This document describes a standard method for measuring the viscosity of thickened (AMS1428) Type II/III/IV Aircraft Deicing/Anti-icing Fluids. The determination of viscosity for a Non-Newtonian fluid is very sensitive to shear and differences in sample chamber geometry. Even slight differences can have a large effect on measurement results. The test parameters and associated error for this standard are applicable to the Brookfield LV viscometer. A Brookfield LV or equivalent viscometer shall be used. To be considered equivalent, an alternate viscometer must demonstrate statistically equivalent performance, i.e., accuracy and precision when testing thickened (AMS1428) fluids using the same test parameters and conditions.Test parameters and conditions outside of the ranges described within this standard may be used only if they meet minimum limits for precision and accuracy established for the Brookfield LV viscometer. To compare viscosities, the same test parameters and conditions (including spindle number, rotation speed, sample volume and container type, sample temperature, and measurement duration) shall be used.