In a sideslip, does the airspeed indicator over-read or under-read?

In a sideslip, the airspeed indicator's reading can be affected by the position of the static port in relation to the airflow. If the static port is positioned on the fuselage, the indicator may experience pressure changes due to the angle of attack created during a sideslip. This can result in the instrument reading an inaccurate airspeed, potentially leading to an over-read or under-read condition depending on factors such as the specific aircraft design and how the static port is influenced by the airflow.

If the static port is located away from the airflow during a sideslip, it may experience lower static pressure, causing the airspeed indicator to show an under-read. Conversely, if the port is capturing more static pressure due to the airflow being altered by the sideslip, you may see an over-read.

The airspeed reading in a sideslip is therefore not a straightforward issue, and its accuracy and the resulting reading can depend on how the aircraft's design impacts the airflow around the static source. This is why the correct answer highlights the importance of the static port location in determining whether the airspeed reading changes in a sideslip.