An air tragedy occurred in the city of Vinhedo, in the interior of São Paulo, this Friday (10), resulting in the crash of a Voepass ATR-72 plane and the death of 61 people (57 passengers and four crew members). Authorities and experts are investigating the causes of the accident, which should still take some time to be concluded.
While official information is yet to arrive, two hypotheses have gained prominence among experts: the aircraft stalled — a phenomenon characterized by loss of lift — and the accumulation of ice on the wings. Both situations are directly linked to the adverse atmospheric conditions that prevailed in the region at the time of the accident, and have the potential to cause the plane to abruptly lose lift, leading to a fatal crash.
The Vinhedo (SP) plane crash
An ATR-72-500 plane crashed in the city of Vinhedo (SP) while traveling from Cascavel (PR) to Guarulhos (SP); At 11:52 a.m., the plane showed its first failure, when its speed dropped sharply: from 529 km/h, it dropped to 398 km/h in just 30 seconds. The failure repeated itself at 1:20 p.m. Experts report that this could mean a problem with the fuel flow; The aircraft was at an altitude of 5,242 m, an altitude that can cause ice to form on aircraft, which have a de-icing system; It plummeted almost four thousand meters in just two minutes. The plane was at an altitude of 17 thousand feet and at four thousand at 1:22 p.m., when the flight tracking tool lost the aircraft’s GPS signal; As the videos show, the plane fell into a “flat spin”; When it hit the ground, it exploded, killing everyone on board; The process of cooling the wreckage ended early Friday evening (9), allowing for the start of forensic work and the rescue of the bodies.
Voepass ATR-72 flies over the city of Vinhedo (SP). An aircraft of the same model and airline crashed in the region. (Image: Miguel Lagoa / Shutterstock.com)
What is stall?
“The general idea is that there really was a possible stall,” flight safety expert Roberto Peterka told Olhar Digital. “A stall is when the plane loses lift and sinks. And why does it lose lift? It loses lift due to a reduction in speed. Its speed drops below that needed to maintain lift on the wings.”
For an airplane to stay in the air, the wings play a fundamental role in providing lift. They are designed with specific aerodynamics that allow for a difference in air speed between the top and bottom of the wing.
The upper part is curved, while the lower part is practically straight. This difference in speed generates a difference in pressure, pushing the wing upwards, which provides the lift necessary for flight.
There are several situations that can cause an aircraft to stall. One of them is when the aircraft’s inclination exceeds the maximum limit, making it difficult for air to circulate over the top of the wing.
Loss of lift for the flight may have led to the biggest aviation tragedy on Brazilian soil since 2007. (Image: Skatty / Shutterstock.com)
In this case, the air mainly hits the front of the wing, which increases drag and requires more force to maintain flight. In addition, the significant reduction in speed can also contribute to the loss of lift, since the airflow over the wing becomes insufficient.
In small aircraft, the approach of a stall can be warned by an audible signal, similar to a horn. In commercial aircraft, the system usually emits a vibration in the control stick, alerting pilots of the imminent risk.
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Ice buildup on wings
Peterka stressed that ice itself is not a threat to aviation, but rather “the formation or accumulation of ice, for example, on the leading edge of the wing.” He continued: “If you start to build up ice, it will displace where the air molecules hit and it will go over the wing or under the wing and will not provide lift, and it will also create a shadow on the back of the wing where the flight controls are.”
The expert highlights that, as the plane was certified to fly, it must have had equipment to eliminate accumulated ice.
As (the ice) accumulates, (the plane) either turns on the electrical equipment that heats the entire leading edge or there is another pneumatic system that runs inside the wing and breaks the ice to return the wing to being an airfoil as it is designed to provide lift.
Roberto Peterka, flight safety expert
The area where the accident occurred was under alert for “severe icing.” When ice builds up on the wings, it can change their curvature, which compromises the aircraft’s lift.
If the camber of the wings is altered significantly, the aircraft can lose lift completely, resulting in a steep fall, similar to a falling rock, as seen in today’s accident.
