Originally Posted by
Artisan
The B737stab trim system has two speed modes for the autopilot and main electric trim, I.e. high rate trimming with flap extended and low rate trimming with flap up.
I am wondering if the MCAS was programmed to always input high rate trimming? Hence if you are flying a MAX with flap up and the MCAS puts in a high rate AND burst for 10sec, then the pilots available ANU counter response on the main electric trim will only be at the low rate.
Looking at the FDR trace, the longest application of ANU trim (about 9-10 seconds) appears to have moved the stab about two units. That's almost, but not quite, the rate that MCAS had been moving it in the opposite direction.