The Anti-skid/Autobrake Control Unit (AACU) arms RTO braking when all wheels speed average more than 90 kt as per FCOM (88 kt according to AMM).
Air/Ground sensor does not sense any speed, air/ground sensor either senses air or ground.
So its based on ground speed and not IAS?
So, if you have a HW of 20kts at 90KTS that will make your ground speed 70kts and your autobr won’t initiate
Yes, since the AACU senses the wheel speed it is indeed the ground speed (not IAS)
But what if you loose IRS and you have no GS available
AACU senses the wheel speed by using the wheels tachometers
RTO function applies brake pressure when all wheel speed Average is more than 88KTS, throttles at IDLE, and there are no fault in the antiskid system.
For this function ADIRU GS is not part of the game.