Abstract: Embodiments of the invention relate to a flight control system for controlling an aircraft during flight. The flight control system may include a primary controller configured to receive an input from a pilot and to output a primary control signal and a primary transmission path connected to the primary controller and configured to relay the primary control signal. The flight control system may also include a backup controller configured to receive the input from the pilot and to output a backup control signal and a backup transmission path connected to the backup controller and configured to relay the backup control signal. Additionally, the flight control system may include an actuator having a remote electronics unit configured to receive the primary control signal and the backup control signal and to determine if the primary control signal is available and valid.

Abstract: Disclosed is a method and device for attenuating lateral effects on an aircraft due to turbulence encountered by the aircraft during flight. The lateral effects are attenuated by applying a roll control order to control a first controllable movable member that acts on aircraft roll and minimizes aircraft roll-wise disturbances due to wind, and a yaw control order that controls a second controllable movable member to act on aircraft yaw. The roll and yaw control orders are calculated based on a sideslip value of the aircraft, while the yaw control order is calculated as a function of the roll control order to compensate for aircraft lateral effects due to turbulence, as well as lateral effects due to application of the roll control order to the first movable member.

Abstract: A method of controlling rotor pitch in a helicopter comprising the steps of: generating at least one blade dynamics signal representing at least one dynamic force acting on at least one of a rotor blade rotating assembly and a helicopter non-rotating assembly, the rotor blade rotating assembly including a plurality of rotor blades and a pitch actuator for each rotor blade; extracting information representing the at least one dynamic force; generating a dynamic force compensation output representing a compensation for at least a portion of the at least one dynamic force; receiving flight control signals directing flight of the helicopter from flight controls of the helicopter; generating from the flight control signals and the dynamic force compensation output a compensated pitch control signal for each blade of the rotor blade rotating assembly, and providing a compensated pitch control signal to compensate for a portion of the at least one dynamic force.

Abstract: A system and method for monitoring vehicle performance including multi-level caching. The system includes a vehicle portion with sensors, a vehicle caching data server, and a wireless transceiver and a monitoring station portion with monitoring workstations, a monitoring caching data server, and a wireless transceiver. The monitoring caching data server receives and aggregates requests for vehicle performance data from the monitoring workstations based on request priority and available bandwidth. The vehicle caching data server stores vehicle performance data from the sensors and selectively transmits a subset of the vehicle performance data to the monitoring caching data server in response to aggregate requests.

Abstract: This invention relates to an intelligence system on board an aircraft that detects an emergency, assesses the situation, and then acts on the situation in a pre-determined manner.

Abstract: A method and device of dynamically reducing the buffeting of an airplane. The method is carried out by detecting a risk of buffeting of the airplane in flight by a monitor. At least one control surface is turned by an actuator arranged at a trailing edge of each wing of the airplane. The control surface is turned, at a predetermined respective rate of turn, into a predetermined respective position to modify lift profile of the wing along a wingspan length to reduce lift in at least one buffeting-generating region of each wing.

Abstract: A method of optimizing the operation of left and right propellers disposed on either side of the fuselage of a rotorcraft including a main rotor. Left and right aerodynamic surfaces include respective left and right flaps suitable for being deflected, yaw stabilization of the rotorcraft being achieved via first and second pitches respectively of the left and right propellers, and the deflection angles of the left and right flaps are adjusted solely during predetermined stages of flight in order to minimize a differential pitch of the left and right propellers so as to optimize the operation of the left and right propellers, the predetermined stages of flight including stages of flight at low speed performed at an indicated air speed (IAS) of the rotorcraft that is below a predetermined threshold, and stages of yaw-stabilized flight at high speed performed at an indicated air speed of the rotorcraft greater than the predetermined threshold.

Abstract: Disclosed is a method and device for attenuating vertical turbulence on an aircraft. The method and device involve calculating, by a calculating unit, based on a determined vertical wind component a first control order to control movement of at least one first controllable movable member that acts on aircraft lift, and a second control order that controls movement of at least one second controllable movable member to act on aircraft pitch. A verification unit verifies that activation conditions evidencing severe turbulence are in effect, the vertical turbulence being attenuated.

Abstract: A device comprises means for computing the air-craft (A) current position, means for determining at least one maximum permitted deviation (E1) around a set position of the flight path of the flight plan according to accuracy and integrity performances of said current position computation and to the restriction of a flight range authorized in a flight corridor (6A, 6B), and a display system (7) for displaying at least one a distance scale (9) on a viewing screen (8), at least one a fixed symbol (10) displaying the current position and two movable pointers (13, 14) displaying the limits of said maximum permitted deviation (E1).

Abstract: A flight control system is configured for controlling the flight of an aircraft through windshear conditions. The system has means for measuring values of selected flight performance states of the aircraft and a control system for operating flight control devices on the aircraft. A windshear detection system located on the aircraft uses at least some of the measured values of the selected flight performance states to calculate a gust average during flight for comparison to pre-determined values in a table for determining whether windshear conditions exist. The control system then operates at least some of the flight control devices in response to an output of the windshear detection system.

Abstract: The effects of IMU gyro and accelerometer bias errors are significantly reduced in accordance with the present teachings by a system or method for commanding an IMU or vehicle through a series of preprogrammed maneuvers. The maneuvers can be designed to minimize the effects of other gyro errors including scale factor errors, nonlinearities, cross coupling/misalignment, and scale factor asymmetries. A sample maneuver is provided which demonstrates performance based on a sequence of roll and yaw maneuvers resulting in zero build up of error at the end of a maneuver cycle period as a result of these errors. Modification of the system involves the addition of control logic to determine the maneuver period, maneuver rate, and vehicle orientation. No additional hardware beyond possible fuel required to perform the maneuver is required.

Abstract: The present invention relates to a device making it possible to turn on a sub-assembly of an electrical item of equipment hosted in a bigger system, which, if turned on unchecked, may impair the operation of the other items of equipment of the system. An embodiment includes three make/break switches in series in the power supply line and a control of the opening or closing of these make/break switches. Two of the make/break switches are controlled by two independent discrete state indicators, to determine whether the power supply of the sub-assembly of the item of equipment may be energized without undue risk to other equipment of the system. The third make/break switch is controlled by a validation command based on the two discretes, actuating the third make/break switch only if the discretes are in the desired state and if a switching of these discretes has been noted.

Abstract: The flight-control device (1) makes it possible, by offsetting part of a flight command according to a particular flight path, to obtain the same control as is obtained with usual flight control, but without flexible excitation that generates discomfort in the aircraft.

Abstract: There is provided a method and apparatus for controlling a toy helicopter in flight. The toy helicopter is powered by a first rotor and a second rotor. A target speed ratio is determined for the speed of the first rotor and the speed of the second rotor. The speed of the rotors is adjusted incrementally until the target ratio is achieved.

Abstract: There is provided a method and apparatus for controlling a toy helicopter in flight. The toy helicopter is powered by a first rotor and a second rotor. A target speed ratio is determined for the speed of the first rotor and the speed of the second rotor.

Abstract: An apparatus comprises a sensor system, a flexible line, and a sensor. The sensor system is capable of detecting skew in at least some of a plurality of control surfaces for a vehicle. The flexible line extends across a number of interfaces for a portion of the plurality of control surfaces. The sensor is connected to the flexible line and is capable of detecting the skew in the portion of the plurality of control surfaces in response to a selected amount of movement of the flexible line.

Abstract: Embodiments of the invention relate to a flight control system for controlling an aircraft in flight having a backup control system integrated into an active control stick. The actuated control stick may include a processing unit that includes independent and separate hardware and/or software dedicated to the primary control system and the backup control system. For the primary control system, the processing unit may receive a sensed primary control stick signal and communicate with a primary processor, which may be configured to generate a primary control signal. For the backup control system, the processing unit may receive a sensed backup control stick signal and generate a backup control signal. The processing unit may also generate tactile signal for use by the actuated control stick to adjust the feel of a pilot's control stick.

Abstract: The invention relates to a device for load limitation in a aircraft high lift system, said system comprising individual segments of landing flap systems and slat flap systems, and a drive unit. The inventive device for load limitation comprises a control unit that is connected to position sensors and is embodied in such a way as to process signals from the position sensors and to generate a signal for limiting the supplied drive power. The invention also relates to a method for load limitation. According to said method, signals from at least two position sensors are measured; at least one reference variable is calculated form the measured signals; each reference variable is compared with a corresponding threshold value pre-determined from a maximum authorized load; and a control signal is generated for limiting the drive power, when at least one of the reference variables reaches or exceeds the threshold value.

Abstract: The device includes a calculation unit to automatically calculate an overall thrust moment of the engines which represents a thrust asymmetry of the engines of a multi-engine aircraft, a determination unit to automatically determine, using this overall moment, a maximum roll rate, and a limiting unit to automatically limit a roll command using this maximum roll rate.

Abstract: Embodiments of the invention relate to a flight control system for controlling an aircraft during flight. The flight control system may include a primary controller configured to receive an input from a pilot and to output a primary control signal and a primary transmission path connected to the primary controller and configured to relay the primary control signal. The flight control system may also include a backup controller configured to receive the input from the pilot and to output a backup control signal and a backup transmission path connected to the backup controller and configured to relay the backup control signal. Additionally, the flight control system may include an actuator having a remote electronics unit configured to receive the primary control signal and the backup control signal and to determine if the primary control signal is available and valid.

Abstract: An aircraft flight surface control system and method simultaneously provides the benefits of both an active/active system architecture and in active/standby system architecture. The system is preferably implemented using hydraulic actuator assemblies and electromechanical actuator assemblies coupled to the same flight control surface. During normal system operations the electromechanical actuator assemblies are energized to supply a relatively minimal force to associated flight control surfaces. In effect, the electromechanical actuators, although energized, may be pulled along by the associated hydraulic actuator assemblies, until needed. Thus, the electromechanical actuator assemblies are controlled in a manner that closely resembles the active/standby architecture.

Abstract: A method and apparatus for a split detent tactile cueing control system comprising an inceptor, a position sensor, vehicle sensors, and a flight control computer. The inceptor can be moved into different positions measured by a position sensor. The vehicle sensors generate signals in response to detecting parameters about a vehicle during a flight. The flight control computer is coupled to the inceptor and the vehicle sensors. The flight control computer is capable of generating actuation signals used to generate tactile cues to generate a flight path hold detent and an altitude hold detent within the plurality of positions using a force feel profile and the parameters. An extension of a latch force from the flight path hold detent to the altitude hold detent is present during changes in vehicle direction. Series actuator compensation allows increased split detent separation with insignificant command overshoot.

Abstract: A method is disclosed for controlling an aircraft when the hydraulic system of the aircraft has been compromised. The method may include resealing at least one gain vector of a digital fly-by-wire, lower-order, full-state feedback control in at least one axis. The gain(s) may then used by a digital control to modulate engine thrust. In this manner, engine thrust modulation may be used for stabilization and control of control-configured aircraft without requiring a substantial change in piloting technique.

Abstract: A monitoring and control device for an aircraft actuator includes a control module, delivering control signals for the actuator and position signals for the actuator determined according to control messages received from a piloting management system of the aircraft, and at least one first position sensor supplying information concerning the position of the actuator, and a monitoring module, delivering position signals for the actuator and receiving the control signals received from the piloting management system of the aircraft, and information relating to the position of the actuator supplied by at least one second position sensor. The control and monitoring modules are capable of assessing the consistency of the signals processed therein and of controlling accordingly a power supply and disabling module of the actuator.

Abstract: A method for monitoring the integrity of an aircraft position computed on board including on-board means for monitoring the aircraft position that are able to detect common-mode failures. Dissimilar computing channels of the aircraft position are utilized, the dissimilar channels being on-board in the aircraft. Each aircraft position primary computing channel is supplemented by a dissimilar computing channel, which allows the coherence of the primary aircraft position, the position computed by the primary computing channels, to be verified. Mechanisms for verifying the reliability of the results from dissimilar computing channels are implemented to limit a loss of performance from the utilization of dissimilar computing channels, which are less performing than primary computing channels.

Abstract: A flight control system is configured for controlling the flight of an aircraft through windshear conditions. The system has means for measuring values of selected flight performance states of the aircraft and a control system for operating flight control devices on the aircraft. A windshear detection system located on the aircraft uses at least some of the measured values of the selected flight performance states to calculate a gust average during flight for comparison to pre-determined values in a table for determining whether windshear conditions exist. The control system then operates at least some of the flight control devices in response to an output of the windshear detection system.

Abstract: Embodiments of the invention relate to a flight control system for controlling an aircraft during flight. The flight control system may include a primary controller configured to receive an input from a pilot and to output a primary control signal and a primary transmission path connected to the primary controller and configured to relay the primary control signal. The flight control system may also include a backup controller configured to receive the input from the pilot and to output a backup control signal and a backup transmission path connected to the backup controller and configured to relay the backup control signal. Additionally, the flight control system may include an actuator having a remote electronics unit configured to receive the primary control signal and the backup control signal and to determine if the primary control signal is available and valid.

Abstract: Apparatuses and methods for controlling autoflight systems are disclosed herein. An apparatus for use with an aircraft having an autoflight system can include an autoflight performance selector configured to limit the response of the autoflight system to flight guidance instructions in at least two of the pitch, roll and yaw axes. The autoflight performance selector has at least a first selection and a second selection different than the first selection. Selecting the first selection causes the response of the autoflight system to flight guidance instructions to not exceed a first level in the at least two axes, and selecting the second selection causes the response of the autoflight system to the flight guidance instructions to not exceed a second level in the at least two axes different than the first level.

Abstract: An interactive aircraft load management system automates calculation and provides simulation capability to changes in an aircraft C.G. limit for display on a three-dimensional aircraft symbology. The aircraft load management system also communicates with a fly by wire (FBW) flight control system wherein the aircraft's control system is programmed to automatically compensate for C.G. excursions and to alter control laws. The aircraft load management system also selectively reels-in and reels out sling lines as the aircraft pitches and rolls to maintain a load vector from a slung load along the aircraft centerline. Load vector travel is accomplished by coupling a winch control system into the flight control system.

Abstract: Flight control systems have plural control subsystems with redundancies organized so as to provide continued but degraded control power over critical aircraft flight operating parameters even if any one complete control subsystem catastrophically fails. One example described in detail for a VTOL craft includes four groups of controls, each group comprising inputs relating to six degrees of freedom of the vehicle, at least one control computer and a plurality of actuators; each group utilizing 25% of required flight control power for the vehicle.

Abstract: A vortex detection device suitable for use in fighter aircraft including an angle-of-attack sensor, an angle-of-attack processing unit connected to the angle-of-attack sensor capable of forming a signal representative of current air stream's angle-of-attack, a synthetic angle-of-attack estimation unit capable of forming a synthetic angle-of-attack signal, and a vortex level calculation unit connected to the processing and estimation unit, capable of calculating a vortex level signal, and a vortex detection unit connected to the vortex level calculation unit, for deciding, based on the vortex level signal, if a vortex is detected.

Abstract: A flight control system for an aircraft receives a selected value of a first parameter, which is either the airspeed or inertial velocity of the aircraft. A primary feedback loop generates a primary error signal that is proportional to the difference between the selected value and a measured value of the first parameter. A secondary feedback loop generates a secondary error signal that is proportional to the difference between the selected value of the first parameter and a measured value of a second flight parameter, which is the other of the airspeed and inertial velocity. The primary and secondary error signals are summed to produce a velocity error signal, and the velocity error signal and an integrated value of the primary error signal are summed to produce an actuator command signal. The actuator command signal is then used for operating aircraft devices to control the first parameter to minimize the primary error signal.

Abstract: A homeostatic flying hovercraft preferably utilizes at least two pairs of counter-rotating ducted fans to generate lift like a hovercraft and utilizes a homeostatic hover control system to create a flying craft that is easily controlled. The homeostatic hover control system provides true homeostasis of the craft with a true fly-by-wire flight control and control-by-wire system control.

Abstract: A method and a device for providing automatic load alleviation to a high lift surface system, in particular to a landing flap system, of an aircraft when a blockage occurs, wherein in response to a control signal emitted by a control device at least one high lift surface, which is actuated by means of a local mechanical final control element, is brought to a predetermined position by a central drive unit that is connected by way of a rotary shaft arrangement to the local final control element by generating a torque transmitted by the central drive unit to the rotary shaft arrangement. If a signal is registered that indicates that there is a blockage within the high lift surface system, the torque transmitted by the central drive unit to the rotary shaft arrangement is automatically reduced to a predetermined low torque value, and the position of the high lift surface system is fixed.

Abstract: Controlling the pitch of individual rotor blades of a helicopter to reduce control loads, vibration and noise in or from the rotating rotor control elements. The system generates blade dynamics signals representing dynamic forces acting on either or both of the rotating and non-rotating elements of the helicopter, including rotor blades of a rotating assembly. The system extracts information representing at least one dynamic force, generates a dynamic force compensation output that represents a compensation for the dynamic force, and generates, from flight control signals and the dynamic force compensation output, a compensated pitch actuator control signal for each rotor blade wherein the compensation factor of the pitch control signal compensates for the dynamic force.

Abstract: An intra-platform wireless communications system is disclosed. The wireless intra-platform communication system comprises a first wireless transceiver, coupled to a platform processor and a second wireless transceiver, coupled to at least one of the subsystems. Platform operational data is communicated between the platform processor and the at least one subsystem via the first and second wireless transceivers.

Abstract: The present invention relates to helicopter automatic piloting equipment. The automatic piloting device for helicopter acts on flight controls of the helicopter that are affected by mechanical play by means of a group of mechanically irreversible rams termed series rams with fast response and short stroke, placed in series on the flight controls. According to the invention, the device comprises at least one detector for detecting direction of variation of the displacement instructions of the series rams and a play compensator adding to the instruction, as a function of the latter's direction of variation, a corrective term dependent on the mechanical play affecting the flight control equipped with the series ram concerned.

Abstract: The invention relates to a method and device for reducing the wake vortices of an aircraft during the approach/landing phase. Spoilers are automatically ordered to deploy when lift-augmenting aerodynamic surfaces are ordered to deploy, and are automatically ordered to retract when at least one of the following three conditions holds: the angle of incidence ? of the aircraft is equal to or greater than an incidence threshold ?s; the speed Vc of the aircraft is equal to or less than a speed threshold Vs; and the aircraft is instigating a go-around maneuver.

Abstract: A method for controlling a plant assembly includes providing a plant assembly having a first plant including a first sensor that monitors the first plant. The plant assembly further includes a second plant in communication with the first plant. The second plant includes a second sensor that monitors the second plant. The method further includes providing a controller that is adapted to control the plant assembly. An outer control loop of the controller receives a setpoint and a feedback signal, which is provided by the second sensor. A first control output signal is communicated from the outer control loop to an inner control loop of the controller. The inner control loop receives the first control output signal and a feedback signal, which is provided by the first sensor of the first plant. An output signal is provided to the first plant.

Abstract: An aircraft flight control surface actuation control system includes an actuator control unit and a flight control module. The actuator control unit includes at least two independent actuator control channels to generate limited authority flight control surface actuator commands based on pilot inceptor position signals and flight control augmentation data. The flight control module supplies the flight control augmentation data to each of the independent actuator control channels, determines operability of each of the actuator control channels and, based on the determined operability of each independent actuator control channel, selectively prevents one of the independent actuator control channels from supplying the limited authority flight control surface actuator commands. The flight control module may also generate full authority flight control surface actuator commands for supply to flight control surface actuators.

Abstract: The present disclosure relates to an aircraft high lift system with at least one load station for actuating a flap of a wing, preferably a landing flap and/or a leading-edge flap, at least one transmission with transmission portions located between branch transmissions, wherein by means of the branch transmissions actuating energy can be branched off from the transmission to the load station, and to a method for determining an operating condition of an aircraft high lift system.

Abstract: A stall protection system for use with an aircraft may have at least one sensor configured to provide an indication of a pressure differential associated with airflow across an airfoil, and a controller in communication with the at least one sensor. The controller may be configured to compare the pressure differential to a pressure differential threshold associated with a stall condition of the airfoil, and to selectively generate a recovery response signal based on the comparison.

Abstract: A real-time multi-tasking digital control system with rapid recovery capability is disclosed. The control system includes a plurality of computing units comprising a plurality of redundant processing units, with each of the processing units configured to generate one or more redundant control commands. One or more internal monitors are employed for detecting data errors in the control commands. One or more recovery triggers are provided for initiating rapid recovery of a processing unit if data errors are detected. The control system also includes a plurality of actuator control units each in operative communication with the computing units. The actuator control units are configured to initiate a rapid recovery if data errors are detected in one or more of the processing units. A plurality of smart actuators communicates with the actuator control units, and a plurality of redundant sensors communicates with the computing units.

Abstract: A device for detecting synchronous errors of high-lift surfaces such as landing flaps or slats on aircraft, having an optical conductor which is laid over at least two adjacent high-lift surfaces, a light source and an optical receiver which are allocated to different ends of the optical conductor, as well as an evaluation unit for determining a synchronous error of the high-lift surfaces on the basis of the light signal received from the optical receiver.

Abstract: A method and a device for providing automatic load alleviation to a high lift surface system, in particular to a landing flap system, of an aircraft when a blockage occurs, wherein in response to a control signal emitted by a control device at least one high lift surface, which is actuated by means of a local mechanical final control element, is brought to a predetermined position by a central drive unit that is connected by way of a rotary shaft arrangement to the local final control element by generating a torque transmitted by the central drive unit to the rotary shaft arrangement. If a signal is registered that indicates that there is a blockage within the high lift surface system, the torque transmitted by the central drive unit to the rotary shaft arrangement is automatically reduced to a predetermined low torque value, and the position of the high lift surface system is fixed.

Abstract: The movable surfaces affecting the camber of a wing are dynamically adjusted to optimize wing camber for optimum lift/drag ratios under changing conditions during a given flight phase. In a preferred embodiment, an add-on dynamic adjustment control module provides command signals for optimum positioning of trailing edge movable surfaces, i.e., inboard flaps, outboard flaps, ailerons, and flaperons, which are used in place of the predetermined positions of the standard flight control system. The dynamic adjustment control module utilizes inputs of changing aircraft conditions such as altitude, Mach number, weight, center of gravity, vertical speed and flight phase. The dynamic adjustment control module's commands for repositioning the movable surfaces of the wing are transmitted through the standard flight control system to actuators for moving the flight control surfaces.

Abstract: Multiple data and images are multiplexed and sequenced in order to minimize the recording and monitoring hardware required to process the images, providing a detailed record of an event, greatly enhancing event reconstruction efforts. The multi-media safety and surveillance system for aircraft incorporates a plurality of strategically spaced sensors including video imaging generators for monitoring critical components and critical areas of both the interior and the exterior of the aircraft. The captured data and images are recorded and may be transmitted to ground control stations for real time or near real time surveillance. The system includes a plurality of strategically located video image sensors such as, by way of example, analog and/or digital video cameras, a video data recorder (VDR) and a pilot display module (MCDU or MIDU). All data is in recorded in an IP format. The IP encoder may be an integral component of the VDR, or the data may be transmitted in an IP format from the data generator device.

Abstract: One embodiment of the present invention is a method for automatically controlling the conversion of a tiltrotor aircraft. An airspeed command for the tiltrotor aircraft is received. The airspeed command is converted to a pylon position. A difference between the airspeed command and a measured airspeed is calculated. The difference between the airspeed command and a measured airspeed is converted to a dynamic pylon position. A total pylon position is calculated from the pylon position and the dynamic pylon position. A pylon of the tiltrotor aircraft is moved to the total pylon position. Another embodiment of the present invention is a system for calculating a position of a pylon of a tiltrotor aircraft based on an airspeed command. The system includes an airspeed command module, a pylon trim position module, a dynamic pylon position module, and a pylon position module.

Abstract: A method and system for preventing the control of an aircraft from the cockpit. In an exemplary embodiment, the system could be triggered externally. For example, an air traffic control (ATC) station could determine that the aircraft has deviated from its planned flight path. If personnel at the ATC station decide that the deviation is not attributable to the actions of the authorized flight crew, the personnel can transmit a signal to the aircraft that disables all normal cockpit control of the aircraft. Once normal flight controls are disabled, the aircraft may execute a preprogrammed emergency flight plan via its autopilot system, with or without the use of a flight management system (FMS). The emergency flight plan could cause the aircraft to fly to a sparsely populated area and enter a holding pattern, or it could cause the aircraft to land in a sparsely populated area or at an airport using an autoland system.

Abstract: A system useable in a jet aircraft having installed therein a pressurized oxygen supply which feeds oxygen into the interior of the plane when it flies at high cabin altitudes, the system indicating the changing status of the supply as oxygen is drained therefrom. The system includes a pressure transducer coupled to the supply and means associated with the transducer to determine the lapse rate at which the pressure of the supply is reduced as oxygen is drained therefrom to yield a first signal representing this pressure lapse rate, and to concurrently determine the lapse rate at which the number of liters of oxygen in the supply is reduced as oxygen is drained therefrom to yield a second signal representing the liter lapse rate. These signals are applied to a microprocessor in whose data base is entered the total oxygen inventory of the supply and the oxygen demand of the plane in which the supply is installed.