US emergency directive after Boeing jet crash in Indonesia

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Indonesian crash investigators have confirmed the 737 in the crash had technical faults on four flights previous to the one in which it plummeted into the sea shortly after take-off from Jakarta.

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.

A statement and copy of the new directive obtained by Avionics International notes that the agency is issuing an emergency AD requiring a Boeing 737 MAX flight operations manual update.

The airworthiness directive covers all 737-8 and 737-9 aircraft and is similar to a service bulletin issued by Boeing, after the manufacturer conducted an analysis in the wake of the fatal Lion Air crash on October 29.

These included erroneous speed and altitude data that prompted a flight operated the day before the crash to go into a dive that frightened passengers and a made them sick. Its flight crew had requested permission to return to the airport several minutes after taking off.


"The point is that after the AOA [sensor] is replaced the problem is not solved, but the problem might even increase".

Attempts to fix the issues were unsuccessful, NTSC chairman Soerjanto Tjahjono has said, with the pilots of the 737's second-to-last flight experiencing conflicting information despite an AOA sensor being replaced.

Airline safety experts said pilots are trained to handle a plane safely if those crucial sensors fail and backup systems are generally in place as well.

There are audio signals and physical warnings that can alert the pilot to malfunctioning equipment or other dangers, said Todd Curtis, director of the Airsafe.com Foundation. FDR data resulted in investigators determining that if an erroneously high single AOA sensor input is received from the aircraft's flight control system, there is a potential for the 737 to repeatedly perform nose-down trim commands of its horizontal stabilizer.

"On November 6 2018, Boeing issued an operations manual bulletin (OMB) directing operators to existing flightcrew procedures to address circumstances where there is erroneous input from an AOA sensor".


The DGCA official said if the condition is not addressed, it could cause the flight crew to have difficulty in controlling the airplane.

"The draft of what will be conveyed by Boeing this morning has been presented to us", said air accident investigator Nurcahyo Utomo.

The 737 Max, the fastest-selling plane in Boeing history, is the latest version of the company's 737 family of jets.

Wednesday night's incident involving Indonesian low- cost airline Lion Air comes as the authorities extend search efforts till Saturday for victims' bodies and a second black box from the downed Flight JT610.

The bulletin is based on preliminary findings from the Lion Air disaster, a person familiar with the matter earlier told Bloomberg. All 189 people on board the flight were killed.


Lion Air is one of Indonesia's youngest airlines but has grown rapidly, flying to dozens of domestic and global destinations.

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