The FAA has issued a new airworthiness directive (AD) on the Boeing 737 MAX after Lion Air flight JT610 crash investigators found the aircraft's angle of attack (AOA) sensors are capable of generating erroneous inputs, potentially making the aircraft hard for pilots to control.
"We also plan to conduct a flight reconstruction to see the impact of the AOA sensor damage in the engineering simulator at the Boeing facility in Seattle". Aviation regulators such as the FAA and the European Aviation Safety Agency often follow such actions by mandating that carriers follow the bulletins - something the FAA says it will do in this case.
Lion Air's first two attempts to address the airspeed indicator problem didn't work, and for the Boeing 737 MAX 8 plane's second-to-last flight on October 28, the angle of attack sensors were replaced, Tjahjono said.
Pilots are trained to disengage the angle-of-attack sensors from the plane's computers when they get false readings.
The FAA said the "erroneous inputs can potentially make the horizontal stabilisers repeatedly pitch the nose of the airplane downward, making the aircraft hard to control".
"Both the documents (FAA and Boeing) address erroneous high angle of attack sensor input and corrective action for the same as it has potential for repeated nose-down trim commands of the horizontal stabiliser", said a senior Directorate General of Civil Aviation official, who asked not to be named.
"On November 6, 2018, Boeing issued an Operations Manual Bulletin (OMB) directing operators to existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor", the company's statement said.More news: Trump calls Pelosi to congratulate her on House takeover
Indonesian investigators have recovered the plane's flight data recorder, which showed that the plane's airspeed indicator malfunctioned on its last four flights.
KNKT said that there was a problem with the sensor on the last flight taken by the doomed plane, from the island of Bali to Jakarta, even though one sensor had been replaced in Bali.
The Boeing 737 Max has three such blade-shaped sensors.
That sensor, known as the "angle of attack" sensor, keeps track of the angle of the aircraft nose to help prevent the plane from stalling and diving. The US manufacturer has delivered 219 737 MAX jets to customers globally, according to Boeing's website, and it has 4,564 orders for jets that have yet to be delivered.
The glitch had been repeatedly serviced and Lion Air's technical team declared the plane to be airworthy.
A Lion Air plane carrying 145 passengers was forced to abort its take-off from Indonesia's Bengkulu city on Wednesday night (Nov 7), after its left wing crashed into a pole.
Divers have recovered one of the two "black boxes" - the flight data recorder - but are still searching for the cockpit voice recorder, in the hope it will shed more light on the cause of the disaster. The Boeing bulletin says it is possible that the system will continue to put the aircraft nose down, right up to the limit, unless it is deactivated. Another clue: the so-called angle-of-attack sensor had failed on an earlier flight and had been replaced the previous day.