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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 21st Mar 2019, 21:15
  #2281 (permalink)  
 
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Ignorant question: What is the practical use of a "disagree light"?? I suppose it means watch your workload increase as you continually assess your pitch attitude vis-ŗ-vis the airflow in an aircraft with a natural tendency to pitch up markedly when power is applied.

Wouldn't it be smarter to have THREE AoA indicators (same principle as three attitude indicators) and have the system stick with the two that are agreeing?
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Old 21st Mar 2019, 21:27
  #2282 (permalink)  
 
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Originally Posted by VFR Only Please View Post
Ignorant question: What is the practical use of a "disagree light"?? I suppose it means watch your workload increase as you continually assess your pitch attitude vis-ŗ-vis the airflow in an aircraft with a natural tendency to pitch up markedly when power is applied.

Wouldn't it be smarter to have THREE AoA indicators (same principle as three attitude indicators) and have the system stick with the two that are agreeing?
The use is to know that something is up with the*sensor*itself, and to be especially skeptical of the output from other flight computers that factor in its data (ADIRU).*
The problem with adding more indicators (3, 4, 5...?) is that sometimes 2 of them get erroneous data and 1 is left with correct and it gets voted out (AF447).
There is no perfect system.

To others saying why not add the AoA indicator, in the B737 you could actually just use the difference between the FPV and the pitch angle to figure out your AoA if you wanted to (assuming, again, the data input into these is valid).
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Old 21st Mar 2019, 21:47
  #2283 (permalink)  
 
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Originally Posted by atakacs View Post
This is nothing short of baffling. It would seem to be an extremely useful instrument to have in any aircraft.
Well, for most pilots in a commercial setting, AOA by itself means nothing.

For a military or airshow pilot who maneuvers to rather excessive AOAs regularly, or uses AOA as a primary reference for carrier landing, it makes a lot of sense to show some flavor of AOA. For example, nearly all Navy carrier aircraft are standardized to show something like15 units AOA in a properly configured approach, and something around 30 units AOA at stall. But there is no consistent units-to-degrees mapping, because the pilot doesn't care about absolutes; he just wants to know how close he is to some practical limit.

But for commercial pilots, AOA is relatively meaningless. In fact, it generally introduces needless concerns. What AOA is correct in a given setting: that's hugely dependent on a ton of factors. Which one (left or right) are you showing? How soon during takeoff roll should they come alive; with zero airspeed they can be at crazy values without any concern. They can be slightly different for various valid aerodynamic reasons (sideslip or roll rate). The only time you really care about AOA is when the two (or three or whatever) sensors dramatically disagree, or when they remain at excessive (very low or very high) values when they should not. That's all fairly easy to automatically check, if the FMC is programmed to do so.

WHY the FMC wasn't programmed to do so is a useful discussion. But showing the AOA to most pilots won't make things any better or safer. Principle #1 of human interface: only show what is important.

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Old 21st Mar 2019, 21:59
  #2284 (permalink)  
 
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Why didn't ET302 get higher than 1000ft AGL?

Iíve agonised for a couple of days whether to post this question because having read all the posts on both this and the Lion Air thread, Iím very aware of the understandable annoyance the professional pilots and qualified aircraft industry types on this forum feel when posters are too lazy to read or even search for answers to a question which has been asked perhaps several times before, or ask dumb questions. But, as explained below, Iím very puzzled, I donít think my question has been asked so Iíll risk being flamed.

It seems to be accepted that there are such similarities between the Indonesian and the Ethiopian crashes that Ė I suspect Ė a lot of people are assuming the cause of the accidents will also be similar. However, one difference between the two crashes which doesnít appear to have aroused all that much speculation, at least as far as I can determine, is the fact that the Ethiopian 737 only managed to get to perhaps 1000 feet (according to Flightradar24), whereas the Indonesian 737 appeared to achieve 5000 feet and the pilots consciously settled for that altitude.

This is where my non- aircraft background becomes apparent and the reason for my question; which is basically what caused ET 302 to be unable to get above 1000 feet? My simplistic flying control knowledge can think of only two things which might be possible causes. (Ignoring engine problems as the Flightradar 24 data indicated airspeed was increasing throughout the flight). One problem could be with the flaps which are extended to give extra lift on take-off, so presumably not having them extended fully, or to the extent required Ė particularly at an airport with the elevation of Addis Ė would make the aircraft really struggle. But this is really very basic and surely would have been recognised very quickly and remedied. The only reason I suggest it is that flaps not extended is supposedly a parameter for MCAS to function.

The other reason for inability to gain altitude would be for the stabiliser to be trimmed in a way for it to be forcing the nose down Ė supposedly the faulty AoA/MCAS scenario which is suggested caused the Indonesian 737 crash. An argument against this being the cause is that it has been said in posts on this forum, but without actual proof as far as I have seen, that there is a low altitude limit below which MCAS does not operate. If 1000 feet is classed as low altitude, I donít know what is.

This brings me to a point which was raised on this thread a long while back as to whether a coding error could have been made when the altitude limit (if it existswas coded into MCAS, and which would only be manifest at a high altitude airport like Addis (eg ASL used instead of AGL). Pretty basic error IF it was I know, but Iím reminded of the Mars Climate Orbiter fiasco in 1999

ďA NASA review board found that the problem was in the software controlling the orbiter's thrusters. The software calculated the force the thrusters needed to exert in pounds of force. A separate piece of software took in the data assuming it was in the metric unit: newtons."

Again, apologies for probably dumb questions and a lack of knowledge which probably has eyebrows raised and heads shaken in disbelief, but I would appreciate it if anyone could be bothered to answer, or preferably offer more soundly based reasons.

Regards





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Old 21st Mar 2019, 22:01
  #2285 (permalink)  
 
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Thanks Brandon,
Am I correct in thinking that the Navy displays ‘units’ instead of degrees in order to create an appropriate scale?
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Old 21st Mar 2019, 22:21
  #2286 (permalink)  
 
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Story presently being circulated by a body calling itself 'Patriots in America' - though whether that reflects upon the story itself, I am uncertain:

https://news.yahoo.com/pilot-hitched...053511780.html

iwalkedaway
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Old 21st Mar 2019, 22:43
  #2287 (permalink)  
 
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Salute!

As some have pointed out,
The big point is flaps should never be retracted with a continuous stick shaker going off. The last thing you want is to remove your high lift devices. Just maintain configuration & return to land. I am sure Boeing never envisioned a crew cleaning up & trying to complete the flight with a continuous stick shaker.
Yet the previous Lion flight did exactly that. Worse, they didn't log that or say what they did to maintain control - turning off the stab motor power and trimming with that wheel. They were "saved" by a thrid party who wasn't fighting 40 pounds of column and a vibrating yoke and going thru the stall and unreliable speed procedures. Manual trim on the yoke worked, so no big deal at first, other than the same dive that the next flight had when the flaps were retracted. Dunno why they retracted the flaps if that is the beginning of the NCC, but somehow the MCAS activated.

Gums...





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Old 21st Mar 2019, 22:45
  #2288 (permalink)  
 
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Originally Posted by iwalkedaway View Post
Story presently being circulated by a body calling itself 'Patriots in America' - though whether that reflects upon the story itself, I am uncertain:

https://news.yahoo.com/pilot-hitched...053511780.html

iwalkedaway
Not new, previously discussed.
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Old 21st Mar 2019, 22:56
  #2289 (permalink)  
 
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Originally Posted by 73qanda View Post
Am I correct in thinking that the Navy displays Ďunitsí instead of degrees in order to create an appropriate scale?
Yes. Because actual degrees of AOA really is meaningless, unless you're a "boffin" interested in things like measuring the field of view from the design eye position (more nose-up means less view), or for extreme cases the off-boresight capabilities of a missile attached to a launch rail, or things like that.

Admittedly off-topic for this MCAS problem, but still maybe of interest to some: Because a carrier-landing aircraft must land within a very narrow (~2 degree) range of angles relative to the flight deck to maximize its chances of capturing the arresting cable, and to make certain it's at an appropriate speed for not breaking itself or the cable, AOA is incredibly critical for carrier operations. However, the pilot still doesn't care what the actual values are. He needs an easy-to-remember, easy-to-read, and eminently predictable value as reference. So to provide nice round numbers to look at on displays, and to memorize for safety, all Naval aircraft AOAs are usually remapped to units with a rather arbitrary scale. And it varies with configuration; flap position, for example, significantly changes actual aerodynamic AOA at a given airspeed, but the airplane still has to land at the same nose-to-deck relative angle. So that remapping is variable. And it's typically indexed to 15 (plus or minus) for convenience and memorization. There may be simultaneously four or more different airplane types on a carrier (F-18E/F, F-18G, EA-6B, C-2, E-2, T-45, JSF), but all the pilots know "15 units" is the default landing AOA, more or less. The landing signals officer (LSO) handles all the types in a given day, and can't be bothered to remember 12.5 deg for this one, and 9.3 for that one, and.... Just make them all 15ish.

Similarly, the stall AOA varies with configuration and weight and other things... but keeping mental track of stall speed variations with weight and configuration is beyond the brainpower available. So it is also convenient to map stall speed to a fixed number - 30 units becomes convenient. And for a fighter pilot, stall AOA is incredibly important, because in a combat situation he may touch or even exceed that angle routinely (and safely).

At the low end, near-zero AOA in units generally corresponds to zero lift. Not really relevant much of the time, except during combat maximum pushovers, but still a useful metric.

Thus, the pilot always knows with a glance where he lies on the stall/landing/zero-lift continuum. It may have nothing to do with the actual AOA in degrees, but to his brain, that matters not at all.

To bring it back to MCAS and 737, adding true AOA - or even units AOA - to the flight deck of a commercial airliner is sort of irrelevant. They should NEVER approach stall; they better not be doing zero-lift pushovers; they don't have any extreme limits on AOA for touchdown or liftoff (other than perhaps avoiding tailstrike - but for that, pitch angle is the relevant data, not AOA.

Thus, from my point of view, adding AOA to commercial aircraft displays is "interesting but irrelevant." I challenge any pilot to tell me whether 12.3 degrees (for example) is meaningful by itself. It is only interesting if you also know that stall at your current weight and flap and gear setting is 19.7 deg, and the minimum load factor happens to be at 4.8 degrees, and if you also have the other AOA unit's value to compare to make sure they both agree within a reasonable limit. But making sense of all that data is just distraction from the real task of flying, and has no practical value. The only data you really need is the stall speed indication on the zipper, which does all that thinking for you.
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Old 21st Mar 2019, 22:56
  #2290 (permalink)  
 
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More confirmation had came out. The dead head pilot indeed had prevented the plane from a possible crash on its penultimate flight.


Indonesian officials confirm presence of guest pilot who reportedly saved Lion Air plane day before its fatal crash

...Indonesian investigators on Thursday confirmed the presence in the cockpit of an off-duty pilot reported to have saved a troubled Lion Air flight the day before the same plane crashed on Oct. 29...
...“The third pilot, who has not been identified, was qualified to fly Max 8s and was deadheading aboard the Oct. 28 flight from Bali’s Denpasar airport to Jakarta,” said Soerjanto Tjahjono, the head of Indonesia’s National Transportation Safety Committee, referring to the practice of company employees traveling free of charge. “The aircraft encountered the same problems that appear to have caused it to crash a day later.”...
==========


- https://www.washingtonpost.com/world...=.c1dd3c7c811c
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Old 21st Mar 2019, 23:05
  #2291 (permalink)  
 
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Ok, so we're supposed to believe that the speeded-up certification process of the Max just let ONE bug through.
Or rather, the industry agrees that the best way to search for more bugs is to pull the grounding order, put pilots and SLF in a bunch of planes, and fix whatever happens next.

No wonder the rich refuse to fly commercial.

Edmund
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Old 21st Mar 2019, 23:15
  #2292 (permalink)  
 
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I can't see that a quick fix for MCAS is going to reassure the travelling public, ie me. If MCAS was a bodge, how many other bodges were found acceptable? If this was the only place in the design where engineers were asked to take a 'small' risk, I suspect whispers would have gotten around long before the plane flew. Therefore, it's likely that it was just one of many other design 'solutions' where the idea of tolerable risk was normalised.

No software patch will fix systemic management hubris.
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Old 21st Mar 2019, 23:16
  #2293 (permalink)  
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Originally Posted by gums View Post
Salute!
-----------------------------------------
I am trying to follow the ROE for our forum, but it's getting hard. I do not mean to diminish the length and breadth of experience that many pilots here have contributed to the discussion. But somethimes I get a little testy.

My fear is that some lurking here will think that we lost two planes and 300 passengers because incompetent crews did not simply turn off two switches within seconds of raising flaps at normal altitude and speed with the stall warning system telling them they were stalling and their airspeed was FUBAR.

The primary contributing factor to loss of control in the Lion crash and likely the Ethiopian one ,is gonna be the MCAS and its implementatio without fairly documenting it for the crews and not considering its activation at a corner of the envelope it was not intended for.

Gums...
Plus 1, gums

Last edited by PJ2; 22nd Mar 2019 at 01:45.
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Old 21st Mar 2019, 23:46
  #2294 (permalink)  
 
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Current comment from Mr G Thomas quoting Greg Feith :

“However, the disturbing reality is that it took a pilot who was not in command of the flight, and just an observer, to tell the captain and first officer (who were supposedly trained, qualified, and experienced in the operation of the Boeing 737 MAX) what the issue was that resulted in the nose of the airplane pitching down (uncommanded pitch trim input also known as a “runaway trim”),” he said.
“The fact that the pilots who were in command of the flight and had access to the flight controls did not recognise nor properly respond to the “runaway trim” event is a testament of a more systemic problem within Lion Air.”
There are four failures that will cause a runaway trim on a standard 737 and five on a MAX version with the new background software to help the pilots fly the plane.It was not this software that caused the crashes, rather faulty sensors feeding it incorrect data. “
The flight crews’ failure to understand the issue and implement the proper corrective actions (which are memory items) is a symptom of a more serious problem and a likely explanation for the loss of the airplane if the accident crew reacted in the same manner – confused, panicked and hoping to find the answer in book rather than reverting to what they would have learned in training,” Mr Feith said.
On the Ethiopian crash, Mr Feith said that it was “also of interest that it took the Ethiopian investigative team five days to find a place to have the FDR and CVR data downloaded and converted to a medium that could be used by investigators to determine the initiating event that led the pilots to lose control of the airplane.”
If the quote is accurate then Mssrs Feith and Thomas should get on very well together.
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Old 21st Mar 2019, 23:56
  #2295 (permalink)  
 
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Originally Posted by TriStar_drvr View Post
No. At rotation flaps would be extended. MCAS does not engage with the flaps extended.
​​​​​​.. .and so.. our game crew retract the flaps, cos they are approaching Vfe in the aircraft config but the light is on? What happens next?
How the heck they ever got this through part 14cfr chapter 25 certification reliant on only 1 sensor?

Seems to me, in the rush to fix one certification issue, someone forgot the rest.

Ttfn
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Old 22nd Mar 2019, 00:11
  #2296 (permalink)  
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I have flown with AoA indicators on various corporate jets.
I found them extremely useful as a conformation for approach and departure speeds.
Why they are not standard on larger jets is puzzling.

If MCAS was a bodge, how many other bodges were found acceptable
Stick pushers, stick shakers, Stall Avoidance System on SA227 aircraft, etc..

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Old 22nd Mar 2019, 00:15
  #2297 (permalink)  
 
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Originally Posted by PaxBritannica View Post
I can't see that a quick fix for MCAS is going to reassure the travelling public, ie me. If MCAS was a bodge, how many other bodges were found acceptable? If this was the only place in the design where engineers were asked to take a 'small' risk, I suspect whispers would have gotten around long before the plane flew. Therefore, it's likely that it was just one of many other design 'solutions' where the idea of tolerable risk was normalised.

No software patch will fix systemic management hubris.
It is amazing the amount of Boeing bashing on this forum. Boeing has made tens of thousands of safe & efficient airliners for more than half a century & that's why there are more Boeings than anything else. Every airplane design is a compromise that needs to be tweaked in one way or another to meet certification requirements. This process takes many months & involves much actual test flying. The much maligned MCAS was a tweak to meet an obscure certification requirement that was probably never going to be encountered in the life of the airplane. A lot of effort over decades has gone into making the aircraft as safe & foolproof in operation as possible. But, how do you design for an airline that flies an aircraft for three days with unreliable airspeed, maintenance that then compounds the problem with a bad AOA installation, & flight crews that still try to complete the flight with a continuous stick shaker? We don't know yet about Ethiopian, but if it was the same malfunction after all the warnings & publicity worldwide from Lion Air, then that is the height of incompetence.
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Old 22nd Mar 2019, 00:18
  #2298 (permalink)  
 
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Originally Posted by gums View Post
Salute!
---snip---
I am trying to follow the ROE for our forum, but it's getting hard. I do not mean to diminish the length and breadth of experience that many pilots here have contributed to the discussion. But somethimes I get a little testy.

My fear is that some lurking here will think that we lost two planes and 300 passengers because incompetent crews did not simply turn off two switches within seconds of raising flaps at normal altitude and speed with the stall warning system telling them they were stalling and their airspeed was FUBAR.

The primary contributing factor to loss of control in the Lion crash and likely the Ethiopian one ,is gonna be the MCAS and its implementatio without fairly documenting it for the crews and not considering its activation at a corner of the envelope it was not intended for.

Gums...
Gums,

Mostly everyone here who is *not* a pilot realizes that the rushed certification of the Max is the real issue.

AFAIK nobody except Boeing lawyers and maybe the families is going to lay the blame on those pilots. Anyone, pilot or not, who reads the details of MCAS spooling up time and again in those cockpits thinks "there but for the grace of God go I".

But there is one interesting question though which is why those who survived such MCAS incidents prior to the Lion Air crash did not document them and raise a stink. Was it because they thought they had made an operational mistake?

Edmund
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Old 22nd Mar 2019, 00:41
  #2299 (permalink)  
 
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QF72 - A330

Running through TiVo tonight I came across the Air Disaster documentary on QF72. It's an A330 but at a high-level there is a lot in common with these recent tragedies.

https://www.smithsonianchannel.com/s...ll/802/3467449
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Old 22nd Mar 2019, 00:42
  #2300 (permalink)  
 
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I canít see any foreign regulatory authority allowing the Max into its airspace without an extensive modification of the stall avoidance system and an in-depth training program for Pilots and engineers. A separate type rating covering the Max, rather than relying on a current B737 rating is a real possibility. A new type certificate might also be on the cards as well.

After two disasters, no authority is going to sign off on a solution unless itís iron clad and well in excess of whatís required, a software update isnít going to be enough. No pilot will be flying a Max until heís demonstrated proficiency in dealing with any possible MCAS failures a simulator.

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