in which the AAD can save somebody's life. For this reason, many countries (such as Denmark) require AADs for all skydivers and jumps. In countries where AADs are not legally mandated (such as the US), many drop zones still require all jumpers to use AADs. Others require all student jumpers to use them even if licensed jumpers are not. Possible issues regarding the contained explosives HADOPAD radar actuator High-Altitude Delayed-Opening Parachute Actuating Device, also called HADOPAD, was a radar actuator used as a component in a delayed opening aerial-delivery system. The system was developed by the Harry Diamond Laboratories in the mid-1960s, which later became a part of Army Research Laboratory. The device, based on radar principles, opened a main recovery parachute at either of two preset heights (1,000 or 1,700 ft.) above the ground. The air delivery system consisted of the cargo package, two parachutes (drogue and main), and the radar actuator. The radar was designed to determine when the cargo reached a preset altitude, generating a firing signal which actuated a mechanism releasing the main parachute at that time. See also Adrian Nicholas – a noted skydiver who died from an AAD activation (by reaching the speeds required to activate his AAD under a high performance canopy) References External links Airtec - Cypres and Cypres 2 FXC Corporation - FXC 12000 and Astra Advanced Aerospace Designs - Vigil ParachuteHistory.com - Hi Tek 8000 ParachuteHistory.com - Sentinel Parachuting