We’ve just achieved a further two important steps in the 787 flight test program – we completed flutter testing and ground effects testing.
Both of these accomplishments move us much closer to achieving Type Inspection Authorization (TIA) from the Federal Aviation Administration.
“Flutter” is something you definitely do not want to happen in flight. It occurs when aerodynamic forces act on airplane structures and control surfaces causing a rapid, self-feeding motion that can be very destructive.
So, during flutter clearance testing we purposely introduce oscillations to verify that the airplane is not subject to flutter when operating within normal parameters. We verify it by demonstrating that even when an oscillation is introduced, the airplane will dampen the effect.
ZA001 takes off from Boeing Field during flight test.
We tested at a variety of altitudes, speeds and fuel loads on ZA001. During the testing, we saw altitudes above 43,000 feet, dive speeds as high as Mach 0.97, and calibrated airspeeds as high as 405 knots.
The technical team has made an initial assessment of the data and we couldn’t be more pleased with the performance of the 787. The damping was as predicted and the pilots report that the airplane responded as expected.
Based on this data, the 787 test fleet has now been cleared to fly throughout its full flight envelope.
For the ground effects testing, conducted in Victorville, we looked at the aerodynamic effects on the airplane during low-altitude operations typically experienced during the takeoff and landing portions of a flight. This testing, conducted on ZA002, also went very well and matched our expectations.
Our test data is being turned over to the FAA as part of our Type Inspection Authority submittals. Upon validation by the FAA of this and other test items, we’ll see their technical teams join ours as we move into the next phase of this process – certification testing.
During certification testing - the longest of the four phases - we look at the extremes of the flight envelope including hot weather, cold weather, high altitude, over-speed conditions, hard landings and engine-out conditions. We also explore the details of performance from fuel burn to community noise.
There’s a lot left to do in flight test but no doubt we’re making great progress.