B190, vicinity Bebi south eastern Nigeria, 2008
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|On 15 March 2008, a Beech 1900D on a non-revenue positioning flight to a private airstrip in mountainous terrain flown by an inadequately-briefed crew without sufficient guidance or previous relevant experience impacted terrain under power whilst trying to locate the destination visually after failing to respond to a series of GPWS Alerts and a final PULL UP Warning. Whilst attributing the accident to the crew, the Investigation also found a range of contributory deficiencies in respect of the Operator, official charting and ATS provision and additional deficiencies in the conduct of the unsuccessful SAR activity after the aircraft became overdue.|
|Actual or Potential
|Controlled Flight Into Terrain (CFIT), Fire Smoke and Fumes, Human Factors|
|Type of Flight||Public Transport (Non Revenue)|
|Origin||Murtala Muhammed International Airport|
|Intended Destination||Bebi Airstrip|
|Take off Commenced||Yes|
|ENR / APR|
|Location - Airport|
|Airport vicinity||Bebi Airstrip|
|Tag(s)||Inadequate Aircraft Operator Procedures,|
Inadequate ATC Procedures,
Ineffective Regulatory Oversight,
Copilot less than 500 hours on Type
No Visual Reference,
Lateral Navigation Error,
Vertical navigation error,
VFR flight plan
|Tag(s)||Post Crash Fire|
|Tag(s)||Inappropriate ATC Communication,|
Inappropriate crew response - skills deficiency,
Plan Continuation Bias,
Procedural non compliance,
|Safety Net Mitigations|
|Malfunction of Relevant Safety Net||No|
|TAWS||Available but ineffective|
|Damage or injury||Yes|
|Aircraft damage||Hull loss|
|Fatalities||Most or all occupants ()|
|Causal Factor Group(s)|
Air Traffic Management,
On 15 March 2008, a BEECH 1900D (5N-JAH) being operated by Wings Aviation on a revenue positioning flight from Lagos to Bebi as TWD8300 went missing in mountainous terrain near to its intended destination in daylight hours. SAR activity began the same day and continued for a week but when it failed to locate the aircraft, it was called off. The wreckage was eventually discovered by chance six months later in the vicinity of the destination airstrip. It was apparent that the impact had been non survivable for the three occupants and that there had been a post-crash fire.
An Investigation was carried out by the Nigerian Accident Investigation Bureau (AIB).
Progress was limited until the airplane wreckage was eventually found by local hunters on 30 August 2008 about 5nm south west of Bebi airstrip in hilly terrain at an altitude of approximately 3200 feet. It was spread over a sizeable area in a wooded valley. Investigators visited the site and recovered both the FDR and CVR which were taken to the UK AAIB and successfully downloaded. Since both recorders had sustained impact and severe fire damage, data could not be extracted from either in the normal manner and alternative techniques were employed.
At the crash site they found a 200 foot-long wreckage trail and evidence of severe impact damage from a high speed impact as well as signs of post-crash fire. There was no evidence that there had been a pre-impact fire or any in-flight separation of the aircraft.
It was established that the aircraft had departed Lagos on an IFR Flight Plan with just the two pilots and a staff passenger (who was qualified as cabin crew) on board. The Captain was PF. A climb to FL 250 was made towards Enugu but a track deviation from the filed flight plan then occurred and the aircraft took a slightly different route south of Enugu and towards a waypoint south west of Bebi situated on the Cameroon border. This departure from the filed flight plan was not properly communicated to ATC. It was cleared to descend initially to FL 160 by Port Harcourt TWR and then by Enugu TWR to descend to FL 050. It was noted that this latter clearance was invalid since it had been given when the aircraft had already left Enugu-controlled airspace which has a lateral limit defined by a 30 nm radius circle from ground level to FL 105.
It became evident from CVR data that the crew were soon beginning to make use of GPS navigation and, having agreed and input a coordinate for Bebi, were attempting to locate the airstrip. FDR data showed that the aircraft had descended to FL 080 and then climbed back to FL090 within little over a minute. It had then maintained that level for another 12 minutes before beginning a descent to 3500 feet which took 4 minutes.
Soon after reaching this altitude, the Captain was recorded as saying "we have to go down further". At 3.5 minutes prior to impact, both pilots were "still looking out for the ground and landmarks". Ninety seconds later, the approach checklist was begun and was complete after 22 seconds. One minute later (36 seconds before impact) the first GPWS 'Too Low Terrain' Caution activated followed 9 seconds later by "multiple GPWS warnings". After a further 16 seconds, a GPWS Hard Warning of 'TERRAIN TERRAIN PULL UP' began but there was no crew response. Six seconds later, the Captain uttered an expletive and the First Officer simultaneously shouted "climb" and after a further five seconds, the aircraft impacted terrain at a recorded altitude of 3400ft one hour and forty five minutes after leaving Lagos. It was calculated from FDR data that had the aircraft been fitted with EGPWS, the crew would have received terrain alerts 36 seconds earlier than they did because of its forward looking capability.
FDR data showed that all engine and flight controls were functioning normally until the moment the aircraft impacted terrain. The same source confirmed that there had been power on both engines, the speed at impact was over 150 knots and the propeller speed on both engines was about 1500 rpm. It was calculated by the Investigation that shortly before the crash, the fuel endurance was three and half hours, which meant that there was a large quantity of fuel still on board.
It was found that the 60-year old Captain had 9730 hours flying experience which included 852 hours on the Beech 1900D. He was also the Flight Safety Pilot for the airline. From evidence available, it appeared that he had only landed in Bebi once previously, some 15 months earlier. A second attempt to do so had ended in a diversion to Calabar and the third attempt was the crash. Contrary to the requirements of the Nigeria Civil Aviation Regulations, he had never had a route check to Bebi. The 36 year old First Officer had 444 hours flying experience which included 204 hours on type. His limited operational experience did not include Bebi.
It was noted that the Bebi facility was a private airstrip which was neither licensed nor certified by the NCAA. It lies under the airway UA 604 at an elevation of 850 feet. On the Jeppesen IFR chart, the Minimum Off Route Altitude (MORA) in the area is shown as 11200 feet but no similar information appeared on the en route IFR chart published by the Nigerian Airspace Management Agency (NAMA) which was used by the accident aircraft crew.
There is a single runway 10/28 which is 1800 metres long. It was found that this runway was contaminated with rubber deposits in the TDZ at both ends and noted that no evaluation of runway friction level had ever been carried out. There is no Air Traffic Control Service at Bebi, but an unlicensed radio operator, with whom the crew had been in contact. An ILS and an NDB were installed at the airstrip but neither was commissioned for operation and no generally-available approach chart had been published for Bebi by NAMA (or Jeppesen) and no other instrument or visual approach procedure charts were available to the crew. Other operators using Bebi were found by the Investigation to have developed their own unapproved "in-house" procedures which, whilst helpful to crew situational awareness, were considered to represent an unsafe practice "which should not be encouraged (and) therefore the Regulatory Authority should address it".
There was a meteorological office operated by the Nigeria Meteorological Agency (NIMET) which was open during daylight hours. The TAF for Bebi issued shortly before the aircraft left Lagos and valid for its ETA gave the wind Calm, visibility 8km and the cloud FEW at 975 feet and BKN at 2925 feet (converted heights which were actually given as 300 metres and 900 metres respectively since NIMET uses metres for aviation weather purposes).
The Investigation found that the NAMA en route IFR chart used by the crew was found to co-locate Bebi and the OBUDU waypoint whereas the two locations are 27 nm apart. SAR aircraft from NEMA which landed at Bebi during the initial search for the accident aircraft reported that its actual coordinates were N 6° 39' 23, E° 9 19' 46 compared to the chart position for OBUDU which was N 6° 10' 2, E° 9 15' 28. It was noted that as they began trying to locate the airstrip, the pilots had loaded co-ordinates that produced conflicting distances to Bebi on their respective GPS displays. One gave it as 27 miles away, the other as 62 miles away. It was noted that this error had temporarily caused the crew to be confused and distracted. It was considered that "operation into Bebi from the northwest is less hazardous than approach from the south which has mountainous terrain and requires a good knowledge of the area and operational experience" which neither pilot had.
An examination of Wings Air in terms of operational standards found some significant deficiencies. These included:
- There was no evidence in crew training files to show that the accident crew had completed any recency, route check or CRM within the last year.
- The crew used a NAMA/AIS Route Map instead of the Jeppesen charts required under the NCAA-approved Company Operational Specifications.
- The operator did not appear to have any documented procedures for use when operating into Bebi.
The SAR effort was found to have been undertaken without the use of any serviceable Infra Red detection equipment, which was considered to be a material failure when carrying out this activity in such a difficult environment.
The Investigation determined that the Cause of the accident was Controlled Flight Into Terrain which had occurred when the flight crew conducted an approach into a Visual Flight Rules (VFR) airfield in Instrument Meteorological Conditions (IMC), did not maintain terrain clearance and minimum safe altitude and did not respond promptly to GPWS warnings.
Two Contributory Factors were also identified:
- The flight crew was not familiar with the route in a situation of low clouds, poor visibility and mountainous terrain.
- The Area Controllers did not detect the estimate passed by the pilot was for positions not in the filed flight plan (LIPAR and LUNDO) or the omission of ENUGU.
The disparity in the co-ordinates of Bebi Airstrip and of Obudu on the NAMA en route chart has been corrected by the issue of a new chart by NAMA.
Five Safety Recommendations were made as a result of the Investigation:
- that the Nigerian CAA (NCAA) and the Nigerian Airspace Management Agency (NAMA) should ensure that Bebi airstrip is certified and licensed with all available nav-aids made functional and effectively maintained with appropriate charts and correct coordinates.
- that the NCAA should ensure that Airstrip operator services and maintains ILS and VOR/DME where installed and the Authority to provide Approach and Area charts for the Airstrip.
- that All Search and Rescue Aircraft owned by Government agencies such as the Nigerian Emergency Management Agency (NEMA) and the Nigerian Air Force, Border Patrol and Police should be well equipped with specialised equipment suitable for efficient conduct of Search and Rescue missions. Such equipment should include:
- Rescue Hoist
- Emergency Floatation Kit
- Night-Sun Search light
- Auxiliary Fuel System for Extended Range
- Cargo Hook
- Stretcher System
- HF Radio
- Forward Looking Infra-Red System
- that the NCAA should ensure compliance of AOC holders with NCAR Part 22.214.171.124 (the requirement for route checks to special airstrips at not less than 12 month intervals) and increase their surveillance.
- that Wings Aviation Limited should enhance safety in their operations by developing an approved SOP which should include but not be limited to:
- Aircraft dispatch procedure
- CRM, Route and Recency checks for the crew in accordance with NCAR. 126.96.36.199 and 188.8.131.52.
- Operation in a hazardous environment (mountainous area)
- and should also ensure that safety critical appointments are not concentrated in a multiple manner in the hands of a specific or particular person, so as to encourage checks and balances in their operations.
The Final Report was released on 21 May 2015.
- Controlled Flight Into Terrain (CFIT)
- CFIT Precursors and Defences
- Approach and Landing Risks
- Terrain Avoidance and Warning System (TAWS)
- Response to a "PULL UP" Warning
- Terrain Awareness
- Flight in Mountainous Terrain
- Mountainous Terrain Escape Routes
- Safety Oversight
- Crew Resource Management (CRM)
- Minimum Obstacle Clearance Altitude (MOCA)
- Jepessen charts presentation, Jim Tepstra, Jepessen (2007)