The flap position monitoring is a function of the Flap Slate Electronic Unit, so my guess is that the FSEU would send a signal to MCAS (which is a subroutine of the FCC) regarding flap position. There are one or more digital data busses which allow the various electronic components to exchange information, so I figure this would be the easier option than running a dedicated sensor to the flap handle. Reference the DFDR data from ET302 mentioned in the post immediately prior, there could be some threshold value beyond which the flaps are presumed up (i.e. < 0.2 degrees, slats retracted, etc.).
Last edited by 737 Driver; 20th Apr 2019 at 20:50.
Reason: Added comment