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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 26th Apr 2019, 14:50
  #4361 (permalink)  
 
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Originally Posted by 737mgm View Post
Another issue is, if these accidents were preventable by carrying out the required Boeing procedures or by applying basic flying skills respectively, despite MCAS activating.
When I was trained on the 737 (classic and NG), the stab trim runaway was a runaway - where the trim wheel ran continuously. We would identify it as a runaway, because it was continuously running, and flick the switches.

1. MCAS activation is not continuous, it's bursts.
2. The 737 trim system likes to provide bursts of random trim at certain times (STS) so bursts are considered normal.

This is why the Boeing excuse "they should have done the runaway stab QRH to fix the MCAS problem" is a load of utter nonsense. 737 Driver - pinning this on lack of airmanship will costs lives in the future.
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Old 26th Apr 2019, 14:56
  #4362 (permalink)  
 
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HundredPercentPlease,

I don't know the 737 but I used to fly 707s. The stab trim runaway drill was predicated on continuous movement as you say. I imagine the bursts of STS activity made these movements appear normal and thus mask the MCAS bursts too. All very confusing.
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Old 26th Apr 2019, 14:58
  #4363 (permalink)  
 
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Originally Posted by sky9 View Post
Can I just highlight that the F/O had 200hrs experience. I didn't get a commercial pilots licence until I had flown 230 hours and didn't fly jets until I had 1800hrs. The company that I flew 737's for in the UK in the early 1970's required 2000 hours before offering a job in the right hand seat.

This incident was to all intents and purposes a single pilot operation.
Absolutely spot on. At 200 (300 according to ET) hours, you are just along for the ride. The CA himself may have never flown anything outside of ET, certainly not old and broken airplanes from the past. It really bothers me that to this day, I sometimes look over at the FO for ideas or help in doing mental math, and he has nothing to contribute. These aircraft are certified for a minimum of two experienced pilots, not one instructor and one student. Ridiculous.

12,000 hours as captain of 727/57/67, I still rely on my highly experienced F/O's to feed me as much advice as they can.
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Old 26th Apr 2019, 14:59
  #4364 (permalink)  
 
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Originally Posted by HundredPercentPlease View Post
When I was trained on the 737 (classic and NG), the stab trim runaway was a runaway - where the trim wheel ran continuously. We would identify it as a runaway, because it was continuously running, and flick the switches.

1. MCAS activation is not continuous, it's bursts.
2. The 737 trim system likes to provide bursts of random trim at certain times (STS) so bursts are considered normal.

This is why the Boeing excuse "they should have done the runaway stab QRH to fix the MCAS problem" is a load of utter nonsense. 737 Driver - pinning this on lack of airmanship will costs lives in the future.
I think we disagree where a burst ends and continuously starts. Only been in the jumpseat of the 737, but I would be wildly surprised if STS would ever trim more than a second or two. Having the trim wheel run for ten seconds is way more than a burst. Having said that I can totally see the pilots not realizing what is going on amidst the whole set of stall warning/stick shaker/UAS indications. MCAS should never have been certified using only one AOA at a time, and I feel the same goes for the stall warning/stick shaker, there should at least be an easy way to cancel the alert if the warning is spurious.
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Old 26th Apr 2019, 15:04
  #4365 (permalink)  
 
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Originally Posted by sky9 View Post
Can I just highlight that the F/O had 200hrs experience. I didn't get a commercial pilots licence until I had flown 230 hours and didn't fly jets until I had 1800hrs. The company that I flew 737's for in the UK in the early 1970's required 2000 hours before offering a job in the right hand seat.

This incident was to all intents and purposes a single pilot operation.
This airline isn't alone in setting up that situation.
It does not help that the captain was only recently transitioned to the new aircraft, and the already-mentioned-a-few-hundred-times issues with "just what was in the differences training?" was hardly a robust aircraft systems course. That their best efforts were not good enough points, in my view, a finger at the system writ large: training, currency, company policies on training (and others) and of course the aircraft system itself. What is to me the most worrying is that with the comparatively recent Lion Air crash, this crew was, it seems, neither prepared nor trained on how to deal with that problem.
That right there, it seems to me, is where the entire system let these two pilots down. The "system" doesn't learn, and / or does a poor job of passing on "lessons learned."
Deni, a few pages back, points to the AoA signal getting to the flight computer as being a detail worthy of very thorough resolution. With the Lion Air ending up in the sea, some evidence of how that signal went sour may have been lost. In this crash, granted, there was a fire, perhaps some evidence of that signal's path, and it's possible sources of corruption, may be more clear.
I sincerely hope that Beoing's team is, along with their various test flights, putting a high magnification glass on the entire path of the AoA signal from vane to computer, and focues on how and where those signals can get dirty/contaminated. I experienced a variety of strange things happening in aircraft over the years due to electrical signals going astray or strange. Were stray trons a root cause?
We'll see.
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Old 26th Apr 2019, 15:13
  #4366 (permalink)  
 
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Originally Posted by HundredPercentPlease View Post
When I was trained on the 737 (classic and NG), the stab trim runaway was a runaway - where the trim wheel ran continuously. We would identify it as a runaway, because it was continuously running, and flick the switches.

1. MCAS activation is not continuous, it's bursts.
2. The 737 trim system likes to provide bursts of random trim at certain times (STS) so bursts are considered normal.
Honest question: How long does a trim wheel have to spin before you deem it "continuous" and thus subject to intervention by the pilot?

In the case of Ethiopian, the MCAS input was not like the normal Speed Trim you see during takeoff. If you take a look at the DFDR traces of the automatic trim before the flaps were retracted, you can see what these inputs look like. Short and seemingly random inputs.

When MCAS activated, it ran the trim nose down for 9 continuous seconds. Please count that out to yourself. MCAS moved the stab about 2.5 degrees. That would be about 37 spins of the flight deck trim wheel. Please imagine that white stripe on the trim wheel making 37 trips passed the Captain's knee. All this time, the Captain was holding the yoke and must have felt the changing trim pressures. This happened TWICE (one other MCAS input was interrupted by the pilot trimming nose up). Ultimately, it wasn't even the 8122-hour Captain who suggested that the trim cutout switches be used - it was the 361-hour First Officer.

So honestly, just how long does the stab have to continuously run before a fully qualified 737 type-rated Captain determines that he has runaway stab trim?
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Old 26th Apr 2019, 15:42
  #4367 (permalink)  
 
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Reviewing the charts, can someone explain to me why the N1 percentage seems to be 95-100%? This aircraft seems to be going at a very high IAS. No wonder manual trim was so difficult. Rule number 1, fly the aircraft.
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Old 26th Apr 2019, 15:45
  #4368 (permalink)  
 
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Salute!

Thanks a lot, Wonk. Best post in a very long time.

Maybe some of the “Sky Gods” here would think about some things.

And I support your criticism of Big B and FAA and so forth for letting the plane fly we lowly proles without satisfying basic aerodynamic FAR requirements. I would even go so far as to claim the Airbus FBW models could be flown in “direct law” and behave as required. After all, the AF447 debacle showed how stable the plane was despite the best efforts of the crew to keep it stalled.

Gums ......
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Old 26th Apr 2019, 16:31
  #4369 (permalink)  
 
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Gums,

As I understand it, when designing the A320 Airbus toyed with the idea of reduced stability, citing FBW as the "excuse". The whole world raised a regulatory eyebrow and Airbus designed a fully stable aircraft.

Ironically, Boeing designed a less than stable aircraft with a bit of bolt on, undocumented FBW, and the world continued to rotate, until two crashed.
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Old 26th Apr 2019, 16:41
  #4370 (permalink)  
 
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Originally Posted by 737 Driver View Post
). Ultimately, it wasn't even the 8122-hour Captain who suggested that the trim cutout switches be used - it was the 361-hour First Officer.
The reason people are bashing your skygod/airmanship analysis is hidden in your statement above.

Why do you think the captain didn't get it, but the FO did?

Really, why?

As so many are saying, this is HF. Think: volume of input and processing.

A final thought: do you think that if the ET crew had trained this scenario in the sim, then when it happened for real then they would have been fine? The comfort of the sim helps recognition, which reduces processing, which allows improved performance through lack of overload. The max is a dog, but Boeing would have got away with it (again) if pilots had been sim trained.

These pilots were overloaded, they weren't adequately prepared and the aircraft is flawed.
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Old 26th Apr 2019, 16:47
  #4371 (permalink)  
 
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Originally Posted by HundredPercentPlease View Post
.
These pilots were overloaded, they weren't adequately prepared and the aircraft is flawed.
Agree 100%. So what should be done to insure the next crew is not overloaded and unprepared the next time they are handed a flawed, but still flyable, aircraft?

Because there will be a next time.



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Old 26th Apr 2019, 16:57
  #4372 (permalink)  
 
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Simple.

Remove the flaw. Either remove the aerodynamic stability problem or make the FBW fix a proper one (like an Airbus, triple inputs, 14 computers, multiple layers of automatic or selectable degraded flight modes).

Train the pilots. If a single failure (here AoA) causes a monster, then prepare the pilots by training.

As someone who has moved back and forth, twice, between the 737 and A320, I can't begin to describe how lowly I view the Renton tractor. Boeing made a flawed aircraft and failed to mandate sufficient training. The pilots are as much victims as the passengers. No doubt at all.
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Old 26th Apr 2019, 17:07
  #4373 (permalink)  
 
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Originally Posted by 737 Driver View Post
Wonkazoo,
Ultimately, these planes were flyable using some pretty basic airmanship skills, but that did not happen.
No.
Look I agree with most of what you're saying. Good airmanship, hand flying practice, all the other great points.

But this is different to any other aircraft system failure that I can think of.

Eg loss of pitot. Loss of static. Engine fire. "QF32" uncontained failure causing multiple control system failures. Flap/slat wrong config at takeoff. Dual engine out after bird strike... Etc.

These are all single events that put the aircraft in a new and interesting state. Now use good airmanship to recover. Fine.

Why is MCAS different?
1) It's intermittent. Not just a single event. Pops up unexpectedly for a few seconds then disappears. These are always the hardest faults to diagnose.
2) It's insidious - hidden by noise and by human expectation (hiding in plain sight - bursts of trim are normal).
3) It's fast - it can put you in serious trouble in a few seconds flat
4) Like a bacterial complication to a viral infection, it creeps in and hits you when you're dealing with another problem (airspeed unreliable/stick shaker)
I'm not saying that the ET302 pilots had no room for improvement. Like you I think their repeated autopilot engagement is a red flag. But dealing with MCAS failure is in test pilot league, not 'basic airmanship skills'.
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Old 26th Apr 2019, 18:31
  #4374 (permalink)  
 
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Inherent stability and "help

Salute!

@ 100% We went thru a lot of the issue concerning stability and such on the 447 thread.

The more we saw of the AB330, and the FDR traces, the more it was apparent that the thing was and is a good design. So smooth an entry to the stall that the crew did not understand why the sucker wasn't reponding to stick commands.

Many of the bent wing designs have obvious clues when you are gettiing to high AoA. Buffet, wing rock, maybe aileron reversal and so forth. Others are smooth and stick shakers or pushers can save the day.

The AB330 does not appear to be statically neutral from what we saw, but the control laws make it appear so. If you use a gee command for pitch, then you will not have speed stability WRT AoA or Q. Duhhhh? Then I see the 737 with the STS kludge and I cannot find enuf early 737 data to indicate a need for the STS when the dinosaur model was certified.

One and not the only reason that a good FBW implementtion helps the $$$, is you can fly with less trim drag by using the stab to keep the tail up than forcing the nose down. My trusty Viper was and is the classic case. However, I do not think that Airbus developed the 320 and subsequent FBW models to be inherently speed neutral or have much longitudinal stability issues. Sure, you could get away with some aft cee gee, but could always fly the plane as you would any other. I"m not even sure if the USAF F-22 and F-35 have the same longitudinal stability properties as the F-16. Their demo routines show stuff that we Viper drivers couldn't dream of, primarily the really high AoA stuff.

Gums sends...



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Old 26th Apr 2019, 20:45
  #4375 (permalink)  
 
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Learned a lot

Amazing thread. I always believed that the 737NG was a redesigns similar to the 747-400 - shocking to here it is still FBC.
I saw that reference was made to the AF447 crash - truly shocking. And very helpfull. The AF crash makes very clear that problematic pilot skills are not at all related to the mother country of the airline in question. And that makes the discussion about possible pilot shortcomings in relation to the 737Maxs crash bearable, because one thing is clear: Nothing becomes worse than errors made during the AF crash, and this was a true European airline’s crash.
(Same goes for AirEgypt 990 and Germanwings 9525)

Written by a surprised Pax.
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Old 26th Apr 2019, 21:18
  #4376 (permalink)  
 
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Fly the damn aircraft....

Originally Posted by HundredPercentPlease View Post
Simple.

Remove the flaw. Either remove the aerodynamic stability problem or make the FBW fix a proper one (like an Airbus, triple inputs, 14 computers, multiple layers of automatic or selectable degraded flight modes).

Train the pilots. If a single failure (here AoA) causes a monster, then prepare the pilots by training.

As someone who has moved back and forth, twice, between the 737 and A320, I can't begin to describe how lowly I view the Renton tractor. Boeing made a flawed aircraft and failed to mandate sufficient training. The pilots are as much victims as the passengers. No doubt at all.
There will never be a flawless aircraft or flawless maintenance or flawless training or flawless pilots. But at the end of the day, it is the pilots and their passengers who will be on the receiving end of these inevitable flaws. Thus our focus and our determination to overcome those flaws ought to be greater.

Throughout the history of aviation, pilots have been handed unique malfunctions or adverse situations for which there was no prior history, no procedure, no checklist. Many of these situations were also initially confusing, mentally taxing, and potentially paralyzing. Some crews performed, if not flawlessly, at least well enough to stabilize the situation and get the aircraft safely back to earth. Some crews did not.

In a remarkable number of these events, the difference between success and failure came down to the exact same answer - the crew's ability to overcome the startle effect, look past the distractions, and focus on the basics of flying the aircraft. Turn off the automation, set the proper attitude, set the power, trim out the control forces, monitor the performance, move the aircraft away from the threat. The pilots don't have to be perfect or diagnose the problem right away. Fly the aircraft and buy some time. Very, very few of our non-normals need to be executed so fast that we can't first devote the majority of our attention and the necessary time to flying the aircraft.

Training is key, but it has to be the right kind of training. Training scripts in the simulator where you pretty much know not only the problem but the answer ahead of time do little to prepare a pilot for the visceral challenges of the unexpected. Overemphasis on automation to the point that even seasoned pilots feel that tad bit of discomfort when the autopilot and autothrottles click off is a definite warning sign. When all goes to hell, do you have a good idea - right now - where the aircraft pitch and power and airspeed should be for takeoff? low altitude? high altitude? missed approach? Do you know your memory items and limitations cold? If not, you have some homework to do.

It is too late to save the crew and passengers of these two accident, but it is not too late to learn from them. Some commercial pilots have stated here that they could not have done any better, and I'm here to say that is a cop out. If you are a commercial pilot and feel that you cannot - under the duress of distracting warnings and information - turn off the automation, set a reasonable pitch and power setting, establish a climb, hold a heading, and trim the controls as necessary, then you need to do something about that right now.
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Old 26th Apr 2019, 21:58
  #4377 (permalink)  
 
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Originally Posted by HundredPercentPlease View Post
When I was trained on the 737 (classic and NG), the stab trim runaway was a runaway - where the trim wheel ran continuously. We would identify it as a runaway, because it was continuously running, and flick the switches.

1. MCAS activation is not continuous, it's bursts.
2. The 737 trim system likes to provide bursts of random trim at certain times (STS) so bursts are considered normal.

This is why the Boeing excuse "they should have done the runaway stab QRH to fix the MCAS problem" is a load of utter nonsense. 737 Driver - pinning this on lack of airmanship will costs lives in the future.
Back in November 2018 Boeing issued a bulletin about the MCAS Stab Trim problem and many airlines responded by removing the word “CONTINUOUS” from the Runaway Stabilizer checklist.



Last edited by Lost in Saigon; 27th Apr 2019 at 03:24. Reason: Photo of checklist added
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Old 26th Apr 2019, 22:01
  #4378 (permalink)  
 
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Originally Posted by Lost in Saigon View Post


Back in November 2018 Boeing issued a bulletin about the MCAS Stab Trim problem and many airlines responded by removing “continuous” from the Runaway Stabilizer checklist.

What exactly was the MCAS Stab Trim problem?
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Old 26th Apr 2019, 22:37
  #4379 (permalink)  
 
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Originally Posted by 737 Driver View Post
..., and I'm here to say that is a cop out. If you are a commercial pilot and feel that you cannot - under the duress of distracting warnings and information - turn off the automation, set a reasonable pitch and power setting, establish a climb, hold a heading, and trim the controls as necessary, then you need to do something about that right now.
Of course everyone here can do that. The ET crew could do that. Do you really think that an 8000 hour 737 captain didn't know how to do that?

You are missing the point - which is why they didn't do that. Or maybe why they couldn't do that. Or most importantly, why you may not do that as some point in the future.

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Old 26th Apr 2019, 23:15
  #4380 (permalink)  
 
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Originally Posted by Bend alot View Post
What exactly was the MCAS Stab Trim problem?
The “problem” was explained in the Boeing Bulletin issued back in November 2018 after the Lion Air accident.

“Uncommanded nose down stabilizer trim due to erroneous Angle of Attack during Manual flight only”

Ethiopian airliner down in Africa
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