident which featured a unique engine hybrid of rocket and jet power. Three different prototype units were submitted for testing.

As a test aircraft, it set a number of remarkable records, including achieving the fastest recorded climb. However, its development was also plagued with accidents, in part due to its volatile fuel mixture. Politics also played a role in the prototype project not progressing to the production stage and it was cancelled before any Trident could serve in the French Air Force.


The origins of the Trident began shortly after the end of the Second World War. Although French designers continued to work on ideas, the nation’s domestic aircraft production had struggled under the German occupation, with much of it being tightly regulated by occupying Nazi forces and some completed prototype projects even being confiscated by German officials.

During this time and in the pre-war period, a number of French aircraft manufacturers were merged into larger companies, with SNCASCO being formed from smaller weapons and aircraft companies in 1936 to provide defensive armament for the French Air Force.

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The end of the war also marked the beginning of tension between the Soviet Union and Western governments during the early stages of the Cold War. As surface to air and intercontinental missile technology was either in its infancy or not yet developed at the time, it was assumed nuclear warfare would be conducted in the way it had been during the atomic bombings of Japan by delivery of a nuclear warhead in a long range bomber to the target city.

Tupolev Tu-16 in flight.
The West expected nuclear attacks to come from strategic bombers, like this Soviet TU-16.

Military specialists and aircraft manufacturers focused their defensive ideas on high powered and fast interceptor planes that could be scrambled at a moment’s notice and rapidly climb to shoot down an enemy bomber.

SNCASCO had drawn up provisional ideas for a fast interceptor plane in October 1948 and began to closely study the idea of a rocket powered aircraft. Around this time, the French Air Force also issued a specification call for a defensive interceptor aircraft powered by a rocket unit. It was hoped that the new plane would serve a duel purpose of reviving the French aircraft industry, as well as provide an updated system of aerial defense.

The way in which the new aircraft would be powered was met with some debate before the design process began. Although war-era aircraft such as the Messerschmitt Me 163 Komet had used a rocket propulsion system for incredible speed, French Air Force chiefs were against the idea of using a purely rocket powered aircraft and instead called for a hybrid jet and rocket system.

Messerschmitt Me 163B.
Germany’s Me 163 is still the only rocket-powered fighter to have entered service. It was fast, but could only sustain powered flight for less than ten minutes.

The specification call was updated and specified for a single seat, supersonic interceptor jet capable of climbing to 50,000 feet and reaching a Mach 1 speed. Much of the requirement was altered and focused on jet over pure rocket technology after France observed dogfights between jet fighters during the Korean War.


SNCASCO began to research and refine their prototype ideas in the late 1940s, focusing on producing a plane that could use a rocket motor to get it airborne after which auxiliary jet units would help to power the aircraft.

The rocket engine chosen for the project was lifted from the Matra M.04 missile. The fuel would consist of a mix of Furaline and nitric acid, which was more difficult and somewhat hazardous to produce in comparison to existing rocket fuel, but it was selected on the basis that nitric acid did not require ignition chemicals.

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As rocket power was relatively new to French aircraft companies, it was decided to test the Trident’s proposed engine in an existing plane. French engineers took a Sud-Ouest Espadon prototype interceptor and fitted it with the rocket engine.

SO.6020 Espadon.
The SNCASO SO.6020 Espadon. The Espadon was also designed as an interceptor, but was not a successful aircraft.

Ground tests were performed with the engine in March 1951. The Espadon testbed then completed its maiden flight in June 1952. The test trial was deemed a success as the Espadon became the first aircraft made in Europe to achieve Mach 1 during level flight.

In April 1951, the French Air Force officially requested two working prototypes of a new plane from SNCASCO which would be named the Trident.

SNCASCO designed the new plane to be as streamlined as possible. The nose was built to be long and slim, with the cockpit fitted in the aft of the nose. The cockpit itself was heavily framed and situated low in the airframe. The wings were thin, short and mid-mounted on the fuselage.

The first Trident.
The first Trident.

The auxiliary jet units were fitted on the wing tips while the rocket engine was mounted inside the fuselage itself. The jets were Turbomeca Gabizo models that were capable of producing up to 10.79 kN worth of thrust each. The rocket motor would be built by SEPR and would carry enough fuel for a few minutes of flight to get the plane into the air before the jets would kick in.

The overall finished prototype had a total wingspan of 26 feet and a weight of 12,000 pounds. The maximum projected speed was a blistering 1,061 miles per hour.


The first Trident prototype completed its maiden flight on the 2nd of March, 1953 although only under the power of its wingtip jets rather than the rocket, but initial results were deemed as promising.

It was first displayed to the public at the La Bourget air show of June that year and sparked curiosity with its futuristic looking shape.

The second prototype was sent for its first proving flight in September 1953 but was involved in a minor accident without injury to the pilot after its wing clipped a pole during takeoff and the test was subsequently cancelled.

After the initial setback, the Trident was sent for another flight in on the 4th of September, 1954. It was intended to test the entire powerplant, but the rocket motor broke down during a second flight which left the project grounded while a solution was sought.

The SNCASO SO.9000 on the ground.
The Trident’s wingtip engines required very strong wings.

The SNCASCO engineering team took the Trident back to the factory and assessed how to improve its performance. The decision was made to replace the Turbomeca Gabizo jets with Dassault MD30 units which were licensed produced versions of the Hawker-Siddeley Viper jets.

The modified Trident was resubmitted for a trial flight on the 17th of March, 1955 which was deemed a success and went without incident. In a second flight which took place the following month, the Trident again achieved Mach 1 using just the jet units before a full test took place with the rocket, boosting the aircraft to double the speed.

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Although the Trident had achieved its objectives, the decision was made to produce an improved Trident II prototype to demonstrate what a combat version of the plane would look like and to test how it could perform with added weaponry. The wings were thinned slightly while the airbrakes were updated to a more modern design. The cockpit was also modified and the undercarriage was strengthened.

The SNASCO Trident.
The SNASCO Trident in flight with its fuselage rocket engaged.

Proposed armament would consist of air-to-air missiles for use against enemy bombers while a radar unit was installed in the nose.

The modified Trident II was sent for its maiden flight on the 19th of July, 1955 with just the jets in operation before a successful rocket test took place in December that year. A third prototype with the Turbomeca jets reinstated took place in March 1956, and this was also deemed a success by test pilots and observing engineers.


Although the situation for the Trident appeared promising, a number of issues began to hobble any further development after the initial test flights.

SNCASCO disappeared in 1957 after it was merged into the Sud-Est aviation company to form Sud Aviation who elected to continue the Trident’s development where SNCASCO had left off.

However, in May 1957 the project suffered a setback when the first prototype exploded in midair while rehearsing for a flight display at the Paris airshow, killing the pilot. A post-crash investigation determined the Furaline and nitric acid had mixed and caused a deadly chain reaction in the aircraft’s fuel system. The third prototype was also damaged that year after being forced to make an emergency landing.

Despite the setback, the French Air Force placed an order for six production aircraft but the order was cancelled after budget cuts. In an effort to impress potential customers and win back support from the Air Force, Sud Aviation performed a record breaking test flight in 1958 achieving the fastest climb recorded in a jet aircraft.

Trident in museum.
The only surviving Trident on display at the Musée de l’Air et de l’Espace in Paris. Image by Roland Turner CC BY-SA 2.0.

However, as a public relations stunt it failed to make much of an impact on the French Air Force who (still seeking a French-produced aircraft) elected to go with the Dassault Mirage I fighter jet which was deemed simpler to build and maintain.

The unsold Trident airframes were dismantled for spare parts while the Trident II models continued to be used as research planes until their retirement in the late 1950s.

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The first Trident prototype was preserved and has been on public display at the Bourget Air Museum since 1956.


Crew: 4
Length: 41 ft 8 in (12.7 m)
Wingspan: 22 ft 11 in (7 m)
Max takeoff weight: 13,007 lb (5,900 kg)
Powerplant: 2 × Turbomeca Gabizo turbojet engines, 2,400 lbf each, and 1 x SEPR 631 rocket engine, 6,615 lbf
Maximum speed: 1,300 mph (2,100 km/h)
Service ceiling: 24,000 m (79,000 ft)