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B735, Jos Nigeria, 2010

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Summary
On 24 August 2010, a Boeing 737-500 made an uncontrolled touchdown on a wet runway at Jos in daylight after the approach was continued despite not being stabilised. A lateral runway excursion onto the grass occurred before the aircraft regained the runway centreline and stopped two-thirds of the way along the 3000 metre-long runway. Substantial damage was caused to the aircraft but none of the occupants were injured. The aircraft commander was the Operator's 737 Fleet Captain and the Investigation concluded that the length of time he had been on duty had led to fatigue which had impaired his performance.
Event Details
When August 2010
Actual or Potential
Event Type
Ground Operations, Human Factors, Runway Excursion
Day/Night Day
Flight Conditions VMC
Flight Details
Aircraft BOEING 737-500
Operator Aero Contractors (Nigeria)
Domicile Nigeria
Type of Flight Public Transport (Passenger)
Origin Lagos/Murtala Muhammed International Airport
Intended Destination Jos/Yakubu Gowon Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed No
Flight Phase Landing
LDG
Location - Airport
Airport Jos/Yakubu Gowon Airport
General
Tag(s) Approach not stabilised,
Non Precision Approach,
Inadequate Aircraft Operator Procedures,
Inadequate Airport Procedures,
Approach Unstabilsed at Gate-no GA
HF
Tag(s) Fatigue,
Inappropriate crew response - skills deficiency,
Ineffective Monitoring,
Manual Handling,
Plan Continuation Bias,
Procedural non compliance,
Stress
GND
Tag(s) Surface Friction
RE
Tag(s) Overrun on Landing,
Directional Control
Outcome
Damage or injury Yes
Aircraft damage Major
Non-aircraft damage Yes
Causal Factor Group(s)
Group(s) Aircraft Operation
Safety Recommendation(s)
Group(s) Aircraft Operation
Investigation Type
Type Independent

Description

On 24 August 2010, a Boeing 737-500 (5N-BLE) being operated by Aero Contractors Nigeria on a scheduled domestic passenger flight (210) from Lagos to Jos made an uncontrolled touchdown at destination after a daylight non-precision approach had become unstabilised and remained so after the visual reference transition to land. The aircraft departed the side of the runway onto the grass before regaining the centreline and stopping. Damage to the aircraft was substantial but there were no occupant injuries. Three runway light assemblies and some armoured electrical cables were also damaged.

Investigation

An Investigation was carried out by the Nigerian Accident Investigation Bureau (AIB) aided by successful download of Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) data undertaken by the UK AAIB.

It was established that the 25 year-old First Officer had been designated as PF for the accident flight and that the 53 year-old aircraft commander was the aircraft operator's Boeing 737 Fleet Captain. He was also a Training Captain, although he had not been operating in the latter capacity on the accident flight.

The flight was uneventful until the off-set VHF Omnidirectional Radio Range (VOR)/Distance Measuring Equipment (DME) approach to runway 28 at Jos was under way. The only available Instrument Landing System (ILS) approach - to runway 10 - was not available due to unservisability. A thunderstorm with heavy rain had been affecting the airport shortly before the aircraft began the approach and although the rain had stopped, the most recent Meteorological Terminal Air Report (METAR) timed about 40 minutes earlier was still giving BKN cloud just below 500 feet aal (compared to the 600 feet MDH for the approach being flown) and a prevailing visibility of 2500 metres (compared to the 2800 metres increased minimum with no approach lighting).

It was found that the approach had been unstable at the specified 1000ft aal 'gate' but that instead of the mandatory go-around being flown, the approach had been continued. When the TWR controller sighted the aircraft at about 1nm from touchdown they reported that it was "struggling to align to the centreline of the runway". The initial touchdown occurred on the right hand MLG just 135m metres from the threshold of the 3000 metre-long runway with the right engine cowling touching the pavement. The aircraft then "skidded off the runway to the left into the grass area" at speed before re-aligning parallel to the runway. The right hand engine "ingested foreign objects that resulted in fan blade damage" Three runway edge lights and armoured electrical cabling were damaged before the aircraft regained the runway centreline and came to a stop with 1000 metres of runway remaining. In addition to the engine damage, the NLG shock strut collapsed and both NLG tyres burst and there was some ground contact damage to the lower fuselage. Although no fire occurred, the Investigation considered that "there was a risk of fire", no emergency evacuation was accomplished. However, as it was impossible to taxi the damaged aircraft, the commander subsequently requested steps to disembark the passengers.

The Investigation found that "the unstabilised approach led to the Captain attempting to make necessary corrections with inappropriate procedure" whereas "proper control" of the aircraft was lost and this resulted in the runway excursion. It was noted that good airmanship requires that, with a co-pilot as PF, "if a deviation from the extended runway centreline occurs, the Captain should either take control of the aircraft early enough with a standard callout" or make call for a “go-around”.

The Investigation also found evidence of confusion during the touchdown "precipitated by lack of adequate communication and insufficient standard call-outs". During touchdown, the crew comment “I wanted to go-around; I thought you were the one flying”, was considered to indicate that neither the Captain nor the First Officer had been in control of the aircraft.

It was also concluded that, based on the CVR data, the flight crew "did not adequately make reference to checklists in the approach phase of the flight" and that they "did not brief or execute a missed approach when it became obvious that the aircraft was unstabilised".

It was established that the commander, who had already operated three line training sectors after coming on duty at about 0630 that morning some 11 hours prior to the accident, had not been expecting to operate the accident flight and was "hoping to go home". He had only opted to take the flight when the rostered Captain became unavailable down route and the standby Captain advised that they were "indisposed". It was concluded that, as the B737 Fleet Captain and as management staff of the airline, he had had "the option to cancel the flight if he so wished" but that there had been "an element of organisational pressure (on him) to operate the flight, which he had accepted". It was considered that the Captain had been tired prior to the accident flight and noted that "this was confirmed during the course discussions with the First Officer before the flight". It was further considered that a 90 minute wait for refuelling had "added to anxiety and further tiredness" especially as operations at Jos were limited to the period between sunrise and sunset.

The Investigation found that a lighting fault affecting both approach and runway lighting had been regularly reported during the weeks leading up to the accident but "nothing was done to rectify the issue". It was also noted that the ILS on runway 10 had been unserviceable for three months. Both systems were returned to service "shortly after the accident", in the case of the ILS within 24 hours of the accident.

Although runway friction level was not considered to have been a factor in the accident, the Investigation found that the runway was "contaminated with rubberised deposits at the touchdown zones" and noted with concern that "evaluation of runway friction level has never been carried out" by the responsible agency - the Federal Airports Authority of Nigeria.

The formally stated Cause of the Accident was: "the decision of the crew to continue the approach in an unstabilised condition, coupled with the Captain's inappropriate attempt to take over control of the aircraft".

Three Contributory Factors were also identified:

  • Fatigue, which impaired the Captain’s performance and reflected the effects of a long, demanding duty day associated with earlier duties as a Training Captain.
  • The prevailing weather condition.

Two Safety Recommendations were made as a result of the Investigation as follows:

  • that Aero Contractors Nigeria should review its Safety Management System making all safety critical staff aware of their responsibility to alert the system whenever signs of stress, fatigue or disordered behaviours are noticed in any operating flight crew members.
  • that Aero Contractors Nigeria should re-emphasise adherence to safety and company operating procedures by flight crew members and for captains to take over control of the aircraft promptly whenever critical operational deviations are noticed during flight in adverse weather conditions.

The Final Report was released on 21 May 2015.

Further Reading