Definition
The range of airspeeds, roughly Mach 0.75 to Mach 1.20, in which airflow over different parts of an aircraft is partly subsonic and partly supersonic at the same time. Within this range, local shock waves form on the airframe even though the aircraft itself has not yet reached the speed of sound, producing unsteady airflow, drag rise, and handling changes.
Plain English
The band of speeds near the speed of sound where some air flowing over the aircraft is moving slower than sound and some is moving faster. It causes shock waves and rough handling, and it sits between fully subsonic flight and fully supersonic flight.
Context Anchor
Seen in high-speed aerodynamics and powerplant discussions, especially when air over propeller tips, compressor blades, or engine inlets approaches the speed of sound.
Derivation
From Latin trans- meaning 'across' and sonus meaning 'sound.' Literally 'across the sound barrier' — the range an aircraft passes through on its way from below the speed of sound to above it.
Why Pilots Care
In the transonic range, shock waves can disturb airflow over wings and control surfaces, causing buffeting, sudden trim changes, and reduced control effectiveness. Knowing where this range begins helps pilots and engineers respect speed limits like Mmo (maximum operating Mach number).
Grounding Statement
Picture airflow speeding up over one part of an aircraft while nearby air is still slower; in the transonic range, both conditions can exist at the same time.
Intuition Check
Transonic does not mean simply faster than sound. It means the transition zone around the speed of sound, where some airflow may be slower and some may be faster.
Example Sentence 1
As the jet accelerated into the transonic range, the crew felt light buffeting caused by shock waves forming on the upper wing surface.
Example Sentence 2
Engine inlet design must account for the changing airflow patterns that occur in the transonic range.