Semantron 23 Summer 2023

The Boeing 737 Max crisis

weight on the sticks but to no avail. ’ 62 In fact, it is a 103 lbs (46.7 kg) force battle between the cockpit crew and the control column. 63

So, what happened after the first crash? The local preliminary report did suggest the Boeing Company ‘ consider the effect of all possible flight deck alerts and indications on flight crew recognition and response; and incorporate design, flight crew procedures, and/or training requirements. ’ The report also blamed Boeing, saying that ‘ flight crew should have been provided with information and alerts to help them understand the system and know how to resolve potential issues ’. 64

Figure 14: Recorded Flight Data for JT610 (blue: altitude, red: ground speed, green: vertical speed)

2 days before the JT610 flight, on 27 th October 2018, the Captain’s AoA sensor was replaced. Between 27 th October and 29 th October (the day of the crash), the aeroplane had operated 6 flights, and it has been discovered out that 3 out of the 6 flights had AoA problems (JT776, JT2749, JT043). 65 However, none of the pilots reported the problem or had written down the discrepancies observed in flight into the aircraft logbooks. ‘ MCAS does not randomly select which AoA sensors to use, but based on which Flight Control Computer (FCC) is the primary or active unit. ’ 66 In the case of B737 MAX, the left AoA sensor (captain’s side) is wired to FCC1, and the right AoA sensor (the FO’s side) is wired to FCC2. It remains unclear why none of the pilots of the 6 flights reported the problem they encountered in flight. It is also worth mentioning that MCAS will be triggered, only based on one set of AoA data. If the MCAS chooses the faulty AoA data, it will trigger a ‘ false ’ alert and thus, performing the wrong action. Less than 5 months later, on 10 th March 2019, ET302, operated by an Ethiopian Air B737-MAX 8, registered ET-AVJ, 67 took off from Addis Ababa Bole International Airport, bound for Nairobi, Kenya. Unfortunately, it crashed 5 minutes and 3 seconds after take-off. During lift-off, the Left and Right AoA Indicator deviated, fluctuating between a minimum of -11.1° to a maximum of +74.5°. 68 Similar to the previous crash, MCAS was activated at least 4 times. However, the pilots of this flight managed to follow the standard procedure listed on the QRH 69 and the suggested procedure on the AD, 70 i.e. RUNAWAY STABILIZER . As electric trim was now unavailable, the pilots could only use the trim wheel from now on, which is a manual trimming device. 71 After multiple tries from 05:43:10 UTC to 05:43:14 UTC, the 62 Rogers 2020, Fall from the Sky: The Descent of Boeing and the 737 MAX : 22. 63 Komite Nasional Keselamatan Transportasi 2019, Aircraft Accident Investigation Report – PK-LQP : 179. 64 Komite Nasional Keselamatan Transportasi 2019, Aircraft Accident Investigation Report – PK-LQP : 228. 65 Coughlin 2020, Crashing the 737 MAX, Revision 1 : 23. 66 Ibid. 67 Aircraft Accident Investigation Bureau 2019, Aircraft Accident Investigation Preliminary Report – ET-AVJ : 5. 68 Ibid., 10. 69 2009, 737 Quick Reference Handbook : 9.1, 9.14, 9.15.

70 Federal Aviation Administration 2020, Airworthiness Directives AD 2020-24-02 . 71 The Flight Channel 2019, Boeing 737 MAX Crashes Immediately After Takeoff : 17:40.


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