Here to there: 787 pre-first flight milestones explained

GROUND VIBRATION TESTING
Dreamliner Two will be moved from Building 40-26 to the 767 line (Building 40-24) where the second flight test 787 will undergo ground vibration testing to preliminarily check out the airframe for in-flight wing flutter testing. Wing flutter is defined as "a self-starting and potentially destructive vibration where aerodynamic forces on an object couple with a structure's natural mode of vibration to produce rapid periodic motion."

In English: the wing can shake itself to destruction under certain conditions. Residents of the Pacific Northwest have a famous (non-aviation) example of flutter in the collapse of the Tacoma Narrows Bridge in 1940. Wing flutter testing will be a central part of the in-flight test regimen for ZA001.

STATIC TESTING
ZY997, the static test airframe, must complete three structural tests before ZA001 is given a green light for first flight. These tests evaluate the overall strength of the aircraft structure. The first was the high-blow cabin pressurization test completed in late September 2008.

• 1G CHECKOUT

The second is the 1G check out that flexes the wings to loads equivalent to flying straight and level, a deflection of about 10 feet. This test looks for any gaps or interferences on the movable leading and trailing edges of the wing, also known as the slats and the flaps. This test was completed on March 20th.

• WING LIMIT LOAD

The third is a limit load test that flexes the wings to 100% of the maximum loads 787 is expected to encounter in flight. This is different from the critical load test that takes the wing to above 26 feet of deflection and 150% of limit load. The critical/ultimate load test will be run after first flight.

GAUNTLET TESTING
With Dreamliner One out of the paint shop and back in the factory, the aircraft will soon begin the first of three stages of rigorous gauntlet testing.

"Gauntlet testing is where we attach a closed loop simulation to the airplane while it's on the ground so we can demonstrate the basic function of the flight controls and other systems," said Pat Shanahan VP and General Manager of Airplane Programs.

There are 92 systems that are required to support this testing, all of which have been cleared for first flight. During the testing, the aircraft "electrical power distribution and utilization are tested and pushed, and systems are put through their paces for one last time before flight," said Boeing.

• FACTORY GAUNTLET

The factory gauntlet is the first stage of systems integration. The first phase, which takes place in doors, will test most, but not all, of the airplane's systems integrated on ZA001. The Flight Test team will look closely at the onboard systems and verify they function as expected. Most of the aircraft's systems will be tested and the aircraft's power will be drawn from ground cart and battery power. The engines and APU will not be turned on during the indoor phase of gauntlet testing.

• INTERMEDIATE GAUNTLET

The second phase of gauntlet testing will see ZA001 moved to the flight line where Dreamliner One will fueled up and run under its own power for the first time. The Hamilton Sundstrand Auxiliary Power Unit in the tail cone of the aircraft will be spooled up and will supply power to the aircraft's systems for continued integration testing. This phase of the gauntlet will also see the twin Rolls-Royce Trent 1000 engines powered up for the first time as well. This is an incredibly key series of tests that will serve to validate the integrated more electric aircraft systems architecture that is the foundation for the 787.

• FINAL GAUNTLET

During final gauntlet testing, the systems are left running for eight straight days for extensive testing. This phase of testing will simulate every imaginable failure to see how the aircraft software reacts.

FINAL TESTING

• HOT RUN

Before the first flight of any Boeing aircraft, production or other wise, the engines will be pushed to full power in an exercise called the "hot run". The Trent 1000s will be run to full power for 90 seconds simulating a takeoff run then pulled back slightly for a simulated climb to altitude. The Trent 1000 engines will be evaluated at different power settings throughout the final weeks before first flight.

• SLOW/MEDIUM SPEED TAXI TESTS

After gauntlet testing is completed, taxi tests will validate and check out the nosewheel, steering, brakes and anti-skid systems to evaluate ground handing qualities of the 787.

• HIGH SPEED TAXI TEST

Just before first flight, ZA001 will be pushed to just before the V1 speed, lifting the nosewheel off the ground followed immediately by deployment of the spoilers, thrust reversers and brakes to validate the stopping capability of the aircraft. This is done to ensure that in case of an emergency during the first takeoff roll, ZA001 can stop safely. This test historically has been conducted on the day prior to first flight.