The concept of circulation control was successfully demonstrated in flight using an A-6 aircraft. Circulation control can provide an aircraft with STOL performance of heavy lift capability. For ship based Naval aircraft the lower takeoff and landing velocities result in reduced deck gear and wind over the deck requirements. Circulation control airfoils can be mechanically less complex and lightweight compared to multi-element high lift airfoils

Harris, M. J.

Nichols, J. H.

English

NASA Technical Reports Server

N88-17607
FIXED WING CCW AERODYNAMICS
WITH AND WITHOUT SUPPLEMENTARY
THRUST DEFLECTION
J. H. Nichols and M. J. Harris
Department of the Navy
David Taylor Naval Ship Research and Development Center
(No paper received; presentation material only)
PRECEDING
479
https://ntrs.nasa.gov/search.jsp?R=19880008223 2020-03-20T08:17:45+00:00Z
ORIGINAL PACE IS 
OF POOR QUALITY 
DEVELOPMENT OF ADVANCED 
HIGH LIFT SYSTEMS 
I. Development of high-lift airfoils employing circulation control has been 
underway at the David Taylor Naval Ship Research and Development Center (DTNSRDC) 
since 1969. 
concepts, like circulation controlhpper surface blowing, are also being developed. 
This presentation will review the highly successful flight demonstration of circula- 
tion control on a Navy/Grumman A-6A aircraft and provide an overview of the continu- 
ing evolution of circulation control airfoils for fixed-wing applications. 
Hybrid systems which combine circulation control with propulsive-lift 
480 
ORIGINAL PAGE IS 
OF POOR QUALITY 
A-6 CIRCULATION 
CONTROL WING 
11. In 1979 a modified A-6A aircraft demonstrated the STOL capability of 
circulation control. 
concept flight demonstration. Externally the modifications included: a tapered 
cylindrical wing trailing edge, bleed air cross-over duct under fuselage, Krueger 
flap on the wing gloves, modified leading edge slats and modified horizontal tail. 
This aircraft is shown as it was modified for this proof-of- 
481 
CCW TRAILING EDGE APPLIED 
TO A-6 FLIGHT DEMONSTRATOR WING SECTION 
SPOILER 
SLAT 
CCW TRAILING EDGE 
U 
111. The A-6/circulation control airfoil used in the flight demonstration is 
Air bled from the fifth and twelth compressor stages shown here in cross section. 
of the two J52-P-8B turbojet engines on the A-6 is ducted along the wing span in the 
cylindrical trailing edge. 
passes through the plenum and is ejected out through a thin slot in the aft upper 
surface of the airfoil. 
trailing edge, due to the Coanda effect, and flows down around this surface. The 
jet sheet provides boundary layer control and significant augmentation of the lift 
generated by the wing. 
The bleed air exits the cylindrical trailing edge, 
The thin jet sheet from the slot adheres to the cylindrical 
482 
A-6/CCW
S TOL PERFORMANCE
85% INCREASEIN CLMAX
35% REDUCTION IN POWER-ONAPPROACHSPEEDJ
65% REDUCTION IN LANDING GROUND ROLL
30% REDUCTION IN LIFT OFF SPEED
60% REDUCTION IN TAKEOFFGROUNDROLL
75% INCREASEIN PAYLOAD/FUELAT TYPICAL
OPERATING WEIGHT (EW = 28,f'_ LB.)
BASEDON FLIGHTDEMONSTRATIONRESULTS
TOGW -- 35,700LB., LGW = 33,000LB.
CORRECTEDTO SEALEVEL,STANDARDDAY
A-6
(300 FLAPS)
(REF)
2.1
118 KTs.
(CL = 1.49)
2450 FT
120 KTS
(CL = 1.41)
1450 FT
45,000 LB.
A-6/CCW
3.9 (C/_= 0.30)
76 KTS
(0.75 PMAX' C/_=0.14, CL=2.78)
900 FT
82 KTS
(0.6 PMAx,CF.=0.04, CL=2.16)
600 FT
58,000 LB.
IV. Based on results from the flight demonstration, the A-6/circulation
control aircraft achieved an 85-percent increase in maximum lift coefficient when
compared to a standard A-6 with Fowler flap deflected 30-deg. This increase in lift
coefficient was used to reduce the power-on approach velocity by 35-percent which
results in a 65-percent reduction in landing ground roll. During takeoff the
increase in lift coefficient provides a 30-percent reduction in lift off velocity
which resul_s in a 60-percent reduction in takeoff ground roll. Alternatively, at a
takeoff velocity of 120 knots the 85-percent increase in maximum lift coefficient
can provide a 75-percent increase in payload/fuel weight.
483
CCW CONFIGURATION DEVELOPMENT
I I
f _ A-61CCW
A-6 DUAL RADIUS FLAP
THIN T.E. SUPERCRITICAL/CCW
V. The radius of the cylindrical trailing edge used in _ne flight demonstra-
tion was 3.65-percent of the local wing chord. This relatively large surface could
not remain deployed during cruise flight. Several concepts were proposed for con-
verting this airfoil from the high-lift configuration to the cruise configuration.
These concepts included: inflatable trailing edges, flaps which rotate nearly 180-
deg exposing the cylindrical surface and complex mechanical systems which rotate or
translate the cylindrical surface forward into the airfoil
Two mechanically simple alternatives to the large radius trailing edge used in
the flight demonstration, which are being developed at DTNSRDC, are the dual radius
circulation control flap and circulation control trailing edges with a radius small
enough so it can remain deployed and still have minimal impact on cruise flight.
484
70
60
50
40
30
CCW AIRFOIL PERFORMANCE
2.0
1.0
LIFT PERFORMANCE
a=0 °
0.018C
S_NASA,_ _
S-31CCW \ / _.-_
y/-_.. 0.072 c
h,' .. _-s!cc__w__ t
.._1 (LOW SPEED '
_/// CONFIGURATION)
_P
t 0.008c
I I I
0 0.1 0.2 0.3 0.4
C_
2.0
1.5
1.0
0.5
CRUISE PERFORMANCE
0.008c
'S NASA 17% __
UPERCRITICALL _..- -_'--_ _
c _-o
x,,, °.o,8°
t
S-3/CCW
I I I
0.01 0.02 0.03 0.04
Cd
VI. The concept of a circulation control trailing edge which has a base thick-
ness less than two-percent of the wing chord was successfully demonstrated on a
supercritical airfoil. Wind tunnel investigations have confirmed the capability of
this combination of supercritical airfoil and small radius circulation control
trailing edge to achieve, at STOL velocities, lift coefficients equivalent to the
lift coefficient achieved in the A-6/circulation control flight demonstration. This
combination also results in an airfoil which converts from high-lift configuration
to cruise configuration by simply terminating the flow of bleed air to the blowing
slot. Since this trailing edge remains deployed during cruise flight no retracting
mechanism is needed.
485
A-6/CCW
CRUISE CONFIGURED AIRFOILS
DUAL RADIUS CCW
CONVENTIONAL A-6 AIRFOIL
VII. A circulation control trailing edge with a radius of one-percent of the
wing chord was also evaluated on the A-6 airfoil along with the dual radius circula-
tion control flap. The dual circulation control flap is a short chord flap which,
when rotated from 60 to 90 deg, provides a circulation control trailing edge. The
dual radius flap currently being evaluated is 3.5-percent of the wing chord. Dual
radius refers to the two arcs which make the upper surface of this flap. In this
case the flap leading edge radius is one-percent of the wing chord and the flap
trailing edge radius is four-percent of the wing chord.
486
COMPARISON OF
BLOWN LIFT
AUGMENTATION
_rg=3 deg
dSlat =25 deg
C_
I I I I I
DUAL RADIUS CCW
dF=90 deg
A-6/CCW
DEMONSTRATOR /
3.6% RADIUS /
/
/
/
/
/
/ RADIUS
CCW
£JF=60 deg
1% RADIUS CCW
SINGLE SLOI-I'ED FOWLER FLAP
£JF=30 deg
I I 1 I I /
0.0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16
C
VIII. The A-6 airfoil with either the one-percent radius circulation control
trailing edge or the dual radius circulation control flap achieved lift coefficients
at relatively low blowing levels which are higher than can be achieved with a single
slotted Fowler flap deflected 30 deg. With the dual radius circulation control flap
deflected 90 deg, lift coefficients achievable at low to moderate blowing levels are
higher than the lift coefficients achievable with the large radius circulation
control trailing edge used in the flight demonstration.
487
CLEAN AIRFOIL COMPARISON
(NO BLOWING)
1.2
1.0 --
0.8 --
0.6 --
Cl' 0.4
0.2 __0.0
I
-0.2 -/
I 1 1 I
DUAL RADIUS __.
_
///
d/,_,_1o,o,_,o,os
/_/ -'"°;_'w'°°
Iii
_/ A_'//co_w_',O_L _
/
I I [ [
-4 0 4 8 12 16
_r, deg
I I I I I I
DuALRADIUs_" -.--"- -
- CCW/ _1.-"f -
X/| I 1_ RADIUS
i \ _ ccw .
- \ -
\ ,. ,,.
\
\
_ \
t I I I I I
0.004 0.006 0.008 0.010 0.012 0.014 0.016
Ca
IX. The mechanical system required to rotate the dual radius circulation con-
trol flap would be equivalent to the system required for a simple single slotted
Fowler flap. The undeflected dual radius circulation control flap would have no
significant impact on cruise performance. The dual radius flap provides a means of
mechanically varying the wing chamber independent of the circulation control
blowing.
The impact of the one-percent radius circulation control trailing edge on
cruise performance is significant enough to require that this surface be retracted
during cruise flight. Retracting the small radius circulation control trailing edge
would be considerably simpler than the large radius surface used in the flight
demonstration.
488
Conclusions:
The concept of circulation control has been successfully demonstrated in flight
using an A-6 aircraft.
Circulation control can provide an aircraft with STOL performance of heavy-lift
capability.
For ship based Naval aircraft the lower takeoff and landing velocities result
in reduced deck gear and wind-over-the-deck requirements.
Circulation control airfoil can be mechanically less complex and light weight
compared to multi-element high-lift airfoils.
489


Fixed wing CCW aerodynamics with and without supplementary thrust deflection

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