Posted on 06/17/2024 3:27:05 PM PDT by mabarker1
Blame the Flight Crew is always put in the mix to have a scapegoat.
The PCU Valve was redesigned but who’s to say that a box of old inventory got found in the parts room and the current Parts Crew/Assembly Line Crews may not even know about the original problem.
Gotta wait and see.
I’m old enough to have worked on CNC machine tools with hydraulic servos. In the computer, the motion axis would have a position feedback register, and the program a command register. The difference between them generated a command signal to the servo valve. But if the difference exceeded some predetermined value, a separate valve would close, locking the axis wherever it was. This prevented axis runaways due to a malfunctioning servo valve. I’d want to think that the 737 rudder servo hydraulics would have some analog to that, to prevent the rudder going hard over un-commanded.
One would think that they would create a secondary independent Rudder control system. If nothing else it could have a Hydraulic Line lock that would close 2 valves (feed and return) with a pressure vent to release the pressure on the isolated PCU Rudder valve. Then they could revert to a secondary cable control system to still allow complete control of the Rudder. I’m pretty sure it won’t be easy to move the Rudder with cable only control but maybe they could add a gearbox to amplify the backup cable system that would be better.
A Boeing 737 sustained tail damage in midair last month in an incident that aviation experts say is rare for commercial flights.
On May 25, Southwest Airlines Flight N8825Q, a Boeing 737 Max experienced what is known as a “Dutch roll” — where the aircraft tail wags back and forth as the wings rock in see-saw fashion, according to NBC.
This was another in a string of recent incidents involving Boeing planes that began in January when a door blew off of a 737 jet. Since that time, Boeing’s production process has come under investigation.
The Phoenix to Oakland flight had 175 passengers and six members of the crew aboard. The plane was initially reported to be at 38,000 feet at the time of the incident, but a National Transportation Safety Board investigation showed it was at 34,000 feet.
The plane landed safely with no injuries reported.
An FAA report said the aircraft “experienced a Dutch roll, regained control and post flight inspection revealed the damage to the standby PCU,”referring to the rudder’s power control unit.
The FAA later noted that damage to the tail was “substantial,” according to USA Today.
“Having a Dutch roll event is unusual,” John Cox, an instructor at the University of Southern California and CEO of the consulting firm Safety Operating Systems, told The Washington Post.
“Having one that caused damage is unheard of,” he said.
“Any uncommanded flight control movement is potentially significant. The fact that this resulted in significant damage makes this sort of a big deal,” Sumwalt told CBS senior transportation and national correspondent Kris Van Cleave in an email.
In its reporting, USA Today wrote that “Dutch rolls are fairly rare in commercial aviation.”
“The movement can stress the airplane fuselage and cause damage as it did in the Southwest incident. Dutch roll incidents have previously caused planes to break apart inflight,” it reported.
Tracking data from FlightAware indicates the jet was flown to Boeing’s plant in Everett, Washington, on June 6.
The NTSB report on the incident is due later this month, according to USA Today.
“The NTSB’s Vehicle Recorder Laboratory in Washington has received data downloaded from the airplane’s digital flight data recorder. Data from the recorder will aid investigators in determining the length and severity of the event,” the NTSB said.
“The cockpit voice recorder, which is currently limited to two hours of audio, was overwritten and unavailable to investigators. A preliminary report is expected within 30 days of the date of the event,” the NTSB said.
Boeing 707 roll by Test Pilot Tex Johnson
Nice short video from yesteryear. Worth a watch.
https://youtu.be/Ra_khhzuFlE?si=etkLBPY3LcBnNcvU
Does anything have cables at all anymore?
Interestinger and interestinger, said Alice. Did the damage cause the event, or verse vicea?
Oldie but a Goodie.
That is what the Yaw damper is and does. Already created..
The reason the recovery procedure calls for feet on the floor is the pilot input could over stress the vertical stabilizer.
So, the procedure uses the spoilers to slow the forward movement of the wing.(Drag)
Using the attitude indicator, the SLIGHT input is used to slow the rising wing because that is the wing that is moving forward, creating, when the other does the same thing, “dutch roll..”
“intentional” ... “sabotage”
I don’t often agree with either of you ...
On this, I’m 100% in agreement.
When people with wildly differing viewpoints all smell a rat ...
The Peoples' Republic of China would just LOVE to get in on the international airliner sales business. Currently, it's dominated by Boeing and Airbus.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.