Impact Publications : MICEBTN-73
Page 24 • MICEBTN - September 2019 Not back in the air yet, but Boeing is paddling hard to ensure smooth MAX return by Jack Handley US PLANE maker Boeing hopes that by end October, it will have US approval to return its 737 MAX jets to the skies after their world wide grounding. All 387 of the planes in service were ‘parked’ in March this year following two crashes that killed all 346 passengers and crew. An- other 250 jets manufactured since the grounding are being stored by Boeing. Both crashes - Lion Air Flight 610 in October 2018 and Ethiopian Air- lines Flight 302 in March 2019 -have been linked to flaws in anti-stall flight software known as the Maneu- vering Characteristics Augmenta- tion System (MCAS). MCAS was developed because the new, larger CFM International LEAP-1B engines chosen for the MAX had to be located further forward and higher on the wings than the engines used on earlier 737 types. This affected the jet’s handling characteristics. Put simply, if the ‘angle of attack’ (AoA) air flow/speed sensors on the outside of the jet indicated the plane was attempting to climb too steeply and/or too slowly, MCAS activated and automatically forced the plane’s nose down (into a dive). Unfortunately for Boeing and the passengers and crew on the two crashed jets, in dive mode MCAS was ‘almost physically impossible’ for pilots to correct manually. Boeing’s own engineers probably did not know how difficult it would be for pilots to overpower the acti- vated dive setting during a real-life crisis. And while many pilots claimed not to know MCAS even existed, others believed MCAS used two AoA sensors (one acting as a failsafe if the first malfunctioned) when in reality only one of the two on each jet was active as a default setting. If that one active sensor misfired, as some reports said may have hap- pened as a result of a bird strike in the Ethiopian Air crash, then MCAS could start repeatedly, activating every few seconds. (The Lion Air MAX crash jet suffered what is believed to have been a MCAS malfunction on the day before its fatal accident, but the flight deck crew on that earlier flight were able to switch the sys- tem off - and the jet was repaired after landing safely. The pilots on the same jet’s next outing, Lion Air Flight 610, were not able to disable MCAS when it ‘went rogue’ - or perhaps they did not how to turn it off and didn’t have time to find out. One can only speculate whether the crew on the Ethiopian jet knew there was an ‘off switch’ for MCAS but failed to find it. Following the earlier Lion Air crash, Boeing had is- sued an advisory on how to address erroneous cockpit readings.) Disaster control After the fleet was grounded globally, Boeing went into disaster control mode. Ceo Dennis Muilenburg said the safety systems on its 737 MAX jets were properly designed, but added that Boeing would ‘make them safer’. He also said the pilots did not completely follow Boeing’s proce- dures to prevent the kind of mal- function that probably caused the Ethiopian Airlines crash. He stopped short of saying the crashes were purely pilot error, but his comments encouraged pilots on other airlines to come forward with their own MAX MCAS stories. Those claims in turn gave weight to law suits lodged later by crash victims’ families, Boeing’s own shareholders and its airline custom- ers’ pilots. Later still, the United States Department of Transportation (DoT) ordered an audit into the 2017 regulatory process that led to the aircraft’s initial certification. The audit came after allegations were made that Boeing had (to an extent) been allowed to self-certify the MAX so the MAX would better compete with the (then new) Airbus A320neo. That DoT investigation is ongoing. Adding to Boeing’s troubles, during a set of ‘fixed’ MAX MCAS simulator tests in June, the FAA’s test pilots discovered a separate issue that affected pilots’ ability to quickly and easily follow Boeing’s recovery procedures for runaway stabiliser trim and stabilising the aircraft. Boeing immediately started work on a solution and so far, no other A B737 MAX... its airline customers loved it before the two crashes and most will support its return to service. - Picture Boeing.