Investigators have notified United Nigeria Airlines of a need to ensure compliance with recommendations to upgrade Embraer ERJ-145 nose-wheel steering systems, after a runway excursion accident at Lagos.
The aircraft, arriving from Ebonyi on 31 May last year, had touched down on runway 18L but subsequently veered off the right side of the runway.
It crossed drainage channels and a link taxiway, suffering a nose-gear collapse, before coming to a halt on grass some 1,860m from the threshold.
Weather conditions at the time were good with no precipitation.
None of the 50 passengers and four crew members was injured, but the jet (5N-BWW) suffered substantial damage.
Nigeria’s Safety Investigation Bureau has yet to reach conclusions on the accident, but it states in preliminary findings that United Nigeria should comply with an Embraer service bulletin, issued in April 2005, to upgrade the nose-wheel steering hydraulic manifold.
This service bulletin addressed premature deterioration of O-ring seals within the electro-hydraulic servo valve within the manifold.
The valve converts electrical nose-wheel steering commands into hydraulic pressure.
Embraer’s bulletin followed incidents in which ERJ aircraft had experienced uncommanded swerving on the ground – with the nose-wheel steering system not responding to pilot input – investigations into which had confirmed failures in the servo valve.
Nigerian investigators have also been probing a second runway excursion at Lagos involving a United Nigeria ERJ-145 (5N-BWY), which occurred about three months later on 8 September. It is unclear whether this excursion, which took place in poor weather, had any contributing factors in common with the May accident.
