How many operational defects are listed for NVG units?

The correct answer, which states that there are four operational defects listed for NVG units, is based on the standard operational procedures and evaluation criteria for Night Vision Goggles. These defects highlight critical performance issues that can affect the functionality and reliability of NVG systems in operational settings.

Understanding these specific defects is essential for users to be able to identify problems during pre-operations checks and to ensure that the NVGs are working effectively before they are deployed in the field. Each defect typically relates to key performance metrics or physical conditions that may compromise vision quality, such as image distortion, light leaks, or focus issues. Awareness of these defects allows operators to maintain the devices properly, conduct timely maintenance, and enhance overall mission effectiveness during nighttime operations.

While there are other potential issues related to user mishandling or environmental factors, the focus on these four operational defects is crucial for ensuring the NVG systems meet required performance standards.