It can torn off the engines from the main body structure: https://asn.flightsafety.org/asndb/333926

While true, this was a pretty different situation in that it was 1959 (engineering standards have changed a lot in the last 65 years), and the dutch rolls were being performed intentionally for demonstration purposes.

> dutch rolls were being performed intentionally for demonstration purposes.

…with the yaw dampers (that are there to prevent Dutch roll) turned off.

1985 the dedliest single aircraft accident was due to dutch roll. Japan Airlines Boeing 747SR.

2013 KC-135 Stratotanker broke up in flight due to dutch roll.

2005 Airbus A310 survived with serious structural damage.

> 1985 the dedliest single aircraft accident was due to dutch roll. Japan Airlines Boeing 747SR.

This kind of buries the lede, right? A bad repair caused an explosion that blew off most of the vertical stabilizer (ie, the tail). The dutch roll was part of the series of unfortunate events that followed.

Of those three examples, only the KC-135 was caused by the dutch roll. The other two were caused by structural failures, the dutch roll was incidental.

This is extremely disingenuous. A dutch roll if identified and corrected is not structurally dangerous to an aircraft but it typically signifies something wrong with the control surfaces which is a larger issue. In the majority of the cases, it's the yaw damper that's a problem (my suspicion in the 737 case).

JAL 123 crashed because hydraulic pressure on all 4 hydraulic lines and 90% of the vertical stabilizer and 100% of the rudder were lost due to an explosive decompression of the aft pressure bulkhead. Dutch rolls ensued because of the loss of lateral direction control.

The KC-135 crashed because the rudder power control unit on the rudder was faulty and the pilots failed to identify the problem. They then used alternating rudder inputs to recover which caused the structural limits of the vertical stabilizer to be exceeded its structural limits and separate (along with the rest of the tail).

The Air Transat flight (961) had the entire rudder separate from the aircraft most likely due to stress fractures. This caused the aircraft to have extremely limited lateral directional control which caused the dutch rolls.

> engineering standards have changed a lot in the last 65 years

Especially for Boeing where standards are determined by the stock price

Maybe it's a feature, not a bug? Eventually, enough parts fall off that a whole new plane appears on the ground. It's just how the 737s reproduce.

Here's a video demonstrating it:

https://youtu.be/Zmjam1evDD4

I guess it’s worse than it looks? The video was kind of a dramatic let down to be honest. I preferred the mystery.

It looks a bit more intense in real footage.

https://www.youtube.com/watch?v=2tgfkGiHhxs

This should be the top comment.

Agreed.

Yeah, this has some elevation reference, and much more dramatic shifting.

A real-world video looks a lot scarier.

Linked downthread: https://www.youtube.com/watch?v=2tgfkGiHhxs

Especially if close to the ground.

this video posted elsewhere here seems dramatic enough

https://www.youtube.com/watch?v=2tgfkGiHhxs

Imagine you are in the cockpit at the top of the plane and your view/perspective - for a layman like me this would seem and feel like the flight is completely out of control. Even the passengers are bound to experience dramatic movements similar to severe turbulence I guess.

Idk. The idea of trying to control the aircraft which is doing this while being responsible for >100 lives seems pretty terrifying to me.

Yeah, could this be caused by turbulence? Winds?

Looking at the video, now i'm not sure I haven't been through some dutch rolls also.

Dutch Roll is a coupling of yawing and rolling dynamic modes, and is a product of the aircraft's aerodynamics. If the aircraft is disturbed off a steady-state path either by control input, changing winds, or turbulence, then it should return back to it's steady-state path with oscillations that quickly dampen. Dutch Roll is a phenomenon where these oscillations grow rather than dampen as a result of out-of-phase yaw and roll modes.

So Dutch Roll can be triggered by turbulence/wind, but the Dutch Roll itself is the result of something going wrong in reaction to that stimulus. This is different than the aircraft just being batted around by turbulence.

> This is different than the aircraft just being batted around by turbulence.

Does it actually look different or is it just a different cause for similar movement patterns?

Just being batted around by turbulence looks different if you know what you're looking for (although what to look for might be only obvious when looking at accelerometer data). Again, Dutch Roll is a very specific phenomenon as a result of coupling between the roll and yaw dynamic modes. The risk of Dutch Roll is that these oscillations can grow even without further stimulus rather than just dampen out.

The FAA reported: "AIRCRAFT EXPERIENCED A DUTCH ROLL, REGAINED CONTROL AND POST FLIGHT INSPECTION REVEALED DAMAGE TO THE STANDBY PCU, OAKLAND, CA." and stated the aircraft sustained substantial damage, the occurrence was rated an accident.

Standby PCU sounds like a control system. Was that a cause or effect of the event?

The PCU in this context is the part that moves the rudder. PCU issues were common on the 737 in the 90s[0] although that's... probably?... not relevant here.

[0] https://en.wikipedia.org/wiki/Boeing_737_rudder_issues

Exactly, rudder control issues could trigger or exacerbate Dutch roll. Loss of yaw damper control, in other words (yaw damper actuates the rudder).

For what its worth, that's very unlikely in the last decade or so. More likely to be moderate turbulence, which would be nearly indistinguishable in a non-severe event.

Dutch roll was particularly pernicious with trijets. It has to do with thrust vs lift vectors having different offsets (origins) relative to the cg. Sometimes they would add stabilizers to the tail to correct for this, but eventually manufacturers gave up on the design.

I feel like “roll” is a bad word for what’s happening here. In my brain, when I hear “roll”, I’m thinking a 360 degree rotation in either the vertical or horizontal axis (or both).

This is far from that (even in the real life footage linked in the sibling comments). This is more like a “Dutch wobble” or “tilt”.

But I’m not an aviator, so what do I know.

What you describe might be called a loop. In aviation, “roll” describes any rotation (not necessarily full 360) around the longitudinal axis, as “yaw” around the vertical and “pitch” around the lateral axis.

ETA: 360 degrees pitch is a looping, 360 degrees roll is a aileron roll or slow roll, a 360 degrees roll and pitch is a barrel roll, and 360 degrees yaw is “a 360”, ie a full circle turn.

"Roll" is the name for one of the three axes in aviation. "Vertical" and "horizontal" aren't very descriptive in three dimensions.

You could reasonably call yaw the "horizontal axis", but then assigning "vertical" to either of roll or pitch – and what do you call the other one then? They're arguably both vertical, depending on which side you look at the plane from! Additionally, at least "horizontal" implies an Earth-centered focus, which doesn't help while in, say, a barrel roll :)

Best to avoid the ambiguity entirely and use specific terms, just like how port and starboard avoid the "my left/right or yours" ambiguity nicely by always referring to the ship's frame of reference.

In any case, it sure beats a Dutch crunch.

I wonder if the name is related to the Dutch Tilt camera shot - https://en.wikipedia.org/wiki/Dutch_angle

Tha name is believed to be borrowed from an ice skating term:

https://en.m.wikipedia.org/wiki/Dutch_roll

https://www.iceskatesmuseum.com/e-disc-schoon.htm

Thanks for that explanation. I thought at first it was when you fart under the blankets...

I know the humorless HN is downvoting you but I gave you an upvote. Farts and fart jokes are always funny.

It’s being downvoted because it’s technically incorrect. They are describing a Dutch Oven.

Uh yes, they were being sarcastic.

Once again…the humorless HN strikes. Sheesh.

If the joke was worth making, the joke was worth suffering the downvotes. Have some courage in your convictions, and most importantly: don't whine about it.

My courage is strong, I’m willing to support a downvoted comment with another comment or two that I know will be downvoted to hell too…just to hold a mirror up to the humorless folk on here.

You do realise my comment was a joke right? In fact, I believe HN karma exists for the sole purpose of burning it on jokes.

I mean obviously they were being downvoted because it’s nothing to do with the Dutch, it’s just a fart fort.

Is an unfunny joke worth making? Aren't downvotes people telling you they don't find the joke funny?

It may have gotten lost in a sea of Boeing bad news.

> why [Dutch Roll] wasn't bigger news

I think the name is a serious problem. Something like “uncontrolled aircraft orientation” is more descriptive. “Dutch Roll” brings to mind thoughts of “is it better than Swiss Cake Roll?” and “is this news-spam for Hostess brand emerging from bankruptcy?”

There are terms of art, jargon, in many fields that mean something different than the “obvious” reading of the term. I had a discussion with someone on Hacker News recently that just could not understand that “dynamic programming” was a very specific solution technique for a broad range of problems with a special structure, rather than any sort of programming with a dynamic aspect to it.

Agreed. To the question at hand: “why 737-max’s ‘Dutch Roll’ wasn’t bigger news,” my conjecture is the term of art obscures the severity of the problem.

As a point of jargon, “Dutch Roll” is poor because the word roll within aeronautics could refer to an orientation movement or an acrobatic maneuver (and probably other things I don’t know about). The use of an ethnic/national identity as an adjective doesn’t help. Is “Dutch” associated at all with oscillations in two dimensions that are not intended by the pilot?

In plain English: unwanted tail waggle

"Tail lefty-righty no-no" is the industry term.

That's plane English.

You're on a roll

Not as scary as flying upside down which is what I originally thought based on title alone. Most people are familiar with "barrel roll" but by comparison this just looks like wiggling.

Counterintuitively though my understanding is that barrel rolls are generally safe even for large planes since it's a stable 1G maneuver (some jock irresponsible air force pilot used to regularly barrel roll B-52s until he did one too low and killed himself and the crew)...

I'm not aware of a B-52 being crashed in a barrel roll, but this did make me think of the 1994 Fairchild crash[0] that was caused by a pilot who was known as dangerous due to excessive self confidence. In this case he banked too tightly at low level causing a stall into the ground. The whole crash was caught on camera[1], which is indelibly burnt into my memory.

[0] - https://en.wikipedia.org/wiki/1994_Fairchild_Air_Force_Base_...

[1] - https://theaviationgeekclub.com/the-story-of-bud-holland-the...

Thanks, my mistake, this is what I was referring to. Apparently "Bud" would brag about "rolling" B-52s (https://www.historylink.org/File/8716), but the fatal crash was actually just a low-altitude stall as you pointed out. It's now a textbook case study for systemic leadership failure.

Dutch roll, Bud Holland... Netherlands trifecta is in play.

The last 3 seconds of your life as the copilot must have been some revolting emotion knowing that the overconfident asshole in the seat next to you just killed you.

Man, that is just one big ass airplane to even consider wanting to do any kind of maneuvering without threat indicators blinking/buzzing/beeping/toning that your death is imminent without doing some of that "pilot shit".

The story from your [0] about one of the crew's last flight with his family on the ground waiting for the post-flight rituals where his wife and 2 kids watching is just horrific. What a fucking asshat of a person.

I'm pretty sure that's the crash GP was referring to. It sort of looks like he could have been going into a barrel roll.

AFAIK only one Boeing passenger jet ever performed a barrel roll (without passengers on board): https://simpleflying.com/boeing-707-barrel-roll-seattle/

> it's a stable 1G maneuver

It’s positive G, but 0.5 up to 2G (otherwise, given that lift is “towards the ceiling of the plane”, so not always straight up during the manoeuvre, you’d accelerate downward, and arresting the fall requires >1G).

> barrel rolls are generally safe even for large planes since it's a stable 1G maneuver

Maybe "safe" here means that merely the stress of the maneuver itself wouldn't destroy the craft? But surely the loss of lift is likely to put it at significant risk, as in your example.

You dont lose lift in a barrel roll, you merely change the direction that lift is being generated.

When the threat is the ground, maybe that's what's worrying anyway.

Ah, good point ;)

That depends on what you mean by “generally safe”. Airline jets are not made to withstand the forces of an aerobatic maneuver and while they can do it in test flight conditions, each time requires pulling the jet out of service afterwards for a full structural inspection.

A barrel roll is a 1-G maneuver and will not overstress an aircraft unless done improperly.

Up to 2 or 3G, but most aircraft should withstand that, even gliders.

Probably wasn't a B52. Tex Johnston was reknowned for barrel rolling a 707 during a demo back in the day - there's grainy video of it on youtube. Apparently the Boing execs at the demo didn't know it was going to happen and nearly had heart attacks when he did.

Video on youtube: https://www.youtube.com/watch?v=iz1Eze3QrDU

Bob Hoover rolled a plane while pouring a tea.

https://www.youtube.com/watch?v=V9pvG_ZSnCc

Tex flew in cowboy boots and, well, was named Tex. I don’t know what they thought would happen.

Tex Johnson

Thanks, corrected.

A barrel roll or an aileron roll? Most people call an aileron roll a barrel roll (no thanks to Star Fox)

The Fairchild AFB crash was not a barrel roll.

Just flew a Max from Denver to Mexico City a couple days back.

It was mostly uneventful, but as we were preparing to land the aircraft banked hard to the left and began to experience something akin to this...like it hit a sudden pocket of turbulence at the apex of the turn and began to pogo around.

It was minor and far from inducing damage to the vehicle, but in that moment remembered where I was while clenching my body for a few nervous seconds until we eased out of the turn.

Do you fly to Mexico city often? The altitude makes landings unusually eventful.

This is my third time and I'm familiar with altitude weirdness having lived in Denver for several years, that rollercoaster effect.

The other parts of the descent were smooth until specifically hitting its maximum bank, then it suddenly got squirrelly and then stopped as the plane began to flatten. It's as if the degree of bank was beyond the plane's limits.

I've flown hundreds of times and can't recall ever experiencing something quite like this.

EDIT: I just realized my original comment was written incorrectly. The plane didn't expectedly bank, it's that this started happening at the top of a hard bank.

> like it hit a sudden pocket of turbulence at the apex of the turn

I wonder if this could have been wind shear? Wind shear was deemed as the cause of the crash for Delta 191[0] on approach to DFW in the 1985. Lots of new equipment was installed after to detect wind shear. I wonder of MEX has that kind of equipment.

[0] https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191

Possibly, I don't think so. It happened right at the top of the bank and stopped as the plane began to ease out.

There were no weather issues no other incidents of turbulence or jostling around. It seemed as if the plane was having problems banking at that angle.

Sounds quite a bit like wake turbulence. As planes move through the air, they leave air vortices called “wake” (much like a boat does in water). This effect is worse when airplanes are slow, like when they’re coming into land. Pilots try to avoid each other’s wake, but it’s invisible and sometimes you do hit it if the controller vectors you close behind another aircraft.

It produces a strong rolling motion and can even flip small airplanes.

I hope nobody got hurt (assume so, you may have told you otherwise). Is this something pilots get trained for how to cope with this type of incident?

What happened to passengers (are they usually injured from things falling/flying around)?

Boeing is getting some bad news these days, but multiple whistle-blowers in a row is the worst.

It wasn't that extreme, it was what I would consider a medium level of turbulence. I just realized my comment wasn't written correctly - the bank itself is what caused the issue, not that it just suddenly started banking unexpectedly. What was interesting was that it specifically started and stopped as it eased into and out of the turn.

I had a similar experience as a child flying into Phoenix... there were heavy storms and about 100ft from the ground, the plane just shifted to the side several hundred feet... the pilot pulled back up and had to circle around the airport for another landing approach. Kinda wild.

The question is how bad the oscillations were, and how long they lasted. Maybe for the passengers it was indistinguishable from "regular" turbulence?

E.g. wibble-wobble or the more pronounced wibbly-wobbly.