Abstract: A brake system is disclosed herein. The brake system includes a motor, a hydraulic pump mechanically coupled to the motor, a directional control valve fluidly coupled to the hydraulic pump, and a brake assembly fluidly coupled to the directional control valve. The directional control valve is moveable between a braking position, in which the directional control valve allows hydraulic fluid to flow between the hydraulic pump and the brake assembly, and a parking position, in which the directional control valve prevents the hydraulic fluid from flowing between the hydraulic pump and the brake assembly.

Abstract: A system includes a first sensor positioned to sense presence of a contrail in a first volume, wherein the first volume at least partially overlaps an expected volume of a contrail proximate an aircraft. A second sensor is positioned to sense a background reference in a second volume, where the second volume does not overlap the expected volume of a contrail proximate an aircraft. A controller is operatively connected to the first and second sensors. The controller includes machine readable instructions configured to cause the controller to utilize data input from both the first and second volumes to determine if a contrail is present from the aircraft. A system includes machine readable instructions configured to cause the controller to predict persistence of contrails on an intended route through the volume of airspace and to determine an improved route and/or propulsion operation to reduce contrail formation and persistence relative to the intended route.