Posted on 07/10/2024 11:07:09 AM PDT by Red Badger
A Southwest Airlines jet that experienced “Dutch roll” while flying at 34,000 feet had undergone routine maintenance before being parked outside during a strong storm, after which pilots noticed unusual movements of the plane‘s rudder pedals.
Following the incident in May, Southwest Boeing mechanics found “substantial” damage to the plane’s tail, where the rudder is located.
However, the National Transportation Safety Board said it had not determined when the damage occurred.
According to data from Flightradar24.com, the Boeing 737 Max was grounded for more than a month before resuming flights last week.
“Dutch roll” is a swaying, rhythmic combination of yaw, the tail sliding sideways, and the wingtips moving up and down.
The Southwest jet suffered dangerous movement while flying at 34,000 feet and then again when descending to 32,000 feet while flying from Phoenix to Oakland, California.
While the condition can be dangerous, modern planes now have a “yaw damper” to stop the oscillation, which causes the Dutch roll.
After the planes landed, airline mechanics discovered fractures in the metal bracket and ribs, which hold a backup power control unit to the rudder system.
Investigators last week examined the damaged parts in Ogden, Utah.
The plane was parked overnight at the New Orleans airport on May 16 during thunderstorms and heavy rain.
The plane underwent scheduled maintenance on May 23 before pilots noticed the rudder pedals moving when the yaw damper was engaged.
The NTSB said that on May 25, pilots felt the pedals moving during the Dutch roll and after landing.
All of the 31 Max jets were inspected by Southwest, but no other cases of damage were found around the rudder power units, NTSB said.
The most recent Boeing incident was reported last month, when a Korean Air Boeing 737 Max 8 experienced a sudden emergency plummeting 26,900 feet before making multiple erratic loops before stabilizing.
Fifteen passengers suffered injuries ranging from severe hyperventilation and eardrum pain, according to the Ministry of Land, Infrastructure and Transport.
With tens of thousands of commercial airline flights daily, there are occasional ‘flight incidents’. Only the ones on Boeing aircraft receive national news headlines.
If that's true - and it might be - why would that be happening?
Do you mean the pitot tube?
No, it's been used on car jackers before. Woman almost killed a guy.
No, I meant the Angle of Attack probe. AOA info went into the CADC which drove the altimeters and they'd go crazy if the AOA probe became corroded due to the high moisture content. And the CADC had outputs to the Autopilot System, though I don't know exactly what kinds of outputs and what the Autopilot system did with it/them.
The pitot tube mainly drove the Airspeed/Mach indicator, but it must have gone to the CADC as well. (It's been 50 years.) The problems that I remember with the pitot tube is that the heater would fail, and the tube would ice over and the airspeed indication would drop to zero. It was hard to fix in that it was hard to get enough heat to it for a good solder joint. We had a humongous soldering iron but the tube was maybe 12-15 feet above the ground and it was "always" cold and windy in England.
There was also a rudder-feel switch which would make the rudder pedals much harder to push above (I think) about 130 knots. This drove the hydraulics that drove the rudder, so in that problem with the airliner that might be something to look at as well.
All of stuff is much more complexly integrated in a modern system vs. the F-4D which was designed in the late 1950s. Because of this, the bottom line for me is to not overlook these sensor which at first glance don't seem to have possibly been the problem.
One more thing. We had a problem where the Attitude Indicator would suddenly show the aircraft at a 30-degree bank, even if it was flying straight and level or even sitting on the ground. We eventually traced that to a broken pin in the bombing TIMER connector, a part of the "Abba-Jabba-7" bombing system.
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