NASA Armstrong Flight Research Center’s Flight Loads Laboratory completed structural evaluations on a modified Gulfstream G-III aircraft that will serve as a test bed for the Adaptive Compliant Trailing Edge (ACTE) project. The loads tests assisted engineers in predicting the levels of structural stress the airplane will likely experience during ACTE research flights. And for the first time, some unusual hardware aided the process: the aircraft was supported by three large inflatable airbags during the tests.
ACTE project researchers have replaced the airplane’s conventional aluminum flaps with advanced, shape-changing assemblies that form continuous conformal surfaces with no visible gaps. The advanced flexible trailing-edge wing flaps have the potential to improve aircraft aerodynamic and fuel-use efficiency and reduce airport-area noise generated during takeoff and landing.
Lifting the airplane off the loads lab floor with the three inflatable airbags, the first step in the testing process, helped isolate the airframe from any potential influence of the landing gear on strain-gage data. The airbags were positioned beneath the wings and aft fuselage to keep the main gear tires off the floor so that loading throughout the aircraft's center wing box structure remained constant. Once the G-III was properly positioned, lab technicians applied loads via hydraulic jacks positioned underneath the wings.