Definition
The total roll-stability effect produced by a wing's design features acting together, expressed as the equivalent amount of geometric dihedral (wingtips angled upward) that would produce the same rolling tendency back toward level flight after a sideslip. Sweepback, high wing placement, and actual dihedral angle all contribute to a wing's effective dihedral.
Plain English
It is how strongly an aircraft naturally tries to roll back to wings-level after a sideways slip, measured as if all that rolling tendency came from the wings being tilted upward at the tips — even when most of it actually comes from other design choices like wing sweep or a high-mounted wing.
Context Anchor
Seen when studying lateral stability, sweepback, and how high-wing or low-wing airplane designs affect roll behavior.
Derivation
"Effective" here means "in its overall result" rather than "working well." The term groups several different design features under one combined measurement, because they all produce the same kind of effect — restoring roll after a sideslip.
Why Pilots Care
It supplies roll stability on many jet and high-wing aircraft, affecting handling qualities and reducing the amount of actual dihedral the designer must add.
Analogy
Think of several small design features all pushing in the same direction. Even if the wings are not angled up very much, the airplane may still behave as though they are because those features add to the same stabilizing effect.
Grounding Statement
Picture a gust pushing the airplane slightly sideways; effective dihedral is the airplane’s built-in tendency to turn that sideways airflow into a roll back toward wings-level.
Intuition Check
Effective does not mean “best” here; it means the total result actually produced. Dihedral in this phrase does not mean only the visible upward wing angle; it also includes other design features that act like dihedral.
Example Sentence 1
The high-wing trainer has significant effective dihedral, so it tends to roll back to level on its own when a wing is bumped down by turbulence.
Example Sentence 2
Placing the wings high on the fuselage produced effective dihedral and reduced the need for additional wing angle.