Tuft (aeronautics)

In aeronautics, tufts are pieces of yarn or string, typically around 15 cm long, attached to an aircraft surface in a grid pattern and imaged during flight. Their motion can be observed and recorded to locate air flow features such as boundary layer separation and reattachment. Tufting is, therefore, a technique for flow visualization. They are used during flight testing to study air flow direction, strength, and boundary layer properties.

The world's largest bed of tufts (18.6 m by 18.6 m, 61 feet by 61 feet) was created at NASA Ames Research Center to study air flow fields involving a helicopter's rotor disk.