Simultaneous overspeed and stall warnings (making the pilots believe they were in a high speed stall).
To which the pilots responded to by giving the aircraft conflicting instructions and turning off the stall alarm. The incident was ruled to be pilot error over technical failure (which was the pitot tube issue that Airbus then fixed).
They did not turn off the stall alarm. It turned off itself when speed dropped below 60 kts. Then, the few times when the pilots started to take the correct action by pushing the nose down, speed increased above 60 kts again and the stall warning was reactivated. Which gave them the false impression that they were doing something wrong, and stopped pushing the stick.
I stand corrected, apparently there was no overspeed warning. But the speed indications were fluctuating wildly, and the altimeter was initially going down (due to icing), which prompted the flying pilot to pull the nose up. There were lots of conflicting indications, and at some point the flight director (which had initially disappeared) came back on with a pitch up command to climb at 6000 fpm! (Yes, one of the initial items on the unreliable airspeed checklist is to switch the flight directors off, but since they had already disappeared, they did not think of this step).
A good explanation from a pilot's point of view is here. It doesn't just explain what the pilots did wrong, but also what they were probably thinking at that point.
By the way, both pilots flew small airplanes in their free time. They did have the necessary basic flying skills, they just did not believe they were in a stall. They thought the stall warning was caused by incorrect speed indications, and the increased aerodynamic noise seemed to point towards excessive speed rather than a lack of speed.
As for the airshow crash, the whole point of the conspiracy theorists is that some parts of the report were faked to hide the fact that the engines did not spool up quickly enough. I'm not saying it's true, just explaining what the controvercy is about. Nobody is saying there was anything wrong with the elavators afaik. They were deliberately flying at max AOA to show off the airplane flying at extremely low speed.
It really was shut down, but they reenabled it because they needed to trim the nose back up.
The only way to stop the MCAS from trimming down, is by cutting power to the electric trim. But now they still couldn't get the nose back up because the plane had been trimmed down and they couldn't trim it back up without the electric trim. Manual trim is too slow and possibly even blocked because of the high aerodynamic forces on the jack screw caused by combined down trim and up elevator.
Since they couldn't get the nose back up and manual trim didn't work, they decided to reenable the electric trim to try and trim back up. But as soon as they did that, MCAS trimmed down even further.
As I already explained in a reply to another post higher up, two sensors is not fine if they are of the same type. Several airbus airplanes suffered a violent pitch down because both AOA probes iced up at the same time while going through a layer of icing conditions, resulting in a stall detection at higher altitude. One of these events is described here.
The correct action is to crosscheck AOA with other airplane data to make sure it's consistent. Which is a few lines of computer code since all the hardware already feeds into those computers. Airbus has implemented this fix, and Boeing will now do the same. Belatedly.
GP's post is very relevant. This is indeed something that is taught to every student pilot: never rely on any single instrument, always crosscheck. It's unforgiveable that they didn't program it this way, especially after the Airbus incidents.
Airbus used to rely on two AOA probes. Until they had several incidents where both probes iced up simultaneously at an AOA which was below stall AOA at low altitude but above the limit at high altitude. So when reaching that higher altitude, the plane pitched down violently and was temporarily uncontrollable until reaching a lower altitude again (unless you switched off two Air Data Computers to get into a more basic flight control law)
The correct fix (which Airbus implemented and Boeing is going to) is to rely not just on two AOA sensors, but also crosscheck the AOA with other flight data (airspeed, inertial reference, attitude)
It looks like they turned the trim back on because the MCAS had trimmed down so much that it was impossible to recover using only the elevators and manual trim. (And as someone else has posted, aerodynamic forces in that combined stabilizer/elevator configuration may even have made it completely impossible to trim manually)
Nope, they do look like weather vanes. Just do a Google Image search. (There are other types, but most look like weather vanes, including the ones on the 737 Max)
Airbus did have several incidents where the plane violently pitched down because both AOA probes had iced up (because they had gone through the same area of icing conditions at the same time). Not quite as bad as Boeing relying on a single sensor, but actually harder to recover from since the only solution was shutting down two Air Data Computers using push buttons on the overhead panel. Fortunately, in each incident, the pilots could regain control when the plane reached a lower altitude and the system no longer detected a stall.
Airbus took corrective action by first adding a memorized procedure for the pilots (telling them to turn off two Air Data Computers), then correcting the software so it crosschecked the AOA probe data with airspeed, inertial reference and attitude (which is the fix that Boeing is implementing now).
It's beyond belief how Boeing could not only fail to learn from Airbus' mistakes, but actually do worse by relying on only a single sensor for something so critical (and making a crosscheck between the two available AOA probes an option for an extra price?!?!)
Also, before the first crash, pilots didn't even know the MCAS existed. It wasn't in the flight manuals. Unbelievable.
The elevators were functioning correctly. They were at max angle of attack, any further up elevator would have stalled the plane. The problem was that the engines were not spooling up quickly enough.
Simultaneous overspeed and stall warnings (making the pilots believe they were in a high speed stall). Stall warning that shut up at low speed (below 60 kts) but came back on precisely when the pilots were temporarily taking the correct action, making them believe that pushing the stick was the wrong thing to do. Pilots that cannot feel what the other pilot is doing with the stick. With all the simultaneous warnings and inconsistent indications, they had no idea what information to trust anymore. Sure, with perfect hindsight it's easy to see what they did wrong, but it wasn't as clear cut as some seem to believe.
The Paris Air Show lawnmower, AF 296
Ah, I see, you are a conspiracy nut. The envelope protection saved almost all lifes back then when the pilot actively tried to kill everyone by stalling the aircraft. Without the protection the plane would have fallen from the sky like a bloody brick, not slowly gliding on the top of the trees.
They were actually trying to demonstrate the stall protection, by flying extremely slowly right at the edge of the stall (which no pilot would ever attempt in a regular plane). The big problem was that the engines did not spool up as quickly as the pilots had expected. The conspiracy theory is about why the engines took so long to spool up: some say they got into ground idle due to a programming error, some say it was because the pilots had pulled certain circuit breakers, some say flight data recorder info was falsified, etc... I have never really dug in to the whole story, but the theories are not as nutty as they would seem at first sight.
The pilots disengaged the electric trim which was causing the plane to pitch down. However, since it had already trimmed the nose down so much, they were unable to pull the nose back up using only the elevators (i.e. the stick). They could trim manually by turning the big trim wheels by hand, but that wasn't fast enough while they were continuing to dive towards the ground. So they decided to reengage the electric trim, hoping they could trim the nose back up. But instead, the MCAS immediately started to trim down even further.
You'd be surprised how some people have absolutely no problem with being caught lying in public or sexually harassing women, yet would be terrified to be caught during a perfectly legal sexual activity.
And what the summary forgot to mention (unless I missed it) was that the streaming site had more than 4,000 members, 97 of whom paid a $44.95 monthly fee to access extra features, such as the ability to replay certain live streams.
They were flying by hand. The problem is that the MCAS system is designed to add extra control inputs to the pilot's inputs to make the airplane behave the same as older 737s. And at high angles of attack (or when it thinks the angle of attack is high) it pushes the nose down to prevent a deep stall which would otherwise be a serious risk on this variant of the 737 due to the placement of its engines.
The part about single sensors being allowed if the chance of failure is less than 1 in 100000 is the biggest bullshit I've ever heard in my life as an airline pilot. If there are hundreds of parts that all have a 1 in 100000 chance of failure, that means failures will happen quite often, especially with thousands of planes flying around. And indeed failures do happen regularly, that's why airplanes normally have loads of redundancy. Airspeed, for example, is measured on most airplanes by three different pitot tubes that feed into three different air data computers that constantly compare their data. If one of them is different, it shuts down and throws a failure message.
That's just one example of many. Airliners have two fuel pumps per tank, several isolated hydraulics systems, several electrical systems with equipment spread over many buses with fault monitoring on all of them, etcetera.
If an engineer designs a plane so it overrides pilot inputs and pushes the nose down based on input from a single sensor, that engineer deserves to go to prison and be barred from practicing engineering for the rest of his life. In aviation, this kind of screw-up is simply unforgiveable.
Boeing is currently testing the common sense fix which crosschecks the angle of attack with other data (airspeed, inertial reference system, attitude,...), which is what they should have done from the beginning.
By the way, Airbus made a similar mistake not that many years ago, which was fixed with extra procedures and software updates. One would have expected Boeing to learn from Airbus' mistakes...
Force = mass x acceleration. If the force of gravity is negative, and mass is negative, acceleration is positive. So negative mass stuff would still fall down, right?
(I have read quite a few classical physics books, and a few about special and general relativity as well)
I'm having trouble with the concept of negative mass, too. The phonons would not just move away from the earth, but also from the sun, from the center of the galaxy, etc... Where do you stop?
I'm having trouble with the concept of positive mass, too. The phonons would not just move towards the earth, but also towards the sun, toward the center of the galaxy, etc... Where do you stop?
For positive mass this is no problem. The earth is attracted to the sun, and so is everything on earth, so the relative acceleration between objects on earth and the earth due to the gravity of the sun is zero (apart from small tidal forces). Same for the center of the galaxy which attracts the sun, the earth, and everything on earth. This is unnoticeable because the whole system gets the same acceleration towards the center of the galaxy. And the same goes for whatever acceleration we get from the acceleration of the universe. Whatever the cause of this acceleration (dark energy,...), it acts the same on all mass so it doesn't cause local relative accelerations.
For negative mass, though, all these forces do become important. If we are attracted by the sun, and something here on earth is repelled by the sun, it appears to get a double acceleration away from the sun relative to us. And for the expansion of the universe, which gives an acceleration proportional to distance, we don't even have a reference point so the calculation becomes nonsensical.
Also, take Einstein's famous elevator example to demonstrate the equivalence between gravity and acceleration. Take an elevator in outer space far away from any gravitational influence. The elevator contains a positive and a negative mass, both floating somewhere in the middle. Accelerate the elevator "upward" and both masses will appear to fall down. Now take the same elevator and place it on the surface of the earth. Now the positive mass falls down while the negative mass goes up. Ergo, contrary to one of the most basic assumptions of General Relativity, gravity is not equivalent to acceleration. So, GR goes out the window?
Helium balloons don't have negative mass, they still have weight and are attracted by the earth. It's the heavier surrounding air that pushes the balloon up (pressure gradient provides more force than gravity).
So you're saying that phonon traveling through some medium (like air) is pushed up by the rest of the medium? That's not really "negative mass", just "less mass than the surrounding medium".
Slashdot Mirror
More Volts on the road than Teslas?
In 2018, 18306 Volts were sold vs. 139782 Model 3s
In the first three months of 2019, 2520 Volts vs 22425 Model 3s
Even just the Model S or Model X outsell the Volt, in number of cars sold, while being a LOT more expensive.
https://insideevs.com/monthly-...
Simultaneous overspeed and stall warnings (making the pilots believe they were in a high speed stall).
To which the pilots responded to by giving the aircraft conflicting instructions and turning off the stall alarm. The incident was ruled to be pilot error over technical failure (which was the pitot tube issue that Airbus then fixed).
They did not turn off the stall alarm. It turned off itself when speed dropped below 60 kts. Then, the few times when the pilots started to take the correct action by pushing the nose down, speed increased above 60 kts again and the stall warning was reactivated. Which gave them the false impression that they were doing something wrong, and stopped pushing the stick.
I stand corrected, apparently there was no overspeed warning. But the speed indications were fluctuating wildly, and the altimeter was initially going down (due to icing), which prompted the flying pilot to pull the nose up. There were lots of conflicting indications, and at some point the flight director (which had initially disappeared) came back on with a pitch up command to climb at 6000 fpm! (Yes, one of the initial items on the unreliable airspeed checklist is to switch the flight directors off, but since they had already disappeared, they did not think of this step).
A good explanation from a pilot's point of view is here. It doesn't just explain what the pilots did wrong, but also what they were probably thinking at that point.
By the way, both pilots flew small airplanes in their free time. They did have the necessary basic flying skills, they just did not believe they were in a stall. They thought the stall warning was caused by incorrect speed indications, and the increased aerodynamic noise seemed to point towards excessive speed rather than a lack of speed.
As for the airshow crash, the whole point of the conspiracy theorists is that some parts of the report were faked to hide the fact that the engines did not spool up quickly enough. I'm not saying it's true, just explaining what the controvercy is about. Nobody is saying there was anything wrong with the elavators afaik. They were deliberately flying at max AOA to show off the airplane flying at extremely low speed.
It really was shut down, but they reenabled it because they needed to trim the nose back up.
The only way to stop the MCAS from trimming down, is by cutting power to the electric trim. But now they still couldn't get the nose back up because the plane had been trimmed down and they couldn't trim it back up without the electric trim. Manual trim is too slow and possibly even blocked because of the high aerodynamic forces on the jack screw caused by combined down trim and up elevator.
Since they couldn't get the nose back up and manual trim didn't work, they decided to reenable the electric trim to try and trim back up. But as soon as they did that, MCAS trimmed down even further.
As I already explained in a reply to another post higher up, two sensors is not fine if they are of the same type. Several airbus airplanes suffered a violent pitch down because both AOA probes iced up at the same time while going through a layer of icing conditions, resulting in a stall detection at higher altitude. One of these events is described here.
The correct action is to crosscheck AOA with other airplane data to make sure it's consistent. Which is a few lines of computer code since all the hardware already feeds into those computers. Airbus has implemented this fix, and Boeing will now do the same. Belatedly.
GP's post is very relevant. This is indeed something that is taught to every student pilot: never rely on any single instrument, always crosscheck. It's unforgiveable that they didn't program it this way, especially after the Airbus incidents.
No, it was AOA probes. You're thinking about AF 447 which was a pitot problem.
Here's a description of one of the events.
Airbus used to rely on two AOA probes. Until they had several incidents where both probes iced up simultaneously at an AOA which was below stall AOA at low altitude but above the limit at high altitude. So when reaching that higher altitude, the plane pitched down violently and was temporarily uncontrollable until reaching a lower altitude again (unless you switched off two Air Data Computers to get into a more basic flight control law)
The correct fix (which Airbus implemented and Boeing is going to) is to rely not just on two AOA sensors, but also crosscheck the AOA with other flight data (airspeed, inertial reference, attitude)
It looks like they turned the trim back on because the MCAS had trimmed down so much that it was impossible to recover using only the elevators and manual trim. (And as someone else has posted, aerodynamic forces in that combined stabilizer/elevator configuration may even have made it completely impossible to trim manually)
Nope, they do look like weather vanes. Just do a Google Image search. (There are other types, but most look like weather vanes, including the ones on the 737 Max)
Airbus did have several incidents where the plane violently pitched down because both AOA probes had iced up (because they had gone through the same area of icing conditions at the same time). Not quite as bad as Boeing relying on a single sensor, but actually harder to recover from since the only solution was shutting down two Air Data Computers using push buttons on the overhead panel. Fortunately, in each incident, the pilots could regain control when the plane reached a lower altitude and the system no longer detected a stall.
Airbus took corrective action by first adding a memorized procedure for the pilots (telling them to turn off two Air Data Computers), then correcting the software so it crosschecked the AOA probe data with airspeed, inertial reference and attitude (which is the fix that Boeing is implementing now).
It's beyond belief how Boeing could not only fail to learn from Airbus' mistakes, but actually do worse by relying on only a single sensor for something so critical (and making a crosscheck between the two available AOA probes an option for an extra price?!?!)
Also, before the first crash, pilots didn't even know the MCAS existed. It wasn't in the flight manuals. Unbelievable.
The elevators were functioning correctly. They were at max angle of attack, any further up elevator would have stalled the plane. The problem was that the engines were not spooling up quickly enough.
Pilot error, and a hair raising one at that
Simultaneous overspeed and stall warnings (making the pilots believe they were in a high speed stall). Stall warning that shut up at low speed (below 60 kts) but came back on precisely when the pilots were temporarily taking the correct action, making them believe that pushing the stick was the wrong thing to do. Pilots that cannot feel what the other pilot is doing with the stick. With all the simultaneous warnings and inconsistent indications, they had no idea what information to trust anymore. Sure, with perfect hindsight it's easy to see what they did wrong, but it wasn't as clear cut as some seem to believe.
Ah, I see, you are a conspiracy nut. The envelope protection saved almost all lifes back then when the pilot actively tried to kill everyone by stalling the aircraft. Without the protection the plane would have fallen from the sky like a bloody brick, not slowly gliding on the top of the trees.
They were actually trying to demonstrate the stall protection, by flying extremely slowly right at the edge of the stall (which no pilot would ever attempt in a regular plane). The big problem was that the engines did not spool up as quickly as the pilots had expected. The conspiracy theory is about why the engines took so long to spool up: some say they got into ground idle due to a programming error, some say it was because the pilots had pulled certain circuit breakers, some say flight data recorder info was falsified, etc... I have never really dug in to the whole story, but the theories are not as nutty as they would seem at first sight.
The pilots disengaged the electric trim which was causing the plane to pitch down. However, since it had already trimmed the nose down so much, they were unable to pull the nose back up using only the elevators (i.e. the stick). They could trim manually by turning the big trim wheels by hand, but that wasn't fast enough while they were continuing to dive towards the ground. So they decided to reengage the electric trim, hoping they could trim the nose back up. But instead, the MCAS immediately started to trim down even further.
Just don't place the stickers on both sides or they will still miss each other.
You'd be surprised how some people have absolutely no problem with being caught lying in public or sexually harassing women, yet would be terrified to be caught during a perfectly legal sexual activity.
And what the summary forgot to mention (unless I missed it) was that the streaming site had more than 4,000 members, 97 of whom paid a $44.95 monthly fee to access extra features, such as the ability to replay certain live streams.
The term "cost saving" seems kind of ironic now...
The 777 has had fly by wire flight controls for around 20 years.
The 737 Max still has mostly classic flight controls. Only the spoilers are fly by wire.
I thought LinkedIn was unbelievably negligent when they were not using salt. But Elsevier doesn't even hash?!?! What is this, 1980?
They were flying by hand. The problem is that the MCAS system is designed to add extra control inputs to the pilot's inputs to make the airplane behave the same as older 737s. And at high angles of attack (or when it thinks the angle of attack is high) it pushes the nose down to prevent a deep stall which would otherwise be a serious risk on this variant of the 737 due to the placement of its engines.
The part about single sensors being allowed if the chance of failure is less than 1 in 100000 is the biggest bullshit I've ever heard in my life as an airline pilot. If there are hundreds of parts that all have a 1 in 100000 chance of failure, that means failures will happen quite often, especially with thousands of planes flying around. And indeed failures do happen regularly, that's why airplanes normally have loads of redundancy. Airspeed, for example, is measured on most airplanes by three different pitot tubes that feed into three different air data computers that constantly compare their data. If one of them is different, it shuts down and throws a failure message.
That's just one example of many. Airliners have two fuel pumps per tank, several isolated hydraulics systems, several electrical systems with equipment spread over many buses with fault monitoring on all of them, etcetera.
If an engineer designs a plane so it overrides pilot inputs and pushes the nose down based on input from a single sensor, that engineer deserves to go to prison and be barred from practicing engineering for the rest of his life. In aviation, this kind of screw-up is simply unforgiveable.
Boeing is currently testing the common sense fix which crosschecks the angle of attack with other data (airspeed, inertial reference system, attitude,...), which is what they should have done from the beginning.
By the way, Airbus made a similar mistake not that many years ago, which was fixed with extra procedures and software updates. One would have expected Boeing to learn from Airbus' mistakes...
So basically they just move opposite to the pressure gradient of the gas. Makes sense, negative mass is BS to get headlines.
Force = mass x acceleration. If the force of gravity is negative, and mass is negative, acceleration is positive. So negative mass stuff would still fall down, right?
(I have read quite a few classical physics books, and a few about special and general relativity as well)
But if the gravitational force is repulsive and the acceleration is also opposite to the force, they would fall down rather than up, wouldn't they?
I'm having trouble with the concept of negative mass, too. The phonons would not just move away from the earth, but also from the sun, from the center of the galaxy, etc... Where do you stop?
I'm having trouble with the concept of positive mass, too. The phonons would not just move towards the earth, but also towards the sun, toward the center of the galaxy, etc... Where do you stop?
For positive mass this is no problem. The earth is attracted to the sun, and so is everything on earth, so the relative acceleration between objects on earth and the earth due to the gravity of the sun is zero (apart from small tidal forces). Same for the center of the galaxy which attracts the sun, the earth, and everything on earth. This is unnoticeable because the whole system gets the same acceleration towards the center of the galaxy. And the same goes for whatever acceleration we get from the acceleration of the universe. Whatever the cause of this acceleration (dark energy,...), it acts the same on all mass so it doesn't cause local relative accelerations.
For negative mass, though, all these forces do become important. If we are attracted by the sun, and something here on earth is repelled by the sun, it appears to get a double acceleration away from the sun relative to us. And for the expansion of the universe, which gives an acceleration proportional to distance, we don't even have a reference point so the calculation becomes nonsensical.
Also, take Einstein's famous elevator example to demonstrate the equivalence between gravity and acceleration. Take an elevator in outer space far away from any gravitational influence. The elevator contains a positive and a negative mass, both floating somewhere in the middle. Accelerate the elevator "upward" and both masses will appear to fall down. Now take the same elevator and place it on the surface of the earth. Now the positive mass falls down while the negative mass goes up. Ergo, contrary to one of the most basic assumptions of General Relativity, gravity is not equivalent to acceleration. So, GR goes out the window?
Helium balloons don't have negative mass, they still have weight and are attracted by the earth. It's the heavier surrounding air that pushes the balloon up (pressure gradient provides more force than gravity).
So you're saying that phonon traveling through some medium (like air) is pushed up by the rest of the medium? That's not really "negative mass", just "less mass than the surrounding medium".