Definition
A sharp increase in aerodynamic drag that occurs as an aircraft approaches and exceeds its critical Mach number, caused by the formation of shock waves on the airframe as local airflow reaches supersonic speeds. The drag rise begins at the drag divergence Mach number and produces a steep, non-linear climb in total drag that requires significantly more thrust to overcome.
Plain English
When an aircraft flies fast enough that air over parts of the wing starts moving at the speed of sound, shock waves form. These shock waves cause drag to climb steeply over a small increase in speed, instead of rising gradually like it does at lower speeds.
Context Anchor
Seen in high-speed aerodynamics discussions, especially when studying aircraft that operate near the speed of sound.
Why Pilots Care
This effect limits maximum efficient speed, increases fuel consumption, and can reduce control effectiveness if not accounted for in aircraft design or flight planning.
Grounding Statement
Picture a fast aircraft needing a large increase in power just to gain a small increase in speed because the airflow over parts of it has started to change sharply.
Intuition Check
Drag rise does not mean any normal increase in drag as speed increases. Here it means a sharp high-speed increase in drag tied to airflow reaching the speed of sound over part of the aircraft.
Example Sentence 1
The flight crew kept cruise speed below Mach 0.82 to stay clear of the drag rise region shown in the performance charts.
Example Sentence 2
Wing sweep and area ruling are used to delay drag rise and allow higher subsonic cruise speeds.