Preliminary reports by the Accident Investigation Bureau (AIB) on the October 3 plane crash involving the Associated Airline Embraer 120 aircraft Flight 361 at the Murtala Muhammed Airport, Lagos, has linked the incident to the captain's refusal to heed warnings to abort the trip after signs of engine malfunctioning.
This was disclosed by AIB commissioner Captain Muhtar Usman at a press briefing in Abuja yesterday.
After taking journalists round the new flight safety laboratory of AIB where the flight data recorder (FDR) of the ill-fated plane was analysed, Usman said the crew of Flight 361 had discussed some mechanical concerns about the aircraft prior to departure, "but this time we are not prepared to elaborate on those concerns as there remains a lot of work to complete on the cockpit voice recorder (CVR) analysis in order to determine the specific nature of the crew's concerns".
The aircraft bearing the remains of former governor of Ondo State Dr Olusegun Agagu to Akure, the state capital, crashed a few minutes after take-off from the Murtala Muhammed Airport in Lagos. Thirteen of the 20 passengers aboard the plane died at the scene of the accident while two died later in the hospital.
Usman ruled out weather as a factor in the crash. He said that four seconds after engine power was advanced to commence the take-off roll, the crew received an automated warning from the on-board computer voice which consisted of three chimes followed by "take-off flaps... take-off flaps". "This is a configuration warning that suggests that the flaps were not in correct position for take-off and there is some evidence that the crew may have chosen not to use flaps for the take-off."
The agency said that the warning was normal in flight "but this warning continued throughout the take-off roll".
The report further stated that the "set power" call was made by the captain and the "power is set" call was confirmed by the first officer as expected. But three seconds after the call, the first officer observed that the aircraft was moving slowly, he said.
According to him: "Seven seconds after the 'power is set' call, the internal aircraft voice warning system could be heard stating, 'take-off flaps, auto-feather'. In the feather position, the propeller does not produce any thrust. At this time, we can state that the right engine appears to be producing considerably less thrust than the left engine. The left engine was in a fine condition and produced normal thrust.
It added that, at that point of alert, the automated voice continued to repeat "Take-off flaps, auto feather. The standard '80 knots' call was made by the first officer, which indicated that the plane had problems with take-off."
The report noted that the first officer asked the captain if the take-off should be aborted 12 seconds after the call was made. "In response to the first officer's question to abort, the captain indicated that they should continue and they continued the take-off roll. During the rotation, the first officer stated 'gently', which we believe reflects concern that the aircraft is not performing normally and therefore needs to be rotated very gently so as not to aerodynamically stall the aircraft," Usman revealed.
Also, the first officer had expressed worry over the poor climbing by the plane and advised the captain who was flying not to stall the aircraft. "Immediately after lift-off, the aircraft slowly veered off the runway heading to the right and was not climbing properly. This behaviour appears to have resulted in the air traffic controller asking Flight 361 if operation was normal. Flight 361 never responded," the report said.
Less than 10 seconds after the 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 plane finally impacted 31 seconds after the warning which, according to the report, the flight shows characteristics consistent with an aerodynamic stall. The plane nose-dived near 90-degree right bank.
However, some sources at the site of the crash said the pilot turned the plane to return to the airport but one of its wings hit the tank farm before it plunged to the ground, nose first. "Why the captain continued against the advice from his first officer remains a mystery as the dead can't defend one another."
In his closing remarks, the commissioner said AIB was in the process of developing a comprehensive computer reconstruction of the flight which will help the bureau to understand the sequence of events leading to the crash. It added that it has no safety recommendations for now but will not wait for the final report to issue safety recommendations about any issue that requires immediate attention.