Which of the following describes how a squib is fired?

• A. A manual switch in the cockpit directly fires the squib.
• B. A hydraulic signal fires the squib.
• C. An electric current from the fire extinguishing circuit fires the squib.
• D. The squib is self-igniting upon system discharge.

Answer: (C)

The squib is an electrically initiated device. When the fire suppression system commands discharge, an electric current from the fire-extinguishing circuit powers the squib, causing it to fire and release the agent or open the release mechanism. This setup keeps actuation safe and reliable, controlled from the cockpit or automatic fire detection, rather than relying on manual or hydraulic actuation. A manual cockpit switch firing the squib directly would bypass safety interlocks, which is not how these systems are designed. Hydraulic signals aren’t used to trigger squibs, and the squib isn’t self-igniting upon system discharge—it needs that electrical pulse to initiate.