I'm sure the tens of thousands of flight hours represented by the 737 pilots here counts for nothing. They probably don't know what they're talking about.Originally Posted by TiroFijo
I'm sure the tens of thousands of flight hours represented by the 737 pilots here counts for nothing. They probably don't know what they're talking about.
"Are you ready? Okay. Let's roll."- Last words of Todd Beamer
There is much wisdom in this post.
If it was as simple as flipping the Stab Trim Cutoff switch, this whole thing wouldn’t be where it is. It gets much deeper into certification issues, differences training, both past and future. My educated guess, after peeking behind several curtains, is the end of the year. It took nearly 3 years from the point where the FAA mandated stall training in the A320 series until the first simulator was approved and certified by the test team from Toulouse. Three years. That issue was far less complex than this.
There are many voices yelling “Pilot Error! Let’s move on!” This never has been, nor will it ever will be, an acceptable answer.
Last edited by entropy; 07-01-2019 at 01:59 PM.
Working diligently to enlarge my group size.
Putin is the only one I know who can determine probable cause in a day or a week. Accidents usually involve an error chain, and in this case, the error chain may start with the choice of the engines on the Max, how they interfaced with the airframe, choices Boeing made with the design and implementation of the MCAS system, information that was communicated to the airlines that bought the Max, the common type rating, how the simulators were programmed to depict MCAS failures, the MCAS specific information that was communicated to crews, how that information matched with what actually happens in the real aircraft, and the variation in how the MCAS moved flight controls when failed is a lot to unpack, and is likely to take months not days. I wouldn’t begin to guess what the investigation ultimately concludes and the changes that come out of it. I would guess the investigation will take longer than we initially expected and the causes will be multifactorial.
Likes pretty much everything in every caliber.
Spot on.
Working diligently to enlarge my group size.
Boeing’s 737 Max Software Outsourced to $9-an-Hour Engineers
Apologies if we covered this already. I've been in/out of this thread.Increasingly, the iconic American planemaker and its subcontractors have relied on temporary workers making as little as $9 an hour to develop and test software, often from countries lacking a deep background in aerospace -- notably India.
"No free man shall ever be debarred the use of arms." - Thomas Jefferson, Virginia Constitution, Draft 1, 1776
A few posts up.
In reality - it is pretty common in all industries (my Brother In Law runs a company in the poorer part of Europe that does this very thing) but given everything else - the optics don't look very good.
In my company we have a term for moving work from more expensive economies to less expensive ones, specifically India. It's called "shift left". Anything viewed as rote or transactional gets the "shift left" treatment.
As part of our service governance function, I frequently get involved in discussions or activities around that sort of move.
Chris
I was formally trained in aircraft accident investigation by the Air Force. While there certainly is always an error chain, I’ve yet to hear of a report that found a choice of engine, or the method of engine mounting to be causal. The reports that I spent years reading (and writing) always had multiple “findings,” which were important facts that helped the reader know what happened leading up to an aircraft accident.
From what I know so far, several aspects of MCAS implementation (lack of comparison of AOA inputs, the potential for MCAS to activate several times in sequence, adding more nose-down trim each time) will certainly be “major” findings (meaning that they were major contributors to the chain of events).
But the thing that you never mentioned is the slow and incorrect response by the flight crew (leaving the throttles at takeoff thrust, never activating the stab trim cutoff switches, not sufficiently counteracting the MCAS inputs with the trim switches). And the maintenance practices (on one of the accidents, the AOA sensor had failed on the prior flight - how was that event documented and the aircraft repaired and tested?).
You can bet your ass that any credible report will address those things as “major,” causal findings as well.
In other words, there’s a lot more to the causes of these events than the design of the aircraft and the simulators.
Your post is focused on the very early links in the chain. There are many more, and much more significant links further down the chain. And the links that I’m listing (lack of crew competence, safety and maintenance practices in the airlines involved) have a strong potential to cause future accidents as well - in whatever aircraft they operate.
I fear that we may never see all the information on the causes of these accidents (it certainly isn’t in the interest of the Ethiopian government to point out the causes of their crash that aren’t related to aircraft design). But I hope we eventually see at least some of the truth.
Last edited by GyroF-16; 07-02-2019 at 02:58 PM.
At FlightSafety each year, we are told that about 85 percent of crashes are caused by pilot error, and I sure didn’t mean to exclude those. I have never seen a description of exactly what happened in these two crashes, what the two crews did, and how those actions played out, but that obviously has to be a major part of the analysis.
Either in this thread, or elsewhere, is there a blow by blow account of what failed, what the crew did, and how the accident sequence progressed? Does anyone have access to the AFM and the emergency procedures, including the memory items and relevant checklists?
Likes pretty much everything in every caliber.
There have been several reports and links to reports earlier in this thread. From reading those, it looks like it went generally like this:
Somewhere between takeoff and about 2000 ft AGL, an AOA probe failed. This caused the stick shaker on the side fed by the bad sensor to activate. When the flaps were retracted, MCAS activated, running some nose-down trim. The pilots struggled to hand-fly the jet, as MCAS activated several more times. The Lion Air crew extended flaps again, briefly (which stopped MCAS inputs), then retracted them, got more erroneous MCAS, and nosed into the ground.
The Ethiopian Air crew eventually activated the stab trim cutout switch, (which stopped MCAS inputs) but then returned it to the “normal” position. MCAS then continued to trim nose down. Because the Ethiopian Air pilots also left the thrust levers at takeoff power, the airspeed build to over 300 kts. That led to aerodynamic forces that make manual adjustments to the trim wheel very difficult. Eventually the nose-down trim became too difficult to overcome, and the Ethiopian aircraft flew into the ground.
I do have access to the AFM and emergency checklists, but don’t think it’s wise to post on a public forum, as they are proprietary. I’d be happy to discuss them over beers, though.
Just know that the checklist for runaway stab trim directs a disconnection of autothrottles, and activation of the stab trim cutout switches. If these were both done promptly, and the pilots properly adjusted the thrust setting and hand-flew the airplane competently, all would have been well. I’ll also reiterate that the pilots can always override the MCAS inputs with the trim switch (prior to stab trim cutout). When the aircraft starts trimming itself in a way the pilot doesn’t like, he can always put the trim back where it belongs. Erroneous MCAS activation presents like a simple runaway trim. And the response (and checklist) is the same.
There’s more to it (both in the accident timelines and the crew response), but that’s the essence of it. There was a malfunction of the aircraft (AOA probe). The crew didn’t correctly recognize and respond to it.
Training in runaway trim is part of the 737 type rating, and is familiar to every professional pilot. When the trim runs in a Boeing aircraft, the pilots can see, hear, and feel it happening. And the stab trim cutout switch is checked as part of a challenge-response checklist prior to every flight. So the pilots certainly know where it is, and have been taught what its function is.
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