Abstract: A multi-engine aircraft includes at least two first engines and a third engine located at a rear part of the fuselage, containing rear tail sections, along a vertical longitudinal plane of symmetry of the fuselage. The rear tail sections define a channel which is symmetrical with respect to the longitudinal plane of the fuselage. The third engine is arranged in the plane of symmetry of the channel corresponding to the longitudinal plane and is mounted on the upper part of the fuselage in a raised manner and in front of the tail sections, so that the outlet of the third engine is situated substantially at the inlet of the channel defined by the tail sections.

Abstract: An aircraft fuel cell system (10) includes a fuel cell (12a, 12b, 12c, 12d) which has an oxidant inlet (14a, 14b, 14c, 14d) for supplying an oxygen-containing medium to the fuel cell (12a, 12b, 12c, 12d). An oxidant supply line (16) has a first end which is connected to the oxidant inlet (14a, 14b, 14c, 14d) of the fuel cell (12a, 12b, 12c, 12d). A second end of the oxidant supply line (16) is connectable to a used air outlet (18) of a cabin (20) of the aircraft.

Abstract: Systems and methods for operating aircraft power systems are disclosed. A power system in accordance with one embodiment of the invention includes an aircraft auxiliary power unit and a controller coupled to the aircraft auxiliary power unit, with the controller being configured to automatically stop the auxiliary power unit while the auxiliary power unit is functioning normally. The controller can also be configured to automatically start the auxiliary power unit in-flight when power supplied or expected to be supplied to a subsystem of the aircraft has a non-zero value at or below a threshold value. The controller may also be configured to start the auxiliary power unit when a load or expected load on the subsystem meets or exceeds a threshold value.

Abstract: A filtering device for an engine or a for power unit with a radial air intake, includes a ring-shaped filter for covering the radial air intake, characterised in that the ring-shaped filter includes a first fixed part and a second mobile part which is movable with respect to the first fixed part through actuator elements, from a filtering position in which the whole radial air intake is covered by the ring-shaped filter, to a bypass position in which the second mobile part uncovers at least partly the radial air intake.

Abstract: A supply system that encompasses a vapor generator, may be used to generate water. The vapor generator is supplied with hydrogen and oxygen, and generates hot water vapor, which may be used for supplying energy and water. For example, using the supply system reduces a take off weight for an aircraft and supply redundancy.

Abstract: Drag management structure. The structure includes a tube having an entrance and exit along a longitudinal axis. At least one row of stationary swirl generating vanes is provided at the entrance, the swirl vanes disposed at an angle with respect to the longitudinal axis selected to produce a steady streamwise vortex in a fluid at the tube exit. A fan rotor may be disposed upstream of the stationary vanes.

Abstract: A fuel system for an aircraft is disclosed. The fuel system comprises a fuel tank and a fuel reformer for receiving fuel from the fuel tank. The system includes a hydrogen fuel cell array for receiving hydrogen from the fuel reformer. The system further includes mechanism for providing an inerting gas from the fuel system to the fuel tank.

Abstract: A modular avionics system for an Unmanned Aerial Vehicle (UAV) has a control module that executes flight control and vertical and lateral guidance algorithms to generate control commands. A data link module communicates with a remote control station and receives control commands from the remote control station. A data acquisition module communicates with the control module and the data link module. The data acquisition module is configured to receive and process data from one or more onboard sensors and to actuate a plurality of servo motors in response to control commands. A switching module selectively couples the data acquisition module to the control module or to the data link module responsive to an input from the remote control station to respectively switch between a fully autonomous mode of UAV operation and a manual mode of UAV operation. Power may be provided by a power module.

Abstract: This invention provides an aircraft electric generation system, which can achieve significantly increased capacity of electric generation, while adequately suppressing unwanted increase of a front face area of an aircraft engine as well as successfully dealing with considerably large changes of an engine spool speed. This electric generation system is driven by the engine and includes: a continuously variable transmission (CVT) connected with a rotation shaft of the engine; an electric generator located above the CVT and driven by an output of the CVT; and a lubricating oil pump unit located below the CVT and also driven by the output of the CVT.

Abstract: The disclosure provides for an aircraft galley and lavatory energy system capable of independent operation from a separate aircraft energy generating system. The galley and lavatory energy system comprises an energy source providing electrical energy, heat energy, and at least one by-product; a plurality of galley and lavatory devices for receiving the electrical energy, the heat energy, and the at least one by-product; and, a plurality of connectors for connecting the electrical energy, the heat energy, and the at least one by-product to the galley and lavatory devices. The energy source comprises a fuel cell, a fuel module, and optionally, a supplemental fuel source.

Abstract: A system for electrical generation, conversion, distribution and starting on board an aircraft, of “bleedless” type, that is, with an electrical power architecture with no pneumatic circuits. The electrical distribution channels for high power loads specific to aircraft of “bleedless” type, and the electrical distribution channels for conventional loads, including technical loads, such as avionics, lighting, fuel pumps and commercial loads are separated, and are supplied with power by separate generators driven by the aircraft's engines.

Abstract: A hydraulic drive for an aircraft includes: a gear, a first hydraulic pump and a second hydraulic pump, wherein the gear is installed in a gear housing and wherein the first hydraulic pump and the second hydraulic pump in each case are installed in a pump housing that is affixed to the gear housing, or the two together are installed in a pump housing that is affixed to the gear housing; a hydraulic supply device including a first and a second hydraulic system for operating actuators of the aircraft; and a monitoring and drive device, with the hydraulic supply device including a first hydraulic drive for coupling the latter to a first engine, and a second hydraulic drive for coupling the latter to a second engine, wherein each hydraulic drive includes: a gear drive shaft for coupling the respective hydraulic drive to an engine output shaft of the respective associated engine; two hydraulic pumps that are coupled to a gear output shaft, in each case with a connection device for connecting the hydraulic pump to

Abstract: An un-manned multi-stage payload delivery vehicle and methods of deployment therefore are disclosed. According to various embodiments, the payload delivery vehicle includes first stage and a second stage. At least one of the first and second stages comprises a jet engine. According to various embodiments, methods of deploying the payload delivery vehicle include the steps of launching the payload delivery vehicle from a launch site, controlling the flight of the payload delivery vehicle in accordance with one or more deployment parameters, deploying a payload attached to the payload delivery vehicle, and controlling the flight of the payload delivery vehicle subsequent to payload deployment such that the payload delivery vehicle is flown to a pre-determined location for recovery and reuse.

Abstract: In order to generate an efficient aerodynamic braking force, whatever the speed of a vehicle such as an airplane flying in the air, the method includes a step for the production of energy by the vehicle, a step of storage of the energy produced and a step of utilisation of such energy to drive a propeller which generates a force opposing the forward motion of the vehicle. Energy is produced by using the displacement of the vehicle with respect to air using a propeller driving a generator, or using the displacement with respect to the ground, using wheels driving a generator, or using generators driven by motors of the vehicle. The energy can be stored in the pneumatic, electric or kinetic form and the generation and driving means are selected according to the technology used for the storage means.

Abstract: A non-aircraft-propelling auxiliary gas turbine engine installable in an aircraft having a cabin adapted to be pressurized. The auxiliary gas turbine engine includes an auxiliary-gas-turbine-engine compressor having an inlet, wherein the inlet is adapted to receive pressurized air from the cabin. A method for operating a non-aircraft-propelling auxiliary gas turbine engine of an aircraft includes providing pressurized air from the cabin of the aircraft to an inlet of a compressor of the auxiliary gas turbine engine. The method includes providing compressed air from the compressor to a combustor of the auxiliary gas turbine engine and includes providing combustion gases from the combustor to a turbine of the auxiliary gas turbine engine, wherein the turbine is mechanically coupled to the compressor.

Abstract: A method and apparatus for charging energy supplies in an unmanned aerial vehicle (UAV). The present invention relates to a UAV that comprises an inductive charging device that utilizes the electromagnetic field emanated by overhead/utility power lines, to charge the energy supplies. The UAV also includes a releasable latch for holding power lines to allow for the perching of the UAV on power lines during the charging process. The latch and the inductive charging device may be provided on a single device, a battery augmentation trap (BAT). The UAV may be perched in an upright orientation to allow for takeoff after the charging of energy supplies on the power line.

Abstract: A motor drive for an electric motor receives high frequency AC current, and delivers this current through a converter which is operable to change the current delivered downstream to an inverter and an electric motor.

Abstract: An apparatus for regulating voltage and aerospace electrical power systems are implemented. A multi-functional apparatus for regulating voltage, according to one embodiment, comprises: a DC to DC converter (315), wherein the DC to DC converter (315) is controlled to operate in a first direction to receive a DC voltage from a first bus (329) and to output a first regulated DC voltage adjusted to charge a battery (307), wherein the first bus (329) receives power from a second bus (201), and is controlled to operate in a second direction to receive a battery DC voltage from the battery (307) and to output a second regulated DC voltage to the first bus (329) to power a load (231) independently or in combination with the second bus (201).

Abstract: A method of generating lift for a vehicle including heating a flow of gas using a gas generator mounted on the vehicle that contributes no more than about ten percent of thrust used to propel the vehicle in a forward direction, and driving a lift fan using the heated gas flow to generate lift for the vehicle.

Abstract: A propulsive system for an aircraft including an auxiliary jet engine is integrated within a tail cone of a fuselage. Lateral air intakes include each one a scoop movable between a closed position and an opened position are associated with aerodynamic channels to supply with air the auxiliary jet engine. The aerodynamic channels meet at a common channel including a movable flap to balance air flows coming from the air intakes when the operation is not symmetrical.

Abstract: In order to not risk producing an overpressure of air in the cabin of an airplane on the ground during servicing operation on the airplane, it is appropriate to deliver the air into the cabin of the airplane only when the inlets of the air-conditioning system are open. A device for feeding electricity and air to an airplane on the ground includes means of electric production capable of being connected to at least one electric circuit of the airplane and includes means of producing a flow of air. It has, in addition, a means of determining whether the airplane is actually switched on electrically or is not actually switched on electrically and means for inhibiting the flow of air delivered toward the airplane when the airplane is not actually switched on electrically, that is, as long as it is uncertain whether the inlets of the air-conditioning system are opened.

Abstract: A refueling drogue assembly including a refueling drogue receptacle, a control unit including a duct, and a refueling hose connector adapted to rigidly couple the control unit to an aerial refueling hose. In some embodiments, the control unit is flexibly coupled to the refueling drogue receptacle. In some embodiments, the control unit is adapted to change an orientation of at least a portion of the duct relative to a longitudinal axis of the control unit.

Abstract: In a rear cone of a fuselage of an airplane a pressurized space is arranged in the rear cone and extends up to an impervious strong wall, placed on a rear portion of the length covered by a fin. The pressurized space constitutes an area accessible to individuals and is able to constitute, in particular, a rest and service area for the crew.

Abstract: There is a necessity to provide power for some aircraft service functions whilst the main engines (34) are not operational, for example when the aircraft is on the ground, and to start the main engines (34). This demand is met by provision of auxiliary power units (21). Conventionally a single auxiliary power unit (2) is located in the tail of the aircraft and requires fuel lines and relatively high capacity electrical cabling in order to provide electrical power for main engine starting and service functions. The present invention provides an auxiliary power unit (21) mounted on each main engine (34) and coupled together through an electrical distribution system. This provides greater redundancy in the event of failure of an auxiliary power unit (21) as well as reducing overall weight.

Abstract: Which comprises an auxiliary power unit (1) for supply of pneumatic and electrical power, whose pneumatic power outlet is linked to a duct (2) which conventionally, incorporates bends (7) and compensation elements (6) for thermal expansion and for compensation of the vibrations produced by the APU (1) in its functioning. It is characterized in that the power outlet of the APU (1) is arranged in its front part in which is connected the duct consisting of a straight pipe (2a) inclined downwards toward the lower part of the aircraft in which compensation elements (6) for thermal expansion and for compensation of vibrations are inserted in order to reduce the length of the duct (2) and eliminate the bends, so that the pressure losses are considerably reduced.

Abstract: An Auxiliary Power System includes an APU controller and an aircraft load controller which include an APU load capacity algorithm which provides an uncomplicated and robust method of APU load control. The APU load capacity algorithm defines three load zones: a continuous APU load capacity zone (zone A); a time controlled zone (zone B); and a fault zone (zone C). Each zone is related to altitude to the service ceiling of the APU to provides consistent APU load capacity that addresses APU performance variation and deterioration effects to an end of the APU useful life.

Abstract: The lighter-than-air vehicle for shading is an airborne, movable system that provides sun shade for an open area. The vehicle is a substantially flat flying device having upper and lower surfaces, and which is filled with a lighter-than-air gas or gases, such as helium or hydrogen. The vehicle may be tethered to the ground through control wires, or may be fully autonomous and controlled by propeller fans. The required power may be provided by wire from ground, or through a portable power source, such as solar cells, mounted atop of vehicle. The vehicle has sun sensors that allow it to track the sun, and provides around the clock shaded area underneath its surface. The vehicle can also have pressure sensors and altitude sensors that may trigger an alarm in case of an emergency descent to the ground.

Abstract: A power generation system for an airship includes a solar array and an Earth array for converting solar radiation and albedo radiation, respectively, into electrical energy. The airship also carries a power distribution controller to receive the electrical energy for transfer to a power storage device and/or electrical components carried by the airship. The airship may also receive a man-made radiation source purposefully directed at the Earth array.

Abstract: Dual flow auxiliary power unit (APU) inlets and associated systems and methods are disclosed. An inlet in accordance with one embodiment of the invention includes an entrance aperture and a divider positioned in the inlet and located to separate a first portion of the inlet from a second portion of the inlet. The first portion can be configured to couple to an engine air intake of an APU, and the second portion can be configured to direct air away from the air intake. The divider can be positioned to direct air having a first total pressure level and a first distortion level to the first portion of the inlet, and direct air having a second total pressure level and second distortion level to the second portion of the inlet. The first total pressure level can be approximately the same as or higher than the second total pressure level, or the second distortion level can be approximately the same as or higher than the first distortion level, or both.

Abstract: There is disclosed an electrical system for an aircraft comprising: at least one generator (302); a power control system (304) for distributing power from the generator to electrical subsystems (306, 308) in the aircraft; and an ice protection control system (310) for controlling at least one ice protection device (312, 314, 316), wherein the ice protection control system is connected to said at least one generator.

Abstract: The invention relates to a method of feeding energy to actuators associated with the undercarriages forming the landing gear of an aircraft, the aircraft comprising: a main power supply that operates independently of rotation of wheels carried by the landing gear; and a local power supply comprising one or more local generators, each driven by rotation of a wheel carried by an undercarriage; the method of the invention comprising the following steps: in a nominal mode of operation, powering said actuators by the local power supply; and in an additional mode of operation, when the delivery of energy by the local power supply is not sufficient, providing additional energy or all of the energy required by said actuators by means of the main power supply.

Abstract: An auxiliary power unit (APU) compartment air inlet system seals, via one or more inlet doors driven by a single actuator, an APU compartment, and isolates the APU inlet and cooling system inlets from each other. The system includes either one or two inlet doors, depending on the number of ram air inlets formed in the APU compartment. In either instance, however, a single actuator is used to move the inlet door(s) between open and closed positions.

Abstract: A wing load alleviation structure for use on an aircraft, comprising a front spar, wherein the front spar includes a plurality of alternating rigid spar structures and inflatable spar structures; and a rear spar, wherein the rear spar includes a plurality of alternating rigid spar structures and pivot joints, such that when a load is applied to the front and rear spars, deflection of each of the front and rear spars continues at a first rate until a critical load is reached, and then as the loading increases, deflection of each of the front and rear spars continues at a second rate.

Abstract: A method and apparatus is disclosed in which an aircraft landing system is at least partly primarily powered by power provided by a ram air turbine (RAT).

Abstract: Systems and methods for controlling aircraft electrical power are disclosed. A system in accordance with one embodiment includes an electric motor, an aircraft load coupled to the electric motor and powered by the electric motor, and a motor controller coupled to the electric motor to vary an output of the electric motor. The motor controller is changeable among a fixed number of preset controller modes, with individual controller modes corresponding to an operation mode of the aircraft and a non-zero output level of the electric motor. In further embodiments, motor controllers can be substituted for each other, e.g., in the event one motor controller becomes unoperational.

Abstract: A ground support system configured to support servicing of aircraft may include a main body housing one or both of an engine and/or a blower, a control panel that is used to control operation of one or both of the engine and/or blower, and at least one acoustic wave engagement member positioned on the control panel. The acoustic wave member(s) is configured to selectively activate and deactivate an engine or blower function when touched by an operator. The acoustic wave engagement member(s) operates in the presence of moisture and debris.

Abstract: An on board secondary propulsion system for an aircraft provides the capability of taxiing the aircraft on the ground without using the main aircraft engine(s). The power system includes a small driver mounted on the aircraft. In one embodiment of the invention, the driver may be mounted at any desirable location on the aircraft and is designed to provide sufficient thrust to taxi the aircraft. Such a suitable system may be provided as original equipment to an aircraft or retrofitted to existing aircraft. In a further embodiment of the invention, the on board secondary propulsion system, in addition to the taxiing function, may be incorporated with an alternator to provide electrical power, an environmental control unit, and an emergency power unit as desired. The system may also be used to supplement the main aircraft engines as necessary during takeoff and climb to further reduce fuel consumption, noise, engine emissions, maintenance costs and extend the life of the main aircraft engines.

Abstract: The invention relates to an emergency supply unit (1) with a ram-air turbine (2) which can be driven by an air stream (14) and with an energy converter (4) for at least partly maintaining the functioning of a hydraulic system and/or electrical system on board an aircraft in an emergency situation, wherein the energy converter (4) can be driven by means of the ram-air turbine (2) and the emergency supply unit (1) can selectively be brought into a standby mode or into an operating mode. According to the invention, at least the ram-air turbine (2) is surrounded substantially concentrically by a casing (5) forming a flow channel (6) and the energy converter (4) is directly coupled to the ram-air turbine (2) via a drive shaft (3) and the air stream (14) can be delivered to the ram-air turbine (2) through at least one air inlet (9, 17, 18), wherein the spatial position of the ram-air turbine (2) remains substantially unchanged when changing between the standby mode and the operating mode.

Abstract: An inlet door assembly and method for reducing noise from an auxiliary power unit (APU) contained within an aircraft housing is provided. The inlet assembly includes an inlet duct, an actuator, and a door. The inlet duct is configured to extend from the auxiliary power unit to the aircraft housing and has a sidewall that defines a flow passage through which APU noise propagates. The actuator is disposed at least partially within the inlet duct. The door coupled to the actuator. The actuator is also configured to selectively rotate the door between at least a first position, in which at least a portion of the door deflects APU noise in a first direction, and a second position, in which at least a portion of the door deflects the APU noise in a second direction.

Abstract: An arrangement and a method are proposed for the generation of water on board an aircraft with the use of one or more fuel cells, whereby low-temperature fuel cells are provided as fuel cells. It is proposed that several single-cell or few-cell fuel cells may form a fuel-cell panel or cell array and several cell panels or cell arrays may be arranged close to the inside of the aircraft fuselage and the cathode side of the at least one fuel cell has a chamber pointing to the exterior of the aircraft for the condensation of the water contained in the air and the anode side has a chamber carrying a combustion gas, for example hydrogen. With the proposed solution, a reduction in the storage capacity for drinking water and its quality-assured provision may be enabled and moreover, with the use of fuel cells as a virtual power station, the energy demand on engine generators, auxiliary power unit (APU) or ram air turbine (RAT) may be reduced.

Abstract: Systems and methods are provided for reducing pressure loss of air flowing from a first area in a first direction to a second area in a second direction. The systems include a flow surface, first and second fence walls, an opening, and a flow path. The flow surface defines a portion of the first area. The fence walls extend substantially parallel to each other along the flow surface in the first direction. The opening is formed in the flow surface and is disposed between the first and second fence walls. The flow path defines at least a portion of the second area and is in flow communication with the opening to receive a portion of the airflow and to direct the airflow in the second direction. Methods of using and manufacturing the systems are also provided.

Abstract: An improved method and system for facilitating no-break power transfer between an APU and a main engine includes determining a required APU speed for conducting power transfer based on various APU operating parameters, such as engine speed, fuel, environmental temperature, etc. The APU controller then adjusts the APU speed up or down to the required APU speed. Communication between an aircraft computer and the APU controller may also be provided so that operational data can be exchanged to adjust the electrical load of the aircraft below a maximum load threshold set by the APU, avoiding overloading of the APU during power transfer. By exchanging operational data between the APU controller and the aircraft computer, both the APU and the electrical load can be adjusted to optimize no-break power transfer despite varying APU operating conditions and main engine generator frequencies.

Abstract: A rechargeable battery energized unmanned aerial vehicle having surveillance capability and an ability to clandestinely collect propulsion and other energy needs from a conveniently located and possibly enemy owned energy transmission line. Energy collection is by way of a parked vehicle engagement with the transmission line in a current flow dependent, magnetic field determined, rather than shunt, voltage dependent, conductor coupling. Surveillance during both a parked or docked condition and during aerial vehicle movement is contemplated.

Abstract: A gearbox for an auxiliary power unit (APU) includes a front side defining a generator interface configured to be coupled to a generator, the front side further defining an oil pump and fuel control component interface configured to be coupled to an oil pump and fuel control component, and a starter interface configured to be coupled to a starter. The gearbox further includes a back side on an opposite side to the front side and configured to house a gear train; a bottom side defining an oil tank interface configured to be coupled to an oil tank; and a debris conduit extending from the generator interface to the oil tank interface.

Abstract: Combined aircraft hybrid fuel cell auxiliary power unit and environmental control system and methods are disclosed. In one embodiment, an auxiliary power unit includes a fuel cell component which chemically converts combustible fuel into electrical energy. Unutilized fuel emitted by the fuel cell component is combusted by a burner to generate heated gas. The heated gas is received by and drives a turbine, which in turn drives a drive shaft. A compressor, coupled to the drive shaft, compresses a source of oxidizing gas for supplying compressed oxidizing gas to the fuel cell component and to an environmental control system. A heat exchanger controls the temperature of the pressurized air leaving the environmental control system to provide the cabin air supply. Finally, a generator is coupled to the drive shaft to be driven by the turbines to generate additional electrical energy.

Abstract: A passive cooling system for an auxiliary power unit (APU) installation on an aircraft is provided. The system is for an auxiliary power unit having at least a compressor portion of a gas turbine engine and an oil cooler contained separately within a nacelle. The system includes the auxiliary power unit housed within the nacelle of the aircraft, an engine exhaust opening defined in the aft portion of the nacelle and communicating with the gas turbine engine, at least a first air inlet duct communicating with a second opening defined in said nacelle and with said compressor portion and the oil cooler is located within a second duct communicating with an opening other than the engine exhaust opening of said nacelle and with the engine exhaust opening. Exterior cooling air and engine exhaust ejected through said engine exhaust opening entrain cooling air through said second duct to said oil cooler, and thus provide engine oil cooling. An exhaust eductor is also provided.

Abstract: Systems and methods for operating aircraft power systems are disclosed. A power system in accordance with one embodiment of the invention includes an aircraft auxiliary power unit and a controller coupled to the aircraft auxiliary power unit, with the controller being configured to automatically stop the auxiliary power unit while the auxiliary power unit is functioning normally. The controller can also be configured to automatically start the auxiliary power unit in-flight when power supplied or expected to be supplied to a subsystem of the aircraft has a non-zero value at or below a threshold value. The controller may also be configured to start the auxiliary power unit when a load or expected load on the subsystem meets or exceeds a threshold value.

Abstract: Thermally compliant auxiliary power unit (APU) ducts arrangements, and associated systems and methods are disclosed. A system in accordance with one embodiment includes an auxiliary power unit exhaust, that in turn includes an exhaust flow conduit, a housing disposed outwardly from the conduit, a support providing a load path between the conduit and the housing, and a baffle positioned along the flow conduit. At least one of the support and the baffle can have a resilient, radially compressible portion between the flow conduit and the housing.

Abstract: Dual flow auxiliary power unit (APU) inlets and associated systems and methods are disclosed. An inlet in accordance with one embodiment of the invention includes an entrance aperture and a divider positioned in the inlet and located to separate a first portion of the inlet from a second portion of the inlet. The first portion can be configured to couple to an engine air intake of an APU, and the second portion can be configured to direct air away from the air intake. The divider can be positioned to direct air having a first total pressure level and a first distortion level to the first portion of the inlet, and direct air having a second total pressure level and second distortion level to the second portion of the inlet. The first total pressure level can be approximately the same as or higher than the second total pressure level, or the second distortion level can be approximately the same as or higher than the first distortion level, or both.

Abstract: An improved passive cooling system for an aircraft APU compartment that includes a lightweight annular air-cooled oil cooler that is strategically oriented and shrouded to face its annular inlet away axially downstream from the exhaust of the APU to make it inherently fireproof to flames from the APU or any location within the APU compartment that fuel can accumulate.