opening sequence of a ram-air parachute
The opening sequence of a ram-air parachute is a complex process that unfolds in several well-defined stages. Each phase is crucial to ensure a controlled and safe deployment, minimizing stress on both the parachutist and the equipment. Here’s a detailed breakdown:
1. Pilot chute deployment
The first step is deploying the pilot chute, a small auxiliary parachute that serves as an extraction device. This can be primary (for the main parachute) or secondary (for the reserve parachute). The pilot chute is either manually deployed by the parachutist or automatically (as in a static line system or drogue chute deployment).
2. pod deployment
Once the pilot chute inflates, it generates aerodynamic drag sufficient to extract the freebag (in the case of the reserve parachute) or the deployment bag (for the main parachute). This phase gradually removes the parachute from its folded position inside the container.
3. Line stretch
After the bag is extracted, the suspension lines begin to fully extend. This phase is critical because if the extension is too abrupt, it can cause excessive opening shock, increasing the risk of malfunctions. The proper tensioning of the lines ensures that the canopy deploys with the correct orientation.
4. Canopy inflation (central cell expansion)
Once the lines are fully stretched, the canopy starts to inflate. Initially, the central cell fills with air first, creating a partial structure that facilitates a controlled deployment of the remaining cells.
5. Progressive inflation of lateral cells
As air continues to enter the cells through the front openings, the remaining cells gradually inflate from the center outward. This progressive inflation helps reduce the risk of an explosive opening and allows for a smoother transition to stable flight.
6. Initial stall and full pressurization
Once all the cells are fully inflated, the parachute briefly enters a stall phase, where the vertical speed is minimized, and the slider goes down helping reduce the opening shock, but the canopy is not yet in a fully flyable configuration. The internal pressurization of the canopy is crucial to maintaining its structural rigidity and responsiveness to control inputs.
7. Brake release and transition to controlled flight
The parachute initially deploys with partially applied brakes to prevent an overly aggressive opening. Once the canopy is stable and fully pressurized, the parachutist can release the brakes, allowing the parachute to achieve normal forward speed and transition to a fully maneuverable flight mode.
Factors Affecting the Opening
The opening sequence of a ram-air parachute can vary depending on several factors, including:
Descent speed at the moment of deployment (higher speed results in a more forceful opening)
Pilot chute size and deployment bag design (permeability, size, and drag affect the extraction sequence)
Packing method (incorrect packing can lead to asymmetric or delayed openings)
Atmospheric conditions (relative wind and turbulence can influence canopy deployment)
Last but not least, the skydiver position, in fact, everyone should follow the standard opening procedure, with their belly towards the ground avoiding any horizontal movements
The entire process, from pilot chute deployment to controlled flight, typically takes between 2 and 5 seconds, but this can vary depending on the type of canopy and deployment conditions.
If you’d like to explore any specific phase in more detail or analyze potential opening issues, let me know!
