Maneuvering Characteristics Augmentation System

rdf:langString Maneuvering Characteristics Augmentation System

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rdf:langString Boeing 737-200 JT8D.jpg

rdf:langString Boeing 737-9 MAX CFM LEAP-1B PAS.jpg

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rdf:langString The Maneuvering Characteristics Augmentation System (MCAS) is a flight stabilizing feature developed by Boeing that became notorious for its role in two fatal accidents of the 737 MAX, which killed all 346 passengers and crew on both flights. A first MCAS design was implemented on the Boeing KC-46 Pegasus military air tanker. The KC-46, which is based on the Boeing 767, requires MCAS because the weight and balance shifts when the tanker redistributes and offloads fuel. It allows pilots to assume control of the aircraft. On the MAX, MCAS was intended to mimic the flight behavior of the previous generation of the series, the Boeing 737 NG. During MAX flight tests, Boeing discovered that the position and larger size of the engines tended to push the nose up during certain maneuvers. Engineers decided to use MCAS to counter that tendency, since major structural redesign would have been prohibitively expensive and time-consuming. Boeing's goal was to have the MAX certified as another 737 version, which would appeal to airlines with the reduced cost of pilot training. The Federal Aviation Administration (FAA) approved Boeing's request to remove a description of MCAS from the aircraft manual, leaving pilots unaware of the system when the airplane entered service in 2017. After the Lion Air crash in 2018, Boeing and the FAA, still not revealing MCAS, referred pilots to a revised checklist procedure that must be performed in case of a malfunction. Boeing then received many requests for more information and revealed the existence of MCAS in another message, and that it could intervene without pilot input. According to Boeing, MCAS was supposed to compensate for an excessive nose up angle by adjusting the horizontal stabilizer before the aircraft would potentially stall. Boeing denied that MCAS was an anti-stall system, and stressed that it was intended to improve the handling of the aircraft. After the Ethiopian Airlines crash in 2019, Ethiopian authorities stated that the procedure did not enable the crew to prevent the accident, which occurred while a fix to MCAS was under development. Boeing admitted MCAS played a role in both accidents, when it acted on false data from a single angle of attack (AoA) sensor. In 2020, the FAA, Transport Canada, and European Union Aviation Safety Agency (EASA) evaluated flight test results with MCAS disabled, and suggested that the MAX might not have needed MCAS to conform to certification standards. Later that year, an FAA Airworthiness Directive approved design changes for each MAX aircraft, which would prevent MCAS activation unless both AoA sensors register similar readings, eliminate MCAS's ability to repeatedly activate, and allow pilots to override the system if necessary. The FAA began requiring all MAX pilots to undergo MCAS-related training in flight simulators by 2021.