Definition
The rear edge of the upper surface of an airfoil — specifically, the line along the back of the wing where the upper skin ends and meets the trailing edge. In flap discussions, it refers to the part of the upper wing surface just ahead of the flap hinge, where airflow separates or remains attached as the flap deflects.
Plain English
The back edge of the top side of the wing — the line where the upper surface of the wing ends at the rear.
Context Anchor
Seen in discussions of flap effectiveness, especially when comparing how different flap designs change the shape and airflow near the back of the wing.
Derivation
“Trailing” comes from the idea of following behind. In flight, the trailing edge is the edge of the wing that is behind the rest of the wing as the airplane moves forward; “upper” points to the top side of that edge.
Why Pilots Care
How airflow behaves over the upper trailing edge when flaps are extended affects how much extra lift and drag the flaps actually produce. Some flap designs keep the airflow attached at the upper trailing edge longer, which improves their effectiveness at slow speeds.
Intuition Check
Do not read “upper trailing edge” as simply the highest rear part of the airplane. Here it means the top back edge area of the wing or flap, relative to the wing’s shape and airflow.
Example Sentence 1
With a plain flap deflected, airflow tends to separate near the upper trailing edge, reducing how much extra lift the flap can produce.
Example Sentence 2
A damaged upper trailing edge can reduce flap effectiveness and increase stall speed.