In maintenance status symbols, which indicates an unsafe or unserviceable condition?

• A. Red dash
• B. Red diagonal
• C. Blue Bark
• D. Red X

Answer: (D)

In maintenance status symbols, color and shape are used to quickly signal how an item can be used. The red X is the clear, unambiguous signal that something is unsafe or unserviceable and must be taken out of service and sent for repair or requalification. It tells everyone: do not use this part or component until the issue is resolved.

The other marks aren’t the standard indicator of an unsafe or unserviceable condition. A red dash and a red diagonal do not carry that definitive prohibition in most systems, and Blue Bark isn’t a recognized maintenance symbol at all—it's a distractor. So the red X is the best answer because it directly conveys the required action: remove from service until repaired.