Ethiopian airliner down in Africa
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Information is slow in coming. Eye witness statements of articles and debris falling from the aircraft before final impact should have been confirmed, if true, by recovery of such material. Important question for news media covering the accident; did the aircraft strike anything between takeoff and final resting place? Where was the first item belonging to the aircraft found? If there is any validity to the ads-b data, there was a lot of vertical oscillation close to the ground. It would be possible, admittedly unlikely, that the aircraft struck something prior to the final crash. It's is also possible for the witnesses to be wrong. In any case, there is already more information available to those that know what question to ask. For example, the photo circulating of one of the engines. Looks to have been turning at high speed when it hit the ground. Experts have already no doubt, a rough idea of the speed it was turning when it stopped.
Pressure is building over this accident. Information is not flowing and individuals and groups that are lobbying and withholding are going to suffer consequences.
Pressure is building over this accident. Information is not flowing and individuals and groups that are lobbying and withholding are going to suffer consequences.
Last edited by davionics; 13th Mar 2019 at 12:43.
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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.
Last edited by A0283; 13th Mar 2019 at 13:00.
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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.
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.
"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.
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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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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MCAS is only supposed to operate well outside the normal flight envelope.
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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?
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?
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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.
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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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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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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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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Stuck Vane
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.
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?
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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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.
