Cockpit voice recorder of Lion Air jet depicts pilots' frantic search for fix

Post by dmix » Wed, Mar 20, 2019, 6:42 PM UTC

imsofuture wrote: post #232

dmix wrote: post #170

Earlier quoted context omitted.

> That's a problem. That's a TRAINING problem. Isn't the root problem still related to the fact that the AoA sensors were returning wrong information and the MCAS was simply reacting to that in a dangerous and non-obvious way? I guess the pilots should be aware of this type of system reaction but still it seems like something that should be fixed at a higher level than training (indicators, backup AoA sensors, detect…

Those fixes are inarguably lower level than training. Not just to be pedantic but the whole reason Boeing is in this mess is because they figured all the lower level things could sort out issues, without engaging higher level fixes. I'm skeptical of the amount of automation the big manufacturers are pushing. They're creating wildly more complex system interactions in the process.

Post by msbarnett » Wed, Mar 20, 2019, 6:47 PM UTC

achandlerwhite wrote: post #189

petilon wrote: post #185

Earlier quoted context omitted.

So in other words they designed it this way in order to make the 737 MAX is cheaper to operate, and therefore easier to sell. That's terrible. Boeing traded off safety for profits.

Yes cost is a factor. The alternative might not be feasible economically. I don't think the failure here was reusing the 737 design, but the downstream due diligence of implying no significant changes. I also think airline training is a factor--both Boeing for the new systems and the airliners because runaway stabilizer trim has been in the aircraft emergency checklist for over 50 years and every pilot should know it…

Post by jandrese » Wed, Mar 20, 2019, 7:14 PM UTC

foldr wrote: post #230

jandrese wrote: post #219

Earlier quoted context omitted.

I remember right before the impact with the water the captain finally realizing why his controls aren't doing anything and asking the co-pilot to finally let go of his stick. IIRC they never did throttle up however. Ultimately the co-pilot got tunnel vision and thought for some reason they were in an overspeed condition for most of the incident and failed to communicate that effectively with the rest of the crew. He…

The captain wasn't at the controls. I'm not sure what you mean by "throttle up". They were at full TOGA thrust.

  Neither Bonin nor Robert, nor the third crew member (Marc
  Dubois, the captain) who entered the cockpit 90 seconds
  into the episode, recognized that the aircraft had stalled
  despite multiple cues. In the confusion, Bonin 
  misinterpreted the situation as meaning that the plane was 
  flying too fast and actually reduced the thrust and moved 
  to apply the speedbrakes – the opposite of what was 
  required to recover from the stall. Robert overruled him 
  and attempted to take control, but Bonin continued to try 
  and fly the plane. He and Robert made simultaneous and 
  contradictory inputs, without realizing that they were 
  doing so. By the time the crew worked out what was going 
  on, there was insufficient altitude left to recover, and 
  AF447 crashed into the ocean, with the loss of all 228 
  passengers and crew.


  But I've had the stick back the whole time!

  At last, Bonin tells the others the crucial fact whose 
  import he has so grievously failed to understand himself. 

Post by AceyMan » Wed, Mar 20, 2019, 7:30 PM UTC

CyberFonic wrote: post #10

One of the factors that has been quickly glossed over is the low level of experience of some of the pilots in both the Indonesian and Ethopian accidents. In the USA, due to much higher levels of experience pilots have been correcting for the MCAS actions effectively and complaining about it to NASA (in order to avoid being branded as whistle-blowers by their airlines).

Post by fgonzag » Wed, Mar 20, 2019, 7:35 PM UTC

VBprogrammer wrote: post #119

dvdkhlng wrote: post #118

Earlier quoted context omitted.

Yes, thinking about that, not having any pilot-visible indication would be quite some point of failure at lift-off. Still wondering whether MCAS and other automatation systems have a representation of that position indication. I can't currently come up with an idea of how to implement that in an easy, yet error-resilient way. Usually you would initially drive into a reference position, then integrate the motor's acti…

A potentiometer (or something fancier) directly attached to the stabilizer would do it. I'm not sure if they do have one or not. They rate of movement on the stab trim is different depending on the source of the trim change so it's possible they have a PWM controller with some feedback.