"Dutch roll"
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Simon Hradecky, "Accident: Southwest B38M enroute on May 25th 2024, Dutch Roll", The Aviation Herald 6/13/2024:
A Southwest Airlines Boeing 737-8 MAX, registration N8825Q performing flight WN-746 from Phoenix,AZ to Oakland,CA (USA) with 175 passengers and 6 crew, was enroute at FL320 when the aircraft experienced Dutch Roll. The crew was able to regain control and landed the aircraft on Oakland's runway 30 about 55 minutes later. The aircraft sustained substantial structural damage.
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.
The aircraft remained on the ground in Oakland until Jun 6th 2024, then positioned to Everett,WA (USA), ATS facilities, and is still on the ground in Everett 6 days later.
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).
The PCU is the power control unit, an actuator controlling the (vertical) rudder.
On Jun 13th 2024 The Aviation Herald learned that two ribs, that the stand by PCU is being mounted to, were damaged as well as the mounts of the stand by actuator. A temporary repair was done in Oakland replacing the damaged PCU, the aircraft was then ferried to Everett to replace the damaged ribs.
This being Language Log rather than Aviation Safety Log, I wondered what's Dutch about the "Dutch roll", and how the name originated? The Wikipedia article is helpful — at least to the extent of citing an analogy to ice skating terminology:
The origin of the name Dutch roll is uncertain. However, it is likely that this term, describing a lateral asymmetric motion of an airplane, was borrowed from a reference to similar-appearing motion in ice skating. In 1916, aeronautical engineer Jerome C. Hunsaker published: "Dutch roll – the third element in the [lateral] motion [of an airplane] is a yawing to the right and left, combined with rolling. The motion is oscillatory of period for 7 to 12 seconds, which may or may not be damped. The analogy to 'Dutch Roll' or 'Outer Edge' in ice skating is obvious." In 1916, Dutch Roll was the term used for skating repetitively to right and left (by analogy to the motion described for the aircraft) on the outer edge of one's skates. By 1916, the term had been imported from skating to aeronautical engineering, perhaps by Hunsaker himself. 1916 was only five years after G. H. Bryan did the first mathematical analysis of lateral motion of aircraft in 1911.
The article links to Hunsaker's 1916 paper, which doesn't help me much, since my (childhood) exposure to ice skating was entirely via trial-and-error on a local pond, with equally naive friends:
Here's a YouTube video illustrating (one version of) the Dutch Roll in skating:
The accompanying text is historically and culturally informative, but doesn't help me much with the aircraft analogy:
The original Dutch roll on ice skates. This classic style is meant for skating long tours over the frozen Dutch canals with little effort. It originates from Holland and (West-)Friesland and is well described by Claes Arisz Caescoper (1650-1729) from Zaandijk; next to the windmills of De Zaanse Schans, north of Amsterdam.
The Dutch roll can be performed single, as well as in pairs and groups. In pairs and groups special sticks can be used for support. Every strike with the special classic skates should make an 'S' form. Starting from the outer edge of the blade, changing to the inner edge. The body is to be kept straight and hanging over to replace the forward kick.
The most valued Dutch roll is called in Dutch 'schoonrijden'. The other Dutch word 'zwieren' fits to skating with long strikes, but only on the outer edge of the blade.
The couple showes one of the techniques by skating behind eachother, righthand in righthand on the hips of the first skater (usually the woman/shortest). Other techniques for pairs are skating righthand in lefthand on shoulder level or left hand in lefthand on chest level (of the left skater) and righthand in righthand behind the hips (of the right skater).
This couple belongs to the ten best existing nowadays. They skated on the indoor icerink of Enschede in a championship organised by the local 'Twentse Schoonrijders' in cooperation with the Dutch Roll section LSV within the national skaters federation KNSB d.d. 25 november 2010.
And this video offers a detailed analysis (which they call a "simplified explanation") of the "dutch roll" in aviation, without mentioning ice skating:
Philip Taylor said,
June 14, 2024 @ 5:44 am
Some seriously weird English at "The Aviation Herald learned that two ribs, that the stand by PCU is being mounted to, were damaged" — would that not be more commonly expressed as "The Aviation Herald learned that [the] two ribs to which the standby PCU is mounted were damaged" where "[the]" indicates my ignorance as to whether there are only two ribs in this area.
J.W. Brewer said,
June 14, 2024 @ 7:55 am
What's interesting is that in the aviation context a "Dutch roll" sounds like something you want to avoid and wouldn't do on purpose with your airplane, and thus appears to fit the extensive pattern of NP's of the form "Dutch X" in English being vaguely pejorative. Except that the phrase is apparently descriptive and not pejorative in the ice-skating context from which it was taken, i.e. deliberately using the "Dutch roll" may be an entirely sensible-to-optimal strategy for a skater in a given context.
Adrian Bailey said,
June 14, 2024 @ 8:17 am
Philip Taylor: Some seriously weird English at "The Aviation Herald learned that two ribs, that the stand by PCU is being mounted to, were damaged" — would that not be more commonly expressed as "The Aviation Herald learned that [the] two ribs to which the standby PCU is mounted were damaged" where "[the]" indicates my ignorance as to whether there are only two ribs in this area.
I think the report uses the most "commonly expressed" form (if we remove the "being" which appears to be a flub). That's how people speak. "Which (or that) …… to" is much more common than " to which …" But the second "that" in the text isn't very elegant.
In writing, I'd prefer: "The Aviation Herald learned that there was damage to two ribs which the standby PCU is mounted to."
Philip Taylor said,
June 14, 2024 @ 8:21 am
I would suggest that neither a Dutch cap nor a Dutch auction have pejorative associations.
Cervantes said,
June 14, 2024 @ 8:32 am
I don't know that "Dutch" is necessarily pejorative, but it often is. I cribbed this from Wikipedia, it doesn't give the direct link to the OED discussion but maybe someone can track it down.
"The Oxford English Dictionary connects "go Dutch" / "Dutch treat" to other phrases which have "an opprobrious or derisive application, largely due to the rivalry and enmity between the English and Dutch in the 17th century", the period of the Anglo-Dutch Wars. Another example is "Dutch courage".[1] A term bearing some similarities is Dutch oven. "
J.W. Brewer said,
June 14, 2024 @ 9:08 am
Yeah, the pejorative overtone of "Dutch" is a tendency not an invariant rule. If you look at 19th-century dictionaries of slang, they tend to regard "Dutch auction" as pejorative, although that overtone may have faded as more economically-sophisticated users of the phrase have come to appreciate why it is in fact a perfectly sensible approach to take in certain sorts of commercial contexts rather than being a perverse inversion of a traditional auction just for the sake of being perverse.
Lazar said,
June 14, 2024 @ 9:23 am
In film, Dutch angles can be effective if used with skill but are often considered hacky/schlocky.
Alyssa said,
June 14, 2024 @ 9:26 am
What I find amusing is that this term implies there was a time when it was simply expected that an aeronautical engineer would be familiar with figure skating. I don't imagine those two demographics have much overlap these days.
M.G. Lewis said,
June 14, 2024 @ 9:43 am
I noticed the use of "positioned to" in the third paragraph:
"The aircraft remained on the ground in Oakland until Jun 6th 2024, then positioned to Everett,WA (USA), ATS facilities, and is still on the ground in Everett 6 days later."
I've never seen this usage before? Why wouldn't they say "moved to"?
And in the last paragraph, the action is described as "ferried to"
"the aircraft was then ferried to Everett to replace the damaged ribs."
Does "positioned to" have a more specific meaning in aviation than "moved to"?
Y said,
June 14, 2024 @ 10:09 am
My first thought when reading the headline was this:
https://www.sfgate.com/food/article/dutch-crunch-bread-17635355.php
I hadn't realized until now that the Dutch Crunch roll was local to San Francisco.
Gregory Kusnick said,
June 14, 2024 @ 10:19 am
"The aircraft […] positioned to Everett" calls to mind last month's discussion of "cooperate him", though in this case the technical jargon takes it from transitive ("Southwest positioned the aircraft") to intransitive ("the aircraft positioned [itself]").
Stefan Reimers said,
June 14, 2024 @ 12:32 pm
In "Airline Speak", people differentiate flights that take place to make money from those that don't. Regular flights transport passengers and/or cargo and while doing so the aircraft and its crew end up somewhere else as well. Usually no problem, people tend to travel somewhere and return later, thus the aircraft is filled both ways.
At the beginning of an event (Olympics) you might find more people travelling in one direction over the return, aid being brought in to help victims of a catastrophe and similar are examples of situations in which a very unidirectional demand occurs. Thus, in the other direction you'll see aircraft being positioned (or ferried) for the sake of the aircraft being in another place rather than paying passengers or cargo.
Alyssa said,
June 14, 2024 @ 12:50 pm
@Stefan Reimers
That's a great explanation, thank you!
Philip Taylor said,
June 14, 2024 @ 1:08 pm
Stefan — in "the aircraft was then ferried to Everett to replace the damaged ribs" — does the "ferried" imply "using a means of propulsion other than its own engines", or can an aircraft ferry itself ? The passive voice of "was then ferried" very much suggests the former interpretation to me, but reality suggests that this interpretation is factually unlikely.
Chas Belov said,
June 14, 2024 @ 1:35 pm
@Y: I too immediately thought of Dutch Crunch bread (which I happen to love). Yes, a San Francisco Bay Area treat.
I was surprised to see the phrase in an official government document. That implies both that it's an accepted technical term in aviation and that the occurrence is common enough to have a term. And, by the fact of its Wikipedia entry, that does indeed seem to be the case.
I was previously unaware of either the aviation or figure skating. Odd that the Wikipedia article doesn't refer to the figure skating version, although I wonder how one would find a Wikipedia-sufficient reference to verify that this was the direction the etymology took.
Brett said,
June 14, 2024 @ 1:37 pm
Dutch oven, Dutch door, Dutch courage, Dutch treat, and originally Dutch auction all involve the implication of being small, cheap, and/or unworthy of the names—not a real oven, not real courage, not really treating.
david said,
June 14, 2024 @ 1:42 pm
A “Dutch Roll” is known in the Netherlands as a "Stroopwaffel".
Chas Belov said,
June 14, 2024 @ 1:46 pm
Um, that's what I get for not reading. The Wikipedia article on the avaition Dutch roll does indeed mention the figure skating origin. But apparently the skating version isn't considered notable enough for its own Wikipedia article.
Gregory Kusnick said,
June 14, 2024 @ 2:13 pm
While living in Seattle I did occasionally see aircraft fuselages (sans wings) being moved by flatbed rail car from one Boeing facility to another. (But of course that's not what's being referred to here.)
Viseguy said,
June 14, 2024 @ 4:23 pm
This is all news to me, with respect to both ice-skating and aviation. But I think the aptness of the analogy with the ice-skating movement argues against any pejorative connotation in the aviation usage. Not to mention that the movement of the aircraft so described is clearly a genuine "roll", as opposed to "oven", "courage", "treat", etc.
In any event, I'm grateful that if I ever experience a coupled out-of-phase movement of an aircraft as result of weakened directional stability, I'll know what to call it. Unless, that is, the phony titanium does me in first.
KeithB said,
June 14, 2024 @ 5:21 pm
Lazar:
i.e., Star Wars [effective] vs Battlefield Earth [way schlocky]
cameron said,
June 14, 2024 @ 6:07 pm
while there's no English wikipedia page for the skating sense of "Dutch roll", there is a page in Nederlands: https://nl.wikipedia.org/wiki/Schoonrijden
David P said,
June 14, 2024 @ 6:49 pm
On "ferrying": my father (World War II bomber pilot) spent some time after the war's end ferrying planes back from the Pacific islands to the United States, meaning piloting the planes back without passengers or cargo. That was the word he used, and it seems to be standard in that context. I notice that my old Oxford English Dictionary lists that meaning of the verb (taking from one place to another) as obsolete.
The same operation for buses — shifting them between terminals without passengers — I have heard referred to as "deadheading."
Narmitaj said,
June 15, 2024 @ 3:51 am
Ferry flying has its own Wikipedia article
https://en.wikipedia.org/wiki/Ferry_flying
"A Ferry flight, also known as a fairy flight or a positioning flight is the flying of aircraft for the purpose of returning the aircraft to base, delivering it to a customer, moving it from one base of operations to another, or moving it to or from a maintenance facility that includes maintenance, repair, and operations.
"A commercial airliner may need to be moved from one airport to another to satisfy the next day's timetable or facilitate routine maintenance. This is commonly known as a positioning flight or repositioning flight".
Ferry flying is big in wartime. In the UK in WW2 the Air Transport Auxiliary (10% of whose pilots were women) "ferried new, repaired and damaged military aircraft between factories, assembly plants, transatlantic delivery points, maintenance units (MUs), scrapyards, and active service squadrons and airfields".
Narmitaj said,
June 15, 2024 @ 4:16 am
On Dutch angles, the Wikipedia article on them says Dutch "was historically a synonym of "German". The shot acquired its name due to its popularity in silent-era German films".
I also read somewhere, ages ago, in a book by film writer Ian Christie on Terry Gilliam, that Gilliam suggested the angle came about because narrow Dutch canal-side houses lean forward to facilitate the transport of furniture and goods to upper floors. The buildings being so narrow that the narrow staircases are largely useless, stuff is carted via rope and pulley hooked to a cantilevered beam sticking out of the top of the frontage; the lean helps prevent cargo scraping the wall (even if all this isn't true, sites online claim it is). Gilliam's theory, if I remember this right, was that images of Dutch canalside buildings filmed straight and level looked wrong, so the camera was Dutch-angled to make the houses look correctly vertical. Most likely he, or someone else, was having a mischievous jape.
To follow up my ferry comment without making a third comment, crew members can also be positioned as well as aircraft. The idea is to get the plane or crew in the right position to make the next scheduled revenue-earning flight. (A ferry flight is more general – getting an aircraft from the manufacturer to the squadron where it will then live out its career, for example.)
Philip Taylor said,
June 15, 2024 @ 4:33 am
I earlier wrote
but I now realise, with the benefit of a good night's sleep, that an aircraft could not possibly ferry itself, so the passive voice was mandatory in the absence of an explicit agent.
Tim Roee said,
June 15, 2024 @ 6:08 am
@chas belov Yes, it's very much a standard term in aviation. It's the normal term for a particular condition pilots need to learn to recognise and recover from.
BZ said,
June 17, 2024 @ 11:06 am
Doesn't "going Dutch" also refer to German practice and not Dutch as we understand it today?