Alaska Airlines Door-Dropping Flight Missing Bolts
Preliminary investigation confirms pilot chat was overwritten but doesn't mention attempts to recover data
Improperly Bolted Door Plug Causes Incident
According to a preliminary investigation, the door plug that fell out of Alaska Airlines flight 1282 last month was not properly bolted into place. The incident occurred on January 5 when the Boeing 737-9 Max experienced a rapid decompression due to the door plug - a structure installed in place of an optional emergency door - falling out. The investigation revealed that the bolts connecting the door plug to the Mid Exit Door plug were missing.
Fortunately, all 177 passengers and crew on board de-planed safely. However, this incident has once again tarnished Boeing's reputation in terms of safety and quality control.
Report Observes the State of the Door Plug
The preliminary investigation report issued by the US National Transportation Safety Board (NTSB) acknowledged that the cabin pressure control system functioned as designed. The report also mentioned that airplane maintenance logs had entries indicating a pressure controller light had illuminated on three previous flights, suggesting the plane performed as intended.
Additionally, the investigation examined the state of the blown-out door plug, which was recovered in the backyard of a private residence and analyzed at the NTSB's Maintenance Laboratory. It was concluded that the four bolts designed to hold the door plug in place were missing, leading to its departure from the airplane.
Missing Bolts Identified Prior to Flight
Evidence suggests that the bolts were missing before the flight took off. The report indicated that they were removed after a work order was created to fix damaged rivets at the edge of the door frame. Employees of contractor Spirit AeroSystems, the MED plug maker, performed the rivet repair on September 19 the previous year. A photo exchange between Boeing team members discussing interior renovation showed no visible bolts in three locations.
This information raises concerns about the manufacturing process and associated records at Boeing, which the NTSB is currently investigating.
Cockpit Voice Recorder Doesn't Retain Recordings
The report also mentioned that the Cockpit Voice Recorder (CVR) on the Boeing 737-9 MAX did not retain recordings of pilot chatter during the incident. The CVR is only required to store two hours of audio before overwriting itself, although it can be manually deactivated to preserve recordings after landing. The Flight Data Recorder did document the period when the door plug departed.
It is peculiar that the NTSB report did not mention any data recovery efforts to retrieve the overwritten audio, especially considering modern CVRs use digital storage media. Data recovery services have shown it is possible to recover overwritten information, even on reformatted drives.
