Southwest Airlines Boeing 737-8 Max Experienced Dutch Roll • Hacker News Board

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

#101

Post by ttymck » Thu, Jun 13, 2024, 1:27 PM UTC

brandall10 wrote: post #92

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?

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 b…

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

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

#102

Post by tekla » Thu, Jun 13, 2024, 1:28 PM UTC

I'm going to to laugh at the bad takes on this thread, and await a more accurate report.

Dutch roll is undesirable, but its a basic consequence of some converging aeronautical effects.

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

#103

Post by rob74 » Thu, Jun 13, 2024, 1:28 PM UTC

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…

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

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

#104

Post by FabHK » Thu, Jun 13, 2024, 1:29 PM UTC

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.

> dutch rolls were being performed intentionally for demonstration purposes.

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

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

#105

Post by marcus0x62 » Thu, Jun 13, 2024, 1:30 PM UTC

ToucanLoucan wrote: post #100

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…

> and really high quality counterfeit Fluke multimeters he got from the local market, though. I got one of those years ago. Wouldn't trust it on any industrial shit but I've used it for residential electrical tinkering (plus smaller projects) for years, works great and has never had a single issue.

These were used for mechanic-y stuff like basic voltage and circuit draw tests. They were fine for that, and the main benefit was that they were made with oil/solvent resistant coatings on the meter body and leads.

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

#106

Post by SahAssar » Thu, Jun 13, 2024, 1:30 PM UTC

Kye wrote: post #64

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?

In plain English: unwanted tail waggle

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

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

#107

Post by exabrial » Thu, Jun 13, 2024, 1:30 PM UTC

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.

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

#108

Post by rollulus » Thu, Jun 13, 2024, 1:31 PM UTC

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.

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

#109

Post by geekfactor » Thu, Jun 13, 2024, 1:32 PM UTC

I didn't know what it was called, but I've experienced mild Dutch Roll enough on flights, usually on the approach or landing, that I didn't realize that it was all that rare or dangerous. I had come to think of it as a normal result of wind shear. I imagine it's a matter of degree, and I wish there was some mention of the magnitude of the Dutch Roll in this case vs what is considered normal or acceptable.

(Edited to qualify my experience as "mild".)

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

#110

Post by krisoft » Thu, Jun 13, 2024, 1:32 PM UTC

somenameforme wrote: post #93

bradleyjg wrote: post #53

Earlier quoted context omitted.

Do you think your car (or bike) is safer or more dangerous than the least safe Boeing plane in service?

These numbers are always pretty BSy because the big dangers in flight are take-off and landing. Comparing distances just completely obfuscates everything for no real gain. You can illustrate this clearly with some sort of reductio ad absurdum. Imagine we have an interstellar ship traveling many trillions of miles, but that blows up 90% of the time. If you look at it in terms of this same deaths/mile metric it'd still…

Okay. So let's compare accidents per flights to accidents per trip with bike/car.

IATA reports 1.19 accidents per million flights in the 2019-2023 years. [1] Your turn to find a comparable number for road vehicles.

1: https://www.iata.org/en/pressroom/2024-releases/2024-02-28-0...