Ice buildup caused a serious incident on a flight of the now-defunct Trip Linhas Aéreas in 2013, causing the crew to lose control of the plane. The aircraft was an ATR 72-212A, registration PP-PTU, a model similar to the Voepass that crashed last Friday (9) in Vinhedo (SP).
According to a report from the Aeronautical Accident Investigation and Prevention Center (Cenipa), the incident occurred at approximately 7:00 p.m. on July 26, 2013. The plane was flying between Maceió (AL) and Salvador (BA). There were 62 people on board (58 passengers and four crew members). No one was injured and there was no damage to the aircraft.
The report indicates that the plane was flying at an attitude of 16,000 feet (equivalent to just over 4,800 meters) with the system de-ice disabled. This mechanism is used to remove ice that has formed and accumulated on the aircraft structure. “There has been degradation in its performance”, leading to a reduction in the indicated speed.
“After severe vibration, the crew reduced the power of both engines to 20% torque, causing the speed to drop to 10 kt [pouco mais de 18 km/h] below the minimum speed in icing conditions. The pilot took manual control and the angle of attack increased considerably, causing the stall protection systems to activate [perda de sustentação]”, says the Cenipa document.
The report adds that “the co-pilot requested immediate descent to APP-SV [Controle de Aproximação de Salvador]being authorized to descend to 2,000 ft [cerca de 600 metros]. Upon comparing the information, the co-pilot declared a mayday condition.”
The aircraft’s black box indicates that the aircraft had “a rapid change in speed followed by a loss of 5,000 ft [cerca de 1.500 metros] of altitude”.
The emergency situation lasted just over a minute. At around 7:01 p.m. and 30 seconds, “the vibration ceased and the crew regained control and management of the flight,” says Cenipa.
Salvador Approach Control was informed by the commander about the normalization of flight conditions and the landing was made normally in the capital of Bahia.
Investigation conclusions
An analysis carried out by Cenipa technicians as part of the investigation into the incident involving the Trip Linhas Aéreas ATR indicates possible errors by the crew when dealing with the ice build-up. The names of the pilot and co-pilot who operated the flight have not been released.
“According to the CVR audio [gravador de voz da caixa-preta]it was found that the crew noticed the presence of ice accretion. However, the engine, wing and fuselage de-icing systems were not activated, as provided for in the flight manual.”
The report states that, during the flight, the aircraft showed signs that it could be experiencing problems related to ice, such as:
- “Water splashing and running down the windshield”;
- “Ice extensively accumulated in areas of the structure where it would not normally be observed”;
- “Ice accumulation on the forward part of the lower surface of the wing in protected areas”; and
- “Ice buildup on propeller spinner, further forward than normally observed”
“Although ice accretion conditions [acúmulo de gelo] “Although the conditions were identified, there was no adequate perception of how such conditions could affect the air operation. This fact indicated a reduced level of situational awareness, which favored the crew maintaining the flight in unfavorable conditions and failing to apply the corrective actions planned for managing the situation”, says the report.
“In addition, it was found that the crew had doubts about the correct adjustment of the range and angle of the aircraft’s weather radar antenna. Its correct use could have helped the crew avoid the “heaviest” weather formations,” he adds.
The document points to the absence of a mechanism in the speedometer that “was intended to indicate the minimum speed for flight in severe icing conditions to the aircraft commander.” This problem “may have contributed to the commander not realizing that the speed was gradually approaching the minimum limit for flight in those conditions.”
“The crew did not apply the stall recovery procedure, as provided for in the manual”, says Cenipa.
The report states that shortly before the incident, in January 2013, another ATR from the same company had experienced a problem with “strong vibration in the propellers.” “The crew considered that this condition was the same abnormality and, therefore, attempted to shut down the engines.”
“It is possible that awareness of a previous issue with another airline aircraft influenced the crew’s decision-making process and impaired recognition of the aircraft’s low energy level.”
Cenipa points out that “it was found that there was inefficiency in the use of human resources available for the operation of the aircraft, due to inadequate management of the tasks assigned to each crew member due to confusion in communication, given the mistaken interpretation regarding the need to cut the engines during the occurrence”.
“During the flight, there was an inaccurate perception of the impact of ice accretion conditions on the air operation, which led to the crew
maintained the flight in unfavorable conditions and did not notice the stall occurrence [perda de sustentação] caused by the accumulation of ice.”
According to Cenipa, “there was an inadequate assessment of the factors that impacted the aircraft’s performance, which hindered the recognition of the severe icing condition and resulted in the adoption of erroneous measures to manage that adverse situation”.
Recommendations and measures
To prevent other incidents of this type from occurring, the report recommended that the National Civil Aviation Agency (Anac) act “with ATR aircraft operators to ensure that theoretical, simulated and practical training is sufficient for crews to acquire the knowledge and develop the skills necessary to recognize and perform appropriate actions on a flight under icing conditions.”
The Cenipa document states that, after the serious incident, Trip Linhas Aéreas “issued a warning to crew members about the need to be aware of the aircraft’s flight parameters and to strictly follow the procedures established in the event of ice accretion.” The company informed Anac that “the pilots’ periodic training was reformulated, with greater emphasis being placed on managing flights in conditions of ice formation on the aircraft.”
Regarding the equipment manufacturer, the report says that “ATR procedures associated with the icing condition, including normal and emergency AFM procedures (severe icing and icing condition operation) have been extensively reworked.”
“With the input of different experts and based on in-service experience, ATR identified areas for improvement in terms of writing, formatting and presentation to facilitate crew decision-making and the retrieval of essential information during the flight,” concludes the Cenipa document.
Voepass accident
On August 9, 2024, a Voepass ATR 72-500 crashed in Vinhedo (SP), killing all 62 people on board (58 passengers and four crew members).
The plane was flight 2283, which took off from Cascavel (PR) and was headed for Guarulhos Airport (SP). The crash occurred about an hour and a half after takeoff.
One possibility being investigated is that the Voepass turboprop lost control due to ice accumulating on the wings.
Accident in Vinhedo (SP) is the 5th worst in history involving ATR 72
Source: CNN Brasil
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