Engine propulsion system and methods of assembling the same

A method for exhausting gas from an aircraft engine assembly is provided. The method includes coupling a first exhaust duct in fluid communication only to a first engine. The first exhaust duct includes a primary outlet and a secondary outlet. The method further includes coupling a second exhaust duct in fluid communication only to a second engine. The second exhaust duct includes a primary outlet and a secondary outlet. The method also includes aligning a portion of the first engine secondary outlet concentrically within a portion of the second engine secondary outlet.

BACKGROUND OF THE INVENTION

This invention relates generally to aircraft turbine engines, and more specifically, to propulsion systems used with a multiple turbine engine assembly.

In some known aircraft, propulsion systems are used to control a flow of exhaust gases for a variety of aircraft functions. For example, such systems can be used to provide thrust for Vertical Take-Off and Landing (VTOL), Short Take-Off Vertical Landing (STOVL) and/or Extreme Short Take-Off and Landing (ESTOL) aircraft. At least some known STOVLs and ESTOLs use vertical thrust posts to facilitate short and extremely short take-offs and landings. In aircraft using vertical thrust posts or nozzles, exhaust from a common plenum is channeled to thrust posts during take-off and landing operations, and, at a predetermined altitude, through a series of valves, the exhaust is channeled from the common plenum to a cruise nozzle.

Other known STOVLs and ESTOLs use rotor tip gas reaction driven rotors and rotor tip driven rotors to facilitate vertical take-offs and landings. During flight, some such rotor-driven aircraft can transform into fixed wing aircraft. In some of such aircraft, the engine exhaust gases may also be used to control yaw through aft mounted variable area exhaust nozzles. Other known aircraft use the propulsion system to reduce drag on the aircraft, and/or cool aircraft wings. In such aircraft, gases are channeled through the wings of the aircraft and discharge through a plurality of openings defined in a trailing portion of the wing. Such aircraft are sometimes referred to as having “blown wings”.

Because single engine assemblies may limit the survival capabilities of the aircraft when engine power loss occurs, each of the above described propulsion systems may be preferred to be used with a multiple, especially a dual, engine assembly. In a single engine assembly, the engine exhausts into a plenum where it is then channeled via the propulsion system for use by the aircraft. In a dual engine propulsion control system, each engine exhausts into a common plenum wherein the exhaust is channeled for use by the aircraft. However, because the exhausts are mixed in a common plenum, if one engine stalls, fails, or is in any way rendered inoperable, the exhaust flow from that engine may not enter the plenum. The associated pressure drop in the plenum may adversely affect the operation of the propulsion system and valves must be provided to prevent back flow of exhaust gases into the inoperable engine.

A control system must also be provided to actuate these valves at a high slew rate to prevent the operable engine from stalling. Such a control system capability has been envisioned but is not known to have been demonstrated. Such a control system would be required to make major airflow adjustments in the propulsion system that may include closing valves to prevent loss of plenum pressure through the inoperable engine and to attempt to redirect nozzle areas to facilitate retaining flight stability. Such significant readjustments of nozzle area configuration may lead to the stall of the operational engine and may cause a complete loss of lift. Furthermore, it may be difficult for the control system to increase the power setting of the operable engine to an emergency level.

Because of the time and cost of developing a control system and implementing the mechanical complexity created by such propulsion systems having multiple engines exhaust into a common plenum, such propulsion systems may be much more costly than those used with single engine assemblies. For example, to provide exhaust control, such propulsion systems include a plurality of sensors and valves that can be selectively actuated to isolate an inoperable engine. More specifically, known propulsion systems used with dual engine assemblies include a plurality of butterfly valves and actuation systems that direct the exhaust gases in the event of an engine power loss. The valves enable an inoperable engine to be isolated to prevent back-flow through the inoperative engine. In addition, the isolation valves enable emergency flight capability and limited aircraft control with an inoperable engine. However, because such valves must operate at high temperatures, such valves and associated actuation systems may require large actuation forces. Furthermore, in known propulsion systems, once the valves have been closed to isolate an inoperable engine, it is not possible to attempt to restart an inoperable engine.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect a method for exhausting gas from an aircraft engine assembly is provided. The method includes coupling a first exhaust duct in fluid communication only to a first engine. The first exhaust duct includes a primary outlet and a secondary outlet. The method further includes coupling a second exhaust duct in fluid communication only to a second engine. The second exhaust duct includes a primary outlet and a secondary outlet. The method also includes aligning a portion of the first engine secondary outlet concentrically within a portion of the second engine secondary outlet.

In another aspect an engine assembly is provided. The engine assembly includes a first engine including a first exhaust duct coupled in fluid communication only to the first engine. The first exhaust duct includes a primary outlet and a secondary outlet. The engine assembly further includes a second engine including a second exhaust duct coupled in fluid communication only to the second engine. The second exhaust duct includes a primary outlet and a secondary outlet. A portion of the first engine secondary outlet is aligned substantially concentrically within a portion of the second engine secondary outlet.

In a still further aspect a propulsion system for an aircraft is provided. The propulsion system includes a first engine including a first exhaust duct coupled in flow communication only to the first engine. The propulsion system further includes a second engine including a second exhaust duct coupled in flow communication only to the second engine. The first exhaust duct includes a primary exhaust and a secondary exhaust. The second exhaust duct includes a primary exhaust and a secondary exhaust. A portion of the first engine secondary exhaust is aligned substantially concentrically within a portion of the second engine secondary exhaust.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a top schematic view of an exemplary propulsion system100that may be used with a multiple engine assembly10used with a VTOL, ESTOL and/or STOVL fixed wing aircraft (not shown). In the exemplary embodiment, engine assembly10includes a first engine102and a second engine104. Alternately, propulsion system100can be used with engine assemblies10having more than two engines. In an exemplary embodiment, engine102includes a first inlet106and engine104includes a second inlet108. Inlets106and108enable air to be channeled into engines102and104, respectively. Exhaust gases110from first engine102are discharged through a first exhaust duct114and exhaust gases112from second engine104are discharged through a second exhaust duct116.

In the exemplary embodiment, exhaust duct114is coupled in flow communication to a first lift duct118and to a first cruise duct120. A first passageway122is coupled to duct114to enable exhaust gases110to be channeled from first duct114to first lift duct118. In the exemplary embodiment, at least a portion of first lift duct118is oriented substantially perpendicularly to a center line124that extends between engines102and104. Engine assembly10and propulsion system100are symmetric on each side of center line124. In the exemplary embodiment, first lift duct118is coupled in flow communication to a starboard lift nozzle126and to a port lift nozzle128. Alternately, lift nozzles126and128may be positioned other than starboard and port of center line124. Furthermore, alternately, propulsion system100can have more or less than two lift nozzles126and128. In the exemplary embodiment, lift nozzles126and128, lift nozzles136and138, and cruise nozzles130and142, described in more detail below, are each variable area nozzles. The design, construction, and control of variable area nozzles are known in the art. The nozzles126,128,130,136,138, and142may utilize clamshell or shutter valve designs as is known in the art. Actuation of nozzles126,128,130,136,138, and142may be hydraulic, electric, or any other method known in the art. Alternately, propulsion system100can have more or less than two lift nozzles126and128. Lift nozzles126and128extend from lift duct118generally toward the ground (not shown). More specifically, in the exemplary embodiment, lift nozzles126and128are each oriented such that during pre-defined engine operations, exhaust gases110discharged therefrom facilitate enabling generally vertical take-off and landing (VTOL) of the aircraft, short take-off and vertical landing (STOVL), and/or extremely short take-off and landing (ESTOL).

First cruise duct120is coupled in flow communication to duct114and extends generally parallel to center line124. In the exemplary embodiment, during pre-defined engine operations, exhaust gases110are channeled from duct114into cruise duct120, wherein the gases110may be discharged through a first cruise nozzle130to generate thrust from the aircraft. More specifically, first cruise nozzle130facilitates propelling the aircraft in a direction that is generally parallel to center line124.

In the exemplary embodiment, second duct116is coupled in flow communication to a second lift duct132via a second passageway134. During pre-defined engine operations, exhaust gases112discharged from engine104may be channeled from duct116through passageway134to lift duct132. In the exemplary embodiment, at least a portion of second lift duct132is oriented substantially perpendicularly to center line124. Moreover, in the exemplary embodiment, second lift duct132is coupled in flow communication to a second starboard lift nozzle136and to a second port lift nozzle138. Alternately, lift nozzles136and138may be positioned other than starboard and port of center line124. Furthermore, alternately, propulsion system100can have more or less than two lift nozzles136and138. Lift nozzles136and138extend from lift duct132and are oriented such that exhaust gases112discharged therefrom are discharged generally towards the ground. More specifically, in an exemplary embodiment, second lift nozzles136and138are each oriented such that during pre-defined engine operations, exhaust gases112discharged from lift nozzles136and138facilitate enabling generally vertical take-off and landing of the aircraft, STOVL, and/or ESTOL. Furthermore, in the exemplary embodiment, a portion of each second lift nozzle136and138extends substantially concentrically within a portion of each of lift nozzles126and128, respectively. Alternately, a portion of each of first lift nozzles126and128extends substantially concentrically within a portion of each of lift nozzles136and138, respectively.

In the exemplary embodiment, second duct116is coupled to a second cruise duct140. Cruise duct140extends generally parallel to center line124and is positioned adjacent to cruise duct120. In the exemplary embodiment, during pre-defined engine operations, exhaust gases112are channeled from second duct116into cruise duct140wherein the gases112may be discharged through a second cruise nozzle142. More specifically, second cruise nozzle142facilitates propelling the aircraft in a direction that is generally parallel to center line124.

For generally vertical take-off and landing, STOVL, and/or ESTOL, cruise nozzles130and142are closed from a first position to a closed second position, and lift nozzles126,128,136, and138are opened from a first position to an open second position. Control design and control laws required for progressive actuation of nozzles126,128,130,136,138, and142during pre-defined engine operations are known in the art. When first cruise nozzle130is closed, exhaust gases110are forced from first duct114into first passageway122wherein the gases110are discharged into first lift duct118. Exhaust gases110are then discharged from first lift duct118through first lift nozzles126and128to facilitate vertical thrust. Similarly, in the exemplary embodiment, when second cruise nozzle142is closed, exhaust gases112are forced from second duct116into second lift duct132via second passageway134wherein exhaust gases112are the discharged through second lift nozzles136and138. Thrust from exhaust gases112discharged through second lift nozzles136and138combine with exhaust gases110discharged through first lift nozzles126and128to facilitate generally vertical take-off and landing, and/or STOLV, and/or ESTOL of the aircraft.

Once the aircraft has reached a pre-determined altitude, in the exemplary embodiment, cruise nozzles130and142are opened from the closed second position to the first position while lift nozzles126,128,136, and138are closed from the open second position to the first position. With lift nozzles126,128,136, and138closed, exhaust gases110and112are channeled from first duct114and second duct116, respectively, into cruise ducts120and140, respectively, wherein exhaust gases110and112are discharged through cruise nozzles130and142, respectively. As exhaust gases110and112are discharged through cruise nozzles130and142, respectively, the thrust from the exhaust gases110and112facilitates propelling the aircraft in a direction that is generally parallel to center line124. During pre-defined engine operations in which propulsion in a direction that is generally non-parallel to center line124is changed to propulsion in a direction that is generally parallel to center line124, propulsion system100enables the inoperability of engine102or104without unbalanced lift or thrust forces. Furthermore, in the exemplary embodiment, propulsion system100enables controlled propulsion in a direction that is generally parallel to center line124or controlled decent in a direction that is generally non-parallel to center line124.

In the exemplary embodiment, each engine includes a starboard lift nozzle and a port lift nozzle that facilitates providing balanced lift. For example, if one engine is rendered inoperable during aircraft operation, the exhaust gases from the other engine enables a continued, balanced lift to be provided. The maintenance of balanced lift does not require any control intervention and/or the actuation of any exhaust valves to redirect exhaust gases, either internally or at the lift nozzles. The total lift may be reduced, but in a balanced and controlled manner due to the symmetric position of the lift nozzles and the symmetric geometry of the exhaust gas supply to the nozzles. A simple control command can increase the power of the functioning engine to potentially facilitate allowing continued flight. In the above-described exemplary embodiment, either engine may be rendered inoperable, yet the propulsion system may facilitate maintaining control of the aircraft, and/or increase the probability of aircraft survival, without enhanced control technology and the placement of air control valves in the internal flow circuits.

When the aircraft is in forward flight and wing borne, the loss of engine power will not require any valves present in the system to be actuated to prevent back flow from the functioning engine to the inoperable engine. The forward thrust will be maintained via the cruise nozzles without any control system action. Furthermore, an effort to restart the inoperable engine could be made without endangering the continued operation of the aircraft. Moreover, during the transition from channeling gases through the lift nozzles to channeling gases through the cruise nozzles, the propulsion system allows the inoperability of either engine without unbalanced lift or thrust forces such that operation of the aircraft may be continued.

FIG. 2is a top schematic view of an alternate embodiment of a propulsion system200that may be used with a rotary wing aircraft that transitions to a fixed wing aircraft having a multiple engine assembly20.FIG. 3is a portion of propulsion system200shown inFIG. 2.FIG. 4is a perspective view of an exemplary plenum configuration that may be used to supply exhaust gases to the circuit associated with rotor blade202of propulsion system200shown inFIG. 2.

In the exemplary embodiment, engine assembly20includes a rotor blade202, a first engine204, and a second engine206. Alternately, propulsion system200can be used with engine assemblies20having more than two engines. In an exemplary embodiment, engine204includes a first inlet208, and second engine206includes a second inlet210. Inlets208and210enable air to be channeled into engines204and206, respectively. Exhaust gases212from first engine204are discharged through a first exhaust duct216coupled in flow communication to first engine204. Similarly, exhaust gases214from second engine206are discharged through a second duct218coupled in flow communication to second engine206.

In the exemplary embodiment, first exhaust duct216is coupled in flow communication to a first rotor duct220and to a first cruise duct222. First rotor duct220is coupled in flow communication to a first rotor plenum224. In the exemplary embodiment, at least a portion of rotor plenum224is oriented generally perpendicularly and upward from a center line226that extends between engines204and206. Engine assembly20and propulsion system200are symmetric on each side of center line226. Rotor plenum224is coupled in flow communication to a plurality of first rotor blade ducts228that extend through rotor blade202in a direction that is generally oriented from a rotor plenum center235to rotor blade ends236. In the exemplary embodiment, rotor plenum224is coupled in flow communication to four first rotor blade ducts228, two of which extend through one portion of rotor blade202, and the remaining first rotor blade ducts228extend through the remaining portion of blade202. Alternately, propulsion system200may include more or less than four first rotor blade ducts228.

Each of the plurality of rotor blade ducts228is coupled in flow communication to a rotor nozzle230. In the exemplary embodiment, each rotor nozzle230has a variable area. More specifically, in the exemplary embodiment, the area of each rotor nozzle230is varied via an upper flap232and a lower flap234. Upper flap232and lower flap234are rotatably coupled to an end portion236of rotor blade202. Upper flap232and lower flap234can be rotated with respect to rotor blade202to facilitate increasing or decreasing the area of rotor nozzles230. In the exemplary embodiment, a plurality of rotor nozzles230share a single upper flap232and lower flap234to facilitate uniformly controlling the area of a plurality of rotor nozzles230. Actuation of rotor tip nozzles230, upper flap232, and/or lower234may be hydraulic, electric, or other known actuation devices. The control of rotor tip tip nozzles230, upper flap232, and/or lower234is known in the art.

In the exemplary embodiment, during pre-defined engine operations, exhaust gases212may be used to facilitate directional control of the aircraft. More specifically, in the exemplary embodiment, first cruise duct222is coupled in fluid communication to a first yaw duct238and to a first cruise nozzle240. In the exemplary embodiment, cruise nozzles240and256, described in more detail below, are each variable area nozzles. The design, construction, and control of variable area nozzles are known in the art. Nozzles240and256may utilize clamshell or shutter valve designs as is known in the art. Actuation of nozzles240and256may be hydraulic, electric, or any other method known in the art. Moreover, first cruise duct222includes a starboard yaw control242defined therein. In the exemplary embodiment, yaw duct238is oriented generally perpendicularly to cruise duct222, and is coupled to a port yaw control244. During pre-defined engine operations, exhaust gases212are discharged from first cruise duct222, through at least one of starboard yaw control242, port yaw control244, and cruise nozzle240.

In the exemplary embodiment, second exhaust duct218is coupled in flow communication to a second rotor duct246and to a second cruise duct248that is positioned adjacent to cruise duct222. Second rotor duct246is coupled in flow communication to a second rotor plenum250. In the exemplary embodiment, at least a portion of second rotor plenum250is oriented generally perpendicularly and upward from center line226. In the exemplary embodiment, a portion of first rotor plenum224extends substantially concentrically within a portion of second rotor plenum250. Alternately, a portion of second rotor plenum250extends substantially concentrically within a portion of first rotor plenum224. Second rotor plenum250is coupled in flow communication to a plurality of second rotor blade ducts252that extend through rotor blade202in a direction that is generally oriented from rotor plenum center235to rotor blade ends236. In the exemplary embodiment, second rotor plenum250is coupled in flow communication to four second rotor blade ducts252, two of which extend through one portion of rotor blade202, and the remaining second rotor blade ducts252extend through the remaining portion of blade202. Alternately, propulsion system200may include more or less than four second rotor blade ducts252. Each of the plurality of second rotor blade ducts252is coupled to one rotor nozzle230, which is described in more detail above.

In the exemplary embodiment, during pre-defined engine operations, exhaust gases214may be used to facilitate directional control of the aircraft. More specifically, in the exemplary embodiment, second cruise duct248is coupled in flow communication to a second yaw duct254and to a second cruise nozzle256. Moreover, cruise duct248has port yaw control244defined therein. In the exemplary embodiment, second yaw duct254is oriented generally perpendicularly to cruise duct248, and is coupled to starboard yaw control242. During pre-defined engine operations, at a starboard yaw control outlet258, exhaust gases212discharged through first cruise duct222combine with exhaust gases214discharged through second yaw duct254to control a yaw of the aircraft. Similarly, at a port yaw control outlet260, exhaust gases212discharged through first yaw duct238combine with exhaust gases214discharged through second cruise duct248to control yaw of the aircraft. Alternately, propulsion system200may be used to control directions other that the yaw of the aircraft. Moreover, in the exemplary embodiment, exhaust gases214may be discharged through duct218into cruise duct248, and then through at least one of starboard yaw control242, port yaw control244, and second cruise nozzle256.

For generally vertical take-off and landing, STOVL and/or ESTOL, cruise nozzles240and256are closed from a first position to a second position, and rotor nozzles230are open via moving upper flap232and lower flap234from a closed position to an open position. Movement of cruise nozzles240and256is coordinated with the movement of rotor nozzles230. Control design and control laws required for progressive actuation of nozzles230,240, and256during pre-defined engine operations are known in the art. During pre-defined engine operations, exhaust gases212are channeled from first duct216, through first rotor duct220, and then channeled into first rotor plenum224. Exhaust gases212are channeled from first rotor plenum224through first rotor blade ducts228, and are then discharged from propulsion system200through rotor nozzles230to facilitate rotating rotor blade202. Rotation of rotor blade202facilitates propelling the aircraft in a direction that is generally non-parallel to center line226.

Similarly, in the exemplary embodiment, when second cruise nozzle256is closed from a first position to a second position, and rotor nozzles230are open via moving upper flap232and lower flap234from a closed position to an open position, exhaust gases214are channeled from second duct218, through second rotor duct246, and then channeled into second rotor plenum250. During pre-defined engine operations, exhaust gases214are channeled from second rotor plenum250through second rotor blade ducts252, and then are discharged from propulsion system200through rotor nozzles230. More specifically, in the exemplary embodiment, exhaust gases212discharged through rotor nozzles230facilitate rotating rotor blade202wherein rotation of rotor blade202facilitates providing propelling the aircraft in a direction that is generally non-parallel to center line226.

Once the aircraft has reached a pre-determined altitude, in the exemplary embodiment, cruise nozzles240and256are opened from the second position to the first position while rotor nozzles230are closed via upper flap232and lower flap234. Movement of cruise nozzles240and256is coordinated with the movement of rotor nozzles230. When rotor nozzles230are closed, rotor blade202may cease rotation such that blade202is oriented substantially perpendicularly to center line226, and the aircraft transforms into a fixed wing aircraft. When the aircraft is operating as a fixed wing aircraft, upper flap232and lower flap234close to facilitate preventing exhaust gases212and214from discharging through rotor nozzles230, and to facilitate reducing drag on rotor nozzles230facing fore. With flaps232and234closed, propulsion system200may have a greater capability for propelling the aircraft at a velocity in a direction that is generally parallel to center line226. In an exemplary embodiment, a control system (not shown) may modify the pitch of rotor blade202to facilitate allowing the blade202to function more effectively as a wing.

During pre-defined engine operations, with rotor nozzles230closed, exhaust gases212and214are channeled from rotor ducts220and246through cruise ducts222and248, respectively, and then through cruise nozzles240and256, respectively. As exhaust gases212and214are discharged through cruise nozzles240and256, respectively, the thrust from the exhaust gases212and214facilitates propelling the aircraft generally parallel to center line226. In the exemplary embodiment, by opening and closing starboard yaw control242and/or port yaw control244, exhaust212and214can be used to change a yaw of the aircraft. Control design and control laws required for the actuation of yaw control242and244during pre-defined engine operations are known in the art. Alternately, exhaust gases212and214may be channeled through propulsion system200for other directional control uses.

The propulsion system described above facilitates providing a balanced loss of rotor tip thrust if either engine is rendered inoperable without requiring an aircraft/engine control system beyond what is currently known in the art. The engine exhaust gases are channeled separately from each engine to each of the rotor blade tip nozzles to facilitate providing the balanced loss of rotor tip thrust. The propulsion system also enables aircraft stability to remain uncompromised. Furthermore, the yaw flow circuit incorporates a crossover of the engine exhaust circuits to supply exhaust gases to the yaw nozzles. The crossover of the yaw circuit to each of the engine exhaust circuits facilitates maintaining the required yaw forces without any significant aircraft/engine control system action when one engine is inoperable.

FIG. 5is a top schematic view of another alternative embodiment of a propulsion system600that may be used with a multiple engine assembly60. In the exemplary embodiment, engine assembly60includes a wing602, a first engine604, and a second engine606. Alternately, propulsion system600can be used with engine assemblies60having more than two engines. In an exemplary embodiment, engine604includes a first inlet608, and second engine606includes a second inlet610. Inlets608and610enable air to be channeled into engines604and606, respectively. Exhaust gases612from first engine604are discharged through a first exhaust duct616coupled in flow communication to first engine604, and exhaust gases614from second engine606are discharged through a second exhaust duct618coupled in flow communication to second engine606.

In the exemplary embodiment, first duct616is coupled in flow communication to a first plenum duct620and to a first cruise duct622. First plenum duct620is coupled in flow communication to a first plenum624. In the exemplary embodiment, at least a portion of plenum624is oriented generally perpendicularly and upward from a center line626extending between engines604and606. Engine assembly60and propulsion system600are symmetric on each side of center line626. In the exemplary embodiment, first plenum624is configured similarly to first rotor plenum224shown inFIG. 4.

Furthermore, in the exemplary embodiment, first plenum624is coupled in flow communication to a plurality of first wing ducts628and630that extend axially through wing602and are oriented in a substantially non-parallel direction to center line626. In the exemplary embodiment, plenum624is coupled to a starboard first wing duct628and a port first wing duct630. Starboard wing duct628extends from center line626towards a wing starboard end636through one portion of wing602. Port wing duct630extends from center line626towards a wing port end640through the remaining portion of wing602. Alternately, propulsion system600may include more or less than two first wing ducts628and630. Each of first wing ducts628and630is coupled to a first wing outlet632and638, respectively. In the exemplary embodiment, starboard wing outlet632is defined on an aft side634of wing602on starboard end636. Similarly, port first wing outlet638is defined on aft side634of wing602on port end640.

Alternately, exhaust gases612may be channeled into first exhaust duct616, and air (not shown) from an engine fan (not shown) may be channeled into a first fan exhaust duct (not shown). The air from the first fan exhaust duct is discharged into first plenum624to facilitate providing fluid to wing ducts628and630at a lower temperature than exhaust gases612. In an exemplary embodiment, the air is channeled through wing ducts628and630to facilitate cooling wing202. The air is then discharged from wing202through outlets (not shown) at the ends of wing ducts628and630. Similarly, exhaust gases614may be channeled into second exhaust duct618, and air (not shown) from an engine fan (not shown) may be channeled into a second fan exhaust duct (not shown). The air from the second fan exhaust duct is discharged into second plenum648to facilitate providing fluid to wing ducts650and652at a lower temperature than exhaust gases614. In an exemplary embodiment, the air is channeled through wing ducts650and652to facilitate cooling wing202. The air is then discharged from wing202through outlets (not shown) at the end of wing ducts650and652.

In the exemplary embodiment, first duct616is coupled in flow communication to a first cruise duct622. In the exemplary embodiment, at least a portion of cruise duct622is oriented generally parallel to center line626. In the exemplary embodiment, during pre-defined engine operations, exhaust gases612are discharged from duct616through first cruise duct622. First cruise duct622is coupled in flow communication to a first cruise nozzle642. In the exemplary embodiment, cruise nozzles642and658, described in more detail below, are each variable area nozzles. The design, construction, and control of variable area nozzles are known in the art. Nozzles642and658may utilize clamshell or shutter valve designs as is known in the art. Actuation of nozzles642and658may be hydraulic, electric, or any other method known in the art. Cruise nozzle642is oriented to facilitate enabling exhaust gases612to be discharged through cruise nozzle642to facilitate propelling the aircraft in a direction that is generally parallel to center line626.

In the exemplary embodiment, second exhaust duct618is coupled in flow communication to a second plenum duct644and to a second cruise duct646. Second plenum duct644is coupled in flow communication to a second plenum648. In the exemplary embodiment, at least a portion of plenum648is oriented generally perpendicularly and upward from center line626. In the exemplary embodiment, a portion of first plenum624extends substantially concentrically within a portion of second plenum648. Alternately, a portion of second plenum648extends substantially concentrically within a portion of first plenum624. Moreover, in the exemplary embodiment, second plenum648is configured similarly to second rotor plenum250shown inFIG. 4.

Furthermore, in the exemplary embodiment, second plenum648is coupled in flow communication to a plurality of second wing ducts650and652that extend axially through wing602and are oriented in a substantially non-parallel direction to center line626. In the exemplary embodiment, second plenum648is coupled in flow communication to a starboard second wing duct650and a port second wing duct652. Starboard wing duct650extends from center line626towards wing starboard end636through one portion of wing602. Port wing duct652extends from center line626towards wing port end640through the remaining portion of wing602. Alternately, propulsion system600may include more or less than two second wing ducts650and652. Each of second wing ducts650and652is coupled in flow communication to a second wing outlet654and656, respectively. In the exemplary embodiment, starboard wing outlet654is defined on aft side634of wing602on starboard end636between starboard first wing outlet632and center line626. Similarly, port wing outlet656is defined on aft side634of wing602on port end640a between port first wing outlet638and center line626. Starboard second wing outlet654and port second wing outlet656are oriented to facilities enabling exhaust gases612and614to be discharged through outlets632,638,654and656, respectively, to facilitate reducing drag on the aircraft during pre-defined engine operations. Propulsion system600with wing ducts628,630,650, and652may also facilitate providing other functions, such as, but not limited to, yaw control, wing trailing edge thrust nozzles, or wing cooling.

In the exemplary embodiment, second duct618is coupled in flow communication to a second cruise duct646. In the exemplary embodiment, at least a portion of cruise duct646is oriented generally parallel to center line626and is positioned adjacent to cruise duct622. In the exemplary embodiment, exhaust gases614are channeled from duct618into second cruise duct646. In the exemplary embodiment, second cruise duct646is coupled in flow communication to a second cruise nozzle658. Cruise nozzle658is oriented to facilitate enabling exhaust gases614to be discharged through cruise nozzle658to facilitate propelling the aircraft in a direction generally parallel to center line626during pre-defined engine operations.

When the aircraft is in operation, in the exemplary embodiment, air is channeled through inlets608and610into engines604and606, respectively. From engines604and606, exhaust gases612and614are discharged through exhaust ducts616and618, respectively. A portion of exhaust gases612and614is then channeled through plenum ducts620and644, respectively. The remaining portion of exhaust gases612and614is channeled through cruise ducts622and646, respectively. The portion of exhaust gases612and614channeled into plenum ducts620and644, respectively, is then channeled through plenums624and648, respectively. From plenums624and648, exhaust gases612and614are channeled into wing ducts628,630,650, and652, respectively, to be discharged through wing outlets632,638,654, and656, respectively. When exhaust612and614is discharged through outlets632,638,654, and656drag on the aircraft is facilitated to be reduced. The portion of exhaust gases612and614that is channeled into cruise ducts622and646, respectively, is discharged through cruise nozzles642and658, respectively. Control design and control laws required for actuation of nozzles642and658during pre-defined engine operations are known in the art. Exhaust gases612and614are discharged through cruise nozzles642and658, respectively, to facilitate propelling the aircraft in a direction that is generally parallel to center line626.

The above-described methods and apparatus facilitates simplifying a propulsion system that can be used with a multiple engine assembly. The propulsion system facilitates maintaining independent exhaust circuits for a multiple engine assembly in an aircraft by providing each engine with an exhaust circuit independent from any other engine exhaust circuit. Each engine has an exhaust circuit from the engine to at least two outlets. The propulsion system facilitates isolating one engine from other engines within the assembly. With the engines isolated by the design of the exhaust circuit, isolation valves, actuators, and hydraulic lines are eliminated, facilitating reducing the complexity of the multiple engine installation. If an engine is rendered inoperable, the isolation of each engine facilitates allowing the ability to restart an inoperable engine, and facilitates maintaining control of an aircraft during the inoperability of an engine. The propulsion system facilitates maximizing control at a reduced thrust level since the amount of exhaust is reduced but the distribution fractions are facilitated to be held substantially constant. Control of the aircraft is also facilitated to be increased because, by isolating the exhaust circuits, the exhaust forces stay balanced. The propulsion system also facilitates attempting to restart an inoperable engine without affecting the operation of the other engines in the installation. Pilot operation of an aircraft is facilitated to be simplified because, by using the propulsion system of the current invention, the pilot only needs to attempt restart of an inoperable engine without having to actuate valves.

Exemplary embodiments of a method and apparatus for a multiple engine propulsion system are described above in detail. The method and apparatus is not limited to the specific embodiments described herein, but rather, components of the method and apparatus may be utilized independently and separately from other components described herein. For example, the propulsion system may also be used in combination with other aircraft exhaust gas functions, and is not limited to practice with only the generally horizontal propulsion function, the generally vertical take-off and landing, STOVL, and/or ESTOL functions, and/or the drag reduction function as described herein. Rather, the present invention can be implemented and utilized in connection with many other aircraft propulsion applications.