I'm not sure exactly what you mean by "detected", but the bulk of the research on the forces normal to the propeller axis of rotation was done in wind tunnels by groups such as NACA. The usual reference is "Propellers in Yaw" by Herbert Ribner, NACA Report 820. The forces were "detected" by the wind tunnel balances.
A slight variation to this would be the work done on the effect of downthrust (tilt down of the propeller axis) on longitudinal static stability, eg "Effect of tilt of the propeller axis on the longitudinal-stability characteristics of single-engine airplanes" by Harry Goett and Noel Delaney, NACA Report NACA-TR-774. You could argue that the impact of vertical force affects long-stat, and thus is "detected" in that measurement.
Not sure if this helps you.