Hello folks, I always notice and can't figure out why arming autobrakes for RTO is only possible with idle or near to idle thrust. Even when applying normal breakaway thrust autobrake won't arm anymore. What I mean by that is, the DISARM light won't go out. And it's definately not dependent on thrust, only thrust lever angle. Pulling them back a tiny bit, and zap, autobrakes arm. Place to OFF, add a tiny bit of thrust, select RTO, bam, don't arm. Could play this game all day although I don't get it.I understand autobrakes will disarm after landing when advancing thrust levers, but why would they do so when trying to arm RTO?

Hello folks, I always notice and can't figure out why arming autobrakes for RTO is only possible with idle or near to idle thrust. Even when applying normal breakaway thrust autobrake won't arm anymore. What I mean by that is, the DISARM light won't go out. And it's definately not dependent on thrust, only thrust lever angle. Pulling them back a tiny bit, and zap, autobrakes arm. Place to OFF, add a tiny bit of thrust, select RTO, bam, don't arm. Could play this game all day although I don't get it.I understand autobrakes will disarm after landing when advancing thrust levers, but why would they do so when trying to arm RTO?

RTO should be selected during your pre-flight setup, prior to departure. To arm the autobrake the following conditions must exist:

• airplane on the ground
• antiskid and autobrake systems operational
• AUTO BRAKE select switch positioned to RTO
• wheel speed less than 60 knots
• forward thrust levers positioned to idle

Cheers, Doug

And again, checked the wrong manual... Thanks, must have missed it. Two thrust levers at idle, there we have it.

Also !! See FCOM Vol 2 page 1186........." Autobrake Disarm Light " Fred.

Thanks, I read that before. But it doesn't say anything regarding my issue. The point was why it wouldn't arm with thrust levers advanced. Now I actually still don't have a reason as to why this is, but at least I have confirmation the conditions are just like that, and idle thrust is required to arm them, for whatever reason.

Thanks, I read that before. But it doesn't say anything regarding my issue. The point was why it wouldn't arm with thrust levers advanced. Now I actually still don't have a reason as to why this is, but at least I have confirmation the conditions are just like that, and idle thrust is required to arm them, for whatever reason.

As my old instructor would have said "It just does, okay!"

LOL I hear ya