Washout is a deliberate twist built into a wing such that the angle of attack at the tip is lower than at the root. Typically 1–4° of washout is used, meaning the tip airfoil is angled slightly nose-down relative to the root airfoil.
Why washout matters: Without washout, a rectangular or tapered wing tends to stall at the tips first — the tips operate at higher local angles of attack due to induced downwash effects and taper geometry. Tip stall is dangerous: it causes sudden loss of aileron authority (since ailerons are outboard) and can trigger a spin. With washout, the root reaches its stall angle first while the tips still have margin, preserving roll control into the stall.
Geometric washout — physically twisting the wing structure so the tip has a lower incidence angle. Simple to implement in construction: a twisted spar, a jig that holds the tip at a different angle, or a 3D print with the twist modeled into the CAD geometry.
Aerodynamic washout — using a lower-camber or thinner airfoil at the tip than at the root, so the tip produces less lift at a given angle of attack without physically twisting the structure. More complex to design but avoids the manufacturing challenge of holding a precise twist angle during construction or printing.
For 3D-printed wings, washout can be modeled precisely in CAD and reproduced identically in every print — an advantage over hand-built foam-core wings where washout depends on jig accuracy and builder skill. However, warpage during printing or cooling can introduce unintended twist, so the as-built washout should be verified before flight.
Delta wings generate a related effect naturally: the strong leading-edge vortices that form at high angles of attack tend to break down at the tip first, giving progressive stall behavior without explicit washout. This is one reason delta planforms are forgiving of manufacturing imprecision.
Related terms
- Stall — the condition that washout is designed to manage
- Aileron — the control surface preserved by washout’s tip-stall prevention
- Angle of Attack — the variable that washout modifies spanwise