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"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
by blakesterz 2y ago
"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?
- deleted 2y ago[deleted]
- jamesholden 2y ago[flagged]
- kcplate 2y agoI know the humorless HN is downvoting you but I gave you an upvote. Farts and fart jokes are always funny.
- doctor_eval 2y agoIt’s being downvoted because it’s technically incorrect. They are describing a Dutch Oven.
- kcplate 2y agoUh yes, they were being sarcastic. Once again…the humorless HN strikes. Sheesh.
- cwillu 2y agoIf 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.
- kcplate 2y agoMy 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.
- doctor_eval 2y agoYou 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.
- namaria 2y agoIs an unfunny joke worth making? Aren't downvotes people telling you they don't find the joke funny?
- drcongo 2y agoI wonder if the name is related to the Dutch Tilt camera shot - https://en.wikipedia.org/wiki/Dutch_angle https://en.wikipedia.org/wiki/Dutch_angle
- SonicScrub 2y agoTha name is believed to be borrowed from an ice skating term: https://en.m.wikipedia.org/wiki/Dutch_roll https://en.m.wikipedia.org/wiki/Dutch_roll https://www.iceskatesmuseum.com/e-disc-schoon.htm https://www.iceskatesmuseum.com/e-disc-schoon.htm
- tjpnz 2y agoHere's a video demonstrating it: https://youtu.be/Zmjam1evDD4 https://youtu.be/Zmjam1evDD4
- kcplate 2y agoI guess it’s worse than it looks? The video was kind of a dramatic let down to be honest. I preferred the mystery.
- FrustratedMonky 2y agoYeah, 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.
- belter 2y agoThe 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.
- HPsquared 2y agoStandby PCU sounds like a control system. Was that a cause or effect of the event?
- banannaise 2y agoThe 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 https://en.wikipedia.org/wiki/Boeing_737_rudder_issues
- HPsquared 2y ago
- belter 2y agoIt can torn off the engines from the main body structure: https://asn.flightsafety.org/asndb/333926 https://asn.flightsafety.org/asndb/333926
- senordevnyc 2y agoWhile 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.
- jtdev 2y ago[dead]
- FabHK 2y ago> dutch rolls were being performed intentionally for demonstration purposes. …with the yaw dampers (that are there to prevent Dutch roll) turned off.
- nabla9 2y ago1985 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.
- sjm-lbm 2y ago> 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.
- rootusrootus 2y agoOf 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.
- underseacables 2y agoIt may have gotten lost in a sea of Boeing bad news.
- adolph 2y ago> 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?”
- FabHK 2y agoThere 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.
- adolph 2y agoAgreed. 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?
- Kye 2y agoIn plain English: unwanted tail waggle
- SahAssar 2y ago"Tail lefty-righty no-no" is the industry term.
- Kye 2y agoThat's plane English.
- addandsubtract 2y agoYou're on a roll
- umvi 2y agoNot 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)...
- rob74 2y agoAFAIK only one Boeing passenger jet ever performed a barrel roll (without passengers on board): https://simpleflying.com/boeing-707-barrel-roll-seattle/ https://simpleflying.com/boeing-707-barrel-roll-seattle/
- wyldfire 2y ago> 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.
- MeImCounting 2y agoYou dont lose lift in a barrel roll, you merely change the direction that lift is being generated.
- throwup238 2y agoThat 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.
- brandall10 2y agoJust 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.
- ttymck 2y agoDo you fly to Mexico city often? The altitude makes landings unusually eventful.
- brandall10 2y agoThis 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.
- tracker1 2y agoI 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.
- dylan604 2y ago> 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 https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191
- rob74 2y agoThe question is how bad the oscillations were, and how long they lasted. Maybe for the passengers it was indistinguishable from "regular" turbulence?
- semireg 2y agoE.g. wibble-wobble or the more pronounced wibbly-wobbly.