What term describes the delay before an instrument needle reaches a stable indication?

The term that refers to the delay before an instrument needle reaches a stable indication is known as lag. This phenomenon occurs in various types of instruments where the response to changes in the measured parameter is not instantaneous. For instance, when an aircraft makes an abrupt change in attitude or speed, the corresponding instrument may take time to reflect these changes accurately due to the inertia of the needle or the damping characteristics of the system.

Understanding lag is crucial for pilots, especially during instrument flight, because it affects how quickly and accurately they can perceive and respond to changes in flight conditions. Acknowledging this delay helps in better situational awareness and can prevent misinterpretations that might lead to inappropriate responses during flight maneuvers.

Position error, response time, and calibration error describe different phenomena that affect instrument readings but do not specifically address the aspect of delayed needle movement. Position error pertains to discrepancies due to instrument placement. Response time refers to how quickly an instrument reacts to changes but is not as specific about the delay before achieving stability. Calibration error involves inaccuracies rooted in the instrument's calibration and operation but does not directly relate to the timing of the indication stabilization.