Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to vertical and/or short takeoff and land-
ing ~/STOL1 airplanes and ;n particular to improved method, system9 and
apparatus for vector;ng the aircraft engine exhaust flow with a system of
trail;ng edge flaps to achieve vertical and/or short takeoffs and landings.
Several types of so called V/STOL aircraft have been proposed.
One type, exemplified in United States Patent 3J096a95~, Bauger et al, uses
an articulated cylindrical duc~ through which a turbofan exhaust is discharged.
Thi.s type of system has relatively low efficiency due to large losses in turn-
ing the exhaust. One loss occurs in the fan exhaust duct on the outsi.de of
the turn, where the turning of the exhaust b~ the nozzle duct wall tends to
generate contrarotating vortices. These vortices ~orm a blockage in the duct,
causing a thrust loss. Also mixing o~ the fan exhaust with the hot core or
turbine exhaust limits the augmentation ratio available because of a require-
ment to match the pressures of the two streams.
Another proposal is shown in United States Patent 39330,500 ~.o
Winborn. In this propulsive wing type, the fan discharge is vectored through
lower surface flaps at approximately the mid cord of the propulsive wing,
while the hot turbine exhaust is discharged at the upper trailing edge of
the propulsive wing. The discharge of a high energy jet at mid chord on the
].ower surface of the wing will cause high suckdown forces on the wing and
may even be large enough to prevent lit-of~.
Another disadvantage of designs such as the Winborn patent re~er-
red to above is in the arrangement of the deflecting flaps for the ~an ex
haust. Several flaps are spaced across the fan nozzle, forming a cascade
and vertically dividing the exhaust stream into several layers. The flaps
all pivot downwardly, turning the individual layers o:~ air. The several
flaps in the mainstream create drag, causing a loss in thrus~ efficiency.
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Another disadvantage is that due to their positioning, the total noz7~1e area
varies as the flaps move from the horizontal to downward poslt:ions. The
variance can detrimentally affect the thrust during transition positions.
Another example of this cascade flap arrangement is shown in United States
Patent ~,000~868, Gregor.
One manner in which certain types of airplanes have -improved the
lift at low speeds is by bleeding a portion of the jet engine exhaus-t air
or fan air over the upper surface of a wing trailing edge flap. An example
of this system is shown in United States Patent ~,920,203 ~o Moorehead. The
high energy sheet of air being discharged delays or prevents boundary layer
air flow separation. Boundary layer separation as used in this context refers
to the separation of an airstream flowing over an airfoil from the airfoil
surEace. At and after the point of separation, a higher static pressure tur-
bulent area exists between the airstream and airfoil, causing drag and re-
ducing the lifting potentlal. The high energy sheet of air being ejected
over the flap retards or prevents this separation. Also, the jet sheet can
induce, by jet pumping action, additional flow over a wing to increase its
circulation or li~t, this increased circulation being kno~l as super circula-
tion.
Bleeding a portion of the exhaust over a trailing edge flap has
been used, wit'n the energy level of the jet sheet at moderate levels, to
successfully improve the low speed characteristics of conventional take-oEf
and landing airplanes, as shown in the Moorehead patent.
One proposal, shown in United States Patent 2,879,957, Lippisch,
proposes to utilize the propulsion system to create super circulation in a
V/STOL airplane. One deficiency in the desig~ disclosed therein is that it
îs unlikely tha-t the sheet of air could exit through the upper slot since
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higher pressure air exis-ts on the upper surface of the nacelle.
Means would have to be provided -to scoop the airflow ou-t. The
Lippisch design also utilizes the high drag cascade system of
flaps, and has other disadvantages as well.
It is accordingly a general objec-t of this inven-tion to
provide an improved propulsion system for a V/STOL airplane.
The invention provides the method of improving airp]ane
fligh-t charac-teristics in a V/S~`OL airplane in which a higher than
ambient static pressure flow of exhaust gas from a power means is
turned to effec-t the change between flight modes respectively
having greater horizontal and grea-ter ver-tical thrust vectors,
wherein at least a major portion of said exhaust gas flow is
directed through a closed conduit means to exi-t through a thrust
producing main nozzle downstream of the power means for powering
the airplane in all flight modes varying from horizontal to at
least partly vertical; and wherein the exhaust gas flow is turned
through an angle from a condition in which the exhaust gas flow is
directed predominantly horizontally Eor horizontal thrus-t, -to a
condition in which -the exhaust gas flow is direc-ted predominately
downwardly -thereby forming a bend when at least partly vertical
thrust is desired; said method comprising: bleeding-off -through
a second nozzle a second portion of the exhaust gas flow from an
outer portion of the bend in said closed conduit means upstrearn of
the thrust producing main nozzle exit and downs-tream of the bend
leading edge to reduce vortex formation in said conduit means dur-
ing at least partly vertical thrust; and direc-ting a bled-off por-
tion and said major portion of the exhaust gas flow adjacent each
other and oriented towards the same general direction in all fligh-t
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modes; whereby increased thrust is avai]able in all flight modes
by recovering thrust potential of the bled-off por-tion and
achieving high efficiency by eliminating contro-rotating vor-tices
when said flow o:E exhaus-t gas is -turned to form a bend.
From another aspect/ the invention provides in a vertical
and/or short takeoff and landing (V/STOL) airplane, a propulsion
system providing enhanced thrust and airplane handling qualities
through more efficient turning of its exhaust be-tween horizon-tal
and upward directed flight modes which comprises: propulsion means
for generating a higher than ambient static pressure flow of thrust
producing exhaust gas; exhaust nozzle means forming a condui-t Eor
containing and directin~ at least a portion of said exhaust gas
flow from the propulsion means to the airplane exterior, and to
turn the flow between substantially horizontal and downwardly direc-
ted flow positions; said exhaus-t nozzle means comprising. primary
thrust nozzle means for the exit of a major portion of said
exhaust gas flow, and secondary thrust nozzle means for bleeding-
off a minor portion of the exhaust gas flow; said secondary thrus-t
nozzle means positioned in said primary -th.rllst nozzle means -to
effect said bleed-off of exhaust gas flow downstream of the
commencement of the -turn therein so as substantially to prevent
formation of dynamic pressure-induced contra-ro-tating vor-tices in
the outside of the turn; and said secondary -thrust nozzle means
being directionally movable so as to direct -the bleed-off to flow
closely parallel to the major portion of the exhaus-t flow a-t all
positions thereof whereby the bleed-off is -turned -together wi-th the
major portion of the exhaust flow, -to provide a subs-tantially
coherent uni-tary-li.ke exhaust stream passing from said airplane at
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all angles of flow from horizontal to downward flow; -thereby
maximizing both the -thrus-t from said major por-tion of the flow and
the recovery of thrust from said bleed-off flow and improving the
handling qualities of the airplane at all positions of turning of
-the exhaust gas flow.
The invention further provides a propulsion system for
vertical and short take-off and landing airplanes, cornprising: a
nacelle comprising a conduit, said nacelle having an upper surface
and a lower surface forming an upper surface and a lower surface
L0 of an airfoi1, respectively; a fan mounted in said nacelle for pro-
viding a flow of propulsive fan exhaus-t; a turbine engine mounted
in the nacelle behind the fan and connected to the fan for driving
the fan; a fan nozzle and exhaust air turning means located in
said nacelle downstream of the fan for discharging fan exhaus-t air
at controllable angles between a generally horizontal direc-tion for
forward thrust and generally downward direc-tions for vertical
thrust, said turning means forming one or more bends; fan exhaus-t
air bleed-off means positioned in said conduit for bleeding-off
through a nozzle a por-tion of the fan exhaust air stream from an
outer portion of the turning means downstream of the leading edge
thereof to reduce vortex formation in -the -turned exhaust stream;
an engine nozzle and exhaust turning means located in said nacelle
downstream of the engine for discharging engine exhaust downs-tream
of a shroud means at a predetermi.ned desired angle between horizon-
tal for forward thrus-t and generally downwards for vertical thrust,
and forming one or more bends, said shroud means ex-tending from
the rear of the engine to the engine nozz]e for separating the
engine exhaust from the fan exhaust air un-til the engine exhaust
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passes through the engine nozzle and exhaus-t turning means and the
fan exhaust passes -through the fan nozzle and exhaust air tuxning
means; the fan nozzle and exhaust air turning means, the fan
exhaus-t air bleed-off means, and the engine nozzle being positioned
in close adjacency and oriented to direct all thrus-t in the same
general directions in all flight modes to form the exhaus-t streams
in a substantially unitary flow immediately downstrearn of -the fan
nozzle so as to recover thrust poten-tial from both fan air and
engine exhaust in all flight modes.
A propulsion system for a propulsion induced lif-t V/STOL
airplane is disclosed that has wing/nacelle units secured to each
side of the fuselage. Each wing/nacelle unit con-tains a turbofan
engine posi-tioned ahead of a system of three flaps. An upper flap
is positioned at the -trailing edge of the wing/nacelle upper sur-
face. Two slots are provided at -the leading edge of this flap.
The engine turbine discharge has a shroud leading to the most for-
ward slot for separating its hot turbine exhaust from the fan
exhaust and discharging it over the flap. The most rearward slot
discharges high energy air from the fan exhaust duct
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over the flap.
A lower .~lap is mounted to the trailing edge of the wing/nacelle
lo~er surface. An intermediate flap is located behind and in alignmen~ with
the lower flap as part of the airfoil lower surface during horizontal fligh~.
All three flaps pivot downwardly to vector the exhaust downward for vertical
flight.
The n~ain fan discharge during horizontal flight is through the
space between the intermedia~e flap and ~he upper flap, this space being free
of additional flaps. For vertical flight, the intermediate flap pivots over
to a position below the upper flap9 orming the trailing edge of the airfoil
upper surface. A slot between the upper and intermediate flaps during -the
vertical flight position bleeds off an additional amount of fan exhaust to
improve turning efficiency and to provide additional external boundary layer
control.
Accordingly it has been found that more efficient V/STOL aircraft
fligh* can be achieved by providing a nacel~ forming an airfoil, wi~h an
engine exhaust nozzle formed by a system of trailing edge flaps providing
both main o~ primary and auxiliary or secondary exhaust nozzles in which one
of the flaps is at the trailing edge of one of the airfoil surfaces ~e.g.,
lower) in one principal flight position ~e.g., horizontal) and is reposition-
able to form the trailing edge of the other (e.g., upper) airfoil surface in
the other principal flight position ~e.g., vertical) as the exhaust nozzles
are directed between horizontal and vertical flight positions. Such flap can
thus be shifted between positions in which it may optionally be a part of
either the "upper" or "lower" surfaces of ~he airfoil depending on ~he
direction of nozzle thrust with total nozzle area remaining substantial]y
con~tant ~or all nozzle directions,or total nozzle area may be made variable
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according to predetermined aircraft operating requirements. In horizontal
and vertical ~light conditions the nozzles can be fully open and unobstructed.
The inventlon will urther be described, by way o-E example
only with reerence to the preferred embodiment illustrated in the accompanying
drawings, wherein:
Figure 1 is a perspective view of an airplane constructed in
accordance with this invention.
Figure 2 is a side elevational view of the airplane of Figure 1.
Figure 3 is a schematic cross-sectional view of the airplane of
Figure 1, taken along the line III--III of Figure 6, with the propulsion
system shown in the horizontal flight mode.
Figure ~ is a schematic view of the propulsion system, similar
to Figu~e 3 but showing the propulsion system in a transistional flight mode.
Figure 5 is a schematic view of the propulsion system, also
similar ~o Figure 3 to show the propulsion system in the ~ertical flight mode.
Figure 6 is a top view of the airplane of Figure 1.
Figure 7 is a fragmentary and schematic cross-sectional view o:E
the propulsion system of Figure 3, taken along the line VII-VII of Figure 3.
Figure 8 is a fragmentary and schematic cross-sectional view of
~0 the propulsion system of Figure 3~ taken along the line VIII-~III of Figure 3.
Figure 9 is a fragmentary schematic cross sectional view of the
propulsion system of Figure 3, taken along the line IX~-IX of Pigure 3.
Airplane 11, shown in Figures l, 2 and 6, has a fuselage 13 cmd
tail section 15 of general configuration common to many types of airplanes.
As shown in Figure 2, the main landing gear 16 folds inside a compartment
18 under each wing 17 during flight. Each wing 17 extends laterally from a
pair of wing/nacelles 19 hereafter called nacelles. There are two nacelles,
each mounted on a respective opposite side of the :Euselage 13. Nacelles
19 ha~e arl upper surface 21 and a lower surface 23. These surfaces are cur-
vilinear when vie~ed in a longitudinal vertical section, as shown in Figures
3-5, but generally straight when viewed in a vertical lateral section, as
shown partially in Figures 7~9. The ~Ipper surface 21 and lower surface 23
of each nacelle 19 serve as upper andlower surfaces of a ducted airfoil.
Within each nacelle l9, a vertical partition 2S separates the
nacelle into -two compartments. Each compartment has a generally rectangular
inlet 27. The nacelle outlet or no~le is also rectangular. The power means
for forcing air through nacelle l9 comprises a turbofan engine, having a fan
29 and turbine engine 30 housed in each compartment. Each turhofan engine
is a high bypass ratio, low fan pressure ratio engine of generally conventional
design. The fan p-ressure ratio is preferably about 1.2 to 1.8 and the nozzle
pressure ratio is approximately the same thus producing a higher than ambient
static pressure flow of thrust producing exhaust gas.
Referring to Figures 3-5 and 7-9, a shroud 31 is attached to the
rear of the turbine engine 30 and extends rearward. As shown also in Figure 6
in phantom, shroud 31 commences at the turbine engine exit as a cylindrical
duct~ gradually flattening as it proceeds to the rear. At the trailing edge
of the nacelle upper surface 21, the passage formed by shroud 31 is in a
general rectangular shape of width greater than height. Shroud 31 contains
all of the hot exhaust from the turbine engine 30, indicated in Figures 3-5 as
33. Exhaust air from the fan 29, indicated in Figures 3-5 as 35, passes
through the interior 37 of nacelle l9. As shown in Figure 7, forward of the
commencement of shroud 31, the fan exhaust 35 passes around the housing for
turbine engine 30, being split at the top by a portion of the housing connected
to the nacelle interior surface 37. Further downstream, as shown in Figure 9,
the ~an exhaust 35 passes beneath the shroud 31.
Referring to Figures 3-5, a plurality of flaps are pivotally secured
to the nacelle outlet ~or vectoring the exhaust by turning i-t between a hori-
~ontal flight positî.on and a vertical flight position. An upper :Elap 39 is
mounted adjacent the trailing edge of the nacelle upper surface 21. Flap 39
is pivotal from the position shown in Figure 3 to that sho~n in Figure 5, and
is in the shape of an airfoil. Flap 39 includes a pair of vanes 41, 43 rigidly
secured to the upper leading edge of flap 39. Vane 41 is considerably shorter
in cord length than flap 39 and is sealed against the trailing edge of the
nacelle upper surface 21. Vane 41 moves against this trailing edge while
pivoting from the position shown in Figure 3 to that shown i.n Figure 5. Vane
43 is mounted between flap 39 and vane 41, and is also considerably shorter in
cord length than flap 39. An upper nozzle or slot 45 exists between vanes 41
and 43. An intermediate nozzle or slot 47 exists between vane 43 and flap 39.
Vane 41 leads~zane 43 slightly~ and vane 43 leads flap 39. Shroud 31 terminates
at the upper slot 45. Intermediate slot 47 receives a portion of fan exhaust
35, discharging it over the upper surface of flap 39. Engine turbine exhaust
33 is discharged from upper slot 45~ also over the upper s~rface of flap 39.
Vanes 41 and 43 should be considered as integral parts of flap 39 and pivot
directly with it. Slots 45 and 47 should be considered to be found in the
leading edge of upper flap 39. Vanes 41~ 43 serve to more efficiently turn
a portion of the fan exhaust and engine turbine exhaust as it exits from slots
45 and 47 respectively and flows over the upper surface of flap 39.
A lower flap 49 is pivotally mounted to the nacelle lower surface
23. Flap 49 is in the shape of an airfoil and pivots from the position shown
in Figure 3 to that shown in Figure 5. An intermediate flap 51 î.s pivotally
mounted to the nacelle 19. Intermediate flap 51 is in the shape of an airfoil
and is pivotal from the position shown in Figure 3 to that shown in Figure
5. In the position shown in Figure 5, a lower slot 53 is formed between the
leading edge of intermediate flap 51 and the trailing edge of upper flap 39.
Fan flow out slot 53 tends to energize the flow over flap 39 and effect
efficient flow turning over the external surface of flap 51.
Each compartment within each nacelle 19 has a separate and identical
set of flaps. The width of the flaps and the vertical distance across the
nacelle outlet are selected to provide a high aspect ratio opening at slots
45 and 47. That is, the width is much greater than the height.
In operation, in the horizontal flight position as shown in Figure
3, upper flap 39, along with its vanes 41, 43, is generally aligned with the
nacelle upper surface 21. That is, flap 39 continues the airfoil upper
surface at generally the same rate of curvature as contained on the trailing
portion of the nacelle upper surface 21. Upper flap 39 forms the trailing
edge of the airfoil upper surface in this position. Hot engine turbine ex-
haust 33 is ducted through shroud 31 to the upper slot 45. A portion of the
fan exhaust is discharged through the intermediate slot 47. The discharges
through these slots retard boundary layer separation on the flap external
surfaces and increase flow over the wing/nacelle by jet pumping action, as
shown by the longer dashed lines 54 in the drawing. In this position, lower
flap 49 and intermediate flap 51 are generally aligned with the nacelle lower
surface 23. They continue the airfoil lower surface at generally the same
rate of curvature that exists on the trailing portion of the nacelle lower
surface 23. Upper flap 39 and intermediate flap 51 define a horizontal flight
main thrust nozzle 56 through which the majority of the fan exhaust 35 is dis-
charged. IN the horizontal flight position, no additional flaps are located
in the horizontal flight main thrust nozzle 56, avoiding unnecessary drag.
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In the horizontal 1ight position, the trailing edges of upper flap 39 and
intermediate flap 51 are in approximately the same vertical plane. The
height of the horizontal flight main thrust nozzle 56 is approximately one-
half its width.
Figure 4 illustrates a ~.ransition and STOI, position. The pivoting
of the flaps from the position shown ;n Figure 3 to that shown in Figure 5
is continuous with no automatic stop, thus the position sho~l in Figure 4 is
one of an infinite number of transition positions. In the position shown
- in Pigure ~, upper flap 39 has turned downwardly, turning along with it its
vanes 4] and 43, as can be seen as referring *o reference pivok point 55.
Lower flap 49 has turned downward slightlyg although not noticeable by refer-
ence to its reference pivot point 57. Intermediate flap 51 has moved away
from the lower flap 49 and now splits the majority of the fan exhaust 35 into
two separate flow streams, as shown by its reference pivot point 59. Lower
flap 49 now becomes the trailing edge of the airfoil lower surace. ~oth
the turbine engine exhaust 33 and fan exhaust 35 incline downward and combine
aft0r passing through the flaps.
The vertical or upward flight position, used for vertical or sharply
angled take-off and landing, is shown in Figure 5. In this position, upper
flap 39 and its vanes 41, 43 remain i31 approximately the same position, as
shown in Figure 4 with only a small amount of additional movement. Lower
f]ap 49 turns downward to a greater degree. Note that the upper surface of
lower flap 49 and the lower surface of the nacelle interior 37 form a large
radius of curvature to promote turning efficiency. Intermediate flap 51 has
pivoted downward further and now has positioned itself to become a part of
the airfoil upper surface. Intermediate flap 51 and lower flap 49 define a
vertical flight main thrust nozzle 55 that discnarges the majority of the fan
exhaust 35. All of the engine turbine exhaust 33 continues to discharge
~hrough the upper slot 45. A portion of fall exhaust 35 discharges through
the intermediate slot 47, and another portion through lower slot 53. Air
flowing through these three slots or nozzles helps prevent separation of the
stream of air 54 flowing over -the airfoil upper surface and induces super
circulation or jet pumping of air over the wing. Discharge of a portion of
the fan exhaust 35 at the outside of the turn through slots 47 and 53 pre-
vents the internal formation of thrust destroying contrarotating vortices.
The thrust potential of the portion of fan exhaust 35 that is bled through
slots 47 and 53, and the *urbine exhaust 33 through slot 45, is recovered by
jet n~zzles formed cat the slot exits. The flaps are positioned so that the
engine turbine exhaust 33 combines with the fan exhaust 35 after exiting
through the upper slot 45. In the vertical flight posi~ion, the trailing
edges of the intermediate flap 51 and lower flap 49 are substantially in the
same horizontal plane. The height of the ver~ical flight mai.n thrust nozzle
58 is approximately one-half its wic7th.
The sum of the areas of slots 45, 47 and horizontal flight main
thrust nozzle 56 equals the sum of the areas of slots 45, 47, 53 and vertical
flight main thrust nozzle 58. Also, these sums equal all of the sums o:E the
areas of slots 45, 47 and the streams of fan air 35 on both sides of i.nter--
mediate flap 51 for all transition positions. The to~al nozzle area normally
remains cons~ant through all positions, maintaining a constant power match
between fan 29 and turbine engine 30. If desirecl, the total -fan nozzle area
can be varied in flight according to a predetermi.ned schedule, however, by
independently moving certain of the flaps, as a means for thrust control.
In the preferred embodiment, the engine turbine exhaust 33 will
comprise only approximately 13% of the total exhaust flow. About 10% of the
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63
fan exhaust 35 is discharged through intermediate slot 47, regardless of the
flap positi.ons. In the vertical flight position, an additional portion,
approximately 5%, of the fan exhaust 35 is discharged through the lower slot
53.
The degree of pivot of the flaps may be determined with reference
to the longitudinal axis 61 of the aircraft. For reference purposes9 the
angle of inclination of the flaps with respect to the axis 61 is determined
herein by drawing a line from the trailing edge of each flap through the
approximate center of thickness of each flap. Angle x represents the angle
between this center line and ~he longi*udinal axis 61 for upper flap 39.
Angle ~ represents the same angle measurement for the lower flap 49, and
angle ~ represents the same angle measurement for the intermediate flap 51.
; In the horizontal flight posi~ion, sho~n in Figure 3, angle ~ is approxima~ely
negative 23 degrees, angle ~ is approximately negative 3 degrees, and angle
~ is approximately positive 8 degrees. In the transition position shown in
Figure 4, angle ~ has changed to approximately nega~ive 52 degrees, angle
to approximately negative 8 degrees, and angle ~ to approximately negative
; 46 degrees. In the vertical flight posi*ion, shown in Figure 5, angle ~ is
approximately negative 60 degrees, angle ~ i5 approximately negative 63 de-
grees9 and angle ~ îs appro~imately negative 110 degrees. Consequently, be-
tween the horizontal and vertical flight positions, the upper flap 39 pivots
a total o:~ approximately 37 degrees, the lower flap ~9 pivots a total of
approximately 60 degrees and the intermediate ~lap 51 pivots a total o
approximatel~ 118 degrees.
It should be apparent tha~ an i.nvention having significant i~prove-
ments has been provided. The propulsion system with its system of -flaps per-
mits design of a highly efficient vertical and shorttakeoff and landing air-
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plane. The discharge of high energy air over the upper surface Elaps retards
boundary layer separation and induces super circulation around the airfoil.
The flaps are located so tha~ during horizontal flight and in vertical flight,
the main thrust nozzles 56 and 58 are free of drag creating intermediate flaps.
The slots 47 and 53 provided in the vertical flight position bleed-off internal
vortices formed by the fan exhaust air stream being turned by the internal noz-
zle wall, making turning of the exhaust highly efficient. Separating the en-
gine turbine exhaust from the fan exhaust promotes higher propulsion system
augmentation ratio by avoiding the interaction of two streams of different pres-
sures.
It will be apparent from the foregoing ~see especially drawingsFigures 3, 4 and 5) that the main or primary khrust nozzle means ~56 or 58; or
the combination of the nozzles respectively between flaps 39-51 and 51-4~,
i~e., between flaps 39 and 49, in transitional flight) discharge a primary vr
major portion of the exhaust or exhaust gas flow. Likewise jet or thrust noz-
zle means 47 in horizontal and transitional ~i.e.~ more upward or downward an-
gled) flight and jet or thrust nozzle means 47 and 5~ in vertical or upward
and downward flight are secondary in discharging a minor or bleed-off portion
of the exhaust gas flow. Auxiliary nozzle 45, and the exhaust exiting from
it that comes from the engine core or turbine, may be considered a part of the
primary thrust nozzle means and the major portion of the exhaust gas flow res-
pectively, all of the referred to nozzles together making up the exhaust noz-
zle means for the exit of the exhaust from the airplane.
It can be seen that turning of the exhaust commences immediately
downstream of the fan discharge. Thus, those skilled in the art, from at~ention
to the drawings and text, will realize that an internal build-up of dynamic
pressure will begin to occure in the vic;nity of the outside wall of the turn
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due to impingement of the gas against the outer wa~ls of the turn, and that
this build-up tends to cause the thrust reducing contrarotating vortices to
form in the flow. These will be relieved or prevented, however, in that the
slot or nozzle 47 is positioned to effect bleed-off downstream of the leading
edge or commencement of the turn, i.e.~ where the obstruction to flow re-
sulting from the build-up tends to occure, and will be relieved or prevented
again by nozzle 53 downstream thereof where like obstruction may re-occur
for like reasons.
It can also be clearly seen in the drawings that the auxiliary
thrust nozzle 45 and secondary thrust nozzle means (slots 47 and 53) are tan-
demly arranged along the turn and respectively direct the engine core (turhine)
exhaust and the bleed-off exhaust substantially tangentially to and over the
curved lifting surfaces formed by the flaps, with the core exhaust close a~ove
the bleed-off, i.e., the bleed-off between the core exhaust and downstream flap
surfaces. These flows individually and together induce supercirculation over
the nacelle and retard boundary layer separation theref~m during horizontal
and upward angled flight. It is ~rther apparent that such auxiliary thrust
nozzle and secondary thrust nozzles are directionally movable so as to direct
the core exhaust and bleed-off to flow generally parallel and close to the
major portion of the exhaust flow at all positions of flow whereby the core
exhaust and bleed-off are turned together with the rest oF the major portion
o:F the eYhaust 10w to provide, in its effect, a substantially unitary or co-
herent exhaust stream passing from said airplane horizontally and at all
turning angles between horizontal and downward flow, i~e., between horizontal
and upward flight positions. (See Fi~ures 3, ~ and 5.)
As is clear from the drawings, each of the nozzles at all posi-
tions of turning or to which directed for exhaus-t of the gas flow, has its noz-
zle constriction or throat pos;tioned so as to be maintained at all times
substantially at and forming (i.e., coincides with~ the nozzle exit plane
unless purposely varied therefrom as indicated above. The effect is to pro-
duce the maximum oE velocity and thus thrust from the exiting flow or stream
of the exhaust gases and to cause t~rning of all of the exlting exhaust flow
through the maximum angle with the maximum velocity thereby enhancing total
thrust in all modes of f~ight and producing the coherent flow.
While the invention has been shown in only one of its forms, it
should be apparent to those skilled in the art that it is not so limited but
is susceptlble to various changes and modifications without departing from
the spirit thereof.
