If that were the only reason for MCAS, why does it have to rely on a single AOA sensor, rather than the combination of sensors that create the stall warning / stick shake? If it only has to be in effect in near stall conditions, then it should not need to be active unless near a stall.
QuoteActually, the MCAS was needed in part *because* of those powerful engines. They are more powerful and mounted farther forward than the engines on other 737s, so their power generates a higher turning moment that wants to push the nose up, so the danger of a stall is increased. Furthermore, once you the AOA very high, the nacelles themselves generate some lift (again, with a large moment because of the forward placement relative to the center of rotation), and that pushes for an even higher AOA. This is really only a problem once you are already at high AOA, but essentially the engines themselves become a destabilizing force once you get out of the safe zone.
I'm struggling with this description. It makes it seem like the new engine placement has a tendency to push the nose of the plane up, and that is the main reason for MCAS.
It's a Boeing design error and the S/W patch allowing "the option" of using two sensors stinks of cover-up. AOA DISAGREE alert indicator is also an "option"?!
Using two sensors is still shitty because you have now doubled the probability of MCAS failure due to a sensor failure.
Multiple sensors iced up for the AF447 disaster. Would MCAS register a discrepancy with two sensors reading similar yet both are out to lunch?
I'll repeat the old adage "with two clocks you can never know the correct time". This MCAS system is never going to be stellar, even adding a third (sensor) opinion because the other pair can malfunction. It's just getting a slightly lower probability of failure, this is all Boeing can accomplish. Unless there was a gross S/W bug that is being fixed too.
In other industries with safety-critical design, you do fault-tree analysis and FMEDA to ensure you have coverage of a sensor problem, among other scenarios.
Clearly, Boeing bungled this and is showing a repeat bungle with their hasty "software fix" that cannot meet basic functional safety requirements even after piling on the algorithm smartness.
I've seen this before - a bad design safety-critical system is out there, sold in numbers and a corporation has a massive panic to fix it ASAP without changing any hardware.
Adding complex S/W algorithms (which can never be proven correct) is very dangerous.
Then I read this:
"MCAS is implemented within the two Flight Control Computers (FCCs). The Left FCC uses the Left AOA sensor for MCAS and the Right FCC uses the Right AOA sensor for MCAS. Only one FCC operates at a time to provide MCAS commands. With electrical power to the FCCs maintained, the unit that provides MCAS changes between flights. In this manner, the AOA sensor that is used for MCAS changes with each flight."
How do you come up with something so stupid?
That the MCAS in default only use a single Angle of attack vane was a mistake by boeing. That stall warning is done with angle of attack sensors (and not "other" sensors) is because it is an aerodynamic phenomenon, not something to do with engines, a common misconception of non-pilots.
Furthermore, the reason MCAS was specifically designed for the MAX is that the *nacelles* themselves generate lift. (Almost any object in an airstream can generate lift if you hold it the right way.) They are designed to have neutral lift when in level flight, but as you turn the nose of the plane up, the engines actually want to push it up even more, and this is very pronounced at high angles of attack. I'm sure simulations showed that this instability is hard to recover from if not dealt with immediately, hence MCAS.
A stupid question here: why is MCAS needed in the first place? Isn't the pilot trained to push when the stick shaker is activated? There are some certain scenarios where the pilot must respond without referring the handbook, and they get well trained and well paid for executing those memory checklists well.
What's the problem trusting the pilot? Military planes don't have as much "safety" BS, and they don't fall from the sky for no reason.
I am curious why the plane was on full throttle. Do any pilots have a theory here? The plane was supposedly going 600mph and on full thrust. Maybe this is a normal pilot response.
And another question: if there is a huge structural error in this plane, why did "only" two planes crash in half a year time ?
Are there more incidents, reports from pilots that just in time got the plane under control by disabling the computer and take manual control? Haven't heard about them ?
And another question: if there is a huge structural error in this plane, why did "only" two planes crash in half a year time ?
Yes, there are reports of at least two other pilots that have had to deactivate MCAS during takeoff.
There are approximately 350 Boeing 737 Max 8 aircraft in operation worldwide, being flown by 54 operators, according to the US Federal Aviation Administration (FAA).5 days ago
it looks like it will be pretty hard to exactly determine the cause...
Yes, there are reports of at least two other pilots that have had to deactivate MCAS during takeoff.Ok 5 incidents in a half year for 350 planes flying at least two flights a day , so 5 incidents over 127000+ flights.
EDIT: the plane has been in service since 2016 so that would be miliions of flights and only now it occurs.
Don't get me wrong it is good to get to the bottom of this, but it looks like it will be pretty hard to exactly determine the cause if it only happens under certain very specific conditions.
Good that the flightrecorders are there, otherwise it would be a needle in a haystack.QuoteThere are approximately 350 Boeing 737 Max 8 aircraft in operation worldwide, being flown by 54 operators, according to the US Federal Aviation Administration (FAA).5 days ago
Thanks but I understand that, already. In this case, other sensor could have told the MCAS system that the plane was not stalled. The fact that the plane is going 600 mph in the direction the nose is pointed should be a pretty good indicator of this. I don't know what all sensors that the plane has, but it seems like there are some other ways to detect a stall than the AOA. And the fact the stick shaker did not activate means that the malfunctioning AOA did not fool the stick shaker, right?
3. After the elevator is manually moved by the pilot, the MCAS can re-trigger. Doing a full 2.5 degrees again. (In the Ethiopian Airlines flight, the captain corrected the plane 21 times, then he handed the plane to the FO.
3. After the elevator is manually moved by the pilot, the MCAS can re-trigger. Doing a full 2.5 degrees again. (In the Ethiopian Airlines flight, the captain corrected the plane 21 times, then he handed the plane to the FO.
Fuck me drunk. I'm sorry. What ?? 21 times??
"Here, the thing is fucked and we're all going to die. You deal with it".
Are the new engines so powerful that MCAS is needed or is it purely a bandaid because the weight of the new engines changed the CG too much
Wrong take on it. It was more likely something along the lines of, "My controls aren't working right, try yours!" Which is a perfectly reasonable thing to try. Redundancy on all the primary flight controls and instruments from side to side is deliberate, just in case one side breaks in some way.
It can take off like a Vulcan bomber:
QuoteIt can take off like a Vulcan bomber:Wowzers. The video says the plane experiences zero gravity when it leveled off. If you could get all the passengers to sign a waiver, I'd be the first one to.... watch the cell phone videos.
It can take off like a Vulcan bomber:
Standard airshow stuff for new planes. Light fuel load and a completely empty cabin. Even the passenger seats and cabin trim may be missing. Much bigger power to weight ratio than a normal commercial takeoff.
Standard airshow stuff for new planes. Light fuel load and a completely empty cabin. Even the passenger seats and cabin trim may be missing. Much bigger power to weight ratio than a normal commercial takeoff.A long time ago, I flew in a British Midland 747 from San Diego to LHR. The aircraft had flown from LHR to LAX, then the little hop down to San Diego to drop off the last few passengers. It took off with about 30 passengers on board, and hardly any fuel. Whoosh....