Ground test crewmen checking the RR RB211-535C engines of the 757 after completion of engine runs. The engines were started and initial checkout begun on January 23, just 10 days after the aircraft rolled out. The next day, full power runs were made to takeoff thrust of 37.000 pounds and trim tests were completed. Additional runs on January 25 were for calibration purposes, acceleration response, fuel flow measurement and checks of the engines' electronic control system. the RR engines were said to cut fuel consumption by 48% comparted to the aircraft it would replace. Photo from Boeing

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