Chapter 2


Safety considerations have led to the development of automatic activation devices and reserve static line systems. These devices allow for automatic deployment of the main or reserve parachutes in the event of an emergency.


Automatic activation devices (AADs) are devices which activate the parachute automatically. Modern systems combine a barometric sensor with a rate of descent sensor so that the system is fully automatic once turned on and calibrated. The activation may be by either pulling the ripcord pin(s) or cutting the locking loop(s), causing the pilot chute to release. Most older models use a mechanical or pyrotechnic pin pulling technique. Newer models use a pyrotechnic loop cutting design.

For many years, AADs were primarily used by the military and student parachutists. The designs were bulky, expensive, and, to a degree, inconsistent. The installations themselves were cumbersome and awkward. In the early 1990s a new generation of AADs became available. The CYbernetic Parachute RElease System (CYPRES®) uses modern parachute release technology. It is small, reliable, computer based, and uses a pyrotechnic loop cutter. It has an auto-off feature that turns the unit off after 14 hours of operation to conserve power. It also has the ability to calibrate the unit for operation at altitudes other than the calibrating ground level. Based on these concepts, other companies have developed similar systems and as a result, changed the approach to the design and use of AADs. Today, most sport parachutists use an AAD and some countries mandate their use by all parachutists.

The following describes the operation and installation requirements of the CYPRES® model AAD. Most other designs are compatible with the CYPRES® installation requirements.


The CYPRES® system is a barometrically controlled microprocessor that activates a pyrotechnic cutter that cuts the container locking loop. When calibrated to ground level, the barometric sensor activates the unit firing the cutter when the descending parachutist reaches an altitude of approximately 750 feet AGL and exceeds a rate of descent of 115 feet per second.

The CYPRES® consists of three parts: (1) the battery and processing unit, (2) the control unit, and (3) the cutter. [Figure 2-43] The processing unit is generally located in a stowage pouch installed in the reserve container of the parachute system. [Figure 2-44] The control unit is contained in a vinyl pocket located either under the pin protector flap or in the upper backpad area. [Figure 2-45]

The cutter(s) may be located at the base of the pilot chute or on a flap over the pilot chute. [Figure 2-46] Each parachute system has its own particular requirements, and it is imperative that the rigger have the appropriate manuals for installation.

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