ASN Wikibase Occurrence # 387124
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| Date: | Saturday 20 January 2024 |
| Time: | |
| Type: |  AgustaWestland AW139 |
| Owner/operator: | Caverton Helicopters |
| Registration: | 5N-BSG |
| MSN: | 41360 |
| Fatalities: | Fatalities: 0 / Occupants: 12 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | 11.95 NM WSW ERHA -
 Nigeria
|
| Phase: | En route |
| Nature: | Passenger - Non-Scheduled/charter/Air Taxi |
| Departure airport: | Lagos-Murtala Muhammed International Airport (LOS/DNMM) |
| Bonga Floating Production Storage and Offloading (FPSO) | |
| Investigating agency: | NSIB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
The AW139 helicopter departed Murtala Muhammed Airport, Lagos (DNMM) for Bonga Floating Production Storage and Offloading (FPSO) as a charter flight, 360A, on an Instrument Flight Rules (IFR) flight plan. On board were 12 persons including 2 crew; with 3 hours endurance.
The Captain was the Pilot Flying (PF) while the First Officer was the Pilot Monitoring (PM). Before take-off, both Auto Pilots (AP) were switched ON, on ground in accordance with the Pre-Take Off checklist procedure. After take-off, the aircraft climbed to 1,500 ft initially, and requested 2,500 ft from Lagos Air Traffic Control (ATC).
At 08:19 h, the crew reported reaching ETVOV, a waypoint on a radial 151 and 69 NM from LAG, maintaining 2,500 ft on QNH. During cruise at 2,500 ft, AP 2 fault warning came up on Crew Alerting System (CAS) message.
The crew attempted unsuccessfully to clear it by disengaging and re-engaging the Auto Pilot. The FDR captured five disengagements and re-engagements of AP 2 in a 2-minute period. The crew then reset the Gangbar (Master Gen. 1 & 2) to clear the fault, without success.
The crew further reported that AP 1 fault warning came up, and aircraft nose dropped. The Captain took manual control of the flight while the First Officer continued attempts to re-engage the Automatic Flight Control System (AFCS).
According to FDR data, simultaneous with the attempts to re-engage the AFCS, the aircraft climbed to about 3,500 ft within a period of 1 min and 40 s, followed by a rapid descent to 330 ft in 45 s. FDR shows that the aircraft commenced another climb to 2,500 ft in the next 2 mins within which period, several pitch and roll control inputs were recorded; pitch angle varied between 28o pitch up and 12o pitch down before a maximum 25° pitch down motion was recorded, simultaneous with the maximum recorded roll angle of 37° to the right.
Over the next 44 s, the PF attempted to correct the right roll unto datum and continued into a left roll to a maximum angle of 15° before recovering to level flight 9 min later, following a series of roll attitude corrections.
The crew reported that to re-establish control of the aircraft, the Pilot ‘guarded the controls’ while the First Officer monitored the instruments and made call-outs of attitude and position.
Attempts to re-engage the Auto Pilot were eventually successful when AP 1 came engaged, followed by AP 2, 4 s later. The aircraft then settled on level flight path at about 800 ft. The crew climbed to, and stabilized the aircraft at 1,000 ft AGL, and made an Air Return. The FDR indicated that the aircraft was flown with both Auto Pilot engaged from this point till the end of the flight.
About 52 min later, the aircraft commenced a descent to 500 ft within 90 s, at which altitude it flew for the next 5 min before commencing final descent to Lagos air field.
At 10:00 h, the aircraft landed at DNMM.
The passengers disembarked safely.
Accident investigation:
 |
|
Sources:
NSIB
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 01-May-2024 10:18 | ASN | Added |
| 01-May-2024 10:18 | ASN | Updated [Aircraft type] |
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