What happened
On October 03, 2022, an Embraer EMB-545, registration N179SP, was operating a business flight near Houston, Texas, under VMC weather conditions. The crew, consisting of two pilots, was accompanied by two passengers.
During the initial climb, the aircraft failed to pressurize. Flight data recorder information indicated that the main entry door vent flap was open and the door was not fully closed. As the aircraft climbed through approximately 5,280 feet, a master warning and a "DOOR PAX OPEN" message appeared on the crew alerting system.
The pilot in command (PIC) left his seat to inspect the door and attempted to push the handle into the locked position, but reported that the handle would not stay down. Approximately 14 seconds after the pilot left his seat, the cabin door opened while in flight, causing substantial damage to the door and the fuselage. The flight subsequently returned to land. During the landing phase, the door made contact with the runway, resulting in further substantial damage to the aircraft. All four occupants were not injured.
The investigation
Post-accident examination of the aircraft found no mechanical anomalies that would have prevented the door from being closed, latched, or locked. However, investigators discovered that a locked sensor assembly was jammed due to corrosion. This malfunction caused the crew alerting system to provide a false indication that the door was locked when it was actually only in the latched position.
While the electronic system provided an erroneous signal, the two visual locked indications on the door itself were partially red, which correctly indicated that the door was not locked. Investigators determined that aerodynamic forces or aircraft vibration likely caused the door sensor target to move during the climb, triggering the warning. It is believed that aerodynamic forces, vibration, or the pilot's manual manipulation of the handle allowed the door to open in flight.