Investigation Summary
The Zodiac departed the Aero Club park at St. Cloud shortly before 2:00 p.m. on April 17, 1913. The flight was intended as a military exercise but was quickly complicated by strong westerly winds that pushed the balloon toward the eastern suburbs of Paris. Observers noted the crew frantically throwing out ballast near Fontenay-sous-Bois as the balloon lost altitude. The basket (car) first struck a chimney, which tilted the craft violently. Although it initially cleared this obstacle, the balloon remained at a dangerously low altitude, striking the side of a house and entangling in telegraph wires. The sequence culminated in a mid-air explosion, the cause of which was attributed to the volatile nature of the lifting gas and the structural damage sustained during the multiple ground collisions. The basket detached or fell following the blast, resulting in the immediate death of three occupants, while the remaining two succumbed to their injuries later that day.
Final Conclusions
The accident was caused by a loss of altitude control in high wind conditions, leading to multiple collisions with ground structures (a chimney, a house, and telegraph wires). These impacts likely compromised the envelope or gas valves, resulting in a fatal mid-air explosion and the subsequent fall of the car.
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Lifting Gas
The balloon used 'ordinary gas' (likely coal gas), which was flammable and susceptible to explosion if ignited following a structural breach.
Ballast System
The crew attempted to regain altitude by discarding ballast, a standard procedure that proved insufficient to clear ground obstacles in the high winds.
Interesting Facts
- 01The balloon was inflated with 'ordinary gas' rather than hydrogen or helium.
- 02Three aeronauts were killed instantly upon impact with the ground.
- 03The accident occurred during a period of strong westerly winds over the Paris region.
- 04The victims included three officers, one sergeant, and one civilian pilot.