Some nations ground 737 Max 8 planes after second catastrophic crash in five months (3 Viewers)

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Bill said:
A pitot tube can definitely get clogged. In fact it's part of the walk around pre-flight check to visually inspect it for possibly having something plugging the opening. The sensitivity of the bellows in the airspeed indicator can very easily be affected by anything inhibiting the air pressure at the pitot opening.
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Sorry, that's my bad on "it".

I meant, obviously the Angle of Attitude sensor wouldn't clog. It doesn't have a hole, right? Just comparing the simplicity of how some of these sensors/gauges can fail.
 
Saint_Ward said:
Sorry, that's my bad on "it".

I meant, obviously the Angle of Attitude sensor wouldn't clog. It doesn't have a hole, right? Just comparing the simplicity of how some of these sensors/gauges can fail.
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No, the AoA wouldn't get clogged as a pitot hole might, but the little winglet of the AoA is on a spindle of sorts, and I would be interested in know how it is affected over its service life by things like air pressure, moisture, and sub zero temperatures. No doubt there is some sort of heating feature to keep it from freezing, but anything that could affect the ease at which the little winglet must swivel could be an issue for such an important sensor.
 
Saint_Ward said:
The side note, is if the AoA sensor is faulty or having problems, they need to address that as well. But the first two items will ensure we're safe while they figure out the last bit.
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There is no design issue with the AOA vanes that I am aware of. They stop working sometimes just like every bit of electronics and mechanical parts of an airplane cease to function as designed eventually. You note the fault, use alternate procedures and have a period of time to continue with alternate procedures until it has to be fixed. Something like the AOA probably has 10 days to get repaired. This is logged in a book that's kept with the aircraft and reviewed by the pilots before EVERY flight.

Saint_Ward said:
Yeah, I'm used to every major system having some redundancy. I don't know enough of the guts, but there has to be something else to cross reference potentially bad data.

Is this as simple/stupid as Pitot Tubes icing up, or otherwise clogged? Obviously, it doesn't clog, because I believe it's solid and it's just how the air moves or twists the sensor, but what could throw that out of alignment or stick? Can it ice up and bind? Sand stuck in there?
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Pitot tubes are 'tubes' and collect data from the air that flows into the tube. They are electronically heated to temperatures as high as 200°C, depending on the aircraft model.

The AOA sensor is a little "fin" that protrudes out from the fuselage near the nose of the aircraft. The fin tilts as the air flows across it to feed data to the aircraft computers in order to indicate the angle of the nose of the aircraft. In the picture you will see the pitot tubes and AOA vane right below the Captain's window. There are two pitot tubes with an AOA vane between them.

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MLU said:
There is no design issue with the AOA vanes that I am aware of. They stop working sometimes just like every bit of electronics and mechanical parts of an airplane cease to function as designed eventually. You note the fault, use alternate procedures and have a period of time to continue with alternate procedures until it has to be fixed. Something like the AOA probably has 10 days to get repaired. This is logged in a book that's kept with the aircraft and reviewed by the pilots before EVERY flight.

Pitot tubes are 'tubes' and collect data from the air that flows into the tube. They are electronically heated to temperatures as high as 200°C, depending on the aircraft model.

The AOA sensor is a little "fin" that protrudes out from the fuselage near the nose of the aircraft. The fin tilts as the air flows across it to feed data to the aircraft computers in order to indicate the angle of the nose of the aircraft. In the picture you will see the pitot tubes and AOA vane right below the Captain's window. There are two pitot tubes with an AOA vane between them.

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I've cross sectioned a few Pitot Tubes in my day, so I know those well enough. I just haven't seen a AoA up close.
 
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Currently optional, there is some thought that the Boeing will add the AOA disagree warning indication to future B73M and retrofit those already being flown. The software update could possibly include a feed to the AOA data being recorded. It sounds like the US carriers (except Southwest) opted to have the warning indication installed on their orders already. Southwest will probably have it added to future orders.
 
MLU said:
Currently optional, there is some thought that the Boeing will add the AOA disagree warning indication to future B73M and retrofit those already being flown. The software update could possibly include a feed to the AOA data being recorded. It sounds like the US carriers (except Southwest) opted to have the warning indication installed on their orders already. Southwest will probably have it added to future orders.
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Sounds like a step in the right direction.
 
The National Transportation Safety Committee (KNKT) for Indonesia has confirmed that the day before the Lion Air crash, on the very same aircraft that crashed it experienced the same issue. The difference being that there was a jump-seating pilot in the cockpit who prompted the working crew on what to do per the checklist.

...media reports quoting sources who were close to the case said the so-called dead-head pilot on the flight from Bali to Jakarta told the crew to cut power to the automated system designed to lower the nose of the plane when it receives information from the AOA sensors that the aircraft is flying too slowly or steeply, and for them to take back manual control of the plane. According to analysts this is part of a checklist that all pilots are required to memorize.
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MLU said:
The National Transportation Safety Committee (KNKT) for Indonesia has confirmed that the day before the Lion Air crash, on the very same aircraft that crashed it experienced the same issue. The difference being that there was a jump-seating pilot in the cockpit who prompted the working crew on what to do per the checklist.
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https://www.nytimes.com/2019/03/25/business/boeing-simulation-error.html

The article states that they had training that only gave them 40 seconds to figure it out and cut the switch.

Good thing that jump pilot was on that other aircraft.

“There is a limited window to solve this problem, and this crew didn’t even know that this system existed,” he said.
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So, a few things...

1) 40 seconds is a long time. A lot can happen up front in 40 seconds. It sounds like a short period of time, but it shouldn't be something a trained crew can't handle.

2) The crew begins the checklist when they get the error in the simulation it sounds like. They run the simulation with the knowledge of the familier before hand. Im not sure if the 40 seconds takes this into consideration and is the limitation or not, but I would be interested to know.

3) Ethiopian Air stated that both pilots had been briefed of this issue after the Lion Air flight. I am interested to know if the CVR will find them going through the checklist. It should be pretty fresh on their minds.
 
Weird that they called Orlando OIA instead of by it's call letters, MCO.

 

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