To disengage, you are correct, but to disable it is to pull the breakers. Using the trim buttons will disengage it temporarily as well. In any case, they should all know that pulling the breakers will disable the electric trim.

Just to clarify, there is no "pulling a breaker" here. This isn't a 707, lol. :p

As mentioned previously, there are 2 stab. trim switches on the center pedestal. Flipping those down to "cut-out" completely disables all auto trim. Been that way (and in that location) for several generations now.

Visual aid:

http://forums.pelicanparts.com/uploa...1552679145.jpg

I violated my own rule of accident investigations!

Thanks for the visual.

Sorry, my bad on that.

I read that radar data showed the plane accelerating to very unusual speed during the flight. What's that about?

Added to that question is why radar data showed it to be airborne at 93 kn ground speed. I have no idea what the wind speed and direction were but that’s an astonishingly low speed, especially at the airport elevation.

It makes me wonder if they had a faulty airspeed indication, I think that was a problem on the Lion Air flight.

Edit: There’s no way I’m reading that chart correctly. It couldn’t have been airborne at 93 knots, that quickly. Maybe that airport runway has a hell of a hump in it...

200 hours total?

as in flight time?

as in not very much more than necessary to solo a Cessna 172?

It's a function of where the thrust line is in relation to the pitch axis. You can see that on virtually all commercial jets, the engines are the lowest thing under the airplane when in flight. They are well below the pitch axis, so thrust will make the airplane pitch up. Pilots just adjust trim for the long haul to maintain level flight, or give it some down stick if its temporarily pitching up more than desired. Software takes care of that today.

Speaking of software, it may be as easy as downloading the fix from Boeing's My Boeing Fleet customer service website. That can be done right there in the cockpit. Technology can be so cool...

If the fix requires any hardware changes, it could take awhile to implement. Some avionics components are about a five minute swap, "plug and play" with a big ass multi-pin connector on them, just like your car. With some components, you're done right there. Others need calibration to their various input sources, or with other components.

I don't think these particular components, if some indeed need to be replaced to accept the new software, will be all that easy. These communicate with the "where am I and what am I doing" external and internal sensors. These would include the AOA sensors we have already discussed, plus the airspeed indicators (these are the little pitot tubes seen in the photos right next to the AOA sensor), altitude sensors, nav gyros, and that sort of stuff. This all requires calibration and verification.

That calibration was one my jobs on site. I was responsible for those tasks as the Tooling and Equipment Engineer. Not just performing those tasks on site, but designing the equipment with which we performed those tasks. Any time we worked on the airplane in such a way as to have disturbed the nav gyros, the AOA sensors, etc. we had to re-calibrate those components. Think about it - what is "straight ahead"? What is "level" (both pitch and roll)? How do you "tell" the airplane all of that? What is your baseline for measurement?

Seat tracks. They do far more than just hold seats (and lavs and galleys) - they serve as the "zero" for yaw, pitch, and roll. These are some of the most carefully aligned components in the airplane, but not because we mount seats to them - we mount a lot of our alignment equipment to them. In this case, the very equipment that tells the aircraft what "straight and level" is.

Here is a quick high level overview of just one of our alignment procedures. This is for the nav gyros. We start by mounting an electronic gyro (of my design) to the seat tracks on the centerline of the aircraft, somewhere near where the front or rear main spars of the wing would meet (if they actually extended all the way to the center of the fuselage - they don't). We mount targets both forward and outboard of the gyro, in the seat tracks. Kind of like surveyors' targets. We then use lasers to align the gyro housing to those targets. Once physically aligned, we then turn on the gyro and let it find "straight and level".

Once aligned, we dismount it from its housing, quick scurry out the door and down the stairs, and head for the forward EE (electrical equipment) rack, located up by and accessed through the nose gear wheel well. The gyro is electronically "spinning" this whole while, and the clock is ticking. We only have so much time before it starts to "drift", so we have to work fast.

Once in the forward EE bay, we mount our gyro to a shelf that will be mounted on the EE rack. This shelf is loose - it is not yet hard mounted to the rack. Once the gyro is mounted to it, we can begin aligning this shelf to the rack. Once the gyro tells us that shelf is "straight and level", we hard mount the shelf to the rack and remove the gyro. This shelf will then hold the nav gyros.

AOA sensors are easier. We align these optically all from the outside of the aircraft. Hopefully you guys kind of get the idea, though. If it's not just software, depending on which hardware, it could mean a fair amount of fiddly-dicking around, which would lead to delays.

So, hopefully, it's just software. :D

Just about shot Merlot through my nose! lol!

So the Seattle Times has an article about Boeing's cozy relationship with the FAA and 737's flawed certification process (link) .

I was thinking about the crash last night and as flawed as the MCAS implementation appears to be, I have to agree with their statements in the article

With all the focus on control issues with the Lion Air flight, I can't believe the Ethiopian Air pilots did recognized the issue and at least disable MCAS. These are supposed to be trained professionals, or maybe they were just professionals. But if I were a 737Max pilot, after the Lion Air crash, I certainly would have familiarized myself with the process. Boeing certainly appears culpable, but poor piloting, at this point, appears to be the cause of the crash.

I am fairly certain that the pilots will get their fair share of the blame for this. It's hard to not notice the trim wheels spinning away next to your knee. If nothing else, they should have seen that.

Poor training is almost certainly going to be an issue too, but that captain needed someone in the right seat with more than 200 hours. That's on the airline.

From the article.
Thank you for posting the article, the 737 Max still seems like a pit-bull that can turn on it's owner/operator at any moment. As with pit-bulls, proper training seems to be essential.

I disagree. If a pilot sees and hears the trim wheels spinning and he hasn't activated the trim switch, he should recognize he has a problem. Never mind what caused the trim wheels to spin, the fix is the same.

It's not hard to notice them.

https://youtu.be/ULCrAZyNk34

A useful summary of what's transpired:

Crash: Ethiopian B38M near Bishoftu on Mar 10th 2019, impacted terrain after departure

FWIW:

http://files.abovetopsecret.com/file...vz5c8c0001.jpg

That's weird. I caught part of a show over the weekend with some scary similarities.

the show is called air disasters on the Smithsonian channel. Pretty good show.
https://www.imdb.com/title/tt9838136/?ref_=ttep_ep_cur

It described several incidents involving airbusses where the altitude reading was confused with the AOA reading and caused the controls to go 10 degrees down instantly.
Note that the passengers did not go 10 degrees down, they went up into the ceiling. Lots of serious injuries.
the same thing happened on a few other identical planes, almost all off the west coast of Afrika.

They never did figure out why the hardware mislabeled the altitude readings as AOA readings, but they wrote a software fix to prevent the plane from over-reacting.

IIRC they didn't pull breakers either ;)

And before you go sayin' i don't know nuthin about the subject, I sat right seat in a Citation business jet once. I remember it because he kept telling me not to touch ANYTHING.



http://forums.pelicanparts.com/uploa...1552939158.gif

And that's another thing: why do people take off their seat belts on a plane?

I never do that unless my bladder is bursting.
if I'm not heading to the lav or on the way back, I'm always belted in.

But apparently others do not do that and tend to get hurt by turbulence. Prolly the same people who get runned over by trains.

I’m not so sure, there was zero training on the system, no override, and no manual on it available to crews according to what I read.

Grand jury has started looking at the certification process. I recall (un)fondly what it was like to receive a grand jury subpoena at Boeing. Sends everyone into ass-covering mode.

Actually, I think it is described in the manual. There are not very many simulators for the Max 8 yet, but...

I’m fairly certain that a competent pilot would recognize the fact that the stabilizer trim is being manipulated without pilot input. That is something that they do train for, it really doesn’t matter why the stabilizer is moving uncommanded. The fix is the same and it’s been that way for 50 years.

I don’t mean any disrespect to the pilots that crashed these two jets but I truly believe that that would not of happened with the frontline pilots we have here in this country.