Incident: Southwest B38M at Phoenix on Feb 24th 2023, no autopilot trim(avherald.com)
avherald.com
Incident: Southwest B38M at Phoenix on Feb 24th 2023, no autopilot trim
https://avherald.com/h?article=505d0701
8 comments
If you enjoy this type of thing, check out https://youtube.com/@VASAviation for animated flights combined with ATC radio traffic. There are MUCH more interesting incidents posted weekly. I'm not affiliated - just a fan.
Is this even all that unusual? Certainly mechanical issues occur sometimes that require a plane to land again shortly after taking off. Given that the plane went back into service 14 hours later, it seems unlikely that it was a software problem (similar to the MAX issues over the past few years), no?
I'd of course be curious to read more details and an explanation of the root cause, but it's presumably too soon for that...
I'd of course be curious to read more details and an explanation of the root cause, but it's presumably too soon for that...
"no autopilot trim and no electrical trim" doesn't sound like a mechanical issue to me, but the underlying issue certainly could be. Of course, things like this do occur, but you would think that on a newly delivered plane that passed Boeing's QC, this wouldn't happen. And, as a pilot, if you see these issues you probably start wondering what else might be wrong. After all, one of the most pointless and horrifying aircraft accidents in recent years (https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261) also initially looked like a trim issue. Not to mention the two 737-MAX crashes of course, where it was also ultimately the horizontal stabilizer trim that flew the planes into the ground.
The lesson is, if you have a trim issue, turn it off and land.
This was the first revenue flight for that plane. Inappropriate? Yes. Unusual? Not for Boeing.
The US Air Force stopped taking deliveries of the KC-46 for a period of time because of sloppy assembly (FOD). One of the ME3 airlines stopped taking delivery of 787s built at the east coast plant because of FOD and other sloppy assembly problems (and Boeing's had to stop delivery a few times on the 787 because of assembly/manufacturing problems). Boeing got into a bit of hot water with the 737NG because they were hand building parts that were supposed to be CNC'd. Stuff like that.
One of the key problems that I vaguely remember is that Boeing did away with a lot of the manual quality control checks in favor of automated checks with no oversight. As Tesla's learned some things are extremely difficult to automate.
The US Air Force stopped taking deliveries of the KC-46 for a period of time because of sloppy assembly (FOD). One of the ME3 airlines stopped taking delivery of 787s built at the east coast plant because of FOD and other sloppy assembly problems (and Boeing's had to stop delivery a few times on the 787 because of assembly/manufacturing problems). Boeing got into a bit of hot water with the 737NG because they were hand building parts that were supposed to be CNC'd. Stuff like that.
One of the key problems that I vaguely remember is that Boeing did away with a lot of the manual quality control checks in favor of automated checks with no oversight. As Tesla's learned some things are extremely difficult to automate.
For those not familiar with the acronym FOD: https://en.wikipedia.org/wiki/Foreign_object_damage
Automated checks no one is actually looking at may as well not even be happening.
https://fodprevention.com/boeing-overhauls-quality-controls-...
https://www.heraldnet.com/business/boeing-revamps-quality-co...
https://www.washingtonpost.com/archive/politics/2006/04/17/b...
https://www.heraldnet.com/business/boeing-revamps-quality-co...
https://www.washingtonpost.com/archive/politics/2006/04/17/b...
Doesn't change my point.
In fact, reinforces it. You must check. How do you know the device is calibrated? Is the sensor you're relying on still trust worthy? What happens when your fancy Bluetooth sensor breaks, and you've forgotten how to measure things the old fashioned way?
Now I'm glad Boeing is taking inspiration from Toyota; but American companies tend to lose sight of a key part of the teachings of Demmings: just do it right the first time is wrong. You must build your business around the assumption it will be wrong, (because it always will be), and generate data to be reviewed that can be acted upon to improve processes.
Besides which; remember, the real objective there is cost savings by Quality department downsizing, coupled with remaining Quality Inspector upskilling, which comes with increased cognitive overhead for the inspector, which will manifest in a lower detection rate because you can only be in so many places at once.
T. Decade-on Quality Assurance guy/builder of testing departments.
Companies hate us because we're the one group in the building who can objectively measure how badly everything sucks; yet you can't let up, no matter how badly you're treated because once you stop looking, someone down the line'll pay for it.
And that's just not Quality.
In fact, reinforces it. You must check. How do you know the device is calibrated? Is the sensor you're relying on still trust worthy? What happens when your fancy Bluetooth sensor breaks, and you've forgotten how to measure things the old fashioned way?
Now I'm glad Boeing is taking inspiration from Toyota; but American companies tend to lose sight of a key part of the teachings of Demmings: just do it right the first time is wrong. You must build your business around the assumption it will be wrong, (because it always will be), and generate data to be reviewed that can be acted upon to improve processes.
Besides which; remember, the real objective there is cost savings by Quality department downsizing, coupled with remaining Quality Inspector upskilling, which comes with increased cognitive overhead for the inspector, which will manifest in a lower detection rate because you can only be in so many places at once.
T. Decade-on Quality Assurance guy/builder of testing departments.
Companies hate us because we're the one group in the building who can objectively measure how badly everything sucks; yet you can't let up, no matter how badly you're treated because once you stop looking, someone down the line'll pay for it.
And that's just not Quality.
737MAX has a design problem that attempted to use software to cover it up. Boeing stuffed in big fans which needed to be higher to not scrape the runway. The fans stick out forward from the wings, which can cause the plane to pitch up. Software attempts to hide that design flaw, and pushed down really hard a couple times into the ground.
Really needs a new type certification, though FAA and flying public generally don't seem to care.
Really needs a new type certification, though FAA and flying public generally don't seem to care.
> 737MAX has a design problem that attempted to use software to cover it up.
The design requirements of the software were wrong. Not the airplane, not the implementation of the software.
The design requirements of the software were wrong. Not the airplane, not the implementation of the software.
Of note is that the A320 has three angle of attack sensors, while the MAX only has one -- no redundancy.
That's not true. The MAX always had two sensors, it's just that the software design only ever used one of them at a time.
Man imagine being on that development team. I wonder if anyone thought it was a bad requirement at the time and whose job it was to identify that (and was the issue flagged and if not why not). A programmer isn’t an aeronautical engineer but it really says how a whole systems view is necessary.
I work in a field with increased specialization but we build systems and sometimes similar things come up. There are few who see the end to end system for itself.
I imagine rockets and the space shuttle get that level of scrutiny and that books have been written about it.
I work in a field with increased specialization but we build systems and sometimes similar things come up. There are few who see the end to end system for itself.
I imagine rockets and the space shuttle get that level of scrutiny and that books have been written about it.
They knew a dual/multi-sensor system would be required. They aldo knew putting one in would have mandated simulator training; and they had to avoid that at all costs.
That's why the MAX accidents are so notably engineering failures; the industry knew what needed to be engineered, but business shot it down, and forced them to build something fundamentally unsafe in the interests of maximizing profit, and not sweating the product in the box.
That's why the MAX accidents are so notably engineering failures; the industry knew what needed to be engineered, but business shot it down, and forced them to build something fundamentally unsafe in the interests of maximizing profit, and not sweating the product in the box.
Well, having two is functionally the same as having just one since you fundamentally can't tell which one is good when there's a single failure.
Two in an improvement.
With only one you can be in one of 3 states:
S1. The sensor is returning correct readings.
S2. The sensor is returning readings but they are not correct.
S3. The sensor is not returning readings.
To the pilot (or automation) using the sensor there are only two states:
S1. Both sensors are returning correct readings.
S2. Both sensors are returning the same incorrect readings.
S3. One sensor is returning correct readings and one sensor is returning incorrect readings.
S4. Both sensors are returning incorrect readings which do not match.
S5. One sensor is returning correct readings and one is not returning readings.
S6. One sensor is returning incorrect readings and one is not returning readings.
S7. Neither sensor is returning readings.
The states the pilot (or automation) sees are
Here are some numbers.
If the sensor works fine 98% of the time, but 1% of fails in a way that gives false readings, and 1% of the time fails in a way that gives no readings, then when the pilot gets a reading on the single sensor plane there is a 98.99% chance it is right.
On the two sensor plane when the pilot gets a reading that is the same on both sensors there is a 99.99% chance that reading is right. If the pilot only gets a reading from one sensor then it is the same as the single sensor plane case, 98.99%.
Overall, on the two sensor plane if the pilot checks the sensors and accepts the result when the two sensors agree on a reading or when only one sensor gives a reading, they will be getting a correct result 99.97% of the time.
With only one you can be in one of 3 states:
S1. The sensor is returning correct readings.
S2. The sensor is returning readings but they are not correct.
S3. The sensor is not returning readings.
To the pilot (or automation) using the sensor there are only two states:
U1 = S1 + S2.
U2 = S3.
S1. Both sensors are returning correct readings.
S2. Both sensors are returning the same incorrect readings.
S3. One sensor is returning correct readings and one sensor is returning incorrect readings.
S4. Both sensors are returning incorrect readings which do not match.
S5. One sensor is returning correct readings and one is not returning readings.
S6. One sensor is returning incorrect readings and one is not returning readings.
S7. Neither sensor is returning readings.
The states the pilot (or automation) sees are
U1 = S1 + S2
U2 = S3 + S4
U3 = S5 + S6
U4 = S7
Here are some numbers.
If the sensor works fine 98% of the time, but 1% of fails in a way that gives false readings, and 1% of the time fails in a way that gives no readings, then when the pilot gets a reading on the single sensor plane there is a 98.99% chance it is right.
On the two sensor plane when the pilot gets a reading that is the same on both sensors there is a 99.99% chance that reading is right. If the pilot only gets a reading from one sensor then it is the same as the single sensor plane case, 98.99%.
Overall, on the two sensor plane if the pilot checks the sensors and accepts the result when the two sensors agree on a reading or when only one sensor gives a reading, they will be getting a correct result 99.97% of the time.
With two, you can tell that one is wrong, so you shut off any automatic systems that depend on it. This is where MCAS went wrong.
Different handling at the edge of the flight envelope is not a "design problem". The design is fine, it just handles differently from the other versions in certain regimes so they (attempted, poorly) used software to avoid that
My understanding is that it was failing an airworthiness requirement without MCAS: https://www.law.cornell.edu/cfr/text/14/25.175
If by "different handling" we mean "not airworthy", I wouldn't say the design is fine.
If by "different handling" we mean "not airworthy", I wouldn't say the design is fine.
I believe that is false, as MCAS should (when correctly implemented) only apply at the edge of the flight envelope and those airworthiness requirements are all related to normal regimes. I can't find anything supporting your understanding
Look harder.
https://aviation.stackexchange.com/questions/73132/did-boein...
No MCAS = does not meet the criteria to be employed in Civil Air Transport in the United States.
There were several failures on the system architecture front as well, including a vulnerability to single event upset, where a cosmic ray flipping a single bit in the FC in vommand would trigger an MCAS failure state that the average civil aviation trained pilot was found not to be able to successfully cope with.
It's also in the NTSB and FAA final reports, as well as several House generated investigations.
I spent waaaay too many hours doing that math by hand and looking up crap on Engineering Toolbox to easily forget/forgive that.
https://aviation.stackexchange.com/questions/73132/did-boein...
No MCAS = does not meet the criteria to be employed in Civil Air Transport in the United States.
There were several failures on the system architecture front as well, including a vulnerability to single event upset, where a cosmic ray flipping a single bit in the FC in vommand would trigger an MCAS failure state that the average civil aviation trained pilot was found not to be able to successfully cope with.
It's also in the NTSB and FAA final reports, as well as several House generated investigations.
I spent waaaay too many hours doing that math by hand and looking up crap on Engineering Toolbox to easily forget/forgive that.
If you read AvHerald you’ll see that worldwide there are half a dozen mechanical incidents on various commercial aircraft every day.
Mechanical incidents is one thing, but is it also the case of pilots declaring an emergency?
[edit] though it looks like they declared an emergency out of an abundance of caution
[edit] though it looks like they declared an emergency out of an abundance of caution
Declaring an emergency is, oddly, fairly routine. There are surely dozens each day. (I’ve declared three in a little over 1500 hours of flying piston aircraft.)
When you have an abnormal condition that gives you doubt about the aircraft state and priority ATC handling would be helpful, declare an emergency. It’s as simple as that.
When you have an abnormal condition that gives you doubt about the aircraft state and priority ATC handling would be helpful, declare an emergency. It’s as simple as that.
Yep. Emergency isn’t the “we’re all going to die” it’s “something is not right and we’re deviating from the flight plan and need priority”.
https://www.flightradar24.com/blog/squawking-7700-in-flight-...
Closest I ever got was 7600 for a full radio stack loss.
https://www.flightradar24.com/blog/squawking-7700-in-flight-...
Closest I ever got was 7600 for a full radio stack loss.
I'm wondering how it passed preflight. Isn't the trim tested?
You test the range of motion preflight but you can’t test the results of said motion without actual airflow over the stabilizer.
Um, if the stabilizer moves, it works. No need to test airflow.
You can get a trim tab that "works" but doesn't "stay" in position (one of the walk-around checks on a small plane it to set the trim max in one direction, make sure it moves correctly when you move the stabilator, set in the other direction, recheck) but you can't reach them on a large jet.
There have been cases where the ONLY thing working on the tail was the trim tab, the yoke cables broke - you can land a plane with only the trim if you really need to.
There have been cases where the ONLY thing working on the tail was the trim tab, the yoke cables broke - you can land a plane with only the trim if you really need to.
On a jet there should be an indicator of the trim position that is independent of the actuator mechanism.
I don't think it's tested explicitly, but you usually need to trim the aircraft for takeoff.
Noteworthy comment from the website.
* WN Delivery Process By Retired on Wednesday, Mar 1st 2023 22:12Z*
On the delivery flights I rode on, after the crew had a meal at the Boeing delivery center and signed the acceptance paperwork. WN dispatch would assign a delivery flight number to one of several "make ready" contract centers. Were various items would be done to bring the aircraft to the current WN configuration. From there it would be released to the line. One of the "make ready" centers is in Phoenix. I suspect in the short time used to turn this aircraft around something was not correctly finished by the "make ready" folks. In the pre-MAX days, the aircraft would be in the contract "make ready" center for a couple of weeks.
* WN Delivery Process By Retired on Wednesday, Mar 1st 2023 22:12Z*
On the delivery flights I rode on, after the crew had a meal at the Boeing delivery center and signed the acceptance paperwork. WN dispatch would assign a delivery flight number to one of several "make ready" contract centers. Were various items would be done to bring the aircraft to the current WN configuration. From there it would be released to the line. One of the "make ready" centers is in Phoenix. I suspect in the short time used to turn this aircraft around something was not correctly finished by the "make ready" folks. In the pre-MAX days, the aircraft would be in the contract "make ready" center for a couple of weeks.
Boeing 737-MAX, I don’t know if it’s the increased coverage or poor quality/design/software flaws but
I always check the plane before booking a flight to ensure I don’t get on one of these.
I dunno, I would trust it more. Like when the IBM Deskstar drive line had a huge failure which tanked their reputation, I bought the next model line because they have to be extra careful not to screw up again. They were then the most reliable drives (until getting bought by Hitachi and then WD, but whatever). Anecdotal of course, but it makes logical sense to me to go in on the reputation saving product after an established engineering brand loses face.
This is just dumb. The plane has a compromised design that they tried to paper over with software.
None of the design issues have gone away with better software.
None of the management and engineering culture problems have gone away at Boeing. And even if they had done a 180 on both, this particular plane is still compromised.
All they did is the minimum amount of work to be able to fly again.
None of the design issues have gone away with better software.
None of the management and engineering culture problems have gone away at Boeing. And even if they had done a 180 on both, this particular plane is still compromised.
All they did is the minimum amount of work to be able to fly again.
This. I am not enough of an expert to evaluate the flaws, so my safe bet is - avoid flying in them.
I gain nothing by flying in those planes where I can find good alternative flights, so why risk it, even if the risk is very low?
I gain nothing by flying in those planes where I can find good alternative flights, so why risk it, even if the risk is very low?
I dunno, I would trust it more
And, really, even if the MAX were a stellar plane it still doesn't meet the same crash standards that any newer aircraft (including the A320) has to meet. Your C-series or A320 have seats and floor structures designed to withstand forces of up to 16Gs. The 737? Grandfathered in with 9G seats. It's long past time to retire the 737. It's one thing to keep flying them until the wings fall off, but it's another to sell brand new 737s in 2023.
What the whole 737 MAX/MCAS debacle highlighted was that the 737 is a design that is more than 50 years old, and that Boeing can only update it within strict limits, because otherwise it would need a new type certificate, which airlines with massive only-737 fleets like Southwest or Ryanair want to avoid at all cost. So, even with the particularly egregious problem which crashed two planes fixed, my trust in the 737 has diminished considerably.
From experience (personal, our data center operations and Backblaze yearly drive stats [0]) WD is one of the best, if not the best hard drive vendor for quite some time.
Seagate tanked their reputation, but IronWolf Pros seem to work well, too.
[0]: https://www.backblaze.com/blog/backblaze-drive-stats-for-202...
Edit: BTW, HGST is WD, too. :)
Seagate tanked their reputation, but IronWolf Pros seem to work well, too.
[0]: https://www.backblaze.com/blog/backblaze-drive-stats-for-202...
Edit: BTW, HGST is WD, too. :)
Boeing is not IBM of that era. Far from it.
It’s the very beginning of the bathtub curve. I wouldn’t draw too many conclusions from this.
It sounds like it was the plane's first revenue flight, too.
[deleted]
I'm not a pilot and don't know much about aviation, but isn't the point of still having human pilots on board that they should be able to fly the plane without issues in case of an autopilot malfunction. Was this really an emergency that necessitated returning to the airport? It was a 2 hour national flight. Can't commercial pilots fly plans for even just 2 hours anymore?
This isn't criticism or a rant, I'm genuinely curious to know.
This isn't criticism or a rant, I'm genuinely curious to know.
> The crew subsequently declared emergency advising they had no autopilot trim and no electrical trim system on their brand new aircraft and needed to trim the aircraft manually
I would assume the bigger problem was loss of the electrical trim system. From what I understand, manually trimming a 737 (or any large commercial jet) is a physically demanding task, even with both crew members doing it in tandem. That will add a lot of workload to the pilots that could cause further delay in reacting to new problems as they arise, and there's always the chance that can happen. When a malfunction like this occurs, it is absolutely safest to land as soon as possible so the issue can be assessed on the ground, especially when relevant failure checklists or company policies indicate it.
I would assume the bigger problem was loss of the electrical trim system. From what I understand, manually trimming a 737 (or any large commercial jet) is a physically demanding task, even with both crew members doing it in tandem. That will add a lot of workload to the pilots that could cause further delay in reacting to new problems as they arise, and there's always the chance that can happen. When a malfunction like this occurs, it is absolutely safest to land as soon as possible so the issue can be assessed on the ground, especially when relevant failure checklists or company policies indicate it.
That makes sense, thanks! I'd missed that part when I scanned the page and the headline is misleading in that case, since it only mentions autopilot when it should be the other way around.
Pilots follow checklists. In case of anything ever going wrong or even just getting in the aircraft they go through a checklist. The error popped up and the checklist said 'try x' and 'x' didn't work so it probably said 'if you can divert, do that', so they did.