1. Statistical Validation of Calibrated Wind Data Collected From NOAA’s Hurricane Hunter Aircraft
Kelly Graham, Department of Earth and Atmospheric Sciences, SUNY College at Oneonta
Ian T. Sears, Mike Holmes, Richard G. Henning, A. Barry Damiano, Jack R. Parrish, Paul T. Flaherty, Aircraft Operations Center, National Oceanic and Atmospheric Administration
Introduction
Methodology
Results
Overview:
Flight parameters from netCDF files for all flights from were downloaded and imported to a PostgreSQL database
From the database, scripts programmed in R extracted specific parameters used in our alternate derivation method
Attack Angle Values
Slip Angle Values
The mission of NOAA’s Office of Marine and Aviation Operations is “to safely deliver effective Earth observation capabilities, integrate emerging technologies, and provide a specialized, flexible, and reliable team responsive to NOAA and the Nation.” The OMAO’s Aircraft Operations Center in Tampa, Florida, serves its goal of generating and providing accurate and reliable data to the scientific community.
In August 2012, damage was found on the vertical stabilizer component of the tail of NOAA’s Gulfstream-IV, the high altitude Hurricane Hunter aircraft responsible for gathering in-situ measurements and deploying dropsondes to collect a plethora of meteorological data. One suspected cause of the damage were the yaw maneuvers conducted during wind calibration flights. Since July 2012, a wind calibration has not been performed due to the risk of further damage. Since wind calibration flights are necessary and performed annually, an alternate method to the calibration of these in-situ meteorological measurements is needed. This project focuses on an alternate method to wind derivations.
Year
Slope
Intercept
R value
2012
6.934
5.214
0.019
2013
3.794
4.675
0.007
2014
6.25
5.121
0.822
2015
6.179
5.128
0.806
Year
Slope
Intercept
R value
2012
5.114
0.705
0.009
2013
9.962
-0.05
2014
5.777
-0.021
2015
1.238
-0.397
Alternate Derivation Method
Our hypothesis stated that G-IV wind measurements could be computed from producing linear regression models of attack ratio vs. aircraft pitch and slip ratio vs. drift angle, and then extracting attack angle and slip angle slopes and intercepts from over 140 flights collected from the aircraft system’s raw data. This would allow for wind speed and wind direction to be empirically derived using the attack and slip angle slopes and intercepts, and thus, we would be able to derive wind measurements using previous flight data.
2012 Wind Results
WS Difference Between Empirical Calculation and Aircraft Data System
WS Ratio Between Empirical Calculation and Aircraft Data System
WD Ratio Between Empirical Calculation and Aircraft Data System
Wind Calibration Flight – 19 July 2012, Results
WD Difference Between Empirical Calculation and Aircraft Data System
With the derived 2012 attack and slip angles not far from the wind calibration flight results, wind derivations held promise. However, 2013, 2014, and 2015 wind speed and direction derivations were highly skewed and did not correlate at all with aircraft data system measurements.
G-IV Wind Calibration Procedure
A wind calibration flight is necessary to ensure the quality of G-IV wind data to the scientific community. Wind calibration maneuvers provide a wide range of data that measure many in-flight parameters. This data is needed to compute slopes and intercepts for the attack angles and sideslip angles, which are then used to derive horizontal and vertical winds. The wind calibration maneuvers are to be flown in clear, non-turbulent, near homogeneous air.
Attack Angle (AA) Equation
AA = aas*pdalpha/pqalpha + aai
aas = attack angle slope
aai = attack angle intercept
pdalpha = differential attack pressure
pqalpha = dynamic attack pressure
Slip Angle (SA) Equation
SA = sas*pdbeta/pqbeta + sai
sas = slip angle slope
sai = slip angle intercept
pdbeta = differential slip pressure
pqbeta = dynamic slip pressure
2013 Wind Results
Slip Ratio vs. Drift Angle
WS Ratio Between Empirical Calculation and Aircraft Data System
WD Ratio Between Empirical Calculation and Aircraft Data System
Analysis
Flight Maneuvers:
Racetrack Legs
Yaw Maneuver*
Concentric Circles
Pitch Maneuver*
For wind calibrations, yaw and pitch maneuvers need to be considered to compute attack angle and sideslip angle.
After successfully proving the alternate derivation method with the wind calibration flight dataset, we expanded our data to include each year from 2012 to 2015 (over 140 flights). This would allow future data to be calibrated using past data. The following was executed:
Computed attack angle and slip angle equations using the same method as above for 2012, 2013, 2014, and 2015.
Using the computed results, the new attack angles and slip angles were fed in to the equations to the right.
Wind speed and direction data was plotted as a difference between the empirically derived data and the aircraft data systems computation.
Wind Derivation
TX, TY, TZ – true airspeed components
PC = pitch, RL = roll, HD = heading
TXA=TS/sqrt(1+tan(AA)*tan(AA)+tan(SA)*tan(SA))
TYA = -TXA*tan(SA)
TZA = -TXA*tan(AA)
TXR = TXA
TYR = TYA*cos(RL) – TZA*sin(RL)
TZR = TYR*sin(RL) + TZA*cos(RL)
TXP = TXR*cos(PC) – TZR*sin(PC)
TYP = TYR
TZP = TXR*sin(PC) + TZR*cos(PC)
TX = TXP*sin(HD) – TYP*cos(HD)
TY = TXP*cos(HD) + TYP*sin(HD)
WX, WY – Horizontal Wind Components
WX = GSx – TX
WY = Gsy – TY
Wind Speed, WS = sqrt(WX² + WY²)
Wind Direction, WD = (180/pi)*atan2(WY,WX)
Pitch Maneuver
Requirements:
45,000 feet
0.77 Mach
5 cycles of ±5°
Conclusions & Future Work
Derivation of slip angle as part of the wind calibration process is not yet possible using this method. The 2013, 2014, and 2015 slip angle slopes and intercepts were not close to matching the wind calibration flight results. With more work, slip angle results can be improved. Since attack angle derivations held promise in correlating with aircraft data system results, this method still holds promise. A new method of deriving slip angle slopes and intercepts is needed. Potential solutions to this problem include:
Limiting upper and lower quartiles of data, thus increasing the correlation coefficient
Restrict data calibration regimes to omit light and variable wind scenarios
Conduct a larger analysis
Yaw Maneuver
Requirements:
40,000 feet
0.77 Mach
3 cycles of ±5°
Since the yaw maneuver is currently under review, an alternate method to calibrating G-IV wind measurements is needed. Can G-IV wind measurements be derived without performing a wind calibration procedure, using previous flight data as a means of calibration? This poster illustrates the first attempt at solving this problem.