Definition
A method of displaying the results of an ultrasonic nondestructive inspection in which the cathode-ray tube or screen shows a horizontal baseline representing time, with vertical spikes (pulses) indicating the location and relative size of any reflected ultrasonic signals returning from the surface, the back wall, or any internal flaw within the part being tested.
Plain English
A way of showing the results of an ultrasonic test on a screen. The screen displays a flat line with vertical spikes — each spike marks where sound waves bounced off something inside the part. The position of the spike shows how deep the reflection came from, and the height of the spike shows how strong it was, which helps the inspector judge the size of any flaw.
Context Anchor
Seen in aircraft maintenance when a part is inspected for hidden cracks, voids, or other internal damage without cutting it open.
Derivation
The 'A' simply labels the first and most basic of several ultrasonic display formats (A-Scan, B-Scan, C-Scan), each presenting the same return-signal data in a different way. The A-Scan shows amplitude against time on a single line, which is where its name comes from.
Why Pilots Care
A-Scan results help maintenance personnel find hidden defects in aircraft parts before those defects become safety problems.
Analogy
Think of it like sonar on a fishing boat shown as a single line: a bump near the start of the line means something close to the surface, a bump farther along means something deeper, and a tall bump means a bigger reflection.
Grounding Statement
A sound pulse is sent into a part, and the A-Scan shows the echoes that come back from inside it.
Intuition Check
Do not read “scan” here as a picture of the whole part. An A-Scan is a line-style signal display, not a photo or image.
Example Sentence 1
The inspector used an A-Scan display to locate a small crack in the wing spar forging by reading the position and height of the return spike.
Example Sentence 2
A clear A-Scan with no intermediate echoes confirmed the skin panel was free of delamination.