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Tags airplane incidents , government shutdown

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Old 14th March 2019, 04:10 PM   #81
smartcooky
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Originally Posted by theprestige View Post
That's fine for my purposes.

My concern right now is not so much staying off of 737-MAX flights (though that's also a concern for me). My concern right now is staying the **** away from airlines that continued to operate the 737-MAX between the time they knew it had problems and the time the planes got grounded because of the problems they already knew it had.

To me, that speaks to an institutional laziness that almost certainly extends beyond their fleet of MAXs. If I can't trust Southwest to do the right thing with a 737-MAX, how can I trust them to be doing the right thing with a 737-800?

On the other hand, if you were to find an airline that had MAXs in service, and voluntarily grounded them when they understood the problem, I'd be happy to give them my business.

Meanwhile, there's airlines like Alaska, that don't have any MAXs in their fleet anyway, and haven't yet gotten a track record of bad behavior with their other planes. So they can keep my business for the time being. The 737-700/800/900 family is reportedly a more reliable and proven plane, so I'm not yet ready to give up on Boeing entirely. Plus it would be almost impossible to fly anywhere in the western hemisphere if I did that.

Which might not be a bad idea.

Hopefully, they have improved their maintenance standards since AA261

https://www.ntsb.gov/news/press-rele...light_261.aspx
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Old 14th March 2019, 04:13 PM   #82
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Originally Posted by smartcooky View Post
Hopefully, they have improved their maintenance standards since AA261



https://www.ntsb.gov/news/press-rele...light_261.aspx
A ten year moratorium seems entirely reasonable.
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Old 14th March 2019, 07:29 PM   #83
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Originally Posted by smartcooky View Post
I think its both.

I might be pre-empting things here, but assuming it is MCAS that caused the difficulty the pilots had with controlling the aircraft I'm going to go right ahead and call early what I think the conclusion of the investigation will be.

CAUSE
- Pilot error

CONTRIBUTING FACTORS
- Insufficient training by the airline and by Boeing.
- Poor documentation by Boeing
- Delays in certification by the FAA due to the US Government shutdown in 2019
If MCAS caused it, how could it be pilot error?

Also, how would the pilot know that MCAS was causing the issue and that the thing to do would be to turn it off?
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Old 16th March 2019, 09:25 AM   #84
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Originally Posted by Puppycow View Post
If MCAS caused it, how could it be pilot error?

Also, how would the pilot know that MCAS was causing the issue and that the thing to do would be to turn it off?

Brazil demanded new training protocols for the new plane. But not the U.S.
Quote:
n October 2017, Brazilian regulators flew to Miami to test out the brand-new Boeing 737 Max 8. The team scrutinized the sleek new jetliner’s flight systems and soon published a list of over 60 operational changes, from landing systems to cockpit displays, that Brazilian pilots would need to learn.

Among the new features regulators said pilots would have to familiarize themselves with was the Maneuvering Characteristics Augmentation System, a safety system that could nose the plane downward if it sensed a potential stall. The regulators mandated an interactive course for pilots to go over the changes and recommended “two legs of SLF,” or supervised flight, according to a copy of their report obtained by The Washington Post.

In those same months, the Federal Aviation Administration was making its final revision to a 53-page report that would make up the backbone of Max 8 training guidelines for pilots across the United States and in almost every other country around the world.
https://www.washingtonpost.com/inves...=.06963c8e2476
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Old 16th March 2019, 01:24 PM   #85
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Originally Posted by Puppycow View Post
If MCAS caused it, how could it be pilot error?

Also, how would the pilot know that MCAS was causing the issue and that the thing to do would be to turn it off?
Understand that Pilot error is not always directly blaming the pilot for the crash.

If an aircraft system fails, but that failure is resolvable, and the pilot fails to resolve it and the aircraft crashed, that is pilot error.

If the pilot was unable to resolve the failure because of poor or inadequate training, that is a mitigating factor.

A good example is Air France 447.
• temporary inconsistency between the measured speeds, likely as a result of the obstruction of the pitot tubes by ice crystals, causing autopilot disconnection and reconfiguration to alternate law;
• the crew made inappropriate control inputs that destabilized the flight path;
• the crew failed to follow appropriate procedure for loss of displayed airspeed information;
• the crew were late in identifying and correcting the deviation from the flight path;
• the crew lacked understanding of the approach to stall;
• the crew failed to recognize the aircraft had stalled and consequently did not make inputs that would have made it possible to recover from the stall
The initial failure was airspeed indication due to iced pitot tube. This was a mechanical system failure, but the pilots were unable to resolve it...

The cause was ultimately ruled to be pilot error.
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Old 16th March 2019, 03:02 PM   #86
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Originally Posted by ponderingturtle View Post
This is just a claim to try to justify the existence of the FAA and its excessive regulations and intrusions on business. They are clearly all useless and worthless and properly should be fired like all government regulators. That is the conservative answer to this.
Yes, absolutely right. The market decided in this case, as it always should. Keep planes flying until enough people die and no one wants to fly on the planes any more. Simple, yet effective.
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Old 16th March 2019, 03:35 PM   #87
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Originally Posted by smartcooky View Post
Understand that Pilot error is not always directly blaming the pilot for the crash.

If an aircraft system fails, but that failure is resolvable, and the pilot fails to resolve it and the aircraft crashed, that is pilot error.

If the pilot was unable to resolve the failure because of poor or inadequate training, that is a mitigating factor.

A good example is Air France 447.
• temporary inconsistency between the measured speeds, likely as a result of the obstruction of the pitot tubes by ice crystals, causing autopilot disconnection and reconfiguration to alternate law;
• the crew made inappropriate control inputs that destabilized the flight path;
• the crew failed to follow appropriate procedure for loss of displayed airspeed information;
• the crew were late in identifying and correcting the deviation from the flight path;
• the crew lacked understanding of the approach to stall;
• the crew failed to recognize the aircraft had stalled and consequently did not make inputs that would have made it possible to recover from the stall
The initial failure was airspeed indication due to iced pitot tube. This was a mechanical system failure, but the pilots were unable to resolve it...

The cause was ultimately ruled to be pilot error.
OK, I won't argue over it, but since it's (apparently) happened twice already since these planes have been introduced, something might be seriously wrong with the software or some other component of the system. Also, it may not be apparent to the pilots which system has failed. Especially if there is no mention in the manual they use or established procedure to follow. They had in each case thousands of hours of experience, but perhaps something like this had never happened to them before. Suddenly the plane is out of control and not responding to stick inputs.
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Old 16th March 2019, 05:24 PM   #88
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Originally Posted by Puppycow View Post
OK, I won't argue over it, but since it's (apparently) happened twice already since these planes have been introduced, something might be seriously wrong with the software or some other component of the system. Also, it may not be apparent to the pilots which system has failed. Especially if there is no mention in the manual they use or established procedure to follow. They had in each case thousands of hours of experience, but perhaps something like this had never happened to them before. Suddenly the plane is out of control and not responding to stick inputs.
Oh, I agree.

The point I'm making is that, if it was a faulty MCAS (which is starting to look more and more likely*) then the problem could have been overcome by disabling it (there is no way to actually turn the MCAS off).

There are two possible ways to do that (well three actually, but I won't go into the third as it gets complicated)

1. Lower the flaps to Flaps 1. MCAS is supposed to only be enabled with the flaps in the fully retracted position.

2. Turn the Stab Trim switches to OFF. This disables the horizontal stabilizer's automatic trim completely, and reverts to manual trim so that even if the MCAS is still erroneously detecting a stall, it cannot send trim inputs to the FCS.



*Update

https://www.washingtonpost.com/world...=.56baceff2f62
Investigators found a device known as a jackscrew in the wreckage. The jackscrew, used to set the trim that raises and lowers the plane’s nose, indicates the jet was configured to dive, according to John Cox, a former pilot and an airline-safety consultant with the Washington-based aviation-safety consulting firm Safety Operating Systems.
Also, CNN are reporting that the pilot reported control system problems almost immediately after takeoff... about the time when the flaps are retracted. Also, that ATC tracked the aircraft pitching up and down wildly, and accelerating and decelerating.

This is definitely looking like a flight control system problem.
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Old 16th March 2019, 07:10 PM   #89
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Originally Posted by smartcooky View Post
Oh, I agree.

The point I'm making is that, if it was a faulty MCAS (which is starting to look more and more likely*) then the problem could have been overcome by disabling it (there is no way to actually turn the MCAS off).

There are two possible ways to do that (well three actually, but I won't go into the third as it gets complicated)

1. Lower the flaps to Flaps 1. MCAS is supposed to only be enabled with the flaps in the fully retracted position.

2. Turn the Stab Trim switches to OFF. This disables the horizontal stabilizer's automatic trim completely, and reverts to manual trim so that even if the MCAS is still erroneously detecting a stall, it cannot send trim inputs to the FCS.

https://www.dropbox.com/s/yntgr47fa9...able.jpg?raw=1

*Update

https://www.washingtonpost.com/world...=.56baceff2f62
Investigators found a device known as a jackscrew in the wreckage. The jackscrew, used to set the trim that raises and lowers the plane’s nose, indicates the jet was configured to dive, according to John Cox, a former pilot and an airline-safety consultant with the Washington-based aviation-safety consulting firm Safety Operating Systems.
Also, CNN are reporting that the pilot reported control system problems almost immediately after takeoff... about the time when the flaps are retracted. Also, that ATC tracked the aircraft pitching up and down wildly, and accelerating and decelerating.

This is definitely looking like a flight control system problem.
Sounds like a phugoid motion, the flight crew was certainly having a bad day.
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Old 17th March 2019, 12:54 AM   #90
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Originally Posted by Delphic Oracle View Post
Sounds like a phugoid motion, the flight crew was certainly having a bad day.
Indeed! The VS plots of the Ethiopian Airlines and Lion Air flights bear a disturbing similarity



The 15-20 second interval of climb and dive points directly to MCAS being a chief suspect.

A typical climb out rate after takeoff is 1800 fpm... note that the EA flight almost hit 3000 fpm; an airliner like the 737 would not be able to maintain that for long without putting the nose down or a stall would result.

Those last few minutes would have been utterly terrifying for the passengers.
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Old 17th March 2019, 06:34 AM   #91
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Originally Posted by Puppycow View Post
OK, I won't argue over it, but since it's (apparently) happened twice already since these planes have been introduced, something might be seriously wrong with the software or some other component of the system.
.....

From this, it sounds like the 50+ year-old design has been modified and revised beyond its capacity.
Quote:
First introduced in West Germany as a short-hop commuter jet in the early Cold War, the Boeing 737-100 had folding metal stairs attached to the fuselage that passengers climbed to board before airports had jetways. Ground crews hand-lifted heavy luggage into the cargo holds in those days, long before motorized belt loaders were widely available.

That low-to-the-ground design was a plus in 1968, but it has proved to be a constraint that engineers modernizing the 737 have had to work around ever since. The compromises required to push forward a more fuel-efficient version of the plane — with larger engines and altered aerodynamics — led to the complex flight control software system that is now under investigation in two fatal crashes over the last five months.
https://www.latimes.com/local/califo...315-story.html
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Old 18th March 2019, 05:55 AM   #92
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Originally Posted by smartcooky View Post
Hopefully, they have improved their maintenance standards since AA261

https://www.ntsb.gov/news/press-rele...light_261.aspx
But fortunately all that kind of garbage regulation went out the window with the regulators during the shutdown.
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Old 18th March 2019, 12:57 PM   #93
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For reference these are some other major airframe groundings, the cause, and how long they lasted.

Boeing 787 Dreamliners, grounded worldwide for 3 months in 2013 after two separate cases of battery fires (one caused an emergency diversion and landing, the other happened on an unoccupied plane on the runway. No crashes or fatalities.)

McDonnell Dougles DC-10, grounded for 37 days in 1979 after 273 people were killed in a crash in Chicago caused by an engine separating from the wing in flight.

Lockheed L-049 Constellation, grounded for 6 weeks in 1946 after one crash that killed 4 and several reports of engine fires.
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Old 18th March 2019, 02:31 PM   #94
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Originally Posted by JoeMorgue View Post
McDonnell Dougles DC-10, grounded for 37 days in 1979 after 273 people were killed in a crash in Chicago caused by an engine separating from the wing in flight on takeoff.
Turned out be a maintenance issue leading to component failure.

Originally Posted by JoeMorgue View Post
Lockheed L-049 Constellation, grounded for 6 weeks in 1946 after one crash that killed 4 and several reports of engine fires.
Electrical fire in the wings

Of course there is also the famous grounding of the DH Comet 1, grounded twice; once in January 1954, and again in April 1954, less than a month after flights resumed

Cause was a design flaw combined with metal fatigue.
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Old 18th March 2019, 02:57 PM   #95
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Originally Posted by smartcooky View Post
Of course there is also the famous grounding of the DH Comet 1, grounded twice; once in January 1954, and again in April 1954, less than a month after flights resumed

Cause was a design flaw combined with metal fatigue.
Was that the square window problem?
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Old 18th March 2019, 03:03 PM   #96
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Originally Posted by JoeMorgue View Post
Was that the square window problem?
Square windows fit in square holes in the skin of the plane. The corners of the square holes concentrated skin stress at those points, causing the skin to fail. As you can imagine, this is suboptimal for airplanes. Especially at times of high and prolonged stress, such as flying through the air.

Most planes have windows with rounded corners, distributing the stress more evenly across the skin around the window, and avoiding having your plane come unskinned at 30,000 feet with a hundred lives on board.
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Old 18th March 2019, 03:07 PM   #97
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Originally Posted by smartcooky View Post
If they were trained, retrained or briefed about it, but it seems they may not have been. Plenty of Max 8 pilots are claiming they have heard little or nothing from Boeing.

https://www.washingtonpost.com/busin...a61_story.html

Nothing on the MCAS

After the Ethiopian Airlines crash Sunday, Boeing said it would update flight-control software, provide more training, introduce “enhancements” to external sensors that measure the direction of an aircraft and make changes to how MCAS is activated.

But two pilots who attended the meeting with Boeing in November after the Lion Air crash said pilots had suggested that the company take these actions at that time.

“Whatever level of training they decided on [before the Lion Air crash], it resulted in an iPad course that I took for less than an hour,” Tajer, the American Airlines pilot, said. “A lot of pilots here at American did that course.”

But he said the course did not cover the new MCAS system. “There was nothing on the MCAS because even American didn’t know about that. It was just about the display scenes and how the engines are a little different,” he said.

That's what I've heard in the coverage on the radio here; Boeing chose to present the 737 Max as a minor upgrade, not a new plane, to avoid the costs involved in certification and training that new plane would entail. I've not heard that there was any actual bug in what the plane was doing, just that it was unexpected from the pilot's point of view, so they didn't know how to react.
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Old 18th March 2019, 03:19 PM   #98
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Originally Posted by theprestige View Post
Square windows fit in square holes in the skin of the plane. The corners of the square holes concentrated skin stress at those points, causing the skin to fail. As you can imagine, this is suboptimal for airplanes. Especially at times of high and prolonged stress, such as flying through the air.

Most planes have windows with rounded corners, distributing the stress more evenly across the skin around the window, and avoiding having your plane come unskinned at 30,000 feet with a hundred lives on board.
WW2 'Liberty ships' had the same problem with hold hatch corners causing cracking of the main deck.
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Old 18th March 2019, 05:21 PM   #99
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Originally Posted by zooterkin View Post
That's what I've heard in the coverage on the radio here; Boeing chose to present the 737 Max as a minor upgrade, not a new plane, to avoid the costs involved in certification and training that new plane would entail. I've not heard that there was any actual bug in what the plane was doing, just that it was unexpected from the pilot's point of view, so they didn't know how to react.
And here is the really important point about this. If you start having problems such as your aircraft pitching nose down at cruise speed and altitude, you have margin; you have time to sort it out, because you have some altitude and airspeed to work with.

However, an aircraft just after take-off is still climbing and accelerating. Typically, a 737-800 take off speed is about 130 -160 kts (fuel and load dependant) and in climb-out, it is accelerating to its cruise speed of around 500 kts. Three minutes into flight its probably still only around 5,500 ft at 300 kts. Anything goes wrong, there is not a lot of margin for the pilot to work with.
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Old 18th March 2019, 06:24 PM   #100
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Originally Posted by smartcooky View Post
And here is the really important point about this. If you start having problems such as your aircraft pitching nose down at cruise speed and altitude, you have margin; you have time to sort it out, because you have some altitude and airspeed to work with.

However, an aircraft just after take-off is still climbing and accelerating. Typically, a 737-800 take off speed is about 130 -160 kts (fuel and load dependant) and in climb-out, it is accelerating to its cruise speed of around 500 kts. Three minutes into flight its probably still only around 5,500 ft at 300 kts. Anything goes wrong, there is not a lot of margin for the pilot to work with.
National Airlines 102, for instance. Poor guy just never had time to sort it out. Amazingly, after nearly rolling over and with questionable flight controls he was just about wings level and slightly pitched down when he ran out of time.

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National Airlines Flight 102

Quote:
On 2 June 2013, investigators from the Ministry of Transport and Civil Aviation of Afghanistan confirmed the load shift hypothesis as the starting point: three armoured vehicles and two mine-sweeping vehicles, totalling 80 tons of weight, had not been properly secured. At least one armoured vehicle had come loose and rolled backwards against the airplane's rear bulkhead, damaging the bulkhead. This also crippled key hydraulic systems and damaged the horizontal stabilizer components - most notably the jackscrew, which rendered the airplane uncontrollable.[3] Control of the aircraft was therefore lost, with the abnormal pitch-up rotation, stall, and crash to the ground ensuing.[1] The damage made it impossible for the crew to regain control of the aircraft.

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Old 18th March 2019, 07:58 PM   #101
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Originally Posted by JoeMorgue View Post
Of American based airlines:

Alaska Air has 32 on order, but is not currently flying any.
American Airlines has 100 on order, has 22 in its fleet.
Ryan Air has 135 on order, but is not currently flying any.
Southwest has 280 on order, has 31 in its fleet.
United has 136 on order, has 14 in its fleet.
2 have been delivered to individuals/companies for use as personal or corporate jets. I assume they would be affected by the grounding.

I cannot find any carrier world wide that is flying only the 737 Max (some small budget carriers only fly one make/model of plane to keep costs down.)
Ryan Air is an Irish airline.
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Old 19th March 2019, 05:39 AM   #102
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I came across this speculation by a friend and fellow pilot, that I found well-informed and I thought I’d share.

***Warning contains my own uninformed speculation... I am posting it ONLY to see if people agree or disagree... ***

It seems clear to me that a chain of well known information could give us a possible explanation and the reasons for the recent 737 max 8 crashes.

Overall its the problem of adding envelope protection and automation to an older Boeing aircraft design that, unlike Airbus, was never designed for fly by wire automation, and an addition that is against the normal design philosophy of the manufacturer - - - Boeing.

Airbus has had fly by wire and computer based flight controls designed in from the begining, Boeing however have never before really embraced this idea.

While the lunar module and many agile fighter jets would be unstable without fly by wire, Boeing have normally designed aircraft that fly 'naturally'..

This can be seen clearly in the design of the pilot interface to the aircraft, a big old fashioned yoke in the Boeing and a small side stick like a games controller in the Airbus and the Apollo era lunar module.... .

But here's the problem, when Boeing added bigger engines and other changes like fuselage length to the 737-max series they upset the natural flight characteristics, engines needed to be more forward in a different position, and had more thrust. I heard Boeing found this affected control, badly, at some edges of the flight envelope including the full power stall characteristics of the aircraft.

Pilots who practice full power stalls know they are scary at the best of times. This aircraft was apparantly even more scary, so much so that it could probably not have been certified.

So automation shy Boeing were forced to depend on Airbus style software protection to prevent these edges of the flight envelope ever being reached.

Hense the MCAS system was born, an override that would automatically forward trim the aircraft at high angles of attack approaching the stall in this configuration, flaps up full power, ( you know like the climb phase close to the ground just after take off) to eliminate the possibility of the stall...

Trouble is, the airframe was designed years ago. The trim on the 737 trims the angle of the WHOLE tail stabiliser.... not just the elevators. Yes that 'wing at the back' actually changes its position relative to the fusalage... its whole angle.... this is actually a very powerful, coarse control input in the wrong hands.... .. the pilot controlled elevator for pitch control at the back is only part of this whole flying surface... so I imagine that trim can, at full defection, be a stronger force than elevator input.

So a faulty angle of attack sensor could trigger this forward stabiliser trim if it detects a phantom stall... . Boeing say this is what happened in the first lion Air crash... a faulty sensor.. but they blamed pilot training... really?

So what actually happens? Well every 10 seconds or so, unless the whole trim system is disabled, the MCAS forces the nose down using this very powerful stabiliser trim, to avoid the phantom stall.

You can imagine a pilot fighting this in two ways, pulling back on that big yoke, and trimming backwards to reverse the false input, but every time he does the system kicks in again and undoes his fixes... there are two additional problems the poor pilot faces... .

Firstly because the aircraft thinks its stalling it starts shaking this yoke. imagine pulling to save your life on a yoke that is shaking, it's like the aircraft is disobeying wanting to nose down and still want you to fight it. But hang on... secondarily the Yoke has an artifical feedback system designed to give flying the plane a more natural 'feel' for pilots. This system can make the controls feel stiffer at high speed for example and looser at low speed, even though, like the steering wheel of a car the controls are power assisted.... in a stall guess what? this artificial feedback system kicks in to make it very hard to pull back on the yoke... its stiffens as if to say 'don't do that'...

So we have runaway trim, moving the whole rear stabiliser into a dangerous nose down flight position... possibly faster that the pilot can fix it, a shaking stick, and a yoke that actively resists pilot input to pull back! Even if the pilots disconnected the trim system (as per Boeing 'fix'...) its likely to be left in a nose heavy trim position... which takes time to fix...

Then the poor pilot has to try and pull up, using a small (relatively speaking) elevator, against a stiff, artificially resistant pressure on the yoke, possibly with a shaking stick.... all close to the ground?

I can imagine easily how a runaway nose down trim, resistant and shaking controls and nose down path of the aircraft could quick result in loss of control, and ground impact, whatever the pilot did. Too little time to fight the disobedient aircraft..

To avoid it I guess they would need to very quickly identify what is happening (how can they when the problem has never been practiced?) disconnect the auto trim, manually fix the trim position quick enough to regain elevator authority, all while the stick is shaking and refusing or resisting to be pulled back?

I think this must qualify as a design flaw, that results on trying to add automation and envelope protection onto an aircraft concept and pilot interface where so many other design decisions have assumed automation is not present.

Thank goodness they have grounded the aircraft. Finally. But what can Boeing do to fix it? I suggest replacing MCAS with a good old fashioned Stall Warning horn, and let the pilots fly.. put a placard on the console saying 'Full power stalls prohibited'.. what else can they do?

Discuss?


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Old 19th March 2019, 04:00 PM   #103
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https://www.nytimes.com/2019/03/19/p...pia-crash.html

Short version is that this plane was made to compete with a similar sized Airbus plane, which is more fuel-efficient than earlier models of the 737. The selling point was that pilots who already know how to fly the 737 won't need any retraining or flight simulator time. They even decided that pilots didn't need to know about the new MCAS system, so when they ran into problems, the pilots didn't even know that the system existed or that it was what was causing the problem.
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Old 19th March 2019, 06:45 PM   #104
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Pilot Who Hitched a Ride Saved Lion Air 737 Day Before Deadly Crash
"As the Lion Air crew fought to control their diving Boeing Co. 737 Max 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit.

That extra pilot, who was seated in the cockpit jumpseat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia’s investigation.

The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard."
Doesn't look good for Lion Air.
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Old 19th March 2019, 07:57 PM   #105
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Doesn't look good for Boeing either. An extra pilot who didn't have his hands full during a busy part of the flight just after takeoff was able to sit back and diagnose the root cause of the problem and the solution.
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Old 19th March 2019, 08:12 PM   #106
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Originally Posted by Fast Eddie B View Post
I came across this speculation by a friend and fellow pilot, that I found well-informed and I thought I’d share.

***Warning contains my own uninformed speculation... I am posting it ONLY to see if people agree or disagree... ***




So automation shy Boeing were forced to depend on Airbus style software protection to prevent these edges of the flight envelope ever being reached.

Hense the MCAS system was born, an override that would automatically forward trim the aircraft at high angles of attack approaching the stall in this configuration, flaps up full power, ( you know like the climb phase close to the ground just after take off) to eliminate the possibility of the stall...

Trouble is, the airframe was designed years ago. The trim on the 737 trims the angle of the WHOLE tail stabiliser.... not just the elevators. Yes that 'wing at the back' actually changes its position relative to the fusalage... its whole angle.... this is actually a very powerful, coarse control input in the wrong hands.... .. the pilot controlled elevator for pitch control at the back is only part of this whole flying surface... so I imagine that trim can, at full defection, be a stronger force than elevator input.

So a faulty angle of attack sensor could trigger this forward stabiliser trim if it detects a phantom stall... . Boeing say this is what happened in the first lion Air crash... a faulty sensor.. but they blamed pilot training... really?

So what actually happens? Well every 10 seconds or so, unless the whole trim system is disabled, the MCAS forces the nose down using this very powerful stabiliser trim, to avoid the phantom stall.

You can imagine a pilot fighting this in two ways, pulling back on that big yoke, and trimming backwards to reverse the false input, but every time he does the system kicks in again and undoes his fixes... there are two additional problems the poor pilot faces... .

Firstly because the aircraft thinks its stalling it starts shaking this yoke. imagine pulling to save your life on a yoke that is shaking, it's like the aircraft is disobeying wanting to nose down and still want you to fight it. But hang on... secondarily the Yoke has an artifical feedback system designed to give flying the plane a more natural 'feel' for pilots. This system can make the controls feel stiffer at high speed for example and looser at low speed, even though, like the steering wheel of a car the controls are power assisted.... in a stall guess what? this artificial feedback system kicks in to make it very hard to pull back on the yoke... its stiffens as if to say 'don't do that'...

So we have runaway trim, moving the whole rear stabiliser into a dangerous nose down flight position... possibly faster that the pilot can fix it, a shaking stick, and a yoke that actively resists pilot input to pull back! Even if the pilots disconnected the trim system (as per Boeing 'fix'...) its likely to be left in a nose heavy trim position... which takes time to fix...

Then the poor pilot has to try and pull up, using a small (relatively speaking) elevator, against a stiff, artificially resistant pressure on the yoke, possibly with a shaking stick.... all close to the ground?

I can imagine easily how a runaway nose down trim, resistant and shaking controls and nose down path of the aircraft could quick result in loss of control, and ground impact, whatever the pilot did. Too little time to fight the disobedient aircraft..

To avoid it I guess they would need to very quickly identify what is happening (how can they when the problem has never been practiced?) disconnect the auto trim, manually fix the trim position quick enough to regain elevator authority, all while the stick is shaking and refusing or resisting to be pulled back?

I think this must qualify as a design flaw, that results on trying to add automation and envelope protection onto an aircraft concept and pilot interface where so many other design decisions have assumed automation is not present.

Thank goodness they have grounded the aircraft. Finally. But what can Boeing do to fix it? I suggest replacing MCAS with a good old fashioned Stall Warning horn, and let the pilots fly.. put a placard on the console saying 'Full power stalls prohibited'.. what else can they do?

Discuss?


Attribution: http://about.me/ianvalentine
All airliners use that type of trim system by rotating the horizontal stabiliser up and down.

All modern Boeing airliners are fly by wire, even though they retain the yoke. The difference to Airbus fbw is that Boeing still gives the pilots more direct control of the plane, they can fly it into a stall of they really want. They yoke gives simulated force feedback while the sidestick doesn't.

MCAS does break with historic Boeing design philosophy in that it will help to prevent a stall by dropping the nose by moving the horizontal stabiliser. It does this so that the force on the control column will stay the same. Otherwise the effect of the engines at near full power at an unstable balance point makes the pilot feel a control column that is counterintuitively feeling lighter even though the plane is about to stall.

It's all a mess and there is no elegance of a design philosophy there, just an ugly hack. And not just an ugly hack, but one that has been done badly.
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Old 19th March 2019, 08:23 PM   #107
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Originally Posted by a_unique_person View Post
Doesn't look good for Boeing either. An extra pilot who didn't have his hands full during a busy part of the flight just after takeoff was able to sit back and diagnose the root cause of the problem and the solution.
I wonder if the pilots who saved that plane made any effort or had any mechanism to communicate their experience to the other Lion pilots: "Hey, we almost died! If the plane does this, flips these switches quick!"
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Old 19th March 2019, 09:30 PM   #108
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Originally Posted by Bob001 View Post
I wonder if the pilots who saved that plane made any effort or had any mechanism to communicate their experience to the other Lion pilots: "Hey, we almost died! If the plane does this, flips these switches quick!"
A valid question.
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Old 20th March 2019, 01:03 AM   #109
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Originally Posted by smartcooky View Post
Oh, I agree.

The point I'm making is that, if it was a faulty MCAS (which is starting to look more and more likely*) then the problem could have been overcome by disabling it (there is no way to actually turn the MCAS off).

There are two possible ways to do that (well three actually, but I won't go into the third as it gets complicated)

1. Lower the flaps to Flaps 1. MCAS is supposed to only be enabled with the flaps in the fully retracted position.

2. Turn the Stab Trim switches to OFF. This disables the horizontal stabilizer's automatic trim completely, and reverts to manual trim so that even if the MCAS is still erroneously detecting a stall, it cannot send trim inputs to the FCS.

https://www.dropbox.com/s/yntgr47fa9...able.jpg?raw=1

*Update

https://www.washingtonpost.com/world...=.56baceff2f62
Investigators found a device known as a jackscrew in the wreckage. The jackscrew, used to set the trim that raises and lowers the plane’s nose, indicates the jet was configured to dive, according to John Cox, a former pilot and an airline-safety consultant with the Washington-based aviation-safety consulting firm Safety Operating Systems.
Also, CNN are reporting that the pilot reported control system problems almost immediately after takeoff... about the time when the flaps are retracted. Also, that ATC tracked the aircraft pitching up and down wildly, and accelerating and decelerating.

This is definitely looking like a flight control system problem.
Sometimes switching off the auto-pilot is more complicated;
https://www.youtube.com/watch?v=UgkyrW2NiwM
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Old 20th March 2019, 01:14 AM   #110
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The FAA certification process is under review.
https://www.bbc.co.uk/news/business-47633085
The problem is that whilst the FAA has previously been 'trusted' to certify US aircraft their processes now seems to be under question. European aviation authorities will probably want more detailed supervision of the FAA certification process or will require re-certification. The 'self-certification' process where manufacturers carry out their own checks on behalf of the FAA is likely to be reviewed. This may get caught up in the current fashion for trade wars. The Canadians may see an opportunity to hit back at Boeing following Boeing's actions against Bombardier. Potentially all new US manufactured aircraft will have their safety credentials questioned.
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Old 20th March 2019, 04:08 AM   #111
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Originally Posted by Planigale View Post
The FAA certification process is under review.
https://www.bbc.co.uk/news/business-47633085
The problem is that whilst the FAA has previously been 'trusted' to certify US aircraft their processes now seems to be under question. European aviation authorities will probably want more detailed supervision of the FAA certification process or will require re-certification. The 'self-certification' process where manufacturers carry out their own checks on behalf of the FAA is likely to be reviewed. This may get caught up in the current fashion for trade wars. The Canadians may see an opportunity to hit back at Boeing following Boeing's actions against Bombardier. Potentially all new US manufactured aircraft will have their safety credentials questioned.
Please the administration will put a stop to all such intrusive regulations.
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Old 20th March 2019, 04:44 AM   #112
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Originally Posted by a_unique_person View Post
All airliners use that type of trim system by rotating the horizontal stabiliser up and down.

All modern Boeing airliners are fly by wire, even though they retain the yoke. The difference to Airbus fbw is that Boeing still gives the pilots more direct control of the plane, they can fly it into a stall of they really want. They yoke gives simulated force feedback while the sidestick doesn't.

MCAS does break with historic Boeing design philosophy in that it will help to prevent a stall by dropping the nose by moving the horizontal stabiliser. It does this so that the force on the control column will stay the same. Otherwise the effect of the engines at near full power at an unstable balance point makes the pilot feel a control column that is counterintuitively feeling lighter even though the plane is about to stall.

It's all a mess and there is no elegance of a design philosophy there, just an ugly hack. And not just an ugly hack, but one that has been done badly.
I pretty much go along with most of this and the excerpt you posted, except this bit.

"Even if the pilots disconnected the trim system (as per Boeing 'fix'...) its likely to be left in a nose heavy trim position... which takes time to fix... "

Not if I understand MCAS functionality correctly.

Switching off the stab trim does not disconnect the trim and leave the elevator in a fixed position, it turns off the autopilot inputs to the trim system. This means the trim system is returned to manual control, and the pilot is no longer fighting against the autopilot.
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Old 20th March 2019, 05:14 AM   #113
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Originally Posted by a_unique_person View Post

All modern Boeing airliners are fly by wire, even though they retain the yoke.
Are you sure? Over on SGU someone just put forth that the 737 Max series still uses cables, rods and hydraulics for flight controls.

Or were you excluding the 737 Max as not being “modern”? It’s kind of a hybrid, with very old roots but lots of modern tech tacked on.

This, from Quora: Every newly designed Boeing aircraft since the Boeing 777, which came out in 1995, has fly-by-wire controls. Legacy aircraft which still sell, like the long-in-the-tooth 737, the new version of the 747, and any 767 still being manufactured (for the military or civilian use), are still non-fly-by-wire.
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Old 20th March 2019, 06:15 AM   #114
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Originally Posted by Bob001 View Post
I wonder if the pilots who saved that plane made any effort or had any mechanism to communicate their experience to the other Lion pilots: "Hey, we almost died! If the plane does this, flips these switches quick!"
And how quickly considering most airlines try to keep their planes in the air for as much of the time as possible.
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Old 20th March 2019, 06:29 AM   #115
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Originally Posted by Fast Eddie B View Post
Are you sure? Over on SGU someone just put forth that the 737 Max series still uses cables, rods and hydraulics for flight controls.

Or were you excluding the 737 Max as not being “modern”? It’s kind of a hybrid, with very old roots but lots of modern tech tacked on.

This, from Quora: Every newly designed Boeing aircraft since the Boeing 777, which came out in 1995, has fly-by-wire controls. Legacy aircraft which still sell, like the long-in-the-tooth 737, the new version of the 747, and any 767 still being manufactured (for the military or civilian use), are still non-fly-by-wire.

The 737Max is not modern. The only FBW on it is the spoilers.
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Old 20th March 2019, 06:33 AM   #116
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Originally Posted by a_unique_person View Post
The 737Max is not modern. The only FBW on it is the spoilers.
Got it. The disconnect is, I think, that it’s “modern” in the sense it’s being manufactured now. With lots of modern bells and whistles. But it’s “legacy” in that it’s based on a very old design.
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Old 20th March 2019, 08:49 AM   #117
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Originally Posted by a_unique_person View Post
Doesn't look good for Boeing either. An extra pilot who didn't have his hands full during a busy part of the flight just after takeoff was able to sit back and diagnose the root cause of the problem and the solution.
Sure, it doesn't in any way absolve Boeing. But this is the first significant indicator that the airline did something wrong, in addition to Boeing.
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Old 20th March 2019, 02:17 PM   #118
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Hmm. I'm not 100% sure this means the airline did anything wrong as such. The incident when the off-duty pilot saved the day only happened the day before.

Those pilots would have no idea that is was a systemic problem. On landing at the destination airport, they would have reported it as a fault with the trim system or autopilot when they filled in the flight log, and then one of two things would happen.

Firstly, if there was a Lion Air maintenance facility at the destination airport, the ground crew would diagnose the fault to try to determine the cause. I am an aeronautical engineer by trade, specialising in avionics and I know how long these things take. Flight control systems are very, very complicated, with a lot of interacting connections and complex feedback loops. You could do several hours, even days of testing and still never find what caused the problem, because you cannot accurately replicate the in-flight problem on the ground. Sometimes it will take an actual test flight to do this.

Alternatively, if there was no Lion Air maintenance facility, the aircraft would be tagged with a defect, and flown back to its home airport with the Stab Trim switches off, and the fault would be investigated there.

The idea that the airline could do all this, and determine that the fault was not an isolated one due to a mechanical defect on this particular aircraft, but a systemic one attributable to a faulty design and could happen to any of their aircraft, and then put a warning out to, not only all their own pilots, but to everyone flying this aircraft type, in the space of only 24 hours, is just ludicrous.

ETA: AIUI, the off-duty pilot didn't already "know" what to do, but together, the three of them worked it out. Having the extra guy in the cockpit diagnosing the problem while the other two were battling the flight controls was probably the key factor in saving the aircraft.



Its also worth noting that the pilots in the Lion Air aircraft that crashed, were scrambling though the QRH and the flight manuals trying to understand why their aircraft was pitching down. They clearly did not know and Boeing failed to put that information in their manuals.

https://www.abc.net.au/news/2019-03-...ashed/10922820
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Old 20th March 2019, 03:40 PM   #119
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https://www.flightradar24.com/blog/a...f-the-737-max/

At 09:33, there's a good look back on how the MAX came about. Boeing was getting beat up badly in market share by Airbus. They wanted to do a new plane, but had to respond to the sales slump. American Airlines, for example, purchased 200 Boeing to 260 Airbus and that was only possible by promising to deliver an up-engine 737. Market pressures forced their hand.
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Old 20th March 2019, 04:35 PM   #120
theprestige
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Join Date: Aug 2007
Posts: 36,892
So far it seems like Boeing and their customers caused the crash, with the shutdown having nothing to do with it.

Raise your hand if you still like the thread title.
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