What causes the net to release from the stanchions in a BAK-15 when an aircraft engages the system?

The net releasing from the stanchions in a BAK-15 when an aircraft engages the system is primarily due to shear link devices. These devices are designed to respond during the aircraft's landing process. When the aircraft engages the arresting system, the force exerted can cause the shear links to break, which in turn allows the net to drop from its stanchions. This mechanism is crucial for ensuring a safe and effective engagement between the aircraft and the arresting system, allowing it to capture the aircraft and bring it to a stop. The function of the shear links is specifically tailored to work under the unique circumstances of a landing, making them an integral part of the system's reliability.