A means for attenuating the vortex created at aircraft wingtips which consists of a retractable planar surface transverse to the airstream and attached downstream of the wingtip which creates a positive pressure gradient just downstream from the wing is presented. The positive pressure forces a break up of the rotational air flow of the vortex

Patterson, J. C., Jr.

English

NASA Technical Reports Server

United States Patent [191 
Patterson, Jr. 
[ 1 11 3,984,070 
[451 Oct. 5, 1976 
WINGTIP VORTEX DISSIPATOR FOR 
AIRCRAFT 
Inventor: James C. Patterson, Jr., Yorktown, 
Va. 
Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Filed: May 28, 1974 
Appl. No.: 413,913 
U.S. CI. ................................. 244/130; 244/1 13 
Int. CL2 .......................................... B64D 47/00 
Field of Search ................ 244/130, 40 R, 40 A, 
244/4l, 42 DC, 110 D, 113, 1 TD 
References Cited 
UNITED STATES PATENTS 
2,612,332 9/1952 Drozinski ......................... 244/1 I3 
2,678,785 5/1954 Graham ............................ 244/1 13 
3,596,854 8/1971 Haney .............................. 244/40 A 
3,881,669 5/1975 Lessen ........................... 244/130 X 
FOREIGN PATENTS OR APPLICATIONS 
1,564,026 4/1969 France .............................. 244/40 R 
1,209,801 3/1960 France ................................ 244/130 
Primary Examiner-Trygve M. Blix 
Assistant Examiner-Barry L. Kelmachter 
Attorney, Agent, or Firm-Howard J. Osborn; John R. 
Manning 
t571 ABSTRACT 
A means for attenuating the vortex created at aircraft 
wingtips which consists of a retractable planar surface 
transverse to the airstream anld attached downstream 
of the wingtip which creates a positive pressure gradi- 
ent just downstream from the wing. The positive pres- 
sure forces a break up of the rotational air flow of the 
vortex. 
2,075,8 17 411937 Loerke ................................ 244/130 
2,421,870 6/1947 Dornier et al. ..................... 244/1 13 12 Claims, 4 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19770003059 2020-03-20T06:38:28+00:00Z
U.S. Patent oct. 5 ,  1976 Sheet 1 of 2 3,984,070 
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FIG. 1 
41 
FIG. 2 
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U.S. Patent oct. 5,1976 Sheet 2 of 2 3,984,070 
FIG. 4 
3,984,070 
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lem is the greatest hindrance to air traffic, such as near 
airports. Such a compromise requires a device which 
can be retracted and deployed at will and it is for that 
function that the rigid spline configuration is preferred. ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 5 The spline drogue device is a multiple spline device 
ployee of the US. Government and may be manufac- which is essentially several plates extending windmill 
tured and used by or for the Government for govern- fashion from a central core. The plates, however, differ 
mental purposes without payment of any royalties from a windmill in that they ,are rigidly held exactly 
thereon or therefor. transverse to the airstream in order to maximize the 
l o  airstream disturbance. Theoretically the drogue device 
can be a complete circular surface similar to a drogue BACKGROUND OF THE INVENTION 
This invention relates generally to aircraft aerodY- chute, but for purposes of construction and retractabil- 
namics and specifically to a method and apparatus for ity the spline structure is used. Moreover, the effect on 
attenuating the airstream Vortex generated at the wing- the vortex is essentially the same as a complete circular 
tips of aircraft. I 5  surface. The effectiveness of this device is a function of 
The lift-induced wingtip vortex associated with large its area and the location of this area relative to the 
Jet aircraft has become a major problem to the air vortex. The spline configuration was chosen to distrib- 
traffic controller as well as an unseen hazard to smaller ute the required minimum area for effective vortex 
aircraft. The problem arises from the fact that the vor- dissipation the largest expanse. This minimum 
long persistence and that it intensifies as the weight of configuration diameter of 60 percent of the mean gee- 
the aircraft increases. The rotational airflow or vortex metric chord of the aircraft wing and an individual 
developed at or near the wingtip of an aircraft remains spline width of 15% of the configuration diameter. 
essentially stationary in space and induces a rolling Since the formation of a vortex is associated with the 
moment on smaller following aircraft if encountered. 25 lift change at the wingtip, the drogue device should be 
the limits of control of the smaller aircraft and such loss wing, the vortex forms at to percent of 
the semispan location and the drogue device should be of control has been proven to occur as far as 4 miles 
behind a large aircraft. The vortex problem is particu- 3o located accordingly. In a particular aircraft, structural 
larly severe in flight paths around major airports where considerations such as wing flap configuration may 
smaller aircraft are most likely to follow large aircraft force some compromise with the ideal location. and where the small aircraft has little altitude in which The drogue device is mounted downstream of the to regain control. 
Previous attempts to limit the vortex effect have trailing edge of the wingtip by use of a probe configura- 
tion. The probe is used to house the retracting mecha- generally been unsuccessful either because, as with 35 
wing end plates or wingtip extensions, the devices did nism so that when not in use, each blade of the drogue 
suficiently modify the far downstream effects of device collapses to form a streamlined configuration in 
the vortex or, as with landing flap variations and wing conjunction with the probe. The position of the drogue 
spoilers, the vortex attenuation caused too great a lift device downstream of the wing trailing edge is deter- 
loss for the aircraft. 40 mined by minimizing the detrimental effect on aircraft lift. A typical spacing between the wing trailing edge 
SUMMARY OF THE INVENTION and the drogue device which accomplishes this is ap- 
The present invention breaks up the rotational flow proximately the diameter of the drogue device. 
of &e vortex and thus largely eliminates the danger of An alternate device for mass injection into the vortex 
the otherwise stationary vortex remaining to disturb the 45 creating the associated positive pressure gradient 
flight of following aircraft. This is accomplished by downstream from the wingtip which differs from the 
changing the airflow pattern in the region of the air- drogue device is the wing-tip mounted jet engine. This 
crak wingtip in such a manner that the rotation airflow engine creates a similar airstream disturbance which 
of the vortex is destroyed by linear airflow around it attenuates the vortex. Since the tip mounted engine 
and through the vortex core. The most basic device to 50 requires a high trust, it is more aDPrOPriate for use on 
accomplish such a disturbance to the vortex is the use new aircraft designs than for a retrofit application as is 
of a decelerating chute at each wingtip of the aircraft. the drogue device. 
Such chutes cause a positive pressure gradient just It should be noted, however, that the drogue device, 
downstream of the aircraft wingtip, in effect pushing a when properly designed, and particularly in a new air- 
mass of air ahead of each chute and therefore disturb- 5 5  craft design, could serve both as vortex attenuation and 
ing the vortex airflow just ahead of the chute and just as a decelerating device to achieve more rapid descent 
behind the wingtip. The shearing stresses set up be- during landing approaches. Moreover, a combination 
tween the mass of air forced forward by the chute and of drogue deployment and engine thrust variation can 
the rotational flow of the vortex itself plus the interrup- be programed on the landing approach to optimize 
tion ofthe axial flow in the vortex core cause the vortex 60 both functions. 
TEX DHSSIPATBW FOR AIRCRAFT 
tex created by large aircraft is very strong and Of such 2o area is approximately that which results from a drogue 
This moment can be so strong that it surpasses located at or near the wingtip. Hjor a tapered and swept 
. 
BRIEF DESCRIPTION OF THE DRAWINGS to dissipate. The decelerating chute is, by its nature, a device which is difficult to use and then retract. While 
the drogue device as deployed in the invention does not 
affect aircraft lift any such device which disturbs the 
airstream suficiently to dissipate the vortex also causes 65 
a drag which lowers the aircraft efficiency. It is there- 
fore desirable to strike a compromise and to use the 
vortex attenuation only where the severity of the prob- 
FIG. 1 is a perspective view of the drogue chute 
FIG. 2 is a perspective view of the preferred embodi- 
FIG. 3 is a perspective view of the preferred embodi- 
embodiment of the invention; 
ment of the invention; 
ment fully retracted; 
3,984,070 
3 4 
FIG. 4 is a perspective view of the jet-engine embodi- Operation of the preferred embodiment has been 
experimentally flight tested with excellent results. A ment of the invention. 
Douglas C-54 aircraft with a spline structure on each 
wingtip has been flown in such experiments trailed by a 
A basic understanding of the invention can best be 5 Piuer Cherokee chase aircraft to note the effects of the 
DESCRIPT1oN OF THE lNVENTloN 
accomplished by reference to FIG. 1 which depicts the 
drogue chute embodiment of the invention. FIG. 1 
shows a simplified wing structure 12 attached to air- 
craft fuselage 14. The wingtip vortex is generated ap- 
proximately in area 16 due to the aerodynamic effects 
of the discontinuity of lift caused by the termination of 
wing 12 at wingtip 18. Drogue chute 20 attached to 
wingtip 18 by lines 22 cause a positive pressure gradi- 
ent in area 16 while the aircraft is in flight essentially 
because of the drag effects of any nonaerodynamic 
shaped body. This positive pressure gradient in area 16 
dissipates the rotational vortex airflow caused by the 
lift discontinuity by forcing linear airflow through and 
around the vortex core. 
vortex on the control characteristic of a following air- 
craft. Without the invention the chase aircraft was 
rolled 180", despite attempts to control it, when ap- 
proximately four nautical miles behind the test aircraft. 
With the spline structure installed, the case aircraft was 
able to maintain control as close as one-half nautical 
mile. Visual tests of the vortex of the C-54 aircraft 
made by the use of air-dispersed powder indicate the 
typical vortex has a diameter of two to three-feet, but 
that the vortex on aircraft with spline structures in- 
stalled is dissipated to a diameter of 60 to 80 feet. 
Rolling moment coefficient measurements on the chase 
aircraft indicate reductions of approximately 5.5% for 
the spline configuration. All the tests indicate that the 
STRUCTURE OF THE PREFERRED spline configuration reduces the effects of the vortex to 
EMBODIMENT a point where it can be considered nonhazardous to 
smaller following aircraft. 
The preferred embodiment functions to dissipate the An alternate embodiment of the invention is shown 
vortex in the same manner as the drogue chute. How- in FIG. 4. In such an embodiment jet engine 60 is 
ever, the structure differs in that the preferred embodi- 25 mounted on wing 62 in a similar manner as the pre- 
ment is a structural configuration, as shown in FIG. 2, ferred embodiment in the vicinity of wing tip 68. Since 
gradient at its exit 64 which is adjacent to the vortex quires. To the simplified wing structure 32, attached to air- origin area 66, this positive pressure dissipates the vor- 
craft fuselage 34, is added aerodynamic probe 36. At 30 tex in the Same manner as a drogue device. This em- 
configuration 38 composed of individiual plates 40,41, propriate for original aircraft designs than for retrofit 
35 tional trust for flight as opposed to causing airstream 
designed to be Or retracted as the flight re- the jet engine exhaust produces a positive pressure 
the downstream end 37 Of probe 36 's 'PIine bodiment, being a comp]ex system, is ap- 
42, 43, 44, 45, 46 and 47* Each plate has a application, but it has the advantage of yeilding addi- configuration so that it may be folded at hinge 50 which 
is mounted upon core 48 when moved by actuator 52. 
The actuators may be of the fluid energized type with drag' 
ture being of conventional design. The configuration of herein shown are merely preferred embodiments. Vari- 
plates closes up flower petal-like toward the rear of the OUs changes may be made in shape* size and the ar- 
namic shape 53 with probe 36 as shown in FIG. 3. tuted for those illustrated and described; and certain 
Cover 54 moved by cover actuator 55, which may be a features may be used independently from other fea- 
prime with appropriate linkage shown schemati- tures without departing from the spirit and scope of the 
tally, slides Over the array of actuators to maintain the invention as defined in the 
For example, the spline configuration shown may be aerodynamic surface. 
The location of spline structure 38 is determined by constructed Of mOre Or fewer plates Of different shapes, 
the actual point of final roll-up of the vortex and the or the location of the invention on the aircraft wing 
structure of aircraft wing 32. Ideally, spline structure may be varied as the aircraft structure requires. 
38 should be mounted exactly at the center of the vor- What is claimed as new and desired to be Secured by 
tex roll-up as determined by model aircraft experimen- 50 Letters Patent of the United States is: 
tation, which on a typical tapered wing would be at 80 1. An apparatus for dissipating a lift-induced vortex 
to 90% of the semispan. However, structural consider- generator by an airstream flowing Past an aircraft wing 
ations such as the location of aileron 56 in FIG. 2 may having a leading edge and a trailing edge comprising: a 
force a less than ideal location on an existing aircraft to positive pressure gradient producing means; said gradi- 
which the invention is to be retrofitted. 55 ent producing means being a drogue structure having a 
Spline structure 38 should be mounted downstream surface transverse to the airstream, and an attachment 
of trailing edge 58 a distance sufficient to prevent any means of aerodynamic design which attaches said 
detrimental effect upon the aircraft lift. Typically this drogue structure downstream of the origin of the vor- 
distance is approximately equal to the diameter of the tex. 
spline configuration. 60 2. An apparatus for dissipating an aircraft lift- 
The effectiveness of the invention in dissipation of induced vortex as in claim 1 wherein the attachment 
the vortex is directly affected by the area of the flat means includes deployment means for selectively de- 
plate surface of the structure. The minimum area for ploying and retracting the drogue structure. 
effective dissipation of the typical vortex has been ex- 3. An apparatus for dissipating an aircraft lift induced 
perimentally determined to be the area of a spline con- 65 vortex as in claim 1 wherein the drogue structure is a 
figuration of eight plates whose widths are 15% of the drogue chute. 
configuration diameter and whose configuration diam- 4. An apparatus for dissipating an aircraft lift- 
cter is 60% of the mean geometric chord of the aircraft. induced vortex as in claim 1 wherein the drogue struc- 
appropriate linkage connected to the plates, this strut- It is to be understood that the forms Of the invention 
probe 36 when actuated to form an integral aerody- 40 rangement Of parts; means may be substi- 
45 
3,984,070 
5 6 
ture is a spline configuration of plates which simulate a 9. An apparatus for dissipating an aircraft lift- 
planar surface. induced vortex as in claim 8 wherein the configuration 
5. An apparatus for dissipating an aircraft lift- of plates is shaped to form a unitary aerodynamic sur- 
induced vortex as in claim 1 wherein the drogue struc- face with the attachment means when the configuration 
ture has a diameter at least 60% of the mean distance of plates is retracted. 
between the leading edge and the trailing edge of the 10. An apparatus for dissipating an aircraft lift- 
aircraft wing. induced vortex as in claim 2 wherein the drogue struc- 
6. An apparatus for dissipating an aircraft lift- ture is a spline configuration of plates which simulate a 
induced vortex as in claim 1 wherein the drogue struc- planar surface, and wherein each plate is hinged; and 
ture is mounted downstream of the wing trailing edge a l o  wherein the deployment means is an array of actuator 
distance approximating the diameter of the drogue means. 
structure. 11. An apparatus for dissipating an aircraft lift- 
7. An apparatus for dissipating an aircraft lift- induced vortex as in claim 10 wherein the configura- 
induced vortex as in claim 5 wherein the drogue struc- tion of plates is shaped to form a unitary aerodynamic 
ture is mounted downstream of the wing trailing edge a l 5  surface with the attachment means when the configura- 
distance approximating the diameter of the drogue tion of plates are folded down. 
structure. 12. An apparatus for dissipating an aircraft lift- 
8. An apparatus for dissipating an aircraft lift- induced vortex as in claim 2 including means for cover- 
induced vortex as in claim 2 wherein the drogue struc- 2o ing said deployment means to provide an aerodynami- 
ture is a spline configuration of plates which simulate a cally clean surface when not deployed. 
planar surface and wherein each plate is retractable. * * * * *  
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65 . 


Wingtip vortex dissipator for aircraft

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