[alexey-salmin]

This sounds odd, they're able to certify the crazy MCAS but not a simple anti-ice switch?

I know that it's a complete nightmare to certify anything. However I apparently don't understand some underlying principle that allows to certify some things and not the others.

[wahern]

The constraint here (entirely self-imposed by Boeing's sales strategy) is that the newer models have to basically behave like the older models to avoid needing a new type certification. (See https://en.wikipedia.org/wiki/Supplemental_type_certificate) The aircraft behavior, and pilot procedures and training have to be substantially similar. That was the whole point of MCAS, to make the plane fly as-if it were an older model, despite the significantly different aerodynamics. Changing anti-icing procedures is apparently too big a difference to maintain the original type certification.

[kayfox]

> That was the whole point of MCAS, to make the plane fly as-if it were an older model, despite the significantly different aerodynamics.

MCAS was implemented to make sure the control forces increase going into a stall, this is a requirement in the regulations. Without MCAS the control forces would drop on the way into a stall, which is an issue that would prevent certification of the aircraft.