On May 12, 2010, Afriqiyah Airways Flight 771 crashed on approach to Tripoli International Airport, killing 103 of the 104 people on board the aircraft.
Coming from Johannesburg, South Africa, Afriqiyah Airways Flight 771 took off from OR Tambo International Airport (JNB) on May 11 at 19:25 UTC, bound for Tripoli, Libya. The nine-month-old Airbus A330-202, registration 5A-ONG, was carrying 11 crew members and 93 passengers.
The flight crew consisted of a captain, a pilot not flying (PNF), a co-pilot who was pilot flying (PF) and a relief co-pilot. The flight was uneventful until the start of the approach to Tripoli airport. The following data comes from the final report of the Libyan Civil Aviation Authority, and all times are in UTC.
Accident investigators often have to examine the wreckage in great detail to find answers. Photo: Getty Images
Why did they ignore their minimums?
At 0329:43, the Tripoli ACC controller identified the aircraft and cleared it to proceed directly to the Tripoli TW locator approach runway 09. At 0358:57, the aircraft was transferred to Tripoli tower with an aircraft at 1200 feet QNH. At 0359:19, the tower advised the aircraft to continue the approach and report the runway in sight, which the crew confirmed.
The flight then received information from a flight ahead that it had noticed patches of fog during the short final. At 0400, the aircraft passed the TW locator beacon at 1000 feet, 200 feet below the prescribed altitude. The captain told ATC he would report when the runway was in sight.
The approach continued below the minimum descent altitude of 620 feet, the runway still not being visible. At 280 feet, the GPWS issued “ground too low” and the captain ordered the co-pilot to go around. The aircraft climbed to 450 feet above ground level, then nosed over at 0400:59.
From 0401:10 to 0401:12, the captain took priority over the flight controls and applied a strong pitch-down input. At 0401:14, the aircraft struck the ground with a ground speed of (260 knots) and a vertical speed of (4400 ft/min) downwards.
The investigation revealed that the accident resulted from a descent below the MDA without the runway in sight, inappropriate flight control inputs during the go-around, and lack of flight path monitoring and control. . The report also indicated that the inappropriate control inputs were typical of a somatogravic perception illusion.
The purpose of investigations is to improve future safety, not to assign blame. Photo: Getty Images
Was the accident caused by an illusion?
A somatogravic illusion is a form of vestibular illusion or false sensation caused by changes in linear acceleration, angular acceleration, and vertical acceleration (gravity), which occur due to changes in flight path. One of the most likely and dangerous situations for this illusion to occur is during a go-around.
Retracting flaps and gears and changing thrust while seeking to maintain a specific climbing flight path involves considerable changes in acceleration. As inputs to establish a sustained climb take effect, a perception of excessive nose-up may occur and raise concern that the stall angle of attack is approaching. The instinctive reaction is to push the nose down thinking that a reduction in pitch towards a more “normal” climb is being achieved.
The report said coordination and cooperation between the pilots was limited and their performance was likely impaired due to fatigue. The degraded CRM prevented either pilot from identifying and recovering from the situation, even when the terrain avoidance warning system was activated near the ground.
How many people have experienced a somatogravic illusion or knew about this effect?
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