A system to maintain a phase difference is disclosed. Two or more aircraft fly in a continuous periodic trajectory. The system maintains a phase difference between the two or more aircraft. Telemetry information for a reference aircraft moving in a first periodic trajectory is received. A phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory is determined. A variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference is determined. A new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the new periodic trajectory is determined, and the primary aircraft is maneuvered to follow the new trajectory.

Systems, apparatus and methods for disinfection of airflow. An apparatus for disinfecting air-conditioned airflow in a confined space includes: a modular housing; and a disinfection chamber enclosed within the housing. The disinfection chamber includes a plurality of disinfection sheets. Each disinfection sheet comprises a plurality of ultraviolet (UV) light sources. The airflow is configured to be routed along a serpentine pathway within the housing to expose microorganisms in the airflow to far UV-C light emitted by the UV light sources for an extended and optimal duration.

A cabin air control system for an aircraft comprising a plurality of compressed air sources, each operable to provide compressed air, at least one air outlet, a conduit system connected to the air sources and the air outlet and arranged to conduct air from the air sources downstream to the air outlet, and a plurality of particulate matter detectors configured to detect the presence of particulate matter in air from the air sources. Each detector is associated with a different predefined subset of the air sources by being arranged in the conduit system at a location from which it is only possible to reach the associated subset of the air sources when traversing the conduit system from the respective location towards the air sources in an upstream direction. Any two subsets of the different subsets associated with the different particulate matter detectors include different ones of the air sources.

A method for evaluating an air purification system. The method includes generating, with an air flow generator, a flow of air through a test filter so that an upstream air flow exists an upstream side of the test filter and a downstream air flow exists on a downstream side of the test filter. A multiple contaminant mixture is injected, with a fluid injector, into the upstream air flow. Downstream concentrations for each contaminant of the multiple contaminant mixture in the downstream air flow are measured with a contaminant measurement device. Test filter breakthrough curves for each contaminant of the multiple contaminant mixture in the downstream air flow are generated based on the downstream concentrations for each contaminant of the multiple contaminant mixture.

A system to maintain a phase difference is disclosed. Two or more aircraft fly in a continuous periodic trajectory. The system maintains a phase difference between the two or more aircraft. Telemetry information for a reference aircraft moving in a first periodic trajectory is received. A phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory is determined. A variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference is determined. A new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the new periodic trajectory is determined, and the primary aircraft is maneuvered to follow the new trajectory.

An aircraft environmental control system comprising a fresh air input and a RAM air input, heat exchanger means for receiving fresh air from the fresh air input and RAM air from the RAM air input and using the RAM air to cool the fresh air, and means for providing the cooled fresh air to a cabin of the aircraft, the system further comprising means for feeding back exhaust air emitted from the interior of the aircraft to combine with the RAM air to further cool the fresh air, whereby the heat exchanger means comprises a main heat exchanger and a primary heat exchanger; wherein the main heat exchanger comprising a main heat exchanger cooling fluid inlet, a main heat exchanger cooling fluid outlet and a main heat exchanger bleed air inlet, the cooling fluid working to cool bleed air in the main heat exchanger.

One embodiment is a passive particle separation system including a plenum; an inlet for feeding outside air into the plenum, wherein the outside air has particles entrained therewith; a housing for enclosing the plenum; and a standpipe installed on the housing. The outside air enters the plenum via the inlet and plenum, housing, and standpipe interact to impact the outside air entering the plenum to cause the particles to be released from the outside air.

A system that filters airborne particles when the aircraft is in a dusty environment and is disengaged when the aircraft is flying up and away from the dusty environment.

An environmental control system that includes a first environmental control system pack, a first recirculation fan assembly, and a cabin air sensor unit. The first environmental control system pack is arranged to provide conditioned air to an aircraft cabin. The first recirculation fan assembly is arranged to recirculate a first cabin air fluid flow back to the aircraft cabin. The cabin air sensor unit is arranged to provide a first air quality signal indicative of an air quality of the first cabin air fluid flow to a controller.

A system to maintain a phase difference is disclosed. Two or more aircraft fly in a continuous periodic trajectory. The system maintains a phase difference between the two or more aircraft. Telemetry information for a reference aircraft moving in a first periodic trajectory is received. A phase difference between a primary aircraft and the reference aircraft with respect to the first periodic trajectory is determined. A variance in the phase difference between the primary aircraft and the reference aircraft from the target phase difference is determined. A new trajectory for the primary aircraft that decreases the variance in the phase difference with respect to the new periodic trajectory is determined, and the primary aircraft is maneuvered to follow the new trajectory.