Definition
A built-in twist along the length of a wing, in which the angle of incidence decreases gradually from the wing root to the wing tip. This design causes the inboard section of the wing to stall before the outboard section, preserving aileron effectiveness and lateral control during the onset of a stall.
Plain English
The wing is twisted slightly so that the tip is set at a smaller angle than the root. This makes the inner part of the wing stall first, while the tips keep flying, so the pilot still has roll control as the stall begins.
Context Anchor
Seen in airframe maintenance, inspection, repair, and rigging when checking whether a wing has the correct built-in twist.
Derivation
The term comes from the idea of the angle being progressively 'washed' or eased out toward the tip. It is paired with its opposite, 'wash in,' where the angle increases toward the tip. Knowing the term describes a gradual reduction along the span helps the meaning stick.
Why Pilots Care
It improves stall behavior and keeps lateral control available longer during a stall.
Analogy
It is like gently twisting a long flat board so one end sits at a slightly different angle than the other. The change is small, but across the length of a wing it matters.
Intuition Check
Do not read wash out as cleaning something away or failing out of training. In this airframe context, it means a deliberate twist built into the wing.
Example Sentence 1
The designer built wash out into the wing so the root would stall before the tips, keeping the ailerons effective during stall recovery.
Example Sentence 2
During slow flight the pilot notices the wing's wash out keeps the ailerons effective.