The first officer flying the Atlas Air B-767 which crashed near Huston airport may have experienced a nose up sensation of up to 80 degrees nose up before he put the aircraft to a dive. The “apparent” pitch angle that the co-pilot might have “felt” that the airplane was at based solely on vestibular/kinesthetic(body’s balance system in the ear canal) perception from loads acting in the co-pilot’s body coordinate system

On February 23, 2019, at 1239 central standard time, Atlas Air f light 3591, a Boeing 767-375BCF, N1217A, entered a rapid descent from 6,000 ft and impacted a marshy bay area about 40 miles southeast of George Bush Intercontinental Airport (KIAH), Houston, Texas. The two pilots and one non-revenue jump seat pilot were fatally injured. The airplane was destroyed and highly fragmented.

The chain of events was probably triggered by an inadvertent activation of the go-around mode which commanded maximum thrust from the engines and a rapid acceleration. The acceleration may have been perceived as a pitch up. To counter the apparent pitch up, the first officer may have pushed the nose down into a steep dive.

Somatogyral illusion

SI is a false sensation of rotation or absence of rotation. Any discrepancy between the actual and perceived rate of self-rotation. It originates in the inability of the semicircular canals to register accurately prolonged rotation (> 30 s).

Otolyth Organ

The otoliths consist of calcium carbonate ‘stones’ embedded in a gelatinous
substance. When the head moves, the inertia or weight of the stones bends the
hair cells and thus activates nerve cells, sending a signal to the brain
proportional to the amount of head movement.

Inner ear

lThe gravito-inertial acceleration (GIA) is the vector sum of the vector of gravitational acceleration (upward) and all other linear accelerations acting on the head.

lA somatogravic illusion is a false sensation of body tilt that results from perceiving as vertical the direction of non-vertical gravito-inertial acceleration or force.

Prevention

• Prioritize the workload; first, fly the aircraft, then do  everything else
• Build up experience controlling the aircraft in an environment of conflicting orientation cues
• Avoid disorientation by making frequent instrument cross-checks, even when the autopilot is on
• Match the instrument readings with your internal mental representation of the flight path
• Recover from disorientation by
• Making the instruments read right, regardless of your sensation
• Don’t trust your built-in equilibrium organs, particularly in low-visibility conditions
• In moments of stress, make decisions based on the instruments; don’t fall back on your instinct or perceptions

Short calculation

• 1 knot = 0.514 m/s Acceleration after takeoff:
• 30 kts/10s = 1.54 m/s²
• 1 G = 9.81 m/s²
• à acceleration = 0.16 G
• GIA = sqrt(1² + 0.16²) = 1.01 G
• Inclination = Arc Tan(0.16/1) = 9 degrees
• Nose-up impression of 9 degrees