Production aircraft were powered by various models of the Avon engine. This power-plant was initially rated as capable of generating of dry thrust, but when employing the four-stage afterburner this increased to a maximum thrust of . Later models of the Avon featured, in addition to increased thrust, a full-variable reheat arrangement. A special heat-reflecting paint containing gold was used to protect the aircraft's structure from the hot engine casing which could reach temperatures of 600 °C. Under optimum conditions, a well-equipped maintenance facility took four hours to perform an engine change so specialised ground test rigs were developed to speed up maintenance and remove the need to perform a full ground run of the engine after some maintenance tasks. The stacked engine configuration complicated maintenance work, and the leakage of fluid from the upper engine was a recurring fire hazard. The fire risk was reduced, but not eliminated, following remedial work during development. For removal, the lower No.1 engine was removed from below the aircraft, after removal of the ventral tank and lower fuselage access panels, by lowering the engine down, while the upper No.2 engine was lifted out from above via removable sections in the fuselage top.