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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 12:31
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ICAO Annex 13 ? The number of important (based on their fleets) countries clearly not or hardly reporting is now more than a handful. In the philosophy of Annex 13 and general safety experience we know that this is deterimental to safety. Appears we are going back in time and ... there is no international discussion about this ... One thing that might help is that people dont fly with airlines from countries that dont report.

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Old 13th Mar 2019, 12:33
  #1002 (permalink)  
 
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Regarding normal clean up altitude

FWIW. Clean up altitude is based upon two primary considerations, safety and noise abatement and secondarily, economy. 800 to 1000 foot clean up altitudes have been traditionally, the selected safety compromise. The best configuration for an aircraft with a failed engine, airborne, is clean. So, we want to get to clean as soon as it is safely possible. Noise abatement considerations can raise the cleanup altitude and because we are gaining altitude instead of speed, it is not much of a safety concession. Instrument departure procedures may also influence configuration because turn radius, at a max 30 degree bank angle, is a function of speed. So, slower leading edge out turn, is a tighter turn.

all that said, in an emergency, especially day, vmc, no obstacles, you do what you have to do. Cleanup may be 500 to 600 feet agl.

sorry for the pedantry but there are clearly many here who do not understand these matters.


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Old 13th Mar 2019, 12:45
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Does anyone have any information on instances of irregular MCAS activation that have been successfully handled?
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Old 13th Mar 2019, 12:51
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CVR abnd DFDR sent to Europe?

According to French media FranceInfo, CVR abd DFDR will be sent to Europe for analysis. Country hasn't been decided yet
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Old 13th Mar 2019, 12:52
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"Does anyone have any information on instances of irregular MCAS activation that have been successfully handled?"

The day prior to the Lion Air crash the accident aircraft suffered from MCAS activation due to the faulty AOA. The Captain of that flight ran the runaway stabilizer procedure and cutout the stab trim and then was able to complete the flight normally. As far as I know no MAX aircraft has had a MCAS activation since the Lion Air crash until (potentially, there is only tenuous circumstantial evidence at this point) the Ethiopian accident.
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Old 13th Mar 2019, 12:52
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Originally Posted by Loose rivets
Debris, personal items, BEFORE impact. This would surely change everything? Unless violent stresses on the airframe were so great the structural integrity had been compromised.
Just a thought RE: eye witness accounts of smoke, debris, strange noises etc.

The last FR24 data point has the A/C at 383kts GS. At 8000' that's 339kts EAS (assuming still air) which is perilously close to Vmo (Not sure exactly for the MAX but I believe 340kts for the -800)
They apparently flew for a good 3 mins or so after this, so could well have exceeded Vmo, at which point you're liable to start having parts falling off your A/C, particularly given the unusual loading state with fluctuations in the Vertical speed.

This could account for the eye witness accounts and potentially the eventual complete loss of control and crash, whatever it was that caused them to get in this sorry position in the first place (I know what my money's on).
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Old 13th Mar 2019, 12:54
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Originally Posted by bauble
Does anyone have any information on instances of irregular MCAS activation that have been successfully handled?
I think in the case of the Lion Air flight, the preceeding crew had little problem dealing with abnormal MCAS trim intervention.



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Old 13th Mar 2019, 12:56
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Originally Posted by bauble
Does anyone have any information on instances of irregular MCAS activation that have been successfully handled?
We only have two confirmed instances of MCAS activation ever. JT 610 (not handled) and the flight immediately preceding it (handled).

MCAS is only supposed to operate well outside the normal flight envelope.
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Old 13th Mar 2019, 12:57
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Originally Posted by bill fly
So the AoA Sensor is usually a pretty rugged piece of kit.
What could cause it to fail?
Either the output has an anomaly (electrical/electronic side) or there is a mechanical problem (vane stuck).
What could cause a vane to stick?
Fine sand? Volcanic ash?
Where did this happen?
We had a stuck vane happen on one of our NGs just a few weeks ago due to a birdstrike.
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Old 13th Mar 2019, 13:08
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Thank you, I knew about the flight preceding JT610. Would other instances be widely known of? Operator tech log reports and incident reports would follow and probably local regulator incident reports. None of this would be publicly available though.
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Old 13th Mar 2019, 13:09
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Originally Posted by DaveReidUK
The public search engine on the ASRS is dire (hopefully airline safety departments have better access), so I've only been able to find one of those incidents so far:
Let someone else's fingers do the walking

https://www.documentcloud.org/docume...-737-max8.html
https://assets.documentcloud.org/doc...r-737-max8.pdf
"Contributed by: Cary Aspinwall, The Dallas Morning News"
HTML has some summary material (metadata) not in the pdf.

ASRS Reports for 737 max8
A 737 Max 8 captain noted problems on takeoff
An unidentified captain says the Airworthiness Directive does not address the problem in November 2018.
An airline captain called the flight manual for the Boeing 737 Max 8 "inadequate and almost criminally insufficient."
A co-pilot reported an altitude deviation in November.
Co-pilot said after engaging autopilot, aircraft pitched nose down.
Co-pilot reported that aircraft pitched nose down on departure.
A Boeing 737 Max 8 goes nose down suddenly during takeoff, pilot reports incident.


I have recently found bing search to be worth a look. Google finds it too.
[asrs database "max 8"]
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Old 13th Mar 2019, 13:09
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Originally Posted by Cleared Visual
Although I am not a pilot, I have some experiencing in testing (non aviation) automated systems and have seen some poorly written code before. I think Silverstrata summed up a simple fix that might be a step in the right direction.
I am responsible for developing safety related systems and although the 'spirit' of the suggestion may be sensible even a simple fix is actually more complex and requires more consideration than is immediately obvious. The MCAS feature is important for safety so adding code that can disable shoudl not be done without careful consideration. It will double the probability of a failure although making teh failure behaviour different (disabled). Should the pilot be warned it is disabled ? if so in what manner and under what conditions?

The actual code is not as straightforward as suggested. The two AoA sensore will frequently not read exactly the same and the readings wil be noisy so when they are compared the output of each AoA sensor must be filtered and the comparison must allow a tolerance window. What if the disagreement is intermittant? Should the system reenable itself or stay off?

We should consider other solutions for example limiting the maximum trim that can be applied or considering the state of other controls. The point is to select a solution which is safe under normal and forseeable fault conditions. The impact on teh pilots and general human factors under normal and fault conditions also have to be considered. The first solution we think of maybe a good one but we can't afford to make changes without making sure everything has bene considered.
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Old 13th Mar 2019, 13:11
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What would happen with a stuck stab (combined with MCAS triggering (or vice versa) ) ... loads of (as yet unanswered) questions that you hope were answered during the design, test and certification process ...
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Old 13th Mar 2019, 13:19
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Originally Posted by 22/04
To restore confidence in the aircraft - what?

Three AOA sensors inputting to MCAS two of which must agree.

Limitation to the forward trim provided by MCAS?

They would do it for me. How difficult/expensive to fit/retrofit.
The AoA vanes on each side of the nose are not really two redundant sensors requiring a third to failsafe the system. This is because you don't necessarily expect them to agree during maneuvering, especially with a yaw component, They are kind of like 1.5 sensors, because there could be some consistency detection between them (i.e. they can't be very different over time), which could be used to improve the input side of MCAS. For the kind of redundancy I think you are suggesting, you would need 3 vanes per side.
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Old 13th Mar 2019, 13:22
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BBC News reporting 'Black boxes to come to Europe' for expert analysis
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Old 13th Mar 2019, 13:24
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Stuck Vane

Originally Posted by xetroV
We had a stuck vane happen on one of our NGs just a few weeks ago due to a birdstrike.
Thanks Xetro,
What I was getting at was the environment before the takeoff/last landing.
I just wonder what could get into a vane bearing. There may be dust of various origins at both the takeoff sites where the Max fights crashed.
For the crew dealing with a jam, the reason for it is secondary, except that a bird strike could be noticed at the time of failure.
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Old 13th Mar 2019, 13:29
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Originally Posted by PiggyBack
The actual code is not as straightforward as suggested. The two AoA sensors will frequently not read exactly the same and the readings wil be noisy so when they are compared the output of each AoA sensor must be filtered and the comparison must allow a tolerance window. What if the disagreement is intermittant? Should the system reenable itself or stay off?
One would think that your line of thinking was pursued in considerable depth before implementing that system. (Only those involved in it will know).
I have had the opportunity in the last decade to participate in safety of flight component redesign IPTs. As you say it's not quite as simple as it sounds.
When you take something that has already been subjected to a variety of optimization and design constraints, and decisions, the amount of design space/room for revision shrinks considerably. (While my most recent experience was with hardware, not software, back when it was software (not flight systems software) the problem is as thorny for different reasons.
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Old 13th Mar 2019, 13:30
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Originally Posted by hans brinker
There is no control column cutout switches, but the trim control on the control column will stop and override MCAS for 5 sec. There are trim cutout switches on the pedestal that stop MCAS permanently.
There are control column cutout switches on the 737.

They are buried under the floor and simply prevent a pilot from trimming against the yoke. ie. you can't pull on the yoke and trim nose down or push on the yoke and trim nose up. And these switches are overridden by the STAB TRIM override switch on the Aft Electronic Panel.
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Old 13th Mar 2019, 13:31
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Boeing needs to provide that PFD AOA display for free.
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Old 13th Mar 2019, 13:32
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Originally Posted by TacomaSailor
Non-pilot but expert number cruncher with a basic questions about the DATA shown in post 69 and several prior to that.

Looking at the ADS-B numbers, in ascending time sequence from the start of the takeoff roll at 05:38:01Z, I see:

18 seconds with 0 elevation gain (to 7,200') and acceleration from 0 to 93 knots (ETH-302 still on the runway?)
5 seconds with 25' elevation gain (to 7,225') and acceleration from 93 to 105 knots (ETH-302 still on the runway?)
11 seconds with 00' elevation gain (to 7,225') and acceleration from 105 to 154 knots
11 seconds with 25' elevation LOSS (to 7,200') and acceleration from 154 to 183 knots (did ETH-402 try to lift off runway and then settle back on to it?)
14 seconds with 25' elevation gain (to 7,225') and acceleration from 183 to 200 knots

59-seconds after beginning the takeoff roll - the plane was at 200-knots and had gained NO altitude above the runway (based on elevation at 105-knots). Is that possible?

At 59-seconds there could not be much of the ~12,465' runway left ahead of the plane since it had been doing an average of 150-knots (250 fps) for 33-seconds (8,250') and had travelled about 3,000' accelerating in the first 26-seconds.. At what point would the takeoff be rejected? Or is this just a normal takeoff at a hot and high airport?

I assume MCAS could not have been active during the first 60-seconds of the takeoff event.
Originally Posted by DaveReidUK
The aircraft was approximately 125' AAL (7750' AMSL) at the 59 second point (05:38:59Z). See the profile I posted a couple of days ago, where the altitudes are drawn to scale.
Yes, Dave, that was an interesting graphic you posted but did not your plots only commence at the end of the runway? Indeed, the 7750' AMSL plot is some 1600 feet beyond the 25L landing threshold if the position reports are to be believed, and due to a fairly marked dip in terrain beyond that per Google Earth, a true AGL may have been nearer 175'. But have you tried plotting the take-off roll? Clearly the simple ADS-B "on_ground" algorithm used on ET302 to determine ground/airborne status was auto-switched to "airborne" earlier in the take off roll when ET302 had not yet actually become airborne as it was only registering 93kts in a possible 10kt headwind. Nothing unusual about the early ADSB switching, but given the confirmatory and accurate ADSB pressure altitudes transmitted thereafter, which seemingly correctly did detect the slight 20 foot rise in the first half of the runway, I found myself asking the same question as Tacoma Sailor about whether a rotation may have been attempted which resulted in that 7250' pressure altitude transmission at 05:38:45Z.798, and the strange 7075' just 1 seconds later.

Tacoma Sailor also seems to be right with his suggestion that at 59 seconds into the roll, ET302 must surely have been near the end of the runway - indeed (again if the ADS-B position reports can be believed) it seems it was 1600 feet beyond 25L landing threshold and with no paved area remaining beneath it.

There will be eventual explanations for all the numbers, but like Tacoma Sailor, I'm intrigued by those transmitted from the runway.

One question about how the transmitted pressure altitude is auto-calibrated prior to flight. Clearly a complex aircraft like this on the ground at a well charted licensed airfield knows exactly where it is and at what altitude, so does it continuously calibrate itself whilst it is on the runway up to the point WOW and groundspeed, and GPS data tell it it may be airborne?
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