737 Max

Expect to hear some preliminary info this morning, or at least that's mentioned by Bloomberg radio a few minutes ago. A suggestion that there may have been a mechanical issue with one of the jackscrews.

Notice that the frontal shape of the engines of the 737 MAX compared with the older 737's I am used to flying on.
 
I don't fly however I have been told a few stories in my time. The most relevant one was from the 1980s when I used to fix band gear. The band traveled to a gig in a much smaller aircraft on a route that took them across the English channel. On the way back they made a stop on the south coast of England. During there approach the the spring that defaults the yoke to level flight snapped so that the pilot had to man handle it over the cliffs and into the coastal airfield. They managed to get the owner of the aircraft to hire a replacement plane for them to continue. A soccer player was lost a couple of months ago in the English channel in an accident involving a similar small aircraft. Larger planes have something a bit closer to the power steering on a car and later large planes have an electronic system coupled with the hydraulic system controlled by an increasing number of sensors. I would guess that some kind of sensor test will needed as part of the pre-flight check so that protective covers placed over sensors during cleaning of the aircraft do not get forgotten. I once had a problem with a ground based device with a sensor line that mysteriously got blocked up over a period of a couple of hours. It was an insect nest in the end so if that happened in an African country as opposed to the UK where I had the problem the higher temperature would make the insect work faster. Wooden biplanes used to get eaten by termites in Africa and insects have not gone away or stopped causing technical problems. Some kind of sensor check needs to be done on the taxi way especially in a hot climate.
 

6L6

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LISTEN TO ME VERY CLOSELY...

Yes, essentially ALL modern large aircraft have jackscrews. They are usually electrically driven, but the mechanism itself is a (large) threaded rod connected to the front of the horizontal stabilizer and controls the angle of incidence of the stabilizer.

boeing_737_ng_horizontal_stabilizer_trim_actuator_1a529610f30d47f02f150f3adb614fff457f950b.jpg


737-pitch-control.png
 
The Lion Air crash was ultimately blamed on shoddy maintenance by a second rate charter airline which led to a faulty sensor.
At least that was strongly implied if not the official result.

This doesn't really work for Ethiopian as their practices are widely recognized as impeccable.
These airplanes are so new anyway, I can understand there's a strict regime for maintenance and service checks, but I cannot understand a sealed sensor failing after such short time on a modern aircraft. And even if a sensor failed, should it not be possible to manually control the airplane? The pilots where powerless in their attempts to do anything at all.

However I am also disturbed by the strong worded insistence that the recorders must be analyzed in the US. Luckily they went to Paris for analysis.

Yes, maybe one can hope for a relatively unbiased analysis.
 
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Geez, that Jackscrew trim systems looks about as mechanically complicated as the levers, cams and push rods on the underside other the Dual record changer I'm overhauling. :D

Thanks for the pics. :up:

The mechanics of it are still great for motion control. Archimedes should be proud. :)

Anyways, as 6L6 said so succinctly, I'm all too familiar with how badly my field is reported so I assume that most things are far far more nuanced and complex than can be distilled down in an article written by someone that's probably not a subject matter expert.
 
The problem may run deeper than the MCAS system.

According to Associated Press the two US pilots who reported problems said that the plane went into a steep descent when they switched to autopilot but doing so switches off MCAS.

And according to the Guardian newspaper the flight data recorder of the Ethiopian plane may be damaged to such a degree that it might not yield any useful information.

Meanwhile the Norwegian airline is seeking reimbursement from Boeing for the costs of grounding their Max 8s ie cost of parking the planes plus loss of earnings.

Pilots have reported issues in US with new Boeing jet

Boeing’s 737 Max fleet 'will remain grounded for weeks' | World news | The Guardian