View Full Version : B737NG Antiskid/Autobrakes

29th Feb 2008, 12:02
I understand that with Antiskid inop, you lose autobrake... but if you lose autobrake, do you lose the antiskid function.

My thoughts are....in RTO without autobrake, it would be handy to still have antiskid combined with max manual braking...

DDG, QRH, Vol 2 haven't seemed to point me in the right direction.


29th Feb 2008, 12:18
Here's my tuppence. They are two different systems. For max autobrake operation you need antiskid to prevent wheel lock. So the autobrake system requires antiskid operational. And as you suggest, antiskid is more than desirable in RTO with max manual braking effort. Hence the huge penalty on RTOW with antiskid inop (7,800 tons RYR policy), as far as I remember it's not even allowed on a wet rwy.

Totally Lost
29th Feb 2008, 12:21

14.20.4 of the OM2 states that antiskid protection is available even with loss of both hydraulic systems. Autobrake uses system B and the normal brakesytem must be available. Antiskid is available with normal or alternate brakes, so if autobrake capabilities are lost, antiskid still works.
Hope that helps...


Totally Lost

sudden Winds
29th Feb 2008, 19:39
Totally lost is totally right. If u lose autobrake, say during taxi, u do the checklist, turn it off, light goes out, check the MEL and go. I dont know if u need it for cat II/III landings but if thatīs not the case, there arenīt any problems. Be ready on those brakes if u see a cow in your way during takeoff roll and thatīs it. Antiskid functions just fine.
Hope it helps,

1st Mar 2008, 01:37
Thanks for the responses.. very appreciated.

I may have sorted it out... my main concern was that in the RTO situation, why isn't there a penalty along the theme with Thrust Reverser inop, antiskid inop etc etc...
I think the acft are certified without the use of autobrake ie max manual braking, no Thrust Reversers etc in the RTO certification process.....

I'm just going now to look it all up, but if anyone could throw some info this way.. that'd be great..

thanks for the good discussion

mona lot
19th Nov 2008, 23:06
Is this correct, does the TO performance assume that the autobrake is inop. for V1/RTO calculations? Why is this not stated explicitly in the performance preamble? Why is there not a performance penalty?

20th Nov 2008, 07:13
It is explicitly stated in the FCTM Takeoff section:
During certification, maximum manual braking and speedbrakes are used. Thrust reversers are not used. Although reverse thrust and autobrakes are not used in determining the FAR accelerate-stop distance, thrust reversers and RTO autobrakes should be used during any operational rejected takeoff.

So autobrake is not "assumed to be inop", it's just not part of certification. But Boeing (and most likely your operator) recommend you let the Autobrake do its job.