Interesting news. I just finished this thread and found the same news unpaywalled on Microsoft News website.
Not sure if one has to login with a MS account or not.
Was the MCAS included in the 737max partly to prevent what happened with Air France 447 (an A330)?
If so, it seems the cure was worse than the disease. One whole plane-ful worse.
I should add that I understand the more direct reason for installing it is that the big engines, placed further forward so as to clear the ground, make an unwanted nose-up situation more likely. I just wondered if, without MCAS, this makes for even less margin of error should an Air France 447 situation arose (i.e., something that leads a pilot to lift the nose higher than she should).
I think where we are differing is that you are saying they should have been aware that disengaging the electric trim with the stab well out of position was a critical error. My view is that for most aircraft, and what the flight crew most likely believed was the case for the MAX, disengaging electric trim early is desirable but not critical—you should be able to trim manually regardless of how far out of trim it is. This is not the case for the B737 but it is not made clear in the MCAS / trim runaway procedure, using the electric trim to return the trim to a reasonable position is a footnote rather than a bold this-will-save-your-life headline.
I don’t think so. The Airbus, being fly-by-wire, is a completely different animal than the B737. For what it’s worth, the AF447 guys could have saved the day just by pushing the stick forward, instead one of them was holding it back almost all the way down. MCAS on the B737 is not meant to stop the pilots from holding the stick back, it’s supposed to make the control force get heavier when close to the stall because that’s a requirement to get the aircraft certified.
It wasn’t “eventually”. You can keep repeating the same thing again and again, but that doesn’t make it true.
It’s a pity that the graphs showing exactly what happened are too difficult for you to understand - as you admitted previously. If you can’t follow the details of what happened, that certainly explains why your argument comes down to, “Them darkie furriners can’t fly planes. They too stoopid. Not like us white, red-blooded true Americans.”
What happened was:
05:40:00 - MCAS cuts in for the first time for 9 seconds, overriding other input.
05:40:12 - 3 sec after MCAS ends, crew are correcting trim, probably not sure what just happened. Trim goes back up.
05:40:20 - MCAS cuts in a second time.
05:40:27 - Captain calls on First-Officer to trim up with him. Trim moves back up again.
05:40:35 - First-Officer calls “stab trim cut-out” twice. Captain agrees and they cut the electric stab trim.
At this point they have quickly and correctly identified the problem, and taken the correct action.
05:40:41 - MCAS activates again, but has no effect because they have cut the stab trim.
… but they are still not able to get back into trim manually.
They could NOT have continued correcting the trim and got fully back into trim before cutting the electric trim switches - because MCAS would have cut in again before they could do that.
There wasn’t enough time to get back into neutral trim between the MCAS activations. And each time it activated, the situation was getting worse.
if I remember correctly the joysticks on the airbus are first come first serve. The first one engaged cancels out the second. With a loss of airspeed data at that altitude the fix required a specific engine setting and trim setting. The window for this was very small and the Captain had stepped away from the cockpit.
The issue with the flight was a problem with the pitot tubes freezing quickly due to super cooled water which is water colder than zero C or -55F. here’s a video of what it looks like and how fast it freezes.. Airbus had accelerated their replacement program of the parts that failed. Ironically the plane was due for upgrade upon arrival of the flight.
If you understood what you are looking the time frame was NOT fast response. And they were able to trim both electrically and manually while the tail plane remained close to neutral. The situation got worse because the crew let it get worse. At some point the distraction of troubleshooting the computer input to the electric trim put them behind the recovery point.
They were at an extremely low altitude. Waiting 3 seconds would have the same effect as you waiting 3 seconds when your Tesla rental auto-steers into a barrier. You would be 2 3/4 seconds too late.
The time to fix trim at that altitude is immediately and you can’t let it go full trim. And what you fail to grasp is that trim is used to neutralize yoke input. Yoke input is used to change attitude. So at the very hint of downward nose trim the automatic response is to pull up and trim. In this case it stops the MCAS. If you don’t then the yoke becomes heavier as you pull back to maintain altitude so it’s impossible not to notice this.
After this cycle of back and forth trim repeats itself the obvious fix is to retrim for an upward climb and shut the electric trim off. That stops the cycle. This is what the previous crew did and it was a non-event from that point on. If it’s a pain in the ass to manually trim for landing then you extend out the approach.
Even taking your position, the end result is a yoke that is getting heavier and heavier on a flight that is extremely low to the ground. You have to know it’s going to take longer to manually trim.
If you were flying the worlds easiest manual trim its still going to take time to retrim from full down trim. what’s the decent rate of a plane traveling 250 knots with a nose down angle of 40 degrees?
I’m not a pilot, but I read the whole report on Air France Flight 447. As I recall, the Airbus fly-by-wire system either averages the input of the two pilots, or adds the two inputs. The controls are not linked together like with the Boeing control columns – in other words, there is no indication on one pilot’s controls of the other’s position.
Whether the Airbus computer averages or adds the inputs of the pilots’ joysticks, the effect is the same for for opposite commands: opposite commands will cancel each other out. Since the co-pilot on AF 447 was fully pulling back on his stick the entire way down (which even I as a non-pilot know is the exact wrong thing to do when you are in a stall), the pilot in the left seat was unable to counteract this and get the nose down.
I don’t believe the accident had anything directly to do with the airspeed or trim setting. A plane doesn’t need airspeed data to keep flying, and the plane was properly trimmed before the airspeed data was lost.
The problem was that after airspeed data was lost, the co-pilot fully pulled back on his joystick and put the plane into such a deep stall that the stall alarms cut out (because it was never envisioned that the plane could ever be stalled that badly). Early in the incident, when the nose was tentatively brought down, the stall alarm came on because the plane’s computer then recognized that the it was stalled. When the co-pilot pulled back on the stick, the alarm went off. So the alarm had the exact opposite effect of its intent, and thoroughly confused the co-pilot flying the plane…and he continued pulling back on the stick all the way down.
The other problem was poor training and lack of airmanship on the part of the co-pilot. The co-pilot was used to flying in so-called “Normal Law” in which the plane’s computer prevented the plane from stalling, even if a pilot pulled all the way back on their joystick. So the co-pilot was used to the computer keeping him out of trouble. The problem is that when the pitot tubes froze up and airspeed indication was lost, the computer shifted into “Alternate Law” in which the computer no longer prevented a pilot from being able to stall the plane.
By the time the left-seat pilot and the Captain (who had returned to the cockpit) realized what was going on, it was too late to recover. One of the last statements recorded in the cockpit was the co-pilot stating that he had been pulling back on his joystick the whole time.
That’s not what I said though. The assumption is that if you can hold the force required on the column (ie to maintain level flight), you should be able to disconnect electric trim and then trim manually. They were maintaining level flight, a slight climb actually, tried to trim manually, couldn’t, turned electric trim back on to try and use the electric trim again, then MCAS made one last input to drive them into the ground. They weren’t diving into the ground until after they’d tried all this stuff.
The Airbus adds the inputs of the side sticks, it also flashes a red light and says “DUAL INPUT, DUAL INPUT…” Either of the pilot’s can take over by pushing and holding a red take-over button on the side stick. The system will then announce “PRIORITY LEFT (or right)” and the dual input warning will cease.
The system is ok but it is a weak point compared to having linked controls ala Boeing.
True. What they needed to do was just nothing. It was flying ok before they lost airspeed indications so if you just do nothing at all it would probably keep flying ok.
That page has had some updates which may have not been there when you posted the link. The short story is that the A321NEO pitch issues are not related to the engines but rather to some flight control law changes made to make the aircraft more responsive in pitch at certain times. As you say, it will be fixed with a software update, in the meantime there is a CofG restriction.
Although the article doesn’t mention it, there are also some pitch issues on the A320NEO which are unrelated to the A321 but present similarly and have a similar mitigation.
The pilots can fly without it but when air speed is lost then the autopilot shuts off as does the engine auto thrust.
The two crashes have no relation to each other.
It seems to me that a properly trained and qualified pilot should be able to fly a plane without the autopilot and/or auto thrust.
Well, there is a relation in the sense that the pilots in both cases were apparently unable to manually fly their planes without a working autopilot.
On the Air France flight, everything went to crap when the autopilot shut off and the control logic switched to Alternate Law. Other than this, though, it was a perfectly flyable plane. The co-pilot then took this perfectly flyable plane and proceeded to put it into a stall and subsequent crash.
Regarding the Ethiopian Airlines crash, as I quoted upthread, the pilots repeatedly tried “to engage the autopilot, all of which were refused because autopilots are not recovery devices.”
Where do you get the idea the tail plane was close to neutral? It was nowhere near.
Actually, their altitude was gradually going up all the time except for the final seconds after the stab trim was re-activated and MCAS cut in again for the third time. There was a very slight dip after the first MCAS activation, but otherwise the altitude was under control.
There is no explanation for that 3 second gap after the first MCAS activation, except that the MCAS was overriding everything they did for 9 seconds, and it took them that long to realize the trim controls were working again.
The real problem was the airspeed. If they had reduced speed they might have been able to get the trim under control. But probably their instinct was not to reduce speed when they couldn’t afford to lose altitude.
The goal of controlled flight is to trim the yoke neutral. I honestly don’t understand what you don’t understand about this. They had override control of the MCAS system with pilot electrical trim and manual trim. they repeatedly countered the MCAS input. the procedure is to trim to neutral and shut it off.
If the plane was under control why did they have to dig 30 feet into the ground to find the engines? They demonstrated that they had trim control of the plane but there are gaps in their response that eventually took it down.
No the MCAS does not override pilot control of trim. The crew did nothing to abate this for 9 seconds. MCAS is overriden by autopilot, pilot electric trim, pilot manual trim, and flap extensions. You’re right there is no explanation for the gaps between MCAS and pilot trim.
You’re putting the cart before the horse. Airspeed is controlled by attitude. And as an aside, the 737 training procedure calls for moving the elevator back and forth to take the load off the jack screw if it’s too hard to move manually.
Maybe that’s the root cause of your misunderstanding.
See the wiki:
Nor could it be overridden by the electric trim, since MCAS was controlling the electric trim.
As for your other points… :rolleyes:
It’s a waste of time arguing with you, since you still haven’t acquainted yourself with the facts.
However, you can be quite sure that the entire 737MAX fleet isn’t grounded at a cost of billions a month, with no indication of when they might fly again, because of some elementary pilot error.
Magiver is correct on this.
The MCAS could not be overridden by pulling back on the control column but it could be overridden by operating the electric trim switches. Each time the electric trim switches were used, the MCAS would be disabled for 5 seconds and then it would reactivate with another 10 seconds of nose down trim. This subsequent MCAS operation could be interrupted by using the electric trim switches again and then the cycle would repeat. There is no technical reason why the electric trim could not have been used to keep the stabiliser in trim until the cutout switches were used. This is what Boeing expected the pilot’s to do.
The question then is, why didn’t they do it? Were they overwhelmed? Focussed on the wrong issue? Was there some mechanical issue that prevented the electric trim switches operating with the stick shaker going? When they trimmed nose up, disabling the MCAS, were they startled by the sudden g loading? Did that make them reluctant to trim aggressively nose up?
I think Magiver/’s view is that they were incompetent, but we don’t learn anything by writing a crew’s actions off as incompetent. The logical conclusion from that is that it won’t happen to us because we are not incompetent. My view is that we are all capable of doing the wrong thing at times. That we learn best by trying to imagine how we could perhaps make similar errors, if errors were involved, and what we could do to try and prevent such errors from occurring again. Do we need to focus training on different topics? Does the aircraft need to be redesigned? Do procedures need to be communicated better?
If that’s the case, then I apologise about that point.
Exactly right. Here is the opinion of two experts, a former 737 pilot and pilots’ union safety representative, and none other than Chesley “Sully” Sullenberger:
John Cox, previously a 737 pilot and pilots’ union safety representative, and Chesley Sullenberger, who successfully ditched US Airways Flight 1549 in the Hudson River, both did Flight Simulator replications of [Ethiopian] Flight 302. Cox described the rapid onset of unforeseen events as a “…breeding ground for confusion and task saturation.” Sullenberger commented that “Even knowing what was going to happen, I could see how crews would have run out of time and altitude before they could have solved the problems.”
The idea that the required procedures were “simple” and the pilots were simply incompetent is not just unrealistic, but as an investigative conclusion it verges on the ludicrous. Again, there’s a very good reason that the MAX remains grounded.