Old 14th Mar 2019, 19:11
  #182 (permalink)  
fdr
 
Join Date: Jun 2001
Posts: 508
Originally Posted by canyonblue737 View Post
everything below is about LION AIR:

1. i see no evidence you can't disable MCAS with stab trim cutout. this is the bottom line fix that works even when all else fails. i have yet to see it won't work or didn't work in any of these accidents, it just wasn't tried.
2. i see no evidence that MCAS didn't perform *as designed* in response to an inaccurate indication of a stall based on a flawed AOA sensor. that's a software response to a hardware failure.
3. Boeing has already stated the coming fix to the software will: 1) have MCAS compare both AOA sensors and require them to match prior to any application of trim 2) have a visual alert appear to the pilots showing the MCAS application and 3) disable the ability of MCAS to apply more than a certain amount of total trim, a value which can be overcome by pilots with yoke force. that seems comprehensive in terms of a fix that would have prevented the lion air accident from happening.

i see ZERO reason the MCAS issue wouldn't be resolved by the coming fix even for pilots who don't understand the proper use of the stab trim cutout switches but of course we have to wait and see what the evidence shows with this weeks tradgedy.
the point is that while what you say is correct, the loss of Lion's Max show that the real world is more complex than a simple switch flick, on the day it didn't happen. The crew there were missing information.

Wind forward 5 months, and with the new knowledge and AD etc, we see a likely repeat of the deal in Addis. A simple switch flick didn't happen, or didn't permit recovery in time.

Sitting in a simulator and doing a procedure is slightly different to confronting a sudden life threatening, time critical event even when the cure is known.
fdr is offline