If the instrument static pressure line disconnects inside a pressurized cabin, what will occur?

When the instrument static pressure line disconnects inside a pressurized cabin, the altimeter and airspeed indicator will both read low due to the nature of how these instruments function and rely on surrounding static pressure for their operation.

The altimeter measures altitude based on the difference between the static pressure outside the aircraft and a preset standard pressure. If the static source is disconnected, the altimeter no longer has accurate external pressure data. Inside a pressurized cabin, where the pressure is typically higher than that outside the aircraft, the altimeter will interpret the higher pressure as being at a lower altitude, resulting in it indicating a lower altitude than the actual one.

Similarly, the airspeed indicator works by measuring the dynamic pressure, which is a combination of static pressure and airspeed. A disconnection means that the airspeed indicator will also receive misleading static pressure information, leading it to display an indication that is lower than actual speeds. In essence, both instruments provide incorrect readings due to the unrepresentative pressure conditions caused by the disconnection of the static pressure line.

In summary, when the static line disconnects, both the altimeter and the airspeed indicator will yield low readings, reflecting the incorrect static pressure being sensed within the cabin as opposed to the