This 'drop test' is done to simulate a landing on an aircraft carrier
(Dallas, May 7, 2010) -- The anticipation was palpable as Vought engineers and our customer watched Lockheed Martin's F-35C Lightning II Carrier Variant dangle from its harnessed position just below the rafters in building 94 at the Jefferson Street site. When the wheels reached their 138 knot speed, the countdown began. 10, 9, 8, 7... The lanyard releasing the quick release safety latch was pulled and the jet was dropped. It was over in five brief seconds.
. As a fighter jet approaches the deck of a carrier, forty-six thousand pounds of airplane is traveling at 138 knots and hitting the deck with a thud, stressing the airframe and especially the jet's landing gear with thousands of pounds of pressure. Every part of the gear must withstand that tremendous stress time after time with no structural failure.
So how can we assure that the gear is suitable for carrier landings, and there won't be any catastrophic failures? How do we prove that the design engineering was correct? That's where Vought's Test Lab comes in. The lab is capable of lifting a fully-loaded, fullscale aircraft up to eleven feet above the floor ... and dropping it. Lockheed Martin has contracted with us to drop test the F-35C Lightning II Carrier Variant, a fifth-generation, single-seat, single-engine stealth fighter.
Hundreds of wires snake along the sleek lines of the light green jet, connected to an array of instruments that are streaming signals back to a computer for correlation to computer models that engineers spent many months designing. This data acquisition system is measuring every quiver, shudder, and pulse that is emitted from the test jet. Technically speaking, however, F-35 Drop Test Director Tom Foster says they are measuring strain, acceleration, deflection and load data. This is where the rubber meets the flight deck, so to speak.
There are 512 data channels connected to this aircraft. Twenty-five hundred data samples are gathered per second per channel during each drop test for this aircraft. Per Eric Moore, Test Control and Data Acquisition group lead, high speed video of each landing gear is simultaneously recorded at two thousand frames per second and synchronized with the aircraft test data for post-test, image-to-data correlation. In other words, each high speed video picture can be directly compared to the load and deflection data measured and recorded on each landing gear. This was not possible in the old days when high speed film-based cameras and analog recording equipment was used in this application.
Eventually, there will be about 53 landing gear drop tests at various aircraft roll, pitch and landing sync rates performed on this one jet. A stack of bombs in the corner of the room awaits their turn alongside a row of missiles to be loaded onto the jet to test for maximum landing weight conditions. Of course, they are dummy ordnance but they are fabricated to weigh in as a real load.
Today, Vought is one of only two test labs remaining in the United States that has full-scale carrier suitability drop test capabilities. The other is at Boeing, St. Louis. According to John Vaught, Test Lab Manager, the F-35 Drop Test Program in total represents a very high level of complexity generally not seen on previous drop test programs. "The ability and know-how to do these drop tests are very unique," he said.
With the level and type of test capabilities the labs possess, Vought has a long, and very reputable history of accomplishing carrier suitability testing for the Navy, said John. "We can go all the way back to the XC-142, F-8, A-7, S3A, and now the F-35. All of these legacy aircraft programs required fullscale drop testing to qualify for aircraft carrier operations. Full-scale dynamic tests of this nature present a very complex test set of problems to run," he said.
The F-35 tests at Vought should be completed within the next few months; then it will go back to Lockheed Martin for a series of additional tests. They estimate that the Carrier Variant F-35C will attain first flight in the second quarter of 2010.
Source : Vought Aircraft Industries