Go Back  PPRuNe Forums > Flight Deck Forums > Rumours & News
Reload this Page >

Ethiopian airliner down in Africa

Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

Ethiopian airliner down in Africa

Old 14th Mar 2019, 01:26
  #1261 (permalink)  
 
Join Date: Nov 2018
Location: Brisbane
Posts: 19
Now that this is a huge international news story, it's interesting to see the developing outside media opinion/current consensus.

One very commonly expressed thread is that the probable JT610, possible ET302 accident cause is new overcomplicated automation confusing pilots (this is similar to Trump's Tweet also).

But interestingly this is actually the opposite of the MCAS issue. The MCAS algorithm appears much too simple for it's power, primarily taking a single AoA vane input without consistency checks, and applying them to the stabilizer periodically with no limit except when maximum downtrim is reached. Automation simplicity is one approach to reducing failure modes, but within reason as demonstrated in this case.
LEOCh is offline  
Old 14th Mar 2019, 01:33
  #1262 (permalink)  
 
Join Date: Dec 2014
Location: Nz
Posts: 274
I think it is common for those who don’t fly Airliners, and also for those with only one or two years experience on them, to underestimate the effect of contradictory information being presented on the Primary Flight Displays.
For me, just when I thought I was a gun at flying appropriate thrust settings and attitudes during simulated Airspeed Unreliable scenarios, just as my confidence was peaking ( about six years on the NG after ten years on turbo-props), I was presented with a pitot-static issue on departure ( in the sim) that really had me struggling to know what was right. With the machine blaring WINDSHEAR WINDSHEAR WINDSHEAR while the stick shaker rattled away and the IAS was a moderately believable number......what to do? Is the WINDSHEAR real and I need to pitch to 15 etc etc or is the stickshaker real and I need to reduce pitch etc? Here come the Pitch Limit Indicators, gotta respect them right? They’re now down at 6 degrees nose up......
I managed to sneak away with it because of good support from my First Officer but it has given me a reality check with regard to the effects of contradictory information being presented when in IMC. I am now quicker to check my First Officers screen and I am also more aware of when Winshear is simply not going to be possible.
My point though, is that the machine (NG sim) applied no nose down trim, even without the machine applying nose down trim it can be very very challenging to apply sensible attitudes and thrust settings in real time as an event of this nature unfolds.
With unexpected and potentially unknown flight control inputs taking place in conjunction with contradictory information being presented one would hope to be in VMC with an excellent horizon.
Just my thoughts for those who think it is as simple as setting 10/80 and calling for the stab trim cutout switches to be operated.
73qanda is online now  
Old 14th Mar 2019, 02:07
  #1263 (permalink)  
 
Join Date: Dec 2003
Location: On a different planet, so it appears...
Posts: 43
Originally Posted by wrench1 View Post
“These knobs don't seem to work in flight. The First Officer offered to hit the SEL function in flight, to test it out, but I thought something irreversible or undesirable might happen (not knowing what we were actually selecting), so we did not try it out in flight.”

SERIOUSLY????????
speedbirdconcorde is offline  
Old 14th Mar 2019, 02:28
  #1264 (permalink)  
 
Join Date: Apr 2008
Location: Paris
Age: 69
Posts: 246
At some point somebody is going to have to check in the sim how effective the Boeing procedures are in practice, and how many AoA sensor failures out of a hundred would end up underground.

Edmund
edmundronald is offline  
Old 14th Mar 2019, 02:33
  #1265 (permalink)  
 
Join Date: Dec 2014
Location: Nz
Posts: 274
At some point somebody is going to have to check in the sim how effective the Boeing procedures are in practice, and how many AoA sensor failures out of a hundred would end up underground.
Easier said than done. To get a realistic idea you would have to choose pre rostered Capt/FO combinations from all sorts of different training backgrounds and they would have to have no idea what was about to happen.
73qanda is online now  
Old 14th Mar 2019, 02:35
  #1266 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 5,115
Thumbs up

Originally Posted by gums View Post
Salute MJB !!

..... snip

A pure FBW control system has all the "protections" and limits/warnings and such as part of the basic design. But no FBW commercial airliner has failed to meet the basic aerodynamic requirements for stability and control if they all had ropes, levers, pulleys, cables, torque tubes, etc to move the ailerons, rudder and elevator. They are not the military or utility platforms and do not haul 200 folks about to visit aunt Clara.
So Boeing adds another thingie besides the STS speed stability doofer to meet Part 25 requirements and it gets signed off. Most of we pilots would handle the new thingie if and a BIG IF we knew it was added AND we were told what possibel failure indications existed AND we practiced a bit. GASP!! None of that was done.
My experience was in military planes and before each flight we had to sign off every little notice, directive and change and such before flying. On some mods we had to fly with an instructor before being cleared "solo". The MCAS mod required none of those things, and I have problems with not having seen a revolt by a thousand 737 pilots that only discovered MCAS after Lion 610 pranged.

'nuff bitching, and I close for now

Gums
A salute back to you

You point to a problem which i whole heartedly agree.

Now can you also point to a solution in commercial service among the various nations flying these aircraft?
lomapaseo is offline  
Old 14th Mar 2019, 02:55
  #1267 (permalink)  
 
Join Date: Aug 2001
Location: The wrong time zone...
Posts: 646
Originally Posted by 73qanda View Post

Easier said than done. To get a realistic idea you would have to choose pre rostered Capt/FO combinations from all sorts of different training backgrounds and they would have to have no idea what was about to happen.
Not only that, but you have to be sure the sim accurately represents what happens with such failures in the real aircraft - for a "behind the scenes" system such as MCAS, this is NOT guaranteed - yet.
josephfeatherweight is offline  
Old 14th Mar 2019, 03:15
  #1268 (permalink)  
 
Join Date: Feb 2008
Location: PARIS
Posts: 7
BFU, Bundesstelle für Flugunfalluntersuchung, repeat afer me !

It seems that the German bureau of accident analysis refuses to receive the CVR/FDR from request of Etiopia... (BFU, Bundesstelle für Flugunfalluntersuchung, repeat afer me !)
So, the french BEA (= AAIB or NTSB or ATSB) will take care of this...

I'm not authorized to post a link/url, but search for :

francetvinfo.fr crash-aerien-en-ethiopie-les-boites-noires-seront-analysees-en-france on Google...
Condor99 is offline  
Old 14th Mar 2019, 03:20
  #1269 (permalink)  
 
Join Date: Feb 2009
Location: Seattle
Posts: 379
Originally Posted by positiverate20 View Post
I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.

In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.

Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place! So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is. Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes. By the time he actually realises how out of trim he is, he's doing 350, and despite the stab still being at the same X° nose down since cut-out, the forces have multiplied. Now if there is any nose down attitude or reduction in power then there's absolutely no chance to recover.

Obviously all hypothetical, an airspeed disagree on takeoff could lead to circumstances similarly, or a multitude of other possible reasons, however, in the situation that I've hypothesized, it would almost certainly always end in a similar steep nose down attitude.
737 is not a FBW system with augmented elevator control. The elevator follows only the column. The pilot will know at all times when flying manually just how out of trim the airplane is by how much column force/displacement is needed to maintain the target pitch attitude. Having shut off electric stabilizer control, the workload associated with maintaining pitch trim is increased as it requires manual, mechanical rotation of the trim wheel, but the cues as to when trim is needed, in which direction, and how much are the same as what the pilot has seen for every hour of flying that airplane manually that he or she has done. As with every day flight with a completely healthy airplane, the amount of pitch trim required to recenter the column after having used that column to compensate for the pitching moment changes associated with thrust and configuration changes will be no different and thus the cue to provide pitch trim will be no different. The task of inserting that trim is higher workload, but nothing any 737 pilot (MAX or otherwise) should find particularly difficult to keep up with.

From your mention of "autotrim" I get the sense that you may not realize that when flying the 737 manually the automatic stabilizer control functions that are active (STS and MCAS) tend to drive the stabilizer away from trim thus making the pilot trim workload higher than it would be without them. The automatic stabilizer control is not there to "automatically trim the stabilizer". It is in fact there to "automatically untrim the stabilizer" such that the pilot has to provide column in the opposite direction yielding handling qualities and awareness that are dictated by the FARs.
FCeng84 is offline  
Old 14th Mar 2019, 03:21
  #1270 (permalink)  
 
Join Date: Sep 2016
Location: USA
Posts: 438
Originally Posted by positiverate20 View Post
I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.

In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.
Trimming the plane for neutral stick force is part of safely trying to get back to the ground. This is a fundamental airplane flying concept since the 172 presolo days. Literally lesson one. At what point does this get lost? Are you seriously proposing that someone cease trimming since the emergency checklist does not say to trim? What about the fact that the emergency checklist doesn't say to use the ailerons to turn back toward the airport, what do you do then? Say well we're stuffed now, we're out of options, we have to take whatever is straight ahead?

Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place!
NO! As multiple people including FCEng have explained multiple times, this is not why MCAS is required!

So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is.
I'm not following. If there's a neutral stick force given all the current pitch moments (including the thrust couple) then it is, by definition, in trim. If thrust is reduced then it well get out of trim toward nose down (stick force to hold steady pitch will become a pull)

Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes.
You're joking, right? This has to be a joke.
Vessbot is online now  
Old 14th Mar 2019, 03:37
  #1271 (permalink)  
 
Join Date: Apr 2008
Location: Paris
Age: 69
Posts: 246
Before the damages trials for Indonesian and Ethiopian take place, someone is going to have to run through a bunch of these scenarios in the sim, and see in what percentage of a few hundred trials of AoA sensor faults the pilots manage to survive even if they apply all recommended Boeing procedures.


Edmund
edmundronald is offline  
Old 14th Mar 2019, 03:40
  #1272 (permalink)  
 
Join Date: Feb 2009
Location: Seattle
Posts: 379
Originally Posted by jimtx View Post
Just trying glean what flight regime MCAS needs to protect. So, they didn't want the column cutout switch to work because they envisioned pulling hard and not trimming. Trimming would normally return the column to neutral. Two things come to mind. Windshear escape in the clean config and steep turns with guys that don't trim. I (having the T-38 training mantra embedded, "trim trim trim") would trim during steep turns so that would not be a problem for me or MCAS. Of course steep turns are a simulator exercise so not really relevant. Again I ask why put out the original AD and not caution about being careful when pulling with the loss of MCAS.
Handling qualities regulations require starting from a wings level, trimmed condition and then demonstrating flying to high AOA (both by slowing and by executing a wind-up turn at constant speed) and showing that the stick force throughout the maneuver (flown without trimming) increases monotonically (i.e., the required pull does not decrease throughout the maneuver). These maneuvers involve insertion of enough aft column to go past the column cutout switch and thus MCAS must be able to continue to add airplane nose down stabilizer with the column pulled past the position of this switch.

On a side note I have always been told that trimming into a steep turn maneuver is a recipe for trouble. When you trim into a maneuver you increase your available control power in the direction of the maneuver, but reduce the available control power in the opposite direction. If you trim into a steep turn with a forward CG airplane you may find that you have to push like crazy when you exit the maneuver and level out. If, by bad luck, your trim device (horizontal stabilizer in the case of a 737) were to get stuck in the position to which it was moved to trim into a maneuver you might find it hard to get home. On all commercial transports that I know of the elevator is sized to provide continued safe flight and landing starting from any normally encountered stabilizer position, but that assurance would not be preserved if it were routine practice to trim into maneuvers.
FCeng84 is offline  
Old 14th Mar 2019, 04:00
  #1273 (permalink)  
 
Join Date: Feb 2008
Location: PARIS
Posts: 7
CVR/FDR

Where are the CVR/FDR boxes right now ?

Who knows ?
Condor99 is offline  
Old 14th Mar 2019, 04:01
  #1274 (permalink)  
 
Join Date: Mar 2004
Location: Somewhere Over America
Posts: 190
Sooooooooooooo when will they release a transcript of the CVR from the Lion Air crash?
Halfnut is offline  
Old 14th Mar 2019, 04:18
  #1275 (permalink)  
 
Join Date: Sep 2018
Location: Laredo, TX
Posts: 95
Originally Posted by FCeng84 View Post
Handling qualities regulations require starting from a wings level, trimmed condition and then demonstrating flying to high AOA (both by slowing and by executing a wind-up turn at constant speed) and showing that the stick force throughout the maneuver (flown without trimming) increases monotonically (i.e., the required pull does not decrease throughout the maneuver). These maneuvers involve insertion of enough aft column to go past the column cutout switch and thus MCAS must be able to continue to add airplane nose down stabilizer with the column pulled past the position of this switch.

On a side note I have always been told that trimming into a steep turn maneuver is a recipe for trouble. When you trim into a maneuver you increase your available control power in the direction of the maneuver, but reduce the available control power in the opposite direction. If you trim into a steep turn with a forward CG airplane you may find that you have to push like crazy when you exit the maneuver and level out. If, by bad luck, your trim device (horizontal stabilizer in the case of a 737) were to get stuck in the position to which it was moved to trim into a maneuver you might find it hard to get home. On all commercial transports that I know of the elevator is sized to provide continued safe flight and landing starting from any normally encountered stabilizer position, but that assurance would not be preserved if it were routine practice to trim into maneuvers.
The T-38 did not have an elevator. It had a stabilator. But in all the other commercial transport aircraft I flew “trim trim trim” worked for me. Except for, thankfully, only in the simulator, stalls and wind shear events. But in any normal airline flying you woul expect to be in trim when sht happened. We don’t have “maneuvers” but if I did I would trim if I had an airplane that required it. I’m supposing that some current aircraft don’t require trim. I could adapt to that. There might be that some guys can’t adapt, old to new, young to old, not capable to required capable.

Last edited by jimtx; 14th Mar 2019 at 15:17.
jimtx is offline  
Old 14th Mar 2019, 04:32
  #1276 (permalink)  
 
Join Date: Jul 2007
Location: Hadlow
Age: 56
Posts: 587
Originally Posted by silverstrata View Post


i have had some dealings with transponders, and the rule of thumb is that.

Mode-c gives 1013 baro altitude.
Mode-s gives 1013 baro altitude.
Ads-b also gives 1013 baro altitude, to be compatible with the above.
Flarm and paw give gps altitude.

As far as i know, fr24 is simply picking up ads-b 1013 pressure altitudes, so you will need to know the qnh of the day, and the altitude of the airport, to calculate the true height of the aircraft. Transponders were designed for seperation on airways, not for separation with terrain, so the older units all used 1013 baro, and ads-b follows suit.

(if ads-b used gps alt, then atc would not be comparing like with like. However, newer systems like flarm and paw can happily use gps alt, because they all use gps, so they are comparing like with like.)

silver

metar HAAB 100500Z 06008KT 9999 FEW025 16/10 Q1029

Airfield elevation 2,334m / 7,625 ft

Last edited by Super VC-10; 14th Mar 2019 at 04:35. Reason: + airfield elevation
Super VC-10 is offline  
Old 14th Mar 2019, 05:44
  #1277 (permalink)  
 
Join Date: Feb 2008
Location: PARIS
Posts: 7
Crash in Ethiopia: Germany can not analyze black boxes
http http://www.bfmtv.com/economie/crash-...noires-1651600 . html

Condor99 is offline  
Old 14th Mar 2019, 05:52
  #1278 (permalink)  
 
Join Date: Dec 2013
Location: Weltschmerz-By-The-Sea, Queensland, Australia
Posts: 680
Originally Posted by Condor99 View Post
Crash in Ethiopia: Germany can not analyze black boxes
http http://www.bfmtv.com/economie/crash-...noires-1651600 . html
Dead link, but the gist of a google search using those terms is that Germany currently lacks the ability to assess this new version of the FDR. I do hope that there is a non-US avenue for analysis. I never used to feel that way, but lately I get to feeling a bit queasy getting between Americans and money.
Australopithecus is offline  
Old 14th Mar 2019, 05:58
  #1279 (permalink)  
 
Join Date: Feb 2008
Location: PARIS
Posts: 7
Originally Posted by Australopithecus View Post


Dead link, but the gist of a google search using those terms is that Germany currently lacks the ability to assess this new version of the FDR. I do hope that there is a non-US avenue for analysis. I never used to feel that way, but lately I get to feeling a bit queasy getting between Americans and money.
Just add ".html" to the link (I'm not yet authorized to post a link/url).

France (BEA) will be in charge to try to read these black boxes...
Not the best choice IMHO, but...


Condor99 is offline  
Old 14th Mar 2019, 06:17
  #1280 (permalink)  
 
Join Date: Mar 2014
Location: PRM, AA Prelature
Posts: 2
Originally Posted by Condor99 View Post
Just add ".html" to the link (I'm not yet authorized to post a link/url).

France (BEA) will be in charge to try to read these black boxes...
Not the best choice IMHO, but...
It's not like there won't be an FAA/NTSB team and Boeing reps in the room. I fail to see what the big deal is.
dfens42 is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.