The agency also said that preliminary investigation indicated that the captain-in-command of the ill-fated aircraft,
Abdulrahman Yakubu, ignored the warning from the onboard computer voice.
This was disclosed to journalists by the Commissioner for AIB, Capt. Usman Muktar, while reading out the preliminary readout and analysis of flight 361’s flight recorders in Abuja yesterday.
He said the investigation was done in AIB laboratory in Abuja in conjunction with international flight recorder experts from Canada, who designed the laboratory.
Capt. Mukthar said the Flight Data Recorder (FDR) contained approximately 47 hours in solid state memory, while the Cockpit Voice Recorder (CVR) contained thirty-two and a half minutes of audio, which included internal conversation of two pilots, radio calls, and the overall environment in the cockpit.
Muktar said that Associated Airlines flight 361 was cleared for take-off by the Air Traffic Controller on runway 18 left of the Murtala Muhammed Airport (MMA) Lagos, adding that at that time, the wind was calm and weather was not considered a factor in the accident.
He added that four seconds after the engine power was advanced to commence take off roll, the crew received an automated warning from the onboard computer voice which consisted of three chimes followed by “Take off Flap, Take off Flap, Take off flap.”
He stated that this configuration warning suggested that the flaps were not in the correct position for take-off and there was evidence that the crew might have chosen not to use flaps for the take-off.
According to him, “This warning did not appear to come as any surprise to the crew, and they continued normally with the take-off. This warning continues throughout the take-off roll.“
Capt. Mukhtar added that AIB was in the process of verifying the accuracy of the flight data, adding that the agency had not been able to confirm the actual flap setting and that AIB was expected to determine this in the fullness of time.
The AIB commissioner added that the ‘set power’ call was made by the captain and the ‘power is set’ was confirmed by the First Officer as expected in the normal operations, adding that approximately three seconds after the ‘power is set’ call, the First Officer noted that the aircraft was moving slowly.
Approximately seven seconds after the ‘power is set‘ call, the internal aircraft voice warning system could be heard stating ‘Take off Flap, Auto Feather’.
He explained that auto feather refers to the pitch of the propeller blades, adding that in the feather position, the propeller does not produce any thrust.
The Flight Data Recorder, he said, contains several engine related parameters, which the AIB was studying.
“At this time, we can state that the right engine appears to be producing considerably less thrust than the left engine. The left engine appeared to be working normally. The aircraft automated voice continued to repeat, Take off Flap, Auto Feather.’ “
According to an aircraft engineer, Sheri Kyari, the flap on an aircraft is located at the trailing edge of the wing. It is at the rear end of the wings.
Kyari, a former president of Pilots and Aircraft Engineers in the defunct Nigeria Airways Limited, the function of the flap when operational increases the surface area of the wing, thereby generating enough lift at low aircraft speeds. This is when the aircraft is taking off or landing.
Kyari, is convener and executive director, Centre of Aviation Safety and Research.
“When the flap is not set to the required degree for take off, the aircraft will have to do a long take-off run before gaining enough lift to lift-off the ground,” he said.
Reading out the preliminary report, AIB said “the standard ‘eighty knots’ call was made by the First Officer. The first evidence that the crew indicated that there was a problem with the take-off roll was immediately following the ‘eighty knots’ call.
“The First Officer asked if the take-off should be aborted approximately 12 seconds after the ‘eighty knots’ callout”
AIB added that the captain, in response to the Flight Officer’s question to abort the take off, said that they should continue, adding that the crew did not make V1 call, which is the speed at which the decision to abort or continue a take-off is made, or the Vr call, which indicates the speed at which it is planned to rotate the aircraft.
The Commissioner added that normally, the non-flying pilot pulls back both the V1 and the Vr speeds,
He said that when the Vr was called, the flying pilot pulled back the control column. The First Officer asked the Captain ‘gently’, a word that indicated that the aircraft was not performing normally.
He added that the aircraft did not produce enough overall thrust and that it was difficult or impossible to climb without risk of an aerodynamics stall.
An aviation expert, Mallam Muhammadu Dodo, described aerodynamics as the streamline of air flow around the aircraft due to its design. It enables it to attain a stable and safe flight.
Immediately after lift-off, the aircraft slowly veered off the runway, heading to the right and was not climbing, and that the aircraft behaviour made ATC to ask the pilot if Flight 361 operation was normal but that they did not respond, and that 31 seconds after the warning, the aircraft crashed.
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