Configuration Aerodynamics of the ASW 22 BL Sailplane
Rodney Bajnath, Beverly Beasley, Mike Cavanaugh AOE 4124 Configuration Aerodynamics April 21, 2004
Alexander Schleicher company web site: www.alexander-schleicher.de
ASW 22 BL Specifications
Wing Span: 86.6 ft Wing Area: 179.4 ft2 Aspect Ratio: 41.8 Mean chord: 2.07 ft Airfoils: HQ17/14.38 (root) DU84-132/V3 (tip) BLC: 860 blow holes lwr surface 75%c, flap root to tip
Max T-O Weight: 1654 lbs. Payload: 198 lbs. Water Ballast: 452 lbs. W/SMAX = 9.22 lbs./ft2
Conventional controls: ailerons (inner & outer), elevator, rudder Double panel air brake (upper surface only) Two wheel retractable main landing gear, fixed tail wheel Cruise flaps (flap + inner aileron): +9.2 (thermaling), -0.5, -7.7, -10.7 Landing flaps: flap +40, inner aileron +14, outer aileron -8
Alexander Schleicher company web site: www.alexander-schleicher.de Fred Thomas, Fundamentals of Sailplane Design, 1999. Dick Johnson, A Flight Test Evaluation of the AS-W22, Soaring, April 1983.
Three Types of Soaring
Thermal circle in rising current
of warm air
Ridge fly in updraft on
windward side of ridge
Wave fly in updraft portion of
wave on lee side of mountain
Goal:
sink less than the air rises
Result: climb & fly to next thermal!
Soaring Flight Manual, Soaring Society of America, 1992. Photos, World Championships, Uvalde, Texas, 1991.
ASW 22 BL Factory Speed Polar
0 0 -100 -200 20 40 60 80 100 120 140
sink (ft/min)
-300 -400 -500 -600 -700
1 L/D = tan !
540 kg (1191 lbs) 750 kg (1654 lbs)
knots
Min. sink: 79 fpm @ 43.2 KCAS (1191 lbs. / CL = 1.05) Best glide: 64.85 @ 59.4 KCAS (1654 lbs. / CL = 0.77) Max Speed: 151 KCAS Stall Speed: 35.3 KCAS (light A/C) 41.5 KCAS (heavy A/C) (Flaps 9 / CLmax = 1.58)
Alexander Schleicher company web site: www.alexander-schleicher.de Dick Johnson, A Flight Test Evaluation of the AS-W22, Soaring, April 1983.
Quest for Low Drag Drives Aerodynamic Configuration of Open Class Sailplanes
Large span low span loading (minimize induced drag) for a fixed weight Minimum fuselage size to accommodate pilot - reduce wetted area Laminar flow airfoils on wing, vertical tail & horizontal tail low skin friction Laminar flow on fuselage - low skin friction Smooth composite construction reduce drag of surface imperfections Boundary layer control on wing - fix transition and eliminate laminar bubbles Cruise flaps adjust span & chord loading for a range of flight conditions Retractable landing gear reduce pressure drag from gear and open doors Winglets - minimize induced drag in climbs Long tail moment arm reduce horizontal tail area, min downwash at tail Aft center of gravity placement reduce trim drag Water ballast adjust speed for maximum L/D, improve penetration
ASW 22 Planform Analysis
Tornado Model
ASW 22 Planform Analysis
Without Winglets
AR = 38.3 b = 25.0 m e = 0.95 L/Dmax = 60 W/Smax = 9.42 lb/ft2
With Winglets
AR = 41.8 b = 26.58 m e = 0.99 L/Dmax = 62 W/Smax = 9.21 lb/ft2 Improved stall Better roll rate Lower induced drag
ASW 22BL Trim Analysis
Tornado dCm/dCL Cmo -0.410 0.0 JKay -0.203 0.0 VLMpc -0.368 0.0
ASW 22BL Elevator Effectiveness
1 0.5
Cm
0 -0.5 -1 -1.5 -2 -0.5 0 0.5 1 CL 1.5 2 2.5
ASW 22BL Stability and Control
Longitudinal
Tornado
Lateral-Directional
DATCOM
JKay
VLMpc
Tornado
JKay
DATCOM
CL_ Cm_ Cm_e
6.30 -1.48 -1.70
7.22 -1.47
4.89 -1.80
6.34
Cn_
0.79 -0.02
0.011 -0.004
0.039 -0.21
-2.36 Cl_ -1.96
The ASW 22BL is stable for all major flight conditions.
XFOIL Wing Airfoil Analysis
Favorable pressure gradient to promote laminar flow Airfoil analysis at CL for best L/D (59.4 KCAS @ 1654 lbs.)
Mark Drela, XFOIL 6.9 User Guide, 2001.
XFOIL Wing Airfoil Analysis
Skin friction plot shows presence of laminar separation bubbles on the upper and lower surface where cf goes to zero
Shape factor (_*/_) increases dramatically due to transition and the presence of the laminar bubbles
XFOIL Wing Airfoil Analysis
Boundary layer profiles show reverse flow in the bubble region Blowing used to fix transition and eliminate bubble 430 holes (0.0225 diameter) located on bottom of each wing 73%~71% chord just in front of flap and aileron hinge lines 20 mm spacing running from flap root to tip of aileron Four inlet pitot tubes supply pressurized air to blowing holes
Lower wing surface
turbulent profile reverse flow in bubble laminar profile
XFOIL Wing Airfoil Analysis
Polar with upper and lower surface laminar separation bubbles present At max L/D speed (CL=0.773), trips at 0.65c on the upper surface and 0.77c on the lower surface reduce airfoil Cd by 4.9 counts
Drag Polar Extracted from Company Speed Polar
CD extracted from company speed polar using L/D = 1/tan! Data for the heavy aircraft (1654 lbs.) at 5,000 ft.
1.80 1.60 1.40 1.20 1.00
CL
0.80 0.60 0.40 0.20 0.00 0.0000
L/D =
1 tan !
0.0400 0.0450
0.0050
0.0100
0.0150
0.0200
0.0250
0.0300
0.0350
CD
Drag Breakdown
Attempt to match polar derived from Schleicher company data
1.20
1.00
0.80
Schleicher Cd fuselage Cdf wing
CL
0.60
Cdp wing Cd HT Cd VT
0.40
Cd induced
0.20
0.00 0.0000
0.0050
0.0100 CD
0.0150
0.0200
0.0250
Independent Flight Test Verification of Performance
Flight test of the original ASW 22 by Dick Johnson and David Jones in 1983 Appeared in the April 1983 issue of Soaring Magazine Plot shows amount of scatter in performance flight test data Plot shows flap scheduling suggested by Schleicher Performance of later 22B and 22BL models improved with increased span and winglets
Dick Johnson, A Flight Test Evaluation of the AS-W22, Soaring, April 1983.
ASW 22 BL Stability & Control Analysis
D(#) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Stability Derivatives CLAlpha CDAlpha CmAlpha CLAlphadot CmAlphadot CLq Cmq CLM CDM CmM CLDeltaM CDDeltaM CMDeltaM CTV CTDeltaT CyBeta ClBeta CnBeta Clp Cnp Cyp Clr Cnr Cyr ClDeltaL CnDeltaL ClDeltaN CnDeltaN CyDeltaN DATCOM /rad /deg 6.3259 0.0979 -1.2551 0.5129 -3.9800 5.7499 -44.6196 0.0 0.0 0.0 0.2528 0.0056 -1.9618 0.0 0.0 -0.2824 -0.2064 0.0392 -0.9658 0.1174 -0.0082 0.1676 -0.0277 0.0840 0.6251 -0.0194 0.0019 -0.0194 0.1099 Tornado /rad /deg 0.109885 0.001539 -0.025724 0.251209 -0.806028 0.004210 0.000163 -0.030192 0.073614 0.000346 0.014136 -0.012801 -0.003336 -0.002502 0.002380 0.005836 0.030504 0.004766 0.000179 -0.000739 0.007743 0.042030
Phys(#) 1 2 3 4 5 6 7 8 9
Reference weight Ixx Iyy Izz Ixz Area Span Chord Thrust Angle 1653.75 10780 626 11396 0 179.37 86.62 2.067 0
units lbs slug-ft^2 slug-ft^2 slug-ft^2 slug-ft^2 ft^2 ft ft rad
0.110400 6.2964 0.001709 0.0882 -0.021903 -1.4740 0.008951 -0.069459 0.100347 14.3943 -0.778702 -46.1854 0.0 0.0 0.0 0.004412 0.2412 0.000097 0.0093 -0.034237 -1.7300 0.0 0.0 -0.004928 4.2181 -0.003602 0.0198 0.000685 0.8100 -0.016854 -0.7335 0.002048 -0.1912 -0.000143 -0.1434 0.002926 0.1364 -0.000484 0.3344 0.001466 1.7479 0.010909 0.2731 -0.000338 0.0102 0.000033 -0.0424 -0.000338 0.4437 0.001918 2.4083
Ref(#) 1 2 3 4 5 6
Condition density TAS Mach CL CD gamma 0.002048 107.94 0.098 0.773 0.01191 -0.01542
units slugs/ft^3 ft/s trim trim radians
c.g. @ 42.5%c
Stability derivatives and reference conditions for analysis
Jan Roskam, Airplane Design Book VI, 1990.
ASW 22 BL Stability & Control Summary
Longitudinal static stability positive Stick-fixed neutral point location: 0.66c Tornado / 0.62c DATCOM C.G. location calculated to be 42.5%c at maximum take-off weight Static lateral/directional stability positive CN_> 0: Tornado (sign change needed) & DATCOM CL_< 0 dihedral effect: Tornado (sign change needed) & DATCOM Lateral/directional control Rudder power: _ degree of sideslip per degree of rudder deflection Steady state roll rate 17.02 deg/sec at 45 knots (Johnson flight test value 11.25 deg/sec) Dick Johnson flight test reports moderately strong adverse yaw Longitudinal Dynamic Stability
Mode phugoid short period ! -0.00033 0.71326 "d (rad/s) "n (rad/s) 0.3127 2.8114 0.3127 4.0111 f (Hz) 0.0498 0.4474 T (sec) 20.0933 2.2349
Lateral/Directional Dynamic Stability
Mode dutch roll spiral roll ! 0.16144 "d (rad/s) "n (rad/s) 0.6143 0.6225 f (Hz) 0.0978 T (sec) 10.23 T2 (sec) 84.47 0.1025
Dick Johnson, A Flight Test Evaluation of the AS-W22, Soaring, April 1983.
T1/2 (sec)
Conclusions
Pro Performance, low min sink (79 fpm) and high glide ratio (L/D 64.85) Variable wing loading with jettisonable water ballast. Good penetration on strong days and low minimum sink on weak days Wing extensions and winglet add-ons provide versatility ASW 22BL an improvement over ASW 22 and ASW 22B because of higher L/D and span efficiency (as evidenced by flight testing) Stable configuration Winner of 6 World Championships! Con Ground handling difficult due to large span (TEU aileron deflection) Flight test report of moderately strong adverse yaw Complexity (boundary layer control) Technology is 10 years old, current max L/D now in low to mid 70s Price: $144,339 US / Eastern Sailplanes, Waynesville, OH
References
Alexander Schleicher company web site, www.alexander-schleicher.de Fred Thomas, Fundamentals of Sailplane Design, College Park Press, College Park Maryland, 1999. Richard H. Johnson, A Flight Test Evaluation of the AS-W22, Soaring Magazine, April 1983. Soaring Flight Manual, Private and Commercial, Soaring Society of America, Jeppesen Sanderson, Inc., 1992. Mark Drela, XFOIL 6.9 User Guide, MIT Aero & Astro, 2001. Jan Roskam, Airplane Design Part VI: Preliminary Calculation of Aerodynamic, Thrust and Power Characteristics, Roskam Aviation and Engineering Corporation, Ottawa Kansas, 1990.
