Jul 29, 2020

120kts IAS RTO You have a 30kts HW and this will make your GS 90kts. Is the air / ground sensor based on 1. ground speed 2. IAS


Hi Vernon, 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.


Jul 29, 2020

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)

Jul 29, 2020

But what if you loose IRS and you have no GS available

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Aug 6, 2020

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.