Double hinged flap for boundary layer control over trailing edges of wing

Turner, T. R.

English

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REPLY ro 
ATTN OF: GP 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
October 16, 1970 
TO : USI/Scien t i f ic  & Technical Information Div i s ion  
Attent ion:  M i s s  Winnie M. Morgan 
FROM t GP/Office of A s s i s t a n t  General  
Counsel f o r  Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U,S. Pa ten t s  i n  STAR 
I n  accordance wi th  t h e  procedures contained i n  t h e  Code GP 
t o  Code US1 memorandum on t h i s  subject, dated June 8, 1970, 
t h e  a t tached  NASA-owned U.S, patent i s  being forwarded f o r  
a b s t r a c t i n g  and announcement i n  NASA STAR, 
The following information i s  provided: 
U.S, Pa ten t  No. 3,321,157 
Corporate Source : Langley Research Center 
Supplementary 
Corporate Source 
NASA P a t e n t  Case NO, : ~ ~ ~ - 0 1 2 9 0  
Gayle Parker 
Enclosure: 
copy of Pa ten t  
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( P A G E S 9  (CODE) 
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(CATEGORY) 
=! X (NASA CR OR TMX OR AD NUMBER) 
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May 23, 1967 1 T.R.TURNER 3,32 1,157 
DOWELEI HINGED FLAP 
Filed Aug. 31, 1964 
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20 
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FIG. 3 
I 
FIG. 4 
44 
FIG. 5 
I IO I 
I i2 BY 
INVENTOR 
THOMAS R. TURNER 
ATTORNEYS 
3,321,157 
Thomas W. Turner, Newport News, Va., aSSigEIQr to the 
United States of America as represented by the Ad- 
ministrator of the National Aeronauccs and Space 
AdminiStrathn 
Filed Ang. 31, 1964, Ser. No. 393,451 
8 Claims. (CL 244-42) 
The invention described herein may be manufactured 
and used by or for the Govrnment of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon or therefor. 
This invention relates generally to an aircraft and 
more particularly to boundary layer control over a wing 
having multiple flap segments. 
The operating cost of large aircraft and especially car- 
go transport aircraft is a function of the cruising lift-to- 
drag ratio which increases with aspect ratio. For higher 
aspect ratios, that is, where the span is large in order to 
obtain the necessary surface area, airflow separation oc- 
curs over the thick root section of the wing, which is re- 
quired for structural reasons. Obviously, deep chord 
sections and thick root sections limit the lift-to-drag ra- 
tios obtainable for large winged aircraft. The lower 
rift-to-drag ratios inherent in deep airfoil sections not 
only are uneconomical, but require considerable runway 
length for takeoff and landing of the aircraft. It has 
been found that a blowing slot suitably located on the 
upper surface of the airfoil controls flow separation and 
the drag may be reduced by more than the power required 
to operate the blowing slot. It is also well known that 
provision of flaps having considerable surface area in- 
creases the lift to enhance takeoff and landing characteris- 
tics of the aircraft. However, the prior art flap construc- 
tion is disadvantageous for a blowing4lap installation be- 
cause of the large break in the wing upper surface. 
The present invention, a flap comprised of two seg- 
ments individually pivoted to the wing and having a nar- 
row slot between the upper segment and the wing, over- 
comes the difficulties inherent in the prior art. Release 
of a high-pressure fluid from the slot controls the bound- 
ary layer and flow separation over the aft portion of the 
wing surface. Blowing high pressure air from the slot 
with the flap undeflected reduces separation over the aft 
portion of the airfoil resulting in a higher lift-to-drag 
ratio for more economical cruising. Blowing air from 
the same slot with the flap partially or  fully deflected 
increases the lift for takeoff and landing. 
It is an object of this invention to provide boundary 
layer control over a two-segment, double-hinged flap. 
Yet another object of the instant invention is to pro- 
vide boundary layer control over an airfoil having a thick 
root and large chord and a two-segment flap to increase 
the lift-to-drag ratio thereof and to increase the lift for 
takeoff and landing. 
A further object of this invention is to provide in- 
creased cruising lift-to-drag ratio and enhance the lift 
characteristic during takeoff and landing of relatively 
thick wings by blowing a high-pressure fluid over the 
upper surface of a multiple segment flap. 
Still another object of this invention is to provide a 
technique for increasing the lift-to-drag ratio of an aero- 
dynamic body for economical cruising flight and en- 
hancing landing and takeoff characteristics. 
Yet another object of the instant invention is to pre- 
vent airflow turbulence because of a large break in the 
wing upper surface and relative vibration between the 
multiple flap segments utilized for reducing that break. 
Yet another object of this invention is to provide 
boundary layer control wherein the airfoil drag can be 
reduced by more than thqpower drag required to oper- 
ate the blower and a blowinkQp induces large lift gains. 
Generally, the foregoing and other objects are ac- 
complished by pivotally mounted upper and lower flap 
5 segments on the trailing edge portion of the airfoil. The 
two flap segments have mutually abutting surfaces that 
slide on one another and are maintained in contact by 
a spring or track and connector arrangement. The ad- 
jacent upper portions of the airfoil and flap are curved 
10 to provide a small slot therebetween. A nozzle is posi- 
tioned in the slot between the leading portion of the up- 
per flap segment and the wing and is connected to a high 
pressure chamber by means of a conduit, all of which are 
located within the airfoil section. The chamber is con- 
15 nected to a source of high-pressure fluid with controls 
therebetween to govern the amount of fluid entering 
the chamber. Flap position is controlled by a linkage 
mechanism driven by a conventional power supply op- 
erated from within the aircraft. The nozzle slot location 
20 and the deflection of the upper flap segment permit full 
utilization of the high-pressure fluid in obtaining the 
boundary layer control that provides the desired high 
lift characteristics. 
A more complete appreciation of the invention and 
25 many of the attendant advantages thereof will be readily 
apparent as the same becomes better understood by ref- 
erences to the following detailed description when con- 
sidered in connection with the accompanying drawings 
whexin : 
FIG. 1 is a diagrammatic cross section of an airfoil 
embodying the instant invention with parts omitted for 
clarity; 
FIG. 2 is a diagrammatic cross section of an airfoil 
with parts omitted for clarity and showing the flap ar- 
FIG. 3 is a diagrammatic plan view of a segment of 
FIG. 4 is a diagrammatic cross section of an airfoil 
4o with parts omitted for clarity and showing an alternative 
FIG. 5 is a diagrammatic plan view of the embodiment 
Referring now to the drawing wherein like reference 
45 numerals designate identical or corresponding parts 
throughout the several views and more particularly to 
FIG. 1 wherein an airfoil section generally designated 
by numeral 10, is shown as having centerline 12 corre- 
sponding to the centerline of the flow stream around the 
5o airfoil section. The airfoil section has leading edge 14 
and a relatively deep chord. Dimension a repzesents 
the length of the chord with dimension b the distance 
from leading edge 14 to the leading edge of the flap. 
Dimension c designates the distance from leading edge 
55 14 to the after section of airfoil 10 adjacent the nozzle 
slot 50. Tests have shown that efficient operation of the 
invention results if dimension 6 is equal to 0.654 of a 
and dimension c is equal to 0.65 of a. 
Airfoil 10 is shown as having flap 20 adjacent the trail- 
Flap 20 has upper flap segment 22 pivoted 
adjacent the upper edge surface of airfoil 10 on axis 24 
and lower flap segment 26 pivoted at 28 to the lower por- 
tion of airfoil 10. Upper surface 30 of flap segment 22 
conforms to the upper surface of the airfoil and termi- 
65 nates in a curved leading portion 40 that extends to lower 
surface 32. Flap segment 26 has lower surface 34 sub- 
stantially forming an extension of the lower surface of 
airfoil section 10 and terminating at the trailing edge of 
flap 20. Surface portion 38 connects with upper surface 
70 36 of flap segment 26 and forms an extension of upper 
surface 30 of flap segment 22 when flap 28 is in an un- 
deflected position. As shown in FIG. 1, lower surface 32 
30 
35 rangement in a deflected position; 
the construction of FIG. 2; 
drive mechanism; and 
of the instant invention as shown in FIG. 4. 
6o ing edge. 
3 
of upper flap segment 22 substantially conforms for a 
portion thereof to upper surface 36 of lower flap 26. 
Nozzle dot 50 forms the trailing edge of an elongated 
conduit 52 which connects to  tubular chamber 54. The 
latter forming a container and equalizing area for the 
high-pi-essure fluid flowing into chamber 54 via a conduit 
from high-pressure fluid source 58: such for example as 
the compressor of a propulsion unit. Control mechanism 
or valve 56 is positioned between high-pressure fluid 
source 58 and chamber 54 to govern the amount of fluid 
released into the chamber, Chamber 54, nozzle 50 and 
conduit 92 extend substantially the span of flap 20. 
FIGS. 2 and 3 show airfoil section PO with flap 20 in 
a deflected position caused by a linkage mechanism. The 
linkage mechanism shown in FIGS. 2 and 3 has link 76 
pivoted to upper flap segment 22 about pivot axis 78 and 
to piston rod 80 at pivot pin 82. Piston rod 80 operates 
in conjunction with a conventional double-acting cy3inder 
84 pressurized by a hydraulic fluid flowing through con- 
duit 88 from control source 86. 
In order to provide for coordination of movement and 
prevent relative vibration between the flap segments, up- 
per flap segment 22 is provided with stud 70 with secured 
foot 72 in spaced relation thereto. Lower flap segment 
26 is provided with a track which mates with foot 72. 
Although, as best seen in FIG. 3, foot 72 and track 54 
are shown as having a dovetail cross section, it is readily 
apparent that other conventional sliding connections could 
be utilized. For example, track 74 could be of T-shape 
and countersunk within upper surface 36 of lower flap 
segment 26 with foot 72 being of flanged U-shape. 
The operation of the linkage shown in FIGS. 2 and 3 
causes deflection of upper flap segment 22 by forcing the 
hydraulic fluid under pressure through conduit 88 into 
cylinder 84 where it forces piston rod 80 rearwardly and 
causes link 76 to rotate counterclockwise; thus maintain- 
ing upper flap segment 22 in the normal cruising position 
as shown in FIG. 1. In order to cause flap 20 to deflect, 
pressure is relieved on one side of double-acting cylinder 
84 which draws piston rod 80 forward and rotates link 76 
clockwise. The coordination of movement of lower flap 
segment 26 is accomplished by foot 26 sliding in track 74. 
Another embodiment of a mechanism for operation of 
the two-segment flap of the instant invention is shown in 
FIGS. 4 and 5, wherein links 96 and 98 are respectively 
pivoted at one end at 100 and 102 to upper flap segment 
22 and lower flap segment 26. The other ends of the pair 
of links 96 and 98 are pivoted respectively at 106 and 
108 to the ends of bar extension 104 which is connected 
to drive shaft 110. A conventional activator or power 
source 112 is utilized for providing torque to shaft 110. 
The mechanism of FIGS. 4 and 5 operates by a signal 
sent to activator 112 (FIG. 5) which rotates drive shaft 
110 that in turn rotates bar extension 104. Links 96 and 
98 reciprocate to cause movement of upper flap segment 
22 and lower flap segment 26. Obviously, activator 112 
must be capable of rotation either in a clockwise or 
counterclockwise direction. As shown in FIG. 4, clock- 
wise rotation of shaft 110 causes a similar clockwise 
movement of bar extension 104 to  thereby push link 96 
toward the trailing edge of airfoil section 10 and pulls 
link 98 forward to effect deflection of both flap segments 
22 and 26. Thus, it is seen that a counterclockwise rota- 
tion causes flap 20 and its individual flap segments 22 and 
26 to be deflected into the high-lift landing and takeoff 
position while a clockwise rotation raises flap 20 to a 
cruising position. The exact location of links 96 and 98 
and their corresponding pivots 100 and 102 would neces- 
sarily depend upon the size of flap 20 and its component 
segments 22 and 26. 
In order to prevent relative vibration between the flap 
segments, spring 90 is mounted at 92 to upper flap seg- 
ment 22 and 94 to lower flap segment 26. Obviously, 
many modificatiohs for activation of the mechanisms as 
well as to prevent vibration between upper flap segment 
4 
22 and lower flap segment 26 may be utilized. For e%am 
ple, it may be desirable, in order to insure positive action 
of segments 22 and 26 as shown in FIGS. 4 and 5, to uti- 
lize the track and runner arrangement shown in FIGS. 
Thus it is seen that the multiple segment fiap of the 
instant invention with pivotal axes located whereby curved 
portion 40 of upper flap segment 22 maintains a substm- 
tially narrow and uniform break in the upper surface of 
10 airfoil 10 to avoid any turbulence of airflow or drag 
created by the previously known wide breaks. In conse- 
quence of the small break, the blowing air or high-pres- 
sure fluid released through nozzle 50 is able to provide the 
utmost efficiency in operation of the system for boundary 
15 layer control when flap 20 is in a retracted position result- 
ing in a higher lift-to-drag ratio for cruising. Full uti- 
lization of boundary layer control, regardless of the posi- 
tion of flap 20, has the attendant advantage of providing 
high lift characteristics for the airfoil during takeoff and 
6 2 and 3. 
20 landing. 
Obviously, many modifications and variations of the 
subject invention are possible in the light Of the above 
teachings. 
It is, therefore, to be understood that within the sCO@ 
25 of the appended claims, the invention may be practiced 
What is claimed as new and desired to be secured by 
1. In a boundary layer control system for an aircraft 
30 having wings with relatively large chords, the combination 
comprising: flap means exdending substantidly the length 
of the wing and having complementary upper and Iowei" 
flap segments; said flap segments pivoted to said wing adjaa 
cent the upper and lower surfaces respeatively at k e d  
35 points thereof; linkage means pivotally intetconnected td 
said flap segments and actuator means; eompressm means: 
for a supply of high-pressure fluid; dozzle mearis betweed 
the upper surface of said wing and said upper flap segment: 
and conduit means extending between said compressdt 
40 means and said nozzle means whereby high-pressure fluid 
from the compressor is exhausted over the upper flap seg- 
ment to effectively control the boundary layer along the 
upper surface of the wing and thereby impart high-lift 
characteristics to the wing regardless of the orientation 
of the aircraft. 
2. The boundary layer control system of claim 1 where- 
in the complementary flap segments have autually abut- 
ting after portions; and slidable connecting means fof 
preventing separation of said mutually abutting porfions, 
3. The boundary layer control system of claim 2 where- 
" in said linkage means comprises a bar pivotally connected 
at one end to said upper flap segment and at the other end 
to said actuator means. 
4. The boundary layer control system of claim 2 where- 
in the linkage means comprises a pair of links pivotallqt '' attached at one end to said upper and lower flap segments 
and at the other end to a bar extension secured to a driver 
shaft; and drive means for supplying power to said drive 
shaft. 
5. The boundary layer control system of claim 2 where- '' in the connecting means include a track on said lower flap 
segment and a mating projection on said upper flap seg- 
ment whereby said flap segments slidably engage one 
another. 
6. The boundary layer control system of claim 2 where- 
7. The boundary layer control system of claim 2 where- 
in said linkage means comprises a bar pivotally connected 
at one end to said upper flap segment and at  the other 
end to said actuators means; and said connecting means 
include a track on said lower flap segment and a mating 
projection on said upper flap segment whereby said flap 
segments slidably engage one another. 
8.  "he boundary layer control system of claim 2 where. 
76 in the linkage means comurises a nair af links tivotallv 
otherwise than as specifically described and shown. 
Letters Patent of the United States is: 
45 
65 in said connecting means comprise a spring. 
b 3,321,157 
attached at one end to said er and lower flap segments 
and at the other end to a bar extension secured to a drive 
shaft connected to drive means for supplying power there- 
to; and said connecting means comprise a spring. Re. 24,917 12/1960 Attinello. 
UNITED STATES PATENTS 
1,848,809 3/1932 Upson. ' 2,137,882 11/1938 Blaylock et al. 
2,406,919 9/1946 Stalker. 
2,928,627 3/1960 Johnson. 
References Cited by the Examher 
UNITED STATES PATENTS 
2,142,123 1/1939 Fahrney -__----- ----- 2 4 4 4 2  2,940,690 ,6/1960 Wood. 
2,279,615 4/1942 Bugatti _ _ _ _ _ _ _ _ _ _ _ _ _ _  244-42 2,978,207 411961 Davidson. 
3,188,021 6/1965 YOUllg __--_-___----- 2 4 U 2  MILTON B U C n E R ,  Primary Examiner. 
3,127,129 3/1964 Petrie _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  244-42 lo 
FOREIGN PATENTS B. BELKIN, Assistant Examiner. 
1,287,819 2/1962 France. 


Double hinged flap Patent

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