The Nigerian Accident Investigation Bureau recently issued an investigative report detailing its findings after a Boeing 737-500—with 113 passengers and crew on board—lost cabin pressure 23 min. into a flight on June 5, 2015.
The incident occurred on the first commercial flight after an engine installation. The probable cause was reportedly the improper position of a pressure release shut-off valve; investigators found no evidence that post-installation procedures were followed to ensure the valve was locked.
The bureau directed its safety recommendation at the regulator, stating that the Nigerian Civil Aviation Authority must ensure operators perform proper maintenance in compliance with aviation regulations.
The Nigerian authority responded that it was “considering requiring operators of aircraft to mandatorily inform [the authority] of any engine changes prior to accomplishment,” maintaining that notification would allow the authority to monitor the process.
The investigative report was one of four issued on Nov. 29. The bureau has aggressively issued safety reports to clear the backlog of accident investigations, which numbered 27 in early 2017.