Definition
No longer in active use, production, or service. In aviation, an obsolete part, procedure, publication, or piece of equipment has been formally superseded by a newer version or withdrawn from approved use, and should not be relied upon for current operations.
Plain English
Out of date and no longer used. Something newer or better has replaced it, or it has been withdrawn altogether.
Context Anchor
A pilot may see this word when discussing old charts, outdated procedures, replaced equipment, expired manuals, or parts that are no longer used.
Derivation
From the Latin obsoletus, meaning 'worn out' or 'fallen into disuse.' The aviation use keeps that exact sense -- a part or procedure that has had its day and is no longer fit for current service.
Why Pilots Care
Using an obsolete part or procedure can create safety risks and violate regulations.
Intuition Check
Obsolete does not simply mean old. It means old enough, replaced enough, or out of use enough that it should not be treated as current.
Example Sentence 1
He removed the obsolete approach plate from his binder and replaced it with the current revision.
Example Sentence 2
The pilot discarded the obsolete approach plate and used the current chart instead.