Boeing 777 Major Static Test Video Audio Transcript

Thomas A. Briggs, Manager 777 Major Static Test Lab: 

The 777 Major Static Destructions Test is really the combination of 7 months of intense effort to complete certification of a test airplane.  And the test was very successful.  The test system, the test aircraft, and the people associated with the test performed flawlessly in a very successful test.

The aircraft that we use for our test article is a production airplane – it’s the number 2 airplane from the line.  It was rolled over from the 40-25 building at midnight on February 18th.  To be able to get the airplane from the 40-25 building, we needed some way to do that.  We used a production gear, and the airplane was brought over with the standard-type tow bar, and we pulled it in a test rig.  We built a little bit different test rig than we’ve done in the past.  We designed it so that it can be cantilevered and a lot of the structure could be in place.  By doing that we were able to install a lot of the early instrumentation that needed to go in place, and we started running cable about 4 months before the airplane ever arrived.  After the airplane arrives, we take many of the control surfaces and we install tension pads that are bonded to the surface and we use this also to proof-load these surfaces.

Another part of fabricating the airplane, very early, two years ahead, they plan to put strain gauges inside the rudder because it’s a closed-out structure.  Altogether, as the airplane got close to test, we had installed over 4,000 individual strain gauges, and at each test the maximum number of strain gauges we read was 2,048.  There’s cabling that goes to each of the 6,000 channels of strain gauges that are located within the airplane, and, to be able to get from the front end part of the data system up into the structure, into the airplane, there was approximately 500 miles of cable run – a massive amount of weight.

Really, a lot of the organizations that have to be integrated into a test program this size; structures lab – within my own organization, we had up to 30 different engineers and technical people working on this program for about 2½ years.

Some of the testing during the certification is critical to the flight test program.  Part of that is what’s called TIA or Type Inspection Authorization that Boeing obtains from the FAA.  Our part on the static test of that TIA is to meet certain proof tests by a certain amount of time so that they can go ahead and fly those conditions on the flight test – number 1 airplane.  So the airplane is lifted off of the gear during the flight condition, and so the airplane is totally free floating and balanced by the air-loads as we test.

A little bit about the loads that are applied on the destruction test – this is a 2.5G dive maneuver test condition at limit load.  There’s 1.5 factor to go to ultimate load so we essentially apply it at 3.75G+ since we went over that 150% design limit load.  To be able to do that, we had to apply 500,000 lbs to each wing to keep the airplane from moving up.  We had to react that with 1,000,000 lbs down on the fuselage, and that’s what balances the airplane.  We also measure the deflection of the fuselage and as we see the movement of the wing quite a bit, but not realizing the tip of the tail of the fuselage is also moving 16-20 inches on some of these tests.

Wing failure occurred at 154.4% from our initial readings.  Failure occurred in both wings, so again analyzing data afterwards we determined that they failed 20 milliseconds apart; right wing going first.  Additional analysis after that showed that the right wing failed beginning in the area of rib 25, and the left wing also failed at rib 25 and also at rib 21 on the upper surface of the wing.  This was as they expected.  They had high-speed video exactly in that location and were able to capture those failures as they progressed.

This test, at destruction, we failed at approximately 24 feet tip deflection of the wing.  They had a capability in the test rig, and all of our structures to go to 187.5% so we still had some margin to go and we were prepared to go as far as we needed to, to get destruction.  The folks that worked in support of the test, their attitude came from really feeling an ownership of the overall test, and I was quite pleased with the way everybody really, throughout all the teams, would say “this is the test I’m working,” and they felt the ownership of it, and it really impacted the way we can meet the schedules during the test.

< Back