Definition
In nondestructive testing of aircraft structures, the primary wave is the initial ultrasonic pulse transmitted into a part by a test probe. It travels through the material and reflects back from internal flaws or from the far surface, allowing inspectors to detect cracks, voids, or delaminations.
Plain English
The first sound pulse sent into a part during an ultrasonic test. Echoes from this pulse reveal hidden damage inside the material.
Context Anchor
Seen in discussions of radio navigation reception, especially when comparing direct signals with reflected signals that can cause indication errors.
Derivation
From Latin primus, meaning 'first.' Called primary because it is the original transmitted wave, before any reflections or secondary signals return.
Why Pilots Care
Recognizing the primary wave helps pilots anticipate strong lift, sink, and rotor turbulence that can exceed aircraft performance limits or create severe control problems.
Grounding Statement
Picture the airplane receiving one signal that comes straight from the station and another that arrives later after bouncing off a surface; the straight one is the primary wave.
Intuition Check
Primary does not mean “strongest” or “most important” here. It means the direct signal that arrives first by the intended path.
Example Sentence 1
The technician adjusted the probe until the primary wave appeared cleanly on the oscilloscope display.
Example Sentence 2
Before crossing the mountains, the pilot checked for a primary wave signature on the satellite image to plan the best altitude and route.