Lion Air crash: Boeing didn’t reveal key info

Cornelia Mascio
Novembre 14, 2018

The U.S. aviation regulator has launched a high-priority probe of the safety analyses performed over the years by Boeing Co, following the crash of a Lion Air jet in Indonesia last month, the Wall Street Journal reported on Tuesday.

Citing "safety experts involved in the investigation, as well as mid-level FAA officials and airline pilots", the Journal reported Monday that the automated stall-prevention system on Boeing 737 MAX 8 and MAX 9 models - meant to help cockpit crews avoid mistakenly raising a plane's nose dangerously high - "under unusual conditions can push it down unexpectedly and so strongly that flight crews can't pull it back up".

The automated system is created to help pilots avoid raising the plane's nose too high, which can cause the plane to stall, or lose the aerodynamic lift needed to keep flying.

Preliminary findings from investigators looking into the October 29 crash of the Lion Air 737 MAX 8 suggest that faulty angle-of-attack data contributed to the drastic ups and downs that preceded the loss of the plane and all 189 people who were aboard.

"It is something we did not have before in any of our training".

Aviation Week said it verified that the MCAS system wasn't covered in the operations manual or in the supplemental training materials provided to pilots coming over to the 737 MAX from the previous generation of 737s. The FAA on November 7 issued an emergency airworthiness directive ordering US airlines to incorporate information about the feature in their pilot manuals.

The new flight-control systems "automatically put the nose down to keep the plane from stalling", Mary Schiavo, an airline lawyer and former inspector general of the US Transportation Department, said in an email.

Boeing Chairman and CEO Dennis Muilenburg said Tuesday that the Chicago-based company remains confident the MAX is a safe airplane.

"We did not know this was on the [Boeing 737] MAX models", Weaks said in a Tuesday (Wednesday NZ time) interview, referring to a new automated flight control feature created to prevent the plane from stalling by automatically nudging its nose downward in response to externally collected flight data. An American spokesman said the airline was unaware of some new automated functions in the MAX but hasn't experienced nose-direction errors.

Boeing and the FAA last week issued directives to airlines to alert their pilots that they can resolve such a problem using an existing emergency procedure.

When Boeing designed its latest version of the 737, it added the new safety feature to combat a loss of lift, which is a leading contributor to the loss-of-control accidents that by far cause the most crash deaths around the world.

Last week, investigators working on the Lion Air Flight 610 crash - in which 189 people died - said a sensor on board the aircraft had been replaced the day before the incident, but problems persisted.

The brand new Boeing 737 went down just minutes after take-off from Jakarta on Monday, killing all 189 people on board.

Pilots could stop this automated response by pressing two buttons if the system behaved unexpectedly, but questions have been raised about how well prepared they were for such an automatic reaction and how much time they had to respond.

Indonesian investigators say that the Lion Air Boeing 737 MAX 8 experienced malfunctions with sensors that indicate the angle of the nose on four recent flights, including the fatal one. They are also questioning whether the FAA and Boeing adequately analyzed potential hazards if the systems malfunction and send faulty data to the plane's computers, according to the newspaper.

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