Another brand new 737 Max crashes

[David]

I still can't wrap my mind around how Boeing allowed a non-redundant system on an airplane that had the ability to override a pilot's inputs.

[GH85Carrera]

Originally Posted by David

I still can't wrap my mind around how Boeing allowed a non-redundant system on an airplane that had the ability to override a pilot's inputs.

The Air Force just stopped accepting the new tankers. The Air Force keeps finding tools and other debris in closed panels. Just completely unacceptable to get a new mega million dollar aircraft and part of a huge order, and have junk left behind by the workers. Not the publicity Boeing needs or wants. Well, maybe they do need it. Fire those production crews and hire some that want to do a good job, or move production to a plant that wants top quality production.

[flipper35]

Why do they keep calling it anti-stall technology? From my understanding from both pilots and the manufacturer is that this is more like a force feedback controller, to make the efforts on the yoke feel the same as the earlier aircraft, especially at higher angles of attack. They still use a stick shaker/pusher when it gets close to a stall as well. One of the stories mentioned the MAX 7 has a version of MCAS as well.

jd, I wondered what else might be going on if they hit the cutoff switch and still could not control the aircraft and then decided to flip it back on. It sounds like they were trying to use the trim switches instead of the manual wheels in a couple of the more in depth reports. If that is the case, there may be some other training issues or a language barrier issue at hand here also.

[flipper35]

Originally Posted by GH85Carrera

The Air Force just stopped accepting the new tankers. The Air Force keeps finding tools and other debris in closed panels. Just completely unacceptable to get a new mega million dollar aircraft and part of a huge order, and have junk left behind by the workers. Not the publicity Boeing needs or wants. Well, maybe they do need it. Fire those production crews and hire some that want to do a good job, or move production to a plant that wants top quality production.

Are those built in WA? They may have a very difficult time firing those employees if so.

[javadog]

Originally Posted by flipper35

Why do they keep calling it anti-stall technology? From my understanding from both pilots and the manufacturer is that this is more like a force feedback controller, to make the efforts on the yoke feel the same as the earlier aircraft, especially at higher angles of attack. They still use a stick shaker/pusher when it gets close to a stall as well. One of the stories mentioned the MAX 7 has a version of MCAS as well.

jd, I wondered what else might be going on if they hit the cutoff switch and still could not control the aircraft and then decided to flip it back on. It sounds like they were trying to use the trim switches instead of the manual wheels in a couple of the more in depth reports. If that is the case, there may be some other training issues or a language barrier issue at hand here also.

The only reason to turn the switches back on would be so they could trim it electrically. At which point you'd think they'd turn it back off. I heard they turned it on and off 4 times but I haven't looked at the FDR traces yet to confirm that.

[flipper35]

I read the same thing, four times. You would think they would leave it off and trim manually like you are supposed to do. A couple reports talked about the engines surging as well and a lot of disparity between instrumentation between the left and right seat. The instrumentation I can understand if the computer thinks they are at high (75* in one report) angle of attack since it would have unreliable data from a pitot tube at that angle but the pitch ladder doesn't make sense. Something really odd here. Hope it isn't bad software beyond the MCAS.

[javadog]

There is some indication that they were unable to trim manually, maybe from excessive aero forces. The prelim report can be seen here:

https://games-cdn.washingtonpost.com/notes/prod/default/documents/6375a995-4d9f-4543-bc1e-12666dfe2869/note/4cb6f748-a0c0-45c2-bf0b-f672ba3cfebe.pdf

It apparently all started with divergent AOA indications after rotation. One vane's data trace went to 75 degrees and stayed there.

Interesting to note the captain was 29 and the FO was 25. FO had a total of 361 hours.

It's clear they knew they had a trim issue and ran the checklist but they did some things that were not recommended. Maybe their decisions were correct, in light of factors that are unknown.

I wonder about the ability to trim the stabilizers in all corners of the flight envelope. I also wonder of they were both cranking on the trim wheels when they were trying to trim manually. It sounds like the Captain was flying and the FO cranking. Not strong enough? Impossible for anyone?

[otto_kretschmer]

I've been following this guy with his 737 max updates

[javadog]

I really don't understand why they didn't simply keep their thumb on the trim buttons until they had a normal stabilizer trim position. And, once they flipped the cutout switches back on, to use the trim switches after they failed to be able to adjust it manually, why the hell didn't they flip the switches back off after they finished their inputs? And why were the inputs so brief that they made almost no difference?

I realize that the left AOA indicator was indicating incorrectly, but the value was not credible so it should have been disregarded as erroneous. The FO should have tried to switch the AP on from his side, instead of the captain turning his on.

Then there's the whole issue of never retarding the throttles and getting up to and past the redline speed.

Things only really went south after the last electrical trim inputs, when thy left the cutout switches in the on position.

[seafeye]

I’m not sure you can just disregard the AOA sensors. All that analog data from all the external sensors are fed into Seperate computers that convert the analog data into digital. Then those are fed into DADC’s. Dual air data computers. That get turned into usable data for the pilots. I can’t speak for the 737. But on the Airbus and other jets I’ve flown you always have the ability to turn off one side of the data. And use the other. I’ve never seen where you can just turn off say an AOA vane. But in reality. It’s difficult to know what is the right info. For example. If the f/o airspeed is reading 180 knots. And the Captain is showing 200. Who’s is right? Sure you can look at the standby. But say that’s at 190. Standby never seems to be accurate. Because of the location of the sensors.
Locking. And unlocking the brakes on the horizontal stab doesn’t sound like a good idea but maybe they were just trying to get the airplane so it an be flown in level flight.

Also the computer has full authority of the horizontal stab when trimming the airplane. The pilots only have a trim tab. Maybe the trim tab ran out of usefulness so they disconnected the stabilizer to try neutralize it, to get more trim control. You have to be Big John to fly a 737 straight and level with the horizontal stabilizer in the wrong position. Both feet on the dash with arms crossed behind the yoke. If it was me I’d probably disconnect the stabilizer brakes and try retrim.

[javadog]

I have to remind myself that maybe they didn't have AOA indicators on both sides of the cockpit. I think that was an option and they may not have ordered it. I think one is standard on the left side.

As I understand it, there are two AOA sensors, each which feeds eventually into the flight computer on their respective sides of the aircraft. As far as MCAS is concerned, only one computer is used per flight and it alternates with each cycle. I think that may have to change.

In any event, if the left sensor starts showing bad date right at rotation, I think any pilot could recognize that he's 15 degrees nose up, not 75.

Towards the end of the flight, they had to know the stabilizer position and when they turned the switches back on, I would have thought they would have kept their trim switches mashed continually, until the stabilizer had a lot more units showing and the column forces weren't so high that they were both pulling back as hard as they could. The two short inputs, that achieved almost no change in the stabilizer position or the aircraft's pitch, then leaving the switches on, I think doomed them.

[flipper35]

It makes no sense to turn the electric trim back on. If the manual trim didn't work there was something else serious happening, or they were overwhelmed and confused. Another thing they could have and probably should have done after everyone reviewed Lion Air is run the flaps to 5* with the throttles back until it is stabilized. That would have taken MCAS out of the picture entirely.

I know, not there, speculation etc.

[daepp]

Originally Posted by flipper35

It makes no sense to turn the electric trim back on. If the manual trim didn't work there was something else serious happening, or they were overwhelmed and confused. Another thing they could have and probably should have done after everyone reviewed Lion Air is run the flaps to 5* with the throttles back until it is stabilized. That would have taken MCAS out of the picture entirely.

I know, not there, speculation etc.

In Otto's video above, the (777 F.O.) pilot indicates that the aerodynamic forces can, at times, be so strong that it may become necessary to use the electric motor to change the trim setting - that the manual wheels would be too stubborn to turn. Perhaps, in the heat of the moment, they attempted to adjust the trim with power assist, so to speak, but lost track and left it energized. Speculation of course on my part...

[flipper35]

Hence the flaps to 5* to use the electric trim.

[flipper35]

They should have pulled the old Denzel and rolled inverted!

[stevej37]

A very realistic movie scene. ^^^
A person can only imagine the chaos that the crew and passengers enter into.

[javadog]

This quote, from another forum, might just sum things up.

“I will preface my response by saying that there is lots of blame to go around and when I criticize the pilots understand that this is also a criticism of their airline employer as well as their national CAA.

In all three MCAS incidents, immediately upon lift-off the aircraft was into an Unreliable Airspeed situation (stick shaker, disparity between the various airspeed indicators). This is a recall (memory) checklist - set an attitude/power setting (10 degrees/85% with flaps, 4 degrees/70% clean - don't quote me on those numbers as I am not MAX qualified), autopilot and auto throttles off, etc. This is a simple emergency procedure.

Neither the Ethiopian nor Lion Air accident aircraft pilots did this checklist. In fact, the Ethiopian Captain asked for the autopilot on, contrary to the checklist. Getting the power back from take-off to 85% or less would have most helpful in controlling the speed and hence the trim forces when manual trim was required later. I think it is fair to ask why four B737 MAX rated pilots did not do a simple, memory checklist and remember, this is along before the flaps went to zero and MCAS kicked in.

When the flaps were selected up and the aircraft was in manual flight the MCAS did its thing, namely provided an uncommanded nose down trim. Anybody hand flying the jet surely could not miss this as the trim was uncommanded, downward and produced a lot of nose down trim; manual electric trim was available including continuous nose up trim to both stop MCAS and return the aircraft to a neutral trim - this is basic flying skills. Nevertheless, neither crew did not do the Stab Trim Runaway procedure which, again, is a simple, memory checklist...manhandle the aircraft and shut off the stab trim cut-off switches. Once again, how is it that the four pilots in these two aircraft did not do a simple recall checklist? Worse, on the Lion Air flight on the same aircraft previously, the operating crew did not know to turn off the stab trim and it took a jump seat pilot from another airline to point this out.

Pilot error is too often the go to explanation for an accident and I don't like it one bit however why did these pilots, all MAX endorsed, not do two simple, memory checklists particularly the Ethiopian crew that should have been acutely aware of this issue following the Lion Air accident.”


I realize that we shouldn’t automatically blame the pilots until the investigation is complete, but I think some mistakes were made here.

I would wager that a Southwest Airlines or American Airlines pilot would not have had this outcome.

[Clint Lando]

computer does everything

[flipper35]

Originally Posted by stevej37

A very realistic movie scene. ^^^
A person can only imagine the chaos that the crew and passengers enter into.

That was actually based on an Alaska Airlines flight crew's attempt to save the plane when the jack screw pushed the elevator full nose down. It didn't work out for them. The movie, of course, took a lot of artistic license.

"Five miles above the Pacific Ocean, alone with a mechanical problem they could not counter or even completely diagnose, the crew of Alaska Airlines Flight 261 seemed to try everything to save their plane, even as it rolled upside down and rocked back and forth in the last moments of flight.

''Got to get it over again -- at least upside down we're flying,'' the captain, Ted Thompson, said. His determined words, 19 seconds before hitting the water off Los Angeles, were captured on the cockpit voice recorder. A transcript was released today by the National Transportation Safety Board as it opened four days of hearings here on the crash."

[David]

Why would the Ethiopian crew keep the throttles near max power? Seems like that would give even less time to solve the problem vs helping pull the nose up.