Earlier quoted context omitted.
1593699 is amazing.
I have to wonder at the fit-and-finish that would allow full-sized pieces of paper to fall inside an instrument console.
Maybe Boeing poached the guys responsible for Tesla's panel gaps, who knows?
Boeing 737 Max pilots complained to feds for months about suspected safety flaw
141–150 of 307 posts
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#142Earlier quoted context omitted.
In those cases (if they are not two reports of the same incident), while MCAS was discussed prior to the flight, the actual incident appears to be autopilot related, and there is no mention of the trim running away and having to be disabled. In fact, the Captain's report mentions that he chose to engage the autopilot earlier than usual, "to remove the possible MCAS threat."
I'm a developer and not a pilot but I think that's pretty relevant. In both of those (two separate) cases, the pilots were aware of MCAS (it's not supposed to run when autopilot is on, right?) and tried to avoid any interference from it, yet they experienced interference anyway. One of those examples was nose down which sounds like MCAS and the other was unexpected leveling off at the wrong altitude.
There is no evidence, in these reports, that 'interference' from MCAS had anything to do with it. The fact that the problem occurred when the autopilot was engaged (and MCAS, therefore, supposedly disabled) and was resolved by disengaging the autopilot, suggests a problem with the autopilot, not MCAS. The captain's report speculates about possible causes, but MCAS failure is not on the list, even though, as we know, the captain was aware of MCAS and its failure modes.
From the reports:
Synopsis
B737MAX Captain reported an autopilot anomaly in which led to an undesired brief nose down situation.
Synopsis
B737 MAX First Officer reported that the aircraft pitched nose down after engaging autopilot on departure. Autopilot was disconnected and flight continued to destination.
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#143Earlier quoted context omitted.
Which Airbus model is affected?
Probably referring to A330: https://en.wikipedia.org/wiki/Qantas_Flight_72 They never quite figured out the root cause of the un-commanded dives
> Probably referring to A330
A330 has figured in the incidents, but AFAIK the flight control software and angle of attack sensors that are implicated in those incidents are the same in all of the Airbus models.
> They never quite figured out the root cause of the un-commanded dives
Yes, they did. Read the "Conclusion" under the "Final Report" section. The "design limitation" they're referring to is that, first, the autopilot is not driven by an average or majority vote of the three angle of attack sensors, but by one of them only (which one depends on whether the captain or first officer's position engaged the autopilot), and second, the other two angle of attack sensor inputs are not used to check the sensor that is driving the autopilot, so if that sensor gives faulty input (the "multiple spikes" described), the faulty input is allowed to trigger uncommanded events such as the violent pitch down that happened on Quantas Flight 72.
What should happen is that the input from all three angle of attack sensors should be combined: as long as all three of them are within some tolerance, the average of the three becomes the angle of attack used to drive the autopilot. If one goes out of tolerance compared to the other two, its input is discarded until it comes back into tolerance (so "multiple spikes" from one sensor would simply be ignored). If it takes too long for the one sensor to come back into tolerance compared to the other two, that sensor gets ignored for the remainder of the flight and the pilots get notified. If it gets to a point where no two of the sensors are within tolerance of each other, the autopilot gets disengaged and a big red light goes on in the cockpit. I am unable to understand why that is not how the system is designed, but the investigation reports make clear that it isn't.
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#144Earlier quoted context omitted.
Thanks for the documents! I searched through item 1 for 'trim', and while I found some trim failure reports, and the complaint about Boeing's nondisclosure of MCAS in its documentation, I did not notice any concerns over disabling a runaway trim situation.
Not a pilot here (developer) but doesn't "nose down" imply trim? If so, one of those pilot reports in the Dallas News story does say that they experienced uncommanded nose down. Both pilots were aware of MCAS and discussed it before the flight. Another one who also knew of MCAS reported uncommanded leveling-off at the wrong altitude. Is that not trim, too?
"Nose down" does not imply a trim adjustment, as the primary control in pitch is performed by the elevator, while trim adjustment, on this airplane, is done by rotating the horizontal stabilizer. From the fact that the pitch changed, we cannot tell whether it was commanded by the autopilot or MCAS, but as MCAS is supposed to be disabled when the autopilot is engaged, and this occurred when the autopilot was engaged, it appears less likely that it was MCAS than it was the autopilot.
Furthermore, the signature feature of the MCAS failure that downed the Lion Air flight was runaway trim, and there is no indication in this report that the crew had to take any action to stop it by disabling MCAS (setting STAB TRIM CUTOUT to CUTOUT, the documented procedure for doing so), or to restore the correct trim manually (as far as I know, it would not revert to the correct setting simply because MCAS was disabled.)
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#145Earlier quoted context omitted.
regex? I just grepped "B737 max" and found 11 entries. "737.{0,20}max" (case insensitive) yields 20. [0] [0] CSV output: https://pastebin.com/87N023cx
So 20 MAX-related issues out of ~850. How is that significant?
> So 20 MAX-related issues out of ~850. How is that significant?
To build on what @ggm and @siwatanejo noted. The 737 debuted in 1967, so it is 52 years old now. The 737 MAX is 2 years old. In terms of number of issues per year since the aircraft was introduced the 737 is at ~15 incidents per year and the 737 MAX is at ~10/year. But as @ggm notes, it's important to look at when in the life cycle many of the non-MAX 737 incidents occurred.
Another way to look at this is by number of aircraft produced. The Boeing website[0] gives production numbers for various classes of the 737. In terms of incidence per number of aircraft delivered the non-max 737s have 0.082 incidents per delivered aircraft while the 737 MAX has 0.05 incidents per delivered aircraft.
Both of those suggest that the 737 MAX may not be any worse than the non-max 737s, but a more careful statistical analysis is probably necessary to draw strong conclusions.
[0] http://active.boeing.com/commercial/orders/displaystandardre...
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#146Earlier quoted context omitted.
Boggles the mind on several levels: 1. That airlines would use consumer tablets without hard-copy backup as matter of procedure. I remember Air Canada announcing it and how it would save so much weight for both pilots and the airplane, and thinking... I print my Google Maps as a backup for roadtrips, I sure as heck would do it on a flight! 2. Perhaps I'm misjudging, but the tone and perspective of pilot makes me worr…
As a non technical person, who is about to fly an 80 ton vehicle for extended distances, local backups of WiFi dependent data is not likely to be a major concern. Especially if (a) it’s not part of your extensive checklists, which would reasonably be expected to be included if it was important, and (b) you’ve lost WiFi in other planes before without losing your flight plan.
I’m a technical person and it is a major concern.
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#147Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#148Please make a conscious choice when flying 737 Max on US domestic flights. It is your right to know the type of aircraft when you are booking your flight. Switching to a reasonably expensive alternative is worth more than any foreseeable trouble.
At this point I wouldn't be booking on a Max for a while just in case they ground them all, if nothing else.
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#149This is off topic. But I've been skeptical of the commercial aviation accident risk compared to cars. I'm not saying cars are safer. But using accident count per mileage seems a bit odd, especially when the most risky parts of flying are taking off and landing. A plane travelling 400 more miles doesn't incur much more risk. But a car travelling 400 more miles incur a much bigger risk (e.g. fatigue, car malfunctioning…
The same sort of problem occurs on the other end when you try to compare the risk of driving vs walking. Cars are 5 times faster in the city and 20 times faster on the highway than walking. The trips are almost always shorter on foot, you drive to the far away big box store but would walk to the neighbourhood store. Better metrics than risk per unit of distance would be risk per unit of time spent or risk per trip.
I would point out that in a similar way few people drive between continents but flight is common.
Re: Boeing 737 Max pilots complained to feds for months about suspected safety flaw
#150Earlier quoted context omitted.
It would be ironic if the lack of 737-MAX category for reports is why these reports never made it to the people who needed to see them, which caused the issue to go unnoticed.
1555013 is pretty damning in telling how the airlines treated the MAX as the same type as the 737-800: "I had my first flight on the Max [to] ZZZ1. We found out we were scheduled to fly the aircraft on the way to the airport in the limo. We had a little time [to] review the essentials in the car. Otherwise we would have walked onto the plane cold.My post flight evaluation is that we lacked the knowledge to operate th…
Wow... I wonder how much of this could have been avoided if the 737-Max had just been given an entirely new model name like "738".
I'd assume that when the 777's came out even pilots with experience on the 767 and other Boeing planes were still given ample training beforehand. The minor difference in the Max's model name disguises the seemingly large difference in their operation.