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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 12th Apr 2019, 09:05
  #3881 (permalink)  
 
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Originally Posted by artee
An article on Bloomberg:
‘Not Suitable’ for Certain Airports

...‘Challenging Airports’

Boeing stated in a brief filed in the trade case that the “737 Max 7 has greater performance capabilities at challenging airports. In particular, the 737 Max 7 can serve certain ‘high/hot’ airports and has a greater range operating out of constrained airfields.” The brief then cites a number of such airports -- the names of which are redacted -- that the Max 7 can fly into that “the 8, 9 and 10 cannot."

“Larger 737 variants cannot be used at what are referred to has ‘high/hot’ airports,” the brief stated. Certain U.S. airports are unsuitable for the Max 8 “due to a combination of short runway lengths, elevation, temperature, humidity and other environmental conditions."...
That's just a red herring. It talks about "short runways". Nobody in their right mind would think a 3700 m runway was short. It is a sales pitch for the MAX 7, and it has nothing at all to do with this accident or the one in Jakarta.

Documents in the trade case referred to at least 16 U.S. airports considered “high and hot” and therefore unsuitable for the Max 8, though the names of those facilities weren’t made public. Asked during a trade commission hearing to specify which airports, an expert witness for Boeing replied that “sometimes Denver would qualify as that.” The expert, Jerry Nickelsburg, an adjunct economics professor at UCLA, added that “Mexico City certainly qualifies as that.”
Yes, Denver could sometimes be called "hot and high", but would never fall in the category of "short runway". The same goes for Mexico City.

The manufacturer provides rules (usually computer software and long tables) telling the crew the required runway lengths for takeoff for a given combination of weight, elevation and temperature. These values contain ample margins for uncertainties in actual weight, temperature and wind variations and various failures including an engine failure. If the runway is long enough it is long enough.

Yes, there will be some airports, where the MAX 7 can operate with higher payloads than the 8/9/10. So what?

They are probably rather talking about small regional airports such as Telluride.

The Ethiopian airport’s altitude hasn’t been cited as a factor in the downing of Flight 302 and likely didn’t cause the crash. But it could have exacerbated the situation because an airplane’s performance degrades at higher altitudes, said a 737 pilot who flies into high-elevation airports such as Denver ,
This shows how disingenious this article is. "It is totally irrelevant but we'll blurb on about it anyway. And look, we even found a pilot who said something totally unrelated!". There certainly was no problem with aircraft performance in either accident, except perhaps there was too much of it.

Denver will not be on this list. Neither will Mexico City, Jakarta or Addis Ababa. They are all big International Airports with very long runways. The "expert" is an "adjunct economics professor". I rest my case.


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Old 12th Apr 2019, 09:14
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You know, back when a young CGB was taught to fly, we didn't just consider runway length when examining departure performance................

Just sayin'
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Old 12th Apr 2019, 09:26
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Originally Posted by bsieker
The "expert" is an "adjunct economics professor". I rest my case.
To be fair, his comments weren't made in the context of either of the Max accidents, but in an anti-competitive hearing where he was simply comparing the hot-and-high performance of the Max 8 compared to the Max 7, in other words stating the obvious. So let's not put words in his mouth.

Incidentally his CV includes being a VP at FlightSafety International, and 8 years at McD before that, so I suspect he does actually know one end of a WAT curve from the other.
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Old 12th Apr 2019, 10:02
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The Case for Pilot Error

Curtain Twitcher, et al, #3938
The value of ‘The Case for Pilot Error’ should be rated by the purpose of the report (small print at the end):-
The purpose of the report is to help our institutional clients answer the following questions: 1) what are issues, 2) can the problems be fixed, 3) how long will it take, and 4) at what cost. The last step is to value BA (Boeing Co) and the airlines impacted by the grounding of the MAX aircraft fleet.”

Also by who the authors are now, opposed to what they list as piloting experience - ‘what we say reflects thoughts’.
“…founded AirlineForecasts, LLC … has managed airline and transportation-related investment research … Clients included …, Southwest, and WestJet pilot groups.

And their conclusion:-
Examining both accidents separately provides valuable insights—it’s easy to understand how these unrelated airlines and crew may have responded in similar ways—but the overall conclusion in our previous article, “Boeing’s Grounding: Catastrophic Crashes, and Questions About Boeing’s Liability And 737 MAX Aircraft Viability,” still stands—the major contributing factor to these accidents was pilot error.

Which begs the question what is ‘pilot error’; or of greater concern is if the views of these US based, airline pilots (authors) reflects the standard or effectiveness of human factors training in the wider industry.

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Old 12th Apr 2019, 10:34
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I'm starting to draw parallels with the "Guns don't kill people, people do" argument. There certainly appears to be a lack of subscription to modern safety management principles (layers, bow-ties etc).

The whole 'defence' seems to be based around an argument that whilst BA created a characteristic of HAL that would make him suicidal purely because of a single corrupt data path, everything would be OK as long as you subsequently disabled HAL within a finite period. Hmmmm, I'm not detecting an overly mature hazard analysis process there.

Originally Posted by HAL9000
I know I've made some very poor decisions recently, but I can give you my complete assurance that my work will be back to normal. I've still got the greatest enthusiasm and confidence in the mission. And I want to help you."
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Old 12th Apr 2019, 10:47
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This seems to be "tombstone" learning..

LionAir didn't know about MCAS, so plain stuffed it up.

Ethiopian learnt about MCAS due Lionair, but didn't know about next to impossible trim forces and yoyo, so stuffed it up.

So airline #3 will come along; know about MCAS, know about high trim loads, but will then encounter ???

It's a rum way to do airline safety... I know in IT we used to do field tests to let customers shake out the bugs but I didn't know aircraft manufacturers now practised it..

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Old 12th Apr 2019, 11:14
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Originally Posted by DaveReidUK
To be fair, his comments weren't made in the context of either of the Max accidents, but in an anti-competitive hearing where he was simply comparing the hot-and-high performance of the Max 8 compared to the Max 7, in other words stating the obvious. So let's not put words in his mouth.

Incidentally his CV includes being a VP at FlightSafety International, and 8 years at McD before that, so I suspect he does actually know one end of a WAT curve from the other.
Yes, It was perhaps a bit unfair towards Professor Nickelsburg, and I apologise. What annoyed me is that Bloomberg even put it in the context of the accidents, even going so far as to claim that "it could have exacerbated the situation because an airplane’s performance degrades at higher altitudes", when there is no hint that this may have played any role, and lack of performance (as in: insufficient engine power) was certainly not a problem.

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Old 12th Apr 2019, 11:16
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Originally Posted by Cows getting bigger
You know, back when a young CGB was taught to fly, we didn't just consider runway length when examining departure performance................

Just sayin'
Well, sure, there's also terrain, overrun areas, possible emergency landing locations and whatnot, but I didn't want to make it longer than it already was. I could have added "and other parameters" but didn't bother.

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Old 12th Apr 2019, 11:20
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Originally Posted by Cows getting bigger
I'm starting to draw parallels with the "Guns don't kill people, people do" argument. There certainly appears to be a lack of subscription to modern safety management principles (layers, bow-ties etc).

The whole 'defence' seems to be based around an argument that whilst BA created a characteristic of HAL that would make him suicidal purely because of a single corrupt data path, everything would be OK as long as you subsequently disabled HAL within a finite period. Hmmmm, I'm not detecting an overly mature hazard analysis process there.
I agree. There seems to be a strong correlation between:
- chauvinistic attitudes to 3rd world pilots
- a protective attitude towards a 1st-world manufacturer
- the mentality of blame the victim/dead guy.
Even if its 99% the manufacturers fault, and 1% the pilots fault, its still "pilot error", and "they caused the crash".

Edit: Another irony is that a few pages back in this thread, we have a link to the great Ralph Nader, pointing out the greed and iniquity of the corporate villain Boeing! So far, I don't see Ralph Nader suing the airline. IMO both aspects highlight the gulf in understanding the complex causal chain in any accident.

Last edited by GordonR_Cape; 12th Apr 2019 at 11:45. Reason: Add thoughts.
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Old 12th Apr 2019, 12:31
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Originally Posted by rog747
Not sure I buy the bird taking out the AoA vane shortly after lift off...did they find a dead bird or the vane on or near the runway at ADD?- in this day and age of forensics can these items be found?
I agree that loss of a vane is questionable for 2 reasons:-
1) The idea that there are 2 (or 3) different AoA sensor faults were experienced on the 2 Lion Air flights and ET302 flight seems to me to be very unlikely from a probabilistic point of view, especially so as the AoA sensor is apparently generally very reliable.
2) The lack of noise on the high value of AoA of a flat-line value of 74.5deg. Noise is seen on both R & L AoA right up to take off, and stays at about the same amplitude on R AoA throughout the flight, suggesting it is not caused just by air speed buffeting of the vane. Instead the noise seems to start just as the engines reached 94%, so I suspect the noise is more air-frame vibration related. I find it hard to believe that a counter weight (without a vane) would stay exactly on 74.5 for minutes and not now be affected by vibration plus all of the other changes to flight dynamics. A fixed offset, sometimes tracking the R AoA value, sometimes not, looks to me like a software generated value.

I think the “lost vane” idea came from an observation on ET 302’s FDR Data chart that Vertical Acceleration lines up with a jump in AoA. It is possible that “cause and effect” may have been misinterpreted here because Vertical Acceleration is a consequence of, and directly related to Pitch Rate. This would fit in with the fact that AoA L was disrupted on the 2 Lion Air flights (as well as on ET 302) just around take off when there would have been a large value for pitch rate.

This could well be relevant as one of the AoA correction factors is Pitch Rate, according to Fig 9 in Boeing’s aero_12 magazine (Figure 9. AOA Measurement Errors)
As I mentioned in an earlier post (#2744), I think an error in the correction calculating software may be the source of the AoA corruption problem. Earlier discussions have suggested that the AoA sensor itself must be the single source of a bad analogue value as both the SMYD (for Stick Shaker on/off determination) and the ADIRU receive bad data. However, either the SMYD uses the corrected AoA from the FCC (via ARINC 429) or it computes the same correction (possibly using an exact copy of the software) as the ADIRU. If the SMYD does its own computation of AOA, then both SMYD and the ADIRU took take a good analogue signal, apply an incorrect correction to produce garbage for AoA. Obviously there has to be a common failure that triggers both sets of computations to produce garbage for AoA. As the fault is always on the Left, the common failure could well be the loss of the signal that tells the L SMYD and the L ADIRU that they are Left, resulting in both of them using the correction algorithm for a Right AoA sensor on data from the Left AoA sensor and computing garbage values.
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Old 12th Apr 2019, 13:16
  #3891 (permalink)  
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VicMel Thought provoking.

I find it hard to believe that a counter weight (without a vane) would stay exactly on 74.5 for minutes and not now be affected by vibration plus all of the other changes to flight dynamics. A fixed offset, sometimes tracking the R AoA value, sometimes not, looks to me like a software generated value.
I'm swinging between both extremes of scenario. However, that balance weight flopping near the end of ET's flight is hard to reconcile, even with Vic's logic.

That slight change of AoA at 05:41:22 - ish, is also troubling me. Why there? Why so consistent before and then after the change? i.e., if it can change at all, why would it remain steady either side of the change?
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Old 12th Apr 2019, 13:19
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Originally Posted by VicMel
I agree that loss of a vane is questionable for 2 reasons:-
1) The idea that there are 2 (or 3) different AoA sensor faults were experienced on the 2 Lion Air flights and ET302 flight seems to me to be very unlikely from a probabilistic point of view, especially so as the AoA sensor is apparently generally very reliable.

I think the “lost vane” idea came from an observation on ET 302’s FDR Data chart that Vertical Acceleration lines up with a jump in AoA. It is possible that “cause and effect” may have been misinterpreted here because Vertical Acceleration is a consequence of, and directly related to Pitch Rate. This would fit in with the fact that AoA L was disrupted on the 2 Lion Air flights (as well as on ET 302) just around take off when there would have been a large value for pitch rate.
Well, how does that align with ALL the information?
At 05:38:44, shortly after liftoff, the left and right recorded AOA values deviated. Left AOA decreased to 11.1° then increased to 35.7° while value of right AOA indicated 14.94°. Then after, the left AOA value reached 74.5° in ¾ seconds while the right AOA reached a maximum value of 15.3°. At this time, the left stick shaker activated and remained active until near the end of the recording. Also, the airspeed, altitude and flight director pitch bar values from the left side noted deviating from the corresponding right side values. The left side values were lower than the right side values until near the end of the recording.
At 05:38:43 and about 50 ft radio altitude, the flight director roll mode changed to LNAV.
At 05:38:46 and about 200 ft radio altitude, the Master Caution parameter changed state. The First Officer called out Master Caution Anti-Ice on CVR. Four seconds later, the recorded Left AOA Heat parameter changed state.

There is very little in terms of cause and effect that would satisfy the heater parameter change other than losing the vane itself. (Unless you want to believe this is entirely spurious).

- GY

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Old 12th Apr 2019, 13:27
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Originally Posted by CurtainTwitcher
One has to wonder if the Boeing PR machine is starting to kick into gear behind the scenes, and orchestrate a smear campaign through friendlies to point the finger at the pilots (as per the Seeking Alpha The Boeing 737 MAX 8 Crashes: The Case For Pilot Error) and operators instead of Boeing. Boeing Has Called 737 Max 8 ‘Not Suitable’ for Certain Airports. The "Not suitable for certain airports" implies Jakarta as being in this category (too hot). All the hallmarks, unattributed expert opinions such as "Mark". Reporters just happened to find these U.S. International Trade Commission documents lying around?
In reference to the "Not Suitable" article statement... What a load of nonsense.

How does an AOA sensor become discombobulated by temp or pressure altitude???? Seriously, has relaxing the pot laws in WA resulted in loopiness in Chicago head office? If Boeing wants to defend their position, they need to get serious and deal with the facts at hand and not puff smoke or play with mirrors.

WAT limits per 25 Subpart B control suitability of the aircraft for a particular operation for the certification of the aircraft, not the name or number written on the side of the plane by the OEM.
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Old 12th Apr 2019, 14:00
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Totally agree that this is an effort to build the public opinion case for pilot error.
To me the worst part of the 'case for pilot error' is no mention of even the possibility that the crew was unable to manually trim and the suggestion they were very slowly winding the wrong way.
The slight .2 unit wrong way trim during the manual trim phase of the flight could be due either to struggles with the wheel or (less likely in imho) back drive from the extreme load.

He then slams them for the aparent last ditch re-enabling of electric trim.

The lack of speed management certainly was a factor but had they been able to manually trim they would likely dealt with it next.
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Old 12th Apr 2019, 14:17
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I think there is another HF issue (already commented on some time back) in that it is utterly counter-intuitive to reduce thrust when the nose is pitching down. It is like leaning to right when you want to turn your bicycle to the left.
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Old 12th Apr 2019, 14:18
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Originally Posted by MurphyWasRight
Totally agree that this is an effort to build the public opinion case for pilot error.
I find it quite remarkable that it takes such a long windup to finally conclude that the crew did not do everything perfectly. Duh. No human ever does.

And then it just stops. What is the point of finger-pointing? How can that help anyone in any way? (Except perhaps Boeing's reputation, but even that is doubtful.)

A finding of "Human Error", can never be the end of an analysis, rather it must be the start of asking questions such as:
  • What was the exact situation the operators were in?
  • What was the information they could get?
  • Was some information maybe ambiguous? Even contradictory? Hard to find?
  • How much time did they have to find it?
  • How much time did they have to analyse it?
  • Were they trained to evaluate the information properly?
  • Were there perhaps multiple anomalies requiring different, possibly even contradictory procedures?
  • Was there perhaps cognitive overload?
  • Did they (could they?) have an understanding of why the system did what it did?
  • What additional information do we have now, that the operators at the time did not have? (The easy one: we know that what they did eventually led to an unrecoverable situation. They didn't. Or else they wouldn't have done it.)
  • Which again leads to: why did they do what they did?
  • How can we prevent:
    • ... crews from doing the same things again, or better still:
    • ... anyone from getting into the situation in the first place?
I repeat here the image I posted way back that makes these ideas very clear:


From The Field Guide to Understanding 'Human Error' by Sidney Dekker

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Old 12th Apr 2019, 15:11
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I used to always think that we, as a community, tend to focus more on the who, instead of the more pertinent, what, which should be followed by the even more pertinent, why. I now understand that the whole industry is afflicted by the malaise.
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Old 12th Apr 2019, 15:35
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in that it is utterly counter-intuitive to reduce thrust when the nose is pitching down.
Have you done jet upset or UA recovery in the sim? Low nose is always reduce power.
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Old 12th Apr 2019, 16:29
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Originally Posted by Loose rivets
VicMel Thought provoking.



I'm swinging between both extremes of scenario. However, that balance weight flopping near the end of ET's flight is hard to reconcile, even with Vic's logic.

That slight change of AoA at 05:41:22 - ish, is also troubling me. Why there? Why so consistent before and then after the change? i.e., if it can change at all, why would it remain steady either side of the change?
Given the oil damping system and inherent friction it would be reasonable to expect the weight to stay put and not respond to vibration or minor changes in g.
.
The forces on an operating AoA vane/system would be high compared to the weight which is just there to balance the vane.
It is not like the weight on a balance beam scale that is part of the measurement.

I think the change at 05:41:22 - ish and one slightly after that can be explained by 2 brief excursions to ~.5g (bit hard to tell exact from graph) at the same time.
Each of those might have 'bumped' the weight enough to shift it slightly.

Last edited by MurphyWasRight; 12th Apr 2019 at 16:44. Reason: Added friction to oil dampening.
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Old 12th Apr 2019, 16:30
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Originally Posted by Icarus2001
Have you done jet upset or UA recovery in the sim? Low nose is always reduce power.
Wow, who taught you that?
Un load and wings level are first on the list, but when it comes to power, that is as needed.
That means you might need to add power in a low speed, low nose situation. The faster you are on speed, the faster you can pull out.
(Rule of thumb, speed in the 100's - add power, speed in the 200's - power in the mid range, speed in the 300's - cut the power)
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