Definition
A localized separation in the wood grain of a wooden aircraft spar or other wood structural member, forming a small cavity that contains, or once contained, resin (pitch). Pitch pockets are a recognized defect evaluated during inspection of wooden aircraft structures and may be cause for rejection depending on size, location, and number.
Plain English
A small pocket inside a piece of wood where the grain has split apart and filled with sticky tree resin. In aircraft wood, this is treated as a flaw that has to be checked because it can weaken the part.
Context Anchor
Seen in propeller maintenance, especially when discussing controllable-pitch or constant-speed propellers.
Derivation
Pitch is the sticky resin that seeps from softwood trees like spruce and pine. A pocket is a small enclosed space. Together the term simply describes a hidden pocket of resin trapped within the wood.
Why Pilots Care
Can cause imbalance, vibration, or blade failure if left unrepaired.
Intuition Check
Do not read “pocket” as a storage space. Here it means a shaped recess or receiving point in the propeller blade assembly.
Example Sentence 1
During the annual inspection of the wooden wing spar, the mechanic flagged a pitch pocket near the root and consulted the airworthiness limits before signing it off.
Example Sentence 2
Small pitch pockets were filled and re-glued before the propeller was returned to service.