How many aircraft that we know had an MCAS malfunction are currently not destroyed from a crash? 0.
So far, aircraft with malfunctioning MCAS has resulted in 100% loss of aircraft.
So far, aircraft with malfunctioning MCAS has resulted in 100% loss of aircraft.
At first, everyone asserted it was 'faulty sensor reading,' but later it came out that there's also faulty programming and the MCAS system has way more authority than originally specified to the FAA.
There’s about 40 seconds before the aircraft becomes unrecoverable in these 2 crash scenarios. It’s not pilot error.
It’s design, software, certification subterfuge, lax FAA regulatory posture, and limited pilot awareness and superficial training. Roughly in that order.
Add to that desperation, in that Boeing was keen to catch up with the Airbus 320neo, and didn’t want to build (and certify) an entirely new aircraft.
Plus an extra sensor and related systems most US 737MAX’s have was an option, and at least the Lion Air aircraft didn’t have it.
Demonizing pilots or belittling the training of the LionAir and Ethiopian Air pilots is offensive and not supported by the facts.
This is going to get worse for Boeing. Their only saving grace is that the airlines and military need them too much.
<pilot; not ATP>
When hundreds of lives are at stake, defense in depth is critically important. Planes that crash unless the pilot does the exact right thing in some rarely occurring situation are not safe. It's bad design. That's like saying that airbags aren't necessary in cars because if everyone just drove perfectly there'd be no accidents. Well guess what, no one's perfect, and building systems that require human perfection are bad engineering.
But here's the thing. It's impossible to train or have a checklist for every eventuality or combination of failures. In the end, it's up to the pilots to use good airmanship and fly the plane. If systems are interfering with that, disable them and fly the plane. Trim system doing something you don't want? Disable it and fly the plane. Instruments disagree? Set known good pitch and power and fly the plane. It was daylight in good weather. Look out the window. Fly the plane. Diagnostics can wait until the plane is flying again.
Those two aircraft were flyable. All they needed to do was flip a switch. And fly the plane.
I'm not in any way suggesting that the problems with MCAS or AoA data on the 737 MAX should not be fixed.
I personally find the AoA sensors failure to be unlikely in the case of the Lion Air crash as they were replaced in between the two problematic flights.
I most interested in seeing the final results of the Ethiopian crash. My suspicion is the MCAS has terrible software and is a bug-ridden mess.
If maintenance procedures for testing did not correctly specify that a retest must start, then restart the system to actually test that the repair was successful, then that replacement may have been tested while the computer was being fed data by the correctly operating sensor. They would have had to attempted a single boot between flights for the next flight to have flown with the untested replacement sensor. If they didn't test at all, then it's possible both sensors had a problem.
This is of course assuming that there is any retest procedure at all in the documentation given that the AoA sensor wasn't classified as safety-critical.
It really seems like the makings of a bad movie doesn't it?
That's why it's incumbent upon Boeing to let the pilots know about all of the systems.
Trim system doing something you don't want?
STS generally does this by design.
Disable it and fly the plane
Boeing claims that MCAS is a part of STS. Well, you can disable STS quite easily by pushing/pulling on the yoke. You cannot disable MCAS this way.
Which, notably, they did not run right away. The need to run the runaway trim checklist was pure guesswork on the pilot in the jumpseat's part. It took them several minutes of fighting with the controls before they finally killed the trim. They even re-enabled the auto trim after killing it, not initially recognizing that that was what had fixed the issue.
Not even the flight that survived correctly identified the issue initially. This really isn't a case of "see, these other pilots got it right". They got lucky.