One year is fulfilledñor the flight accident Ethiopian 302 operated on a Boeing 737 MAX, it became púI publish a new preliminary report.
After the fatal crash of the Ethiopian flight 302 everything changedó in the industry, especially for Boeing. Hours laterés of this event and for the notable similarities with the accident of the flight of Lion Air spaghettién operated in a 737 MAX, this model of avióno leftó on land.
It is already añor since this accident and the aviation authoritiesón civil de Ethiopía reveló the interim or preliminary report of the progress of the investigationón that has been carried out together with regulatory entities around the world, seeking to reveal the chain of events that led to this situationón.
Ethiopian preliminary report 302 Boeing 737 MAX
In the lengthy document 136 pápages detail the first findings of the investigationón and since it is not a final report toún, no industry recommendations detailed, manufacturer, aerolíne or regulatory entities.
Findings
The report highlights the following points:
- The aircraft hasíto a certificate of airworthiness válicit and in accordance with applicable regulations and procedures;
- There were no problemséknown cynics before departure.
- The weight and balance of the aircraft were within líoperational mites.
- Takeoff and takeoff run were normal, including left and right normal values
of the áangle of attack (AOA). During the takeoff roll, the engines stabilized in about 94% of N1. From this point for most of the flight, the reference N1 remained around the 94%. - Shortly afterés of takeoff, AOA values recorded on the left and right deviated. In the left AOA the values were erróneos and reached 74.5° while in the right AOA it reachedó a value mámaximum of 15.3°. The difference between the left and right AOA values was 59° and remainedó as such until near the end of the recordingón.
- Right afterés of the deviationón del aoa, the left stick shaker activatedó and remainedó active until the end of recordingón. The flying pitch bars (F/D) disappeared on both primary flight screens (PFD).
- Approximately five seconds laterés from the end of the adjustment inputs theéelectric crew manualón, a third automatic adjustmentánose down attic (MCAS) activeó. There was no corresponding
stabilizer movement, which is consistent with the stabilizer cutoff switches being in the positionón of «off». - Sonó the speed and stay clackeró active until the end of recordingón. The speed values varied between 360 kt y 375 kt.
- Approximately five seconds laterés of the úlast adjustment entryémanual electric, quarter
auto adjustáattic nose down (MCAS) activeó. The stabilizer movedó from 2.3 a 1 degrees. Vertical speed decreasedó and turnedó negative 3 seconds laterés of activationóMCAS number. - The difference in trainingón from B737NG to B737 MAX provided by the manufacturer was inadequate.
- AOA's disagreement message did not appearó on the accident aircraftún the designñor described in the operation manualón of the crewóflight number.
- The functionóditchóADIRU AOA failure number not detectedó the AOA erróneo on the left AOA Sensor because it only considers the value to be erróneo when AOA value is out of range.
- He saysño of MCAS on individual AOA inputs made it vulnerable to activationóunwanted n.
- Specific failure modesífics that canían lead to an activationón Unwanted MCAS, as an err entryóAOA lines were not simulated as part of the evaluation tests.ón of functional risks. As a result, various effects occur in flight (such as IAS DISAGREE and ALT DISAGREE alerts and activationón del stick shaker) resulting from the same underlying fault (for instance, AOA errónea) were not simulated or documented in the aircraft manual.
security recommendations
Finally, the document recommends that the system MCAS must obtain informationón of both AOA, so that you get informationón redundant.
Spaghettién mentions that it is necessary to carry out simulator sessions so that the crews that go from NG to MAX become familiar with the normal and abnormal procedure of the MCAS system, for which the training system must be able to simulate AOA failures.
To close, The investigative board recommends that the manufacturer should confirm that the AOA DISAGREE alert operates regardless of whether the AOA DISAGREE indicator áangle of attack whether or not it is installed on aircraft of this type.
