Definition
In aircraft maintenance, the gradual deterioration of a material, component, or system over time due to chemical, electrical, mechanical, or environmental causes. Common forms include corrosion of metals, breakdown of insulation, weakening of adhesives, loss of charge in batteries, and degradation of rubber or composite parts.
Plain English
Slow loss of strength, condition, or performance in a part or material as time passes.
Context Anchor
Seen during inspections of wooden aircraft parts, such as wing structures, ribs, spars, and plywood skin.
Derivation
From Latin 'decadere,' meaning 'to fall down' or 'fall away.' The sense of something slowly falling out of good condition carries directly into the maintenance meaning: a part is gradually falling away from its original sound state.
Why Pilots Care
Unchecked decay can lead to structural failure in flight, making regular inspections critical for aircraft with wood components.
Analogy
Decay in aircraft wood is like rot in a fence board: the outside may still look mostly normal, but the material can be soft, weak, and unable to carry the load it was meant to carry.
Intuition Check
Decay does not just mean age, wear, or fading. In this airframe context, it means fungal rot that damages wood and can weaken the structure.
Example Sentence 1
The technician found signs of decay in the battery cell, with reduced voltage and visible corrosion at the terminals.
Example Sentence 2
Aircraft with fabric-covered wooden structures require checks for decay especially in humid climates.