HIAPER 3D Winds – current status

- Dick Freisen -

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

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.

Spectra from TREX Calibration Flight - ~ 1000’ AGL

Longitudinal wind component Lateral wind componet

Spectra (continued)

Sample-rate QC, Attack, Sideslip (25 Hz)

7 Hz

QCs

α,β

Vertical Wind Component

“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

Reverse Heading Maneuver – Look for Averaged Wind Offset

True Heading

Wind Speed (Blue Line)

WS= 15.8 m/sWS= 15.4 m/s

“Pitch” Maneuver to Determine Vertical Wind Phasing

and Calibration

Vertical wind

GV Vertical Wind

Pitch

• 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