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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 18th Mar 2019, 00:34
  #1841 (permalink)  
 
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'
That they found it was necessary with 2,5 degrees might indicate that the aircraft might be way off the required natural stability without the help of any system.


nope- it is sufficiently stable without MCAS - which is why they only needed it for the extreme unlikely case which allowed them to use the non flight critical certification. The biggedst screw up was NOT limiting its use and allowing a single sensor to control over the normal pilot disconnect. for 737 and similar

read the seattle times article today
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Old 18th Mar 2019, 00:34
  #1842 (permalink)  
 
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Originally Posted by WHBM View Post
Apparently this is an additionally chargeable option. All three major US customers (Southwest, American, United) have bought it. Lion and Ethiopian did not. I wonder about others.

And I wonder how the Boeing sales team went about selling this add-on. Why did the US carriers spend the money and others not. Presumably the sales team offered it to everyone. What were their justifications, and why did the US carriers, no fools at tough negotiations, go for it but not others. And how did the FAA certification let it be optional rather than required. How often, for those that fitted it, did it operate ?
I wonder too about the sales process. It does seem a little odd that carriers in the domestic market opted for an extra element there was no obvious reason to buy (if they didn't know there was a software feature for which it was a single point of failure), while third-world airlines did not. Was it just cost-saving, or did Boeing push a little harder / offer discounts where failures were less likely to be written off as down to poor maintenance / airmanship?
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Old 18th Mar 2019, 00:47
  #1843 (permalink)  
 
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Thoughts on Seattle Times article published Sunday morning Seattle time

This article is generally well written and seems quite accurate. One point of clarification is that early on in the 737MAX development it was thought that MCAS would only be needed at particularly high Mach numbers. For those conditions the prediction was that the original 0.6 degrees of MCAS stabilizer authority would be sufficient. That proved to be pretty close to the case during flight testing and the final MCAS increment size for cruise and higher Mach numbers is very close to 0.6 deg. Later on it was determined that MCAS would also be needed at lower Mach numbers. With that extension of MCAS came the MCAS authority vs. Mach number schedule that is in the current design. The high Mach end of that schedule is approximately 0.6 degrees. Only with Mach Number less than 0.4 is the MCAS authority 2.5 degrees. The larger authority at lower Mach numbers is needed as the effectiveness of the horizontal stabilizer is less at lower speed. It is quite common that flight control functions are given higher authority at lower airspeed and less authority at airspeed increases.

A second point that did not come through particularly clearly in the Seattle Times article is that the pending MCAS software update has been in the works at Boeing since shortly after the Lion Air accident. As the data for the Ethiopian accident is not yet available (or maybe just came available) nothing that Boeing would be getting out the 737MAX fleet over the next couple of weeks could possibly be based on the most recent event. I'm sure that the team at Boeing will be evaluating the ET accident data as soon as they are able to see (1) if MCAS played any role in this accident, and (2) if MCAS did play a role, how would MCAS have behaved differently had the proposed updates been in place.
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Old 18th Mar 2019, 01:02
  #1844 (permalink)  
 
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But, I must say, if anyone trying his best to count the passes couldnt see the gorilla, then I think the expectatations on what a cockpit crew are able to do in a high stress situation with a lot of stuff going on in the cockpit has to be signifcantly decreased.
Scary indeed.
Rubbish analogy.

To make this video exercise more like the flight situation, change it to one where the viewer must count the number of passes, but then introduce an impediment that momentarily, but repeatedly, blocks his vision. Give the viewer a means to permanently remove the impediment.

Does the viewer realise that his view is being regularly blocked? Does he activate the removal option before time runs out?
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Old 18th Mar 2019, 01:05
  #1845 (permalink)  
 
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One interestingly thing from the Seattle article. The Lion air crew went through 21 MCAS cycles with the Captain retrimming each time. They did not disconnect the trim. The Captain handed the aircraft off to the FO who let the nose fall to far for recovery. The logbook entry from the prior flight should have mentioned the trim disconnect. I would presume Lion Air requires a log book review by each crew.
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Old 18th Mar 2019, 01:06
  #1846 (permalink)  
 
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Originally Posted by SteinarN View Post
I dont say it is an excuse, it certaintly is not an excuse.
But, imagine the pressure Boeing is under to get the Max certified and start delivering.
What would the reaction be if some low level engineers argued for work and modification 6 monts before planned first delivery that would delay certification and first delivery by 2 years, just to pick a number?
The stock would tumble, customers would be raging, top management would lose its bonuses.

I can easily see such a reason for some (semi) top level managers trying to get away with a quick and dirty trick to avoid all the problems following a lengthy delay.
Point well taken, but the complete lack of FAA oversight as well as such a rushed and incredibly flawed design are overwhelmingly bad here. Someone, one would expect, will take responsibility for the tragedies. (Having said that, these 'senior managers' are not renowmed for falling on their swords).
The fact is, the lack of alpha signal monitoring within MCAS is both alien to systems design and in my view is unforgivable
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Old 18th Mar 2019, 01:13
  #1847 (permalink)  
 
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FDR: Clear Similarities to Lion Air Crash

From The Washington Post:
March 17 ADDIS ABABA, Ethi*o*pia — *Ethiopia’s transport minister said Sunday that information from the flight data recorder on the Ethiopian Airlines jet that crashed last week shows “clear similarities” to the crash of the same type of plane in Indonesia in October.

Dagmawit Moges told journalists that the condition of the “black boxes” — the data and voice record — was good and that enough data had been recovered that her ministry’s Accident Investigation Bureau would release a preliminary report in 30 days on what happened to Flight 302.

“During the investigation of the FDR [flight data recorder], clear similarities were noted between Ethiopian Airlines Flight 302 and Indonesian Lion Air Flight 610, which will be the subject of further investigation,” Dagmawit said.
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Old 18th Mar 2019, 01:38
  #1848 (permalink)  
 
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The fact is, the lack of alpha signal monitoring within MCAS is both alien to systems design and in my view is unforgivable
Quite commonplace, really, for critical airborne systems to use only one sensor, and only raw data at that. Examples:

Turkish Airlines flight 1951, 25 Feb, 2009. B737-800 where one radar altimeter was malfunctioning. The data from the sensor went to zero, the computers thought the plane was on the ground, so they reduced the engine power to idle. The result was a stall at low altitude where many occupants were killed. The idiotic thing was that not only were the computers using just one radar altimeter sensor, they were making no effort to inspect it for reasonableness or filter it against spikes. The data was showing valid heights but then instantly started showing zeros!

Qantas flight 72, 7 Oct, 2008. Airbus A330. Pilot's side air data computer had a momentary spike in the angle of attack data. Silly computers took this as indicating the aircraft was suddenly stalling, and at a speed of about 450 knots, pushed the nose down. Passengers were thrown into the ceiling and many were seriously injured. The idiotic thing was that the computers were using completely raw data and could therefore believe that the angle of attack could, in the space of one second, change from sensible values to a stalling angle. Also idiotic that the computers would happily perform a manouever of such violence.

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Old 18th Mar 2019, 01:48
  #1849 (permalink)  
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Originally Posted by deltafox44 View Post
In this Airbus crash 2 out of 3 AoA sensors were frozen. The stall was NOT caused by faulty flight computers but was the result of the pilots voluntarily trying to stall the aircraft to "check" the AoA protection (which could not save them since sensors were frozen). At 2000 ft this is kind of a roulette russe
not being pedantic, just that A320’s incorporate a conventional cane AOA sensor, not a static pressure comparator type system, the vane has no way to be blocked, it can jam...
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Old 18th Mar 2019, 01:50
  #1850 (permalink)  
 
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Originally Posted by FGD135 View Post
Does the viewer realise that his view is being regularly blocked? Does he activate the removal option before time runs out?
Has anyone told him that there is a removal option?

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Old 18th Mar 2019, 01:53
  #1851 (permalink)  
 
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Originally Posted by SteinarN View Post
I dont say it is an excuse, it certaintly is not an excuse.
But, imagine the pressure Boeing is under to get the Max certified and start delivering.
What would the reaction be if some low level engineers argued for work and modification 6 monts before planned first delivery that would delay certification and first delivery by 2 years, just to pick a number?

I can easily see such a reason for some (semi) top level managers trying to get away with a quick and dirty trick to avoid all the problems following a lengthy delay.
But an aircraft company of such standing even a small one, should have processes in place such that the situation you describe, doesn't arrive.

Just as aerodynamic problems are best 'engineered out' so such a situation should have been 'managed out' as it arose... we're building aircraft here not widgets and even management always had that aviation ethos back in the day...

I'm getting flavours of VW diesel fuel here,.. and a certain trans Atlantic cynicism.
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Old 18th Mar 2019, 01:56
  #1852 (permalink)  
 
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Originally Posted by GroundedDinosaur View Post
If the MCAS isn't that important.... It can't be, because their was no mention of it in the extensive flight training that pilots received on it, according to
Boeing, it would just confuse them. So, why not just deactivate it, and have the planes fly merrily on their way? As all the 'other' 737's do. You don't think there might actually be a reason Boeing hasn't suggested this, do you?
Why not turn it off? When it would be off during a real abnormal you continue on your merry way with manual trim and no auto pilot and are not told to avoid any flight regime that MCAS was put in to protect.
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Old 18th Mar 2019, 02:02
  #1853 (permalink)  
 
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Originally Posted by Rananim View Post
I counted 14 and missed the gorilla.But thats not important.Whats important is that
Mullenberg doesnt miss the elephant in the room the next time round.
Boeing screwed the pooch on 3 counts:
-------->clandestine installation of MCAS
-------->MCAS activation based on single sensor
-------->failure to provide MAX simulators in good time for an aircraft whose differences cannot be trained on an ipad

Mullenberg is an MA in aeronautics and by all accounts a well-rounded guy.He has a good engineering background.
Hopefully hes the type who knows exactly whats going on on that assembly line and involved in the "nuts and bolts"
from the ground up.
The MAX can be safe,they just have to come clean and fix it.....and then win the flying public back again.I wish them
luck because in general they build great airplanes.
++++
Mullenberg is an MA in aeronautics and by all accounts a well-rounded guy.He has a good engineering background.
Hopefully hes the type who knows exactly whats going on on that assembly line and involved in the "nuts and bolts"
from the ground up.


I'm sure he will be first in line for
from WSJ

By
Andrew Tangel,Andy Pasztor andRobert Wall
March 17, 2019 8:20 p.m. ET The U.S. Department of Transportation is investigating the Federal Aviation Administration’s approval of Boeing Co.’s BA 1.52% 737 MAX jetliners, according to people familiar with the probe, an unusual inquiry into potential lapses in federal safety approvals for new aircraft.The inquiry focuses on a safety system that has been implicated in the Oct. 29 Lion Air crash that killed 189 people, according to a government official briefed on its status. Aviation authorities are looking into whether the anti-stall system may have played a role in last week’s Ethiopian Airlines crash, which killed all 157 people on board.
On Sunday, Ethiopia’s transport minister, Dagmawit Moges, said there were “clear similarities” between the two crashes. U.S. officials cautioned that it was too early to draw conclusions because data from the black boxes of the Ethiopian Airlines plane still need to be analyzed. . . .

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Old 18th Mar 2019, 02:04
  #1854 (permalink)  
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The Seattle Times article makes for very disturbing reading. Again, FCeng84's detailed clarifications have helped a lot.

In the article, one light-bulb moment for me was that the 'Resetting' of the MCAS was in fact a 're-datumizing', (my term) which allows one to understand the summed inputs reaching the end of the jackscrew.

EDIT, just noticed the quote by safelife back here.

Ethiopian airliner down in Africa


Talk about elephants in the room. I'd missed this entire page - see Ian W.



.
.

Last edited by Loose rivets; 18th Mar 2019 at 02:18.
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Old 18th Mar 2019, 02:07
  #1855 (permalink)  
 
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Has anyone told him that there is a removal option?
He would have to know there is such an option. Every Boeing airliner since the 1960's has had that option, and it has been in every checklist.

Was he aware of the option, and was it regularly trained, would be the questions I would be asking.
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Old 18th Mar 2019, 02:14
  #1856 (permalink)  
 
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Originally Posted by Rananim View Post
Mullenberg is an MA in aeronautics and by all accounts a well-rounded guy.He has a good engineering background.
I think you are talking about Dennis Muilenburg (not Mullenberg) who is the CEO of Boeing.
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Old 18th Mar 2019, 02:17
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Originally Posted by deltafox44 View Post
Except that A321 has 3 AoA probes, 2 of which were faulty, and the stall protection could be countered by aft stick (on mini-stick required force may not exceed pilot strength, contrary to a control column)
Actually the stall protection could not be countered by the sidestick in normal law. The pilots switched off two of the three ADRs giving them alternate law without stall protection (just speed stability).
This was at that point not a published procedure and it is very likely that lesser pilots with no technical backup from the company would not have successfully completed the flight.
Having said that, a 3 out of 2 voting system is vastly superior to alternating between AOA 1 and 2 as Boeing has done with MCAS.
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Old 18th Mar 2019, 02:17
  #1858 (permalink)  
 
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Originally Posted by FCeng84 View Post
Thoughts on Seattle Times article published Sunday morning Seattle time

A second point that did not come through particularly clearly in the Seattle Times article is that the pending MCAS software update has been in the works at Boeing since shortly after the Lion Air accident. As the data for the Ethiopian accident is not yet available (or maybe just came available) nothing that Boeing would be getting out the 737MAX fleet over the next couple of weeks could possibly be based on the most recent event. I'm sure that the team at Boeing will be evaluating the ET accident data as soon as they are able to see (1) if MCAS played any role in this accident, and (2) if MCAS did play a role, how would MCAS have behaved differently had the proposed updates been in place.
The FAA has stated that " The grounding will remain in effect pending further investigation, including examination of information from the aircraft’s [ET] flight data recorders and cockpit voice recorders." There is no current timeframe or defined endpoint to that investigation. However, with Ethiopia now saying that there are strong similarities between both events, is that sufficient for Boeing to proceed?

The press coverage and viral responses are not comparable to any other sequence of accidents for any other type. References to the Electra, Comet, DC-10 do not apply - these events went viral reaching an amazingly broad audience world-wide and the politically charged actions will have an impact (has airspace ever been closed to any other type?).


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Old 18th Mar 2019, 02:17
  #1859 (permalink)  
 
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Originally Posted by PaxBritannica View Post
I wonder too about the sales process. It does seem a little odd that carriers in the domestic market opted for an extra element there was no obvious reason to buy (if they didn't know there was a software feature for which it was a single point of failure), while third-world airlines did not. Was it just cost-saving, or did Boeing push a little harder / offer discounts where failures were less likely to be written off as down to poor maintenance / airmanship?
if all 737 Max have the second sensor, why should using it cost more, when the only purpose is _safety_ and avoiding a design fault ?
Come to think, why wasn’t MCAS documented properly in some foreign sales but documented in domestic ones?

i don’t get it.


Edmund


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Old 18th Mar 2019, 02:22
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Can I ask a question about MCAS?

It's my understanding applying nose down trim, will produce the effect of adding negative pitch attitude. So MCAS when activated is literally pushing the nose down. MCAS is sending nose down trim to bring the nose downward. Is this a completely correct statement from an engineering perspective? Is there any reason to think of MCAS another way? Does trim effect pitch attitude directly or is it providing column force so the pilot changes pitch? Would MCAS ever not be trying to bring the nose down? Is it inaccurate to say MCAS uses nose down trim commands to apply negative pitch attitude to the plane? In other words, does adding nose down trim add negative pitch attitude? Would MCAS ever be active adding trim in a scenario of high AoA and the plane has negative pitch attitude? Is MCAS literally part of the trim system?
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