A quick look at any artist's rendering of the 787 in flight, the eye is immediately drawn to the wings which look, by many accounts, ready to flap like a bird. One common question that has frequently been posed is whether or not when this aircraft takes to the sky, will wing flex do for 787 what the hump did for 747?
Only time will tell on that question, yet, I wanted take a closer at the wing flex issue.
The first issue I wanted to tackle was to ask the question, "Just how much are those wings really flexing in those pictures?"
I found my answer with a little help from Photoshop and the Boeing 787 Airport Planning Document. I overlaid the neutral position of the wings on top of the stylized rendering seen above. The results were surprising, the wing flex we see in the renderings of the Dreamliner comes out to roughly 10 feet.
There is no universal amount of flex to be expected in the wing, though a deflection of 10 feet doesn't appear beyond the realm of possibilities. However, this is really dependent on a number of factors, including (but not limited to) the g loads on the wing, as well as the weight and attitude of the aircraft.
Taking the idea one step farther, last week 787 Vice President of Engineering and Technology Randy Harley told a group of reporters that the wings would deflect a full 26 feet when 150% of the maximum loads were applied to the 787 wings. As a required by the FAA, all commercial aircraft must be able to withstand at least three seconds of 150% expected maximum loads on all major structures. For a historical comparison in January 1995, the 777's wings deflected 24 feet at 154% max load before they snapped in spectacular fashion.
Boeing hasn't said publicly how much they expect the 787 wings to flex before they break. A final decision is expected early next year as to whether or not to break the full-scale wings on ZY997, the static airframe, which is parked at 40-23 for testing.
Yet, a full-scale breakage of ZY997 could be very revealing. If the wing withstands loads well above 150%, then it's an important indicator that the wing could be too strong and not require as much internal structure allowing for both future growth and valuable weight savings.
Former 787 Program Manager Mike Bair speculated in jest that during a wing break test the wingtips could possibly touch above the fuselage. Whatever the result of the test is, wingtip contact or not, the world is anxiously awaiting the abandonment of artist renderings in favor of the sight of flexing wings lifting the 787 Dreamliner into the sky for the first time.
Original image courtesy of Boeing, edits by FlightBlogger