This was not what is known as “runaway trim”. The MCAS worked exactly as it was supposed to, with tragic results, because of systems interactions (AOA vane on Captain’s side causing stick shaker and creating the condition causing the MCAS to intervene). MCAS is unique to the 737 Max — it isn’t on the 737 NG, classic, etc., and none of the world’s 737 Max crews have ever known about the existence of MCAS, until now.
If they had left the flaps down this would not have happened (no MCAS with flaps extended) as seen during the seconds following the initial stick shaker. But that’s a systems insight unknown to them since Boeing never told the operators about the existence of MCAS or its systems characteristics.
Additionally, the crew was likely confused by the intermittent nature of the (MCAS-induced) nose down trim — every time either pilot used nose-up yoke trim to counteract the nose-down trim, the MCAS cut out for about 5 seconds, then resumed nose-down for up to 10 seconds (or until interrupted by nose-up yoke trim again). This happened over a dozen times as the Captain flew the airplane, suppressing the symptoms of MCAS intervention, making the down-trimming actions insidious, probably until he handed over the controls to the first officer (who unfortunately didn’t interrupt the MCAS with opposite trim in a timely manner, resulting in further nose-down trim to the point of no return).
If the crew had activated the stab trim cutout switch it would have precluded MCAS activation — but until the flaps came up all they had was a stick shaker induced by the defective AOA vane, not MCAS activation, so their mindset was not focused on the trim at the time. Apparently the previous crew never experienced MCAS trim activation (perhaps the flaps were left extended).
This was an experienced crew with 6,000/5,000 hours for the Captain/First Officer, respectively. Perhaps if they had been better trained they would have tried using the Stab Trim Cutout switch, but like the crew of Air France 447, tragically the best remedy just wasn’t apparent to them given the sequence of events and the confusion.
Boeing is indeed culpable to a large degree, as we will see. They never told crews (or the airlines) about MCAS. There was no training at any airline associated with MCAS. They didn’t think it was important enough (and it’s worth noting: airlines want to keep training as short as possible since training costs money, requires instructor/simulator time, and means down time for crews vs. flying revenue trips). There will be consequences for Boeing.
Good report. It’ll be interesting what the NTSB comes out with after the boxes are found. The NTSB works in cooperation with other nation’s flight accident investigators.
Can that possibly be true? That doesn't sound remotely possible. How can a major new system affecting control be secretly installed and no airlines told about it or trained on it?
I'm ignorant on these things, but that just defies common sense.
If you don’t know your airplane, it will kill you. It is as simple as that.
Not including the existence of the MCAS system is CRIMINAL!
Not training crews in the MCAS and how it operates is CRIMINAL.
Boeing and the airline, probably the pilot union, as well as the national “FAA” are guilty of murder.
This is just unforgivable.
PS. The Boeings that I have flown are the B-52, 727, 737, 747-400, 757, 767, and 777.
No link?