 One of these was evaluated by the RAF before it was decided that the rival Goblin would be adopted for the RAF Vampires instead; another contributed to development work for the Vampires for the Royal Australian Air Force (RAAF).Although the Nene had a higher thrust than the Goblin, the level flight speed was no greater.To reduce the intake losses caused by having to feed air to the rear face of the impeller of the Nene, two additional intakes were added behind the cockpit; these caused elevator reversal and buffeting tendencies, which in turn reduced the Vampire's Mach limitation.