Ethiopian plane crash

[IanH755]

El stovey said:

IanH755 said:

pushthebutton said:

Final one from me.

Let's assume a scenario where a 737 Max is departing an airfield and at some point there is a failure related to an AoA sensor. An average Line Pilot will know that this is one of the feeds to his/her instruments and may have an impact on their reliability. This pilot scans their own instruments plus, occasionally those of their colleague and one of the pair notices a discrepancy, the start of a divergent trend.

Just to clarify this, on the "base model" 737 MAX there is no viewable AOA information displayed anywhere, there is no stand-alone gauge for it nor is it displayed on any of the MAX display System (MDS) screen, unless you paid the "extra" to equip it, which very few companies did.

The full set of MDS screens can be seen here but here is the Primary Flight Display where, if you paid extra, it would appear but, as you can see, this is the base model without any AOA info -

I think you’re talking about an optional display on the pfd, pushthebutton is talking about the single external sensor giving the data.

His point is that, is you have conflicting information from the faulty sensor (outside the aircraft) pilots should cross check their instruments (speed, pitch power etc) and work out which ones might be faulty.

However in the 737 MAX the pilot will not know that his AOA is sending faulty info because they have no way of viewing that info unless they paid extra, so there is no "conflicting info" for the pilots to cross-check against to find a faulty one because there is no AOA info displayed in the first place.

This is why some companies paid the "extra" to get both pilot and co-pilot their AOA info plus a "conflict of info" warning light to grab the aircrews attention should the two AOA probes show different info.

[anonymous-user]

El stovey said:

MX5Biologist said:

How is it that a safety feature is an optional extra? I can't imagine including it makes a big difference to the cost of the aircraft, begging the question why wouldn't airliners stump up the cost/ Boeing absorb the cost.

Is this akin to ordering a car, but paying extra for seatbelts?

It isn’t optional any more. When it was put on, nobody thought it would be so important and didn’t expect the MCAS to cause crashes.

There are plenty of “safety features” on aircraft and in airlines that are dictated by cost though
and vary from operator to operator.

How well are the crews trained? How experienced are they? How hard do they work? How well maintained are the aircraft? Are there extra commercial pressures? How much fuel are they carrying? Etc etc

Edited by El stovey on Monday 8th April 11:57

Still, I'm surprised; following the disappearance of a Malaysian airliner a few years ago, it seemed that at the time the aircraft could have been located much more quickly and accurately but for the non-activation of a Inmarsat tracking service. I gather that at the time of MH370s disappearance, more than 90% of airliners were capable of transmitting said tracking data, but many airlines didn't bother.

I expect the person who decided this MCAS would never cause a crash is somewhat fearing for his/her liberty.

[pushthebutton]

IanH755 said:

However in the 737 MAX the pilot will not know that his AOA is sending faulty info because they have no way of viewing that info unless they paid extra, so there is no "conflicting info" for the pilots to cross-check against to find a faulty one because there is no AOA info displayed in the first place.

This is why some companies paid the "extra" to get both pilot and co-pilot their AOA info plus a "conflict of info" warning light to grab the aircrews attention should the two AOA probes show different info.

Preliminary Report said:

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.

There was conflicting info wrt the airspeed, altitude and flight director pitch bar values as per this preliminary report.

This was apparent just after lift off.

[anonymous-user]

IanH755 said:

However in the 737 MAX the pilot will not know that his AOA is sending faulty info because they have no way of viewing that info unless they paid extra, so there is no "conflicting info" for the pilots to cross-check against to find a faulty one because there is no AOA info displayed in the first place.

This is why some companies paid the "extra" to get both pilot and co-pilot their AOA info plus a "conflict of info" warning light to grab the aircrews attention should the two AOA probes show different info.

The conflicting information will be conflicting speed altitude data and stall warnings etc.

[stevemcs]

Its easy for people to say you should have done this but i guess when you are less than 10,000 feet from the ground in an aeroplane that has known issues and keeps wanting to head into the ground with warnings sounding all over the place and 160 people behind you things are not as easy as in the simulator, get it wrong in that and you can have another go, in real life you have less than 120 seconds.

[dvs_dave]

pushthebutton said:

zombeh said:

I think they're sensible questions to ask...

Is it obvious what the current stabiliser trim setting is? Or is it plausible that having moved it back enough to feel significantly less force on the controls that they thought they've moved it far enough?

Thanks zombeh.

You're in my head.

It'll be obvious through the forces on the control column.

It's possible to hold a fair amount of pressure through control column and against the trim and keep the aircraft on the desired trajectory. Any residiual pressure could be trimmed out if desired/required.

Edited by pushthebutton on Monday 8th April 15:00

Something that’s not been made clear. When MCAS is doing its thing, are the trim wheels not whizzing around, making it visually obvious that it’s winding on a ton of nose down trim? If so, then is it not also obvious that to recover you’ll need to wind it back a similar amount to get back to where it started? Is there not a clear gauge or instrument showing the current trim position?

[alfaman]

stevemcs said:

Its easy for people to say you should have done this but i guess when you are less than 10,000 feet from the ground in an aeroplane that has known issues and keeps wanting to head into the ground with warnings sounding all over the place and 160 people behind you things are not as easy as in the simulator, get it wrong in that and you can have another go, in real life you have less than 120 seconds.

apparently the plane vanished from radar at 10,800 feet (straits times article) - if so .... that is about 3000 foot above the ground.

at over 500 knots (close to 600 mph) - it would take *About 7 seconds* to hit the ground at a descent angle of 30 degrees (to descend 3000 feet )

600 mph is a mile every 6 seconds ... around 12 seconds per mile of vertical height at 30 degrees.

... plenty of time to follow the multiple steps needed and/or figure out what is happening ??

[skwdenyer]

alfaman said:

apparently the plane vanished from radar at 10,800 feet (straits times article) - if so .... that is about 3000 foot above the ground.

at over 500 knots (close to 600 mph) - it would take *About 7 seconds* to hit the ground at a descent angle of 30 degrees (to descend 3000 feet )

600 mph is a mile every 6 seconds ... around 12 seconds per mile of vertical height at 30 degrees.

... plenty of time to follow the multiple steps needed and/or figure out what is happening ??

Once the aircraft was pointing at the ground, AIUI:

- the pilots were initially close to the ceiling under negative G loading;
- the stabiliser loads were so great as to prevent any trimming by any means;
- when not on the ceiling, the crew were pulling back on the columns for all they were worth.

Once it finally pointed at the ground, there seems to have been little left in the cupboard.

[alfaman]

MX5Biologist said:

I expect the person who decided this MCAS would never cause a crash is somewhat fearing for his/her liberty.

and I expect who ever in Boeing thought or decided the following will be stting themselves

1/ Inputs from AoA are always 100% accurate and consistent ... let’s not spend a few $ on any cross checks- one input is just fine.

2/ if computer says the AoA jumps by around 60 degrees in less than a second ... that’s also believable because aircraft can actually behave like that in real life (not) - no need for a ‘sanity check’ or cut out

3/ no need for extra pilot training - we don’t want to slow up certification and sales

4/ we’ll design the safety system so that even if the plane is hurtling to the ground at X,000 feet per minute it stays locked on .... cos the system knows better than the pilots

5/ no need to include AoA indicators for free, or indicate when MCAS has taken control .... let’s keep it simple and cheap.

[hutchst]

There was no need to fit them for free. They could have added the $25,000 to the basic price of an aeroplane that was already costing what, $100 million? In context, that's the equivalent of about £5 on the price of an average new family car. It would have had absolutely zero effect on sales.

No, the problem lies in the culture at Boeing. It's rotten. Remember this is an organisation that didn't need to bother with separate Chairman and CEOs like normal organisations.

[stevemcs]

alfaman said:

apparently the plane vanished from radar at 10,800 feet (straits times article) - if so .... that is about 3000 foot above the ground.

at over 500 knots (close to 600 mph) - it would take *About 7 seconds* to hit the ground at a descent angle of 30 degrees (to descend 3000 feet )

600 mph is a mile every 6 seconds ... around 12 seconds per mile of vertical height at 30 degrees.

... plenty of time to follow the multiple steps needed and/or figure out what is happening ??

I thought it was 40 degrees ? Boeing apparently stated in the handbook for the 737-200 to use the roller coaster manouver to gain height, pull up, release, adjust trim, pull up, release, adjust trim etc ... Boeing probably played a bigger part in the crash than the crew.

[alfaman]

Yeah - think it was 40 degrees.

So even quicker

I just know the sine of 30 is 0.5 (for the example )

[red_slr]

The more I read about this the more I think several people at Boeing should spend a long time in prison. Will never happen though.

[hutchst]

It's a huge leap from negligence to criminal intent. I think they're more likely to see the inside of the big house if they try to cover it up (pervert the course of justice in our terms)

But the costs to Boeing are going to be huge. Tens of billions. Damages, rectification costs, lost production, cancellations and lost sales.

[KTF]

I would imagine that Boeing are still sending them down the line and if the price is right someone will buy them regardless.

The lead time on an Airbus equivalent will be longer than staying on the list for a Max 8 so, whilst they may get a few orders switching over, the majority will stay put.

[stevemcs]

I guess it depends on how flawed the system is, Boeing are going to know more than anyone what needs to be done but given they have been aware of it for a reasonable time you would have thought they would have come up with a fix by now. Given they build over 50 per month they could have caught it very early on, they have cut back on production by around 8 per month but trying to find spaces for 100 aircraft could prove interesting.

I'm not sure criminal proceedings are right, at the end of the day with anything involving aircraft its more important we learn from it and make them safer rather than trying to punish them. Providing the order books don't drop too much i'm sure any fines and loss of earnings will be small fry, however I guess that depends on if Boeing can prove it was the flight crew that caused both crashes rather than the 737.

The other point is will the public lose faith in them ? after all they will only see the 737 part on the safety sheet and won't care if its an 800 or Max 8. It does seem Boeing have tried to push the 737 too far though and that it certainly has a number of issues to deal with. You would not expect any crew to have to work around things on such a new design and certainly not at a very low altitude when things start to go wrong.

[George Smiley]

Indeed, it won’t count for much but I won’t fly a max. Engines that can cause an unrecoverable nose up controlled by lawn dart MCAS- no

[hutchst]

stevemcs said:

I guess it depends on how flawed the system is, Boeing are going to know more than anyone what needs to be done but given they have been aware of it for a reasonable time you would have thought they would have come up with a fix by now. Given they build over 50 per month they could have caught it very early on, they have cut back on production by around 8 per month but trying to find spaces for 100 aircraft could prove interesting.

I'm not sure criminal proceedings are right, at the end of the day with anything involving aircraft its more important we learn from it and make them safer rather than trying to punish them. Providing the order books don't drop too much i'm sure any fines and loss of earnings will be small fry, however I guess that depends on if Boeing can prove it was the flight crew that caused both crashes rather than the 737.

The other point is will the public lose faith in them ? after all they will only see the 737 part on the safety sheet and won't care if its an 800 or Max 8. It does seem Boeing have tried to push the 737 too far though and that it certainly has a number of issues to deal with. You would not expect any crew to have to work around things on such a new design and certainly not at a very low altitude when things start to go wrong.

Do you think the owners of around 400 Max 8s currently parked up around the world for more than a month now are just going to shrug their shoulders and put it down to just one of those things? I suspect that alone is costing Boeing $5m a day.

[George Smiley]

Which means financial pressures will force the issue

[skwdenyer]

hutchst said:

It's a huge leap from negligence to criminal intent. I think they're more likely to see the inside of the big house if they try to cover it up (pervert the course of justice in our terms)

But the costs to Boeing are going to be huge. Tens of billions. Damages, rectification costs, lost production, cancellations and lost sales.

Criminal negligence in engineering is a thing - no need for intent.