Originally Posted by
Someone Somewhere
I'm slightly confused; if BTV CONTAM doesn't take into account the distance to the selected exit, how is it any different to standard autobrake?
The rest fits pretty well with what I surmised.
BTV CONTAM applies the brakes immediately, slows the aircraft to 10 knots, then releases the brakes. The basic auto brake mode (BRK MED) decelerates the aircraft at the same rate as BTV CONTAM (0.3 g), but it does not release the brakes at 10 knots and does not increase the braking to 0.35 g (subject to anti skid) in a missed exit scenario.
I previously said that braking occurs after nose wheel touchdown, but that's not quite right. The BTV or BTV CONTAM mode engages immediately after ground spoilers extension if the nose wheel is on the ground, or 5 sec after ground spoilers extension if the nose wheel is
not on the ground. In BTV mode, brake application may be delayed, as previously described.