As the general aviation market slid downhill in the final 15 years of the last century, propeller manufacturers Hartzell (www.hartzellprop.com) and McCauley (www.mccauley.txtav.com) were faced with vanishing demand. Their response was to break away from their historic reliance on aircraft manufacturers and invent new products that would appeal to owners of existing airplanes via STCs.
Hartzell came out with its sharp Top Prop line at about the same time McCauley developed its aggressive-looking Black Mac line of three- and four-blade propellers. Both began getting STCs for as many airplanes as their budgets allowed.