B742, Sokoto Nigeria, 2013

Summary: 

On 4 October 2013, a Boeing 747-200 touched down short of the intended landing runway at Sokoto after the Captain opted to reduce track miles by making a direct visual contact approach in dark night calm wind conditions rather than continuing as initially cleared towards an ILS approach in the reciprocal runway direction. The Investigation was hampered by an inoperative FDR and failure to preserve relevant CVR data on the grounded aircraft and concluded that the decision to make a visual approach rather than an ILS approach when the VASI was out of service for both runways was inappropriate.

Event Details
When: 
04/10/2013
Event Type: 
Day/Night: 
Night
Flight Conditions: 
VMC

32127

Flight Details
Aircraft: 
Operator: 
Type of Flight: 
Public Transport (Passenger)
Take-off Commenced: 
Yes
Flight Airborne: 
Yes
Flight Completed: 
Yes
Phase of Flight: 
Landing
Location
Location - Airport
Airport: 
General
Tag(s): 
CVR overwritten, Visual Approach
CFIT
Tag(s): 
Into obstruction, Vertical navigation error, IFR flight plan, Undershoot on Landing
HF
Tag(s): 
Procedural non compliance
AW
System(s): 
Indicating / Recording Systems
Outcome
Damage or injury: 
Yes
Aircraft damage: 
Major
Non-aircraft damage: 
Yes
Non-occupant Casualties: 
No
Off Airport Landing: 
No
Ditching: 
No
Causal Factor Group(s)
Group(s): 
Aircraft Operation, Air Traffic Management
Safety Recommendation(s)
Group(s): 
Aircraft Airworthiness
Investigation Type
Type: 
Independent

Description

On 4 October 2013, a Boeing 747-200 (5N-JRM) being operated by Kabo Air on a non-scheduled international passenger flight from Kano to Jeddah as QNK617 with an intermediate stop at Sokoto before leaving Nigeria made a visual contact approach there in night VMC but collided with approach lighting and the ILS 08 LOC antenna before touching down 100 metres ahead of the runway 26 threshold. It then continued onto the 3000 metre-long runway and stopped briefly before taxiing to the apron where a range of structural and landing gear impact damage was eventually identified. Subsequent inspection of the runway 26 undershoot found that a total of 21 approach lights had been destroyed and significant damage caused to the ILS 08 LOC antennae. There were no injuries to the 512 occupants.

Investigation

An Accident Investigation was carried out by the Nigerian Accident Investigation Bureau (AIB). The FDR and CVR were removed from the aircraft and downloaded but it was found that the FDR was unserviceable because its magnetic tape was broken and that relevant CVR data had been overwritten. It was noted that “the lack of data from the FDR and CVR significantly constrained the determination of the aircraft approach profile and the details of the sequence of events” and had also made it impossible to assess CRM issues and the respective roles of individual crew members. A recording of radio communications between the flight and Sokoto TWR was available and showed that all radio communications had been normal.

The 52 year-old Captain, who was PF for the accident flight, had a total of 13,805 hours flying experience of which 1,331 hours were on type and the 27 year-old First Officer had a total of 977 hours flying experience of which 649 hours were on type. The 66 year-old Flight Engineer had 21,205 hours flying experience of which 2,379 hours were on type. He also held flight engineer type ratings on the Douglas DC10 and the Boeing 707. All flight crew were Nigerian nationals. It was noted that the flight was a Hajj charter flight and that the original intention had been to make a direct flight from Kano to Jeddah but this was then modified to include a stop at Sokoto, which was only about 40 minutes flying time from Kano, to pick up more passengers. Although the Captain had confirmed the availability of fuel at Sokoto, he had decided to uplift additional fuel before departing from Kano. The flight was made at FL180 and on initial contact, Sokoto ATC advised that an ILS approach to runway 08 could be expected with the wind calm, the visibility 10km and the only cloud being FEW CB to the north west of the airport with a base at 2,500 feet aal. Descent to FL 065 was subsequently given and the flight was instructed to report when 25 DME from the airport. Subsequent re-clearance was then given to 3,500 feet QNH and for the 08 ILS approach.

On arriving overhead the SOK VOR/DME, the flight reported field in sight and requested for straight-in visual approach to runway 26 to which ATC responded with “no objection, report final runway 26”. Two minutes later, ATC cautioned that the approach lighting for runway 26 was of Low Intensity and after a further three minutes, the flight reported on an 8 mile final and was cleared to land with the wind still reported as calm. During the final part of the approach, intentionally flown at a 2½° approach angle, the aircraft collided with the 08 ILS LOC antenna and the runway 26 approach lighting system and touched down 100 metres short of the threshold of the 3000 metre-long runway. It then continued onto the runway and initially came to a brief stop before taxiing to the apron. During subsequent interview, the Captain stated that after shutting down, the crew had carried out an external inspection and discovered that two of the right main landing gear tyres had deflated after which all the passengers were disembarked.

Upon a more thorough inspection, the actual extent of the damage was found to be much more extensive than just to two tyres and included damage to the right horizontal stabiliser leading edge and a hole on its top surface, damage to the right wing flap trailing edge surfaces, holes in the lower part of the bulk cargo door and in the aft right fuselage pressurised area, damage to the right main landing gear and the right body gear door, a hole in the no 4 engine nose cowling and hydraulic fluid leakage from two of the hydraulic lines.

The Captain stated that his decision to land on runway 26 had been based on saving fuel. He also stated that his intention had been to ensure an early touchdown so as to avoid the risk of an overrun given that the landing weight was within 5 tonnes of the 256 tonne maximum landing weight (MLW). He noted that he had also observed that there was no TDZ lighting for runway 26 but did not mention that the runway 26 VASI was not in service. The Flight Engineer stated that the approach had appeared to have been normal until the 10 feet auto callout which was followed by “a thudding sound and slight vibration”. The Investigation noted that the ILS LOC antenna struck by the aircraft was 13 feet higher than the aerodrome reference point (ARP) and situated 315 metres before the runway threshold. It was found that the crew had said nothing to ATC about the undershoot and that the broken approach lights were first noticed by an airport engineer on his way to the site of the SOK VOR/DME. He had then reported his findings to the Airspace Manager who, when he mentioned these to the air traffic controller on duty, was told that they were unaware of it.

The Investigation noted the calm wind and reviewed the choice of a visual approach to runway 26 supported by a VOR/DME but with no vertical guidance due to the unserviceable VASI against the alternative of an ILS to runway 08 and concluded that “the appropriate choice of landing runway for this category of aircraft (category D) would have been the runway equipped with both vertical and lateral guidance (ILS), that being Runway 08”. It was further noted that having chosen to make a visual approach to runway 26, lateral guidance presented no problem as the VOR is aligned with the runway but with an unserviceable VASI, a continuous descent angle of 3 degrees should have been briefed with height/distance checks planned to allow the PM to monitor the descent and call out any deviations. Without this in place, the vulnerability to ‘Black Hole Effect’ was noted. Finally, it was considered that given that the aircraft could have been landed on the 3000 metre-long runway even if it had been above the maximum structural landing weight, the Captain’s stated concern in respect of runway length relative to the near-MLW landing weight “probably indicates that the approach briefing may not have considered the aircraft landing performance for that runway”.

The Cause of the Accident was formally documented as “an inappropriate visual approach profile flown at night with no vertical guidance”.

Two Contributory Factors were also identified as:

  • An unserviceable Visual Approach Slope Indicator (VASI) for Runway 26.
  • The decision to make an approach to non-precision runway 26 at night.

One Safety Recommendation was made as a result of the Investigation as follows:

  • that Kabo Air should ensure that flight recording devices (FDR and CVR) installed on all aircraft in its fleet are preserved, maintained, serviceable, and operated in accordance with the provisions of the existing Nigeria Civil Aviation Regulations (Nig. CARs) Parts 7.8.1.3, 7.8.1.4 (a), 8.5.1.24 (b)(c) and 8.14.10.3 (a). [2020-013]

The Final Report of the Investigation was published on 26 November 2020.

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