Another (2nd) 737 Max 8 crash

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#2203080 21-Mar-2019 21:06

Technofreak:

dafman

Yes, I may be making some assumptions but I also speak with a little bit of knowledge on the subject. I'd like to think if I was faced with a similar situation I'd know how to handle it. I am a pilot myself and I don't like casting aspersions on fellow pilots but evidence so far shows other pilots have dealt with this problem successfully by following the correct procedures.

One question that has to be asked is why did these two crews not manage to do so? That shows there is a deficiency somewhere. That can mean a deficiency in training which is not a direct reflection on the individual pilots. So was it lack of training or something else?

Boeing did not tell anyone about MCAS prior to the Lion Air crash - I don't know how you can blame the pilots there, the first pilot must have in his personal time discovered the hack to disable trim control without being formally trained for it.

After that Boeing implemented training on how to disable MCAS but the training must have not yet disseminated throughout the world OR, there was something else Boeing is not telling us about.

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#2203085 21-Mar-2019 21:21

Batman:

Boeing did not tell anyone about MCAS prior to the Lion Air crash - I don't know how you can blame the pilots there, the first pilot must have in his personal time discovered the hack to disable trim control without being formally trained for it.

After that Boeing implemented training on how to disable MCAS but the training must have not yet disseminated throughout the world OR, there was something else Boeing is not telling us about.

I'm not familiar with the Boeing system but my understanding the "hack" you refer to was actually a "formally trained" for action to be applied in the event of a elevator trim malfunction, which is what the MCAS fault would have looked like.

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#2203198 22-Mar-2019 03:52

It certainly wasn't a 'hack' but a - relatively obscure - procedure buried in the back of the quick reference handbook.
Something way down the checklist of the previous iteration of the aircraft that should have been front and centre on this one due to the new MCAS system.
The warning light that would have pointed to this particular issue ahead of everything else was 'optional' and not installed on this aircraft.

It comes back to Boeing saying "the new MAX is just like the old 737 NG's, if your pilots can fly those they can fly the new one" - and the FAA's approval of that.

The Batik Air pilot along for the ride on October 28th was able to recognise it as a trim issue and switch that system off - while the pilot and co-pilot, under pressure, were still trying to figure out what action to take. There's a big question as to why this wasn't passed on to the following day's crew.
The pilots request for maintenance after landing that aircraft didn’t mention they had been getting a stall warning since just after takeoff as a result of that faulty angle-of-attack sensor.

That sensor was still giving false readings the next morning when the flight that crashed took off, according to flight data.
Compounding the problem, MCAS was set to activate on readings from just one of it's two Angle of Attack sensors (something Boeing has now issued a software fix for).

On that flight, the pilots - under immense pressure as the aircraft apparently tried to kamikaze itself into the ground - couldn't figure out what procedure to follow.
The pilot had handed over control and was still reading the manual when they crashed.

Boeing underplayed the differences of the new aircraft enough that the Captain of the Ethiopian Airlines flight hadn't yet even practiced on a simulator for the Boeing 737 Max 8 - he was due for training at the end of March. The only 'requirement' was a computer delivered training course. His co-pilot had basically student pilot hours.

As well as software fixes Boeing has decided to retrofit the (previously extra cost) optional warning light to all existing MAX aircraft.

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#2203259 22-Mar-2019 10:41

Many of the media reports are overlooking some basic flying principles.

Power plus attitude equals performance.

There have been reports of erroneous airspeed indications. I think the pilots may have been confused by the false stick shaker operation and high nose attitude, then concluded the airspeed indications were erroneous.

If you set the power setting for level flight and set the nose attitude for level flight you WILL get a normal speed for level flight. End of story. It doesn't matter what the airspeed indications are. It's no different to driving your car on a level piece of road, providing you're in the same gear a given throttle position will give always give the same speed within normal margins.

Both flights that crashed were in visual conditions, the pilots didn't need to use the attitude instruments. The only instruments they needed were the gauges to show how much power they had set. This is flying 101.

When the trim system doesn't perform as expected and you are having difficulty controlling the attitude, turn the electric trim system off and revert to manual trim.

While it might not be so for all aircraft, this has been a memory item on any aircraft I have flown, and it from what I know it applies to the 737. On the 737 it's my understanding, once the electric trim has been disconnected the only way the trim can be changed is by the pilot. The automatics cannot interfere.

I understand there are several incident reports on the FAA database about similar trim problems on 737 Max aircraft in the US. Not one of them crashed.

P.S.

Some further thoughts on the implementation of the MCAS system. Its a system that drives the automatic (electric) trim to add control feel in certain conditions to give the pilot the expected control forces in these conditions. The way in which it interfaces with the trim system is similar to the auto pilot. The pilot can also control the electric trim using toggle switches on the control column. Electric trim systems can fail or the systems driving them can give erroneous signals causing the trim to operate when it shouldn't. That's why the cut off switches are fitted.

Do I need to know that the MCAS system is installed before I can deal with a failure where a trim control system (control wheel toggle switches, Autopilot or MCAS) is give erroneous outputs to the trim system?
No I don't.
Should I be made aware of the system?
Most definitely.

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dafman

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#2203342 22-Mar-2019 12:57

So it looks like safety features are 'optional'; something I've come to expect from Ford, but not what I would have expected from a major manufacturer of consumer aircraft. Link here

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#2203345 22-Mar-2019 13:09

I'm no pilot, and I am 100%ignorant of all the basic things that all pilots would know and memorised and can recite at the drop of a hat.

All I know is the whole world have grounded the planes and I presume there are systemic failings that do not necessarily help pilots under the adrenaline and psychological pressure of a crisis.

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#2203385 22-Mar-2019 14:15

Some of the comments in this TheRegister article are very knowledgeable, worth a ten minute read:

https://forums.theregister.co.uk/forum/all/2019/03/19/boeing_repeats_737_max_software_update_promises/

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#2203427 22-Mar-2019 15:46

Technofreak:

One question that has to be asked is why did these two crews not manage to do so? That shows there is a deficiency somewhere. That can mean a deficiency in training which is not a direct reflection on the individual pilots. So was it lack of training or something else?

To me that's also the key thing.

Regardless of the AOA issues and whether MCAS is broken or not, in both cases killing the auto trim would have probably saved the plane as it did with the Lion Air aircraft the day before.

There has been nothing to suggest so far the Ethiopian pilots flicked these switches, and instead appear to have battled with the same 6s cycles of the plane pitching by itself under the control of MCAS.

The thing that really puzzles me is why these pilots after months of coverage of the issue, and supposedly having undergone additional training since the Lion Air crash didn't simply flick these switches to potentially save the aircraft.

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#2203634 22-Mar-2019 21:57

sbiddle:
The thing that really puzzles me is why these pilots after months of coverage of the issue, and supposedly having undergone additional training since the Lion Air crash didn't simply flick these switches to potentially save the aircraft.

That puzzles me too, very very much. I cannot believe the pilots of these aircraft were not aware of how to deal with a trim problem which is what this essentially was. I also cannot believe they had not made it their business after the Lion Air crash to find out all they could about the quirks of the 737 Max.

I fear this whole thing has now become very political in several areas and I'm not sure we will ever get to know the total truth. I think the aircraft will be made a scapegoat and the designers will be hung out to dry. There are people with agendas and people covering their backsides.

Whether it's proven to be needed or not there will be a software change, and other possible changes. Even though it seems likely there are deficiencies in the way some airlines have operated these aircraft to a point Boeing will swallow a rat to not upset customers.

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#2203719 23-Mar-2019 07:21

Sounds like you are familiar with how to fly an aircraft but perhaps not about human error.

In commercial aviation my understanding is that the blame is rarely solely pinned on the pilot or the manufacturer, but rather the systems around the complex human - machine interface that prevent disasters.

From having set printed checklists so that pilots do not need to recite on demand, to the colour of switches and where they are placed so the pilots can find them. From enforced rest so pilots are not tired when they are in charge, to practising exactly what to say and how to say to maximise teamwork during time of high adrenaline and psychological tunnel vision where decision making is at the lowest no matter how many times you have memorised checklists. (this is why the third pilot who has no responsibility in manning the aircraft had superior ability to correctly diagnose the problem)

I am sure the investigation will look at all these things from how the plane got certified, to how they can layout the plane better to why American planes didn't crash and then the pilot trainings of the affected airlines, not sure if it will extend to all pilot training issues in certain airlines. But such an investigation takes time.

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#2203721 23-Mar-2019 07:44

Batman

I know about all those things. You're not telling me anything I don't know. I have attended many Human Factors and CRM sessions.

Of course there's several factors in any accident. James Reason is famous within aviation Human Factors training for his Swiss Cheese model.

The pilot is the last line of defence in many cases. Unfortunately from what I can tell the last line of defence failed in these two accidents where it hasn't on several similar incidents elsewhere. The question has to be asked. Why?

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#2203776 23-Mar-2019 11:51

Some interesting analysis and an interesting theory on Leeham news

https://leehamnews.com/2019/03/22/bjorns-corner-the-ethiopian-airlines-flight-302-crash-part-2/

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#2203780 23-Mar-2019 12:08

Is the core problem that the 737 MAX is an example of aircraft that has been developed one generation too far in size and power?

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#2203783 23-Mar-2019 12:14

sbiddle:
Some interesting analysis and an interesting theory on Leeham news

https://leehamnews.com/2019/03/22/bjorns-corner-the-ethiopian-airlines-flight-302-crash-part-2/

I think that article is suspect. I may be wrong but my understanding of the 737 trim is it uses screw jacks not hydraulics rams, so I think the blow back theory is incorrect. Makes tou wonder what else is wrong in that article.

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#2203784 23-Mar-2019 12:30

Technofreak:
sbiddle:

Some interesting analysis and an interesting theory on Leeham news

https://leehamnews.com/2019/03/22/bjorns-corner-the-ethiopian-airlines-flight-302-crash-part-2/

I think that article is suspect. I may be wrong but my understanding of the 737 trim is it uses screw jacks not hydraulics rams, so I think the blow back theory is incorrect. Makes tou wonder what else is wrong in that article.

Blow back is of the elevators, not the horizontal stabiliser (tailplane) trim function.

Yes trim uses a screwjack, but the elevators use hydraulic rams, as just about every aircraft.
The thesis being advanced is that once you exceed a certain airspeed, the aerodynamic forces on the elevator are too high for the hydraulic elevator control system to overcome, so no matter how hard the pilot pulls on the yoke, the elevators won't move because they are being blown back down.

It unfortunately provides the last "hole in the swiss cheese slices" that have to line up to cause the fatal crash/es

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