Axisymmetric nozzle with gimbled unison ring

A thrust vectoring exhaust nozzle (10) includes a plurality of flaps (16-22) and seals (24-28) positioned by a unison ring (52) and flap links (54-60).

CROSS REFERENCE TO RELATED APPLICATIONS 
Attention is hereby directed to copending application "Thrust Vectoring 
Exhaust Nozzle" (U.S. Ser. No. 571,797) filed on even date herewith, now 
U.S. Pat. 5,082,182. 
FIELD OF THE INVENTION 
The present invention relates to a thrust vectoring exhaust nozzle for an 
aircraft gas turbine engine. 
BACKGROUND ART 
Variable geometry exhaust ducts for aircraft gas turbine engine 
installations frequently employ an axisymmetric arrangement of overlapping 
flap and seal members to define the periphery of the exhaust duct. By 
providing an intermediate, transverse hinge in the flap and seal members, 
prior art ducts have achieved convergent-divergent arrangements wherein 
the duct may be configured to define a variable area throat which is 
necessary for optimized engine performance, particularly in high speed 
aircraft installations using afterburning for thrust augmentation. 
Such prior art axisymmetric nozzles direct the exhaust gas aftward from the 
aircraft generally along a central axis. Certain alternative designs exist 
for attempting to provide a practical arrangement for selectively 
diverting the exhaust gas from this axial centerline in order to achieve 
vectored thrust for enhancing aircraft maneuverability. Such thrust 
vectoring nozzle configurations have typically not been adaptable to the 
axisymmetric nozzles described hereinabove and further are usually limited 
to redirecting exhaust gas in only a single plane. An additional drawback 
of prior art vectoring nozzle has been the increased weight of the 
actuators and exhaust gas directing surfaces at the aftmost portion of the 
exhaust duct and aircraft, thus adding additional weight at the most 
undesirable location in the aircraft due to stability and balance 
considerations. 
What is needed is a thrust vectoring exhaust duct design which is adaptable 
to both convergent-divergent exhaust arrangements as well as lightweight, 
axisymmetric configurations. 
SUMMARY OF THE INVENTION 
The present invention provides a thrust vectoring, axisymmetric nozzle for 
selectively vectoring the discharge direction of a stream of exhaust gas 
from a gas turbine engine or the like. Such nozzles may be used in an 
aircraft to enhance maneuverability without increasing the size or losses 
resulting from typical aircraft control surfaces. 
The invention comprises a plurality of longitudinally extending control 
flaps defining a moveable exhaust duct. Each flap is secured by a 
universal joint at the upstream end to a discharge throat and at a point 
downstream of the universal joint to one end of a positioning link. Each 
positioning link is secured at the other end to a moveable, coaxial unison 
ring whereby the entire control flap assembly can be collectively 
positioned. 
The unison ring may be translated axially with respect to the engine 
centerline as well as tilted or skewed with respect thereto, thus causing 
the nozzle according to the present invention to collectively position the 
individual control flaps so as to vector the exhaust gas stream relative 
the nozzle central axis, or vary the nozzle discharge flow area as defined 
collectively by the plurality of flaps. 
The nozzle according to the present invention provides the advantages of 
lightweight yaw and pitch thrust vectoring and a high degree of 
compatibility with current nozzle installations. The nozzle according to 
the present invention is also highly compatible with a variable throat 
area, convergent-divergent exhaust configuration, wherein the upstream end 
of each flap is secured to a corresponding moveable convergent flap member 
.

DETAILED DESCRIPTION 
Referring now to the drawing figures, and in particular to FIG. 1 thereof, 
a nozzle arrangement 10 according to the present invention may be viewed 
in perspective. The nozzle 10 includes a static upstream structure 12 
integral with the airframe for supporting the outlet duct 14 according to 
the present invention. 
The variable configuration outlet duct 14 includes a plurality of control 
flap members 16, 18, 20, 22 which collectively form the duct 14. In the 
FIG. 1 embodiment, a like plurality of seal members 24, 26, 28 are 
disposed circumferentially intermediate adjacent flap members and are 
maintained in a centered positioned therebetween by corresponding pivot 
links 30, 32, 34. Each control flap 16-22 is supported at the upstream end 
thereof by a universal joint 36, 38, 40 which permits the flap to pivot in 
the radial and circumferential planes with respect to the nozzle central 
axis 42. The trailing edges 44, 46, 48, 50 of the flaps 16-22 define the 
nozzle outlet from which high speed exhaust gases issue. The duct 14 may 
be reconfigured by collectively positioning the individual flap members 
16-22 so as to selectively vector the discharge direction of the exhaust 
gases relative the nozzle central axis 42. This collective reconfiguration 
is accomplished by repositioning a unison ring 52 which is connected to 
each of the flap members 16-22 by flap links 54, 56, 58, 60. 
Each flap link 54-60 is secured at each end by hinge joints so as to move 
the individual flap member 16-22 in the radial and circumferential plane 
about the corresponding upstream universal joint. 
The unison ring 52 is supported relative to the static structure 12 by 
means of at least three cam races 62 which receive a corresponding number 
of rollers or pins 64 secured to the unison ring 52. The races 62, 64 
prevent circumferential movement of the unison ring 52 while permitting 
portions of the ring to be moved axially by means of actuators 66 secured 
between the pin 64 and static structure 12. 
As will be appreciated by viewing FIG. 1, the exhaust duct according to the 
present invention may be reconfigured in a variety of ways by translating 
the unison ring axially by means of the actuator 66. For example, the 
collective outlet area defined by the trailing edges 44-50 of the flap 
16-22 may be varied by translating the entire unison ring 52 aftward, 
thereby collectively rotating the flaps radially inward. It will also be 
appreciated by those skilled in the art that the entire duct 14 may be 
skewed with respect to the fixed axis 42 by skewing the unison ring 52, 
that is by displacing portions of the circumference of the ring 52 at 
differing axial locations, thus, pitch and yaw vectoring, as well as 
combinations thereof, may be accomplished. 
FIGS. 2 and 3 show plan and sectional views of the flap 18, cam race 62, 
and pin 64. Seal member 26 is shown disposed in FIG. 2 between flaps 18 
and 20. The seal 26 is located between the flaps 18 and 20 by the pivot 
link 32 which includes a central pivot 68, a spanner link 70 and sliders 
72, 74 which are engaged with corresponding tracks 76, 78 on the flaps 18, 
20. The seal 26 is supported at the upstream end thereof by a universal 
joint 80 which is similar to the joints 36, 38 supporting the flaps 18, 
20. 
The side view of FIG. 3 shows the control flap 18, flap link 56, unison 
ring 52 and the other system components. The flap universal joint 36 is 
also shown as being sealed against leakage of gas by overlapping leaf 
seals 82. 
For high performance jet aircraft it is common to employ a variable throat 
area, convergent-divergent exhaust duct wherein the divergent section, 
represented by the duct 14 according to the present invention, is disposed 
downstream of a convergent section which is operable to define a variable 
area throat which is coincident of the upstream end of the divergent duct 
14. Prior art convergent ducts include a plurality of convergent flap 
members 102 and convergent seal members 104 alternatively disposed to 
collectively form the convergent duct 106 and means (not shown) for 
selectively positioning the convergent flap members and convergent seal 
members so as to define a variable area throat. Such convergent duct 
arrangements are well known in the art and will not be described in detail 
herein. 
The divergent duct 14 according to the present invention, is well adapted 
to operate with such variable area convergent duct arrangements, with the 
upstream ends of the flaps 16-22 being secured to the downstream ends of 
the corresponding convergent flap members 102 by means of the universal 
joints 36-40 as described hereinabove. By properly positioning the unison 
ring 52 in conjunction with the movements of the convergent duct flaps, 
the duct 14 according to the present invention is well able to provide 
vectored thrust to the airframe under widely varying conditions of engine 
thrust, nozzle throat area, etc. 
FIG. 4 shows an alternative universal joint design for supporting the 
upstream ends of the flap 16-22 wherein a double hinge arrangement is 
used. Shown in plan view, the joint 84 of FIG. 4 uses a first hinge 86 
having a hinge line essentially tangential to the circumference of the 
duct 14 and a second hinge 88 having a hinge line oriented radially with 
respect to the duct 14. The first hinge 86 permits the flap 18 to rotate 
in a radial plane with respect to the nozzle centerline 42, while the 
second hinge 88 permits rotation of the flap 18 in the corresponding 
circumferential plane. The universal joint 84 as shown in FIG. 4 thus 
provides the degree of freedom necessary to accomplish the variable 
exhaust duct according to the present invention as well as offering the 
advantage of better sealing between the upstream structure 102 and the 
divergent control flaps 18 and seals of the duct 14 according to the 
present invention.