The Automatic Activation Device — AAD — is one of the most important safety innovations in the history of sport skydiving. It is a small electronic computer mounted in your rig that continuously monitors your altitude and descent rate, and if you are falling too fast below a preset altitude, it fires a mechanism that deploys your reserve parachute. It is not a substitute for proper skydiving procedures — you are still responsible for deploying your main canopy and cutting away if necessary — but it is a backup that has saved hundreds of lives that would otherwise have been lost to low-pull and unconsciousness scenarios.
How AADs Work: The Core Technology
An AAD contains a pressure sensor that continuously measures atmospheric pressure and converts this to an altitude reading using the standard barometric formula. It also measures the rate of change of pressure — your descent rate. By combining altitude and descent rate data, the AAD can determine whether you are in freefall at a normal rate, under a functioning canopy at a normal descent rate, or falling at an unsafe speed without a functioning canopy.
When the AAD detects that you are below its programmed altitude — typically 1,000 feet above ground level — and falling faster than a preset threshold — typically around 50 meters per second or 11,200 feet per minute — it fires a squib, an electrically ignited explosive charge. This charge cuts a closing loop and simultaneously activates the reserve parachute deployment system. The reserve canopy opens exactly as it would in a manual deployment.
The AAD's logic is designed to distinguish between normal canopy flight and a failure scenario. A functioning ram-air canopy descends at approximately 15 to 25 feet per second, while a human body in freefall descends at approximately 120 to 180 feet per second. The AAD's detection algorithm is tuned to this difference, and it fires when the descent rate exceeds the canopy threshold below the designated altitude.
The Two Major AAD Brands: CYPRES and Vigil
CYPRES, produced by Airtec in Germany, is the most widely used AAD in sport skydiving and has an extraordinary safety record. The CYPRES Expert model is the most common in recreational skydiving, while the CYPRES Competition model offers additional features for high-speed and high-altitude applications. CYPRES units are known for their reliability and the company's extensive support network.
Vigil, produced by Parasafety in France, is the second major AAD brand and offers comparable reliability to CYPRES with some different feature sets. The Vigil Evolution and Vigil Unlimited models serve different segments of the market, with the Unlimited designed for high-altitude, high-speed applications including BASE jumping and high-altitude formation skydiving.
Both brands have undergone continuous development over their histories, with each new model incorporating improved sensors, algorithms, and user interfaces. The choice between brands is largely a matter of personal preference and availability, with both being considered acceptable by USPA and drop zones worldwide.
AAD Installation and Configuration
An AAD must be properly installed in your rig by a qualified person — typically an rigger or the rig manufacturer — and must be configured for your specific jump profile. The critical configuration parameters include the activation altitude and the maximum descent rate threshold.
Standard recreational skydiving settings typically use an activation altitude of 1,000 feet AGL and a descent rate threshold that corresponds to freefall versus canopy flight. Some AADs allow separate configuration for student and experienced jumper modes, with the student mode firing at a higher altitude to provide an additional margin of safety for less experienced jumpers.
High-altitude skydiving requires specific AAD configuration to account for the different atmospheric conditions and the use of supplemental oxygen. The CYPRES Competition and Vigil Unlimited models are designed for these applications and include features specific to high-altitude operations.
Battery Life and Servicing Requirements
AADs are powered by batteries that must be replaced at specific intervals. This is not optional — a dead battery means a non-functional AAD. CYPRES requires battery replacement every two years or 500 jumps, whichever occurs first, and recommends returning the unit for full factory service every four years. Vigil has similar requirements with some variation by model.
The battery replacement procedure for most AAD models can be performed by the owner with a new battery kit from the manufacturer, but the battery replacement must be followed by a specific activation sequence and functional test. Many owners prefer to have the battery replaced by an authorized service center to ensure the procedure is completed correctly.
Between battery replacement intervals, the AAD performs self-diagnostic tests every time it is activated. Most models display a status indicator showing whether the unit is ready for jumping. If the display shows any error indication or if the status light is not green, the unit must be removed from service and returned to the manufacturer or authorized service center for evaluation.
The Limitations of AADs
An AAD is a backup system, not a primary deployment device. It does not replace the skydiver's responsibility to deploy their main canopy at the correct altitude, nor does it replace the cutaway procedures that handle main canopy malfunctions. An AAD that fires has already failed to prevent a dangerous situation — you have already descended too low without a functioning canopy.
AADs do not protect against all dangerous scenarios. A low pull where the skydiver manually deploys their main canopy but it malfunctions and they cut it away at 2,000 feet will not trigger the AAD because the descent rate while under a malfunctioning but still open canopy may be below the firing threshold. The AAD fires when you are falling freely at terminal velocity, not when you are under any canopy.
The AAD's barometric sensor can be affected by rapid pressure changes that occur during unusual flight attitudes, and it can be temporarily confused by the pressure signature of a large formation in freefall. These limitations are well understood and do not significantly affect the AAD's reliability in real-world scenarios, but they underscore that the AAD is not infallible and must not be treated as a substitute for proper skydiving procedures.