The Airbus autopilot can come on 5 seconds after liftoff or 100 feet AGL!! Oh, and no runaway trim problems!! 😜😜

 

I don't fly 73s, but I'd really appreciate clarification on the following:
-I thought the pitch trim cutouts wouldn't work with an MCAS, so it'd trim you full nose down after a few activations and the trim runaway memory items wouldn't solve the problem,
-I also thought the quick disconnect didn't work on the MCAS and both captains had hammered that button to no effect,
-I also thought if you trimmed it the other way, it would stop the aircraft from trimming more nose down, but wouldn't allow you to trim up, so after a couple of MCAS activations, there just wasn't enough control authority in the elevator to save the aircraft

Also, with MCAS, do you see the trim wheel on the center console spinning? Or is it bypassing it and just running the jackscrew in the tail? If it is spinning, can you jam it, stomp on it, or even spin it in the opposite direction? Or would that be like fighting a 1000 ft-lb impact driver?

I'm not trying to start anything, just genuinely curious.

 

The problem with the MCAS crashes was poor technique and late recognition from the pilot perspective. In the second crash, the crew actually hit the stab trim cutout switches. The problem was, the nose down forces were so great, they couldn't manually crank the trim. You actually have to unload the stab to be able to crank the trim wheel. This requires a kind a porpoising. And even then, it takes something like 40-50 turns to get it back to something manageable.

The second crew couldn't turn the trim wheel and the airplane was on the the verge of out of control. So they turned the electric trim back on.

To your last questions: yes it spins. Yes you can use trim to temporarily cut out the MCAS and yes you could theoretically grasp the wheel. Not sure how effective that would be but it is in the memory item. Why I think it takes so long to recognize is, the 737 actually has a system that trims the aircraft for you on departure so it's actually common to have that wheel spinning on its own as you are pulling flaps up and accelerating.

 

To second CBreezy:

In a worst case MCAS failure event, the manual trim forces that require a "porpoise-ing"/oscillating flight path are highly non-intuitive to the average commercial level trained pilot (who operate in very specific and narrow flight path boundaries), and is a team effort. Not to mention terrifying to the passengers in the back.

Really have to experience in the simulator to appreciate it.

"Flick the auto-trim off and hand crank it" doesn't really do it justice.

 

How much different is an “AB” from a modern FBW Boeing? Answer…Not that much.

 

1. Yes, the pitch trim cutout switches disable MCAS. If you follow the Pitch Trim runaway checklist memory items you would not be in a full nose down condition. Neither crew ran the checklist or the memory items properly.'
2. It is not a button, it is 2 switches next to each other. Now the main electric trim switch overrides MCAS and let you trim the stab, once you release it, MCAS would run again it the system was malfunctioning. The CA in Lion Air kept trimming over and over again and was flying fine. When he transferred control to the FO the FO never trimmed. In the Ethiopian crash neither used the trim switch for more than a few seconds.
3. No, You can trim all you want. I think you are talking about the control column cutouts which is a completely different system. Keeps you from trimming un the opposite direction you are pulling, now those switches (witch are technically force sensors)would not disable MCAS because MCAS was used to keep control forces constant when entering high AOA or accelerated stalls. So it need to work when you were pulling back to stall.

Yes it always spins when the stab is moving regardless of what system is trimming it. Yes you can grab it and hold it. That is part of the Stab Runaway checklist. You can also manually trim it, unless you are going 70 knots beyond the design limit of the aircraft.

 

To clarify, you can manually trim it but if you are greatly out of trim and see using great effort to hold the control column, you will not be able to move the trim wheel manually

 

This is 100% correct.

 

Yes. We practiced this in the sim -- after a 20 minute brief including a powerpoint showing the position of the jackscrew relative to the stab axis and the forces from the elevator. There is no way we could have figured this out in 10s.

 

True, disconnecting auto-throttles if engaged and reducing the thrust below 94% would reduce speed and resultant force needed to trim. These poor folks were well beyond that when they tried to manually trim.
If the sim is like the aircraft, trimming at the UP bug wasn't that horrible. Training. Lots of fault to go around IMHO.