The Wing and Rotor Aeroelastic Test System (WRATS) data acquisition system (DAS) is a 64-channel data acquisition display and analysis system specifically designed for use with the WRATS 1/5-scale V-22 tiltrotor model of the Bell Osprey. It is the primary data acquisition system for experimental aeroelastic testing of the WRATS model for the purpose of characterizing the aeromechanical and aeroelastic stability of prototype tiltrotor configurations. The WRATS DAS was also used during aeroelastic testing of Bell Helicopter Textron’s Quad-Tiltrotor (QTR) design concept, a test which received international attention. The LabVIEW-based design is portable and capable of powering and conditioning over 64 channels of dynamic data at sampling rates up to 1,000 Hz. The system includes a 60-second circular data archive, an integrated model swashplate excitation system, a moving block damping application for calculation of whirl flutter mode subcritical damping, a loads and safety monitor, a pilot-control console display, data analysis capabilities, and instrumentation calibration functions. Three networked computers running custom-designed LabVIEW software acquire data through National Instruments data acquisition hardware.
The aeroelastic model (see figure) was tested with the DAS at two facilities at NASA Langley, the Transonic Dynamics Tunnel (TDT) and the Rotorcraft Hover Test Facility (RHTF). Because of the need for seamless transition between testing at these facilities, DAS is portable. The software is capable of harmonic analysis of periodic time history data, Fast Fourier Transform calculations, power spectral density calculations, and on-line calibration of test instrumentation. DAS has a circular buffer archive to ensure critical data is not lost in event of model failure/incident, as well as a sample-and-hold capability for phase-correct time history data.The system has an interface to drive TDT text overlay display video monitors and an interface to trigger digital video recording (DVR) systems.
DAS uses NI SCXI signal-conditioning hardware to power, amplify, and anti-alias-filter the 64 channels of sample- and-hold time-correlated data at sample rates up to 1,000 Hz. The WRATS data system as a whole maximizes efficient tiltrotor aeroelastic test practices at the TDT by allowing seamless integration of model swashplate stik-stir excitation commands with data acquisition capabilities and post-point damping analysis. Following analysis, the system reports key results to a MATLAB- based data logging system for archiving, organization, and reporting of test results.
In addition to test efficiency, the system improves the safety-of-flight environment of the test process by calculating and monitoring critical model loads, stress, and parameters in real time during testing. In the event of unsafe conditions or loads, audible, synthesized voice alerts are provided to the test crew in addition to visual display cues on the WRATS Loads Monitor displays, which are networked with the WRATS data system.
This work was done by David J. Piatak of Langley Research Center.