Which instrument is also known as the vertical speed indicator (VSI)?

The vertical speed indicator (VSI) is commonly referred to as the rate-of-climb indicator, as it measures the rate at which an aircraft is ascending or descending in feet per minute. This instrument provides pilots with critical information regarding the vertical performance of the aircraft, enabling them to maintain safe altitudes during flight operations. By indicating whether the aircraft is climbing or descending, the rate-of-climb indicator plays a crucial role in flight safety and navigation.

The other instruments listed do not serve the same purpose as the VSI. The altimeter measures the altitude of the aircraft based on atmospheric pressure but does not provide real-time information about the rate of ascent or descent. The angle of attack sensor measures the angle between the aircraft's wing and the oncoming air, which helps assess the likelihood of a stall but is not directly related to vertical speed. The total air temperature probe measures the temperature of the air outside the aircraft, which is essential for various performance calculations but does not provide vertical speed data.