Which item is described as permanent?

• A. Level 1 electric anti icing
• B. Main and Emergency Battery
• C. Probes and sensors (Permanent)
• D. Spring tab

Answer: (C)

In maintenance terms, permanent items are components designed to stay installed for a long time and aren’t treated as consumables or routine replacement parts. Probes and sensors fit this category because they are integral sensing devices mounted on the airframe to provide continuous data for the aircraft’s systems. They’re built to last across many flight hours and cycles, and when serviceability is checked, they’re not typical short-term replacements—you replace them as a unit only when they fail or during major overhauls, not on a routine basis.

The other options aren’t described as permanent because they’re items with finite lifespans or replaceable components: a Level 1 electric anti-icing system is a subsystem that can be serviced or replaced; the main and emergency battery has a defined life and is replaced; a spring tab is a movable control surface that wears or can be damaged and is replaced as needed.