What type of heat detection system is used in the pneumatic system, and how does it detect a bleed leak?

• A. Wire-type sensors running near and parallel to the pneumatic lines, using electrical current and resistance to detect leaks.
• B. Fiber-optic sensors integrated in hoses, measuring light scattering.
• C. Infrared sensors at manifold outlets, measuring temperature.
• D. Acoustic sensors listening for hiss from leaks.

Answer: (A)

The system uses a heated wire sensor that runs near the pneumatic lines. It keeps the wire at a constant elevated temperature by passing current through it. If a bleed leak occurs, the escaping air flows past the wire and cools it, causing a change in temperature. Because the wire’s resistance depends on temperature, this cooling changes the electrical resistance (or the voltage/current needed to maintain temperature), and the monitoring electronics interpret that change as a leak along the line. This heat-based, convective-cooling principle makes the sensor directly responsive to small leaks in the pneumatic system. Other options rely on optical, acoustic, or point-temperature measurements, which don’t fit the described heat-detection approach.