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A man standing inside the front engine cowling may only stand as tall as the engine's halfway point in the opening. He would most certainly touch the top rim of the 747 standard engine pictured on the outboard wing.
Imagine the wing weight on the port side causing the 747 to tilt towards its port during its lift-off. So GE engineers had to compensate the aircraft for a level take-off. Much like, in the old days, fuel tanks had to stay in the balance of the aircraft's centerline by often switching fuel tanks stored its wings while keeping the aircraft in the balance as the fuel volume depletes. Today's fuel volume weight is balanced by computers. I imagine this GE 9X equipped 747 has starboard ballast tanks to compensate for the extra 9X engine weight on the port side. It's that big!
This test program has just completed its first flight in four hours. All went smoothly checking off the first flight test points with complete satisfaction. The 777X program has achieved a critical milestone with this success. More GE tests will continue until all checkpoints conclude the initial engine operations tests later this year. When Boeing completes its 777-9X body these GE-9X's will be mounted for ground tests late 2018 and first flight later in 2019.