737 MAX MCAS activation - in the sim?

[Smooth Airperator]

Is there anyone here who believes they encountered the exact same uncommanded trim problem or something similar in a 737 MAX simulator PRIOR to (or even just after) the crashes of 2018/19?

I believe me and several others did (for an airline assessment).

[ignorantAndroid]

Early on, there was a bug in the simulator which was sometimes mistaken for MCAS. It was mentioned in one of the Boeing chat logs that were released.

Was it an Unreliable Airspeed scenario? Was there an IAS DISAGREE or AOA DISAGREE? What were the flight conditions?

[Smooth Airperator]

No NNs. Started on approach, on the ILS for me, felt like a delayed reaction to trimming. You'd trim, nothing would happen, thus causing you to push/pull on the yoke. Then 5 seconds later the delayed trim input would kick in, adding to your yoke input thus causing wild swings and major control difficulties.

[FlyingStone]

This sounds more like a sim issue than MCAS. Main electric stabilizer trim always overrides any MCAS/STS (Speed Trim System) inputs and should function instantly, even with the original MCAS.

[MechEngr]

A proper MCAS simulation would have two AoA inputs. One is to the aircraft dynamics simulation and a second one to the instrument/flight computer.

I have not heard from any simulator operator how these separate values would be entered into the simulation.

[FlyingStone]

There is an AOA disagree malfunction available in some simulators, which simulates one AoA sensor failing high or low, and is used for unreliable airspeed training on takeoff, as required for 737 MAX differences training.

[RdKetchup]

Originally Posted by FlyingStone

There is an AOA disagree malfunction available in some simulators, which simulates one AoA sensor failing high or low, and is used for unreliable airspeed training on takeoff, as required for 737 MAX differences training.

That malfunction, as delivered by the airplane OEM as part of the Data Package for the MAX only included an AOA low condition before the MAX crashes.

The updated malfunction with options for either AOA low or high was only delivered with the Data Package that also contains the fix to the MCAS software.

So I don't believe it is possible to reproduce the extreme MCAS events using a Full Flight Simulator used for training purpose, at least not using the AOA malfunction.