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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 17th Jun 2019, 10:46
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excellent BBC long article just published on 737 MAX background, almost deserves it's own sticky locked topic mods?

https://www.bbc.co.uk/news/extra/sd9...tle_over_blame

Now I remember why I pay the TV license fee for excellent journalism...

G
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Old 17th Jun 2019, 10:55
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...er, so the one and only new thing in the article is they got the ET boss to respond to the comments the US senator guy made more than a month ago. That article is just churning the same old narrative we have had for 3 months.
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Old 17th Jun 2019, 11:14
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Originally Posted by oggers
...er, so the one and only new thing in the article is they got the ET boss to respond to the comments the US senator guy made more than a month ago. That article is just churning the same old narrative we have had for 3 months.
It does however put everything in one place in a fairly simple to understand format, and from my reading of it didn't seem to make any obvious errors - seemed to be surprisingly well written and researched.

I assume the target audience is a bit wider than readers of this thread.
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Old 17th Jun 2019, 11:33
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Yoko1 puts it better than I did.
From what we know so far of the MCAS debacle, it appears that numerous individuals made decisions that, in the context of their particular view of the problem, seemed reasonable at the time. It was only after the sum total of those decisions came together at a certain place and time that the systematic failure became obvious.
I had suggested that it could have been just one person making a vital decision about say, the use of one vane. It's going to be hard to build a true picture of such scenarios.

Such clear memories for me.
Now we have minimum experience pilots flying aircraft with the same basic DNA as the early transports, who are facing the same issues as 1960s pilots did without the proper training to deal with them.
I sat for over a year with new captains on the 1-11. Many of them came direct from piston engined aircraft. On average, and mostly exactly true was the fact that some of the most bewildering, often bizarre things occurred with the older experienced guys. Right at the beginning of the 'Independents' laying hands on jet transport aircraft, the crews being trained were mostly very experienced - largely from Viscount and Britannia fleets. One example vital procedure they had to accept was maintaining what seemed a low speed after engine failure post V1. On one occasion the skipper let the speed build up, and the very green training guy for some reason thought things looked okay-ish.

An engineer handed the chaps some twigs. Leafy ones. They were in the Undercarriage doors or maybe the wheels, not sure. Anyway, they had dinner, grabbed a map and set off along the centreline. The tree they'd hit was four miles from the runway.


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Old 17th Jun 2019, 11:51
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It does however put everything in one place in a fairly simple to understand format, and from my reading of it didn't seem to make any obvious errors - seemed to be surprisingly well written and researched.
But it doesn't have everything in one place, it has the same information that scores of other articles have in one place, in one place. So for '"well researched" I would say "well syndicated". Subjectively, some may find that "excellent" but I just find it more of the same. Just saying.

Last edited by oggers; 17th Jun 2019 at 12:06.
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Old 17th Jun 2019, 14:52
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Originally Posted by oggers
But it doesn't have everything in one place, it has the same information that scores of other articles have in one place, in one place. So for '"well researched" I would say "well syndicated". Subjectively, some may find that "excellent" but I just find it more of the same. Just saying.
The fact that full power was left selected after takeoff doesn't seem to ba a noticeable comment on theses pages.
Surely the Flight Crews error in leaving TOGA Power set throughout the entire flight until it made a hole in the ground, dwarfs any MCAS part in the accident.
A lightly loaded B737 aircraft, as was ET (destination NBO) at takeoff, would soon break Flap and IAS Limits, and soon lead to a very high work load situation before MCAS was activated by flap retraction.
I am not dismissing the MCAS design problems, and erroneous stick shaker activation, but a lack of old fashioned Airmanship started train of events.
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Old 17th Jun 2019, 15:10
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Originally Posted by cessnapete
I am not dismissing the MCAS design problems, and erroneous stick shaker activation, but a lack of old fashioned Airmanship started train of events.
There we go again with the "lack of old fashioned airmanship"...
Care to elaborate on when, how, what for, the thrust reduction would have to occur ?
According to the Boeing and Airbus test pilots - I mean real pilots, not sim only "instructors" - retarding the throttle is one of the means of pitching down with underslung engines aircraft.
https://filedn.com/lfyhAtb1fbER0sfxD...%2006%3A98.pdf

Not sure pitching down was desirable at any moment of the take off/MCAS event.

Last edited by Fly Aiprt; 17th Jun 2019 at 15:11. Reason: Typo
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Old 17th Jun 2019, 15:16
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Originally Posted by cessnapete
The fact that full power was left selected after takeoff doesn't seem to ba a noticeable comment on theses pages.
Surely the Flight Crews error in leaving TOGA Power set throughout the entire flight until it made a hole in the ground, dwarfs any MCAS part in the accident.
A lightly loaded B737 aircraft, as was ET (destination NBO) at takeoff, would soon break Flap and IAS Limits, and soon lead to a very high work load situation before MCAS was activated by flap retraction.
I am not dismissing the MCAS design problems, and erroneous stick shaker activation, but a lack of old fashioned Airmanship started train of events.
Errors in the crew actions have been previously discussed in several threads, all of which are now locked. Yes, there were a number of errors by the crew, however, it is unclear how much of this was due to individual factors and how much was due to the training and operations environment at Ethiopian. There have been various reports, not particularly well covered by the media, of lapses by Ethiopian in terms of both the overall training and the information communicated about MCAS post Lion Air. IMHO, Ethiopian is getting a huge pass due to all the focus on Boeing's mishandling of the MAX design and their subsequent response.
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Old 17th Jun 2019, 15:23
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Originally Posted by Fly Aiprt
Care to elaborate on when, how, what for, the thrust reduction would have to occur ?
The thrust reduction should have occurred almost immediately once the crew determined the aircraft was not, in fact, stalling. The type of AOA failure they experienced immediately converts to an unreliable airspeed event which calls for (among other things) a reduction in power to 80% N1. This has been discussed extensively in previous threads. The MCAS event doesn't even appear on the scene until the flaps are retracted, and it was highly questionable for the Captain to retract the flaps before the unreliable airspeed issue had been resolved. There is no mention in the CVR transcripts released to date that the crew actually realized they had unreliable airspeed, so the initial crew error was likely a misdiagnosis of the first failure they were presented with.

In case of ET302, a poorly designed system intersected with a poorly prepared crew resulting in a totally avoidable loss of life.


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Old 17th Jun 2019, 16:17
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Interesting announcement from Boeing.

This week we're at the Paris Air Show – the largest aerospace event in the world – to showcase the innovation of our 787-9 Dreamliner, the 777X, and a whole host of other service solutions, defense and autonomous products.
We are also here talking about our enduring values – acting with integrity, delivering first-time quality and putting the safety of our products, the people who travel on and operate them, and our employees above all else.
Watch this video to hear directly from a few of the 150,000 Boeing employees who build our products and model our values every day.

We are re-dedicating ourselves to safety and innovation while keeping our values front and center, because that is the best way to transform how we meet customers' needs.
Ultimately, that’s how we build the future – together.

Erm, that's it.

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Old 17th Jun 2019, 18:25
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Originally Posted by yoko1
so the initial crew error was likely a misdiagnosis of the first failure they were presented with.

In case of ET302, a poorly designed system intersected with a poorly prepared crew resulting in a totally avoidable loss of life.
Thanks for responding, I'll agree with your last sentence.
So it all revolves around failure to associate the stick shaker with this unreliable airspeed issue.
And yet there is nothing fundamentally wrong with keeping T/O thrust when flying away from a low altitude stick shaker alarm, were it not for this MCAS event waiting to happen. Except when considering the chain of event with hindsight.


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Thank you, as you can imagine, those threads have been read and re-read ;-)

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Old 17th Jun 2019, 19:10
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Originally Posted by Fly Aiprt
And yet there is nothing fundamentally wrong with keeping T/O thrust when flying away from a low altitude stick shaker alarm, were it not for this MCAS event waiting to happen. Except when considering the chain of event with hindsight.
I'll agree that most pilots would be reluctant to reduce power close to the ground, but there has to be some point at which the flying pilot should have realized that the stick shaker event is erroneous and the aircraft is climbing and accelerating normally (and if there was any question as to whether the aircraft was stalling, there was no cause to retract the flaps). After that point, it was fundamentally wrong to maintain takeoff thrust. The airspeed unreliable checklist is a memory item for a reason.

I'll confess that I'm a bit perplexed by the perspective that these accidents are a case of event A or event B or event C or event D exclusive of the others. We pretty much know from previous history that aviation accidents are generally the result of multiple causes. Several things came together at the wrong time, and each should be addressed as appropriate. I frankly don't see why Ethiopian's training and operating standards should get a pass just because Boeing and the FAA dropped the ball.
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Old 17th Jun 2019, 20:28
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Originally Posted by Fly Aiprt
A variation on the bicycle theme :
To allow Boeing to stick to the mechanical trim, why do they not gear the manual trim wheels ? In the hub, or with some sort of derailleur since there seems to be some chain linkage ?
If I were Boeing, I'd have been studying such solutions for months now.

Of course that means admitting the manual trim is unmovable in certain trim/speed combinations, but everyone already knows that.
And no doubt serious Airworthiness agencies will mention the point.
As I mentioned above a ratcheting handle could provide up to 3X torque for the pilot inputs assuming the handle was full diameter and folded out at the edge, goes from 0.5 diameter to 1.5X diameter. This is simpler than switchable gearingn needed since it is too slow already.

BTW The envisioned handle would be 'inline' with the wheel, not sticking out to side like the current one, once extended the wheel could be moved with a quick back and forth motion of the handle.
Don't think we know what the actual force requirement are under the assumed conditions.
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Old 17th Jun 2019, 20:46
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Originally Posted by MurphyWasRight
As I mentioned above a ratcheting handle could provide up to 3X torque for the pilot inputs assuming the handle was full diameter and folded out at the edge, goes from 0.5 diameter to 1.5X diameter.
That sounds great in theory, but I suspect that the constraints of the cockpit geometry would mean that each pull of the ratchet handle would only be able to achieve about one-third of a revolution of the trim wheel. So that's about 50 back-and-forward strokes of the handle for each unit (degree) of stab movement.

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Old 17th Jun 2019, 20:47
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To allow Boeing to stick to the mechanical trim, why do they not gear the manual trim wheels ?
It is geared..the gear on the back of the manual trim wheel, is chain driven down to a gear on the front cable drum. Cables running the length of the ac, just the tension required for that is enormous.

A derailleur system would overly complicate an already complex mechanical system. If anything, any sort of variable drive system would have to be shaft driven.

yoko1 if this was as simple as pilot error and training, the ac would not have been grounded for over 90 days (and looking at 270)
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Old 17th Jun 2019, 20:57
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Originally Posted by DaveReidUK
That sounds great in theory, but I suspect that the constraints of the cockpit geometry would mean that each pull of the ratchet handle would only be able to achieve about one-third of a revolution of the trim wheel. So that's about 50 back-and-forward strokes of the handle for each unit (degree) of stab movement.
I suspect your being optimistic with 1/3, might be as low as 1/4. On the other hand back and forth 'pumping' motion is easier to do quickly and with greater force than rotating a wheel since the arm/hand would be optimally positioned and not have dead spots due to biomechanics where the handle is inline with the arm requiring up/down rather than push/pull motion.
Think of a ratchet wrench vs moving a fixed wrench in circles.

Last edited by MurphyWasRight; 17th Jun 2019 at 21:02. Reason: added detail to biomechanics
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Old 17th Jun 2019, 21:02
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Originally Posted by Smythe
It is geared..the gear on the back of the manual trim wheel, is chain driven down to a gear on the front cable drum.
Of course I was considering switchable (mechanical or not) gear ratios.

A derailleur system would overly complicate an already complex mechanical system. If anything, any sort of variable drive system would have to be shaft driven.
If a gear change/derailleur appears beyond Boeing's engineering capacities, they may shop around at any bicycle vendor's ;-)
BTW, weren't the Wright brother bicycle makers ?

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Old 17th Jun 2019, 21:20
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Originally Posted by yoko1
I'll confess that I'm a bit perplexed by the perspective that these accidents are a case of event A or event B or event C or event D exclusive of the others. We pretty much know from previous history that aviation accidents are generally the result of multiple causes. Several things came together at the wrong time, and each should be addressed as appropriate. I frankly don't see why Ethiopian's training and operating standards should get a pass just because Boeing and the FAA dropped the ball.
Of course you're right about the chain of events.
And yet, given what we know at the moment, why would necessarily ET training standards be especially sub-standard as compared to other airlines ?
I've seen so many experienced pilots lose their "basic abilities & airmanship" when confronted to aerobatic situations they have not been prepared to cope with, that I'll tend to cut the crews some slack.
Until more info is coming forth, I'll assume the ET crew was in the "average" line pilot category.

And yes I know that for some forumists here, every professional pilot is "above average" ;-)
Which would prove that their math level is, well, below average^^?

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Old 17th Jun 2019, 21:23
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Originally Posted by Fly Aiprt
Of course I was considering switchable (mechanical or not) gear ratios.

If a gear change/derailleur appears beyond Boeing's engineering capacities, they may shop around at any bicycle vendor's ;-)
BTW, weren't the Wright brother bicycle makers ?
To be practical any mechanical fix would need to fit in the existing manual trim wheel space and could not involve 'remote' control of anything external such as a gear box in the tail.
It must also be certifiable with failure modes that can be analyzed to be extremely unlikely, that by itself rules out anything remotely resembling a derailleur.

Beyond the 'ratcheting handle' the only other thing that springs to mind is a planetary gear arrangement with a locking mechanism to reverts to a solid connection for use once near in trim.
This might fit and be certifiable,especially since most potential failures would result in a jam bypassing the reduction while still allowing wheel to be turned, with others covered by the locking means.
I think I have one year to file the patent papers from time of first publication
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Old 17th Jun 2019, 21:27
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The crews were human, they were bombarded with conflicting information from a system that the manufacturer didn’t provide sufficient documentation for, and weren’t adequately trained to deal with all possible failures.They should never have been put in that situation in the first place.

The accidents could have been avoided by the immediate application of a suitable procedure by crews who understood what was going on. I’m sure most MAX Pilots who were given a thorough ground school on the system and adequate training in the simulator would be able to recognise and deal with the problem. Add in a suitable method of failure warning and a tie breaker for dealing with erroneous inputs, then the accident chain is broken and the holes in the Swiss cheese won’t line up anymore.

The crew and passengers were let down by the entire system at every stage from manufacture to regulatory to training.
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