Author Topic: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'  (Read 23829 times)

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Offline janoc

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #50 on: November 01, 2018, 04:29:41 am »
Alaska 261 was a horizontal stabilizer (controls pitch trim) jackscrew issue, not a rudder (controls yaw) defect.

That it is almost surely unrelated is 100% true (other than both flights ending in water with loss of all aboard).

Ah right, not sure why I wrote "rudder". D'oh. Thanks for the correction.
 

Online BravoV

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #51 on: November 01, 2018, 03:01:07 pm »
Latest update from local news by the reporter that on the SAR ship, black box recovered today at 10 am local time, and apparently undamaged, and it was buried under the mud at about 30m from the surface.

The signals were detected at these coordinates S 05 48 48.051 - E 107 07 37.622 and S 05 48 46.545 - E 107 07 38.393.






Transferred into proper & safe container.

« Last Edit: November 01, 2018, 03:30:20 pm by BravoV »
 

Offline EEVblog

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #52 on: November 01, 2018, 04:30:06 pm »
Latest update from local news by the reporter that on the SAR ship, black box recovered today at 10 am local time, and apparently undamaged, and it was buried under the mud at about 30m from the surface.

I'm surprised the pinger worked under the mud, but then again, 30m of water makes it vastly easier
 

Offline amyk

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #53 on: November 01, 2018, 11:15:35 pm »
Something like https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261 ?
Flight 261 was an MD83, not a 737, the rudder is driven in a different way. And given that this was a brand new plane, the chance that something has worn out already (in the 261 crash the rudder jackscrew threads were worn off due to poor maintenance) is minimal.
Alaska 261 was a horizontal stabilizer (controls pitch trim) jackscrew issue, not a rudder (controls yaw) defect.

That it is almost surely unrelated is 100% true (other than both flights ending in water with loss of all aboard).
I meant related as in "sudden failure of control surface". The fact that the plane was so new means it could be a manufacturing defect.

Good they recovered the recorders, we should get the answer soon.
 

Offline Homer J Simpson

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #54 on: November 01, 2018, 11:36:15 pm »

Scanning the Wikipedia article on the 737 Max...........

https://en.wikipedia.org/wiki/Boeing_737_MAX

Seems to have been / is a lot of pressure to produce as many planes as possible.



"On August 13, 2015, the first 737 MAX fuselage completed assembly at Spirit Aerosystems in Wichita, Kansas, for a test aircraft that would eventually be delivered to launch customer Southwest Airlines.[26] On December 8, 2015, the first 737 MAX—a MAX 8 named "Spirit of Renton"—was rolled out at the Boeing Renton Factory.[27][28]

Because GKN could not produce the titanium honeycomb inner walls for the thrust reversers quickly enough, Boeing switched to a composite part produced by Spirit to deliver 47 MAXs per month in 2017. Spirit supplies 70 percent of the 737 airframe, including the fuselage, thrust reverser, engine pylons, nacelles, and wing leading edges.[29]

A new spar-assembly line with robotic drilling machines should increase throughput by 33 percent. The Electroimpact automated panel assembly line sped up the wing lower-skin assembly by 35 percent.[30] Boeing plans to increase its 737 MAX monthly production rate from 42 planes in 2017 to 57 planes by 2019.[31]

The rate increase strains the production and by August 2018, over 40 unfinished jets were parked in Renton, awaiting parts or engine installation, as CFM engines and Spirit fuselages were delivered late.[32] After parked airplanes peaked at 53 at the beginning of September, Boeing reduced this by nine the following month, as deliveries rose to 61 from 29 in July and 48 in August.[33] "



Interesting if it turns out to be related to manufacturing.

 

Offline boffin

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #55 on: November 02, 2018, 04:55:36 am »
The rate increase strains the production and by August 2018, over 40 unfinished jets were parked in Renton, awaiting parts or engine installation, as CFM engines and Spirit fuselages were delivered late.[32] After parked airplanes peaked at 53 at the beginning of September, Boeing reduced this by nine the following month, as deliveries rose to 61 from 29 in July and 48 in August.[33] "

Hard to imagine there's room for 40 unfinished jets at Renton, it's a pretty small airport.  There's 27 parked there (all over the airfield) in the Google Sat image; and they're spread out all over the place, not sure where you'd find the room to double that.

Boffin at play https://snafu.ca/
 

Offline boffin

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #56 on: November 02, 2018, 04:59:20 am »
I'm reading that it's the Flight Data Recorder (there are two 'black boxes' the FDR and the Cockpit Voice Recorder)..

In the past there have been issues with 737 rudders (https://en.wikipedia.org/wiki/Boeing_737_rudder_issues) , but that was completely redesigned  with the previous generation of the 73.  Until they start looking at what's on that recording, we really wont know.
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Offline raptor1956

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #57 on: November 02, 2018, 05:20:25 am »
As a Avionics Instruments tech while working in the USAF back in the day the reports from a previous flight that also had a problem shortly after takeoff that cleared and they continued on there flight it's looking to me that rather than a cover on a pitot tube it looks like a fitting in the system maybe lose giving erratic readings but then stabilize later.  The pitot static system consists of two lines: the static line that monitor atmospheric pressure used for altitude and vertical velocity, and a ram pressure that's used for indicated airspeed and used in combination with the static pressure and temperature for TAS.  I suspect that the static line had a lose fitting and if that's true it's also possible a ram pressure line may also have been lose.

During maintenance of the pitot static system lines are opened to hook up test equipment to provide calibrated pressures to check the altimeters and airspeed indicators for correct readings.  Of course, when the tests are done the equipment is disconnected AND the lines must then be reconnected.  I've seen it happen where this is done but the fittings are not tightened -- they are snugged up but not immediately tightened so at some point down the road the back off a bit and...

The FDR should reveal this even of the pilots didn't properly identify it.


Brian
 

Online Wolfgang

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #58 on: November 03, 2018, 12:20:37 am »
one of the more trivial reasons for a Pitot failure is an insect stuck in the inlet.
The incoming air then never reaches the heater, icing could occur and the readings are nonsense.
 

Offline raptor1956

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #59 on: November 03, 2018, 05:20:09 am »
one of the more trivial reasons for a Pitot failure is an insect stuck in the inlet.
The incoming air then never reaches the heater, icing could occur and the readings are nonsense.


Yes, that's true, however the previous flight reported similar issues so you would THINK they would do an inspection of the pitot tubes before the next flight.

But, erratic readings could be explained by an inspect or other FOD in the pitot tube.

Again, this should be plainly obvious in the FDR data.


Brian
 

Offline IanMacdonald

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #60 on: November 03, 2018, 06:11:10 am »
I'm not a pilot and have only rudimentary knowledge about this. Hopefully not too much of a noob question.... but if a Pitot tube or aircraft speed sensor was blocked or malfunctioning, it would tell the pilot the aircraft is going too slow? So wouldn't they speed up the airplane? Wouldn't speeding up help keep it flying in the air? I would imagine the reverse would be worse, where the sensor is telling you that you are going fast and you slow down and stall.

No. The ASI measures the difference in pressure between the pitot and static vents. The pitot pressure would remain as it was before it was blocked, so the instrument would likely read the same regardless of a speed increase or decrease in level flight. Although as you gained altitude the indicated speed would increase due to the reducing pressure on the static side. That's maybe what happened, and lead to a stall.

In fact, for VMC flying anyway, most of the stuff on the instrument panel is eye candy. The one thing you really need is to know your airspeed, as it's hard to judge visually.  The rest you can tell with the Mk1 eyeball.

 

Online Gyro

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #61 on: November 03, 2018, 06:23:48 am »
Is there no sanity check built into the system for the airspeed indication (other than the duplicated pitots and instruments)?

I would have though that the system ought to be able to combine engine thrust, altitude, attitude, control surface settings, takeoff weight, fuel used etc. to calculate and generate an airspeed display plausibility warning. Maybe even to provide a emergency backup 'estimated' airspeed indication?
« Last Edit: November 03, 2018, 06:25:35 am by Gyro »
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Offline cdev

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #62 on: November 03, 2018, 06:49:42 am »
One would think that after the accident over the Atlantic several years ago, that the pitot tube icing issue would have been solved by installing multiple redundant pitot tubes, as well as multiple redundant everything else. the same thing with the satellite data link. Every multimillion dollar aircraft that flies should have one tied to a pair of redundant GPS receivers, one at the nose and one near the tail. Using the two it should be possible to get the exact position and heading anywhere in the world of every one of those planes, in seconds. They get a very good quality of data simply from GPS of their airspeed. The pitot tubes might be good to have but they should all be looked at at the same time and if any of the readings is wildly divergent, it should be eliminated as such an outlier its almost certainly wrong.
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Online Nusa

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #63 on: November 03, 2018, 06:53:59 am »
Is there no sanity check built into the system for the airspeed indication (other than the duplicated pitots and instruments)?

I would have though that the system ought to be able to combine engine thrust, altitude, attitude, control surface settings, takeoff weight, fuel used etc. to calculate and generate an airspeed display plausibility warning. Maybe even to provide a emergency backup 'estimated' airspeed indication?

Of course there is, and it's been well established in this thread already. If two completely independent systems don't agree on airspeed, the pilots are going to be alerted. If they follow their training, they'll go to pitch and power settings to ensure a proper airspeed, then they can reference the backup instrument for a third independent reading. If there's no consensus, they can fly pitch and power settings all the way to a safe landing.

If machines were good enough to be trusted to do the job all the time, there wouldn't be pilots on board at all.
 

Online Nusa

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #64 on: November 03, 2018, 06:57:18 am »
One would think that after the accident over the Atlantic several years ago, that the pitot tube icing issue would have been solved by installing multiple redundant pitot tubes, as well as multiple redundant everything else. the same thing with the satellite data link. Every multimillion dollar aircraft that flies should have one tied to a pair of redundant GPS receivers, one at the nose and one near the tail. Using the two it should be possible to get the exact position and heading anywhere in the world of every one of those planes, in seconds. They get a very good quality of data simply from GPS of their airspeed. The pitot tubes might be good to have but they should all be looked at at the same time and if any of the readings is wildly divergent, it should be eliminated as such an outlier its almost certainly wrong.

GPS doesn't give airspeed, it gives ground speed. Great for navigation, but very inaccurate as an airspeed replacement. Could differ by as much as 250mph if the plane is in a jet stream.
« Last Edit: November 03, 2018, 06:59:11 am by Nusa »
 
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Offline tautech

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #65 on: November 03, 2018, 07:00:02 am »
One would think that after the accident over the Atlantic several years ago, that the pitot tube icing issue would have been solved by installing multiple redundant pitot tubes, as well as multiple redundant everything else. the same thing with the satellite data link. Every multimillion dollar aircraft that flies should have one tied to a pair of redundant GPS receivers, one at the nose and one near the tail. Using the two it should be possible to get the exact position and heading anywhere in the world of every one of those planes, in seconds. They get a very good quality of data simply from GPS of their airspeed. The pitot tubes might be good to have but they should all be looked at at the same time and if any of the readings is wildly divergent, it should be eliminated as such an outlier its almost certainly wrong.
GPS derived ground speed means shit for flying a plane, you need airspeed which can be influenced by prevailing winds that could be all over the place at different altitudes.
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Online Gyro

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #66 on: November 03, 2018, 07:08:34 am »
Is there no sanity check built into the system for the airspeed indication (other than the duplicated pitots and instruments)?

I would have though that the system ought to be able to combine engine thrust, altitude, attitude, control surface settings, takeoff weight, fuel used etc. to calculate and generate an airspeed display plausibility warning. Maybe even to provide a emergency backup 'estimated' airspeed indication?

Of course there is, and it's been well established in this thread already. If two completely independent systems don't agree on airspeed, the pilots are going to be alerted. If they follow their training, they'll go to pitch and power settings to ensure a proper airspeed, then they can reference the backup instrument for a third independent reading. If there's no consensus, they can fly pitch and power settings all the way to a safe landing.

If machines were good enough to be trusted to do the job all the time, there wouldn't be pilots on board at all.

So there's a nice big indicator saying one or both of your airspeed indications may be implausible, without relying on the pilots constantly visually cross-checking their indicators?

Edit: Sorry, I missed the reference to a third, backup, instrument. Is that Pitot too?... and is it linked into the automatic comparison warning too?
« Last Edit: November 03, 2018, 07:40:06 am by Gyro »
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Offline cdev

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #67 on: November 03, 2018, 08:11:07 am »
I bet!

 the speed of the gulf stream etc, adds a substantial boost/slow down to planes flying in it, you can see that happening when they change their heading in relation to it.
GPS derived ground speed means shit for flying a plane, you need airspeed which can be influenced by prevailing winds that could be all over the place at different altitudes.

Multiple, heated pitot tubes would be good, I wonder what other kinds of air speed sensors exist.

Anything mechanical that I can think of right now at least, besides a pitot pressure indicator would likely fail at a typical jets speed though.
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Offline Mr. Scram

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #68 on: November 03, 2018, 08:23:45 am »
Multiple, heated pitot tubes would be good, I wonder what other kinds of air speed sensors exist.

Anything mechanical that I can think of right now at least, besides a pitot pressure indicator would likely fail at a typical jets speed though.
Mechanical measures aren't completely infeasible. A small propeller device is deployed when all engines and the APU fail to power the bare essentials. This device is obviously capable of dealing with fairly substantial forces, even though a gliding jet liner will be slower than at cruising speeds.
 

Online Wolfgang

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #69 on: November 03, 2018, 08:24:09 am »
I bet!

 the speed of the gulf stream etc, adds a substantial boost/slow down to planes flying in it, you can see that happening when they change their heading in relation to it.
GPS derived ground speed means shit for flying a plane, you need airspeed which can be influenced by prevailing winds that could be all over the place at different altitudes.

Multiple, heated pitot tubes would be good, I wonder what other kinds of air speed sensors exist.

Anything mechanical that I can think of right now at least, besides a pitot pressure indicator would likely fail at a typical jets speed though.

When I took my flying lessons (AS350B3) the procedure for a suspect Pitot was to fly a circle and to look at the difference of TAS and ground speed.
 

Offline khs

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #70 on: November 03, 2018, 09:13:44 am »
here a link to an Austrian website (English) discussing crashes & accidents..

http://avherald.com/h?article=4bf90724&opt=0
 

Online Nusa

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #71 on: November 03, 2018, 09:26:19 am »
When I took my flying lessons (AS350B3) the procedure for a suspect Pitot was to fly a circle and to look at the difference of TAS and ground speed.

Perfectly reasonable for a helicopter, for which low airspeed by itself typically isn't an emergency. Maneuvers that cause low rotor speeds/blade stall are the real killers, as I understand it. Not that I've had any rotor training.
 

Online Wolfgang

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #72 on: November 03, 2018, 09:37:13 am »
When I took my flying lessons (AS350B3) the procedure for a suspect Pitot was to fly a circle and to look at the difference of TAS and ground speed.

Perfectly reasonable for a helicopter, for which low airspeed by itself typically isn't an emergency. Maneuvers that cause low rotor speeds/blade stall are the real killers, as I understand it. Not that I've had any rotor training.

You would run this maneuvre at a medium power setting (80% MCP) and a level flight, and try a 2 minutes turn. Bank angle should be very moderate then.
 

Offline EEVblog

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #73 on: November 03, 2018, 07:33:20 pm »
 

Offline EEVblog

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Re: Lion Air crash: Jakarta Boeing 737 'had prior instrument error'
« Reply #74 on: November 03, 2018, 07:36:57 pm »
Surprised at how intact the black box is, pinger still attached:

 


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