We report recent investigations into the transition to turbulence in superfluid $^4$He, realized experimentally by measuring the drag forces acting on two custom-made quartz tuning forks with fundamental resonances at 6.5 kHz and 55.5 kHz, in the temperature range 10 mK to 2.17 K. In pure superfluid in the zero temperature limit, three distinct critical velocities were observed with
both tuning forks. We discuss the signicance of all critical velocities and associate the third critical velocity reported here for the first time with the development of large vortical structures in the flow, which thus starts to mimic turbulence in classical fluids. The interpretation of our results is directly
linked to previous experimental work with oscillators such as tuning forks, grids and vibrating wires, focusing on the behavior of purely superfluid $^4$He at very low temperatures