Plain English Meaning
The different ways something can break, and what each kind of break looks like to the pilot. Knowing the failure modes means knowing what the instruments will show when a particular part stops working correctly.
Full Definition
The specific ways in which a system or component can fail, including how each failure manifests, what indications the pilot will see, and how the failure affects related systems. In the pitot-static context, failure modes describe what happens when the pitot tube, static port, or associated lines become blocked, leak, or are damaged, and how the airspeed indicator, altimeter, and vertical speed indicator respond to each type of failure.
Context Anchor
Seen when studying pitot-static system problems, especially when how , , and or can become .