What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Co-pilot secured door and verified cabin door and cabin seal light were extinguished. The pilot taxied to the runway and began takeoff. During climb, at about 400 ft, pilot noticed both cabin door and cabin seal lights became illuminated. The co-pilot verified the lights were illuminated and checked security of the door. The door appeared secured and he did not hear any wind or other indication that the door may have come ajar. Both pilots agreed to return for a precautionary landing, and coordinated request with ATC. The pilot was assigned a heading and 2,000 ft AGL and told to contact potomac TRACON. Pilots contacted potomac TRACON and advised the TRACON that they would need to dump fuel before landing. Potomac TRACON assigned an easterly heading and 4,000 ft AGL. Upon reaching the assigned altitude the door blew open and took out communications. Pilots transmitted to ATC mayday mayday mayday and squawked 7700 with no response. The pilots were able to land without further incident.
As the FAA filed it
CO-PILOT SECURED DOOR AND VERIFIED CABIN DOOR AND CABIN SEAL LIGHT WERE EXTINGUISHED. THE PILOT TAXIED TO THE RUNWAY AND BEGAN TAKEOFF. DURING CLIMB, AT ABOUT 400 FT, PILOT NOTICED BOTH CABIN DOOR AND CABIN SEAL LIGHTS BECAME ILLUMINATED. THE CO-PILOT VERIFIED THE LIGHTS WERE ILLUMINATED AND CHECKED SECURITY OF THE DOOR. THE DOOR APPEARED SECURED AND HE DID NOT HEAR ANY WIND OR OTHER INDICATION THAT THE DOOR MAY HAVE COME AJAR. BOTH PILOTS AGREED TO RETURN FOR A PRECAUTIONARY LANDING, AND COORDINATED REQUEST WITH ATC. THE PILOT WAS ASSIGNED A HEADING AND 2,000 FT AGL AND TOLD TO CONTACT POTOMAC TRACON. PILOTS CONTACTED POTOMAC TRACON AND ADVISED THE TRACON THAT THEY WOULD NEED TO DUMP FUEL BEFORE LANDING. POTOMAC TRACON ASSIGNED AN EASTERLY HEADING AND 4,000 FT AGL. UPON REACHING THE ASSIGNED ALTITUDE THE DOOR BLEW OPEN AND TOOK OUT COMMUNICATIONS. PILOTS TRANSMITTED TO ATC MAYDAY MAYDAY MAYDAY AND SQUAWKED 7700 WITH NO RESPONSE. THE PILOTS WERE ABLE TO LAND WITHOUT FURTHER INCIDENT.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.