Boeing issues operational manual to airlines following Lion Air crash

Thursday, 08 Nov, 2018

The families have been asking why the plane, a two-month-old Boeing 737 MAX 8, was given flight clearance at all, given that it had reported technical issues the day before, on a flight from Bali to Jakarta, wherein it descended rapidly right after take-off, much to the terror of passengers on board.

In a statement released late Tuesday night, Boeing said the bulletin directs operators to "existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor".

USA aviation regulators plan to order airlines to follow Boeing Co.'s advisory on how pilots should handle false readings from a plane sensor that authorities linked to last week's deadly 737 Max jet crash off the coast of Indonesia.

The Boeing 737 MAX has three such sensors but erroneous readings could cause it to point the nose down sharply in order to keep air under the wings and avoid a stall, according to a person briefed on the matter. If either of the pressure sensors are blocked, it can cause erroneous readings.

Meanwhile, authorities are still investigating what exactly happened during the Lion Air crash, which killed 189 passengers.

Based on the preliminary data recovered from the wreckage of PK-LQP (msn 43000), the DJPU said that the aircraft's airspeed indicator malfunctioned during four flights prior to the doomed flight JT610 from Jakarta Soekarno-Hatta to Pangkalpinang.

Investigators examine engine parts from the ill-fated Lion Air flight JT 610 at a port in Jakarta on November 7, 2018, after they were recovered from the bottom of the Java sea.

Tjahjono said that due to the small size of the debris found and loss of the plane's engine blades, investigators determined that Flight 610 did not explode in the air, but was in "good shape" before it crashed 13 minutes after takeoff.

The 737 MAX is Boeing's newest and most advanced aircraft series, as well as the company's bestseller.

Soerjanto Tjahjono, chairman of Indonesia's National Transportation Safety Committee, said the problem was similar on each of the four flights, including the doomed one on October 29.

One of the critical ways a plane determines if a stall is imminent is a measurement known as angle of attack, which is a calculation of the angle at which the wind is passing over the wings.

But the National Transportation Safety Committee (NTSC) said on Monday that the black box data showed the plane had an air speed indicator issue on at least two other earlier flights.

It is a more fuel-efficient version of the manufacturer's best-selling single-aisle 737 series.

Boeing issues an operational update for 737.

The U.S. Federal Aviation Administration said it would issue an airworthiness directive to make Boeing's advice mandatory. But the urgency of a fatal accident can trigger a flurry of such notices.

For a safe climb-out, the aircraft's nose is pitched up at a small angle. In the early days of the jet age, the pitch trim system was linked to several accidents.

"When there was a problem, the pilot would write it down and the mechanic would do (a repair).Then the plane would be declared airworthy". That case didn't involve the angle-of-attack system.

"The pilots can use extra force to correct the nose down trim, but the failure condition repeats itself, so that the nose-down push begins again 10 seconds after correcting", reported The Seattle Times.