The Flight Loads Laboratory (FLL) at NASA’s Armstrong Flight Research Center in Edwards, California, conducts mechanical load tests on structural components as well as full-size aircraft. Typical tests include strength verification, stiffness, and material coupon characterization.
For mechanical load tests of aircraft, loads are applied through hydraulic actuators and regulated with up to 40 channels of closed-loop control, using load cell feedback. Hydraulic actuators and load cells with capacities to 300,000 pounds in tension and compression are available.
An example of a large closed-loop control loads test was the YF-12 flight vehicle test. This test required 20 channels of closed-loop control in order to apply the loads necessary to calibrate strain gages for the measurement of flight loads. These tests were conducted in the high bay test area with setups assembled from an “erector set” inventory of structural members or from specially designed built-up structures.
Another example of this type of testing was the test performed on the F-15 Advanced Control Technology for Integrated Vehicles (ACTIVE) airplane. This test provided strain gage information to determine in-flight vectored thrust loads. A unique feature of the test was the need to consider large displacement loadings. Using torque tubes in place of engines, three-axis component loads were applied to simulate the vectored thrust loads of this vehicle.
The FLL also has four universal testing machines. Three are closed-loop electrohydraulic machines, each with a digital engineering unit display and an X-Y recorder. One machine has a maximum load capacity of 10,000 pounds; the second and third machines have load capacities of 100,000 pounds and 220,000 pounds, respectively. The fourth machine is a screw type with a maximum load capacity of 2,500 pounds. All four machines are used for static loadings of coupons and structural components at ambient and elevated temperatures. These machines are located in a separate small test area, although data from these machines can be recorded on the FLL data acquisition system.
