Final investigations into the two crashes that grounded the Boeing 737 Max fleet are still ongoing. A picture has emerged, however, of organisational decision making that was deeply flawed. It was this, rather than a technical malfunction in the Manoeuvering Characteristics Augmentation System (MCAS), that was to prove fatal.
On March 10th, 2019, a Boeing 737 Max operated by Ethiopian Airlines nosedived into the ground 6 minutes after takeoff. On inspection, the disaster was almost identical to an earlier crash involving a Lion Air 737 in Indonesia the previous October. This led to the worldwide grounding of the Boeing 737 Max fleet, a devastating blow to the aircraft manufacturer. The aircraft had only been in service since 2017.
The immediate cause of both crashes appeared to be a mistaken activation of the MCAS on the basis of false Angle of Attack (AoA) sensor inputs. These told the MCAS that the aircraft was in danger of stalling and initiated a corrective action on the part of the aircraft's stabilisers. It was this that sent the aircraft into a dive.
There is no denying that a technical malfunction of the AoA sensors played an important role in the crashes by triggering a nosedive. Nevertheless, the pilots should have been able to recover the aircraft manually, but were not. For an explanation of why they were not able to do so, we need to shift our attention away from technical components towards the organisational decision making that put the pilots in an impossible situation.
The 737 Max was a response by Boeing to competition from Airbus, its major rival. Under pressure from the A320, Boeing took the decision to re-engine its 737, abandoning its previous intention to build an entirely new design as a replacement. This it did, however the new engines affected the aircraft's centre of gravity, shifting it forwards, and therefore increasing the risk of a stall when the aircraft was under heavy load or in a turn.
The MCAS was the solution to this threat. This was an automated system that responded to sensors by adjusting the rear stabiliser, without any pilot intervention. It was here that the difficulties began.
A major challenge for the 737 Max rollout lay in the extent of pilot training that would be required. Boeing sought to minimise this as the cost would prohibit sales among operators of the older version of the 737. One pilot stated (see here) that transition training from the NG "consisted of little more than a one-hour session on an iPad." There was also a fear that the introduction of the MCAS would meet resistance from the pilots union. This was one reason why an automated system was preferred. According to this media report, the pilots and their union were not even informed that the new system existed. Nor was it included in the Flight Crew Operations Manual issued to operators such as Southwest Airlines (see here).
Pilots did retain the possibility of overriding the MCAS, by using the manual trim wheel. Unfortunately, the operation of the horizontal stabiliser by the MCAS interfered with the counter action of the trim mechanism. Not only that, but the MCAS functioned in a step manner, reactivating every five seconds for so long as sensors told it the AoA was too high, no less than 26 times in the case of Lion Air. It was here that the lack of information sharing took on its significance, as the pilots had no idea what was causing the aircraft to dive, nor why their corrective actions were having no effect.
For operators, the lack of information about the MCAS influenced their decision making in one important respect. An additional AoA indicator fed into the pilots' main display was available as an optional extra, and would have alerted pilots to the problem with the sensors, but without an understanding as to why this was needed, there seemed no good reason to take on the extra cost. There is good reason to believe this would have made all the difference, in the case of Lion Air for example, the aircraft would probably not have taken off as the AoA sensors were already malfunctioning.
In the last few days, more revelations have come to light of organisational failures leading up to the two crashes. It now appears that Being test pilots became aware of problems with the MCAS and discussed this among themselves, however this information was lost inside the development team who were under pressure to get the aircraft certified and operational. The FAA is still looking into this aspect of the overall picture (see here)
The ability of critical information to reach the person within a team who needs it most is one of the performance metrics covered in Avoiding Catastrophe and T3's Team Processes training program. Organisational decision making is a key component within the HCD program. Both would have been highly relevant to the situation emerging as the 737 Max was being rolled out during 2017 and 2018.
If you would like to discuss these issues, or how HCD and T3 training might be helpful in your context, then please contact us at editor@avoidingcatastrophe.com
For more coverage of the Boeing 737 Max crisis, go to Air Current Magazine here