SNCASO SO.9000 Trident — Archival Technical Documentation
Société Nationale de Constructions Aéronautiques du Sud-Ouest (SNCASO), France
Trident I & Trident II — Archival Collection, Early 1950s
The SNCASO SO.9000 Trident was one of the most radical interceptor concepts ever to reach flight testing. Conceived in the early 1950s to counter supersonic strategic threats, it combined wingtip-mounted turbojets with a liquid-fueled rocket motor in the rear fuselage — a mixed-power formula that pushed French experimental aviation to its absolute limits and ultimately cost the life of test pilot Charles Goujon in 1957.
This archival collection assembles two primary-source technical documents for the Trident I and Trident II programmes, covering aerodynamic configuration, propulsion systems, flight dynamics, cockpit systems, and the engineering solutions devised for one of the most dangerous aircraft ever built in France.
Aerodynamic Design & Structural Configuration
The SO.9000's aerodynamic profile was optimized explicitly for the transonic and supersonic regimes. The highly streamlined, bullet-shaped fuselage minimized cross-sectional wave drag. Wings were short, straight, and needle-thin — a low-aspect-ratio rectangular structure that minimized supersonic wave drag at the cost of poor lift-to-drag ratios at low speed. Conventional multi-part control surfaces were abandoned in favour of three all-moving slab tailplanes, operating collectively for pitch/yaw and differentially for roll — the only solution to high-speed control lock-up.
Propulsion Systems
Turbojet (Wingtip-Mounted): Two Dassault MD.30 “Viper” turbojets at wingtips — annular air intake, 7-stage axial compressor, annular combustion chamber (6 igniter + 12 start injectors), single-stage turbine, fixed-area ejection nozzle. Static ground thrust: 725 kg each. Ground start via cart (compressed air + electrical accumulators), two-phase sequence; in-flight re-ignition possible on onboard battery. Kerosene system: 2 forward tanks (660L) + 2 lateral tanks (90L) + collector/nourrice (85L). HP pump feeds both reactors via FAURE-HERRMANN counter and independent leading-edge solenoid isolation valves.
Rocket Motor — SEPR Group (Rear Fuselage): Propellants: Furaline (fuel) + pure nitric acid (oxidizer) — hypergolic, instantly igniting on contact, extremely toxic, volatile, and highly corrosive to the airframe. Staged fixed thrust: 3 stages of 1,500 kg / 3,000 kg / 4,500 kg via 3 × 1,500 kg combustion chambers. Gas generator (nitric acid + Furaline combustion, water/methanol injection cooled) drives turbine powering centrifugal feed pumps. Pilot operations minimized to a master electric switch and a start timer.
Hydraulic Systems
Hydraulic energy used for: landing gear retraction, servo-control jacks and compensators, braking, and cabin jettison push. Two electric pumps in parallel, pressurized reservoir, feeding four independent circuits: landing gear (+ servo-control emergency), servo-control normal, normal braking, emergency braking. Cabin jettison circuit is fully autonomous — fed by a dedicated accumulator pressurized on the ground; two cabin push jacks fitted with special scissors that sever all service lines connecting cabin to airframe at the moment of jettison.
Pneumatic Systems
Cabin Pressurisation (normal & emergency): Bleed air from both MD.30 Viper reactors via SRMCA pressure regulator. Schedule: 0–3,000 m = ambient; 3,000–6,250 m = fixed at 3,000 m equivalent; above 6,250 m = differential 0.250 kg/cm². Emergency supply: 3.3L bottle at 150 HPZ in forward nose, supplies cabin at Δp = 25 ps on reactor bleed failure or during cabin jettison descent. Secondary circuits feed cockpit seal inflation and anti-g valve.
Rocket Propellant Tank Pressurisation: Acid reservoir pressurized by 150 HPZ bottle in forward nose via pre-reducer and reducer. Furaline and water reservoirs pressurized by separate bottle in fuselage above wing. Pilot can dump acid reservoir rapidly (“vide-vite”) or progressively (“vidange lente”) via same forward nose bottle.
Servo-Stabilizer Valve: Dynamic pressure from pitot antenna transmitted to servo-stabilizer valve cylinder — piston linked to pitch command, applying speed-dependent load feel to pilot.
Electrical Systems
Two ANDZAR 40 Ah (19-cell) batteries. Battery 1 (forward, “servitudes battery”): powers reactors (LP/HP cocks, LP pump, fuel counter, tachometers, manometers, thermometers), fire detectors, hydraulic electro-pumps/gauges/warning lights, landing gear, intrados flaps, airbrakes, servo-control (roll gyro, friction dampers, compensator motors), windscreen de-icing, pitot heating, cabin pressure/oxygen, warning lights, navigation (gyro-compass, gyro-horizon), radio (VHF I, radio compass), and flight test instrumentation. Battery 2 (rear fuselage, “emergency battery”): backs up Battery 1 on failure; powers VHF II and all rocket circuit accessories in normal operation.
Handling, Stability & Flight Dynamics
Wingtip engine positioning created extreme yaw vulnerability — a single-sided flameout at high speed threatened an unrecoverable pinwheel spin. Early test flights without the active rocket required the full length of military runways to unstick from the tarmac. Conventional ailerons were entirely locked out during supersonic transitions, leaving the all-moving tail surfaces as the sole roll authority. Test pilot Jacques Guignard documented these severe anomalies in flight test reports that form part of the programme’s engineering record.
Engineering Bulletins & Programme History
The second Trident I prototype was lost on its maiden flight in 1953. The Trident II suffered a mid-air explosion in 1957, killing test pilot Charles Goujon. Engineering files detail a fully jettisonable nose capsule — the entire cockpit section designed to separate from the airframe at supersonic speeds, with hydraulic push jacks and scissors that sever all service lines on command. Despite setting multiple unofficial altitude and climb rate records, the programme was officially terminated in 1958 when the French Air Force selected the Dassault Mirage III.
Document Manifest — 2 Unique Documents
Document 1 — S.O. 9050-001 · Notice Pilote — Note Technique n° 2-0355 (Trident II)
Pilot’s Notes for the SO.9050-001 — 15 pages. Covers: general description (MD.30 Viper + SEPR 2-chamber rocket), hydraulic servitudes (landing gear, servo-controls, braking, airbrakes), pneumatic systems (cabin pressurisation, hydraulic reservoir pressurisation, rocket propellant tank pressurisation, acid dump circuits, servo-stabilizer valve), electrical systems (two ANDZAR batteries, full circuit breakdown), MD.30 Viper reactor description and start sequence, kerosene fuel circuit, SEPR 63 rocket system (Furaline + nitric acid, 2-stage thrust 1,500 + 2,000 kg, turbopump, pilot controls), and flight control system (irreversible hydraulic jacks, mixer unit, all-moving tail surfaces).
Document 2 — S.O. MDa/LM · Note Technique 5456 (Trident I — SO.9000)
Comprehensive systems description — 29 pages + 13 technical plates. Covers: general characteristics (3-chamber SEPR group, 2 × MD.30 Viper), hydraulic systems (4-circuit architecture, cabin jettison autonomous circuit), full pneumatic systems breakdown (cabin pressurisation normal/emergency/secondary, hydraulic reservoir pressurisation, rocket tank pressurisation, acid dump rapid/slow, servo-stabilizer valve), electrical systems (two ANDZAR 40 Ah batteries, complete circuit inventory), MD.30 Viper reactor description and two-phase start sequence, kerosene circuit (660L + 90L + 85L collector), SEPR rocket group (3-stage thrust 1,500/3,000/4,500 kg, 3 combustion chambers, gas generator turbopump). 13 technical plates covering general arrangement, fuel feed, hydraulic schematics (4 plates), cabin layout, instrument panels (left/right consoles, central panel), cabin conditioning, and radio installation.
This collection contains 2 unique documents — Cette collection contient 2 documents uniques.
⚠️ Regulatory Notice: Under FAA 14 CFR § 43.13 and EASA Part-M, any mechanic performing maintenance on an active aircraft must use current, manufacturer-approved revision-controlled data. This archival document does not satisfy that requirement.
This is an archival, static-copy edition fixed at its original publication date. Intended for historical reference, flight simulation, museum restoration, and educational use only. Not approved for active airworthiness maintenance under FAA 14 CFR § 43.13, EASA Part-M, or equivalent international regulations. Operators of active aircraft must use current, revision-controlled publications from the Type Certificate holder or an authorized distributor.
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