I'm writing this for Aviation Week and would like to understand the 737-700 retarding systems.
Would like to clarify:
1) For autobrakes, is wheel spinup (means >60 kt.?) required? Is there an air-ground sensor backup if wheels don't spinup on icy runway, like the autospoilers have?
2) What does it take for the manual brakes and/or antiskid to work? If the wheels haven't spun up to >60 kt., does pressing the brake pedal actually clamp the brakes, or does it do nothing?
Is there an on-ground (squat switch) indication required for the brakes to work?
Is there any difference between the brakes working, and the antiskid working? That is, can the brakes clamp but the antiskid is not yet alive, perhaps because wheel spinup hasn't been sensed?
3) The sensors for weight-on-wheels in the autospoiler logic is curious -- the description provided by Mr. Rafferty suggests 3 separate things: a) air/ground sensor, b) any landing gear compression, and c) R MLG compression.
Are those really 3 different things?
What does it take for the air/ground logic to think it's on the ground?
Thanks,
-- Mike Dornheim