A preliminary report released Friday by the Accident Investigation and Prevention Bureau (AIPB) has revealed that penultimate Thursday's plane crash in Lagos was caused by engine failure and human error.
This was disclosed yesterday in Abuja by the AIPB Commissioner Capt. Mukthar Usman while presenting the report to newsmen.
The report indicated that the voice recorder which captured the conversation among crew members at the onset of the flight revealed that they were worried about the condition of the plane.
The report also stated that during the short period the flight lasted, the right engine of the aircraft produced less thrust than the left engine.
According to the four paged report: " The crew expressed some concerns about the aircraft prior to departure but at this time we are not prepared to elaborate on those concerns as there remains a lot of work to complete on cockpit voice recorder analysis in order to determine the specific nature of the crew's concerns".
The report further revealed that approximately four seconds after engine power was raised for take off roll, " the crew received an automated warning from the on-board computer voice which consisted of three chimes followed by announcement of " take off flaps, take off flaps".
Captain Usman disclosed that the crew ignored this first warning.
The document further showed that a short while later, the co-pilot (First officer) in the aircraft complained that the plane was moving slowly and suggested that the flight should be aborted.
According to the report: "Approximately seven seconds after the 'set power' call was made by the captain and confirmed by the co-pilot, the internal aircraft voice warning system could be heard stating "take off flaps, take off flaps, auto feather".
Captain Usman explained that this meant that the propellers of the aircraft were not producing enough thrust required for the take-off of the aircraft."
According to Captain Usman: "In response to the First Officer's question on whether the flight should be aborted, the Captain decided that the take-off roll should continue and they continued".
The report further revealed that the First Officer complained once again that since the aircraft was not climbing, the Captain should not stall the aircraft in order to avoid danger.
The AIPB Commissioner explained that "if the aircraft was not producing enough overall thrust, it is difficult for the aircraft to climb without the risk of an 'aerodynamic stall'."
Said he: "Immediately after lift-off, the aircraft slowly veered off the runway heading to the right and was not properly climbing. This aircraft behaviour appeared to have resulted in the air traffic controller asking the crew whether the plane's operation was normal but they never responded"
According to Capt. Usman: " The physical examination of the wreckage revealed that the right engine propeller was in the feather position and the engine fire system was activated."
He continued: " Less than 10 seconds after rotation of the aircraft to climb away from the runway, the stall warning sounded in the cockpit and continued to the end of the recording.
The flight data showed characteristics consistent with an aerodynamic stall. 31 seconds after the stall warning was heard, the aircraft crashed onto the ground with its nose almost at an angle of 90 degrees".
The AIPB Commissioner further stated that : " The investigation was focusing on the following:Mechanical and electronic engine control issues related to the right engine and right engine propeller systems; warnings related to the auto-feather and the flap settings required for take-off; take off configuration issues with respect to flap settings; crew decision making and training with respect to proceeding with the flight despite the concerns regarding the aircraft's suitability for the flight; when and how the second engine's fire system was activated; standard operating procedures with respect to continuing the take-off roll despite continuous automated voice warnings of both 'take-off flaps' and 'auto feather' when there was ample time to abort the flight take off and the safety culture prevailing among the staff of the airline".
Captain Usman explained that the AIPB was in the process of developing a comprehensive computer reconstruction of the flight "which would help our team understand the sequence of events and will ultimately help us communicate our findings to the aviation community and the general public."
He further stated that AIPB had no fresh safety recommendations to make for now but reassured the public that it would do so if the need arises in the course of its investigation of the accident.
Throwing more light on the authenticity of the report which emanated from the newly completed laboratory of the aviation parastatal, Captain Usman stated that "International flight recorder experts from Canada who designed the laboratory assisted the investigation team with the read out and analysis process along with representatives from the aircraft manufacturer and aircraft operator."
According to him, the investigation was conducted in accordance with Annex 13 of the International Civil Aviation Organisation's (ICAO) rules.
Said he: " The cockpit voice recorder contained 32 and half minutes of audio which included the internal conversation of the two pilots, radio calls and the overall environment in the cockpit."
He also said the flight data recorder (FDR) contained 47 hours of data which captured all that happened to the aircraft's operations throughout the short period of the flight.