Plenty of Pratt & Whitney 3-spools. They just happen to be Turboprops. The PW100 series is a marvelous design with each turbine stage turning a different shaft, Nh, Nl, Np. It manifests the usual 3-spool advantages, impressive Sfc, nimble power response, and easy starting. By the time ones fingers move from the start switch to the fuel control Nh is high enough to introduce fuel, and everything clicks right along. Puts the PT6 to shame.