On April 4th, 26th day after the crash of Ethiopian Airlines, the country's regulatory authorities issued a preliminary investigation report. According to this report, the crashed flight ET302 encountered a series of fault alarms after take-off. Although the pilot followed the emergency procedures issued by Boeing and the Federal Aviation Administration (FAA), he still could not control the plane, causing it to dive and crash at high speed.
On April 5th, Boeing admitted for the first time that two accidents in lion air and Ethiopian Airlines were related to the failure of MCAS system, but it still stressed that "historical experience shows that the accidents were caused by a series of factors".
Boeing 737 MAX is equipped with left and right angle of attack sensors. The report shows that about 1 minute after take-off, the deviation of two angle of attack sensors is close to 60. One angle of attack sensor reads 15.3 and the other reads 74.5, which means that the plane is almost pointing to the sky.
After sensing the sensor data failure, the pilot immediately tried to access the autopilot. However, the plane was disconnected after half a minute of automatic driving, and the captain immediately asked the co-pilot to report the control problem of the plane to the air traffic control. In the next four minutes, the black box recorded that the plane had automatically lowered its nose four times. The captain and the co-pilot tried to control the plane to return to normal many times, but the manual operation was invalid.
Boeing 737 MAX is equipped with a new system to prevent the aircraft from stalling, that is, the Maneuverability Enhancement System (hereinafter referred to as MCAS). The main function of the system is to automatically command the horizontal stabilizer (which refers to the horizontal wing surface of the tail of the aircraft and can control the attitude of the aircraft) to make the nose of the aircraft tilt downward when judging that the angle of attack exceeds the limited value. However, Boeing's MCAS is not equipped with enough fault-tolerant mechanism. When the angle-of-attack sensor recognizes the error, MCAS will start automatically without informing the pilot.
FAA: federal aviation administration.
The pilot expert committee appointed by the US aviation regulatory agency reviewed the software repair scheme proposed by Boeing for the grounded 737 Max aircraft, and concluded that once the aircraft resumed use, pilots would not need additional simulator training.
This report of the Federal Aviation Administration (FAA) Flight Standardization Committee is an important first step to review the unfinished upgrade of the 737 Max series aircraft. The report is posted on the FAA website, and the public can comment on it before April 30.
The proposal calls for strengthening the training of the anti-stall system called Maneuvering Augmentation System (MCAS), which is related to two crashes that caused casualties, but does not require simulator training. Simulator training is expensive, and it may also complicate the aircraft recycling service.
Boeing is about to complete the flight test of the upgraded anti-stall software of the 737 Max aircraft involving two fatal air crashes, hoping to end the global grounding dilemma of its best-selling models as soon as possible.
Dennis muilenburg, CEO of the company, said in a video message released on the evening of April 17 that the company had completed the engineering test of the updated software. Next, Boeing will conduct a certification test flight and submit the final written document to the Federal Aviation Administration (FAA).
The accident of Boeing 737MAX attracts worldwide attention, because it is a model that should not go wrong from any angle. The whole 737 series has always been one of Boeing's products with the highest profits and the largest orders, accounting for 1/3 of the company's total profits. The latest 737MAX is Boeing's most technologically advanced aircraft, with more than 370 aircraft sold and 4,700 still in production.
Whether it is Boeing's good reputation or the excellent reputation of the 737 series aircraft, the crash of this star plane looks incredible, a bit like the feeling that the so-called "unsinkable" Titanic hit an iceberg on its maiden voyage.
Then you may ask, aviation accidents happen every year. Why is this 737MAX accident particularly eye-catching?
The Economist said in the article that most of the aviation accidents in the past were caused by improper human operation and had nothing to do with the aircraft manufacturer, but this 737MAX accident was caused by the design problem of the aircraft itself, and the nature of the matter was completely different. Moreover, Boeing aircraft account for half of all civil airliners. Once there is a problem with its products, the scope will be large.
Based on the interpretation information of authoritative media and experts, the possible reasons for Boeing's two crashes are summarized as follows: