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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 14:19
  #1021 (permalink)  
Join Date: Nov 2018
Location: Brisbane
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Originally Posted by 22/04 View Post
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, 14:22
  #1022 (permalink)  
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BBC News reporting 'Black boxes to come to Europe' for expert analysis
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Old 13th Mar 2019, 14:24
  #1023 (permalink)  
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Stuck Vane

Originally Posted by xetroV View Post
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, 14:29
  #1024 (permalink)  
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Originally Posted by PiggyBack View Post
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, 14:30
  #1025 (permalink)  
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Originally Posted by hans brinker View Post
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, 14:31
  #1026 (permalink)  
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Boeing needs to provide that PFD AOA display for free.
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Old 13th Mar 2019, 14:32
  #1027 (permalink)  
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Originally Posted by TacomaSailor View Post
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 View Post
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 1Ĺ 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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Old 13th Mar 2019, 14:32
  #1028 (permalink)  
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BBC News reports that the recorders are being sent to a European agency for processing and analysis (presumably either the French BEA or UK AAIB). It also stated that the AAIB had been accredited to the investigation, so they may well go to Farnborough.

The NTSB, as a party to the investigation, had (not unreasonably) been pressing for the recorders to go to the USA, but despite their fierce independence from the FAA, it would seem that the latter's decision to allow continued operation of the Max in the USA (not to mention Trump's comments) may have had a bearing on the decision.
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Old 13th Mar 2019, 14:33
  #1029 (permalink)  
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Originally Posted by A30_737_AEWC View Post
Like you, I found myself perplexed by what a 'Continued Airworthiness Notice to the International Community' (CANIC) was supposed to be. I'd never heard of them before and there's not a register of them that I was able to find on the FAA website. I think it was rather telling that when I read about the 737 MAX CANIC in the media and tried to find a copy of it for myself, an FAA Twitter 'tweet' provided a link to the document. It hardly looks likes it's a legal airworthiness document (like an AD, NPRM, etc.). It sounds more like a 'child of the social media age' being promulgated by 'tweet' and being crafted by the 'brand managers' of the organisation whose product is found to be wanting in a crisis.
CANICs are not new. The FAA issues several of them each year, dating back maybe 10 years. It's part of an internal FAA communication process to give a "heads up" to other XAAs about an upcoming safety action, and may be issued prior (or concurrent to) an NPRM or an AD.
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Old 13th Mar 2019, 14:36
  #1030 (permalink)  
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Shouldn't they be on their way already? How long does this need to take? Aircraft are grounded because the crash circumstances are not enough known yet.
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Old 13th Mar 2019, 14:43
  #1031 (permalink)  
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Originally Posted by canyonblue737 View Post
"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.
Whilst that crew proved they could actually fly, they then made an appalling "airmanship" decision to fly hundreds of miles over high terrain to Jakarta with an effectively jammed stab and no autopilot instead of returning to the 10,000' RWY in Bali 20-30 nm away. Furthermore the incident was not fully written up in the tech log. Commercial pressure maybe....

At this point MCAS has NOT been implicated although something - voice reports from other aircraft indicate unreliable airspeed - happened. It seems probable they didn't even make flap retraction height (thereby discounting MCAS unless they retracted flaps below flap ret. ht.).

While we are waiting for some actual CVR/DFDR facts maybe you would like to read about Ethiopian's last 737 prang here: https://www.bea.aero/docspa/2010/et-...b100125.en.pdf which in one sentence can be summarised as: pilots can't fly.

I'll get on a Max tomorrow if flown by say, Southwest.
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Old 13th Mar 2019, 14:47
  #1032 (permalink)  
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Originally Posted by slip and turn View Post
Yes, Dave, that was an interesting graphic you posted but did not your plots only commence at the end of the runway?
I didn't include the ground roll in my graphic simply because my interest was in what happened from rotation onwards.

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?
Nothing so complicated.

The aircraft simply transmits either a Ground Position ADS-B message, which for obvious reasons doesn't need to contain an altitude, or an Airborne Position, which does.
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Old 13th Mar 2019, 14:47
  #1033 (permalink)  
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Originally Posted by A. Muse View Post
BBC News reporting 'Black boxes to come to Europe' for expert analysis
....And surprise, surprise.....

American air safety experts are trying to persuade their Ethiopian counterparts not to send the flight data to crash investigators in London, The Wall Street Journal reported. Instead, they want it examined by the National Transportation Safety Board in the United States.
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Old 13th Mar 2019, 14:52
  #1034 (permalink)  
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Wouldn't be surprised if the recorders are on their way to the BEA in Paris. The engines were half French.
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Old 13th Mar 2019, 14:52
  #1035 (permalink)  
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Originally Posted by ManaAdaSystem View Post

So the Americans have had 5 cases of control issues after takeoff on the MAX. At least two happened when they engaged the auto pilot.
There appears to be several issue with the MAX.
Only time before itís grounded world wide.
Here's a couple of extracts to look at

REPORT- trim after AP is turned on: December 2018

Noted on preflight, a write up, for a cycling trim situation on the inbound leg. With no faults noted by maintenance, it was cleared. First Officer (FO) and I discussed the situation as one of the threats possible, with emphasis on being alert for the cycling trim situation to possibly repeat. Reviewed applicable procedure for a possible runaway trim scenario. Upon takeoff, Autopilot A was engaged at approximately 1,200 FT AGL. As flaps were retracted and airspeed began to increase, additional trim inputs were immediately noticed by both pilots. With flaps now up, FMC called for 250 KTS. Aircraft pitched to 260 KTS with trim inputs, then re-pitched to 240 KTS. The trim system would activate for 1-2 seconds and then immediately reverse itself, trimming in opposite direction. I directed FO to ask for intermediate stop on climb, where we then stopped at FL230. Advised ATC we were experiencing a trim system problem, but the aircraft was stable and trim stopped fluctuating once a stable and level pitch was attained. I chose not to declare an emergency at this time as we did have a stable aircraft, but contacted dispatch via radio, and informed dispatcher of the situation, that it was a reoccurring event, and that I was not comfortable taking the aircraft to ZZZ1 with a primary flight control system not operating properly. Therefore I would return to ZZZ. Dispatcher brought Maintenance Control in I believe at that point and I gave them a description of the problem. We then completed those calls, informed ATC of our desire to return to ZZZ, and no emergency being declared at this time. The trim problem immediately reappeared when given a descent to 11,000, executed via Level Change on the Mode Control Panel. I was flying and at that point disconnected the autopilot, and hand flew the remainder of the approach to the landing. No trim problems were noted with autopilot disconnected. Maintenance ACARSed us several times, requesting us to attempt to troubleshoot the failure and gather information. I elected to not do this. I knew I had a failed trim system and did not wish to engage a deeper problem if something else went wrong with the system while troubleshooting. In addition we [were] now under 15000 FT, in the terminal area, and I was hand flying the aircraft. Too many distractions, as well as a potential bigger problem if something else went wrong. We both put on the table the trim motor / elevator jackscrew failure a few years back that happened to another carrier. That situation was perhaps the final reason I did not want to troubleshoot the failure. We finally told Maintenance Control via ACARS. "We are busy ", as they were now a distraction with their requests as we were near or under 10,000 FT. Aviate, Navigate, Communicate. That is what I start every brief off with a new pilot at the beginning of a trip.
REPORT- trim after AP is turned on: November 2018

It was day three of six for me and day three with very good FO (First Officer). Well rested, great rapport and above average Crew coordination. Knew we had a MAX. It was my leg, normal Ops Brief, plus I briefed our concerns with the MAX issues, bulletin, MCAS, stab trim cutout response etc. I mentioned I would engage autopilot sooner than usual (I generally hand fly to at least above 10,000 ft.) to remove the possible MCAS threat.

Weather was about 1000 OVC drizzle, temperature dropping and an occasional snow flake. I double checked with an additional personal walkaround just prior to push; a few drops of water on the aircraft but clean aircraft, no deice required. Strong crosswind and I asked Tug Driver to push a little more tail east so as not to have slow/hung start gusts 30+.

Wind and mechanical turbulence was noted. Careful engine warm times, normal flaps 5 takeoff in strong (appeared almost direct) crosswind. Departure was normal. Takeoff and climb in light to moderate turbulence. After flaps 1 to "up" and above clean "MASI up speed" with LNAV engaged I looked at and engaged A Autopilot. As I was returning to my PFD (Primary Flight Display) PM (Pilot Monitoring) called "DESCENDING" followed by almost an immediate: "DONT SINK DONT SINK!"

I immediately disconnected AP (Autopilot) (it WAS engaged as we got full horn etc.) and resumed climb. Now, I would generally assume it was my automation error, i.e., aircraft was trying to acquire a miss-commanded speed/no autothrottles, crossing restriction etc., but frankly neither of us could find an inappropriate setup error (not to say there wasn't one).

With the concerns with the MAX 8 nose down stuff, we both thought it appropriate to bring it to your attention. We discussed issue at length over the course of the return to ZZZ. Best guess from me is airspeed fluctuation due to mechanical shear/frontal passage that overwhelmed automation temporarily or something incorrectly setup in MCP (Mode Control Panel). PM's callout on "descending" was particularly quick and welcome as I was just coming back to my display after looking away. System and procedures coupled with CRM (Resource Management) trapped and mitigated issue.

From FO perspective
Day 3 of 3 departing in a MAX 8 after a long overnight. I was well rested and had discussed the recent MAX 8 MCAS guidance with the Captain. On departure, we had strong crosswinds (gusts > 30 knots) directly off the right wing, however, no LLWS or Micro-burst activity was reported at the field. After verifying LNAV, selecting gear and flaps up, I set "UP" speed. The aircraft accelerated normally and the Captain engaged the "A" autopilot after reaching set speed. Within two to three seconds the aircraft pitched nose down bringing the VSI to approximately 1,200 to 1,500 FPM. I called "descending" just prior to the GPWS sounding "don't sink, don't sink." The Captain immediately disconnected the autopilot and pitched into a climb. The remainder of the flight was uneventful. We discussed the departure at length and I reviewed in my mind our automation setup and flight profile but can't think of any reason the aircraft would pitch nose down so aggressively.
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Old 13th Mar 2019, 14:56
  #1036 (permalink)  
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Originally Posted by jimjim1 View Post
Let someone else's fingers do the walking

"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"]
Amazing reading.

Basically what it confirms is that for competent well rested crews the potential MCAS issues are a minor speed bump. Doesn't mean that it isn't a very real issue but the bottom line specific to Lion Air is simple and compelling....crew error. As for the current tragedy we really don't know enough but it doesn't have any of the trim related oscillation seen in Flight 610...

At some point the various regulatory agencies will need to figure it out.
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Old 13th Mar 2019, 15:04
  #1037 (permalink)  
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From Positive Rate
Here's a couple of extracts to look at
Interesting that there are other trim problems than MCAS for the Max8. Neither of the ASRS reports would be due to MCAS as they occurred with autopilot engaged and MCAS is disabled when autopilot is engaged.
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Old 13th Mar 2019, 15:11
  #1038 (permalink)  
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interesting speculation from reddit thread

I just read an interesting post on the reddit 737 MEGA Thread about possible internal Boeing reports on the AOA/MCAS failure. Not that reddit can be trusted as 'professional' source of information, but now days anything seems to be fair game as far as where valid info might pop up...
Some info leaking down the engineering community grapevine, I have it second hand from a buddy working for one of the subcontractors, reportedly a memo was circulated internally at Boeing as early as AUG 2018 of potential failure modes tied to MCAS-AOA programming logic[...]
Take if for what it is, but am curious if any of the experts might chime in to the plausibility of the failure mode talked about?
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Old 13th Mar 2019, 15:12
  #1039 (permalink)  
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Originally Posted by SLFinAZ
Amazing reading.

Basically what it confirms is that for competent well rested crews the potential MCAS issues are a minor speed bump. Doesn't mean that it isn't a very real issue but the bottom line specific to Lion Air is simple and compelling....crew error.
Yeah right. Give someone a dog that wants to bite and don't tell them about Gnasher's habit, then blame them when the dog actually does bite.
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Old 13th Mar 2019, 15:14
  #1040 (permalink)  
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Originally Posted by JamesT73J View Post
I think in the case of the Lion Air flight, the preceeding crew had little problem dealing with abnormal MCAS trim intervention.
By "little problem" you mean fighting against MCAS for about 5 minutes, just like the next crew, before using the cutoff switches? Because that's what the released FDR traces from the previous Lion Air flight show.
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