What pressure does a technician use when conducting the static system leakage check required by aviation regulations?

When conducting the static system leakage check, technicians utilize negative pressure. This process involves creating a vacuum in the aircraft's static system to analyze the integrity of the system's components and connections. By applying negative pressure, the technician can observe whether the system holds the vacuum or if there are leaks. If the pressure drops, it indicates a potential leak, which can impact the accuracy of the altimeter and other altitude-referenced instruments.

Using negative pressure for the leakage check is essential because it simulates conditions that instruments experience during flight, allowing for a more accurate assessment of the static system’s performance. The other types of pressure, such as positive or absolute pressure, are not typically relevant for this specific testing method, as they do not provide the necessary insights into the leakage characteristics of the static system.