Piqua, Ohio-based Hartzell Propeller has announced the development of a new two-blade Top Prop conversion kit for Piper PA-23-250 Aztec twins. The scimitar-shape, 77-inch propeller blades incorporate blade-mounted counterweights, offering greater redundancy for pitch control and feathering, compared with the original-equipment propellers that relied on air pressure. The shape of the blades is more efficient, yielding a 2-to-3-knot increase in cruise speed, and noise reduction of close to 2 dB(a). The conversion kits are available for Aztec C models through F models powered by Lycoming IO-540-C4B or TIO-540-C1A engines. They are available with 14- or 28-volt de-ice systems and include composite spinners. Total weight is 62 pounds per side, and installation is expected to take just a few hours, said Hartzell, since no changes are required to the prop governors. Through its dealer network, Hartzell is offering an introductory price of $21,950 for the basic kit, including a three-year/1,000-hour warranty and a six-year/2,400-hour time between overhaul. To date, Hartzell reports it has delivered more than 17,000 of its Top Prop conversions worldwide.