Introduction

1. Introduction A PORTABLE DATA ACQUISISTION SYSTEM FOR FLIGHT TESTING LIGHT AIRCRAFT Karl E. Garman & Dominick A. Andrisani II School of Aeronautics & Astronautics Purdue University

2. Recognition of Need • There is a growing need to test the performance characteristics of small aircraft • Data acquisition for flight testing small aircraft has often been performed by • manually recording instrument readings • Until recently, electronic data acquisition was not realistic for such aircraft • Often, installation of flight test instrumentation involved the cumbersome • alteration of certain parts of the aircraft’s structure • Potential for use in a Purdue University course in flight testing • This effort involved the development of portable, • low cost, computer-aided electronic instrumentation • for gathering flight test data on light aircraft

3. Design Challenges • Wish List: • Inertial Data ………………..What is the airplane doing in the inertial reference frame? • Air Data …………………….What is the airflow relative to the airplane? • Control Deflection Data …..What are the control surface deflections? • Pilot Command Data …….. What are the control force inputs and feedbacks? • Constraints: • FAA Certification …………..Purdue aircraft must be kept in Normal Category. • Risk Management …………Experimental R&D is not possible with students aboard. • Flight Operations …………..Minimum bureaucracy for each flight is essential. • Verdict: • System Location……………Place integrated INS/GPS in baggage area (cargo). • Air Data Boom ……………..Possible with special one-time FAA approval (not pursued). • Pilot Command Data ………In situ placement of such instruments not feasible.

4. Instrument System Overview Low-cost instrumentation for recording flight test data: • Recording m-INS/GPS mounted in baggage compartment • 1 Hz GPS update rate / 10 Hz INS update rate • Accessible to flight crew Pallet & Components Mounted in Baggage Compartment Sony VAIO Status and Control Computer On Lapboard Chassis Box Power Supply Ethernet Cable m-INS with GPS receiver External GPS Antenna (to be affixed in aircraft window) RS-422 to RS-232 Protocol Converter Box (with power switch and safety fuse) Dell Inspiron Logging Computer With LabVIEW, INS and Signal Conditioning Equipment

5. m-INS Data Packet andSpecification Tables m-INS Data Packet Output m-INS Specification Table Latitude Longitude Altitude Yaw (magnetic) Yaw (true) Pitch Angle Roll Angle GPS Time Velocity East Velocity North Velocity Up X Axis Rate Y Axis Rate Z Axis Rate X acceleration Y acceleration Z acceleration Static baro Dynamic baro Status 1Typical values 3Performance specs are given based on a 5-minute warm-up time

6. Instrument System Architectureand Data Flow GPS Antenna (in aircraft window) Dell Inspiron Logging Computer (Running LabVIEW Data Acquisition Program) m-INS ~10Hz Hex Packet Data Output RS-422 Data Stream RS-232 Data Stream Protocol Converter 24 VDC Power System TCP/IP Protocol Ethernet Cable Components of System in the Aircraft Baggage Compartment Sony Vaio User Interface in cockpit

7. System Integration Considerations • Power System: • Independent of aircraft electrical system for certification and safety purposes • GPS Reception: • Visibility of GPS satellite constellation by GPS antenna • Antenna should be located away from high multipath environments • Computer Interfacing: • LabVIEW software aids efficient development of data acquisition routines • Use of Windows-based operating system allows use of LabVIEW software • Use of TCP/IP to interface between computers negates need to write software drivers

8. User Interface (on Sony Vaio) LabVIEW front panel user interface GPS status window Purpose: Status indication and control of the data logging

9. m-INS Post ProcessProgram Front Panel LabVIEW Front panel for post processing m-INS output (hexadecimal to base ten) Post Processing In-flight Logging m-INS data stream ASCII Hex file decoded output uINS1.vi PostProcess.vi base 10 text file

10. Demonstration Platform Cessna 182 Skylane Aircraft used for student flight instruction. Registered as a “Normal Category” aircraft under the FAA. Data acquisition system was placed the in baggage compartment with a temporary GPS antenna mounted in the rear window

11. Flight Tests • GPS Airspeed Calibration Test • Purpose: Test groundspeed output of m-INS against a certified instrument • Various heading tracks were flown to determine winds aloft and true airspeed • An airspeed calibration chart was produced and compared with handbook values • Results compared to instrument-certified GPS (Bendix King KLN89) Wind Direction Wind Speed True Airspeed

12. Airspeed Conversion Process +DVc +DVic +DVpc Indicated Airspeed (IAS) Instrument Corrected Airspeed Equivalent Airspeed (EAS) Calibrated Airspeed (CAS) True Airspeed (TAS) • True Airspeed is calculated with GPS Airspeed Method • DVic was not independently determined • The sum of DVic and DVpc was found • Vary the IAS to determine (DVic+ DVpc) as a function of IAS

13. Groundspeed Outputs FromKLN89 and m-INS

14. m-INS Inertial Velocity Anomalies 90 knot South Track s = 10.6 knots 90 Knot East Track s = 1.1 knots Something is wrong here Aircraft was maintained in level, unaccelerated flight for each airspeed test leg Standard Deviations of m-INS Groundspeed Data

15. Position Error Correction Chart DVic + DVpc (knots) * ** Assumes DVic=0

16. Phugoid Mode Of Cessna 182P Approximately 28 seconds Control Yoke Release Asymptotically Damped Motion Is Evident 4500’ Pressure Altitude OAT=57 deg F

17. Conclusions • As demonstrated, a “Normal Category” portable data acquisition system • has been built and used in a Normal Category aircraft • Main design challenges were from FAA regulations instead of technical concerns • Use of TCP/IP data transmission negated the need to rewrite software drivers • Common commercial computer equipment allowed the use of LabVIEW and • other Windows-compatible software • m-INS velocity and angular output data from the flight experiments compared • well with certified instrumentation and emperical calculations • Limiting factors for use in particular aircraft include cargo area geometry and • visibility of the GPS antenna to the GPS satellite constellation

18. Acknowledgements • Rockwell Collins Avionics, Cedar Rapids, IA • Dr. Dominick Andrisani II, Dr. Galen King, Dr. James Garrison • Dr. Robert Santini, Dr. Mike Everly, Mark Carlsen, Bob Fagan, Jonathan Amy Facility for Chemical Instrumentation (JAFCI) of the Purdue University Department of Chemistry • Brian Stirm, Department of Aviation Technology, Purdue University • Dr. Paul Shepson, Departments of Chemistry and Earth & Atmospheric Science, Purdue University