Lion Air 737 MAX crashed

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Re: Lion Air 737 MAX crashed

Unread post by Hexapilot » Sun Jan 06, 2019 10:51 pm

It sounds to me like an accountant was the cause of this crash.
We are in the <<moderated - language>> because accountants are deciding on training, manufacturing and quality controll nowadays, and not engineers and old hands with tons of experience.
Profit margins are calculated quarterly, and stock prices are based on these quarterly results. But yet, safety, experience and good engineering principals are not held to the same time and margin based constraints as what accountants deem to be profitable for a good return on investment, or quaterly report.

If you want to be safe and reliable, shoot the beancounter and listen to the engineer.
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Re: Lion Air 737 MAX crashed

Unread post by richard C » Thu Jan 10, 2019 8:32 am

Hexapilot wrote:
Sun Jan 06, 2019 10:51 pm
It sounds to me like an accountant was the cause of this crash.
We are in the <<moderated - language>> because accountants are deciding on training, manufacturing and quality controll nowadays, and not engineers and old hands with tons of experience.
Profit margins are calculated quarterly, and stock prices are based on these quarterly results. But yet, safety, experience and good engineering principals are not held to the same time and margin based constraints as what accountants deem to be profitable for a good return on investment, or quaterly report.

If you want to be safe and reliable, shoot the beancounter and listen to the engineer.
...and lawyers go around shooting the survivors.

Not only in aviation, but most of the professions too.
Grant all equity and dignity.
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Re: Lion Air 737 MAX crashed

Unread post by Deanw » Mon Jan 14, 2019 7:34 am

Cockpit Voice Recorder has now been found, apprantely buried meters under the sea floor at a depth of 30 meters.
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Re: Lion Air 737 MAX crashed

Unread post by Ugly Duckling » Mon Jan 14, 2019 8:14 am

Deanw wrote:
Mon Jan 14, 2019 7:34 am
Cockpit Voice Recorder has now been found, apprantely buried meters under the sea floor at a depth of 30 meters.
Hopefully intact and readable
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Re: Lion Air 737 MAX crashed

Unread post by Hop Harrigan » Mon Jan 21, 2019 7:37 pm

Anyone know if the CVR recording is readable?
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Re: Lion Air 737 MAX crashed

Unread post by Schallas » Mon Jan 21, 2019 8:20 pm

Hop Harrigan wrote:
Mon Jan 21, 2019 7:37 pm
Anyone know if the CVR recording is readable?
Hop
Yeah the data is good. They extracted 124 min of good recordings.

http://avherald.com/h?article=4bf90724/0009&opt=0
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Re: Lion Air 737 MAX crashed

Unread post by Christopher » Thu Feb 07, 2019 12:35 am

Long, long article all about this accident on front page of Sunday's New York Times, with particular reference to the fact that Boeing had not notified operators about new systems in the aircraft, compared with the previous model. The European Aviation authority at first were in conflict with Boeing, making it clear that they thought that all operators/pilots should be informed and <trained>; but later fell into line with the manufacturer(who naturally wanted to spare operators the costs of further training -- so they said!)

It all stems from the possibility of false information from AoA indicators under less-than-ideal conditions (ie, when errors might occur).

I wonder if someone can look this up and post -- very thorough, if long, article, which started on front page and then went into a double-page spread!
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Re: Lion Air 737 MAX crashed

Unread post by Ajay » Thu Feb 07, 2019 3:20 am

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Re: Lion Air 737 MAX crashed

Unread post by Christopher » Sat Feb 09, 2019 5:48 pm

Thanks, Ajay!
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Re: Lion Air 737 MAX crashed

Unread post by heisan » Sat Feb 09, 2019 7:06 pm

I wonder how much of a difference it would have made if the pilots knew about the MCAS system?

As I understand it, the memory actions and QRH actions remain the same, whether the trim runs away because of MCAS, or for any other reason.

Would a detailed understanding of the MCAS system have made any difference in how the pilots would have handled the situation?
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Re: Lion Air 737 MAX crashed

Unread post by Hop Harrigan » Sat Feb 09, 2019 7:53 pm

Is a flippin’ piece of blink flappin’ in the wind really the only way to measure AoA? In this day and age isn’t there a better way to do this?
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Re: Lion Air 737 MAX crashed

Unread post by StressMerchant » Sun Feb 10, 2019 3:14 am

Hop Harrigan wrote:
Sat Feb 09, 2019 7:53 pm
Is a flippin’ piece of blink flappin’ in the wind really the only way to measure AoA? In this day and age isn’t there a better way to do this?
There are several alternative ways of measuring AoA, but for a multi-engine vanes are often the most effective solution.

A number of light aircraft use a differential pitot-static measurement system, which is essentially a pitot tube inclined to the aircraft longitudinal axis by an angle (usually 45 degrees). The AoA is deduced from the difference between the dynamic pressure of the normal pitot and the dynamic pressure of the inclined pitot. The system works surprisingly well, although I'm not sure how well it handles compressibility changes.

The next method involved use of the information from the gyro, accelerometer, and barometric instruments. Typically these instruments are present within the Inertial Motion Unit (IMU) / Attitude Heading and Reference System (AHRS). The AoA can be derived from the data by further calculations. I understand that some of the latest systems will display this as a back-up to the flight crew. On a smaller aircraft we used this to estimate AoA during dynamic manoeuvres, but we were only able to do this after the flight - we never had the systems to carry out the data fusion in real time. And it was a lot of maths.

The problem with the data fusion approach is that the failure cases become more and more complex as you add additional sensors. The traditional AoA vanes are fairly simple, can be duplicated for redundancy, and can be compared by a caution and warning system. The failure potential of any system must be assessed under the design regulations (FAR 25.1309), it becomes a lot simpler to use duplicated vanes, have an alerting system, and a flight deck procedure to deal with a failure. The IMU based system is potentially not as accurate (it is essentially showing a history), has more failure modes, and ultimately would still require a cockpit procedure to deal with the failure.

As flight control systems become more integrated, there may be a shift away from vanes simply because the IMU / AHRS systems are improving and are going to be present anyway.

Edit: Adding two links if anyone wants to do a bit of reading. Both reports from the FAA:
http://www.tc.faa.gov/its/worldpac/techrpt/tc18-7.pdf
Low cost AoA system, using the pitot-static method described above

http://www.tc.faa.gov/its/worldpac/techrpt/tc16-52.pdf
Comparison of different techniques.
Last edited by StressMerchant on Sun Feb 10, 2019 7:09 am, edited 1 time in total.
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Re: Lion Air 737 MAX crashed

Unread post by jimdavis » Sun Feb 10, 2019 6:06 am

Thanks Stressers - your posts are always interesting.

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Re: Lion Air 737 MAX crashed

Unread post by Hop Harrigan » Sun Feb 10, 2019 11:52 am

Hi S&M😀,
Thanks for the info. I can see the attraction of the vane from a reliability and simplistc viewpoint. Maybe a more reliable, less icing prone design is required. However in this case it sounds like it maybe wasn’t a mechanical or ice fault, but rather a fault in the electronics that interfaces the vane to the processors (I think the tech changed a pc board).
I also find it a bit dof that the computer can’t figure out which instrument is giving bad readings and indicate to the crew which one should be used instead of forcing the crew to troubleshoot under high stress conditions. This isn’t the first time a faulty AoA indication has brought an otherwise serviceable airliner down
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Re: Lion Air 737 MAX crashed

Unread post by Breytie » Sun Feb 10, 2019 9:29 pm

Internal instruments (gyros / accelerometers etc) can give attitude information - where the nose is in relation to the horizon.
A vane or pitot-static based systems measure the actual airflow direction. The plane may be horizontal, but strong up and down drafts change the relative airflow direction. Same thing for GPS based ground speed vs airspeed. Like many planes now have systems that calculate and predict stall, older planes had horns that sounded when the wing actually started stalling, causing a change in pressure at the port on the wing.

Now a daft sounding question - If your plane uses a gyro based system for attitude indication - how does that system compensate for the curvature of the earth on long distance flights? You end up literally upside down when you land in Perth compared to when you took off from ORT.

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