Boeing Jet Crashed in Indonesia After Key Sensor Replaced

[turbinetree]

Source: New York Times

By The Associated Press
Nov. 7, 2018

JAKARTA, Indonesia — A crucial sensor that is the subject of a Boeing Co. safety bulletin was replaced on a Lion Air jet the day before it plunged into the Java Sea and possibly worsened other problems with the plane, Indonesian investigators said Wednesday.

Indonesia's National Transportation Safety Committee said it had agreed with Boeing on procedures that the airplane manufacturer should distribute globally on how flight crews can deal with "angle of attack" sensor problems following the Oct. 29 crash that killed all 189 people on board.

The sensor keeps track of the angle of the aircraft nose relative to oncoming air to prevent the plane from stalling and diving.

But a Boeing statement said a safety bulletin, sent to airlines on Tuesday, directs flight crews to existing guidelines on how they should respond to erroneous "angle of attack" data. It wasn't immediately clear if it plans an update, though comments from Indonesian officials indicate they expect one.

Read more: https://www.nytimes.com/aponline/2018/11/07/world/asia/ap-as-indonesia-lion-air-crash.html

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If the AOA sensor (angle of attack) on the outside of the plane has been replaced, a maintenance manual procedure must be accomplished.

The angle of attack sensor looks like a triangle shaped wing, that is on the side of the plane, (usually left hand side) it must have a Rosecran attached to the outside of the fuselage to perform the ground test when the angle of attack wing or sensor is moved to the associated degrees marking on the Rosecrans, if the angle of attack sensor is put in the down position the control wheel stick must start shaking, and the stall must be avoided by pushing the control wheel forward , if the sensors is placed in the up position a overspeed warning light will illuminated also with stick shaker bell going off.

This means that the plane is suppose to be jacked up and put in flight configuration to perform that stall warning check if the LRU (line replacement unit) and the angle of attack sensor have been replaced..................that is the question was this procedure performed.................


http://www.boeing.com/commercial/aeromagazine/aero_12/attack_story.html

[Roland99]

1. Ruh roh. But, uh, who's the copy editor?

A crucial sensor that is the subject of a Boeing Co. safety bulletin was replaced on a Lion Air jet the day before it plunged into the Java Sea and possibly worsened other problems with the plane

Um, yeah, crashing into the sea would worsen other problems with the plane!

[paleotn]

4. Ha!

[Hassin Bin Sober]

2. It's shaping up to look like the angle of attack envelope protection system dove...

... the plane in to the ocean.

That would explain the “roller coaster ride” on the previous flight.

The system senses a stall and forces the nose down. Which is fine if you are actually stalling.

Apparently the forces applied by the envelope protection system are very strong. At 5,000 feet, the pilots didn’t have a lot of time to react and disable the system.

[turbinetree]

3. Correct, that stall warning vane in my opinion was not checked against the Rosecrans indicator

that is attached to the fuselage during a maintenance stall check, to have the WOW (weight off wheels simulation of flight indication) removed by placing lugs in the landing gear sensors to make the plane think it was in flight and then mimicking the flight control deployment and retraction and airspeed. In the older 737 and some newer ones there is a test button(s) or switch(s) to get the control wheels to shake and to get aural warnings off the MFD (multifunction display units) and other FMS (flight management system) display screens

I would like to know if they jacked the airplane up and performed the performance maintenance procedures of that stall indication............to verify proper operating parameters of the flight controls against the LRU and that vane


This is really sad..................