G Warwick, Piasecki and Hypoint to bring hydrogen to helicopters, Aviation Week & Space Technology, 30 August-12 September 2021, p 43

In UK, production will begin of the Piasecki Hypoint 650 kW high-temperature PEM fuel-cell module for the five-seat helicopter PA-890. The module is arranged in radial format, permitting air cooling and thus dispensing with a heavy liquid-cooling system.