Investigation Summary
The sequence began during climb-out when improperly secured insulation blankets, manufactured by the airline, migrated and partially blocked the forward and aft outflow valves. This caused a pressurization malfunction that the crew attempted to manage by switching to manual control. During the return to Miami, abnormal pressure levels triggered false lavatory smoke alarms and a cargo fire loop light. The crew, focused on the perceived fire threat, did not complete the 'Cabin Pressurization Manual Control' or 'Emergency Landing' checklists, both of which contained steps to ensure the aircraft was depressurized. Upon landing, the captain initiated an evacuation. Because the outflow valves do not automatically open in manual mode and the crew had not manually opened them, the cabin was pressurized to a level that made the doors nearly impossible to open normally. The purser, Jose Chiu, persistently attempted to open the L1 door, eventually overcoming the mechanical locks. This led to a violent decompression that threw him 40 to 60 feet from the aircraft, resulting in fatal injuries. The force of the door opening also knocked two flight service directors (language translators) unconscious; one sustained minor injuries while the other was uninjured. In total, besides the fatality, 3 passengers sustained serious injuries and 19 others (18 passengers and 1 flight service director) sustained minor injuries.
Final Conclusions
The NTSB determined the probable cause was the flight crew's failure to perform the cabin pressurization manual control abnormal checklist and the emergency landing checklist, resulting in excessive cabin pressure after landing. Contributing factors included the failure of maintenance personnel to properly secure insulation blankets, the lack of pressure-relief systems or warnings on emergency doors, and the absence of a depressurization check in the ground evacuation checklist. The investigation also noted that the cabin altimeter lacked a mechanical stop, which could lead to misleading readings under excessive pressure.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
First Officer
Systems & Failure Modes
Pressurization Outflow Valves
Two valves (forward and aft) that regulate cabin pressure by controlling the exhaust of air. In manual mode, these valves do not automatically open upon landing.
Cabin Altimeter
A cockpit instrument indicating cabin altitude. The unit lacked a mechanical stop, allowing the needle to sweep into misleading ranges under extreme pressure.
Ionization Smoke Detectors
Sensors in lavatories and cargo bays that triggered false alarms due to the rapid pressure fluctuations caused by the blocked outflow valves.
Interesting Facts
- 01The aft outflow valve was found fully closed and the forward valve was only 3/8 open due to insulation blanket obstruction.
- 02The insulation blankets involved were manufactured by American Airlines and lacked the fasteners recommended by Airbus.
- 03The aircraft was pressurized to approximately 1.5 psi differential or higher at the time of the evacuation attempt, resulting in an estimated 1,500 pounds of force against the door.
- 04The RAM AIR switch, which the crew activated, does not open the outflow valves when the system is in manual mode.
- 05Post-accident testing showed ionization smoke detectors could trigger false alarms when subjected to abnormal pressure changes.
Safety Actions & Advisories
Checklist Revision
The NTSB recommended that ground/emergency evacuation checklists include a specific requirement for the flight crew to ensure cabin differential pressure is zero before signaling an evacuation.
Door Design Requirements
Recommendations were issued to the FAA to require emergency exit doors to have systems to relieve pressure or provide clear warnings of over-pressurization.
Location
ACCIDENT SITE · Coordinates taken from the ntsb final report.