Abstract: In accordance with at least one aspect of this disclosure, there is provided a system for aircraft power. The system includes a DC/DC converter having a DC input and a DC output and a switching circuit connecting the DC input to the DC output operable to vary voltage at the DC output. A control module is operatively connected to the switching circuit for variable control of the DC output. The control module includes machine readable instructions to cause the control module to receive input indicative of altitude and control the switching circuit to vary voltage of the DC output as a function of environmental conditions such as altitude and humidity. In embodiments the altitude sensor is operatively connected to the controller.

Abstract: A VTOL aircraft includes a plurality of lift propellers configured to rotated by lift motors to provide vertical thrust during takeoff, landing and hovering operations. The lift propellers are configured to generate a cooling airflow to cool the lift motors during use. During a cruise operation when the VTOL aircraft is in forward motion, the lift propellers may be stowed in a stationary position. Therefore, the cooling airflow may be reduced or eliminated when it is not needed.

Abstract: An unmanned aerial vehicle including a propeller blade and a central hub. The propeller blade includes a hole, and a connector located at a root of the propeller blade, the connector including a projection and a shoulder. The central hub includes an opening configured to receive the projection; a portion of a face, wherein the shoulder engages with the portion of the face in a first rotational position of the propeller blade and holes. The holes of the propeller blade and the central hub are concentric so that the propeller blade is movably connected to the central hub via the holes.

Abstract: An aerial vehicle is disclosed having a hybrid drive unit and a rotor unit wherein the hybrid drive unit includes at least a combustion engine, a generator and a first electric motor and the rotor unit includes a first rotor. The combustion engine is configured to drive the generator to produce electricity, and the generator is coupled to the first electric motor in such a way that the first electric motor is feedable with electricity from the generator. The rotor unit includes a second rotor and the hybrid drive unit includes a second electric motor, wherein the generator is coupled to the second electric motor in such a way that the second electric motor is feedable with electricity from the generator. The first rotor is driven by the first electric motor and the second rotor is driven by the second electric motor.

Abstract: A multi-mode aircraft power-split-transmission system includes a rotational power input and a power-split transmission. The power-split transmission includes a sun gear, a planetary carrier, a ring gear, a first rotational power output, and a second rotational power output. The multi-mode aircraft power-split-transmission system also includes a first resistance device coupled to the first rotational power output and fixed to an airframe of the multi-mode aircraft and a second resistance device coupled to the second rotational power output and fixed to the airframe. Operation of the first resistance device causes power received from the rotational power input to be directed to the second rotational power output.

Abstract: A compressed gas ejection assembly for a rotating wing aircraft blade comprising a compressed gas passage adapted to allow a substantially constant mass flow through the compressed gas ejection assembly across at least a portion of the width of the compressed gas ejection assembly.

Abstract: Provided is a technology to properly display information onto a projection surface without depending on a distance image sensor, and directly project a wide range of information other than a survey setting point onto a construction site. A system includes: a projector including an inclination sensor and at least one reflector; a measuring device configured to measure a position of the reflector; a means having surface information; and a means configured for setting a distance between a projection surface onto which the surface information is projected and the measuring device in a normal direction, wherein the measuring device measures the reflector, and the surface information adjusted according to the distance in the normal direction is projected onto the projection surface.

Abstract: An unmanned aircraft includes: a sensor (person detection sensor) and so forth) that performs sensing of an external environment of the unmanned aircraft; a detector (suspicious person identifier) that detects a moving object based on a result of the sensing performed by the sensor; an obtainer (movement prohibition position determiner) that obtains area information indicating an area, entry to which by the moving object is undesirable; and a flight controller that causes the unmanned aircraft to move to a position between the moving object and the area indicated by the area information, based on a positional relation between the moving object and the area, and fly at the position that is a destination position.

Abstract: An anti-aircraft system is described and includes an unmanned aerial vehicle (UAV) comprising a body; a wing connected to the body; and propulsion systems associated with the wing, wherein the propulsion systems comprise pylons releasably connected to opposite ends of the wing such that the propulsion systems may be selectively released from the wing during flight of the UAV.

Abstract: Methods and systems of operating a gas turbine engine in a low-power condition are provided. In one embodiment, the method includes supplying fuel to the combustor by supplying fuel to the first fuel manifold via a first flow divider valve and supplying fuel to the second fuel manifold via a second flow divider valve. While supplying fuel to the combustor by supplying fuel to the first fuel manifold, the method includes stopping supplying fuel to the second fuel manifold and supplying pressurized gas to the second fuel manifold via the second flow divider valve to flush fuel in the second fuel manifold into the combustor and hinder coking in the second fuel manifold and associated nozzles.

Abstract: An aircraft for generating torque. The aircraft includes a motor coupling a lifting rotor and a torque rotor, and is configured to spin the lifting rotor in a first direction to generate lift and spin the torque rotor in a second direction to generate drag-torque. The torque rotor and the lifting rotor are coupled or decoupled from one another during flight or on ground.

Abstract: An exemplary aircraft includes a wing positioned below a vertical rotor, the wing extending to an outboard end, and an anhedral winglet extending from the outboard end through an angular transition to a tip, the anhedral winglet having an external surface exposed to the rotor downwash and the external surface is contoured to generate local wing lift in response to the rotor downwash.

Abstract: A self-retaining wear-pad leveler has a first plate having arms on opposing sides and forming an aperture through the first plate. A rear section is coupled to a rear portion of the first plate and has tabs extending from opposing sides of the rear section. The arms are configured for being retained about a ball of a spherical bearing assembly, and the tabs are configured to cause rotation of the leveler about the bearing when engaged by a component coupled to and rotating about the bearing.

Abstract: The present disclosure discloses a trans-media unmanned aerial vehicle device and a control method thereof. The trans-media unmanned aerial vehicle device includes a housing, and a piston which is arranged in the housing and is capable of moving in a reciprocating manner in the housing; one end of the housing is provided with an opening; several flying wings are uniformly arranged in a circumferential direction of the piston; the flying wings are rotatably connected to a side of the piston facing the opening and are spread or retracted like an umbrella; and under the pushing of the piston, the flying wings can be spread to the outside of the housing and retracted back into the housing.

Abstract: An aircraft with a fuselage that accommodates a floor panel and a fuel storage system, wherein the fuel storage system comprises a tank system with at least one main tank 5a that is arranged underneath the floor panel; a cross ventilation system with a plurality of ventilation lines for venting the tank system, wherein the plurality of ventilation lines comprises at least one crossing ventilation line 11a that is routed from a first lateral side of the tank system to an opposite second lateral side of the tank system; and wherein the at least one crossing ventilation line is routed underneath or in the floor panel from the first lateral side of the tank system to the second lateral side of the tank system.

Abstract: A tail boom support stand assembly for a tail boom of a helicopter includes a forward structure including a forward telescopic support assembly; a webbing arrangement mounted between a first and second boom support of the forward telescopic support assembly to provide a non-rigid cradle for the tail boom; an aft structure comprising an aft telescopic support assembly; a boom support channel of the aft telescopic support assembly to provide a rigid cradle for the tail boom; and a frame structure that interconnects the forward structure and the aft structure.

Abstract: A pitch angle blocking device for blocking the pitch angle of a multi-blade rotor that has neighboring first and second rotor blades in circumferential direction that extend from a rotor hub of a rotary-wing aircraft In non-operational mode of the rotary-wing aircraft. The present embodiments further relate to a multi-blade rotor of a rotary-wing aircraft that is adapted to receiving such a pitch angle blocking device, and to a rotary-wing aircraft with such a multi-blade rotor. The pitch angle blocking device comprises first and second attachment means that are configured to be non-rotatably and releasably attached to the first and second rotor blades spaced apart from the rotor hub, and a connecting device that non-rotatably connects the first attachment means with the second attachment means.

Abstract: An active vibration control system (AVCS) and method for reducing motion and/or vibration of a seat frame within an aircraft includes vibration sensors, a controller, and force generators. In some embodiments, the vibration sensors and/or the force generators are attached to the seat frames. In other embodiments, the vibration sensors and/or the force generators are attached to aircraft structures, proximate to the seat frame. By monitoring the motion and/or vibration of the seat frame, the controller calculates a cancelling force to be generated by the force generators to reduce the vibration experienced by the seat frame and its occupant. Such seat frame vibration control can be implemented as a separate AVCS in an aircraft, or can be integrated in an existing AVCS that is also configured to provide vibration control in other parts thereof.

Abstract: A method for converting a conventional airplane having at least one thermic reaction propulsion engine and at least one fuel tank fluidly connected through fuel pipes to an electric propulsion airplane comprises: removing the at least one thermic reaction propulsion engine from the conventional airplane; replacing the at least one thermic reaction propulsion engine used for propelling the conventional airplane with at least one electric engine; removing the at least one fuel tank from the conventional airplane; implanting at least one rechargeable battery instead of the at least one fuel tank; and electrically connecting the at least one electric engine and the at least one rechargeable battery.

Abstract: A rotor for an aircraft is described having: a support angularly fixed with respect to an axis and housing a power source; a unit rotatable about axis and housing an electrical load of the resistive type; and a power supply system for the electrical load (21, 24) and comprising: a first transformer electrically interposed between the power source and the load; the first transformer comprises: a first winding arranged on the support and a second winding arranged on the unit, a stator carried by the support, rotationally fixed with respect to axis and to which the first winding is fixed; and a rotor operatively connected to the unit and to which the second winding is fixed; the power supply system comprises a capacitive circuit electrically connected to the first transformer, so as to reduce the reactive power absorbed by the rotary transformer.

Abstract: A drone with extendable and rotatable wings and a multiple accessory securing panel is provided. The extendable wings help increase the lift of the drone and reduce the air drag on the drone. The multiple accessory securing panel allows various tools and objects to be temporarily and selectively secured to the drone. The multiple accessories may be secured to the drone by a ground based rotating delivery unit. The drone may have a removable front nose and legs which receive power from a power unit.

Abstract: An electrically-powered VTOL aircraft has a fuselage with a cabin flexibly connected to a powerplane assembly that includes a plurality of electrically-powered rotors and booms. The powerplane assembly can pitch and roll relative to and independently of the cabin, thereby generating efficient fore, aft and lateral thrust while the cabin attitude remains unchanged. This provides a stable passenger experience and enhanced performance and controllability with reduced cost and complexity. In some embodiments, the fuselage is vertically elongated and the powerplane assembly mounts above the fuselage such that a person may walk beneath the rotors completely erect without the fear of being struck by any of the rotors. Using a vertically elongated cabin in conjunction with a relatively high powerplane provides various performance benefits that improve controllability and maneuverability particularly in congested environments, reduce complexity and costs, and enhance passenger safety and experience.

Abstract: Described herein are methods and systems for motorized control of a tether, such as for purposes of user interaction and feedback. In particular, a UAV's control system may determine one or more operational parameters of a motor for a winch disposed in the UAV, the winch including the tether and a spool. The control system may then detect in the one or more operational parameters, an operational pattern of the motor that is indicative of an intentional user-interaction with the tether. Based on the detected operational pattern of the motor that is indicative of the intentional user-interaction with the tether, the control system may determine a motor response process. Then, the control system may operate the motor in accordance with the determined motor response process.

Abstract: An electric vehicle charging connector, including a set of pins, a sensor, and a controller. The set of pins may include a DC pin, wherein the DC pin is configured to supply DC power to a charging port, wherein the charging port comprises a locking mechanism. The sensor can detect power flow from the pins to the charging port. The controller is communicatively connected to the sensor and configured to receive a signal from the sensor and send a locking signal to a locking mechanism. The locking mechanism comprises an engaged state wherein the charging connector is mechanically coupled to the charging port and a disengaged state wherein the charging connector is mechanically uncoupled form the charging port, wherein the locking mechanism is configured to receive a locking signal from the controller of the charging connector and enter the engaged state.

Abstract: A helicopter includes annular rotors surrounding a fuselage. Rotor blades extend radially outwardly from each annular rotor. One or more motors is provided. Each motor rotates a roller, which drives each annular rotor by traction. In an embodiment with two rotors, one rotor rotates in one direction and the other rotor rotates in the opposite direction. A swash device with a grooved outer cylindrical surface engages the free end of a crank arm of each rotor blade to provide collective and cyclic pitch control. Actuators, which may be electromechanical or hydraulic, control positioning and movement of the swash device. Batteries, an electric generator and/or a hydrogen fuel cell may supply electric power.

Abstract: An isolation system and method are disclosed. The isolation system includes a beam that includes a first end and a second end. The isolation system may include at least one clamping block comprising first elastomeric material, and the first end may be coupled with the first elastomeric material by the at least one clamping block. An end condition of the buckling beam may be varied based on compression stiffening of the first elastomeric material.

Abstract: An automatic aircraft powerplant control system includes a throttle servo for adjusting a throttle valve via a throttle control linkage. A throttle control lever provides a user input to the throttle servo, and a throttle controller controls the throttle servo for controlling a throttle valve. A propeller servo may be provided for adjusting a propeller governor setting of an engine. A propeller control lever provides a user input to the propeller servo, and a propeller controller controls the propeller servo. A full-authority digital engine control (FADEC) controller is used to automatically control mixing of fuel and air via a fuel-air mixture device. The FADEC controller may be used to automatically provide propeller control.

Abstract: A rotor wing aircraft provided with a propulsion apparatus is disclosed. The aircraft has a rotating mast configured to rotate said rotor wing and the apparatus includes a pole mechanically connectable to the rotating mast of the aircraft. At one of the ends of the pole there is placed an electric turbine, powered by a battery, and configured to rotate the pole around an axis of the rotating mast in such a way that the rotation of the pole can be used to rotate the rotor wing. Preferably the pole is made of carbon fiber.

Abstract: A rotorcraft provided with a yaw motion control system comprising a fairing and a rotor provided with blades, the blades being arranged in the fairing and able to rotate about an axis of rotation of the rotor, the fairing comprising a casing defining an air stream, the air stream extending in a direction of flow of the air within the fairing from an intake section towards an outlet section. The rotorcraft comprises an ice protection system comprising at least one grille arranged upstream of the air stream in the air flow direction, the grille facing the intake section parallel to the axis of rotation and the casing, no grille facing at least one unprotected section of the intake section in a direction parallel to the axis of rotation.

Abstract: A method and apparatus for estimating an airspeed of a rotorcraft by analyzing its rotor. The rotorcraft includes a fuselage and a main rotor that is equipped with a plurality of blades and that rotates about an axis of a hub of the rotor, and in which the free end or “tip” of each blade describes a path in the vicinity of a tip-path plane. The method makes it possible to determine said airspeed of the rotorcraft in a frame of reference united with the tip-path plane by solving a model of the rotor that puts a pitch angle of at least one blade relative to the tip-path plane into relation with the airspeed of the rotorcraft and with an auxiliary speed. The auxiliary speed may be an induced velocity of the air flowing through the rotor or else an axial airspeed at the upstream infinity of the rotorcraft.

Abstract: A vibration damping device equipped with a resonator mechanism comprising at least one resonator, the at least one resonator having a first beater extending from an embedded end to a free beating end. The resonator consists of an elastically deformable base equipped with a first branch and a second branch connected by a central section, the embedded end being embedded at the first branch, the first branch extending from a first end to a second end each rigidly fastened to a mount, the second branch extending from a first end section to a second end section each rigidly fastened to a vibration source.

Abstract: A battery-powered pilotless aerial vehicle has a center unit, a plurality of rotor units coupled to the center unit, a plurality of battery assemblies, and a plurality of electrical circuitry components including a central control circuitry and at least a flight control subsystem, a detecting and avoiding subsystem, and an emergency communication subsystem controlled by the central control circuitry. The center unit receives one or more of the electrical circuitry components and has a compartment for accommodating one or more passengers or cargo goods. Each rotor unit comprises a propelling module functionally coupled to the central control circuitry. The one or more battery assemblies are configured for being controlled by the flight control subsystem for at least powering the propelling modules, and are at a distance away from the center unit for reducing electromagnetic interference to the electrical circuitry components therein.

Abstract: A rotor system for an aircraft is described and includes an open rotor assembly comprising a plurality of rotor blades connected to a rotor mast; and a drive system for providing rotational energy to the open rotor assembly via the rotor mast. The drive system includes at least one electric motor for providing rotational energy to a motor shaft; and a gearbox connected to the drive shaft for receiving rotational energy from the at least one electric motor via the motor shaft and providing rotational energy to the rotor mast via a rotor shaft.

Abstract: A rotor for an aircraft is described that has a mast, an attenuating device to attenuate the transmission of vibrations from the mast in a plane orthogonal to the first axis; and a transmission device interposed between the mast and the attenuating device; the attenuating device comprises a first and a second mass unit with a first and a second mass rotatable about the first axis with a first and a second rotational speed, two control units operable to cause an additional rotation of at least one of the first and second masses; and a first and a second support assembly carrying the first and second masses; each control unit controls the angle between the first and second masses and each control unit comprises: a belt coupled to the support assembly and a drive unit coupled to the first belt, to cause the rotation of the first support assembly with respect to said transmission device.

Abstract: The present invention relates to an aerially distributable communications device (ACCD) including one or more gyrochutes and communications module configured for wireless communication with external communication nodes. The communications module can be configured for mesh network type communication with similar aerially distributable communications device, or as a gateway type communications device to a wide area network such as a satellite network. The ACCD is for deployment in remote areas and/or areas where normal communications networks are down, such as disaster areas. The ACCD can be deployed from an aircraft or a spacecraft. The ACCD can further be configured with emergency equipment such as water purification equipment, power charging equipment, or the like.

Abstract: A low-cost rocket includes an atmospheric flight part and an exo-atmospheric flight part, and uses the atmospheric air part to ascend into the atmosphere through the use of propellers for the atmospheric portion of the flight. The atmospheric flight part separates from the exo-atmospheric flight part in the vicinity of the exo-atmosphere and the exo-atmospheric rocket is launched thereupon. The atmospheric flight part descends through the atmosphere using autorotation of the propellers and, if necessary, a soft landing can be affected by controlling the pitch of the propellers just prior to landing.

Abstract: The present application discloses a three-steering gear direct-drive coaxial rotor system and a control strategy, and belongs to the technical field of helicopter structures. The system includes an upper rotor power module, an upper rotor assembly, an upper tilting mechanism, a driving steering gear group assembly, a lower tilting mechanism, a lower rotor assembly, a lower rotor power module, an upper fixing mast, and a lower fixing mast. According to the present application, three steering gears directly drives an upper-layer swashplate and a lower-layer swashplate, to make cyclic pitch and add-subtract collective pitch on rotors. The synchronous tilting mechanism of the present application provides a flexible design solution for the characteristic of cyclic pitch phase angle offset of the rotors gear.

Abstract: A rotor for an aircraft is described that has a mast, an attenuating device to attenuate the transmission of vibrations from the mast in a plane orthogonal to the first axis, and a transmission device interposed between the mast and the attenuating device; the attenuating device comprises a first and a second mass unit with a first and a second mass rotatable about the first axis with a first and a second rotational speed, two control units operable to cause an additional rotation of at least one of the first and second masses, and a first and a second support assembly carrying the first and second masses; each control unit controls the angle between the first and second masses and comprises a set of drive gear teeth integral with the first support assembly, a cogwheel with a set of control gear teeth meshing with the drive gear teeth, and an actuator to cause the rotation of the cogwheel about a second axis and of the first mass about said first axis.

Abstract: A multi-engine aircraft includes a first engine drivingly engaged to a common rotatable load and a second engine drivingly engaged to the common rotatable load, the second engine having a bleed air system and a control system in communication with a compressed air switching system. The control system controls operation of the second engine and/or the compressed air switching system. The compressed air switching system includes a switching valve that is displaceable between at least a first position and a second position, the first position interconnecting a lower pressure inlet and a switch outlet, and the second position interconnecting a high pressure inlet and the switch outlet. The switch outlet is in communication with the bleed air system of the second engine. The control system actuates the switching valve to switch between the first and second positions.

Abstract: A technique is introduced for touchdown detection during autonomous landing by an aerial vehicle. In some embodiments, the introduced technique includes processing perception inputs with a dynamics model of the aerial vehicle to estimate the external forces and/or torques acting on the aerial vehicle. The estimated external forces and/or torques are continually monitored while the aerial vehicle is landing to determine when the aerial vehicle is sufficiently supported by a landing surface. In some embodiments, semantic information associated with objects in the environment is utilized to configure parameters associated with the touchdown detection process.

Abstract: A propulsion system for providing propulsion of an aircraft includes a plurality of electric motors coupled with a rotor of the aircraft to drive the rotor and a propulsion motor control. The propulsion motor control includes at least one processor electrically connected with at least one electric motor to actuate the at least one electric motor and at least one battery electrically connected with the at least one processor and at least one electric motor to provide power to the at least one processor and the at least one electric motor. The propulsion motor control actuates the plurality of electric motors based on a desired torque level to drive the rotor to provide propulsion of the aircraft.

Abstract: The present invention includes an a plurality of first variable speed motors mounted on a tail boom of the helicopter; one or more fixed pitch blades attached to each of the plurality of first variable speed motors; and wherein a speed of one or more of the plurality of first variable speed motors is varied to provide an anti-torque thrust.

Abstract: An unmanned aerial vehicle (UAV) for transporting items between locations includes a frame and a propulsion system coupled to the frame, the propulsion system including at least one transmission and at least one motor. The UAV also includes a load support area of the frame, the load support area comprising at least one of a different material than the frame or structural supports.

Abstract: A rotary wing vehicle includes a body structure having an elongated tubular backbone or core, and a counter-rotating coaxial rotor system having rotors with each rotor having a separate motor to drive the rotors about a common rotor axis of rotation. The rotor system is used to move the rotary wing vehicle in directional flight.

Abstract: An isolation system and method are disclosed. The isolation system includes a beam that includes a first end and a second end. The isolation system may include at least one clamping block comprising first elastomeric material, and the first end may be coupled with the first elastomeric material by the at least one clamping block. An end condition of the buckling beam may be varied based on compression stiffening of the first elastomeric material.

Abstract: A load balancing system for a system of rotating elements such as a helicopter rotor or an airplane propeller. The load balancing system includes two or more balancing tubes rotationally attached to blades or props on the system of rotating elements. The balancing tubes are slightly curved and enclose a hollow space containing a quantity of weighted fluid such as mercury. During operation of the system of rotating elements, the weighted fluid disperses throughout the hollow space in the balancing tubes so as to counter any imbalance in the system of rotating elements. Centrifugal forces will cause different dispersal of the weighted fluid throughout the hollow space depending on the overall pulling or pushing forces resulting from any imbalance.

Abstract: A tilting system for a propeller of an aerial vehicle, may include a propeller provided in front of the opening portion of the housing and configured to be selectively tilted with respect to the housing; a link assembly provided in the internal space of the housing, a first end portion of which is connected to the housing and a second end portion of which is connected to the propeller, and configured to tilt up or tilt down the propeller as the link assembly is extended from the housing or retracted into the housing; and an actuator coupled to the link assembly and configured to provide power for extension or retraction to the link assembly.

Abstract: A aircraft gas turbine engine and operation method, the engine including: a staged combustion system having pilot and main fuel injectors, and operates in a pilot-only range wherein fuel delivers to pilot fuel injectors, and a pilot-and-main operation range wherein fuel is delivered to at least the main fuel injectors. The engine further includes a fuel delivery regulator to pilot and main fuel injectors, which receives fuel from a first and second source containing fuels each with different characteristics. The staged combustion system switches between pilot-only and pilot-and-main range operation when in steady cruise mode, the mode defining a boundary between first and second engine cruise operation range. The fuel delivery regulator delivers fuel to pilot fuel injectors during at least part of the first engine cruise operation with different fuel characteristics from fuel delivered to one or both pilot and main fuel injectors the second engine cruise operation range.

Abstract: A system for retaining a folded proprotor blade in flight. The system includes a rotary actuator mechanism operable to generate torque via a shaft that rotates about an axis generally parallel to a chordwise direction of the folded proprotor blade, a pair of clamping arms movable in a direction generally parallel to a beamwise direction of the folded proprotor blade, a pair of linkage arms interoperably responsive to the rotary actuator mechanism and coupled between the rotary actuator mechanism and the pair of clamping arms, and a first guide rod extending between the pair of clamping arms in the direction generally parallel to the beamwise direction.

Abstract: An oil cooling system for an aircraft engine, a bypass valve and an associate method of cooling aircraft engine oil are provided. The oil cooling system includes a heat exchanger having an inlet and an outlet. The inlet is in fluid communication with a first oil conduit to receive a first oil flow from the first oil conduit. The heat exchanger facilitates heat transfer from the first oil flow to another fluid. A flow restrictor defining a constriction is operatively disposed to restrict the first oil flow through the heat exchanger. A second oil conduit receives the first oil flow from the heat exchanger. A bypass oil passage provides fluid communication between the first oil conduit and the second oil conduit to allow a second oil flow received from the first oil conduit to flow to the second oil conduit and bypass the heat exchanger.