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Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

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Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#131

Post by lxgr »

jader201 wrote: post #87
tjpnz wrote: post #20

Earlier quoted context omitted.

Here's a video demonstrating it: https://youtu.be/Zmjam1evDD4

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.

"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.

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#132

Post by izolate »

kleiba wrote: post #129
rollulus wrote: post #108

As a Dutchman the endless list of apparent “Dutch” things never ceases to surprise me. Uncles, courage, ovens, double, going, etc., and a new one to my list: rolls. And none of them means any good.

Half of them refer to "German" things, where the word "deutsch" underwent some pronunciational variation.

Actually, a lot of these pejoratives are from the 19th century. By the 17th century, the word "Dutch" had begun to solidify its meaning around the Netherlands.

This mainly stems from a time when tensions between the British and Dutch were at their peak, due to competition.

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#133

Post by solardev »

belter wrote: post #21
blakesterz wrote: post #4

"Dutch Roll is a coupled out of phase movement of the aircraft as result of weakened directional stability (provided by the vertical tail and rudder), in which the aircraft oscillates around its vertical as well as longitudinal axis (coupled yaw and roll)." That sounds pretty scary. I wonder why it wasn't bigger news when it happened last month?

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

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.

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#134

Post by pfannkuchen »

FabHK wrote: post #127
marcus0x62 wrote: post #24

Years ago, my father in law ( a heavy jet mechanic) got sent to China for two months as part of a team to diagnose and fix a recurring dutch roll complaint on a particular airframe. This was for a A300-series flown by a large freight carrier. The local mechanics couldn’t figure it out, so this team was assembled from the mechanics at headquarters to fix the plane. They inspected the plane and found no damage. They ha…

> they simply did not like this particular plane. …and employed a face-saving (though probably very expensive) way of communicating it.

I suspect the face saving culture is holding China back significantly since it adds a ton of noise to interpersonal signal propagation. I wonder if the government is doing anything social engineering-y to try to reduce it?

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#136

Post by rl3 »

CoastalCoder wrote: post #77
rl3 wrote: post #59

Earlier quoted context omitted.

> If it's a software issue, I'd think owners would be pretty clear on its status on each plane. Ha. I have some bad news for you: https://www.bloomberg.com/news/articles/2019-06-28/boeing-s-...

I can't read that article, but I'm assuming (hoping?) that even if the software is flawed, there's still clarity about which source code / build configuration is installed on a given plane. Contrast that to the allegedly faked test results, and known defects, of the planes' physical characteristics.

The source article was talking about how their software practices were so bad they’d hire $9/hr engineers to work on core avionics stuff.

As for your point: There’s not much contrast. MCAS was software, after all.

Only upside to software is because it can be updated (maybe), it’s at least more likely to be fixed instead of covered up.

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#137

Post by psunavy03 »

umvi wrote: post #81
blakesterz wrote: post #4

"Dutch Roll is a coupled out of phase movement of the aircraft as result of weakened directional stability (provided by the vertical tail and rudder), in which the aircraft oscillates around its vertical as well as longitudinal axis (coupled yaw and roll)." That sounds pretty scary. I wonder why it wasn't bigger news when it happened last month?

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…

The Fairchild AFB crash was not a barrel roll.

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#138

Post by rvnx »

FabHK wrote: post #122
exabrial wrote: post #107

What the news about Boeing has done is make me pay more attention to commercial aviation in general. The number of aviation incidents is actually pretty crazy, and no, Boeing is not at the center of them despite what the media would have you believe. What is amazing though is the actual injury and fatality rate is really low due to well trained crews and measured responses by air controllers.

> the actual injury and fatality rate is really low due to well trained crews and measured responses by air controllers. It’s the crew and ATC staff, definitely, but also - the amazingly well engineered airplanes (despite recent Boeing hiccups - just goes to demonstrate the high standards) with many redundancies; - the archaic, but robust ATC system; and - last but not least the excellent safety culture, which invest…

Boeing could still argue "you see, it's safe, redundant systems worked, we haven't killed anyone this time"

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#139

Post by nabla9 »

senordevnyc wrote: post #52
belter wrote: post #21

Earlier quoted context omitted.

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.

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.

Re: Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll

#140

Post by bigstrat2003 »

Waterluvian wrote: post #50
marcus0x62 wrote: post #24

Years ago, my father in law ( a heavy jet mechanic) got sent to China for two months as part of a team to diagnose and fix a recurring dutch roll complaint on a particular airframe. This was for a A300-series flown by a large freight carrier. The local mechanics couldn’t figure it out, so this team was assembled from the mechanics at headquarters to fix the plane. They inspected the plane and found no damage. They ha…

Eek… I’d never want to fly a plane that’s beneath me. I’d prefer it to be at the same altitude.

Technically any plane should be beneath you. Also above you, but beneath you too.
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