UH-60A Airloads Wind Tunnel Data Update"

Tom Norman"

Airloads Workshop – August 9, 2012"

Outline"

•  Data Availability"•  Publications"•  Recent Test Findings"•  Current Activities"•  Wind Tunnel/Flight Test Comparisons"

2"

Data Availability"

•  Selected wind tunnel data made available to Workshop participants Nov 2011"–  Includes speed sweep (8 pts) and thrust sweep (12 pts)"–  Data accessible through NASAʼs NSC Knowledge Now

website https://nsckn.nasa.gov/community/Views/Home.aspx?Filter=930"

•  8 organizations currently have approved access (NASA, Army, Sikorsky, Bell, Boeing, Penn State, CDI, Georgia Tech)"

3"

Publications Since March 2012"

•  6 conference papers at 2012 AHS Forum "–  Aero/Structural Loads"

•  “Loads Correlation of a Full-Scale UH-60A Airloads Rotor in a Wind Tunnel”, Yeo et al"

•  “Evaluation of Wind Tunnel and Scaling Effects with the UH-60A Airloads Rotor”, Norman et al"

–  High Advance Ratio"•  “Investigation of Performance and Loads of a UH-60A Rotor at High

Advance Ratios”, Yeo"•  “Computational Investigation and Fundamental Understanding of a

Slowed UH-60A Rotor at High Advance Ratios”, Potsdam et al"–  Experimental Capabilities"

•  “Wind Tunnel Measurements of Full-Scale UH-60A Rotor Tip Vortices”, Yamauchi et al"

•  “Blade Displacement Measurement Technique Applied to a Full-Scale Rotor”, Abrego et al"

4"

Recent Test Findings"

•  From March 2012 Meeting"–  LRTA control system stiffness measured - similar to aircraft

(somewhat stiffer under collective loading)"–  As-tested blade tab angles measured – similar to flight

measurements"–  7 deg azimuth difference identified between wind tunnel data

and currently used CFD model"•  Must correct model or data for valid comparisons"•  Also identified azimuthal “errors” with flight test data due to anti-

aliasing filter corrections"•  New information"

–  Post-test blade inspections identified error in locations of TE blade pressure transducer"

•  All TE transducers actually at x/c=93.9% instead of 96.3%"•  Effect on flight test airloads (correct value used for WT) is minimal

for normal flight condition"

5"

Current Activities"

•  Continuing data evaluation efforts for blade pressures and integrated parameters"

•  Making progress with PIV and Blade Displacement data reduction efforts"–  PIV processing procedures nearly finalized; significant

data reduction to begin this CY"–  Initial comparisons of blade displacement measurements

with CFD helping to identify necessary improvements in data reduction"

•  Continuing CFD validation efforts with both OVERFLOW and FUN3D"

6"

•  Completed coupling of hi-res CAMRAD with OVERFLOW"

•  Currently modeling in-board blade shank for better performance calculations"

•  Using wind tunnel and LRTA models to investigate effects on rotor loads and performance"–  Also investigating differences between wind tunnel and

flight test measurements"

7"May 3, 2011"

OVERFLOW"

•  Troubleshooting coupling of hi-res CAMRAD with FUN3D (working with Romander)"

•  Developed model for LRTA fuselage and preparing for computations"

•  Preparing to perform detailed validation with thrust sweep data"

8"May 3, 2011"

FUN3D"

Near-Term Plans"

•  Continue data evaluation/correction and database updates"–  Pressures/integrated loads – complete remaining runs"–  Blade motion measurements – correct for RPM effects and

transducer drift (mean effects)"–  Slowed Rotor runs – account for blade gage coupling and

rotor balance drift"•  Continue analysis of PIV and Blade Displacement data"•  Complete documentation of control stiffness testing and

tab deflection measurements"•  Investigate blade contour measurements"•  Investigate measured dynamic hub loads; evaluate

rotor balance calibration issues"9"

•  Full-scale UH-60A Airloads wind tunnel test conducted in USAF National Full-Scale Aerodynamic Complex (NFAC) 40- by 80-Foot Wind Tunnel (2010)"

•  Test provided unique opportunity to evaluate tunnel and scaling effects by comparing acquired data with"–  1994 UH-60A Airloads flight test"–  1989 UH-60A Airloads small-scale wind tunnel test in German-Dutch

Wind Tunnel (DNW)"

10"

Background"

11"

Flight Comparisons - Airloads"Flight (c8424)"

Section Normal Force (M2cn)"µ=0.30, CT/!=0.088"

V∞"

•  NFAC baseline matches well with flight, although noticeable differences outboard"

12"

Flight Comparisons - Airloads"NFAC "

Section Normal Force (M2cn)"µ=0.30, CT/!=0.088"

Flight (c8424)"Section Normal Force (M2cn)"

µ=0.30, CT/!=0.088"

V∞" V∞"

•  NFAC baseline matches well with flight, although noticeable differences outboard"

13"

Flight Comparisons - Airloads"Difference between Flight and NFAC"

Section Normal Force (M2cn)"µ=0.30, CT/!=0.088"

V∞"

•  Biggest differences near negative lift peak and on retreating side for outboard stations"

14"

Flight Comparisons - Airloads"Section Normal Force – µ=0.30, CT/!=0.088 (c8424)"

r/R=0.400" r/R=0.920"

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 90 180 270 360

NFACFlight Test

Nor

mal

For

ce, M

2 c n

!, deg

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 90 180 270 360

NFACFlight Test

Nor

mal

For

ce, M

2 c n!, deg

•  NFAC flap bending and torsion match well with flight"

15"

Flight Comparisons – Structural Loads"Blade Bending Loads – µ=0.30, CT/!=0.088"

Flap Bending, r/R=0.60" Torsion, r/R=0.30"

-0.0002

-0.0001

0

0.0001

0.0002

0 90 180 270 360

NFACFlight Test

Flap

Ben

ding

!, deg-0.0001

-5 10-5

0

5 10-5

0.0001

0 90 180 270 360

NFACFlight Test

Tor

sion

!, deg

•  NFAC flap bending and torsion match well with flight"•  NFAC chord bending shows significant differences"

16"

Flight Comparisons – Structural Loads"Blade Bending Loads – µ=0.30, CT/!=0.088"

Flap Bending, r/R=0.60" Torsion, r/R=0.30" Chord Bending, r/R=0.60"

-0.0002

-0.0001

0

0.0001

0.0002

0 90 180 270 360

NFACFlight Test

Flap

Ben

ding

!, deg-0.0001

-5 10-5

0

5 10-5

0.0001

0 90 180 270 360

NFACFlight Test

Tor

sion

!, deg-0.0006

-0.0003

0

0.0003

0.0006

0 90 180 270 360

NFACFlight Test

Cho

rd B

endi

ng

!, deg

•  Notable differences at 1, 2, 4, and 5/rev"–  1 and 2/rev differences consistent with damper responses"–  4 and 5/rev may be caused by differences in lag modal frequencies (drive

train differences)? "17"

Flight Comparisons – Structural Loads"Chord Bending Harmonics – µ=0.30, CT/!=0.088"1/rev" 2/rev" 3/rev"

5/rev"4/rev"

0

0.0002

0.0004

0 0.2 0.4 0.6 0.8 1

NFACFlight TestM

agnitude

r/R0 0.2 0.4 0.6 0.8 1

r/R0 0.2 0.4 0.6 0.8 1

r/R

0 0.2 0.4 0.6 0.8 1r/R

0

0.0002

0.0004

0 0.2 0.4 0.6 0.8 1

Magnitude

r/R

•  NFAC measured rotor power compares well with matched flight and DNW test conditions"–  Procedures and trim targets used to match conditions are valid"

•  Flight comparisons"–  Airloads match well although some waveform differences found at

outboard stations"–  Rotor structural loads match well except for chord bending"–  Further investigation necessary to determine cause of differences"

18"

Conclusions"

19"

20"

Backup Slides"

Blade Tab Angles"

•  Re-measured tab deflections on all 4 blades"•  New measurements similar to flight test"•  Tab angles dependent on location of tab bend radius and location of

measurement"–  Approx location of bend radius 0.8 in from TE"–  Approx location of measurement .15 in from TE"

•  Tab angles vary from 0.3 to 3.6 deg up"

21"

Azimuthal Diff. Between Flight and Wind Tunnel"•  Known 7 deg azimuth ref. difference between wind tunnel and flight

PdB files"

22"

7.0°

+"#

Wind Tunnel (and TRENDS) azimuth reference

Rotor (hub) shown at 0° azimuth, blade shown at 0° lag angle

+$P#

+%P

7.0°

Flight PDB azimuth reference

Rotor (hub) shown at 0° azimuth, blade shown at 0° lag angle

Azimuthal Diff. Between Flight and Wind Tunnel"•  Looked at possible causes for additional azimuthal differences "

–  Encoder issues, post-processing errors, etc"•  Found that wind tunnel data were corrected for phase delays caused by

anti-aliasing filters; flight data were not"–  High speed data, 550 Hz Butterworth filter; approximately 1.8 deg delay"–  Low speed data, 110 Hz Butterworth filter, approximately 8.6 deg delay"

•  Also need to account for flight sideslip angle for comparisons (up to 4 deg)"

23"-0.00015

-0.0001

-5 10-5

0

5 10-5

0.0001

0.00015

0.0002

0 60 120 180 240 300 360

MRNB20_ND_FTMRNB60_ND_FTMRNB20_ND_WTMRNB60_ND_WT

CNB/s

AZIMUTH, deg

C8525

Flight/Wind Tunnel Flap Bending (Flight corrected for phase)