Boeing 737 MAX

[Seevee]

"Not so much a "gratuitous attack" as an observation that Airbus has had a few crashes due to pilots being unable to wrest control of the aircraft from a malfunctioning computer."

Not so,at the Paris air show crashes the Air Bust computer was doing just what it was programmed to do, no malfunction.

The problem was the computer overrode what the pilots wanted to do,, show off the aircraft to the crowds.

Built for marginal skilled seat warmers, the computer program would have been fine at normal flight operation, but skilled pilots showing off was not part of the installed program .

Programmed to crash?

 

[ssobol]

Programmed to crash?

No, but they were not operating the plane normally either.

https://en.wikipedia.org/wiki/Air_France_Flight_296

 

[BruceK]

"Not so much a "gratuitous attack" as an observation that Airbus has had a few crashes due to pilots being unable to wrest control of the aircraft from a malfunctioning computer."

Not so,at the Paris air show crashes the Air Bust computer was doing just what it was programmed to do, no malfunction.
....

So what? It`s not Airbus planes that are grounded, it`s Boeing Max737s. If posters here knew there were pilots certified to fly the plane who lacked the skills and experience to handle the emergency if/when the plane malfunctioned,ask yourself who else would know it too? Whoever may be responsible, it can`t have been Airbus.
You`d do better directing sympathy to those who died in the 2 crashes precipitating the ban, the airlines reliant on the Max737 for their operations, their staff, their stockholders, an inconvenienced travelling public,the affected tourism interests, etc etc.

 

[Delfin]

So what? It`s not Airbus planes that are grounded, it`s Boeing Max737s. If posters here knew there were pilots certified to fly the plane who lacked the skills and experience to handle the emergency if/when the plane malfunctioned,ask yourself who else would know it too? Whoever may be responsible, it can`t have been Airbus.
You`d do better directing sympathy to those who died in the 2 crashes precipitating the ban, the airlines reliant on the Max737 for their operations, their staff, their stockholders, an inconvenienced travelling public,the affected tourism interests, etc etc.

I see. So because others have attempted to explain to you why this issue may be a touch more complicated than your sliming of Boeing explains, those people lack sympathy for the victims of these crashes?

I'm afraid your dislike for all things American may be getting the better of you, Bruce.

 

[Boat]

Something else here doesn't pass the smell test.

For decades airliners have had various forms of "ground awareness", ground proximity. Inconceivable that trim could automatically be set to fly a plane into the ground with significant vertical velocity.

 

[FF]

"Programmed to crash?"

The consequences of a system that would not allow the deck angle to change quickly.

The French pilots dove to zip by the crowd , but the AP would not allow the nose to be brought up rapidly enough to miss the ground.

A safety feature!

 

[twistedtree]

So sad. In the last several posts, this outstanding thread is beginning to crash, as so many do. It went from being 95% civil, constructive, and informative, to spit balls and piss.


Come on guys, let's rise above it.

 

[RT Firefly]

Greetings,
Another angle.... https://www.forbes.com/sites/marisa...rogram-is-not-a-matter-of-money/#4e58ed3f220b


Technology seems to be happening too fast with not enough manpower to deal with it.

 

[twistedtree]

Richard, excellent post. It really captures how much this incident, like so many disasters, is the result of many small things conspiring to create a much bigger problem.


Regarding one of your comments, my understanding of the back and forth between MCAS and manual thumb switch trim is different from what you described. An example as I understand it would be MCAS trims down 2.5 deg, in this case because the AOA sensor is broken. Pilot in turn trims back to zero, and in doing so, MCAS gets locked out for 10 seconds. Then 10 seconds later, MCAS trims down 2.5 deg, pilot trims back to zero.


This continues as long as the pilot countermands the MCAS every 10 seconds, and I gather this explains the multitude of corrected trim evens in the Lion Air incident. So it's not a runaway trim down, unless the pilot is not countering the trim.


If the pilot doesn't manually counter the trim, then it would progress from 2.5 deg, to 5, to 7.5, etc until it is full trim down. So if the pilots tried the counter-trim for a while, concluded it wasn't solving the problem, then stopped doing it and went looking for other causes, the plane would crash into the ground with full trim down, right? Perhaps one of our 737 pilots can help our understanding here?

 

[ssobol]

"Programmed to crash?"

The consequences of a system that would not allow the deck angle to change quickly.

The French pilots dove to zip by the crowd , but the AP would not allow the nose to be brought up rapidly enough to miss the ground.

A safety feature!

They did not actually hit the ground, you can see the plane stable at a low altitude. They flew into trees at the end of the runway.

There is physics involved. The French pilots had actually slowed the plane down to close to its lowest limit. The computers prevented it from going slower. There was no excess energy in the system. In this state the only way to climb was to apply power. They applied power but too late. Amongst the contributing factors was that they were lower than originally intended and from above, the trees looked less tall than they actually were.

A Boeing aircraft in the same state would have experienced the same problem. The only difference would be that the pilots of the Boeing could have actually stalled the airplane if they tried to pull up before the trees.

The end result would've been the same.

 

[Delfin]

I don't find the use of private companies to assist in certification particularly troubling, nor something to try to solve by asking government workers to do the entire job. When a private company like Boeing screws up, it costs then billions. Bureaucrats are rarely held accountable for their failures, no matter how colossal. We went to war in Iraq because of non existent WMDs, and a trillion$ and many lives went down the drain. I don't recall anybody being held accountable for that.

 

[Ski in NC]

I have a slightly different take on this.

The problem was not lack of oversight by the FAA, but rather the problem was due to the FAA.

In trying to keep the Max "in type", the differences in operating envelope had to be somewhat hidden. If Boeing simply came out and said that the Max flew a little bit different, that would have opened up a whole mess of new regulations that would apply.

It is not that the Max is an unsafe aircraft, it is simply that it flies a bit different that its predecessors. Due to FAA rules, it was different enough that something needed to be done to fit the rules.

The problem was not the aircraft, but trying to fit it into the existing rules.

Law of unintended consequences shows up again.

 

[Boat]

I don't find the use of private companies to assist in certification particularly troubling, nor something to try to solve by asking government workers to do the entire job. When a private company like Boeing screws up, it costs then billions. Bureaucrats are rarely held accountable for their failures, no matter how colossal. We went to war in Iraq because of non existent WMDs, and a trillion$ and many lives went down the drain. I don't recall anybody being held accountable for that.

Me too. Factory trained pilots and crew with third party or government oversight on data collection would be the best of all worlds for certification testing.

Something else here doesn't pass the smell test.

For decades airliners have had various forms of "ground awareness", ground proximity. Inconceivable that trim could automatically be set to fly a plane into the ground with significant vertical velocity.

In other words, once the ground is unavoidable, recovery efforts are over, the plane should be trimmed for crash landing.

 

[BruceK]

They did not actually hit the ground, you can see the plane stable at a low altitude. They flew into trees at the end of the runway.

There is physics involved. The French pilots had actually slowed the plane down to close to its lowest limit. The computers prevented it from going slower. There was no excess energy in the system. In this state the only way to climb was to apply power. They applied power but too late. Amongst the contributing factors was that they were lower than originally intended and from above, the trees looked less tall than they actually were.

A Boeing aircraft in the same state would have experienced the same problem. The only difference would be that the pilots of the Boeing could have actually stalled the airplane if they tried to pull up before the trees.

The end result would've been the same.

Any crash is regrettable. It`s taking remedial action which impresses we travelling users of aircraft. Boeing deserves praise for embarking on remedial action right after its second Max 737 crash.

 

[AlaskaProf]

Here's a riddle, maybe one of you guys who've actually flown one of the 737 variants:

It's been reported that in the Ethiopian case the altitude excursions began as low as 450' AGL.

All reports say MCAS is inhibited when flaps are extended...you see where this is going? Is it realistic to have selected "Flaps 0" that early in the departure profile? Especially in what sounds like a pretty heavy airplane with a field elevation near 8,000' MSL.

Is it possible we are not looking at an MCAS event but a pilot induced stall? I can think of three ways to do that:
Premature retraction
No-flap departure (it's happened before, DTW, Dc9)
Improper departure trim.
...and given the discussion of the designed forward location of the MAC's engines, would it be expected to pitch up in a high-power, low-speed approach to the stall?

Additional puzzlement, admittedly rooted in my ignorance: descriptions of MCAS say Boeing installed the system to protect not against stalls, there are legacy systems for that eventuality, but against accelerated stalls, such as steep turns at lower speeds. If that is true, does the AoA sensor interact with something else, airspeed? G?

The reason I ask is that this airplane crashed on runway heading.

 

[ssobol]

Here's a riddle, maybe one of you guys who've actually flown one of the 737 variants:

It's been reported that in the Ethiopian case the altitude excursions began as low as 450' AGL.

All reports say MCAS is inhibited when flaps are extended...you see where this is going? Is it realistic to have selected "Flaps 0" that early in the departure profile? Especially in what sounds like a pretty heavy airplane with a field elevation near 8,000' MSL.

Is it possible we are not looking at an MCAS event but a pilot induced stall? I can think of three ways to do that:
Premature retraction
No-flap departure (it's happened before, DTW, Dc9)
Improper departure trim.
...and given the discussion of the designed forward location of the MAC's engines, would it be expected to pitch up in a high-power, low-speed approach to the stall?

Additional puzzlement, admittedly rooted in my ignorance: descriptions of MCAS say Boeing installed the system to protect not against stalls, there are legacy systems for that eventuality, but against accelerated stalls, such as steep turns at lower speeds. If that is true, does the AoA sensor interact with something else, airspeed? G?

The reason I ask is that this airplane crashed on runway heading.

Flaps are retracted as a function of speed, not altitude (although there is an indirect relationship in that lower altitude usually means lower speed. If you do a flaps 1 takeoff, you are only one flap retraction from flaps up.

As mentioned before, all underslung engines give a nose up pitching moment when power is applied. Just in the Max, it is more than the previous 737NG because the engines are more powerful. At lower speeds, the horizontal tail has less authority (because of slower airflow) to counter the nose up pitch effect when applying power to get out of a stall or near stall situation.

The MCAS system is supposed to make the MAX "feel" the same as the NG in this situation.

 

[FF]

"The only difference would be that the pilots of the Boeing could have actually stalled the airplane if they tried to pull up before the trees."


Perhaps,, but aircraft do fly on the backside of the power curve , ask any carrier pilot.

 

[Boat]

Something else doesn't pass the smell test. Have they discounted eyewitness reports?


This doesn't at all sound like a computer problem:


https://airlinerwatch.com/witnesses...-from-the-crashed-ethiopian-boeing-737-max-8/


"Witnesses report strange noise from the crashed Ethiopian Boeing 737 MAX 8"


"One of those witnesses was 47 years old Malka Galato, the farmer on whose field the plane crashed. He reported smoke and sparks from the plane."


"Witness Tamirat Abera (25) says that the pilot was still trying to pull up, but failed. Then there was fire and white smoke that turned black."

 

[ssobol]

Not many things you'd find on an airplane produce white smoke when burned. You could have something leaking or venting (e.g. fuel) that might look like white smoke. Also, it the air is humid, you might see condensation from the air moving over the wings in certain conditions.

With turbine engines if the airflow to the engines gets disrupted you can end up with compressor stalls which can cause the engines to make noises and emit smoke and flames. The airflow can be disrupted by rapid or excessive maneuvering (say like trying to avoid the ground).

 

[FlyWright]

Many planes have exotic tech fixes to aircraft performance peccadilloes. The Learjet has a system called Mach Trim that induces an UP stab trim input when hand flying near max mach to overcome "Mach Tuck". Long story short, as the aircraft accelerates without retrimming the stab, the aircraft will tend to pitch UP. As you approach max mach, the wing's center of pressure shifts aft and further increases in speed cause the nose to pitch DOWN...the reverse of what is normally experienced. This system counters that effect artificially by inputting UP stab trim to make the airplane "feel" like it's accelerating.

To the best of my knowledge, all aircraft I've flown had a primary AP/Trim Disconnect Switch located on the Control Yoke at the Pilot's left thumb and the Copilot's right thumb...each its primary control hand.

The importance of this switch's position and access in all flight regimes was paramount. If anything strange happened, push the button with your flying thumb and instantly stop ALL outside influences to the flight controls. It could be runaway trim, autopilot malfunction or mis-programming, Mach Trim failure...it only took ONE button push at your immediate fingertip to take full authority and control of the airplane.

Why doesn't Boeing do this with their MCAS system? IMO, they should have one Primary Disconnect on the yoke for ALL outside influences to the flight controls.

 

[ssobol]

Many planes have exotic tech fixes to aircraft performance peccadilloes. The Learjet has a system called Mach Trim that induces an UP stab trim input when hand flying near max mach to overcome "Mach Tuck". To the best of my knowledge, all aircraft I've flown had a primary AP/Trim Disconnect Switch located on the Control Yoke at the Pilot's left thumb and the Copilot's right thumb...each its primary control hand.

The importance of this switch's position and access in all flight regimes was paramount. If anything strange happened, push the button with your flying thumb and instantly stop ALL outside influences to the flight controls. It could be runaway trim, autopilot malfunction or mis-programming, Mach Trim failure...it only took ONE button push at your immediate fingertip to take full authority and control of the airplane.

Why doesn't Boeing do this with their MCAS system? IMO, they should have one Primary Disconnect on the yoke for ALL outside influences to the flight controls.

Pretty much any airplane that has a MMO near the speed of sound has a mach trim system. 737 included.

All transport category airplanes with an A/P system have a A/P disconnect switch on the control wheel or stick. This only disconnects the autopilot. Auto throttles and trim systems still work normally. There is a separate switch on the throttles to disconnect the auto throttles.

On large airplanes you don't want to disconnect the trim system every time the autopilot is disconnected.

On the 737 operating the wheel trim switch suspends the MCAS trim operation for several seconds. If the trim switch is released than the MCAS can trim again. Also, on the 737 if you move the control column more than a few degrees in the opposite direction of the trim movement the trim is supposed to stop moving.

However, this does not happen in the case of the MCAS because in the situation it is likely to operate in may have the pilot pulling back on the column. So the MCAS trim keeps working.

In the case of the Lion Air crash, they counter trimmed the MCAS trim about 26 times before they crashed. In theory, they could have kept this up for the entire flight. The ride might not be that pleasant, but it should have worked.

However, in the case of Lion Air it seems that one of the stick shakers was operating all the time (tied to the bad AOA sensor). Perhaps the crew kept letting the nose drop because they were trying to get out what they may have thought was a stall condition.

The CVR recording will be interesting.

 

[Seevee]

"The only difference would be that the pilots of the Boeing could have actually stalled the airplane if they tried to pull up before the trees."


Perhaps,, but aircraft do fly on the backside of the power curve , ask any carrier pilot.

They sure do, and in the Boeings, they could have applied power and pitch and flown over the trees in the stick shaker mode. And not stalled.

 

[ssobol]

They sure do, and in the Boeings, they could have applied power and pitch and flown over the trees in the stick shaker mode. And not stalled.

In the case of the A320 they were already at max pitch in level flight (and thus slowest possible speed or energy state) for the flight condition they were in. The A320 computers keep the pilots from increasing the pitch beyond the maximum. If they had been flying a Boeing product they would have been at or near the stick shaker speed. Increasing the pitch would put them in the stall range. The only way out of the situation was to increase engine power. The A320 pilots did so, but ran out of room before the engines spooled up enough to enable the plane to climb.

A Boeing plane might have been able to get a little more pitch out of the situation, if the pilots went into the stick shaker. Because the plane was in level flight at maximum pitch, there is no excess energy to climb until the engines spooled up. Simply increasing the pitch would have caused to plane slow down and increased the risk of a stall. It would be hard to say if the increase in pitch and resulting reduction in speed would have given enough climb to get away from the trees.

If the A320 pilots had thought about it, they could have put the plane into direct law. Then the A320 would have responded like a Boeing, with the same risks. Probably didn't occur to them to do that though. Probably wouldn't have helped much either.

You can only really operate on the backside of the power curve in planes that have a lot of excess power (e.g. military fighters). Transport category aircraft are not in the same class and are designed for a different purpose.

 

[Seevee]

In the case of the A320 they were already at max pitch in level flight (and thus slowest possible speed or energy state) for the flight condition they were in. The A320 computers keep the pilots from increasing the pitch beyond the maximum. If they had been flying a Boeing product they would have been at or near the stick shaker speed. Increasing the pitch would put them in the stall range. The only way out of the situation was to increase engine power. The A320 pilots did so, but ran out of room before the engines spooled up enough to enable the plane to climb.

A Boeing plane might have been able to get a little more pitch out of the situation, if the pilots went into the stick shaker. Because the plane was in level flight at maximum pitch, there is no excess energy to climb until the engines spooled up. Simply increasing the pitch would have caused to plane slow down and increased the risk of a stall. It would be hard to say if the increase in pitch and resulting reduction in speed would have given enough climb to get away from the trees.

If the A320 pilots had thought about it, they could have put the plane into direct law. Then the A320 would have responded like a Boeing, with the same risks. Probably didn't occur to them to do that though. Probably wouldn't have helped much either.

You can only really operate on the backside of the power curve in planes that have a lot of excess power (e.g. military fighters). Transport category aircraft are not in the same class and are designed for a different purpose.

Ssobol,

I don't understand the logic on the Airbus, but have an idea. If the direct law would have worked, too bad they didn't have the chance to try.

And while the Boeings are not designed to operate behind the power curve, they can fly there, can't think of many that won't. However, name me one plane that IS designed to do that other than a VTOL. If the stick shaker isn't operating, then there is excess energy and when you ad power, there's a LOT more energy, especially when operating way below gross, probably like the ill fated Airbus was.

I'd still bet that a Boeing would have survived that.

 

[Baker]

Damn I can't believe I missed this. I will have to read the entire thread and get back to y'all. Gonna be awhile I guess and I hope someone in here knows what they are taking about...lol

 

[Baker]

I have a slightly different take on this.

The problem was not lack of oversight by the FAA, but rather the problem was due to the FAA.

In trying to keep the Max "in type", the differences in operating envelope had to be somewhat hidden. If Boeing simply came out and said that the Max flew a little bit different, that would have opened up a whole mess of new regulations that would apply.

It is not that the Max is an unsafe aircraft, it is simply that it flies a bit different that its predecessors. Due to FAA rules, it was different enough that something needed to be done to fit the rules.

The problem was not the aircraft, but trying to fit it into the existing rules.

Law of unintended consequences shows up again.

That is a very profound obsevation and dead on the money!!! They could have left MCAS off of the airplane and just told pilots that the airplane had a weird tendency to pitch up in certain(defined) situations. Train the pilots for those situations and then they can FLY through them. Instead they buried them and nobody knew about it.

 

[Baker]

Man....I don't even know where to start. But I will try. I will also say that this will not be a complete answer to everything. I should have taken notes. I will also say that there are some really smart people on here that have brought up some really good points. I am not going to go over all of that as it has been hashed out in 11 pages.

I will start off by saying that MCAS is a "feel computer" as a few have stated toward the end of this thread. To give you an idea of what a feel computer is...we could talk about the steering wheel on your car. Chevy could have just given you a toggle switch which would have operated the wheels in either direction. But it would not have given you "feel". So they give you a steering wheel with a rack and a ratio that makes it easier to feel the direction change and the physical forces during that change. MCAS main purpose was to help it feel like an NG. It was mostly during turns or accelerated conditions where the engines produced lift in those situations. It is not normal for anyone to have to push the nose down during a turn. One normally has back pressure through a turn. So they introduced MCAS to push the nose over during these incidents to make it "feel" like past models.

Also, MCAS is not really a new system. It is a modification to an existing system called "speed trim". Speed trim is an automated trim system that does move the trim on the airplane without pilot input. Speed trim is indeed inhibited for 5 seconds after yoke mounted trim switch activation. NOWHERE have I read that MCAS is the same. Please provide a link that says MCAS is inhibited after trim switch activation? I am not saying it is not. But I was under the impression that MCAS is not inhibited at all. IOW, it will re engage instantly after the trim switches are released...further aggravating the situation.

With that said, and regardless of the above issue, I can talk about the human interaction with the machine. I fly this aircraft regularly and am VERY aware of the trim wheel movement. I hand fly to 18000 feet so I always see that trim wheel moving without my input(speed trim). Many times speed trim is trimming opposite of my desires...so I simply trim against it. If MCAS was commanding the trim movement, I don't even think I would know. I would do the same thing as I always do. NOW, like I said above...I am under the impression MCAS has no delay after trim switch activation...IOW, it will start trimming the instant you release the trim switches. If that were the case, I would know instantly that something was not right. For that matter, the captain of the Lion Air plane knew something was not right as he trimmed 21 times against it. My point being...if there were a 5 or 10 second delay after trim switch activation, these accidents would not have happened as they would have had enough time to (re)stabilize the airplane. As noted in one of the accident reports for Lion Air....the FO gave "2 flicks" of the trim switches. As we now know two flicks equals 5 degrees(2.5 degrees per activation)...5 degrees in rapid succession could mean full nose down.

Another thing that was brought up....a Flaps 0 take off would not have happened. We would have read about the smoking hole at the end of the runway. While they may have got airborne, it likely would have been a futile struggle for altitude resulting in defeat. FLAPS 1 takeoffs are not uncommon. Generally, the less flaps you have, the better your second segment climb will be(to clear obstacles at the end of the runway). But more flaps get you off the runway sooner. So Flaps 1 takeoff at a high density altitude airport with a long runway might be a good solution(with regard to tire speeds). Our company begins acceleration normally at 800 feet...that is the altitude the nose comes over and we accelerate to get the flaps up. Someone said this stuff started at 450 feet. I guess they could have retracted flaps at 450 feet but that would be a very non standard thing to do.

I am running out of steam...gotta got to bed. Ask away and I will try to answer...no guarantees...

 

[ssobol]

MCAS system description: 737 MAX - MCAS

The MCAS is sort of a "feel" system, but not exactly. There is already a feel system in the 737 which controls the forces on the control column using hydraulic pressure. Depending on which phase of flight you are in, the pressure is controlled by speed inputs to give the pilot the correct feel on the column to manually fly the plane. The MCAS system actually moves the stabilizer to change the performance of the airplane. This reduces the pilot force required to keep the nose down so it does affect the "feel", but not in the same way.

The control feel system does not move any aerodynamic surfaces to change the control feel. You can experience the column control feel system effects with the plane parked on the ground using a test set. MCAS will not affect the control feel if the plane is not moving.

I expect that there is more to the MCAS system moving the stab than just the pilot feel. If the only need for MCAS was for pilot feel, then Boeing could have accomplished the same thing with the elevator control feel system without actually moving the stabilizer.

 

[RT Firefly]

Greetings,
One more article: https://www.huffpost.com/entry/ethi...software-emergency_n_5ca49822e4b0ed0d780f0c3c


Take it for what it's worth...

 

[AlaskaProf]

Also FWIW:


A fellow I've networked with for a couple decades who flies the 737NG for a US carrier which has grounded its MAXs says that all of the US operators have reviewed the retained digital Quality Assurance data and reported no instance of MCAS anomaly.

There are several ASRS reports, all of which were investigated and found to be other than MCAS events.

Here's a report by a Seattle TV station. Not particularly enlightening until the last 20 seconds or so when the American Airlines union rep says the same thing.

https://youtu.be/oYolKJSrBmg

My friend also confirms something I was wondering about. The Ethiopian crew was confronted by a stick-shaker at lift-off. Their response was to retract the flaps.