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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 21:58
  #1201 (permalink)  
 
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Originally Posted by Ian W
The amount of information broadcast continually by ADS-B Extended Squitter is significant aircraft state, vertical and turn rates, FMC settings lots of information.
Being picky, not all of those are in the ADS-B Extended Squitter. Some (turn rate, FMC mode, IAS, etc) only get sent in response to a Mode S EHS interrogation.

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Old 13th Mar 2019, 21:59
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Bucket loader & bulldozer trashing crash wreckage

Why were two large commercial bucket loaders and a large bulldozer trashing through the crash cite Monday as seen on CNN?

I hope the CVR and FDR are reliable sources of info for this accident. All victoms RIP...
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Old 13th Mar 2019, 22:04
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Originally Posted by Vilters
The most fragile things in the whole system are the sensors that are always exposed to the outside world.
In most cases, it is a sensor breaking up, or feeding wrong information to the pilots/systems.We absolutely need more and better quality control (and back-up's) for the sensors.
Static, dynamic, AOA, all of them.
I am merely SLF, but I do a LOT of industrial machine control systems work. I and my team spend a lot of thought and effort to detect when the sensors aren't making sense, because that is the number one cause of problems in that world. In my case it's usually just making a few hundred thousand dollars worth of scrap, not augering into terrain with a few hundred pax aboard.

It is not possible to make a 100% reliable sensor. For any measurement.
If that measurement is important, you need to validate it.

Always being aware that the validation may itself induce faults.

I will crawl back into my cave now.
...tom
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Old 13th Mar 2019, 22:09
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Originally Posted by NWA SLF
If I remember AF447 correctly it was all speculation as there was no data until over a year later when the recorders were recovered. At that time, if my memory serves me right, data showed the flight crew member in the right seat was commanding pitch up with his joystick while the pilot in the left seat was either neutral or pitch down. Basic flaw of joysticks on 2 crew cockpits in that they do not provide input by feel between flight crew. Thales sensors were speculation due to failure history.

I keep looking here to see if there is data confirming why Ethiopian crashed similar to the data on Lion Air. Have I missed it? In the case of the Lion Air there was the history of the previous flight where the pilot experienced the same sensor malfunction yet flew to destination. Ethoiopian says the previous flight was normal with no write-ups. It reminds me so much of the AA DC-10 in Chicago where the action was to shoot first and ask questions later with the evidence of what happened lying on the runway. Yes, the DC-10 had many faults resulting from rushing into production but engines falling off wings was not one of them. Engines falling off wings causing the slats to retract was a design flaw.

Now the media is interviewing MAX pilots who say they have spent their time as MAX pilots terrified of their life due to control problems. How come they did not say this before? And we have Donald Trump saying airplanes today are too complex for pilots to fly. It just keeps getting worse and worse.
...
Engines falling off wings causing the slats to retract was a design flaw.
nope it was a maintenace method screw up to starrt - and a cross feed/non crossfeed design issue/method/decision which caused slats to retract.
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Old 13th Mar 2019, 22:09
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Ok call me stupid but without a professional analysis of the FDR, which, to the best of my knowledge, has not happened yet I call BS on this grounding hysteria.

We still donít have the Lion air full report but to me the principal cause is faulty sensors and gross negligence: this aircraft should never have been used for passengers flights. The MCAS is most probably a contributing factor and reflects poorly on Boeing but I still do not see it in itself as a showstopper. As for the Ethiopian crash we are way too early to draw any conclusion. An immediate airspace ban of the whole fleet is utter madness. A progressive grounding out of extreme caution ? Ok. But what is going on right now is completely out of control (pun intended).
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Old 13th Mar 2019, 22:10
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Originally Posted by Vilters
The most fragile things in the whole system are the sensors that are always exposed to the outside world.
In most cases, it is a sensor breaking up, or feeding wrong information to the pilots/systems.We absolutely need more and better quality control (and back-up's) for the sensors.
Static, dynamic, AOA, all of them.
You need an A350: https://en.wikipedia.org/wiki/Airbus...512991673).jpg

Its all very well having dozens of sensors, but the flight systems must be able to interpret them.
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Old 13th Mar 2019, 22:12
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Seems there are claims of a discrepancy in the timeline of the FAA having the Aireon data and deciding to act on it. Data supposedly given to FAA on Monday , but claimed here that they sat on it and their action came only after the Canadians were given it and acted on it.
Cannot post urls but search paxex.aero and Aireon space-based Ads-B data
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Old 13th Mar 2019, 22:29
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Originally Posted by LookingForAJob
CNN just reported that FAA based decision on 'black box data' that showed similarities to the Lion Air accident.
As usual cnn has collective heads up posterior- no black box data from second crash yet - BUT more detsails from satellited data available

Waiting for cnn to blame trump . . .

Bingo !!!CNN Host Says Shutdown To Blame For Boeing Crash In Ethiopia

2:28 PM 03/13/2019 | Politics
The article in question ran in The WSJ under the headline “Boeing to Make Key Change in 737 MAX Cockpit Software.” The article asserted that Boeing engineers had expected to push out a software update to the airplanes sometime in January, but it was delayed due to “differences of opinion and technical and engineering issues.”Instead of the FAA being asleep at the wheel, thousands of safety inspectors and other staff were recalled to ensure that all planes continued to be operated in a safe manner.
BUT wash post said
=leftFAA's emergency order grounding Boeing jets came after the agency identified similarities between crashes in Ethiopia, IndonesiaThe FAA developed new information from the wreckage of a 737 crash in Ethiopia that painted similarities to an earlier crash in Indonesia, leading the agency to ground all Boeing 737 Max 8 and 9 aircraft in the U.S., three people familiar with the matter said.



Last edited by CONSO; 13th Mar 2019 at 22:46. Reason: added cnn position on trump and shutdown
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Old 13th Mar 2019, 22:29
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Originally Posted by auldlassie
Seems there are claims of a discrepancy in the timeline of the FAA having the Aireon data and deciding to act on it. Data supposedly given to FAA on Monday , but claimed here that they sat on it and their action came only after the Canadians were given it and acted on it.
Cannot post urls but search paxex.aero and Aireon space-based Ads-B data
Interesting report: https://paxex.aero/2019/03/aireon-ad...max-grounding/
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Old 13th Mar 2019, 22:45
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Originally Posted by MPN11
UK Channel Islands airspace now closed to 737 MAX ... valuable, since none of our airports are big enough to take the aircraft anyway!
Thatís not true. Both Jersey and Guernsey airports are suitable for 737 Max operations on shorter flights.
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Old 13th Mar 2019, 22:49
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Originally Posted by Tech Guy
If one presumes the grounded aircraft will be towed to an unused corner of their respective airports rather than taking up valuable space on the apron, or at gates, would preventative preparations be made for an extended grounding? How long can the aircraft be grounded for in a "cold" state without requiring extensive checks and maintenance prior to returning to service?

Would the airports be levying a "storage charge"?
Quite possible that airlines will in the next few days get permission (Day VMC) for one off ferry flights to airfields suitable for aircraft storage.
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Old 13th Mar 2019, 22:54
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Originally Posted by GordonR_Cape
Interesting report:
This is sad. It shows a likely case of willful blindness by the FAA and/or Boeing.

It's like the FAA: "I don't see anything to correlate the two, what are you talking about?"

Marc Garneau: "Check this out everyone!"

FAA (late to the party): "oh. There is is. Guess we had trouble reading the data (somehow) the first time. Ok we are going to have to do a ground stop on this one or we aren't going to look very good."
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Old 13th Mar 2019, 22:56
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Originally Posted by Cows getting bigger
FCeng84, thanks for the very useful aerodynamics lessons. Joining others, we may be jumping ahead somewhat in our assumptions about the Ethiopian and indeed Lion crash but I personally believe that having now turned-over the MCAS stone the issue must be addressed, regardless of it's (non) role in recent accidents. Some (random) questions/observations:

Before the pilot world knew about MCAS, how would an MCAS failure have been manifested? Should it have been an 'MEL' Item? In other words, if it was not visible/known to pilots, how would anyone have known the system was working? Consequently, was it just looked upon as a sticking plaster necessary to get over a certification requirement and something that didn't need to be monitored or even in place for real world operations? I'm reminded of VW diesel engines and emission tests.

What was the rationale behind only using a single data source to the MCAS?

I think it has already been addressed but, does the flight regime mean that MCAS will activate at/before/about the same time as the stick shaker?

How did Boeing come to the conclusion that a 5 second pause after pilot trim inputs was the MCAS reset period?
MCAS does not use any equipment not already on the airplane, so nothing new to keep track of with regard to component failures. The manifestation of an MCAS failure would depend on the nature of that failure so hard to address that question without specifics. Lion Air discussion covers manifestation of MCAS response to an AOA sensor signal bias / failed high scenario.

As for the rationale behind basing MCAS on a single sensor, that is the default architecture for 737 with each FCC using only the sensors wired to that unit. MCAS seems to have been designed relying on two assumptions with regard to pilot response to erroneously high AOA: (1) If the pilot activates electric trim the column forces will be trimmed to (or near) zero; and (2) Repeated cycles of pilot trimming off column forces followed by automatic stabilizer control driving the stabilizer away from trim when flying at an otherwise steady condition would be recognized by the crew as errant auto stabilizer control action and treated in the same manner as runaway stab => pilot selection of stabilizer cutout via aislestand switches. I would imagine that the MCAS updates that are to be available soon design so as not to rely as much (if at all) on these two previous assumptions.

It is my understanding that MCAS can/will come active at AOA less than that for stick shaker in some configurations, but that MCAS will not be active at/below the AOA associated with any normal trim condition.

One of the objectives of MCAS is to recognize pilot activation of electric trim commands as indication that the crew is working to offload column forces. The pilot trim process is usually somewhat iterative with the flight crew activating trim for a period of time and then evaluating via continued manual flying through the column whether or not further refinement of the stabilizer position is needed. It seems reasonable to choose five consecutive seconds of no further pilot trim command input as indication that the pilot is satisfied with the trim and thus the column is at/near zero.
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Old 13th Mar 2019, 22:57
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So did FAA get this new data like Monday and sit on it?
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Old 13th Mar 2019, 22:58
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SLF here, please be gentle!
Too many pages, not enough time, but it seems to me that the MCAS is functioning solely on inputs about the attitude (AoA) of the airframe in one direction only. No attention appears to be paid to the position of the airframe in space - i.e. is altitude decreasing? AoA says nose is high but longitudinal gyro disagrees and says flight is level? Inertial Nav Systems have been around for a long time - back when I worked in the aviation industry. OK, that might be too expensive, but my yacht had a gyrocompass that cost about $100 as part of the autohelm. Why are these simple technologies not used for cross-checking of something mission critical like AoA? Before pushing the nose down, it would be helpful to know where it was pointing beforehand. And how could an automated system be allowed to drive the nose down while the altimeter shows altitude decreasing and acceleration increasing - the end result is inevitable!
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Old 13th Mar 2019, 23:07
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Originally Posted by FCeng84
MCAS does not use any equipment not already on the airplane, so nothing new to keep track of with regard to component failures. The manifestation of an MCAS failure would depend on the nature of that failure so hard to address that question without specifics. Lion Air discussion covers manifestation of MCAS response to an AOA sensor signal bias / failed high scenario.

As for the rationale behind basing MCAS on a single sensor, that is the default architecture for 737 with each FCC using only the sensors wired to that unit. MCAS seems to have been designed relying on two assumptions with regard to pilot response to erroneously high AOA: (1) If the pilot activates electric trim the column forces will be trimmed to (or near) zero; and (2) Repeated cycles of pilot trimming off column forces followed by automatic stabilizer control driving the stabilizer away from trim when flying at an otherwise steady condition would be recognized by the crew as errant auto stabilizer control action and treated in the same manner as runaway stab => pilot selection of stabilizer cutout via aislestand switches. I would imagine that the MCAS updates that are to be available soon design so as not to rely as much (if at all) on these two previous assumptions.

It is my understanding that MCAS can/will come active at AOA less than that for stick shaker in some configurations, but that MCAS will not be active at/below the AOA associated with any normal trim condition.

One of the objectives of MCAS is to recognize pilot activation of electric trim commands as indication that the crew is working to offload column forces. The pilot trim process is usually somewhat iterative with the flight crew activating trim for a period of time and then evaluating via continued manual flying through the column whether or not further refinement of the stabilizer position is needed. It seems reasonable to choose five consecutive seconds of no further pilot trim command input as indication that the pilot is satisfied with the trim and thus the column is at/near zero.
Can you provide a response to 1174 that would rule out that scenario?
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Old 13th Mar 2019, 23:07
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Originally Posted by Recidivist
AoA says nose is high
AoA doesn't tell you anything about pitch attitude, nor vice versa. Ask Air France.

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Old 13th Mar 2019, 23:08
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Looks like the last U.S. MAX to land with pax today is WN2569 OAK-EWR.

The other MAX's still up are two Air Canada's, three WestJet's and three Sunwings.


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Old 13th Mar 2019, 23:09
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Please sit back and relax - nothing could possibly go wrong go wrong go wrong ( that was in vogue in the 1960's on the Boeing SST program ...

meanwhile back at the ranch

Boeing 737 MAX - Differences

Maneuvering Characteristics Augmentation System (MCAS)

MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall. MCAS is activated without pilot input and only operates in manual, flaps up flight. The system is designed to allow the flight crew to use column trim switch or stabilizer aislestand cutout switches to override MCAS input. The function is commanded by the Flight Control computer using input data from sensors and other airplane systems.The MCAS function becomes active when the airplane Angle of Attack exceeds a threshold based on airspeed and altitude. Stabilizer incremental commands are limited to 2.5 degrees and are provided at a rate of 0.27 degrees per second. The magnitude of the stabilizer input is lower at high Mach number and greater at low Mach numbers. The function is reset once angle of attack falls below the Angle of Attack threshold or if manual stabilizer commands are provided by the flight crew. If the original elevated AOA condition persists, the MCAS function commands another incremental stabilizer nose down command according to current aircraft Mach number at actuation.
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Old 13th Mar 2019, 23:10
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SLF here, please be gentle!
Too many pages, not enough time, but it seems to me that the MCAS is functioning solely on inputs about the attitude (AoA) of the airframe in one direction only. No attention appears to be paid to the position of the airframe in space - i.e. is altitude decreasing? AoA says nose is high but longitudinal gyro disagrees and says flight is level? Inertial Nav Systems have been around for a long time - back when I worked in the aviation industry. OK, that might be too expensive, but my yacht had a gyrocompass that cost about $100 as part of the autohelm. Why are these simple technologies not used for cross-checking of something mission critical like AoA? Before pushing the nose down, it would be helpful to know where it was pointing beforehand. And how could an automated system be allowed to drive the nose down while the altimeter shows altitude decreasing and acceleration increasing - the end result is inevitable!
It is not as easy, remember there are a bunch of certification rules that basically require the algorithms to be simple enough and predictable enough.
The altitude does not change anything to the problem, you could be stalling when recovering from a descent if you pull the stick too much, in that case the airplane is still in descent. So you have to rely on the AOA. You cannot rely on the gyro because the angle of attack and the attitude are not the same thing, for example if you get a sudden strong updraft your angle of attack increases but your gyro does not show that change.

It is a complex problem. There are no easy solutions.
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