What happens during inadvertent de-calibration of instruments?

During inadvertent de-calibration of instruments, the most significant outcome is that instruments provide misleading information. This occurs because the calibration of instruments ensures they provide accurate readings based on specific reference standards. If instruments become de-calibrated, they may give indications that do not match the actual flight conditions, leading to potentially dangerous situations.

For example, if an airspeed indicator is de-calibrated, it might indicate a higher or lower speed than what the aircraft is actually experiencing. This can mislead pilots in critical phases of flight, such as takeoff, landing, or when maneuvering. Therefore, maintaining proper calibration of flight instruments is vital for situational awareness and safe aircraft operation.

The other choices do not accurately reflect the consequences of instrument de-calibration. Accurate readings (the first option) would not occur in this situation, nor is it limited to only digital instruments (the third option), as both analog and digital instruments can be affected. Additionally, de-calibration does not lead to improved instrument function (the fourth option). Proper instrument function relies on precise calibration, and once de-calibration occurs, the risk of inaccuracy increases.