Originally Posted by McHale
So I can only assume (and we all know where that can lead to)
Usually the QRH offers some hints at these times (none handy at the moment).
Regarding Antiskid... With no IRU input, if all the wheels on a particular bogey were hyroplaning (i.e. wheel speed zero), would the aircraft see this as the aircraft stopped and keep the brakes applied because the wheelspeed is less than 8kts)?
Regarding Autobrakes, so far I've only looked at the logic for these from one angle: Antiskid problems causing Autobrake problems (My logic diagrams say that if there are any Normal antiskid problems, the Autobrake switch won't arm). Looking at Autobrakes alone....
The IRUs aren't mentioned in the A/B switch (1~MAX) arming logic on the 747-400 (EDIT: Disregard... See correction below), but they are mentioned in the disarming logic. Indeed, during ground tests, the A/B switch won't stay in the latched position with the IRU's off (NB: park brake confirmed off, hydraulics on). I haven't tried this in ATT mode though. One of the inputs to the disable logic is marked "Captain's selected IRS fail". There is no definition of "fail" shown however.
PS... We've gone a bit off topic, but still learning.
Until we know why Pin Head was asking, I think we can indulge ourselves
