Abstract: An aircraft and system of doors for providing security to a flight deck of the aircraft, and methods for operating the same, are provided. A passenger cabin is separated from a flight deck by an aisle that includes doors at either end. The doors are locked by a controller and one of the doors may only be unlocked, during a flight, if the remaining door is locked. As a result, a pilot can access a lavatory in the aisle in a secure manner. Additionally, the door closest to the passenger cabin may include a window that allows the pilots to view the passenger cabin through a peephole in the flight deck door. The controller may selectively dim or block a view through the window to prevent monitoring of the pilots' movements onto and off of the flight deck.

Abstract: A filter assembly including a plurality of filter modules, wherein each filter module in the plurality of filter modules includes a frame, a filtration element coupled within the frame, and at least one mating feature. The at least one mating feature of each filter module is configured for selective engagement with the at least one mating feature of another filter module such that the plurality of filter modules are coupled together in a serial arrangement.

Abstract: An aircraft and system of doors for providing security to a flight deck of the aircraft, and methods for operating the same, are provided. A passenger cabin is separated from a flight deck by an aisle that includes doors at either end. The doors are locked by a controller and one of the doors may only be unlocked, during a flight, if the remaining door is locked. As a result, a pilot can access a lavatory in the aisle in a secure manner. Additionally, the door closest to the passenger cabin may include a window that allows the pilots to view the passenger cabin through a peephole in the flight deck door. The controller may selectively dim or block a view through the window to prevent monitoring of the pilots' movements onto and off of the flight deck.

Abstract: A filter assembly including a plurality of filter modules, wherein each filter module in the plurality of filter modules includes a frame, a filtration element coupled within the frame, and at least one mating feature. The at least one mating feature of each filter module is configured for selective engagement with the at least one mating feature of another filter module such that the plurality of filter modules are coupled together in a serial arrangement.