As with the Marathon, the HPR-3 Herald was originally configured with four Alvis Leonides Major piston engines of 870 hp (650 kW) each, driving three-bladed propellors.
The HPR-3 Herald was originally configured with four Alvis Leonides Major piston engines of 870 hp (650 kW) each, driving three-bladed propellors. This was as with the Marathon.