A week after an Indonesian low-priced airline Lion Air plane crashed killing 189 people, another of its aircraft was involved in an incident on Thursday, when it smashed into a pole during takeoff from an airport on Sumatra Island.
It did not give more details and did not speculate on how the indicator problem may have played a role in the crash, as it continues to mine the flight recorder - seen as key to answering why a almost brand new plane fell out of the sky.
Aerospace giant Boeing is preparing to alert pilots of its new 737 Max line of passenger jets warning that inaccurate readings in an onboard flight-monitoring system can cause the planes "to abruptly dive", Bloomberg reported on Tuesday, citing a source with knowledge of the matter.
Indonesian investigators said Wednesday the plane had experienced instrument failures on 4 flights, including on one journey where both the AOA sensor and the airspeed indicator were affected. One of the critical ways a plane determines if a stall is imminent is the angle of attack measurement.
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Chairman Soerjanto Tjahjono said the airspeed indicator and sensor problems were related.
Boeing Co. said on Wednesday it had issued a safety bulletin reminding pilots how to handle erroneous data from a key sensor in the wake of last week's crash in Indonesia.
An angle of attack sensor had been changed by mechanics on the ground in Bali the day before the crash, Indonesia's National Transportation Safety Committee (KNKT) has said. "We think this is an issue that is important because there are more than 200 Max planes around the world", Capt. Nurcahyo Utomo, the transportation safety committee's lead accident investigator, told the Times.
The pilot of the flight requested a return to Denpasar but the situation corrected itself and he elected to continue to Jakarta. When the AOA sensor input to the computer is erroneous, it can result in a trim of the stabilizer to a nose down position in increments lasting up to 10 seconds. But the urgency of a fatal accident can trigger a flurry of such notices. If pilots aren't careful, they can cause severe nose-down trim settings that make it impossible to level a plane. That case didn't involve the angle-of-attack system.
He said the pilot had landed the plane safely on that occasion.