hiaper 3d winds – current status - dick freisen -
TRANSCRIPT
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HIAPER 3D Winds – current status
- Dick Freisen -
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U = -Ua sin (Ψ + β) + Up (east/west)
V = -Ua cos (Ψ + β) + Vp (north/south)
W = -Ua sin (Ө - α) + Wp (vertical)
Simplified horizontal and vertical wind calculations
Ψ = aircraft true heading
β = aircraft sideslip angle
Ө = aircraft pitch angle
α = aircraft attack angle
Up, Vp, Wp are aircraft velocities
Ua = aircraft true airspeed
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Wind error sources/ corrections
• Inertial system drift – correct groundspeed with GPS
• True heading accuracy → 0.3º @ 100m/sec to obtain 0.5m/sec
• Phasing/lags of input variables (e.g. pitch, attack, heading) especially in maneuvering flight
• Static/dynamic pressure corrections –static defect:
Pstatic + Pdynamic = Ptotal , where Pdynamic= Qc = 1/2ρV2
• Radome attack/sideslip calibration nonlinearities due to radome shape and flow distortion. In-flight calibration maneuvers.
• Offsets/drift in attitude angles – pitch, roll, yaw
• Total temperature dynamic heating/recovery error in TAS calculation
• Other random and bias errors in instrumentation, data system, etc.
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Spectra from TREX Calibration Flight - ~ 1000’ AGL
Longitudinal wind component Lateral wind componet
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Spectra (continued)
Sample-rate QC, Attack, Sideslip (25 Hz)
7 Hz
QCs
α,β
Vertical Wind Component
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“Speed Run” Maneuver Showing Static Pressure Defect with Airspeed
Correction Derived Using GV Air Data Computer as Reference Pressure
Uncorrected Ps
True Airspeed
Corrected Ps
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Reverse Heading Maneuver – Look for Averaged Wind Offset
True Heading
Wind Speed (Blue Line)
WS= 15.8 m/sWS= 15.4 m/s
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“Pitch” Maneuver to Determine Vertical Wind Phasing
and Calibration
Vertical wind
GV Vertical Wind
Pitch
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• Determine Static Pressure Defect Using Alternate Methods (i.e., differential GPS, Trailing Cone)
• Determine Total Temperature Recovery Factor Over the GV Flight Envelope
• Determine and Implement Corrections for Instrumentation Phase and Time Lag Offsets (Especially Important for High Rate Data)
• Implement GPS enhanced Inertial Winds Algorithm
• Improve Aircraft True Heading Accuracy with Differential GPS and/or Higher Accuracy Inertial System
• Continue to “Fine Tune” Radome Sensitivity Coefficients and Calibrations
• Development of Other Wind Measurement Technologies (e.g., Wing Pod All-weather Wind System, Laser Air Motion System)
Ongoing Work and Future Enhancements