Ethiopia crash

[Bob Scott 7,716]

Those extreme forces were largely a consequence of letting the airspeed run away from them.  If you've got full nose-down trim and you let the jet continue to accelerate almost to Vmo, yes, extreme force will be required to turn the jackscrew manually against those heavy air loads.  A runaway trim resulting from the more commonly known causes--a stuck relay, bad switches or a wiring fault, would also be expected to recur if the system were left activated.  The MCAS may be a new mode of causation for runaway trim, but the corrective action and the implications for flying the aircraft are pretty much the same no matter what causes it.  If you're getting uncommanded trim movement for ANY reason, you don't leave stab trim on.  Turning that trim system on again strikes me like restarting an engine after shutting it down for an engine fire.  "Hey, the fire is out, let's start that bad boy back up again." 

The implications for control of a grossly out-of-trim aircraft as the result of a runaway are the same as well.  Pushing the airspeed to the far limit of the flight envelope with a known flight control problem is just not good airmanship.  Pitch, power, and airspeed...the basics you should always go back to.  Why this is so difficult for some to understand...

 

[KevinAu 441]

1 hour ago, Bobsk8 said:

....until MCAS kicked in again ( which they knew nothing about)....

....so a crash was the guaranteed result. Why this is so difficult for some to understand, is what confuses me. 

Again, they were informed of mcas and given a procedure that explicitly said to leave the trim off once turned off, a few months prior already. Lest we forget, the very first crew to ever encounter the mcas fatal flaw....survived by turning the trim off and leaving it off. The fo even had enough awareness of this issue that he thought to turn it off without prompting from the captain or referencing any checklist. And leaving the trim off in a runaway situation is just something that has been hammered into us from the beginning. Kind of like pitching for glide speed when you lose your engine, or stepping on the ball, etc. Just one of those aviation conventional wisdoms.  I get why they did it. The manual trim was too hard to move and the plane was significantly nose heavy. I get it. But you also need to try to understand that from the viewpoint of a pilot, that by choosing to turn the trim back on, you are also knowingly going against checklist procedure, and inviting the trim to runaway on you again and make the situation worse. 

And again, what is with this fatalism? I’ll say again in black and white, they had a chance at surviving if they hadn’t turned the trim back on. They may still have crashed eventually, but they wouldn’t have died by letting the mcas to instantly nose them into the ground at that moment. And every moment you buy yourself at staving off death is another moment you give the right solution a chance to pop into your head. 

[threexgreen 3,135]

I've watched several of the videos that have been posted here which showed how difficult it can be to trim manually via the wheels. Question: Were those demonstrations done at speeds close to Vmo, basically at the speed that the Ethiopian aircraft was flying at when they attempted to trim via the wheels?

The Lion Air flight that continued with manual trim to their destination shows that at normal flight speeds, trim control via the wheels is possible. Which would suggest letting the airspeed run away was what put the Ethiopian crew into a state where there was basically no way to trim the airplane other than trying to switch the trim system back on with manual trim becoming impossible. This seems like a significant mistake to me, agreeing with what others said.

This in turn I think makes human factors something that needs to be seriously looked at. The Lion Air crew that crashed didn't know about MCAS, let alone about what happens when that AoA vane fails and MCAS kicks in when it's not supposed to in it's old, flawed design. Making the mistake of not switching off the system as a result of confusion arising from an unusual stabilizer runaway pattern and all the warnings going off making no sense, I think it's no surprise the crew made the mistake.

The problem in the Ethiopian case though is that, as has been pointed out, they were informed about the system, what happens when it goes belly up as well as about what to do to tackle the situation. This included what types of warnings occur and that they are limited to the Captain's side (including the stick shaker). It seems, however, they were still caught by surprise enough to forget about throttle and speed which proved to have serious consequences. That's where I'm unsure about human factors. One would tend to say they were informed and knew but failed to work it out nonetheless, hence making pilot error a contributory factor in the overall cause of the accident. That's as far as theory goes.

In practice, is it reasonable to say a crew who has been informed but not specifically trained can be expected to avert that kind of accident?

[Garys 209]

In regards to the EXTREME FORCES lets not forget about the elevator feel shift function. Although it can also be instigated by the SMYD during a stall by reducing hydraulic pressure, in flight the faster the airspeed the harder the pressure will be on the controls because that's what those two static probes on the Vertical stabilizer are there for, they directly put static pressure on the feel system.  So regardless of what caused the initial aircraft nose down attitudes -  They had no chance of trimming manually at those airspeeds as has been demonstrated as they were the ones who continually put these EXTREME FORCES on the airframe by keeping the throttles firewalled even after the uncommanded nose down actions and the elevator feel shift function would have made the controls extremely heavy as well. Managing airspeed was crucially important and these mistakes made during the recovery phase will be found to be a big contributing factor in this accident. Regardless of what side of the fence you sit on, learn more about the aircrafts systems and how they factored into the recovery or lack thereof and why.

Edited May 21, 2019 by Garys

[Bob Scott 7,716]

1 hour ago, threegreen said:

In practice, is it reasonable to say a crew who has been informed but not specifically trained can be expected to avert that kind of accident?

The reality is that there is not (and never will be) enough training time available to practice every conceivable emergency.  You get a small cross section of situations in the box that exercise the major skill sets (e.g. single-engine ops, rapid decompression/emergency descent, ground evacuation etc) but the number of possible emergency situations are legion and practicing them all is just not possible in the limited time alotted.  That's why we have QRH checklists and why pilots are expected to understand system operations in detail.  You are absolutely expected to work through all but the most catastrophic emergencies using basic cockpit resource management, the available procedural guidance, your systems knowledge, and your flying ability and proficiency.

For example, there are myriad possible smoke/electrical fire scenarios, maybe hundreds of them, depending on if it's a component, a bus fault, a wiring fault etc.  No way to practice every variation or even most of them.  You're trained in the basics...like first save the pink flesh (get your O2 and smoke mask on), have one pilot flying, and get the other into the QRH checklist to work through the decision tree and (hopefully) find/deal with the problem.  Depending on what it is (or if you're even able to definitively identify what it is) you may end up having to depower equipment or even entire electrical busses, and both pilots have to put their thinking caps on to make sure they understand the systems implications of what pulling those breakers means.  There are so many possible branches to these kinds of scenarios there's no way to practice them all...but heck yeah, you have to be ready to deal with all of it despite not having seen that exact problem in the sim.

Regards

[BrianW 124]

6 hours ago, w6kd said:

Those extreme forces were largely a consequence of letting the airspeed run away from them.

 

5 hours ago, KevinAu said:

I’ll say again in black and white, they had a chance at surviving if they hadn’t turned the trim back on.

 

2 hours ago, Garys said:

they were the ones who continually put these EXTREME FORCES on the airframe by keeping the throttles firewalled even after the uncommanded nose down actions

Exactly, and here’s an article that goes into all those details. Written by a couple of guys with a lot of experience, not a backyard scientist, or the general media that think aircraft crash because they didn’t file a flight plan.

https://seekingalpha.com/instablog/398764-vaughn-cordle-cfa/5290930-boeing-737-max-8-crashes-case-pilot-error?fbclid=IwAR1YZSOSxznAAJGNHUU4mmx-Y_gSkFBWDEgSikRvXo1Lz7NODddBu5xB358

 

Brian

[n4gix 4,947]

9 hours ago, w6kd said:

The implications for control of a grossly out-of-trim aircraft as the result of a runaway are the same as well.  Pushing the airspeed to the far limit of the flight envelope with a known flight control problem is just not good airmanship.  Pitch, power, and airspeed...the basics you should always go back to.  Why this is so difficult for some to understand...

Bob, do you think that had they brought the throttles back to flight idle, then deployed the spoilers in an attempt to shed excess speed, that they might have unloaded the trim wheel enough to once again use manual trim?

[Bob Scott 7,716]

2 hours ago, n4gix said:

Bob, do you think that had they brought the throttles back to flight idle, then deployed the spoilers in an attempt to shed excess speed, that they might have unloaded the trim wheel enough to once again use manual trim?

I don't know for sure how much of an additional pitch-down moment you'd get if you ripped 'em all the way back to idle...but certainly reduced power and speed brakes to slow down would have reduced the air load on the stab.  But the better solution would have been not to let the speed get away from them in the first place--the severity of the pitch-down forces would have never gotten to the point where the pilots couldn't control pitch with (heavy) control yoke forces, and at normal flying airspeeds they would have been able to move the stab trim with the trim wheels and relieve the heavy control forces.  When they levelled off at 14000 ft, they left the autothrottles on set at climb power (the ATS was left in FLCH mode from the first onset of the problem until they hit the dirt).  That allowed the speed to climb steadily to (beyond, actually) the far limits of the airspeed envelope, and that was a pretty big link in the chain of events, as was the decision to turn the stab trim back on.  Clearly they were task saturated with a pretty serious issue, and left one of the most important flight performance parameters (airspeed) out of their crosscheck, and for a relatively long time, too.  I really think this is one factor in the accident where having an experienced FO on the flight deck might have made a difference.

Cheers

 

[mabe54 17]

https://www.seattletimes.com/business/boeing-aerospace/how-much-was-pilot-error-a-factor-in-the-boeing-737-max-crashes/

I still think the MCAS should have been given its own CB for isolation instead of tide them all up under one (actually a pair of switches). 

n4gix: ... do you think that had they brought the throttles back to flight idle, then deployed the spoilers in an attempt to shed excess speed, that they might have unloaded the trim wheel enough to once again use manual trim?

... and with a nose pointing down and very little altitude left to play with already. A very hard catch 22.

Cheers,

 

[Bob Scott 7,716]

19 hours ago, BrianW said:

here’s an article that goes into all those details. Written by a couple of guys with a lot of experience, not a backyard scientist, or the general media that think aircraft crash because they didn’t file a flight plan.

https://seekingalpha.com/instablog/398764-vaughn-cordle-cfa/5290930-boeing-737-max-8-crashes-case-pilot-error?fbclid=IwAR1YZSOSxznAAJGNHUU4mmx-Y_gSkFBWDEgSikRvXo1Lz7NODddBu5xB358

Another interesting observation in this article I had not seen before...the FO was turning the trim wheel the wrong direction, adding even more nose-down trim to what they already had.  And during the climbout routine, prior to the onset of the problem, the FO had set the wrong altitude in the MCP after repeating the correct altitude back to ATC (undetected and uncorrected by the captain).  The FO's dreadfully low experience level is an established fact.  Beyond experience, however, is the issue of competence, and this has to make you stop and wonder about that, too.

Regards

[honanhal 1,420]

Genuine question for Bob and others pointing to the various mistakes the crew made -- and it's clear at this point that they did make mistakes, understandable or not, that certainly didn't help save the aircraft: in your view, is there actually a reasonable argument to be made that, had the crew not made these unforced errors, this flight could definitely have been saved?

The reason I ask is that from what I've read and seen it's actually far from clear to me that the answer is "yes," in view of the terrain around the airport and the fact that the space of time between the MCAS first engaging and impact was so short. At best, I'm seeing an argument that absolutely flawless decision-making, airmanship, and perhaps a bit of luck could potentially have saved them. I'm also thinking here of the simulations that have been run since the crash which, as far as I know, have all shown that pilots (who are even aware of what's coming and know exactly how to recover from MCAS events) still end up crashing because there's just not enough altitude in play.

If that's the case, and if the answer to whether totally flawless flying could have saved them is in fact "no," it seems a bit hard to understand why we're focusing so much on the crew mistakes -- though mistakes they were. That's not to say there isn't value for future training purposes in dissecting their actions and pointing out their mistakes, to an extent, the same way we do in those cases where the plane does avoid a catastrophic result following an issue. But that's very much not the same thing as establishing those pilot actions (or lack thereof) as a but-for cause of the crash.

To put it a different way: if the wings fall off a hypothetical plane after a bomb going off in the cargo hold, we're simply not going to be looking in any meaningful way at the crew actions as an important factor in the subsequent crash, even if they did things contrary to the QRH or if the FO had relatively few flying hours.

I guess I'm trying to get a sense of whether you think ET302 is more like that hypothetical "wings-fall-off-the-plane" scenario, or more like TK1951, where even though there was a technical issue with the plane that started the chain of events that led to the crash, it's clear that a different (correct) pilot response would have avoided it.

James

[Bob Scott 7,716]

1 hour ago, honanhal said:

Genuine question for Bob and others pointing to the various mistakes the crew made -- and it's clear at this point that they did make mistakes, understandable or not, that certainly didn't help save the aircraft: in your view, is there actually a reasonable argument to be made that, had the crew not made these unforced errors, this flight could definitely have been saved?

From all that I've read, yes.  After the MCAS-driven trim runaway, the aircraft was not unflyable until the crew made it unflyable, primarily by not controlling their airspeed, and by deviating from the abnormal checklist and returning the stab trim switches to normal and leaving them there.

Let's take Southwest 1380, a 737-700 that had a catastrophic t-wheel disintegration on the port engine in April 2018, resulting in a rapid decompression of the cabin when debris from the engine failure caused a window to blow out.  The crew did a good job of dealing with multiple serious problems...the cabin depress, the engine failure and all its sequelae, and potential controllability issues from damage to the left leading edge slats.  The aircraft landed safely with one fatality that resulted from being partially sucked out the window when it blew out.  Now let's suppose that the crew instead didn't get their masks on in time and was incapacitated, or let the aircraft slow to below Vmca after the engine failure resulting in a loss of control, or some other error while handling multiple critical emergencies, and it had instead crashed.  Would it be reasonable to ignore the crew errors and attribute the accident to the engine failure?  No, it wouldn't be.  SWA1380 made it down due to skilled competent crew action following a serious, but recoverable (multiple) emergency situation.  And I think Ethiopian 302 did not make it down due to less than skilled, competent crew action following a serious, but recoverable emergency situation.

Regards

[n4gix 4,947]

2 hours ago, w6kd said:

Another interesting observation in this article I had not seen before...the FO was turning the trim wheel the wrong direction, adding even more nose-down trim to what they already had.  And during the climbout routine, prior to the onset of the problem, the FO had set the wrong altitude in the MCP after repeating the correct altitude back to ATC (undetected and uncorrected by the captain).  The FO's dreadfully low experience level is an established fact.  Beyond experience, however, is the issue of competence, and this has to make you stop and wonder about that, too.

Regards

Thanks for the link to that very well written and cogent analysis. Those two certainly have the bona-fides to author such a piece. I was not previously aware of the trim wheel being trimmed ND rather than NU!

[KevinAu 441]

1 hour ago, honanhal said:

Genuine question for Bob and others pointing to the various mistakes the crew made -- and it's clear at this point that they did make mistakes, understandable or not, that certainly didn't help save the aircraft: in your view, is there actually a reasonable argument to be made that, had the crew not made these unforced errors, this flight could definitely have been saved?

The reason I ask is that from what I've read and seen it's actually far from clear to me that the answer is "yes," in view of the terrain around the airport and the fact that the space of time between the MCAS first engaging and impact was so short. At best, I'm seeing an argument that absolutely flawless decision-making, airmanship, and perhaps a bit of luck could potentially have saved them.

James

Yes, there is a reasonable argument that the flight could have been definitely saved. The point I have made here before and will make again is that they should have followed their *basic* training. There was no need for flawless or superb piloting skills. They only had to switch their mindset from ‘everyday’ flying to their ‘abnormal’ mindset. That would have triggered the process of calling for memory items, assigning tasks, and opening up the qrh. And there would be no need to be supersmart or flawless after that. Because what they needed to know would have been in print in their hands. The whole point of the emergency training that we do is to give us a tool that takes us by the hand and leads us through a situation we have never encountered before. It is meant for use by flawed and mistake prone humans who can’t remember every detail of the systems. So if they had opened up the procedure to deal with this, they would have seen where it says ‘leave if off, oh eff eff, off’. And maybe they would not have turned the mcas back on and would not have died a few seconds later.

If they didn’t die that moment, they would have been able to struggle along and try to figure how to get the trim back in shape manually. And maybe they would then have realized the power was stuck at full throttle and pulled it back and start working the trim back in. That’s how these multiple problems are solved. We solve them one at a time. But your chances of success go down significantly if you have nothing to fall on. And they acted like they had no emergency training of any sort to fall on. The moment they turned the trim back on, that was the moment the bomb blew the wing off. That was the do not pass go, do not collect $200, stop the checkride, you die in 5 seconds moment. And the only that would have stopped that bomb from going off was reading the checklist. All they had to do was just fall back to the process they demonstrated they learned in training for *any* abnormal. Then they would have pulled out a checklist. And lived.

Edited May 22, 2019 by KevinAu

[KevinAu 441]

3 hours ago, w6kd said:

Another interesting observation in this article I had not seen before...the FO was turning the trim wheel the wrong direction, adding even more nose-down trim to what they already had.

Regards

I don’t think their analysis of the manual wheel being turned the wrong way by the fo is correct. If he was turning it in the nose down direction, he would not have found resistance and declared that it wasn’t working. Instead, it seems more likely that he tried as hard as he could to turn it nose up, couldn’t budge it, and when he let go, the wheel rebounded further nose down. Just watch some of these videos that others have posted here of pilots trying to crank the wheel and losing. The tension rebounds it further nose down.