Aero Contractors Boeing 737 Loses Cabin Pressure After Engine Change Oversight

An Aero Contractors Boeing 737-500, registration 5N-BLE, operating scheduled flight NIG181 from Lagos to Kaduna on the evening of 5 June 2015, suffered a loss of cabin pressurisation shortly after departure, according to the Accident Investigation Bureau's final report on the occurrence. The aircraft, carrying 108 passengers and five crew, had climbed to Flight Level 330 when the crew noticed the cabin altitude climbing well beyond normal limits.

Investigators traced the fault to work carried out during a recent engine change, in which a bleed-air valve linked to the pressurisation system was left in the closed position and not identified during subsequent checks. With cabin pressure falling, the crew declared an emergency, initiated an emergency descent and the oxygen masks deployed automatically for passengers, while the flight crew donned their own masks as procedure requires.

A Preventable Maintenance Gap

The aircraft was brought down safely and diverted without injury to anyone on board, but the Bureau's report singled out gaps in post-maintenance verification as the underlying cause, rather than any fault in the aircraft's original design. It recommended that the Nigerian Civil Aviation Authority satisfy itself that Aero Contractors' flight operations and maintenance departments were fully compliant with the Nigeria Civil Aviation Regulations before further engine work of this kind was signed off.

Part of a Wider Pattern

The incident was one of several serious safety occurrences involving Nigerian-registered aircraft that the Bureau investigated in the middle of 2015, a run that also included a runway excursion at Port Harcourt and a ground collision between an Emirates Boeing 777 and a parked HAK Air jet at Lagos weeks later. Coming in a year already strained by fuel scarcity and a weak naira, the cluster of incidents added to pressure on Nigerian carriers to tighten maintenance oversight even as their finances remained under stress.