LRRA Fault Detection
Not a pilot (Dad was, now retired) but an RF engineer.
Crew comments aside, I hope the final report provides more focus on the fault detection algorithym used on the LRRA systems and Boeing's requirements for self-fault detection.
Either there was an internal fault with the radio electronics themselves, or a fault developed in the transmission path (antenna & cabling). My understanding is that the RA is calibrated to read zero when on the ground on the gear. If the fault was internal to the electronics, this should have been trivial to code for and detect. Should the fault have delveloped in the 'dumb' portion of the system (cable and antenna) there are easy ways to test and detect that would not interfere with the normal active operation of the system - specifically monitoring VSWR and/or doing TDR tests on the system.
It just seems that a -7 to -8 foot reading could have been more gracefully handled in system design.