Definition
The branch of acoustics that deals with sound waves at frequencies above the upper limit of human hearing, generally above 20,000 hertz (20 kHz). In aviation maintenance, ultrasonics is applied as a nondestructive inspection method in which high-frequency sound waves are transmitted into a part and the returning echoes are analyzed to detect internal cracks, voids, corrosion, or material thickness changes that are not visible from the surface.
Plain English
The use of very high-pitched sound waves -- too high for humans to hear -- to look inside a metal part for hidden cracks or flaws without cutting it open.
Context Anchor
Seen in aircraft maintenance, especially during inspections that look for cracks, weak spots, or thickness loss without cutting the part open.
Derivation
From the Latin ultra (beyond) and the English sonic (relating to sound). Literally 'beyond sound' -- meaning beyond the range of sound humans can hear.
Why Pilots Care
Enables inspectors to locate internal defects without cutting or damaging parts, preserving airworthiness and preventing in-flight failures.
Analogy
It is similar to medical ultrasound: sound is sent into something, and the returning signals help show what is inside.
Grounding Statement
A technician may place a small probe on a metal part and use ultrasonics to check whether the inside of the part is sound.
Intuition Check
Ultrasonics does not mean very loud sound. It means sound at a frequency too high for normal human hearing.
Example Sentence 1
The wing spar was checked using ultrasonics to look for internal cracks before the aircraft was returned to service.
Example Sentence 2
During the annual inspection, ultrasonics confirmed that the wing attachment bolts had no internal corrosion.